[en] 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 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

[en] This paper presents a new filtering approach based on fuzzy-logic which has high performance in mixed noise environments. This filter is mainly based on the idea that each pixel is not allowed to be uniformly fired by each of the fuzzy rules. In the proposed filtering algorithm, the rule membership functions are tuned iteratively in order to preserve the image edges. Several test experiments were performed in order to high t the merit of the proposed method. The results are very promising and indicating the high performance of the proposed filter in image restoration compared with those of the filters which have been recently cited in the image processing literature

[en] This paper presents a theoretical derivation and computer simulation of an optimal speed controller for a barrelhouse dc motor using feedback from a linear model running in parallel with the inverter-fed model. The intent of the feedback from the linear model is to eliminate torque ripples from the inverter drive. A nonlinear model of such a motor, transformed into a linear model by a local dipheomorphism (defined in section 2) and a new model is introduced in order to eliminate the undesirable effects of the inverter harmonics

[en] The study of mechanical behavior of the structural steel S 400 under quasi-static and dynamic loading has been the subject of this investigation. In order to obtain different stress-triaxiality conditions the specimens were notched with 1, 1.5, 2 and 3.5 mm notch radius. The results of fractography show as the velocity of tension increases, ductility reduces and a ductile-brittle transition occurs under certain stress triaxiality or strain rates. The observation of load-time history diagrams and SEM micrographs show that, as far as the fracture is ductile, any increase in velocity leads to the reduction of fracture load which is presumed to ve due to reduction of plastic deformation. In brittle fracture, however, the velocity increase results in increase in fracture load which is thought to be due to micro-cracks formed at different level near to the fracture surface of specimens, the so called crack shielding and crack branching at high deformation velocities. Notch radius also proved to be highly effective on fracture mechanism which is due to notch strengthening. The change in grain size of some of the specimens shows that the ductile to brittle transition in fracture mechanism can be postponed by a suitable heat-treatment scheme up to a certain strain rate

[en] This paper reports a study on a single server queue with bulk arrival and bulk service patterns where in the incoming traffic depends on the state of the server which may be in operating or breakdown state. The repair of the breakdown server is performed in two phases. The operating duration of server, repair duration of both phases of repairing as well as job's inter-arrival times and service times are exponentially distributed. By using generating function approach, the transient analysis for the queue size distribution has been carried out. For steady state, the stability condition and average queue length for various states have been derived. By taking a numerical illustration, the effect of various parameters on the average queue length has been depicted graphically

[en] An unsteady two-dimensional finite-volume solver was developed based on Van Leer's flux splitting algorithm in conjunction with ^Monotonic Upstream Scheme for Conservation Laws^limiters to improve the order of accuracy and the two-layer Baldwin-Lomax turbulence model was also implemented. Two test cases were prepared to validate the solver. The computed results were compared with the experimental data and a good agreement validated the solver. Finally, the solver was used for the flow through a multi-blade stage of an axial compressor in its off-design condition. The computed results showed a rotating stall-like instability with a periodic behavior. To investigate the flow properties during the instability condition, the flow pattern, vortex properties and the axial velocity were studied. It was concluded that the instability vortices in the multi-blade cascade do not have the same generation history of the separated vortices over a single body

[en] Application of Compressed Natural Gas in diesel engines has always been important, especially in the field of automotive engineering. This is due to easy accessibility, better mixing quality and good combustion characteristics of the Compressed Natural Gas fuel. In this study the application of Compressed Natural Gas fuel along with diesel oil in a heavy duty direct-injection automotive diesel engine is experimentally investigated. In order to convert a diesel engine into a diesel-gas one, the so called ^mixed diesel-gas^approach has been used and for this purpose a carbureted Compressed Natural Gas fuel system has been designed and manufactured. For controlling quantity of Compressed Natural Gas, the gas valve is linked to the diesel fuel injection system by means of a set of rods. Then, the dual-fuel system is adjusted so that, at full load conditions, the quantity of diesel fuel is reduced to 20% and 80% of its equivalent energy is substituted by Compressed Natural Gas fuel. Also injection pressure of pilot jet is increased by 11.4%. Performance and emission tests are conducted under variation of load and speed on both diesel and diesel-gas engines. Results show that, with equal power and torque, the diesel-gas engine has the potential to improve overall engine performance and emission. For example, at rated power and speed, fuel economy increases by 5.48%, the amount of smoke decreases by 78%, amount of CO decreases by 64.3% and mean exhaust gas temperature decreases by 6.4%

[en] The use of different optical-fiber sensors for weighing measurements is 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 a 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

[en] Packed bed units generally, represent the most suitable storage units for air heating solar systems. In these systems the storage units receives the heat form the collector during the collection period and discharges the heat building at the retrieval process. A method for sizing of packed bed storage in an air heating system is represented. The design is based on the K-S curves, which have been generated for the storage used in the C SU solar House II through simulation. The complete simple solar heating system is simulated numerically during both the heating and retrieval processes. The simulation, which utilizes the hourly meteorological data, takes into account consideration of the principle parameters such as pressure drop across the bed, particle diameter, and mean void age. The results are compared with the reported data from a real size of storage and also with the criteria of f-chart recommendation

[en] Signal optimization is affected during radio links between a transmitter and a receiver located in adjacent material media with differing optical densities. The Optimization is carried out via the automated control theory method. The radio signal obtained after the optimization is coordinated with the two media's electrical characteristics simultaneously; and this enables low power and small antenna of the transmitter, on the one hand, and low sensitivity of the receiver, on the other