摘要:

AbstractPower supply quality improvement is a very real goal for utilities throughout the world because of the expanding diffusion of sensitive (electronic) loads. Among the various types of phenomena affecting voltage quality (Le., surges, harmonics, spikes, etc.) a great amount of concern is given to the so-called vol tage dips or voltage sags. The main source of such a dip or sag is connected wi th the M. V. distribution line's transient, quasitransient and permanent short circuits.Once a short circuit occurs on a distribution net, a voltage dip appears on all the lines departing from the same bus of the faulted line. Because of this fact, a significant degree of relief from the dip phenomena, or, in other words, a significant improvement in the powersupply quality, can be achieved if the fault current is limited by a proper device (a faultcurrent limiter (FCL)).The design of a FCL device devoted to vol tagedip limitation has less stringent requirements, as far as reliabili ty and operation quickness are concerned, than does the design of the equivalent device which has as a target the reduction of the circuit breakers' rated capacity. Very attractive and rather simple solutions are possible using standard, electronically controllable power devices such as thyristors or GTOs.In the present paper, some possible circuits consisting in series-resonant and nonresonant impedance and controlled by static valves are proposed. computer modelling and simulations of the above circuits and their static and dynamic performances are reported, compared and discussed.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760243

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractBoth reliability-based structural design and multi-objective optimization techniques have received extensive attention. The proposed approach, using multi-objective optimization strategies, aims to deal with reliability-based. structural design optimization problems with multi-pie design goals. Among reliability analysis, a transformation method based on the advanced firsl order second moment (AFOSM) method is used to evaluate the failure probability of single failure mode, and the Cornell’s upper bound is used to estimate system failure probability with multifailure mode. In multi-objective optimization, the promising surrogate worth trade-off method (SWT) is used. Through the numerical solution of two design examples. it is concluded that the multi-objective 0plimization approach, which improvc.~ the decision-making capability of designers or decision makers and it is an effective design tool for engineers in the solution of multi-objective problems with uncertainties.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760244

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractAn analytical study of flow in the impact region of two jets is used to develop a mathematical model that yields data for the air curtain performance. In this model”theory for the pressure difference created by an air curtain in a rectangular duct is applied to two turbulent-plane air streams injected from two opposite walls. The theory enables us to establish the quantitative influence of the jet properties and duct geometry on the pressure difference and to predict flow conditions in both inlinilies. The flows in both inlinities are considered together with the method applied for generating the streams. Air ulled to fonn the jet ill taken from an external source or is drawn In from one or both side. of the air curtain. The theory i. also extended to an air curtain fanned by a single jet. Some computed and experimental re.ults are presented.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760245

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThe conventional penalty function finite element model and balancing diffusivity upwind scheme are adopted to simulate shear flows over a surface-mounted obstacle within flow domain. Experimental data and flow visualization made available by previous investigators are used to assess applicability of the present numerical scheme. With a nonuniform grid system, both schemes have been shown to eliminate numerical oscillations that are generated from nonlinear advection. The computational results reveal that strength of recirculating zone behind the wall obstacle is in proportion to width/height ratio of the obstacle, and the pressure loss coefficient increllses rapidly as the ratio is increased.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760246

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractThis paper describes the application of the HEClF conceptual model for flood-flow forecllllting and warning to the Venetikos river basin in Northwestern Greece, a region suffering from frequent and hazardous Bash floods. The extremely uneven and nonuniform spatial rainfall distribution in the study region forced the modification of the initial lumped version of the model and its application in a semidistributed manner, Such as by dividing the entire basin into three subbasins with different geomorphology and spatial rainfall patterns. The model is shown to perform better in the semidistributed than in the lumped mode, thus juatifying the modifications adopted and supporting application of the flood-flow forecasting model in a fully distributed manner on a 4x4 km2grid network combined with omite and remotely .ensed radar rainfall input information. Preliminary results from current research on thi. integrated application suggest that the model’s forecasting performance may be further improved.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760247

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

AbstractWe use simulation to Solve the problems related to the design And the management of Treatment Plants; in effect, in this work we Analyzed a system for incineration of Hospital Solid WlUIte using a simulator to define correctly the optimal mix of special waste. This management support is a very powerfu1l assistant manager for defining operating parameters to attain economical And technical targets.

ISSN:0228-6203    

DOI:10.1080/02286203.1995.11760248

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor