Atsunobu Ichikawa

Synthesis of optimal processing system by an integrated approach

Abstract A general synthesis problem is defined as that of determining an optimal system structure by extracting it from an enlarged system structure generated by splitting streams into alternative routes. When the optimized splitting ratio is close to 0 or 1, one of the alternative streams can be eliminated to give the optimal synthesis. Boxs Complex method, is used to solve an actual example amenable to the integrated approach.

Optimal synthesis of heat exchange systems Necessary conditions for minimum heat transfer area and their application to systems synthesis

Abstract Necessary conditions for the optimal structure of a heat exchange system are discussed with the minimum heat transfer area employed as acriterionto express efficiency of the system. On the basis of the necessary conditions obtained, an algorithm to synthesize heat exchange systems with auxiliary heating and cooling equipment is proposed. an application to a practical heat exchange system show that the algorithm provides far more efficient than that which has been conventionally used.

Synthesis of optimal heat exchange systems—an approach by the optimal assingment problem in linear programming

Abstract A systematic way of synthesizing an optimal heat exchange system is proposed. The method consists in formulating the problem as an optimal assignment problem in linear programming, and of carrying out the optimal design of the synthesized system by the Complex method.

On structural conditions for weak persistency and semilinearity of Petri nets

Abstract A necessary and sufficient condition for a Petri net to be weakly persistent for every initial marking is obtained. Moreover, a necessary and sufficient condition for reachability is obtainable for this class of Petri nets. As a sufficient condition for a Petri net to have a semilinear reachability set the notion of sinklessness has been proposed, where a marked Petri net is said to be sinkless if the total number of tokens in each minimal circuit is not decreased to 0 by firing transitions. We show that the reachability set is semilinear if the total number of times that sinklessness is violated is finite during each firing, and define a new subclass of Petri nets which have this property for every initial marking.

Interactive solution to multiple criteria problems in chemical process design: An approach by pairwise comparison

Abstract A process design problem is considered as a multiobjective problem that is characterized by conflicting objectives such as economics, operability, and so on. A method developed for solving multiobjective problems in man-machine interactive mode has been extensively applied to the basic process design of chemical process systems. AS an illustrative example, an optimal design of a simple, yet practical, chemical process system has been taken up to show the practical usefulness of the present method.

Timing information in transient behavior of neuropopulations

A computational model of neuronal populations based on neurophysiological data is presented. The neuronal population consists of model neurons that simulate electrochemical processes in real neurons. Input and output of the population are defined in terms of the stochastic behavior of the single neurons. Analysis of the populational behavior shows that neuronal populations can approximately function as delay elements that transform step input to step output, and the delay intervals can specify timing information in the several-millisecond range, which is essential to high speed parallel computation. An example network composed of neuronal populations is simulated to show how the timing information can serve to achieve parallel processing in neural networks. >

Process synthesis by task assignment

Abstract An approach by task assignment is presented to determine processing system structures in chemical process design. For given design conditions of major subsystems, which were specified by the results of basic or applied research, a basic flowsheet is determined by task assignments on energy recovery and material flow transportation. An illustrative example shows the usefulness of the present method.

Optimal design of linear control systems by an interactive optimization method

Abstract When designing linear control systems, one of the most difficult problems is that the designer almost has no theoretical basis for the determination of proper parameters in order to obtain a system with desired specifications. Poles and directions of eigenvectors in the pole assignment method or weighting matrices of the quadratic criterion function in the optimal regulator method are such parameters. The designer has to determine them by trial-and-error using computer simulation. The purpose of this paper is to propose an approach to helping determine proper parameters in linear control system design by the state space methods. In the case where the desired specifications are not given explicitly, the approach applies an interactive optimization method called the Interactive Simplex method to search the most suitable parameters directly in the parameter space. But, if the specifications are given explicitly, the design problem can be formulated as a multiobjective optimization problem. In this case, weights which indicate relative importance of different specifications are introduced and the Interactive Simplex method is applied in the weight space to indirectly find the most appropriate parameters. The approach is implemented as part of a CAD system. The designer has only to make pairwise comparisons of response curves which are shown on a graphics display terminal in order to obtain the most preferred control system. Two illustrative examples are demonstrated to indicate the efficiency of the approach.

A rational approach to process synthesis: An extensive use of task assignment concept

Abstract The concept of task assignment for process synthesis at the preliminary stage of process design has been extensively applied to generate more complete process flow diagrams. Mathematical description of process synthesis at the process design stage has been made and basic strategies for achieving the present goal have been proposed. A practical example is taken up for illustration.

Brief paper: An interactive system for supporting multiobjective decision making

The purpose of this paper is to develop an interactive system for supporting the decision making process under multiple objectives and to empirically evaluate its performance. An interactive algorithm underlying the system is proposed with emphasis on the psychological aspects of the decision maker (DM). A choice process model is developed, based on pairwise comparison judgments of alternatives, because the judgments are basic and easy for a DM. A corresponding interactive algorithm is implemented and compared with other existing algorithms. Two kinds of comparative experiments, numerical and subject experiments, are conducted to verify the validity of the choice model as well as the practical effectiveness and the convergence of the algorithm.