Discrete Subsystems Research Articles

OPTIMAL POWER SYSTEM MANAGEMENT VIA MIXED INTEGER DYNAMIC PROGRAMMING

Power systems involve both continuous and discrete acting components and subsystems. In this work a logical specification is used to define the transition dynamics of the discrete subsystem. A computational tool that reduces the logical specification to a set of inequalities and the use of the transformed model in a dynamic programming approach to the design of optimal feedback controls arc described. An example of optimal load shedding for a power system with aggregate induction motor and constant admittance loads is given.

Self-induced decoherence approach: Strong limitations on its validity in a simple spin bath model and on its general physical relevance

The ``self-induced decoherence'' (SID) approach suggests that (1) the expectation value of any observable becomes diagonal in the eigenstates of the total Hamiltonian for systems endowed with a continuous energy spectrum, and that (2) this process can be interpreted as decoherence. We evaluate the first claim in the context of a simple spin bath model. We find that even for large environments, corresponding to an approximately continuous energy spectrum, diagonalization of the expectation value of random observables does in general not occur. We explain this result and conjecture that SID is likely to fail also in other systems composed of discrete subsystems. Regarding the second claim, we emphasize that SID does not describe a physically meaningful decoherence process for individual measurements, but only involves destructive interference that occurs collectively within an ensemble of presupposed ``values'' of measurements. This leads us to question the relevance of SID for treating observed decoherence effects.

SOME RECENT RESULTS IN MOVING LOAD PROBLEMS WITH APPLICATION TO HIGHWAY BRIDGES

In this paper, some recent results obtained for various aspects of the moving load problem are discussed. While encompassing a range of problems involving discrete subsystems traversing a primary distributed parameter system, a simple vehicle crossing a bridge is used herein to demonstrate various effects and their relative importance.

A systems approach to electronic assembly optimization

There are many complex problems in the optimization of an electronics manufacturing environment, and it is the view of the authors that these problems should not be solved and optimized in isolation but analysed in the framework of a system. A systems approach offers an overall approach for solving problems, optimizing the whole of the system rather than discrete subsystems. The research introduced in this paper integrates several techniques, namely integrated computer aided manufacturing definition, experimental design and response surface methods for the analysis, control and optimization of electronic manufacturing processes. Electronics manufacturing includes three major processes: printed circuit board manufacturing, semiconductor device manufacturing and electronics assembly. This paper describes a generic systematic model for optimizing electronic assembly. Computer aided systems engineering methodology is introduced and a description of how this was applied to optimize electronic assembly within a manufacturing company using historical data is given together with a process map for electronic assembly. An analysis of the overall assembly operation is then used to generate the relationship between overall yield and yield of the subprocesses.

Models of the State of Multiple-Timing Continuous-Discrete Systems

Linear mathematical models of continuous-discrete dynamic systems are investigated on the assumption that the discrete subsystems are defined on several different time series.

A systems approach to photolithography process optimization in an electronics manufacturing environment

There are many complex problems in the optimization of an electronics manufacturing environment, and it is the view of the authors that these problems should not be solved and optimized in isolation, but analysed in the framework of a system. A systems approach offers an overall approach for solving problems, and optimizing the whole of the system as well as discrete subsystems. The research introduced in this paper integrates several techniques, namely: Integrated computer aided manufacturing DEFinition (IDEF), and experimental design and response surface methods for the analysis, control and optimization of electronic manufacturing processes. Electronics manufacturing includes three major processes; Printed Circuit Board (PCB) manufacturing, semiconductor device manufacturing and electronics assembly. This paper describes a novel generic systematic methodology that has been used to create a model to optimize the photolithography process in PCB manufacture. For this, photolithography has been considered as a whole system made up of several sub-systems. This is shown in the process map for PCBs that focuses on photolithography and its subprocesses. A model of the manufacturing process is then given with the results of this being validated using an industrial study. Optimized settings for processing equipment are given resulting in an increase in process yield within industry.

THE USE OF CONVENTIONAL AND MINPLUS ALGEBRA FOR THE MODELING OF HYBRID PETRI NETS

In this paper we are interested in a mathematical description of the class of hybrid systems, which can be modeled by hybrid Petri nets HPNs . A state space model using conventional algebra for the continuous subsystem and minplus algebra for the discrete subsystem is given. The interface between the discrete and continuous part appears in our model. This model is illustrated through an example. We introduce the concept of discrete control of HPNs.

On the hyperstability of a class of hybrid systems

Sufficient conditions of the hyperstability of a class of single-input single-output hybrid systems, composed of interconnected continuous and discrete subsystems, are given. Hyperstability is guaranteed by that of a discrete extended system which is built by incorporating samples of the continuous substrate. Asymptotic hyperstability is guaranteed by that of one discrete system, together with that of a continuous one. Both systems are related to an augmented state representation of the linear part of the overall system for all the nonlinear output-feedback time-varying actuators that satisfy generalized Popov-type inequalities.

Work and non-work coping strategies: their relation to personality, appraisal and life domain

The nature and degree of the relationship between the choice of coping strategies, personality, situational appraisals and the extent to which these relationships are domain-dependent is open. This study surveyed 330 police officers in order to answer seven specific questions : (1) Is the selection of coping strategies independent of the situational domain ? (2) Is the experience of hassles and uplifts independent of the situational domain ? (3) Is the experience of hassles independent of the experience of uplifts ? (4) Is the selection of problem-focused coping independent of the selection of emotion-focused coping ? (5) Is personality related to the selection of coping strategies ? (6) Is personality related to the reappraisal of the situational events ? (7) Does the selection of the coping strategy relate to the reappraisal of the situational event ? The findings indicate that extraversion (E) and neuroticism (N) are related to the selection of coping strategy, and that personality, domain and coping strategy make independent contributions to the final appraisal of the events. Personality, coping and situational experiences operate as discrete subsystems, with N, emotion-focused coping and hassles correlating together on the one hand, and E, problem-focused coping and uplifts correlating together on the other. This finding of two independent systems also adds support to other results in signalling to stress researchers and practitioners that they need to take account of both negative and positive aspects of the stress-coping process.

A hybrid model for intelligent control systems

Hybrid continuous-time and discrete-event system models are developed for applications to intelligent robot and autonomous control systems. Certain general properties, including the interface structure between the discrete event part and the continuous part of hybrid systems, are studied. Petri nets are proposed as the model for the discrete event sub-system (DES), and state equations with a set of binary parameters as the model for the continuous time sub-system (CTS) in a hybrid system. The quantized CTS is formulated in prime event structures, which can also be modeled by a condition/event Petri net. Therefore, a complete hybrid system can be fit into an extended Petri net formalism, which provides a unified framework for hybrid system description. The validity of the proposed model is demonstrated by modeling a two-tank system.

Finite-Mode Bond-Graph Model Of A Resonant Silicon-Beam Force Sensor

In this paper a systematic approach, based on bond graphs, is presented for modelling micro–electromechanical transduccrs, comprising distributed as well as discrete or lumped subsystems. The bond-...

Psychobiological evidence for the distinction between episodic and semantic memory

The evidence for discrete neurobiological mechanisms that underlie episodic and semantic memory is reviewed. Published data from three separate lines of research are considered: studies of human amnesic patients, psychopharmacological studies of normal human subjects, and studies of working and reference memory in rodents, a distinction that is arguably analogous to the episodic/semantic dichotomy. It is concluded that the available evidence does not indicate that episodic and semantic memory are mediated by discrete neural subsystems. An alternative model of human memory is discussed, based on the concept of parallel distributed processing.

The relationship of the internal security system to group level organization in Miller's living systems theory

It has been suggested that a 20th subsystem, the internal security subsystem, should be added to Miller's 19 matter-energy and information processes that are critical to living systems (Bosserman, 1982). This subsystem protects all levels of living systems from error and disruption resulting from internal and external sources. Yet many characteristics of the proposed security subsystem already are found in existing ones, that is, the reproducer, channel and net, and distributor. Therefore, a discrete internal security subsystem is not justified. There are, however, dormant aspects of the security system that are not described within the existing taxonomy that perhaps best fit as a mirror system across the organizational levels.

Intelligence for miniature robots

It seems clear that small robots which take advantage of recent reductions in packaging size and costs of microelectronics can potentially be very useful; even more so if similar savings could be achieved in the actuation and power supply areas. Typically, the computational power required in a robotic system that connects perception to action is enormous, but if the organization of the sensors, actuators and computing elements is carefully laid out, the actual silicon area required for the intelligence system becomes quite small. A viable avenue of pursuit, then, is to aim towards scaling down the rest of the subsystems in a robot to the same scale as the control system, integrating motors, sensors, computation and power supplies onto a single piece of silicon; the advantages being mass productibility, lower costs and the avoidance of the usual connector problems encountered in combining discrete subsystems. By rethinking implementation strategies with this new form of robotic technology (i.e., the application of many very small robots), it may be possible to solve many problems more cost effectively, albeit in novel ways. As the completely integrated robot faces many technology hurdles, it seems necessary to focus on just one or two of the problem areas at a time. It turns out that many of the cost-saving benefits still accrue at small, but macroscopic scales. This paper describes an exercise of building a complete system, aimed at being as small as possible, but using off the shelf components exclusively. The result is an autonomous mobile robot slightly larger than one cubic inch, which incorporates sensing, actuation, onboard computation and on-board power supplies. Nicknamed Squirt, this robot acts as a ‘bug’, hiding in dark corners and venturing out in the direction of last heard noises, only moving after the noises are long gone.

Computer Aided Engineering and Shock Analysis for the Foundation of a Modularized Vertical Launching System

ABSTRACTThe major objective of this paper is to describe a computer aided methodology for structural integration and analysis. Using the example of recent work in the installation of modular gun and vertical launch missile systems in warships, the reader is guided through a typical case of computer aided structural design and shock analysis, how the models are defined and tested, how the models are modified in order to be compatible with computer capacity, how structural elements are selected to simplify computations, and finally how the results of these operations are used to define the final product before construction and installation.With the maturation of the computer aided process as applied to the whole ship product, more attention must be focused on improving the individual elements of computer aided design (CAD), computer aided engineering (CAE) and computer aided manufacturing (CAM) and the integration of these processes and their products through computer integrated manufacturing (CIM).The application of the CAE techniques described herein to large maritime systems such as combatant, auxiliary and support, and commercial ships and to other large structures such as semisubmersible and fixed platforms is powerful and highly in demand. There is now a means to optimize large structural systems in terms of their discrete subsystems and components and harmonize the entire design while providing the proper design integrity at each successive level of detail.

Modernization of the UK Army Fixed Telecommunication System

The Army Fixed Telecommunication System (AFTS) in the UK has traditionally comprised a number of diverse and discrete subsystems, each tailored to their roles in peace, transition to war and conventional and nuclear war. The subsystems include unclassified voice carried on the Army Telephone Network (ATN), and a mix of classified and unclassified telegraph, telex, facsimile and data systems. Complementary military communications are provided by VHF and HF ratio systems. This paper describes Project Fastnet, the phased modernization of the existing AFTS to provide a modern integrated digital network (IDN) to support the emerging requirements of information technology and office automation.

Optimal control of system with continuous and discrete state variables

Abstract An optimization problem for a system composed of continuous and discrete subsystems is considered. The discrete subsystem is introduced to express a combinatorial constraint in conventional control problems. The objective, the state equation and the constraint are assumed linear. The problem is formulated as a mixed-integer linear program with a staircase structure. A feasible decomposition method is developed for obtaining a suboptimal solution to the problem. In applications to an optimal energy control and planning problem for a large-scale production plant, our method uses less computing time than the non-decomposition method.

Optimal Control of a Coupled System Composed of Continuous and Discrete Subsystems

This paper deals with an optimization problem for a system composed of continuous and discrete subsystems. The discrete subsystem is introduced to express a combinatorial constraint in conventional control problems. The objective, the state equation and the constraint are assumed linear. Then, the problem is formulated as a mixed-integer linear program with staircase structure. A feasible decomposition method is developed for obtaining a suboptimal solution of the problem. In applications to an optimal energy control and planning problem of a large-scale production Plant, the method gives a solution satisfying the condition that the number of switching times for the boiler operation is as small as possible.

Modeling Hydroclimatic Processes in Large Watersheds

Spatial and temporal differences in the processes that transform precipitation into runoff are a common source of error in watershed models. For large watersheds, spatial disaggregation of the drainage area can improve efforts to model the precipitation-runoff relationship when the model employs physically explainable variables to represent horizontal and vertical variations in moisture fluxes and storages. The paper presents the conceptual structure of a hydroclimatic model that simulates the runoff process as four functionally discrete subsystems linked in series. Moisture inputs are routed through each subsystem employing environmentally dictated rules and readily available data. Dividing the basin into homogeneous subunits addresses the problem of horizontal heterogeneity. Residence times for two groundwater storage subsystems are calculated by an optimization algorithm included in the model. Modeled hydroclimatic characteristics for the Deschutes River Basin in Oregon illustrate the ability of the model to reveal important spatial and temporal differences in the runoff process. Sectors representing 20 percent of the basin area contribute 57 percent of modeled ground-water recharge and 61 percent of total modeled runoff for the watershed, but some other sectors make a relatively small quantitative contribution to basin runoff. Moisture exchange processes in the basin display explicit seasonal characteristics that explain the surprisingly large proportion of annual precipitation allocated to groundwater recharge and the dampening of the seasonal moisture input by the groundwater storages. This knowledge of the basin runoff process provides a rational basis for formulating water management strategies for the watershed.

Modelling amnesia and the study of memory in animals

In the last few years, neurobiological research on memory in animals has been evolving from a preoccupation with the modelling of human global amnesia. Studies of the cerebral localization and logical structure of memory in primates are still guided by the prospect of finding a valid model of the clinical syndrome, but such attempts are complicated by new discoveries which have revealed discrete subsystems of primate memory. Work with rats is also moving away from all-encompassing models towards a concern for such issues as recovery of function and the analysis of neurotoxin-induced lesions of brain regions only indirectly related to human amnesia. There is now a broad measure of agreement about the types of memory task that are or are not impaired by diecephalic and/or medical temporal lobe damage in animals 1,2. However, a satisfactory classification of the underlying types of information processing in these impaired and unimpaired memory tasks remains elusive. The search for new directions in current research reflects the fact that separating out the superficially similar predictions of rival hypotheses is proving difficult.