JOURNAL OF SCHOOL OF ENGINEERING
Year:2001 | Volume:13 | Issue:1|Papers Count:7

Security in stressed power systems is seriously affected by voltage collapse phenomena. This paper proposes a new algorithm for determining the voltage security margin. The algorithm is based on the perturbation method and has very high computation efficiency. Therefore, it can be used for on line voltage evaluation. The proposed approach has been validated using IEEE 14, 30 and 57 buses systems.

In this paper, the new modal series method is extended to calculate the closed form zero input response of the nonlinear systems which their linear models have multiple eigenvalues. Also a method, based on modal series, is offered to calculate zero state response of nonlinear systems. These methods give approximate solutions that are more suitable to explain nonlinear systems behavior based on the concepts of the linear systems analysis.  

One of the problems encountered during machining of flexible parts such as: blades, housing and frames is self-excited chatter vibrations. These vibrations are due to the interaction of the tool and the flexible part which can deteriorate dimensional accuracy and surface finish of the part. In this research milling operations of flexible parts are simulated by a comprehensive model consisting of solid modeler of milling operation, dynamic modeler of cutting forces and FEM modeler of tool spindle and part. Amplitude of chatter vibrations are controlled within acceptable limits by improving cutting conditions where metal removal rate approaches to attainable maximum values.

In metal machining, a fluid is required to both lubricate and cool the tool and work piece. In many operations the fluid used is an oil water emulsion. During use it can not be discharged to most sewers (because of high TOD). RO and UF offer an alternate method for treating this effluent. This paper describes the type of laboratory test for the treatment of this effluent by RO and UF. These tests yield information on solute rejection, permeate flux, osmotic and applied pressure and membrane fouling. In UF process, above degree of concentration 2, the gel layer was observed, and flux of permeate rested constant. Under this value, flux of permeate decreases. In RO processes, flux of permeate and solute rejection increased with applied pressure.

In this paper a new design for an ATM cell switch fabric with 4 input and 4 output ports has been considered. The switch fabric has a non-blocking internal structure and is a hybrid input/ output buffered switch. A novel routing algorithm has been proposed and implemented for routing and relaying the waiting cells in input buffers. The proposed cell switch fabric has been modeled and simulated with VHDL at a behavioral level and its performance regarding cell loss rate, throughput and mean waiting time has been evaluated and compared with those of similar switches.

Little research has been carried out to characterize Iranian desert solis from highway Engineering point of view sofar. In such areas conventional paving materials are sometimes difficult and costly to provide. The research presented herein include studying the geotechnical properties of four soils sampled from eastern fringes of Kavir-e Namak, and determining their suitability as paving materials once stabilized with lime and cement. Selection and sampling of soils were accomplished so that they represent the general characteristics of soils in the area. Standard techniques were used to determine the physico-chemical and mineralogical properties of soils. The influence of lime-cement content and curing period on the properties of lime-cement-soil mixtures were investigated. The results show that loess soils are amenable to stabilization with lime and cement while sandy soils are amenable to stabilization with cement, and both might be used as paving materials. But, saline soils containing high proportions of salts do not respond to stabilization.