A robust test of uncertain linear systems

In this paper, it is shown that for low-order uncertain systems, there is no need to calculate all the minimum and maximum values of the coefficients for a perturbed system which is expressed in terms of polynomials and hence no need to formulate and test all the four Kharitonov＇s polynomials. Furthermore, for higher-order systems such as n ≥ 5, the usual four Kharitonov＇s polynomials need not be tested initially for sufficient condition of perturbed systems; rather, the necessary condition can be checked before going for sufficient condition. In order to show the effectiveness of the proposed method, numerical examples are shown and computational efficiency is highlighted.     

Mathematical modelling of an aquatic ecosystem I

This paper presents a mathematicfa1 model of an aquatic ecosystem. The model differs from previous models in that it incorporates characteristics of specific phyla of phytaplankton and zooplankton, inter and intra-phyla interaction and limiting nutrient processing by decomposers.     

Minimization of interfaces and interconnections in a digital system satisfying concurrency constraints

The problem of minimizing the number of links and buses in a digital system subject to a given set of concurrency constraints among data transfers is studied. The notion of the transfer graph (TG) is introduced which depicts the data transfer paths and concurrency requirements in the system, A very simple node labelling procedure is applied on the nodes of the TG, which enables one to make a direct assignment of transfers to buses without going through any elaborate computational steps.     

The Use of Legendre Polynomial Expansions in Solving Optimal Control Problems in the Space l 2

A method for solving a class of general deterministic optimal control problems is presented here. The method consists of relating the functions involved in the problem to sequences and then converting the problem to one which deals with these sequences alone. The function-sequence correspondence is defined by representing each function by its Legendre polynomial expansion and then relating the function to the sequence of coefficients in this expansion. After this is done, the problem is converted to one in l ²; by determining the equivalents in l ²; of differentiation, inner multiplication, and multiplication.

The resulting problem in l ²; is a non-linear programming problem which consists of an infinite array of equations, inequalities, and expressions, each of which involves infinite polynomial expressions. To solve a problem of this type it must be approximated by a finite non-linear programming problem. After this is done various methods can bo used for solving the final problem.     

Modelling and simulation of combinational digital circuits using Petri nets

The P-model approach of modeling a combinational digital network using Petri nets is introduced. In this model a given logic circuit its represented by a graph With only two types of nodes, places and transitions. A logic 1 value in any line of the circuit corresponds to the presence of a so-called token, and a logic 0 corresponds to the absence of tokens, in the corresponding place of the P-model. The operation of the circuit is reflected in the execution of the P-model resulting from the firing of transitions. Several minimizing transformations in the P-model domain are discussed, which reduces the number of places and transitions by an order of magnitude. Based on this P-model representation of a logic circuit, a logic simulation algorithm is outlined. The method is faster and also simpler to implement than conventional simulation techniques.     

ON THE DESIGN OF AN ADAPTIVE CONTROLLER FOR UNCERTAIN PLANTS VIA LIAPUNOV SIGNAL SYNTHESIS METHOD

This paper presents an adaptive design approach for controlling a class of unknown nonlinear multivariable plants operating in an uncertain environment. The approach uses a “two-level” control technique, with a feedforward controller on its first-level, and a conditional feedback controller on its second-level. The procedure employs a Liapunov type signal synthesis approach. By introducing a characteristic vector, which is characteristic of the unknown plant and its environment, the design of the controller bypasses the rigid requirements of explicit identification of the plant and its environment as needed in the implementation of a controller using conventional techniques.

The applicability of this control approach is demonstrated by means of hybrid computer simulation studies which were carried out on a number of unknown plants; however, in this paper we present some simulation results for an exothermic chemical reactor.     

Design of microstrip hyperbolic line to match a complex impedance to a standard coaxial transmission line

Based on the solution of the Riccati equation, a hyperbolically tapered microstrip transmission line for matching a complex load to a standard coaxial cable is designed. An iterative procedure is used to yield the phase constant leading to an accurate design. A numerical example is considered. The result shows that a tremendous reduction in the size of matching components can be achieved if hyperbolic instead of uniform transmission lines are used. This is highly advantageous in the miniaturization of solid state circuits.     

Land use and forestry studies of Himachal Pradesh

Of late, deforestation and the resulting soil erosion, especially in the hilly regions of India, has become a matter of concern and is receiving attention at the highest official level in the country. In this context the study in the changes in forestry and land use of the Himachal Pradesh, known for its scenic beauty and forests, assumes special significance. In this study, which was undertaken as an end-to-end experiment under the National Natural Resources Management System (NNRMS) programme in India, the land-use changes in the state were initially analysed on the basis of available topographical maps. Subsequently, the changes in the forest cover was evaluated with the help of LANDSAT data of 1973, 1977 and 1980.     

n jobs and m machines job-shop problems with sequence-dependent set-up times

This paper presents a mathematical model based on the branch-and-bound technique to solve static scheduling problems involving n jobs and m machines where the objective is to minimize the cost of setting up the machines. Set-up times are sequence dependent and not included in processing times. There is a finite non-zero cost associated with setting the machines which is different for each machine. It is further assumed that the routing may be different for different jobs and a job may return to a machine more than once.