AMIRKABIR
Year:2000 | Volume:11 | Issue:44|Papers Count:16

To investigate the aerodynamic characteristics of the slender bodies with non-circular cross sections, two wing-body combinations having identical cross-section areas and lengths, were tested in a wind tunnel at high subsonic, tran-sonic, and supersonic speeds. The results obtained by the tests have pared with the results of the previous written code. Although there are some reasonable differences between them, the code is strong enough to use as a suitable reference for determination of aerodynamic coefficients of these bodies.

In modern surveillance systems, implementing of advanced and effective tracking algorithms are unavoidable because of the presence of the factors such as utilizing advanced sensors (with increasing types and varieties of measurements), hardware constraint in satisfying processing needs, restricted operational environments, efficient electronic countermeasures (ECM), and complex threat scenarios; the algorithms which have efficient performance subject to the available processing sources. In current situation, necessity of dim target tracking in presence of excessive clutter or false alarm measurements and also tracking of closely spaced or crossing targets need special attention. In this paper several feasible, adaptable to different applications and efficient algorithms are presented, and appropriate to airborne target tracking has been simulated.

Power system restoration is a complicated combinatorial problem. Hence, majority of rendered ideas and methods try to reduce the number of combinations required to be searched. In this paper, using the graph theory, a method has been proposed for power system restoration. In the proposed method, firstly important constraints such as voltage, frequency and transmission lines loading have been considered and secondly, the graph theory based on giving priority to transmission lines in terms of higher voltage level, higher active capacity and  lower capacitance, has been utilized in order to reduce number of combinations required to be searched. The proposed method has been tested and proved to be a success on the IEEE 14 bus system and the relevant outcomes have been shown.

The aim of this work is to study the properties of fabrics produced from air-jet spinning system and comparing with the same fabrics produced from ring spinining system. For this purpose, 34 Tex (50/50) cotton /polyester blended yarns are produced with these spinning systems and provided fabric samples with three stitch length on a single jersey knitting machine. Fabric dimentional stabilities, thickness, spirality and selvedge curling in wale direction are evaluated in different relaxation states. The results showed that the fabrics produced from air-jet spun yarns have lower dimentional stabilities and spirality and higher  thickness and curling the same fabrics procued from ring spun yarns. It was also found that the relaxaion treatments increases dimensional stabilities, thickness and spirality but decrease fabric selvedge curling. Fabric thickness and spirality are increased with the increase of stitch length but selvedge curling is decrease.

In this paper, the model suggested by Duncan for simulation of linear induction motors, is modified by means of finite element method. The modified model covers the special phenomena in linear motors such as transverse edge effect, longitudinal end effect, and saturation of back iron. In the proposed model, first, the level of saturation is computed by simple equations and an iterative method. Then, using finite element method, the equivalent circuit parameters are obtained. Finally, the end effect is taken into consideration by Duncan model. Hence, the modified model can be used in the design of linear induction motors. Furthermore, the change in equivalent circuit parameters at different operating conditions can be taken into account. The comparison of the simulation results using the proposed model with the experimental ones shows the high accuracy of the model.

The paper represents the development of an adaptive multi-criteria algorithm based on fuzzy approach for the decision making part of the differential transformer protection schemes. At first some effective phenomenon have been examined. Then off-line examination results have been implemented for adapting the relay parameters such as fuzzy functions, weighting factors and tripping threshold to relay conditions and transformer characteristics. Self-adjustment of relay parameters has improved the speed of operation, dependability and security of relay. Different tests have indicated satisfactory results and less than half a cycle for the mean of operating time.

Molecular mass of asphaltenes in petroleum fluids is one of important parameters to study and modeling of heavy organic depositions in petroleum fluids processing. Molecular mass of asphaltenes are measured by the same methods used for molecular mass determination of polymer compounds. In this work, size exclusion chromatography methods, which are used broadly for molecular mass measurements of asphaltenes, are described and the main factor involved in obtaining undesirable results due to observation of very low molecular mass in the measured molecular mass distribution are discussed and attributed to high polarity of asphaltenes particles and mechanism of SEC methods. A new method for correction of measured data for these undesirable effects is presented. This method is based on finding a new calibration curve (correlation) for molecular mass measurement by SEC. The experimental data of some asphaltenes samples deposited from four Iranian crude oils have been corrected. The corrected results show the effectiveness of required modification in molecular mass distribution of asphaltenes.

During the flotation operation, recovery may increase, decrease or remain constant with variation of parameters like pH, type and concentration of collector, type and concentration of depressant, % solid in pulp and many others. In this study the attempts have been made to use the flotation rate data to optimize the above parameters and on account of this, the optimum RTD for such model has been determined. In order to control, evaluate and select the suitable parameter, the separation optimized conditions: PH: 9                                                                                                                                         Depressant: 1000 (g/t)                                                                                                                r.p.m:1000                                                                                                                                 %Solid: 23 Time of d80 = 75: 14 minIt is possible to achieve S.E = 87%  

This paper presents noise analysis of a regenerative analog frequency divider at microwave C band frequency. Using harmonic balance and conversion matrix methods, by considering a simple noise model for active device, phase and amplitude noise spectrum densities for the frequency divider (without considering the noise of excitation signal) are calculated and simulated.

The effects of mercerizing, by aqueous solutions of caustic soda (NaOH), on the mechanical properties of friction-spun cotton yarns were studied. A rotor and a series of friction cotton spun yarns, 125 tex, were produced. A laboratory: mercerizing machine was designed and built. The yarns were mercerized with and without tension, at room temperature. The mechanical properties of mercerized and unmercerized yarns were tested and compared. The results indicated that mercerizing under tension in most cases improved the strength of friction- spun yarn samples in a limited extent.

Cellular Manufacturing System, is an effective system for economical production of forming of parts. The identification of part families and machine cells are the main steps of the process. Many approaches have been developed for this problem in the literature. This problem, from computational point of view is NP-Comlete. Hence, the application of optimization methods fails to solve relatively large size problems. In this paper, attempt has been made to apply Simulated Annealing (SA) which is an efficient tool for combinatorial problems to solve cellular Manufacturing Systems. Demand for each part due to its inherent uncertainty Volume of intercell moves and minimizing total within cell load variation has been taken into account. Analysis on the controlling parameters of SA has been performed and the reasonable results have been provided.  

Among the conventional methods for treatment of colored textile waste, the electrochemical technique seems to be the most powerful, simple and economic. In this method a direct current is applied to an electrochemica cell containing coloted waste and due to the passage of current oxidation and reduction reactions is caused the destruction of the dyestuff and removal of the color from the solution.                                                                                                                    In present research dyebath solution containing direct, dispers, acidic, reactive dyes and mixture of those were treated and %90 of color removal and %60 reduction on COD of the solution sere achieved. The parameters such as time, current, voltage, type and surface area of the electrode, pH, electrolyte on the pert of the cell were examined and their role on  the efficiency of the method were clarified.                                       The spectroscopic studies showed that the dye material was reduced to simple components.

Sugar cane juice can be better clarified and decolorized by ultra-filtration than by other techniques. In this article application of ultra-filtration in the clarification of cane sugar juice has been described, Several experiments were car­ried out on the raw sugar juice, and decolorization and permeate flux have been studied in this system; furthermore by consideration of different theoretical models, gel layer model have been proposed for this system.