International Journal of Engineering
Volume:14 Issue: 2, May 2001

Reactive power dispatch for voltage profile modification has been of interest Abstract to powerr utilities. Usually local bus voltages can be altered by changing generator voltages, reactive shunts, ULTC transformers and SVCs. Determination of optimum values for control parameters, however, is not simple for modern power system networks. Heuristic and rather intelligent algorithms have to be sought. In this paper a new algorithm is proposed that is based on a var iant of a genetic algorithm combined with simulated annealing updates. In this algorithm a fuzzy multi-objective approach is used for the fitness function of the genetic algorithm. This fuzzy multi-objective function can efficiently modify the voltage profile in order to minimize transmission lines losses, thus reducing the operating costs. The reason for such a combination is to utilize the best characteristics of each method and overcome their deficiencies. The proposed algorithm is much faster than the classical genetic algorithm and can be easily integrated into existing power utilities software. The proposed algorithm is tested on an actual system model of 1284 buses, 799 lines, 1175 fixed and ULTC transformers, 86 generators, 181 controllable shunts and 425 loads.

The use of different optical-fiber sensors for weighing measurements is Abstract described. By using three different mechanical stressing mechanisms, the operation of the fiber-to-fiber transducer systems are tested and the results are presented. Parameters such as sensitivity, hysteresis, resolution, and dynamic range are measured. A comparison of the results has shown that the sensor system made with a cantilever steel beam offers a better overall performance. It shows a sensitivity of about 4.8 mV/gm, a maximum hysteresis of 4%, and has a resolution of 0.2 gm for a dynamic range of about 140 gm. The reported systems offer simplicity in design and can be implemented for force/pressure measurements.

In CDMA (Code - Division Multiple - Access) systems multi - user accessing of a channel is possible. Under the assumptions of Optimum multi - user and decorrelating detector in CDMA systems. By using signals with zero and / or identical cross correlations, a simple and expandable decorrelating detector with optimum efficiency which can be easily implemented are proposed. Constructing these signals is accomplished by encoding of the data stream by a member of orthogonal code which is then multiplied by a special signature sequences.

The problem of optimal economic operation of hydrothermal electric power systems is solved using powerful continuation method. While in conventional approach, fixed generation voltages are used to avoid convergence problems, in the proposed algorithm, they are treated as variables so that better solutions can be obtained. The algorithm is tested for a typical 5-bus and 17-bus New Zealand networks. Its capabilities and promising results are assessed.

(Singular systems have been studied extensively during the last two decades due Abstract to their many practical applications. Such systems possess numerous properties not shared by the well-known state variable systems. This paper considers the linear tracking problem for the continuous-time singular systems. The Hamilton-Jacobi theory is used in order to compute the optimal control and associated tr ajectory. Two methods are presented for solving these trajectories. The first method uses the concept of the Drazin inverse, and the second involves the derivation and solution of a Riccati equation. Similar to the linear regulator problem, necessary and sufficient conditions for existence and uniqueness of a solution are stated.

In this paper we study two echelon multi-server tandom queueing systems where customers arrive according to a poisson process with two different rates. The service rates at both echelons are independent of each other. The service times of customers is assumed to be completed in two stages. The service times at each stage are exponentially distributed. At the first stage, the customers may balk (i.e. reject to join the waiting line) when all servers are busy. The higher echelon has a limited buffer space. The steady state queue size distribution has been obtained for both stages. We investigate the properties of a Hessenberg mat rix which is required for the complete specification of the generating function for ready use.

The phenomenon of capillary condensation is studied through the weight change of condensed phase in an internally wetted porous pd catalyst pellet during the course of exothermic reacation of cyclohexane hydrogenation in a thermogravimetric analyzer (TGA). The direct measurement of condensed phase indicates that evaporation of condensed phase is confined to the macropores of catalyst pellet at the lower limit of reaction rate. Phase transition from lower to upper limit reaction rate associates with the sharp temperature rise in the catalyst pellet. A substant ial fract ion of pellet pores volume opens in the phase t ransit ion and evaporation of condensed phase extends to the micropores of catalyst pellet. The TGA studies shows the reacation rate multiplicities is the result of condensation - evaporation hsteresis associated with the internally wetted catalyst pellet.

The calculation of the load carrying capacity of variable thickness circular plates subjected to arbitrary rotational symmetric loading is presented. The analysis considers plate materials that obey either the square or the Tresca yield criterion. By using upper and lower bound theorems of limit analysis, corresponding estimations for the load carrying capacity of the plate are obtained. It is shown that these two bounds are identical. Therefore, the obtained solution would represent the exact amount of the load carrying capacity of the variable thickness circular plate. Finally, in order to obtain solutions for some special cases, plates having step changes in thickness and those with linear thickness variation are considered and corresponding results are illustrated.

In this paper the development of a single set of design parameters of the sizing of the tidally affected detention pond system was analyzed and tested. The approach uses critical duration single storm event of specified return period, together with a single harmonic tide. The design flood level is then the aggregate of the levels obtained using the system model with the four phase lags between the high tide and peak inflow. The inequality resulting between the return period of the storm and the resulting aggregate level is adjusted using a modeling factor. The modeling factor is seen to vary significantly with the level of the offsite sewer and this variation is quantified.

In this paper a parametric study was undertaken to quantify the sensitivity Abstract to a wide range of coastal detention pond systems dealing with tidal influence to store surface flood water so as to produce general guidance on the importance of the catchment and pond variables. In this process a specified pond design return period was selected for which the system was to be designed. The pond volume was determined as the fundamental design criterion in the statistical analysis for all the different modeling combinations. The results showed that over the range of different variables for the pond volume identification, the most significant variables were the catchment area and the pond location, as incorporated in the analysis via the size of tidal amplitudes adopted. The sensitivity of the system to the outfall sewer level and its realistic position relative to the sea level was investigated.In this paper a parametric study was undertaken to quantify the sensitivity to a wide range of coastal detention pond systems dealing with tidal influence to store surface flood water so as to produce general guidance on the importance of the catchment and pond variables. In this process a specified pond design return period was selected for which the system was to be designed. The pond volume was determined as the fundamental design criterion in the statistical analysis for all the different modeling combinations. The results showed that over the range of different variables for the pond volume identification, the most significant variables were the catchment area and the pond location, as incorporated in the analysis via the size of tidal amplitudes adopted. The sensitivity of the system to the outfall sewer level and its realistic position relative to the sea level was investigated.