MODARES TECHNICAL AND ENGINEERING
Year:2005 | Volume:- | Issue:18|Papers Count:11

Equilibrium data of the moisture content of ammonium nit rate when exposed to air flows with 20 to 65% moisture were obtained and the absorption and desorption isotherms were plotted at 29,38 and 44°C using EMC. The evaporation (absorption) rate of moisture was determined and its relation with the moisture content was investigated at constant temperatures. Granular ammonium nitrate (explosive grade) from Shiraz petrochemical company was used. The molecular diffusion coefficient of moisture in ammonium nitrate was calculated at the temperatures mentioned above an d its relation with temperature was determined.

Hydrodynamic parameters of an internal-loop airlift reactor for a water-in kerosene microemulsion, as a cold model of petroleum biodesulfurization, were studied. The results obtained in this study showed that the downcomer-to-riser surface area ratio and gas velocity affect the hydrodynamic parameters. An increase in the gas velocity and/or decrease in the downcomer-to-riser surface area can cause a rise in the local and global gas holdup, a decrease in mixing time and have an effect on the liquid circulation velocity. It was found that the theoretical model of Chisti could not predict the values of liquid circulation. velocity in the microemulsion system. Empirical correlations were obtained by this work that can predict the liquid circulation velocity and mixing time with a reasonable degree of accuracy.

Although the advantage of JIT system have motivated many companies to implement this system, but uncontrollable varying environment parameters and the impacts of these parameters in reducing the efficiency of the sys tern is the major problem in JIT implementation. Based on our literature review, determination of the number of Kanbans and investigating of JIT perfonnance in different conditions is one of the most interesting research subjects. In this paper we first develop an integer linear programming (ILP) model to determine a fix number of Kanbans in each working station. Then based on this model we introduce another ILP model to control varying production parameters. The second model determines variable number of Ka nbans for each station. Our objective function consists of inventory holding costs, shortage costs and costs of having variable number of Ka nbans. We also compare the efficiency of both models regarding to variation in demand, processing times, capacity of stations, etc., by solving some test problems. We found that the second model dorninates the first one in all cases.

In this paper we propose a conceptual model for evaluating the information technology (IT) effect on productivity at organizational level. There are many researches that confirm a positive correlation between Information techno logy and productivity but many others that reject. Therefor the investments on IT including hardwares, networks, softwares, and internet alone will not necesserily improve productivity. Organizations should also invest on complementary investments such as investment on changes in strategies, work practices and new products, align with information technology investments. This paper proposes that complementary changes including changes in customers" and suppliers" interactions and internal processes, must als O be considered as complementary investments.

In this research the contaminated surfaces of a Ti -6AI-4V alloy, which produced by stress, relieve annealing in a furnace having a vacuum of 2*10-4 mm mercury, were investigated by the X Ray Diff Taction (CRD) technique. For this purpose, test samples were heat treated at 500°C for one hour and 550°C, 600°C, 650°C, 800°C for five hours. The method of identifying equilibrium phases in this alloy was derived and the lattice parameters of these phases were calculated by the use of diffractometer. Comparison of the calculated results with the values given in source books shows the validity of our results. Study of the effect of the annealing tern peratures on lattice parameters of the a phase show>d that at temperatures of 650°C and higher, desolution of oxygen in this phase increases the volume of crystal lattice. It is not possible to get rid of surface contamination completely by removing the surface layer with the colour change. XRD Analysis of the surface oxide layer showed that the TiO is the first oxide formed in the surface when annealing heat treatment is done at 800°C for 5 hours. The lattice parameter of TiO was measured to be 4.294 A.

The wettability of AIN, AIN-BN and A12O3 by molten steel has been studied using sessile drop method. All of the substrates presented non -wetting behaviour after one hour contact with the liquid alloy at 1550°C. The evaluation of liquid-vapour and solid-liquid tensions and the values of adhesion work showed that wetting is governed by chemical interactions at solid -liquid and liquid vapour interfaces. Addition of BN to AIN substrate on one hand reduces its densification rate and on the other hand modifies its wettabilty by molten steel.

The damage caused to the environment by the by -products of the mining industry has been the subject of much attention in the developed world. In this paper, attempts have been made to introduce practical and economical methods for reclamation and rehabilitation of the mining waste. We begin by eXplaining the relationships between the mining industry and the surrounding environment. The nature of the damage caused to air, water and soil is discussed. Land reclamation is then discussed and data regarding physical and chemical characteristics of the mining waste is explained. Amongst different methods for stabilization of the waste, revegetation has been adopted for further analysis. Revegetation has then been subject to economic feasi bility study and the internal rate of return and the net present value for typical project in Iran is calculated. It is concluded that conversion of mining waste to forests is an economically feasible project. Such project, with an internal rate of return of 26.5% compares favourably with most other projects undertaken by the government of Iran.

Process optimization which is one of the most important tasks in modem industries, requires a number of research projects to be perfor med. On the other hand, a high cost of research and development activities has necessitated the development of various experimental methods, by which the factors effecting a process could be determined with the aim of performing a least number of experiments. Although many experimental designs have been introduced since 1980, Taguchi"s method, because of its comprehensive nature and its ability to present designs which are resistant against uncontrollable parameters, has found wide spread applications. In t his respect, a measure called Signal to Noise (SIN) ratio is used to show the sensitivity of optimum conditions against the variation of uncontrollable factors. In this paper, application of SIN ratio on the effect of seven factors on the flotation of Sar cheshmeh copper ore is discribed. The objective of the research was to find the optimum operating conditions which could provide a least variation of recovery (response) when distursbances such as ore type change, occur.

The purpose of this research is to show the ability of product cost reduction of one of the most economic optimization method in part manufacturing industry in Iran. For this, two -step optimization method in robust engineering is illustrated an d it is applied in two of the major companies, namely, Fanar Lool and Toklan Toos; Obtained practical results are studied and compared with their current conditions. In order to reduce trail tests which in turn reduces costs of conduction, pair-factor interaction effects are estimated through an index.