A codesign approach for distributed systems

Distributed systems have become prevalent in response to the rapidly expanding Internet's demands. Their design presents new challenges because it involves the interaction of hardware and software. Continual marketplace innovation drives computing toward heterogeneity in both hardware and software and generates a complexity that goes beyond the earlier codesign approaches, which were developed for more homogeneous systems executing in non-distributed environments. Codesign of heterogeneous systems requires the support of a powerful modeling and simulation environment because analysis alone cannot deal with all the challenges such complex systems pose. We believe that modeling and simulation, using the discrete-event system specification modeling and simulation framework, are the most suitable vehicles to study the complexities associated with developing distributed-object computing systems     

Computer Simulation of a Living Cell: Metabolic Control System Experiments

Abstract

This paper reports on some interesting experiments performed on a simulated model of a living cell. The basic model is that of Weinberg [35] and the underlying techniques employed are described by Zeigler and Weinberg [41]. The cell was subjected to step changes in its nutrient environment.     

Model continuity in the design of dynamic distributed real-time systems

Model continuity refers to the ability to transition as much as possible a model specification through the stages of a development process. In this paper, the authors show how a modeling and simulation environment, based on the discrete event system specification formalism, can support model continuity in the design of dynamic distributed real-time systems. In designing such systems, the authors restrict such continuity to the models that implement the system's real-time control and dynamic reconfiguration. The proposed methodology supports systematic modeling of dynamic systems and adopts simulation-based tests for distributed real-time software. Model continuity is emphasized during the entire process of software development $the control models of a dynamic distributed real-time system can be designed, analyzed, and tested by simulation methods, and then smoothly transitioned from simulation to distributed execution. A dynamic team formation distributed robotic system is presented as an example to show how model continuity methodology effectively manages the complexity of developing and testing the control software for this system.     

A note on series parallel irreducibility

A new criterion for series-parallel irreducibility is given which makes no reference to underlying semigroups but involves only series-parallel connection operations.Research was sponsored by National Institutes of Health, Grant No. GM-12236-03; Office of Naval Research, Contract No. N00014-67-A-0181-011; and U.S. Army Research Office (Durham), Grant No. DA-31-124-ARO-D-483.     

DEVS-BASED INTELLIGENT CONTROL: SPACE-ADAPTED MIXING SYSTEM EXAMPLE

This paper reviews a methodology for event-based intelligent control employing the DEVS (discrete event system specification) formalism. In this control paradigm, the controller expects to receive confirming sensor responses to its control commands within definite time windows determined by its DEVS model of the system under control. We apply the DEVS-based intelligent control paradigm to a space-adapted mixing system. The event-based approach is compared with conventional sequential control methods.     

Designing fuzzy logic controllers using a multiresolutional searchparadigm

A multiresolutional search paradigm is employed to design optimal fuzzy logic controllers in a variable structure simulation environment. The initial search space is evaluated with a coarse resolution and some of the subspaces are selected as candidate regions for global optimum. New optimization processes are then created to investigate the candidate search spaces in detail, a process which continues until a solution is found. This search paradigm was implemented using hierarchical distributed genetic algorithms (HDGAs)-search agents solving different degrees of abstracted problems. Creation/destruction of agents is executed dynamically during the operation based on their performance. In the application to fuzzy systems, the HDGA investigates design alternatives such as different types of membership functions and the number of the fuzzy labels, as well as their optimal parameter settings, all at the same time. This paradigm is demonstrated with an application to the design of a fuzzy controller for an inverted pendulum     

Early results of AV sequential pacing on left ventricular outflow obstruction after Senning procedure

Dual chamber pacing was shown to decrease left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic cardiomyopathy 30 years ago. We report early results of AV sequential pacing from the LV apex in a patient with transposition of the great arteries who is post-Senning procedure. LVOT obstruction resulted from septal deviation and systolic anterior motion of the mitral valve. Pacing was indicated for sinus node dysfunction. AV sequential pacing with a short optimal AV interval of 60 ms demonstrated a 45% reduction in the degree of LVOT obstruction. This article suggests that LVOT obstruction after the Senning procedure can be palliated by asynchronous septal contraction induced by AV sequential pacing, even if the activation is from LV apex, and avoid or postpone surgery in selected situations.     

System-Theoretic Representation of Simulation Models

The representation of simulation models, especially those expressed in discrete event languages, by means of system-theoretic formalism is reviewed. The important concepts of decomposition, static and dynamic structure, and state variable selection are explained and their implications for the design of simulation software explored. The system-theoretic approach is compared with other approaches to model representation derived from general software development methodology. Both simulation software design and systems theory may benefit by the challenges each raises for the other.     

Canonical realization of general time systems

The canonical realization of general time systems by dynamical systems is discussed employing the notation and definitions of Takahara and Mesarovic. Previous results are extended to the case of causal, but not necessarily stationary, systems and to stationary, strongly connected systems. Conditions are provided under which a time system is guaranteed to have a canonical representation from within a class of possible realizations.     

Trigeminal deafferentation and feeding behavior patterns in the pigeon (Columba livia).

Data from a study with 11 White Carneaux pigeons show that after an aphagic period, trigeminally deafferented Ss regulated body weight at reduced levels. The deficit involved was characterized by comparing feeding patterns of deafferented and food-deprived birds with equivalent weight losses. Deafferented Ss showed disproportionate increases in meal size during the early portion of the feeding period but abnormally rapid attenuation of feeding activity in the course of the day, which led to a reduced overall level of food intake. Trigeminal input appears to influence both the size of bouts and the frequency of bout initiation. Findings are discussed in relation to the homeostatic model of intake control and within the framework of food conditioning. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)