Datasets:

---

memray

/

inspec

like 0

train_908

Multivariable H/sub infinity // mu feedback control design for high-precision

wafer stage motion Conventional PID-like SISO controllers are still the most common in industry, but with performance requirements becoming tighter there is a growing need for advanced controllers. For the positioning devices in IC-manufacturing, plant interaction is a major performance-limiting factor. MIMO control can be invoked to tackle this problem. A practically feasible procedure is presented to design MIMO feedback controllers for electromechanical positioning devices, using H/sub infinity // mu techniques. Weighting filters are proposed to straightforwardly and effectively impose performance and uncertainty specifications. Experiments show that MIMO control can considerably improve upon the performance with multiloop SISO control. Some problems are highlighted that are important for industrial practice, but lacking a workable solution

feedback;weighting filters;servo systems;mimo systems;mechatronics;model uncertainty;motion control;ic manufacture;h/sub infinity / control;mu synthesis;multivariable control systems

train_909

Influence of the process design on the control strategy: application in

electropneumatic field This article proposes an example of electropneumatic system where the architecture of the process is modified with respect to both the specifications for position and velocity tracking and a criterion concerning the energy consumption. Experimental results are compared and analyzed using an industrial bench test. For this, a complete model of the system is presented, and two kinds of nonlinear control laws are developed, a monovariable and multivariable type based on the flatness theory

positioning systems;monovariable control;energy consumption;flatness theory;electropneumatic systems;position control;tracking;multivariable control;nonlinear control;velocity control

train_91

IT challenge: cross selling [finance]

Like most financial institutions, FleetBoston, Fidelity and Berkshire Group of Companies are being charged with developing a strong technology platform that will allow them to cross sell their products and services. They discuss their solutions, advice and technology choices

berkshire group;financial institutions;fidelity;fleetboston;cross selling

train_910

Control of a heavy-duty robotic excavator using time delay control with

integral sliding surface The control of a robotic excavator is difficult from the standpoint of the following problems: parameter variations in mechanical structures, various nonlinearities in hydraulic actuators and disturbance due to the contact with the ground. In addition, the more the size of robotic excavators increases, the more the length and mass of the excavator links; the more the parameters of a heavy-duty excavator vary. A time-delay control with switching action (TDCSA) using an integral sliding surface is proposed in this paper for the control of a 21-ton robotic excavator. Through analysis and experiments, we show that using an integral sliding surface for the switching action of TDCSA is better than using a PD-type sliding surface. The proposed controller is applied to straight-line motions of a 21-ton robotic excavator with a speed level at which skillful operators work. Experiments, which were designed for surfaces with various inclinations and over broad ranges of joint motions, show that the proposed controller exhibits good performance

trajectory control;integral sliding surface;tracking;time-delay control;pressure control;dynamics;motion control;robust control;robotic excavator

train_911

Scheduling schemes for an integrated flight and propulsion control system

We describe two schemes for scheduling an integrated flight and propulsion control system for an experimental vertical/short take-off and landing (V/STOL) aircraft concept in the acceleration from hover (0-120 kn) flight phase. Multivariable integrated flight and propulsion controllers are designed at several points over the V/STOL envelope and implemented as exact plant observers with state feedback. In the first scheduling scheme, the values of the state feedback and observer gain matrices are interpolated between the fixed-point designs as a function of aircraft speed. In the second approach, the control signals produced by the different fixed-point controllers are blended, allowing a significant reduction in the order of the scheduled controllers. Both scheduling schemes are shown in nonlinear simulation to provide excellent handling qualities as the aircraft accelerates from the hover

vertical short take-off landing aircraft;state feedback;observers;vstol aircraft;propulsion control;scheduling;fixed-point controllers;flight control;multivariable control systems

train_912

Grey-box model identification via evolutionary computing

This paper presents an evolutionary grey-box model identification methodology that makes the best use of a priori knowledge on a clear-box model with a global structural representation of the physical system under study, whilst incorporating accurate blackbox models for immeasurable and local nonlinearities of a practical system. The evolutionary technique is applied to building dominant structural identification with local parametric tuning without the need of a differentiable performance index in the presence of noisy data. It is shown that the evolutionary technique provides an excellent fitting performance and is capable of accommodating multiple objectives such as to examine the relationships between model complexity and fitting accuracy during the model building process. Validation results show that the proposed method offers robust, uncluttered and accurate models for two practical systems. It is expected that this type of grey-box models will accommodate many practical engineering systems for a better modelling accuracy

nonlinear system;grey-box models;system identification;genetic evolution;multiobjective optimisation;hydraulic system;evolutionary algorithms

train_913

Control of a coupled map lattice model for vortex shedding in the wake of a

cylinder The flow behind a vibrating flexible cable at low Reynolds numbers can exhibit complex wake structures such as lace-like patterns, vortex dislocations and frequency cells. These structures have been observed in experiments and numerical simulations, and are predicted by a previously developed low-order coupled map lattice (CML). The discrete (in time and space) CML models consist of a series of diffusively coupled circle map oscillators along the cable span. Motivated by a desire to modify the complex wake patterns behind flexible vibrating cables, we have studied the addition of control terms into the highly efficient CML models and explored the resulting dynamics. Proportional, adaptive proportional and discontinuous non-linear (DNL) control methods were used to derive the control laws. The first method employed occasional proportional feedback. The adaptive method used spatio-temporal feedback control. The DNL method used a discontinuous feedback linearization procedure, and the controller was designed for the resulting linearized system using eigenvalue assignment. These techniques were applied to a modeled vortex dislocation structure in the wake of a vibrating cable in uniform freestream flow. Parallel shedding patterns were achieved for a range of forcing frequency-forcing amplitude combinations studied to validate the control theory. The adaptive proportional and DNL methods were found to be more effective than the proportional control method due to the incorporation of a spatially varying feedback gain across the cylinder span. The DNL method was found to be the most efficient controller of the low-order CML model. The required control level across the cable span was correlated to the 1/1 lock-on behavior of the temporal circle map

cylinder;spatio-temporal feedback control;1/1 lock-on;vibrating flexible cable;temporal circle map;vortex shedding;vortex dislocations;vortex dislocation;coupled circle map oscillators;low reynolds numbers;proportional feedback;wake;discontinuous nonlinear control;coupled map lattice

train_914

A knowledge management framework for the support of decision making in

humanitarian assistance/disaster relief The major challenge in current humanitarian assistance/disaster relief (HA/DR) efforts is that diverse information and knowledge are widely distributed and owned by different organizations. These resources are not efficiently organized and utilized during HA/DR operations. We present a knowledge management framework that integrates multiple information technologies to collect, analyze, and manage information and knowledge for supporting decision making in HA/DR. The framework will help identify the information needs, be aware of a disaster situation, and provide decision-makers with useful relief recommendations based on past experience. A comprehensive, consistent and authoritative knowledge base within the framework will facilitate knowledge sharing and reuse. This framework can also be applied to other similar real-time decision-making environments, such as crisis management and emergency medical assistance

crisis management;organizations;real-time decision-making environments;knowledge reuse;knowledge management framework;information technology;emergency medical assistance;disaster relief;knowledge sharing;decision support system;humanitarian assistance;case-based reasoning;information needs

train_915

A meteorological fuzzy expert system incorporating subjective user input

We present a fuzzy expert system, MEDEX, for forecasting gale-force winds in the Mediterranean basin. The most successful local wind forecasting in this region is achieved by an expert human forecaster with access to numerical weather prediction products. That forecaster's knowledge is expressed as a set of 'rules-of-thumb'. Fuzzy set methodologies have proved well suited for encoding the forecaster's knowledge, and for accommodating the uncertainty inherent in the specification of rules, as well as in subjective and objective input. MEDEX uses fuzzy set theory in two ways: as a fuzzy rule base in the expert system, and for fuzzy pattern matching to select dominant wind circulation patterns as one input to the expert system. The system was developed, tuned, and verified over a two-year period, during which the weather conditions from 539 days were individually analyzed. Evaluations of MEDEX performance for both the onset and cessation of winter and summer winds are presented, and demonstrate that MEDEX has forecasting skill competitive with the US Navy's regional forecasting center in Rota, Spain

uncertainty;rules-of-thumb;fuzzy set theory;fuzzy pattern matching;mediterranean basin;meteorological fuzzy expert system;numerical weather prediction products;subjective user input;fuzzy rule base;medex;wind circulation patterns;gale-force wind forecasting;subjective variables;rule specification

train_916

Attribute generation based on association rules

A decision tree is considered to be appropriate (1) if the tree can classify the unseen data accurately, and (2) if the size of the tree is small. One of the approaches to induce such a good decision tree is to add new attributes and their values to enhance the expressiveness of the training data at the data pre-processing stage. There are many existing methods for attribute extraction and construction, but constructing new attributes is still an art. These methods are very time consuming, and some of them need a priori knowledge of the data domain. They are not suitable for data mining dealing with large volumes of data. We propose a novel approach that the knowledge on attributes relevant to the class is extracted as association rules from the training data. The new attributes and the values are generated from the association rules among the originally given attributes. We elaborate on the method and investigate its feature. The effectiveness of our approach is demonstrated through some experiments

attribute extraction;data mining;decision tree;training data;association rules;large database;experiments;attribute generation

train_917

Efficient transitive closure reasoning in a combined class/part/containment

hierarchy Class hierarchies form the backbone of many implemented knowledge representation and reasoning systems. They are used for inheritance, classification and transitive closure reasoning. Part hierarchies are also important in artificial intelligence. Other hierarchies, e.g. containment hierarchies, have received less attention in artificial intelligence. This paper presents an architecture and an implementation of a hierarchy reasoner that integrates a class hierarchy, a part hierarchy, and a containment hierarchy into one structure. In order to make an implemented reasoner useful, it needs to operate at least at speeds comparable to human reasoning. As real-world hierarchies are always large, special techniques need to be used to achieve this. We have developed a set of parallel algorithms and a data representation called maximally reduced tree cover for that purpose. The maximally reduced tree cover is an improvement of a materialized transitive closure representation which has appeared in the literature. Our experiments with a medical vocabulary show that transitive closure reasoning for combined class/part/containment hierarchies in near constant time is possible for a fixed hardware configuration

parallel reasoning;inheritance;containment hierarchy;classification;parallel algorithms;data representation;medical vocabulary;class hierarchy;artificial intelligence;materialized transitive closure representation;part hierarchy;maximally reduced tree cover;knowledge representation;fixed hardware configuration;part hierarchies;experiments;transitive closure reasoning

train_918

Schema evolution in data warehouses

We address the issues related to the evolution and maintenance of data warehousing systems, when underlying data sources change their schema capabilities. These changes can invalidate views at the data warehousing system. We present an approach for dynamically adapting views according to schema changes arising on source relations. This type of maintenance concerns both the schema and the data of the data warehouse. The main issue is to avoid the view recomputation from scratch especially when views are defined from multiple sources. The data of the data warehouse is used primarily in organizational decision-making and may be strategic. Therefore, the schema of the data warehouse can evolve for modeling new requirements resulting from analysis or data-mining processing. Our approach provides means to support schema evolution of the data warehouse independently of the data sources

system maintenance;structural view maintenance;containment;schema evolution;source relations;view adaptation;data analysis;sql query;data sources;data warehouses;organizational decision-making

train_919

Agents in e-commerce: state of the art

This paper surveys the state of the art of agent-mediated electronic commerce (e-commerce), especially in business-to-consumer (B2C) e-commerce and business-to-business (B2B) e-commerce. From the consumer buying behaviour perspective, the roles of agents in B2C e-commerce are: product brokering, merchant brokering, and negotiation. The applications of agents in B2B e-commerce are mainly in supply chain management. Mobile agents, evolutionary agents, and data-mining agents are some special techniques which can be applied in agent-mediated e-commerce. In addition, some technologies for implementation are briefly reviewed. Finally, we conclude this paper by discussions on the future directions of agent-mediated e-commerce

supply chain management;state of the art;data-mining agents;multi-agent systems;agent-mediated electronic commerce;mobile agents;evolutionary agents;business-to-business e-commerce;consumer buying behaviour;negotiation;product brokering;merchant brokering;business-to-consumer e-commerce

train_92

Wireless-retail financial services: adoption can't justify the cost

Slow adoption by retail investors, costly services and bankrupt vendors has prompted banks and brokerage firms to turn off their wireless applications

wireless applications;banks;brokerage firms

train_920

Three-dimensional periodic Voronoi grain models and micromechanical

FE-simulations of a two-phase steel A three-dimensional model is proposed for modeling of microstructures. The model is based on the finite element method with periodic boundary conditions. The Voronoi algorithm is used to generate the geometrical model, which has a periodic grain structure that follows the original boundaries of the Voronoi cells. As an application, the model is used to model a two-phase ferrite/pearlite steel. It is shown that periodic cells with only five grains generate representative stress-strain curves

two-phase steel;kinematic constraints;voronoi algorithm;periodic voronoi grain models;adaptive mesh generator;voronoi tessellation;microstructures modeling;micromechanical fem simulations;ferrite-pearlite steel;stress-strain curves;quadtree/octree-based algorithm;computational time;geometrical model;periodic boundary conditions;three-dimensional model

train_921

Processing of complexly shaped multiply connected domains in finite element

mesh generation Large number of finite element models in modern materials science and engineering is defined on complexly shaped domains, quite often multiply connected. Generation of quality finite element meshes on such domains, especially in cases when the mesh must be 100% quadrilateral, is highly problematic. This paper describes mathematical fundamentals and practical -implementation of a powerful method and algorithm allowing transformation of multiply connected domains of arbitrary geometrical complexity into a set of simple domains; the latter can then be processed by broadly available finite element mesh generators. The developed method was applied to a number of complex geometries, including those arising in analysis of parasitic inductances and capacitances in printed circuit boards. The quality of practical results produced by the method and its programming implementation provide evidence that the algorithm can be applied to other finite element models with various physical backgrounds

metal forming processes;automatic step calculation;quadrilateral mesh;parasitic capacitances;iterative basis;printed circuit boards;parasitic inductances;programming implementation;finite element mesh generation;complexly shaped multiply connected domains;structural engineering models;general domain subdivision algorithm;artificial cut;arbitrary geometrical complexity;set of simple domains;domains transformation;finite element models

train_922

Smart collision information processing sensors for fast moving objects

In this technical note we survey the area of smart collision information processing sensors. We review the existing technologies to detect collision or overlap between fast moving physical objects or objects in virtual environments, physical environments or a combination of physical and virtual objects. We report developments in the collision detection of fast moving objects at discrete time steps such as two consecutive time frames, as well as continuous time intervals such as in an interframe collision detection system. Our discussion of computational techniques in this paper is limited to convex objects. Techniques exist however to efficiently decompose non-convex objects into convex objects. We also discuss the tracking technologies for objects from the standpoint of collision detection or avoidance

nonconvex objects;air traffic control;continuous time intervals;collision information processing;physical environments;consecutive time frames;high speed machining;tracking;virtual environments;interframe collision detection;collision detection;convex objects;smart sensors;discrete time steps;fast moving objects;military training

train_923

Design and manufacture of a lightweight piezo-composite curved actuator

In this paper we are concerned with the design, manufacture and performance test of a lightweight piezo-composite curved actuator (called LIPCA) using a top carbon fiber composite layer with near-zero coefficient of thermal expansion (CTE), a middle PZT ceramic wafer, and a bottom glass/epoxy layer with a high CTE. The main point of the design for LIPCA is to replace the heavy metal layers of THUNDER TM by lightweight fiber reinforced plastic layers without losing the capabilities for generating high force and large displacement. It is possible to save up to about 40% of the weight if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use an epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a carbon prepreg were simply stacked and cured at an elevated temperature (177 degrees C) after following an autoclave bagging process. We found that the manufactured composite laminate device had a sufficient curvature after being detached from a flat mould. An analysis method using the classical lamination theory is presented to predict the curvature of LIPCA after curing at an elevated temperature. The predicted curvatures are in quite good agreement with the experimental values. In order to investigate the merits of LIPCA, performance tests of both LIPCA and THUNDER TM have been conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDER TM

carbon fiber composite layer;glass/epoxy layer;predicted curvatures;lipca;boundary conditions;performance tests;thunder;fiber reinforced plastic layers;near-zero coefficient of thermal expansion;performance test;lightweight piezo-composite curved actuator;177 degc;pzt ceramic wafer;177 degrees c

train_924

Dynamic testing of inflatable structures using smart materials

In this paper we present experimental investigations of the vibration testing of an inflated, thin-film torus using smart materials. Lightweight, inflatable structures are very attractive in satellite applications. However, the lightweight, flexible and highly damped nature of inflated structures poses difficulties in ground vibration testing. In this study, we show that polyvinylidene fluoride (PVDF) patches and recently developed macro-fiber composite actuators may be used as sensors and actuators in identifying modal parameters. Both smart materials can be integrated unobtrusively into the skin of a torus or space device forming an attractive testing arrangement. The addition of actuators and PVDF sensors to the torus does not significantly interfere with the suspension modes of a free-free boundary condition, and can be considered an integral part of the inflated structure. The results indicate the potential of using smart materials to measure and control the dynamic response of inflated structures

satellite applications;thin-film torus;inflated structures;polyvinylidene fluoride patches;boundary condition;dynamic response;pvdf sensors;modal parameters;kapton torus;smart materials;space device;ground vibration testing;macro-fiber composite actuators

train_925

A fundamental investigation into large strain recovery of one-way shape memory alloy wires embedded in flexible polyurethanes

Shape memory alloys (SMAs) are being embedded in or externally attached to smart structures because of the large amount of actuation deformation and force that these materials are capable of producing when they are heated. Previous investigations have focused primarily on using single or opposing SMA wires exhibiting the two-way shape memory effect (SME) because of the simplicity with which the repeatable actuation behavior of the structure can be predicted. This repeatable actuation behavior is achieved at the expense of reduced levels of recoverable deformation. Alternatively, many potential smart structure applications will employ multiple SMA wires exhibiting a permanent one-way SME to simplify fabrication and increase the recoverable strains in the structure. To employ the one-way wires, it is necessary to investigate how they affect the recovery of large strains when they are embedded in a structure. In this investigation, the large strain recovery of a one-way SMA wire embedded in a flexible polyurethane is characterized using the novel deformation measurement technique known as digital image correlation. These results are compared with a simple actuation model and a three-dimensional finite element analysis of the structure using the Brinson model for describing the thermomechanical behavior of the SMA. Results indicate that the level of actuation strain in the structure is substantially reduced by the inelastic behavior of the one-way SMA wires, and there are significant differences between the deformations of the matrix material adjacent to the SMA wires and in the region surrounding it. The transformation behavior of the SMA wires was also determined to be volume preserving, which had a significant effect on the transverse strain fields

three-dimensional finite element analysis;flexible polyurethanes;embedded sensor;alloy wires;actuation deformation;actuation strain;recoverable strains;smart structures;deformations;strain recovery;transverse strain fields;sma wires;two-way shape memory effect;flexible polyurethane;one-way shape memory;matrix material

train_926

Experimental investigation of active vibration control using neural networks

and piezoelectric actuators The use of neural networks for identification and control of smart structures is investigated experimentally. Piezoelectric actuators are employed to suppress the vibrations of a cantilevered plate subject to impulse, sine wave and band-limited white noise disturbances. The neural networks used are multilayer perceptrons trained with error backpropagation. Validation studies show that the identifier predicts the system dynamics accurately. The controller is trained adaptively with the help of the neural identifier. Experimental results demonstrate excellent closed-loop performance and robustness of the neurocontroller

piezoelectric actuators;multilayer perceptrons;identification;robustness;error backpropagation;smart structures;cantilevered plate;closed-loop performance;neural networks;white noise disturbances;control;vibration suppression;neurocontroller;active vibration control

train_927

Autonomous detection of crack initiation using surface-mounted piezotransducers

In this paper we report on the application of an in situ health monitoring system, comprising an array of piezoceramic wafer elements, to the detection of fatigue degradation in metallic specimens exposed to cyclic loading. Lamb waves, transmitted through a beam test coupon, are sensed using small surface-mounted piezotransducer elements, and the signals are then autonomously analysed for indications relating to the onset of structural degradation. The experimental results confirm the efficacy of the approach and provide a demonstration of good robustness under realistic loading conditions, emphasizing the great potential for developing an automated in situ structural health monitoring system for application to fatigue-prone operational structures, such as aircraft

loading conditions;aircraft;robustness;metallic specimens;in situ health monitoring;piezoceramic wafer elements;cyclic loading;lamb waves;automated in situ structural health monitoring;fatigue operational structures;structural degradation;fatigue degradation;surface-mounted piezotransducer elements

train_928

Weighted energy linear quadratic regulator vibration control of piezoelectric

composite plates In this paper on finite element linear quadratic regulator (LQR) vibration control of smart piezoelectric composite plates, we propose the use of the total weighted energy method to select the weighting matrices. By constructing the optimal performance function as a relative measure of the total kinetic energy, strain energy and input energy of the system, only three design variables need to be considered to achieve a balance between the desired higher damping effect and lower input cost. Modal control analysis is used to interpret the effects of three energy weight factors on the damping ratios and modal voltages and it is shown that the modal damping effect will increase with the kinetic energy weight factor, approaching square root (2/2) as the strain energy weight factor increases and decrease with the input energy weight factor. Numerical results agree well with those from the modal control analysis. Since the control problem is simplified to three design variables only, the computational cost will be greatly reduced and a more accurate structural control analysis becomes more attractive for large systems

total weighted energy;total kinetic energy;weighting matrices;damping effect;numerical results;vibration control;optimal performance function;strain energy weight factor;damping ratios;smart piezoelectric composite plates;modal control analysis;computational cost;strain energy;structural control analysis;finite element linear quadratic regulator

train_929

Closed loop finite-element modeling of active constrained layer damping in the

time domain analysis A three-dimensional finite-element closed-loop model has been developed to predict the effects of active-passive damping on a vibrating structure. The Golla-Hughes-McTavish method is employed to capture the viscoelastic material behavior in a time domain analysis. The parametric study includes the different control gains as well as geometric parameters related to the active constrained layer damping (ACLD) treatment. Comparisons are made among several ACLD models, the passive constrained model and the active damping model. The results obtained here reiterate that ACLD is somewhat better for vibration suppression than either the purely passive or the active system and provides higher structural damping with less control gain when compared to the purely active system. Since the ACLD performance can be reduced by the viscoelastic layer, the design of the ACLD model must be given a careful consideration in order to optimize the effect of passive damping

active constrained layer damping;golla-hughes-mctavish method;acld models;viscoelastic layer;structural damping;viscoelastic material;time domain analysis;passive constrained model;active damping model;vibration suppression;passive damping;three-dimensional finite-element closed-loop model

train_93

Help-desk support is key to wireless success [finance]

A well thought out help desk can make or break an institution's mobile play. Schwab, Ameritrade and RBC are taking their support function seriously

ameritrade;schwab;finance;wireless;rbc;help desk

train_930

NARX-based technique for the modelling of magneto-rheological damping devices

This paper presents a methodology for identifying variable-structure nonlinear models of magneto-rheological dampers (MRD) and similar devices. Its peculiarity with respect to the mainstream literature is to be especially conceived for obtaining models that are structurally simple, easy to estimate and well suited for model-based control. This goal is pursued by adopting linear-in-the-parameters NARX models, for which an identification method is developed based on the minimization of the simulation error. This method is capable of selecting the model structure together with the parameters, thus it does not require a priori structural information. A set of validation tests is reported, with the aim of demonstrating the technique's efficiency by comparing it to a widely accepted MRD modelling approach

identification;narx models;magnetorheological damping;modelling;minimization;validation;simulation error;model-based control;mrd modelling

train_931

Active vibration control of composite sandwich beams with piezoelectric

extension-bending and shear actuators We have used quasi-static equations of piezoelectricity to derive a finite element formulation capable of modelling two different kinds of piezoelastically induced actuation in an adaptive composite sandwich beam. This formulation is made to couple certain piezoelectric constants to a transverse electric field to develop extension-bending actuation and shear-induced actuation. As an illustration, we present a sandwich model of three sublaminates: face/core/face. We develop a control scheme based on the linear quadratic regulator/independent modal space control (LQR/IMSC) method and use this to estimate the active stiffness and the active damping introduced by shear and extension-bending actuators. To assess the performance of each type of actuator, a dynamic response study is carried out in the modal domain. We observe that the shear actuator is more efficient in actively controlling the vibration than the extension-bending actuator for the same control effort

quasi-static equations;dynamic response;shear actuators;finite element formulation;shear-induced actuation;piezoelastically;transverse electric field;active stiffness;piezoelectric constants;adaptive composite sandwich beam;linear quadratic regulator;modal domain;finite element procedure;sandwich model;piezoelectricity;sublaminates;extension-bending actuation;modal space control;active damping;extension-bending actuators

train_932

Modeling of torsional vibration induced by extension-twisting coupling of

anisotropic composite laminates with piezoelectric actuators In this paper we present a dynamic analytical model for the torsional vibration of an anisotropic piezoelectric laminate induced by the extension-twisting coupling effect. In the present approach, we use the Hamilton principle and a reduced bending stiffness method for the derivation of equations of motion. As a result, the in-plane displacements are not involved and the out-of-plane displacement of the laminate is the only quantity to be calculated. Therefore, the proposed method turns the twisting of a laminate with structural coupling into a simplified problem without losing its features. We give analytical solutions of the present model with harmonic excitation. A parametric study is performed to demonstrate the present approach

reduced bending stiffness;piezoelectric actuators;hamilton principle;pzt;out-of-plane displacement;structural coupling;twisting;equations of motion;torsional vibration;material anisotropy;in-plane displacements;harmonic excitation;anisotropic piezoelectric laminate;anisotropic composite laminates;extension -twisting coupling;extension-twisting coupling effect;composite laminate;dynamic analytical model;parametric study

train_933

Real-time estimations of multi-modal frequencies for smart structures

In this paper, various methods for the real-time estimation of multi-modal frequencies are realized in real time and compared through numerical and experimental tests. These parameter-based frequency estimation methods can be applied to various engineering fields such as communications, radar and adaptive vibration and noise control. Well-known frequency estimation methods are introduced and explained. The Bairstow method is introduced to find the roots of a characteristic equation for estimations of multi-modal frequencies, and the computational efficiency of the Bairstow method is shown quantitatively. For a simple numerical test, we consider two sinusoids of the same amplitudes mixed with various amounts of white noise. The test results show that the auto regressive (AR) and auto regressive and moving average (ARMA) methods are unsuitable in noisy environments. The other methods apart from the AR method have fast tracking capability. From the point of view of computational efficiency, the results reveal that the ARMA method is inefficient, while the cascade notch filter method is very effective. The linearized adaptive notch filter and recursive maximum likelihood methods have average performances. Experimental tests are devised to confirm the feasibility of real-time computations and to impose the severe conditions of drastically different amplitudes and of considerable changes of natural frequencies. We have performed experiments to extract the natural frequencies from the vibration signal of wing-like composite plates in real time. The natural frequencies of the specimen are changed by added masses. Especially, the AR method exhibits a remarkable performance in spite of the severe conditions. This study will be helpful to anyone who needs a frequency estimation algorithm for real-time applications

multi-modal frequencies;characteristic equation;real-time estimation;real-time computations;frequency estimation;linearized adaptive notch filter;arma;wing-like composite plates;smart structures;auto regressive and moving average methods;bairstow method;frequency estimation algorithm;cascade notch filter;noise control;real-time applications;vibration signal;adaptive vibration control;recursive maximum likelihood methods

train_934

Induced-shear piezoelectric actuators for rotor blade trailing edge flaps

Much of the current rotorcraft research is focused on improving performance by reducing unwanted helicopter noise and vibration. One of the most promising active rotorcraft vibration control systems is an active trailing edge flap. In this paper, an induced-shear piezoelectric tube actuator is used in conjunction with a simple lever-cusp hinge amplification device to generate a useful combination of trailing edge flap deflections and hinge moments. A finite-element model of the actuator tube and trailing edge flap (including aerodynamic and inertial loading) was used to guide the design of the actuator-flap system. A full-scale induced shear tube actuator flap system was fabricated and bench top testing was conducted to validate the analysis. Hinge moments corresponding to various rotor speeds were applied to the actuator using mechanical springs. The testing demonstrated that for an applied electric field of 3 kV cm/sup -1/ the tube actuator deflected a representative full-scale 12 inch flap +or-2.8 degrees at 0 rpm and +or-1.4 degrees for a hinge moment simulating a 400 rpm condition. The per cent error between the predicted and experimental full-scale flap deflections ranged from 4% (low rpm) to 12.5% (large rpm). Increasing the electric field to 4 kV cm/sup -1/ results in +or-2.5 degrees flap deflection at a rotation speed of 400 rpm, according to the design analysis. A trade study was conducted to compare the performance of the piezoelectric tube actuator to the state of the art in trailing edge flap actuators and indicated that the induced-shear tube actuator shows promise as a trailing edge flap actuator

finite-element model;vibration control;shear tube actuator flap;aerodynamic loading;inertial loading;12 inch flap;piezoelectric tube actuator;helicopter vibration;helicopter noise;design;active trailing edge flap;12 inch;bench top testing;induced-shear tube actuator;lever-cusp hinge amplification device;rotorcraft

train_935

Experimental feedforward and feedback control of a one-dimensional SMA

composite The control of embedded shape memory alloy (SMA) actuators has recently become a topic of interest in the field of smart structures. The inherent difficulties associated with SMA actuators has resulted in a variety of approaches. Homogenization provides a simplified, yet mathematically rigorous, method of determining average stress and strain fields in a composite. A modified constitutive model is presented based on experimental results demonstrating the inability of most simple phenomenological models to capture the effective behavior of SMAs during thermal activation. A feedforward controller is presented for a SMA composite based on the homogenization of a modified phenomenological model for SMAs in a linear matrix

homogenization;sma actuators;smart structures;embedded shape memory alloy;linear matrix;sma;thermal activation;models

train_936

Resonant controllers for smart structures

In this paper we propose a special type of colocated feedback controller for smart structures. The controller is a parallel combination of high-Q resonant circuits. Each of the resonant circuits is tuned to a pole (or the resonant frequency) of the smart structure. It is proven that the parallel combination of resonant controllers is stable with an infinite gain margin. Only one set of actuator-sensor can damp multiple resonant modes with the resonant controllers. Experimental results are presented to show the robustness of the proposed controller in damping multimode resonances

damping;actuator-sensor;multiple resonant modes;feedback controller;smart structure;smart structures;resonant frequency;multimode resonances;laminate beam;high-q resonant circuits

train_937

Use of neural networks in the analysis of particle size distribution by laser

diffraction: tests with different particle systems The application of forward light scattering methods for estimating the particle size distribution (PSD) is usually limited by the occurrence of multiple scattering, which affects the angular distribution of light in highly concentrated suspensions, thus resulting in false calculations by the conventionally adopted algorithms. In this paper, a previously proposed neural network-based method is tested with different particle systems, in order to evaluate its applicability. In the first step of the study, experiments were carried out with solid-liquid suspensions having different characteristics of particle shape and size distribution, under varying solid concentrations. The experimental results, consisting of the angular distribution of light intensity, particle shape and suspension concentration, were used as input data in the fitting of neural network models (NN) that replaced the optical model to provide the PSD. The reference values of particle shape and PSD for the NN fitting were based on image analysis. Comparisons between the PSD values computed by the NN model and the reference values indicate that the method can be used in monitoring the PSD of particles with different shapes in highly concentrated suspensions, thus extending the range of application of forward laser diffraction to a number of systems with industrial interest

angular distribution of light;fraunhofer optical model;particle shape distribution;solid-liquid suspensions;fluidized catalytic cracking;particle size distribution;laser diffraction;multiple scattering;pattern recognition;powdered materials;forward light scattering;neural network modeling;backpropagation algorithm;image analysis

train_938

Fast accurate MEG source localization using a multilayer perceptron trained

with real brain noise Iterative gradient methods such as Levenberg-Marquardt (LM) are in widespread use for source localization from electroencephalographic (EEG) and magnetoencephalographic (MEG) signals. Unfortunately, LM depends sensitively on the initial guess, necessitating repeated runs. This, combined with LM's high per-step cost, makes its computational burden quite high. To reduce this burden, we trained a multilayer perceptron (MLP) as a realtime localizer. We used an analytical model of quasistatic electromagnetic propagation through a spherical head to map randomly chosen dipoles to sensor activities according to the sensor geometry of a 4D Neuroimaging Neuromag-122 MEG system, and trained a MLP to invert this mapping in the absence of noise or in the presence of various sorts of noise such as white Gaussian noise, correlated noise, or real brain noise. A MLP structure was chosen to trade off computation and accuracy. This MLP was trained four times, with each type of noise. We measured the effects of initial guesses on LM performance, which motivated a hybrid MLP-start-LM method, in which the trained MLP initializes LM. We also compared the localization performance of LM, MLPs, and hybrid MLP-start-LMs for realistic brain signals. Trained MLPs are much faster than other methods, while the hybrid MLP-start-LMs are faster and more accurate than fixed-4-start-LM. In particular, the hybrid MLP-start-LM initialized by a MLP trained with the real brain noise dataset is 60 times faster and is comparable in accuracy to random-20-start-LM, and this hybrid system (localization error: 0.28 cm, computation time: 36 ms) shows almost as good performance as optimal-1-start-LM (localization error: 0.23 cm, computation time: 22 ms), which initializes LM with the correct dipole location. MLPs trained with noise perform better than the MLP trained without noise, and the MLP trained with real brain noise is almost as good an initial guesser for LM as the correct dipole location

real brain noise;iterative gradient methods;meg source localization;multilayer perceptron;forward model;levenberg-marquardt method;quasistatic electromagnetic propagation;spherical head;correlated noise;fast accurate localization;computation accuracy;analytical model;real-time localizer;white gaussian noise

train_939

Image reconstruction from fan-beam projections on less than a short scan

This work is concerned with 2D image reconstruction from fan-beam projections. It is shown that exact and stable reconstruction of a given region-of-interest in the object does not require all lines passing through the object to be measured. Complete (non-truncated) fan-beam projections provide sufficient information for reconstruction when 'every line passing through the region-of-interest intersects the vertex path in a non-tangential way'. The practical implications of this condition are discussed and a new filtered-backprojection algorithm is derived for reconstruction. Experiments with computer-simulated data are performed to support the mathematical results

region-of-interest;x-ray computed tomography;exact stable reconstruction;fan-beam projections;vertex path;3d head phantom;2d image reconstruction;convolution;short-scan condition;radon transform;linear interpolation;rebinning formula;hilbert transform;filtered-backprojection algorithm

train_94

Gearing up for CLS bank

Continuous-Linked Settlement, a dream of the foreign-exchange community for years, may finally become a reality by the end of 2002

foreign-exchange;continuous-linked settlement

train_940

Tools for the analysis of dose optimization. I. Effect-volume histogram

With the advent of dose optimization algorithms, predominantly for intensity-modulated radiotherapy (IMRT), computer software has progressed beyond the point of being merely a tool at the hands of an expert and has become an active, independent mediator of the dosimetric conflicts between treatment goals and risks. To understand and control the internal decision finding as well as to provide means to influence it, a tool for the analysis of the dose distribution is presented which reveals the decision-making process performed by the algorithm. The internal trade-offs between partial volumes receiving high or low doses are driven by functions which attribute a weight to each volume element. The statistics of the distribution of these weights is cast into an effect-volume histogram (EVH) in analogy to dose-volume histograms. The analysis of the EVH reveals which traits of the optimum dose distribution result from the defined objectives, and which are a random consequence of under- or misspecification of treatment goals. The EVH can further assist in the process of finding suitable objectives and balancing conflicting objectives. If biologically inspired objectives are used, the EVH shows the distribution of local dose effect relative to the prescribed level

insufficient target coverage;exponential law;treatment goals;one-sided quadratic penalties;low doses;objective function;dose optimization algorithms;treatment risks;treatment planning;quadratic overdose penalty;decision-making process;effect-volume histogram;cell survival;computer software;partial volumes;volume element weights;intensity-modulated radiotherapy;high doses;dosimetric conflicts

train_941

Option pricing formulas based on a non-Gaussian stock price model

Options are financial instruments that depend on the underlying stock. We explain their non-Gaussian fluctuations using the nonextensive thermodynamics parameter q. A generalized form of the Black-Scholes (BS) partial differential equation (1973) and some closed-form solutions are obtained. The standard BS equation (q = 1) which is used by economists to calculate option prices requires multiple values of the stock volatility (known as the volatility smile). Using q = 1.5 which well models the empirical distribution of returns, we get a good description of option prices using a single volatility

stock volatility;nongaussian stock price model;black-scholes partial differential equation;closed-form solutions;volatility smile;option pricing formulas;financial instruments;empirical distribution;nonextensive thermodynamics parameter

train_942

Micro-optical realization of arrays of selectively addressable dipole traps: a

scalable configuration for quantum computation with atomic qubits We experimentally demonstrate novel structures for the realization of registers of atomic qubits: We trap neutral atoms in one- and two-dimensional arrays of far-detuned dipole traps obtained by focusing a red-detuned laser beam with a microfabricated array of microlenses. We are able to selectively address individual trap sites due to their large lateral separation of 125 mu m. We initialize and read out different internal states for the individual sites. We also create two interleaved sets of trap arrays with adjustable separation, as required for many proposed implementations of quantum gate operations

neutral atoms;quantum computation;scalable configuration;far-detuned dipole traps;internal states;microfabricated array;atomic qubits;registers;red-detuned laser beam;microlenses;quantum gate operations

train_943

Implementation of universal quantum gates based on nonadiabatic geometric

phases We propose an experimentally feasible scheme to achieve quantum computation based on nonadiabatic geometric phase shifts, in which a cyclic geometric phase is used to realize a set of universal quantum gates. Physical implementation of this set of gates is designed for Josephson junctions and for NMR systems. Interestingly, we find that the nonadiabatic phase shift may be independent of the operation time under appropriate controllable conditions. A remarkable feature of the present nonadiabatic geometric gates is that there is no intrinsic limitation on the operation time

nonadiabatic geometric phase shifts;quantum computation;josephson junctions;nmr systems;nonadiabatic geometric gates;operation time;universal quantum gates;cyclic geometric phase;nonadiabatic phase shift

train_944

Conditions for the local manipulation of Gaussian states

We present a general necessary and sufficient criterion for the possibility of a state transformation from one mixed Gaussian state to another of a bipartite continuous-variable system with two modes. The class of operations that will be considered is the set of local Gaussian completely positive trace-preserving maps

bipartite continuous-variable system;quantum information theory;local manipulation;trace-preserving maps;gaussian states;state transformation

train_945

Testing statistical bounds on entanglement using quantum chaos

Previous results indicate that while chaos can lead to substantial entropy production, thereby maximizing dynamical entanglement, this still falls short of maximality. Random matrix theory modeling of composite quantum systems, investigated recently, entails a universal distribution of the eigenvalues of the reduced density matrices. We demonstrate that these distributions are realized in quantized chaotic systems by using a model of two coupled and kicked tops. We derive an explicit statistical universal bound on entanglement, which is also valid for the case of unequal dimensionality of the Hilbert spaces involved, and show that this describes well the bounds observed using composite quantized chaotic systems such as coupled tops

statistical bounds;entropy production;hilbert spaces;kicked tops;random matrix theory;maximality;quantized chaotic systems;universal distribution;entanglement;reduced density matrices;composite quantum systems;quantum chaos

train_946

Entanglement measures with asymptotic weak-monotonicity as lower (upper) bound

for the entanglement of cost (distillation) We propose entanglement measures with asymptotic weak-monotonicity. We show that a normalized form of entanglement measures with the asymptotic weak-monotonicity are lower (upper) bound for the entanglement of cost (distillation)

entanglement of cost;asymptotic weak-monotonicity;distillation;entanglement measures

train_947

The fully entangled fraction as an inclusive measure of entanglement

applications Characterizing entanglement in all but the simplest case of a two qubit pure state is a hard problem, even understanding the relevant experimental quantities that are related to entanglement is difficult. It may not be necessary, however, to quantify the entanglement of a state in order to quantify the quantum information processing significance of a state. It is known that the fully entangled fraction has a direct relationship to the fidelity of teleportation maximized under the actions of local unitary operations. In the case of two qubits we point out that the fully entangled fraction can also be related to the fidelities, maximized under the actions of local unitary operations, of other important quantum information tasks such as dense coding, entanglement swapping and quantum cryptography in such a way as to provide an inclusive measure of these entanglement applications. For two qubit systems the fully entangled fraction has a simple known closed-form expression and we establish lower and upper bounds of this quantity with the concurrence. This approach is readily extendable to more complicated systems

teleportation;fully entangled fraction;two qubit pure state;fidelity;quantum cryptography;entanglement;quantum information processing;entanglement swapping

train_948

Pairwise thermal entanglement in the n-qubit (n <or= 5) Heisenberg XX chain

We have calculated the concurrence of the pairwise thermal entanglement for the four-qubit and five-qubit Heisenberg XX chain. It is found that there is a great difference between the even-qubit and the odd-qubit chain in the aspect of the critical temperature and of the existence of the entanglement for the case of the qubit number n no more than 5

five-qubit heisenberg xx chain;four-qubit heisenberg xx chain;pairwise thermal entanglement;even-qubit chain;critical temperature;odd-qubit chain

train_949

Reply to "Comment on: Teleportation of an unknown state by W state" [Phys.

Lett. A 300 (2002) 324] In our letter (see ibid., vol. 296, p. 161 (2002)), the main question we consider is whether a general three-particle W state can be used to realize the teleportation of an unknown qubit state. We give the positive answer to this question in our letter, and show that W state can be used to realize to do that probabilistically. We also discuss how to do it in detail in our letter. In the previous comment (see ibid., vol. 300, p. 324 (2002)), authors check carefully the mathematics calculation of our letter, find and point out a simple mathematics error about normalization coefficient of Eq. (1). This mathematics error induces the incorrect probability calculation of Eq. (6), and also an incorrect claim in first part of our letter

teleportation;three-particle w state;qubit state;unknown state;probability calculation;normalization coefficient

train_95

SIA shelves T+1 decision till 2004

The Securities Industry Association has decided that a move to T+1 is more than the industry can handle right now. STP, however, will remain a focus

t+1;securities industry association;straight-through-processing

train_950

Quantum sensitive dependence

Wave functions of bounded quantum systems with time-independent potentials, being almost periodic functions, cannot have time asymptotics as in classical chaos. However, bounded quantum systems with time-dependent interactions, as used in quantum control, may have continuous spectrum and the rate of growth of observables is an issue of both theoretical and practical concern. Rates of growth in quantum mechanics are discussed by constructing quantities with the same physical meaning as those involved in the classical Lyapunov exponent. A generalized notion of quantum sensitive dependence is introduced and the mathematical structure of the operator matrix elements that correspond to different types of growth is characterized

classical chaos;quantum complexity;classical lyapunov exponent;time-independent potentials;time-dependent interactions;operator matrix elements;periodic functions;quantum control;quantum sensitive dependence;wave functions;bounded quantum systems;time asymptotics

train_951

How to drive strategic innovation [law firms]

Innovation. It has everything to do with organization and attitude. Marginal improvement isn't enough anymore. Convert your problem-solving skills into a new value for the entire firm. 10 initiatives

change;strategic innovation;law firms;management;clients;experiments

train_953

Take it to the next level [law firm innovation]

It's called innovating. Our clients do it. Our culture worships it. Our future hinges on it. Why is it so difficult in law firms? How can we make it easier? Viva la difference!

law firms;innovation

train_954

Caring for your new lawyers

In any given year, a striking number of lawyers are in a state of flux, from newly minted law school graduates looking for their first job, to senior litigators migrating to new challenges with new firms. The one certainty is that lawyers new to any firm need care and feeding in myriad ways. All of them need to know and understand three things: (1) the firm's culture; (2) the resources available to help them develop their practices; and (3) where to get help and guidance for research and practice purposes. Obtaining a thorough understanding of a new firm's workings may be the greatest research project lawyers face. How can a firm help its new lawyers learn what they need to know? To offer an example, here are programs in place at my firm

resources;firm's culture;new lawyers

train_955

From the DOS dog days to e-filing [law firms]

The poster child for a successful e-filing venture is the Case Management and Electronic Case File system now rolling through the district and bankruptcy courts. A project of the Administrative Office of the United States Courts, CM/ECF is a loud proponent of the benefits of the PDF approach and it has a full head of steam. Present plans are for all federal courts to implement CM/ECF by 2005. That means a radical shift in methodology and tools for a lot of lawyers. It also means that you should get cozy with Acrobat real soon

pdf;adobe acrobat;united states courts;case management and electronic case file system;e-filing

train_956

Do you see what I see? [visual technology in law firms]

Think of how well-done computer presentations can aid in the learning experience. They are, however, less common in client meetings, settlement conferences and the courtroom. And you have to wonder why, when the same benefits of attention focus and visual learning apply in those legal communication settings. The software and hardware components are easy to use, and they're increasingly affordable to boot. The next time you need to convey a point to an audience (be it one person or many), think of how you might benefit from the visual impact available through presentation software like PowerPoint. Anyone will understand you more easily when assisted by visual input, and it may make all the difference in reaching visual-focused learners

law firms;computer presentations;visual technology;powerpoint

train_957

A Blog in every law firm?

You don't know today what you'll want to know next year. Rather than trying to solve that problem, focus on providing simple tools to users that create valuable content across the firm. Individual contributions will be more visible, and you will have a searchable archive of your institutional memory and a simplified process for ensuring everyone is up to speed. Whether you embrace weblogs for their individual or institutional benefits, one thing is certain: They will become powerful tools for those who seek ways to more efficiently and intelligently manage information

web site;law firm;institutional memory;weblogs

train_958

Efficient combinational verification using overlapping local BDDs and a hash

table We propose a novel methodology that combines local BDDs (binary decision diagrams) with a hash table for very efficient verification of combinational circuits. The main purpose of this technique is to remove the considerable overhead associated with case-by-case verification of internal node pairs in typical internal correspondence based verification methods. Two heuristics based on the number of structural levels of circuitry looked at and the total number of nodes in the BDD manager are used to control the BDD sizes and introduce new cutsets based on already found equivalent nodes. We verify the ISCAS85 benchmark circuits and demonstrate significant speedup over existing methods. We also verify several hard industrial circuits and show our superiority in extracting internal equivalences

internal node pairs;bdd sizes;formal verification;cutsets;overlapping local bdds;internal equivalences;bdd manager;hash table;combinational verification;iscas85 benchmark circuits;binary decision diagrams;structural levels;combinational circuit verification;hard industrial circuits;heuristics;internal correspondence-based verification;internal correspondence based verification;case-by-case verification

train_959

Silicon debug of a PowerPC TM microprocessor using model checking

When silicon is available, newly designed microprocessors are tested in specially equipped hardware laboratories, where real applications can be run at hardware speeds. However, the large volumes of code being run, plus the limited access to the internal nodes of the chip, make it very difficult to characterize the nature of any failures that occur. We describe how temporal logic model checking was used to quickly characterize a design error exhibited during hardware testing of a PowerPC microprocessor. We outline the conditions under which model checking can efficiently characterize such failures, and show how the particular error we detected could have been revealed early in the design cycle, by model checking a short and simple correctness specification. We discuss the implications of this for verification methodologies over the full design cycle

model checking;circuit design error;hardware testing;verification methodologies;correctness specification;computation tree logic;powerpc microprocessor;circuit debugging;temporal logic

train_96

OMS battle heating up as Chicago Equity ousts LongView for Macgregor

Chicago Equity Partners LLC has gone into full production with Macgregor's Financial Trading Platform. This marks a concentrated effort to achieve straight-through processing

straight-through processing;longview;macgregor;financial trading platform;chicago equity partners

train_960

Bisimulation minimization and symbolic model checking

State space minimization techniques are crucial for combating state explosion. A variety of explicit-state verification tools use bisimulation minimization to check equivalence between systems, to minimize components before composition, or to reduce a state space prior to model checking. Experimental results on bisimulation minimization in symbolic model checking contexts, however, are mixed. We explore bisimulation minimization as an optimization in symbolic model checking of invariance properties. We consider three bisimulation minimization algorithms. From each, we produce a BDD-based model checker for invariant properties and compare this model checker to a conventional one based on backwards reachability. Our comparisons, both theoretical and experimental, suggest that bisimulation minimization is not viable in the context of invariance verification, because performing the minimization requires as many, if not more, computational resources as model checking the unminimized system through backwards reachability

experimental results;state space minimization techniques;binary decision diagram;invariance properties;invariance verification;optimization;explicit-state verification tools;bisimulation minimization;state explosion;backwards reachability;symbolic model checking;bdd

train_961

Modular and visual specification of hybrid systems: an introduction to HyCharts

Visual description techniques are particularly important for the design of hybrid systems, because specifications of such systems usually have to be discussed between engineers from a number of different disciplines. Modularity is vital for hybrid systems not only because it allows to handle large systems, but also because it permits to think in terms of components, which is familiar to engineers. Based on two different interpretations for hierarchic graphs and on a clear hybrid computation model, we develop HyCharts. HyCharts consist of two modular visual formalisms, one for the specification of the architecture and one for the specification of the behavior of hybrid systems. The operators on hierarchic graphs enable us to give a surprisingly simple denotational semantics for many concepts known from statechart-like formalisms. Due to a very general composition operator, HyCharts can easily be composed with description techniques from other engineering disciplines. Such heterogeneous system specifications seem to be particularly appropriate for hybrid systems because of their interdisciplinary character

visual description techniques;visual specification;hycharts;hierarchic graphs;hybrid computation model;modular specification;hybrid systems;heterogeneous system specifications;statechart;formal specification;denotational semantics;components

train_962

Optimal control using the transport equation: the Liouville machine

Transport theory describes the scattering behavior of physical particles such as photons. Here we show how to connect this theory to optimal control theory and to adaptive behavior of agents embedded in an environment. Environments and tasks are defined by physical boundary conditions. Given some task, we compute a set of probability densities on continuous state and action and time. From these densities we derive an optimal policy such that for all states the most likely action maximizes the probability of reaching a predefined goal state. Liouville's conservation theorem tells us that the conditional density at time t, state s, and action a must equal the density at t + dt, s + ds, a + da. Discretization yields a linear system that can be solved directly and whose solution corresponds to an optimal policy. Discounted reward schemes are incorporated naturally by taking the Laplace transform of the equations. The Liouville machine quickly solves rather complex maze problems

optimal control;liouville machine;transport equation;physical particles;embedded agents;scattering behavior;adaptive behavior

train_963

A computational model of learned avoidance behavior in a one-way avoidance

experiment We present a computational model of learned avoidance behavior in a one-way avoidance experiment. Our model employs the reinforcement learning paradigm and a temporal-difference algorithm to implement both classically conditioned and instrumentally conditioned components. The role of the classically conditioned component is to develop an expectation of future benefit that is a function of the learning system's state and action. Competition among the instrumentally conditioned components determines the overt behavior generated by the learning system. Our model displays, in simulation, the reduced latency of the avoidance behavior during learning with continuing trials and the resistance to extinction of the avoidance response. These results are consistent with experimentally observed animal behavior. Our model extends the traditional two-process learning mechanism of Mowrer (1947) by explicitly defining the mechanisms of proprioceptive feedback, an internal clock, and generalization over the action space

reinforcement learning;reduced latency;internal clock;animal behavior;computational model;traditional two-process learning mechanism;proprioceptive feedback;temporal-difference algorithm;instrumentally conditioned components;classically conditioned components;one-way avoidance experiment;learned avoidance behavior

train_964

Modeling group foraging: individual suboptimality, interference, and a kind of

matching A series of agent-based models support the hypothesis that behaviors adapted to a group situation may be suboptimal (or "irrational") when expressed by an isolated individual. These models focus on two areas of current concern in behavioral ecology and experimental psychology: the "interference function" (which relates the intake rate of a focal forager to the density of conspecifics) and the "matching law" (which formalizes the observation that many animals match the frequency of their response to different stimuli in proportion to the reward obtained from each stimulus type). Each model employs genetic algorithms to evolve foraging behaviors for multiple agents in spatially explicit environments, structured at the level of situated perception and action. A second concern of the article is to extend the understanding of both matching and interference per se by modeling at this level

group foraging;group situation;individual suboptimality;suboptimal behavior;interference function;multiple agents;focal forager;genetic algorithms;situated action;behavioral ecology;matching law;agent-based models;experimental psychology;spatially explicit environments;situated perception;isolated individual

train_965

Sliding mode control of chaos in the cubic Chua's circuit system

In this paper, a sliding mode controller is applied to control the cubic Chua's circuit system. The sliding surface of this paper used is one dimension higher than the traditional surface and guarantees its passage through the initial states of the controlled system. Therefore, using the characteristic of this sliding mode we aim to design a controller that can meet the desired specification and use less control energy by comparing with the result in the current existing literature. The results show that the proposed controller can steer Chua's circuit system to the desired state without the chattering phenomenon and abrupt state change

cubic chua circuit system;chaos;state change;chattering;sliding mode control;mismatch disturbance;sliding surface;match disturbance

train_966

Controlling in between the Lorenz and the Chen systems

This letter investigates a new chaotic system and its role as a joint function between two complex chaotic systems, the Lorenz and the Chen systems, using a simple variable constant controller. With the gradual tuning of the controller, the controlled system evolves from the canonical Lorenz attractor to the Chen attractor through the new transition chaotic attractor. This evolving procedure reveals the forming mechanisms of all similar and closely related chaotic systems, and demonstrates that a simple control technique can be very useful in generating and analyzing some complex chaotic dynamical phenomena

chen attractors;chen system;transition chaotic attractor;lorenz system;tuning;lorenz attractor

train_967

On the relationship between parametric variation and state feedback in chaos

control In this Letter, we study the popular parametric variation chaos control and state-feedback methodologies in chaos control, and point out for the first time that they are actually equivalent in the sense that there exist diffeomorphisms that can convert one to the other for most smooth chaotic systems. Detailed conversions are worked out for typical discrete chaotic maps (logistic, Henon) and continuous flows (Rossler, Lorenz) for illustration. This unifies the two seemingly different approaches from the physics and the engineering communities on chaos control. This new perspective reveals some new potential applications such as chaos synchronization and normal form analysis from a unified mathematical point of view

rossler system;state-feedback;continuous flows;diffeomorphisms;logistic;henon map;lorenz system;parametric variation;chaos control

train_968

Stabilization of global invariant sets for chaotic systems: an energy based

control approach This paper presents a new control approach for steering trajectories of three-dimensional nonlinear chaotic systems towards stable stationary states or time-periodic orbits. The proposed method mainly consists in a sliding mode-based control design that is extended by an explicit consideration of system energy as basis for both controller design and system stabilization. The control objective is then to regulate the energy with respect to a shaped nominal representation implicitly related to system trajectories. In this paper, we establish some theoretical results to introduce the control design approach referred to as energy based sliding mode control. Then, some capabilities of the proposed approach are illustrated through examples related to the chaotic circuit of Chua

time-periodic orbits;sliding mode-based control;stable stationary states;three-dimensional nonlinear chaotic systems;chua's circuit;global invariant sets;energy based sliding mode control

train_969

Controlled projective synchronization in nonpartially-linear chaotic systems

Projective synchronization (PS), in which the state vectors synchronize up to a scaling factor, is usually observable only in partially linear systems. We show that PS could, by means of control, be extended to general classes of chaotic systems with nonpartial linearity. Performance of PS may also be manipulated by controlling the scaling factor to any desired value. In numerical experiments, we illustrate the applications to a Rossler system and a Chua's circuit. The feasibility of the control for high dimensional systems is demonstrated in a hyperchaotic system

rossler system;projective synchronization;hyperchaotic system;chua's circuit;scaling factor;nonpartially-linear chaotic systems;control

train_97

Philadelphia stock exchange taps TimesTen for database technology

PHLX rolls out Equity Options AutoQuote System to traders as the first application to leverage its enhanced data architecture

data architecture;timesten;philadelphia stock exchange;equity options autoquote system

train_970

Complex dynamics in nearly symmetric three-cell cellular neural networks

The paper introduces a class of third-order nonsymmetric Cellular Neural Networks (CNNs), and shows through computer simulations that they undergo a cascade of period doubling bifurcations which leads to the birth of a large-size complex attractor. A major point is that these bifurcations and complex dynamics happen in a small neighborhood of a particular CNN with a symmetric interconnection matrix

neuron interconnection matrix;stable limit cycles;nearly symmetric three-cell cellular neural networks;robustness;period doubling bifurcations;symmetric interconnection matrix;perturbations;complete stability;complex dynamics;large-size complex attractor;differential equations;cnn

train_971

Homogenization in L/sup infinity /

Homogenization of deterministic control problems with L/sup infinity / running cost is studied by viscosity solutions techniques. It is proved that the value function of an L/sup infinity / problem in a medium with a periodic micro-structure converges uniformly on the compact sets to the value function of the homogenized problem as the period shrinks to 0. Our main convergence result extends that of Ishii (Stochastic Analysis, control, optimization and applications, pp. 305-324, Birkhauser Boston, Boston, MA, 1999.) to the case of a discontinuous Hamiltonian. The cell problem is solved, but, as nonuniqueness occurs, the effective Hamiltonian must be selected in a careful way. The paper also provides a representation formula for the effective Hamiltonian and gives illustrations to calculus of variations, averaging and one-dimensional problems

optimal control;homogenization;value function;calculus of variations;cell problem;deterministic control;convergence;averaging;l/sup infinity / running cost

train_972

VoIP: leveraging existing cable architecture

As operators prepare to enter the voice-over-IP fray, they are searching for ways to leverage their existing two-way, interactive infrastructure. There are several approaches for supporting VoIP on top of the core IP transport network. The one garnering the most interest, especially in the United States, is based on the PacketCable 1.x architecture. This article discusses the PacketCable-based approach

voip;packetcable 1.x architecture;core ip transport network;two-way interactive infrastructure;cable architecture;voice-over-ip;united states;packetcable-based approach

train_973

Time-integration of multiphase chemistry in size-resolved cloud models

The existence of cloud drops leads to a transfer of chemical species between the gas and aqueous phases. Species concentrations in both phases are modified by chemical reactions and by this phase transfer. The model equations resulting from such multiphase chemical systems are nonlinear, highly coupled and extremely stiff. In the paper we investigate several numerical approaches for treating such processes. The droplets are subdivided into several classes. This decomposition of the droplet spectrum into classes is based on their droplet size and the amount of scavenged material inside the drops, respectively. The very fast dissociations in the aqueous phase chemistry are treated as forward and backward reactions. The aqueous phase and gas phase chemistry, the mass transfer between the different droplet classes among themselves and with the gas phase are integrated in an implicit and coupled manner by the second order BDF method. For this part we apply a modification of the code LSODE with special linear system solvers. These direct sparse techniques exploit the special block structure of the corresponding Jacobian. Furthermore we investigate an approximate matrix factorization which is related to operator splitting at the linear algebra level. The sparse Jacobians are generated explicitly and stored in a sparse form. The efficiency and accuracy of our time-integration schemes is discussed for four multiphase chemistry systems of different complexity and for a different number of droplet classes

multiphase chemical systems;chemical species;approximate matrix factorization;sparse jacobians;cloud drops;time-integration schemes;aqueous phase chemistry;multiphase chemistry;size-resolved cloud models;gas phase chemistry;air pollution modelling;linear algebra;operator splitting;chemical reactions

train_974

Extrapolation in Lie groups with approximated BCH-formula

We present an extrapolation algorithm for the integration of differential equations in Lie groups which is a suitable generalization of the well-known GBS-algorithm for ODEs. Sufficiently accurate approximations to the BCH-formula are required to reach a given order. We give such approximations with a minimized number of commutators

geometric integration;extrapolation methods;approximated bch-formula;differential equations;lie groups;gbs-algorithm

train_975

Algebraic conditions for high-order convergent deferred correction schemes

based on Runge-Kutta-Nystrom methods for second order boundary value problems In [T. Van Hecke, M. Van Daele, J. Comp. Appl. Math., vol. 132, p. 107-125, (2001)] the investigation of high-order convergence of deferred correction schemes for the numerical solution of second order nonlinear two-point boundary value problems not containing the first derivative, is made. The derivation of the algebraic conditions to raise the increase of order by the deferred correction scheme was based on Taylor series expansions. In this paper we describe a more elegant way by means of P-series to obtain this necessary conditions and generalize this idea to equations of the form y" = f (t, y, y')

second order boundary value problems;high-order convergent deferred correction schemes;second order nonlinear two-point boundary value problems;runge-kutta-nystrom methods;algebraic conditions;deferred correction schemes;taylor series expansions

train_976

Completion to involution and semidiscretisations

We discuss the relation between the completion to involution of linear over-determined systems of partial differential equations with constant coefficients and the properties of differential algebraic equations obtained by their semidiscretisation. For a certain class of "weakly over-determined" systems, we show that the differential algebraic equations do not contain hidden constraints, if and only if the original partial differential system is involutive. We also demonstrate how the formal theory can be used to obtain an existence and uniqueness theorem for smooth solutions of strongly hyperbolic systems and to estimate the drift off the constraints, if an underlying equation is numerically solved. Finally, we show for general linear systems how the index of differential algebraic equations obtained by semidiscretisations can be predicted from the result of a completion of the partial differential system

constant coefficients;differential algebraic equations;strongly hyperbolic systems;matrices;partial differential equations;semidiscretisations;involution;linear over-determined systems;index;uniqueness theorem;completion

train_977

Behavior of Runge-Kutta discretizations near equilibria of index 2 differential

algebraic systems We analyze Runge-Kutta discretizations applied to index 2 differential algebraic equations (DAE's) near equilibria. We compare the geometric properties of the numerical and the exact solutions. It is shown that projected and half-explicit Runge-Kutta methods reproduce the qualitative features of the continuous system in the vicinity of an equilibrium correctly. The proof combines cut-off and scaling techniques for index 2 differential algebraic equations with some invariant manifold results of Schropp (Geometric properties of Runge-Kutta discretizations for index 2 differential algebraic equations, Konstanzer Schriften in Mathematik und Informatik 128) and classical results for discretized ordinary differential equations

cut-off techniques;geometric properties;equilibria;index 2 differential algebraic systems;half-explicit runge-kutta methods;discretized ordinary differential equations;continuous system;invariant manifold;scaling techniques;runge-kutta discretizations

train_978

On Implicit Euler for high-order high-index DAEs

The Implicit Euler method is seldom used to solve differential-algebraic equations (DAEs) of differential index r >or= 3, since the method in general fails to converge in the first r - 2 steps after a change of stepsize. However, if the differential equation is of order d = r - 1 >or= 1, an alternative variable-step version of the Euler method can be shown uniformly convergent. For d = r - 1, this variable-step method is equivalent to the Implicit Euler except for the first r - 2 steps after a change of stepsize. Generalization to DAEs with differential equations of order d > r - 1 >or= 1, and to variable-order formulas is discussed

variable-order formulas;variable-step method;backward differentiation formula;initial value problem;linear multistep method;convergence;differential index;differential-algebraic equations;stepsize change;implicit euler method

train_979

Design, analysis and testing of some parallel two-step W-methods for stiff

systems Parallel two-step W-methods are linearly-implicit integration methods where the s stage values can be computed in parallel. We construct methods of stage order q = s and order p = s with favourable stability properties. Generalizations for the concepts of A- and L-stability are proposed and conditions for stiff accuracy are given. Numerical comparisons on a shared memory computer show the efficiency of the methods, especially in combination with Krylov-techniques for large stiff systems

stage order;krylov-techniques;linearly-implicit integration methods;shared memory computer;parallel two-step w-methods;convergence analysis;differential equations;stability;large stiff systems

train_98

Automating the compliance and supervision process

New technology enables large broker/dealers to supervise and ensure compliance across multiple branches and managers

supervision;compliance;brokers;risk management

train_980

Convergence of Runge-Kutta methods for nonlinear parabolic equations

We study time discretizations of fully nonlinear parabolic differential equations. Our analysis uses the fact that the linearization along the exact solution is a uniformly sectorial operator. We derive smooth and nonsmooth-data error estimates for the backward Euler method, and we prove convergence for strongly A (v)-stable Runge-Kutta methods. For the latter, the order of convergence for smooth solutions is essentially determined by the stage order of the method. Numerical examples illustrating the convergence estimates are presented

nonlinear parabolic differential equations;runge-kutta method convergence;nonsmooth-data error estimates;data error estimates;backward euler method;linearization;time discretizations;uniformly sectorial operator

train_981

Basin configuration of a six-dimensional model of an electric power system

As part of an ongoing project on the stability of massively complex electrical power systems, we discuss the global geometric structure of contacts among the basins of attraction of a six-dimensional dynamical system. This system represents a simple model of an electrical power system involving three machines and an infinite bus. Apart from the possible occurrence of attractors representing pathological states, the contacts between the basins have a practical importance, from the point of view of the operation of a real electrical power system. With the aid of a global map of basins, one could hope to design an intervention strategy to boot the power system back into its normal state. Our method involves taking two-dimensional sections of the six-dimensional state space, and then determining the basins directly by numerical simulation from a dense grid of initial conditions. The relations among all the basins are given for a specific numerical example, that is, choosing particular values for the parameters in our model

six-dimensional model;attractors;power system stability;global map;state space;infinite bus;pathological states;basin configuration;electric power system;global geometric structure;massively complex electrical power systems

train_982

Abundance of mosaic patterns for CNN with spatially variant templates

This work investigates the complexity of one-dimensional cellular neural network mosaic patterns with spatially variant templates on finite and infinite lattices. Various boundary conditions are considered for finite lattices and the exact number of mosaic patterns is computed precisely. The entropy of mosaic patterns with periodic templates can also be calculated for infinite lattices. Furthermore, we show the abundance of mosaic patterns with respect to template periods and, which differ greatly from cases with spatially invariant templates

spatial entropy;finite lattices;cnn;one-dimensional cellular neural network;infinite lattices;mosaic patterns;boundary conditions;spatially variant templates;transition matrix

train_983

Limitations of delayed state feedback: a numerical study

Stabilization of a class of linear time-delay systems can be achieved by a numerical procedure, called the continuous pole placement method [Michiels et al., 2000]. This method can be seen as an extension of the classical pole placement algorithm for ordinary differential equations to a class of delay differential equations. In [Michiels et al., 2000] it was applied to the stabilization of a linear time-invariant system with an input delay using static state feedback. In this paper we study the limitations of such delayed state feedback laws. More precisely we completely characterize the class of stabilizable plants in the 2D-case. For that purpose we make use of numerical continuation techniques. The use of delayed state feedback in various control applications and the effect of its limitations are briefly discussed

delay differential equations;static state feedback;linear time-delay systems;delayed state feedback;numerical continuation;continuous pole placement method

train_984

Bistability of harmonically forced relaxation oscillations

Relaxation oscillations appear in processes which involve transitions between two states characterized by fast and slow time scales. When a relaxation oscillator is coupled to an external periodic force its entrainment by the force results in a response which can include multiple periodicities and bistability. The prototype of these behaviors is the harmonically driven van der Pol equation which displays regions in the parameter space of the driving force amplitude where stable orbits of periods 2n+or-1 coexist, flanked by regions of periods 2n+1 and 2n-1. The parameter regions of such bistable orbits are derived analytically for the closely related harmonically driven Stoker-Haag piecewise discontinuous equation. The results are valid over most of the control parameter space of the system. Also considered are the reasons for the more complicated dynamics featuring regions of high multiple periodicity which appear like noise between ordered periodic regions. Since this system mimics in detail the less analytically tractable forced van der Pol equation, the results suggest extensions to situations where forced relaxation oscillations are a component of the operating mechanisms

harmonically driven stoker-haag piecewise discontinuous equation;external periodic force;harmonically forced relaxation oscillations;bistability;control parameter space;entrainment;nonlinear dynamics;van der pol equation

train_985

Local activity criteria for discrete-map CNN

Discrete-time CNN systems are studied in this paper by the application of Chua's local activity principle. These systems are locally active everywhere except for one isolated parameter value. As a result, nonhomogeneous spatiotemporal patterns may be induced by any initial setting of the CNN system when the strength of the system diffusion coupling exceeds a critical threshold. The critical coupling coefficient can be derived from the loaded cell impedance of the CNN system. Three well-known 1D map CNN's (namely, the logistic map CNN, the magnetic vortex pinning map CNN, and the spiral wave reproducing map CNN) are introduced to illustrate the applications of the local activity principle. In addition, we use the cell impedance to demonstrate the period-doubling scenario in the logistic and the magnetic vortex pinning maps

chua's local activity principle;spiral wave reproducing map cnn;local activity criteria;nonhomogeneous spatiotemporal patterns;period-doubling;logistic map cnn;difference equation;magnetic vortex pinning map cnn;critical coupling coefficient;discrete-time cnn systems;loaded cell impedance;discrete-map cnn

train_986

Wavelet-based level-of-detail representation of 3D objects

In this paper, we propose a 3D object LOD (Level of Detail) modeling system that constructs a mesh from range images and generates the mesh of various LOD using the wavelet transform. In the initial mesh generation, we use the marching cube algorithm. We modify the original algorithm to apply it to construct the mesh from multiple range images efficiently. To get the base mesh we use the decimation algorithm which simplifies a mesh with preserving the topology. Finally, when reconstructing new mesh which is similar to initial mesh we calculate the wavelet coefficients by using the wavelet transform. We solve the critical problem of wavelet-based methods - the surface crease problem - by using the mesh simplification as the base mesh generation method

range images;wavelet coefficients;hierarchy transformation;marching cube algorithm;surface crease problem;decimation algorithm;wavelet transform;3d object level of detail modeling system;critical problem;mesh simplification;wavelet-based level-of-detail representation;base mesh

train_987

Proof that the election problem belongs to NF-completeness problems in

asynchronous distributed systems This paper is about the hardness of the election problem in asynchronous distributed systems in which processes can crash but links are reliable. The hardness of the problem is defined with respect to the difficulty to solve it despite failures. It is shown that problems encountered in the system are classified as three classes of problems: F (fault-tolerant), NF (Not fault-tolerant) and NFC (NF-completeness). Among those, the class NFC are the hardest problems to solve. In this paper, we prove that the Election problem is the most difficult problem which belongs to the class NFC

not-fault-tolerant problems;distributed computing;nf-completeness problems;fault-tolerant problems;failure detectors;asynchronous distributed systems;leader election;election problem

train_988

A new merging algorithm for constructing suffix trees for integer alphabets

A new approach for constructing a suffix tree T/sub s/ for a given string S is to construct recursively a suffix tree T/sub o/ for odd positions, construct a suffix, tree T/sub e/ for even positions from T/sub o/ and then merge T/sub o/ and T/sub e/ into T/sub s/. To construct suffix trees for integer alphabets in linear time had been a major open problem on index data structures. Farach used this approach and gave the first linear-time algorithm for integer alphabets. The hardest part of Farach's algorithm is the merging step. In this paper we present a new and simpler merging algorithm based on a coupled BFS (breadth-first search). Our merging algorithm is more intuitive than Farach's coupled DFS (depth-first search) merging, and thus it can be easily extended to other applications

linear time;integer alphabets;recursive construction;coupled bfs;index data structures;suffix trees;breadth-first search;merging algorithm

train_989

A dynamic checkpoint scheduling scheme for fault tolerant distributed computing

systems The selection of the optimal checkpointing interval has been a very critical issue in implementing checkpointing-recovery schemes for fault tolerant distributed systems. This paper presents a new scheme that allows a process to select the proper checkpointing interval dynamically. A process in the system evaluates the cost of checkpointing and possible rollback for each checkpointing interval and selects the proper time interval for the next checkpointing. Unlike the other schemes, the overhead incurred by both the checkpointing and rollback activities are considered for the cost evaluation, and the current communication pattern is reflected in the selection of the checkpointing interval. Moreover, the proposed scheme requires no extra message communication for the checkpointing interval selection and can easily be incorporated into the existing checkpointing coordination schemes

optimal checkpointing interval;communication pattern;distributed computing systems;rollback recovery;dynamic checkpoint scheduling scheme;cost evaluation;fault tolerant computing

train_99

Radianz and Savvis look to expand service in wake of telecom scandals [finance]

With confidence in network providers waning, Radianz and Savvis try to prove their stability. Savvis and Radianz, which both specialize in providing the data-extranet components of telecommunication infrastructures, may see more networking doors open at investment banks, brokerage houses, exchanges and alternative-trading systems

network providers;radianz;data-extranet;alternative-trading systems;telecommunication infrastructures;brokerage houses;investment banks;savvis;exchanges

train_990

Pipelined broadcast with enhanced wormhole routers

This paper proposes a pipelined broadcast that broadcasts a message of size m in O(m+n-1) time in an n-dimensional hypercube. It is based on the replication tree, which is derived from reachable sets. It has greatly improved performance compared to Ho-Kao's (1995) algorithm with the time of O(m[n/log(n+1)]). The communication in the broadcast uses an all-port wormhole router with message replication capability. This paper includes the algorithm together with performance comparisons to previous schemes in a practical implementation

pipelined broadcast;replication tree;performance;enhanced wormhole routers;message broadcast;intermediate reception;all-port wormhole router;reachable sets;n-dimensional hypercube;communication complexity;message replication capability

train_991

Estimation of blocking probabilities in cellular networks with dynamic channel

assignment Blocking probabilities in cellular mobile communication networks using dynamic channel assignment are hard to compute for realistic sized systems. This computational difficulty is due to the structure of the state space, which imposes strong coupling constraints amongst components of the occupancy vector. Approximate tractable models have been proposed, which have product form stationary state distributions. However, for real channel assignment schemes, the product form is a poor approximation and it is necessary to simulate the actual occupancy process in order to estimate the blocking probabilities. Meaningful estimates of the blocking probability typically require an enormous amount of CPU time for simulation, since blocking events are usually rare. Advanced simulation approaches use importance sampling (IS) to overcome this problem. We study two regimes under which blocking is a rare event: low-load and high cell capacity. Our simulations use the standard clock (SC) method. For low load, we propose a change of measure that we call static ISSC, which has bounded relative error. For high capacity, we use a change of measure that depends on the current state of the network occupancy. This is the dynamic ISSC method. We prove that this method yields zero variance estimators for single clique models, and we empirically show the advantages of this method over naive simulation for networks of moderate size and traffic loads

importance sampling;standard clock method;quality of service;dynamic channel assignment;strong coupling constraints;blocking probability estimation;approximate tractable models;simulation;bounded relative error;dynamic issc method;single clique models;low-load;high cell capacity;product form stationary state distributions;occupancy vector;zero variance estimators;cellular mobile communication networks;cpu time;network traffic load;static issc method

train_992

Cross-entropy and rare events for maximal cut and partition problems

We show how to solve the maximal cut and partition problems using a randomized algorithm based on the cross-entropy method. For the maximal cut problem, the proposed algorithm employs an auxiliary Bernoulli distribution, which transforms the original deterministic network into an associated stochastic one, called the associated stochastic network (ASN). Each iteration of the randomized algorithm for the ASN involves the following two phases: (1) generation of random cuts using a multidimensional Ber(p) distribution and calculation of the associated cut lengths (objective functions) and some related quantities, such as rare-event probabilities; (2) updating the parameter vector p on the basis of the data collected in the first phase. We show that the Ber(p) distribution converges in distribution to a degenerated one, Ber(p/sub d/*), p/sub d/* = (p/sub d/,/sub 1/, p/sub d,n/) in the sense that some elements of p/sub d/*, will be unities and the rest zeros. The unity elements of p/sub d/* uniquely define a cut which will be taken as the estimate of the maximal cut. A similar approach is used for the partition problem. Supporting numerical results are given as well. Our numerical studies suggest that for the maximal cut and partition problems the proposed algorithm typically has polynomial complexity in the size of the network

rare event simulation;importance sampling;numerical results;randomized algorithm;combinatorial optimization;deterministic network;polynomial complexity;cross entropy method;maximal cut problems;random cuts;partition problems;probability;bernoulli distribution;associated stochastic network

train_993

A large deviations analysis of the transient of a queue with many Markov fluid

inputs: approximations and fast simulation This article analyzes the transient buffer content distribution of a queue fed by a large number of Markov fluid sources. We characterize the probability of overflow at time t, given the current buffer level and the number of sources in the on-state. After scaling buffer and bandwidth resources by the number of sources n, we can apply large deviations techniques. The transient overflow probability decays exponentially in n. In the case of exponential on/off sources, we derive an expression for the decay rate of the rare event probability under consideration. For general Markov fluid sources, we present a plausible conjecture. We also provide the "most likely path" from the initial state to overflow (at time t). Knowledge of the decay rate and the most likely path to overflow leads to (i) approximations of the transient overflow probability and (ii) efficient simulation methods of the rare event of buffer overflow. The simulation methods, based on importance sampling, give a huge speed-up compared to straightforward simulations. The approximations are of low computational complexity and are accurate, as verified by means of simulation experiments

transient buffer content distribution;approximations;importance sampling;buffer resources;simulation methods;bandwidth resources;markov fluid inputs;queuing theory;computational complexity;transient overflow probability;large deviations analysis;atm multiplexers;ip routers

train_994

Design and implementation of a flexible manufacturing control system using

neural network Design and implementation of a sequential controller based on the concept of artificial neural networks for a flexible manufacturing system are presented. The recurrent neural network (RNN) type is used for such a purpose. Contrary to the programmable controller, an RNN-based sequential controller is based on a definite mathematical model rather than depending on the experience and trial and error techniques. The proposed controller is also more flexible because it is not limited by the restrictions of the finite state automata theory. Adequate guidelines of how to construct an RNN-based sequential controller are presented. These guidelines are applied to different case studies. The proposed controller is tested by simulations and real-time experiments. These tests prove the successfulness of the proposed controller performances. Theoretical as well as experimental results are presented and discussed indicating that the proposed design procedure using Elman's RNN can be effective in designing a sequential controller for event-based type manufacturing systems. In addition, the simulation results assure the effectiveness of the proposed controller to overcome the effect of noisy inputs

recurrent neural network;sequential control;learning;pneumatic system;noisy inputs;fms;flexible manufacturing systems;elman network;programmable controller;ladder language;finite state automata

train_995

Vehicle travel time models for AGV systems under various dispatching rules

The design and evaluation of AGV-based material handling systems are highly complex because of the randomness and the large number of variables involved. Vehicle travel time is a fundamental parameter for solving various flexible manufacturing system (FMS) design problems. This article presents stochastic vehicle travel time models for AGV-based material handling systems with emphasis on the empty travel times of vehicles. Various vehicle dispatching rules examined here include the nearest vehicle selection rule and longest idle vehicle selection rule. A simulation experiment is used to evaluate and demonstrate the presented models

vehicle dispatching rules;longest idle vehicle selection rule;material handling systems;automatic guided vehicle;fms;agv;nearest vehicle selection rule;vehicle travel time;flexible manufacturing system

train_996

Flexible air-jet tooling for vibratory bowl feeder systems

Vibratory bowl feeders (VBFs) are machines that feed various small parts in large volume automatic assembly systems. Their shortcomings, like inflexibility and the propensity to jam, stem from the use of mechanical orienting devices. Air jet based orienting devices can be implemented to overcome these limitations. Applications of passive and active air jet based orienting devices that replace conventional devices for the VBF are discussed. Passive devices, which reject incorrectly oriented parts, are discussed first. Active air jet based orienting devices are then introduced to further improve the flexibility of VBFs. Since active devices reorient parts into a desired orientation, the part motion under their influence is analyzed. A number of tests demonstrate the feasibility and advantages of these new orienting devices

passive air jet;active air jet;parts feeding;orienting devices;automatic assembly systems;vibratory bowl feeders

train_997

Production capacity of flexible manufacturing systems with fixed production

ratios Determining the production capacity of flexible manufacturing systems is a very important issue in the design of such systems. We propose an approach for determining the production capacity (i.e. the maximum production rate) of a flexible manufacturing system with several part types, dedicated pallets, and fixed production ratios among the different part types. We show that the problem reduces to the determination of a single parameter for which we propose an iterative procedure. Simulation or approximate analytical techniques can be used as the building block performance evaluation technique in the iterative procedure

iterative procedure;approximate analytical techniques;single parameter determination;fixed production ratios;dedicated pallets;simulation;multiple part type;building block performance evaluation technique;maximum production rate;numerical experiments;flexible manufacturing systems;stability condition;production capacity

train_998

Discreteness and relevance: a reply to Roman Poznanski

In reply to Poznanski (see ibid., p.435, 2002) on discreteness and relevance, Eliasmith claims that all of the concerns voiced by Poznanski in his reply fail to offer a serious challenge to the idea that continuity is irrelevant to a good understanding of cognitive systems. Eliasmith hopes that it is evident that he does not claim that the process in neural systems is discrete, but rather that a complete characterization of the process can be discrete; these of course are significantly different claims

neural systems;relevance;discreteness;cognitive systems;continuity

train_999

The importance of continuity: a reply to Chris Eliasmith

In his reply to Eliasmith (see ibid., vol.11, p.417-26, 2001) Poznanski considers how the notion of continuity of dynamic representations serves as a beacon for an integrative neuroscience to emerge. He considers how the importance of continuity has come under attack from Eliasmith (2001) who claims: (i) continuous nature of neurons is not relevant to the information they process, and (ii) continuity is not important for understanding cognition because the various sources of noise introduce uncertainty into spike arrival times, so encoding and decoding spike trains must be discrete at some level

uncertainty;integrative neuroscience;spike trains;dynamic representations;neurons;cognition;neural nets;cognitive systems;continuity;spike arrival times