INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2000 | Volume:11 | Issue:2|Papers Count:13

Modem power systems are usually interconnected to each other and security assessment in such large systems are very important and vital. In such systems security assessment must be provided using fast and accurate methods. Ranking methods have masking errors and can't detect all critical contingencies correctly.. In Bounding methods that are based on the localized effect of contingencies, power system is divided into appropriate subnet works. One subnetnwork represents the subset of buses situated in the vicinity of outage area and identified using return path of outaged element flow and topological search. Voltage sensitive subnet work is identified using electrical distance concept between buses and reactive sensitive subnet work is identified using base case sensitivity matrix. For this buses exact solutions are obtained and for rest of them approximate techniques are utilized.Results of Iran's power system and other systems shows that in large systems local methods are more efficient, faster and more accurate. Use of sparse vector methods along with compensation techniques has increased the efficiency of the implemented computational methods.

The short -term production planing function for setting up a flexible manufacturing system (FMS) prior to production should be developed so as to interact well with the operation of the system over a planing period. During FMS operation, planning for system set - up has to be performed somewhat periodically, for example, when the part mix is changed, or when the production requirements are finished for some part types, or when a machine breaks down. A model is presented for this function. This problem is formulated as a mixed –integer program. To decrease computational time, a heuristic procedure is developed. Initial investigation indicates that the procedure is capable of identifying good solutions. The performance of the procedure is discussed.

One of the important subject in hydraulics and hydrology is flood routing where it could .be achieved by solving Saint-Venant equations. Based on what term is omitted from the momentum equation several methods would be obtained, Kinematic Wave, Diffusion Wave and Dynamic wave. In this study, due to its simplicity compared to the Diffusion Wave method, Matched diffudivity method has been employed. In order to apply one of the methods, the conditioned the method holds with acceptable accuracy should be determined. In this regard comparison among the three methods has been conducted. In the comparison the effects of different parameters such as channel slope and width, numerical calculation increments, cross section, and the slope of the inflow hydrography, on the outflow hydrograph have been clarified. The objective of this study was to find the cases the different methods are similar or different in results. Generally speaking, increasing the channel slope, reducing its width, and reducing the inflow hydrograph slope results to have close outflow hydrigraphs otherwise the results are significantly different. These conclusions have been obtained for rectangular, trapezoidal. triangular and curricular cross second.

In this paper, an analytical solution for heating a rectangular sensible heat storage packed bed with thermally isolated walls by a non-thermal equilibrium flow of incompressible fluid is presented. It is shown that in this case, the heat transfer phenomenon will be one dimensional. Using an energy model, the temperature difference between the fluid and solid phases is simulated. Application of perturbation technique is resulted in an analytical solution which consists of the steady-state and transient parts. The amplitude of transient part will decrease as time goes on.

Sweetening of sour gases and removal of carbon deoxide and hydrogen sulfide is considered to be one of the most important processes in oil, gas and petrochemical industries.Presence of these compounds might cause problems in downstream units such as corrosion, environmental and catalyst pollution. Usually the absorption of acid gases by means of a reacting liquid like amine solutions is accomplished in plate columns. But because of some specific problems being encountered in this kind of columns, recently packed columns are being taken into consideration again. It is believed that they provide more effective contact between sour gas and amine solution, therefore increasing the total efficiency in this way. Acid gases enter the liquid phase and react rapidly with amine. Usually equilibrium models are for designing these columns, but they do not actually yield very precise results.In this paper, using mass transfer model. a rigorous mathematical model has been developed for packed columns. This approach yields the pressure, temperature and concentration profiles of acid gases, amine and products of their reactions along the columns. Reaction rates are calculated at any point in the column. Also concentration profiles in liquid film at any height of the column can be obtained.In this way, the opportunity for more precise design and of the column is provided. Also using the developed mathematical model, the effects of various parameters on the operation of a packed column are studied.

Three mathematical methods called non-linear, linear and four -point were used to simulate the rate of corrosion reactions. The most appropriate method was shown to be the first; because it is capable of simultaneous calculation of both the tafel slope and the corrosion current density ; irrespective of what interval is chosen for the electric potential. In order to obtain a best fit between the empirical and the empirical and the theoretical data, utilization was made of the least square technique with exponential polynomials and the polarization equation i =icorr.[exp (aDe) - exp (-bDe)].The simulation program, called CKS, is capable of accurate evaluation of the corrosion parameters, with a relatively high speed.

In this research, effects of mixed structure of martensite and lower bainite on the mechanical properties and £facture toughness (KIC)of ultrahigh strength steel containing 0.45 C, 0.50 Ni, 0.97 Cr, 0.90 Mo and 0.06 Ti wt pct have been studied. For this purpoSe, test samples were cooled from the austenitizing temperature of 900oC to 310oC in a salt bath, maintained for 2.5, 5.0 and 7.5 minutes and were finally oil quenched. The mechanical properties were compared with those of The samples directly quenched. With tempering at 300oC it was found out that presence of some lower acicular bainite results in modification of martensite structure and improves mechanical properties, specially KIC. Any further increase of the bainite constituent reduces both the sharpie impact energy and tensile strength. At room temperature the most suitable tensile properties for notched, samples, charpy impact energy and K1Cwere obtained for samples that underwent bainitie transformation for five minutes (with 35 vol pct lower bainite). Samples with mixed structure of martensite and 35 vol pct of lower bainite showed higher impact toughness at -80oC and higher temperatures when compared with samples of tempered martensitic structure. Fractography studies with scanning electron microscope showed that mixed martensite and lower bainite structures displayed higher ductility and better £facture surface morphology compared with tempered martensitic structure.

The effects of PCu as a modifier on the AI..17-19% Si hypereutectic alloy has been investigated. The modification of primary silicon particles was studied using thermal analysis technique and microstructural examinations. It was shown that the finest microstructure can be obtained when the P content in Cu15P modifier was 0-1%.

A Design algorithm for gasket plate heat exchangers have been developed and presented. the algorithm is capable of specifying plate material, dimension and thickness as well as the number of panes for the fluid involved.The software thus developed is capable of receiving information quite fluently. Check input data, and provide the user to estimate the cost of manufacturing the designed equipment.

Various mathematical models have been developed so far for simulation of thermal cracking reactors, each having its own simplifying assumptions. These assumptions reduce the complexity of the model and decrease the runtime of computer programs. The most important one is assuming one dimensional model and neglecting radial gradients. They are also intended to relate the results to some limited parameters. As a matter of fact, the rate of formation of coke, the undesired product, is influenced mainly by wall temperature.Therefore the necessity of a better prediction for temperature profile in radial direction is inevitable.This may not be implemented through a one - dimensional model. In this work a two dimensional model is developed and solved with Crank -Nicholson method. The results are compared with one dimensional ones. These results consist of products distribution, temperature and pressure profiles, fluid velocity profile and conversion at different positions.The results are also compared with an industrial naphtha cracker operating in Arak petrochemical Complex.

This research study experimentally and theoretically the behavior of concrete cylinders and cubes reinforced with perforated steel plates. Experimental program on cylindrical specimens reinforced with perforated steel plates as lateral reinforcement for confining concrete, is conducted to evaluate influence of Local- Global confinement with high lateral stiffuess on concrete. Test results indicate that the proposed confining system, considerably increases compressive strength and specially ductility of concrete. Also, it is observed that this system of confinement performs equally or better than spiral confinement.Formulations for predicting the behavior of confined concrete with perforated plates (strength and ductility) are proposed which correspond to test results satisfactorily.

Inelastic solution of an axisymmetric boundary value problem is obtained from elastic solution using variable material properties method. The distribution of material properties, which are considered as field parameter is obtained as a part of the solution. This method is applied to process of cold worked fastener holes. The residual stress field induced by the process is determined. The actual material behavior in loading and unloading is utilized, while different hardening models, isotropic and kinematic hardening, are also used. Results are shown to be in good agreement with published results. The process of recoiled work is also studied. It is shown that a recold worked fastener hole may have a more useful residual stress pattern.

In this paper one type of Maglev is introduced and also principles of linear motors that are used in Maglev is explained. Low temperature superconductors with an air core is used for linear motor of this type of Maglev. In addition, main parts of this electromagnetic system are introduced. Besides the principles and analysis of the Propulsion, Levitation and Guidance electromagnetic forces in Maglev system and calculation of these forces are presented. Various operating conditions of Maglev are simulated in order to find guidance for its applications. After calculating mutual inductance between 8 - shaped coils and superconductor coils and also the effect of vertical and horizontal displacement affected by weight of vehicle and the effect of curvature of guide line on mutual inductances, Propulsion, Guidance and Levitation forces will be calculated and the results are shown. These calculation are done for various speed to use the results for designing and controlling of the pilot Maglev.