INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2003 | Volume:14 | Issue:4|Papers Count:19

One of the most sensitive and important problem in mining is suitable mining method selection. Suitable mining method should be determined on basis of geological, geotechnical, geographical, and economical Factors. Distinguishing of all parameter that have effect in mining method and determination of weighting factor of any parameter is difficult work. In this paper, attempted to disinguish important parameter that has effect in mining method selection and weighting factors calculated by using fuzzy multiple attribute decision-makings. Result of studies show that block caving method is optimum mining method for Area 3 of Gol Gohar iron mine.      

The effect of ball milling under Ar atmosphere on the reduction behavior of sintered hematite and graphite mixture. Was studied. Hematite, which was sintered at 1050°C for 24 hour, was mixed with 19.84-wt% graphite (C:O ratio was 1.1:1) and subjected to ball milling under Ar atmosphere. The milling time varied between 6 to 200 hours. In order to study the effect of milling time on reduction process under Ar atmosphere a TG-DTA technique was adopted. The samples were heated at a constant heating rate of 10°C/min from room temperature up to 1100°C and maintained for 30 min at this temperature. According to TGL curves, the onset temperature of reduction was decreased with milling time. The rate of reaction (RTG) was calculated using differentiation of weight loss curve. It was found that the RTG curve consisted of two reaction peaks. The first peak corresponded to hematite-magnetite (HM) reduction and the second one could be attribute to the overlapping curves of magnatie-wustite (MW) and wustite-iron (WF) reductions. The two peaks were overlapped and broadened as milling time proceeded. The temperature of reactions decreased and the time of reactions increased significantly with milling time.    

In this paper the problem of optimal buffer size in a production line is considered. A simulation-optimization model based on Tabu search algorithm is developed and implemented in one of the production lines of Mashhad Wheel Manufacturing Company. In the model, tabu search is used to approach the global optima, avoiding the local optimum points. Using the model, it is shown that the overall buffer stock can be reduced by at least 10 percent. Considering the days prices, this amounts to nearly 31000000 Rials in savings.

For the moment, distribution of research credits has no program. The nonexistance of the plan makes the problems for the research centers, some of them are lack of the credits and some are over. . To avoid facing this kind of problems, the plan and management organization has decided to change the structure of the allocating credits. They first try to recognize the research requirements, then put them in the different level. The most important requirement in the highest level and so on. They also put the research centers into the different level of the priorities on base of some criteria then select the best center for doing the highest requirement. We believe that one of the most important criteria in the centers productivities. Thus, we provide this thesis to design the practical system for measuring the research centers productivities. For doing that we have been getting some information which was related productivity measurements then we have chosen Multi Criteria performance productivity Measurement Technique thereafter I analyze the research centers activities to create the productivities index. We also used questionnaire to get information about the different level of the index. Then we omitted some index on base of their priority. The most non-important indexes have been omitted. Then we determined the method for evaluating the quantity index. We use Topsis method to do all process, finally we have run designed model as a sample.

One of industrial applications of fluidized bed reactors is the production of maleic anhydride on Vanadium Phosphorus Oxide (VPO) catalyst. Synthesis of maleic anhydride from a feed containing 1% v/v of 1-Butene in the air have been investigated in a fluidized bed reactor at various bed temperatures and different gas velocities. The best selectivity and reaction yield obtained when temperature was approximately 395°C and gas velocity was three fold of the minimum velocity for fluidization (U=3Umf). The comparison between experimentally measured selectivity with model predictions showed that the models of K&L and Grace predicted the fluidized bed performance better than others. This is due to the more realistic assumptions of these models indicating the right image of the physical and chemical processes, which happen in the bed.

The stiffness and damping coefficients are constant and time invariant for passive suspension systems. This makes the vehicle suspension system to be far from desired performance under some road irregularities and inputs. Therefore, the controlled suspension systems including active and semi-active have been proposed in order to provide improved car dynamic performance under various road conditions. In this paper, using a non-liner full car suspension model with seven degrees of freedom, application of both fuzzy and optimal controllers have been studied for active and semi-active suspension systems. In this study, using computer simulation, both ride comfort and handling characteristics have been evaluated for active and passive suspension systems under random and bump road inputs. The results demonstrate great advantage of the active suspension performance in comparison with the passive system. Also, the ability of fuzzy controller was comparable with optimal control approach. 

Set covering problem is covering the rows of a matrix by subset of the columns at minimum cost. Considering the fact that set-covering problem is a NP-complete one, most contemporary researchers have tried recently to focus on applying heuristic algorithms to solve the above problem. The most promising heuristic method is genetic algorithm trying to simulate the natural evolution process. This algorithm is an efficient and suitable approach to handle set covering problems. In this paper, a special design of the proposed genetic algorithm is used to solve such problems. The computational result of great trails confirms the efficiency of genetic algorithms.

Independent brake valve, is a diaphragm pneumatic valve with low out-flow and self lapping property. By moving valve handle, the valve delivers reserved compressed air to other sections of the system. The pressure of output flow is adjusted based on pre-set pressure of a spring which is usually between 45-50 psi. In this paper, first, the valve is described and analyzed based on its functionality. Then, the mathematical equations of various sections of valve are presented. After that and based on those equations, the mathematical model of the whole valve is derived. To evaluate the model, the results obtained from simulation are compared to the experimental results. After validation of the model, it is used as a reference to evaluate the functionality of the valve at different operating conditions. In general, investigation on the steady state and also transient response of the valve is the main objective of this research.

There are a few criteria for predicting fracture in cracked specimens. In this paper, the maximum hoop strain criterion is employed to study mixed mode IM fracture. The structure, therefore three criteria for finding the critical members in steel space frames have been presented, namely, load carrying capacity criterion, strain energy criterion and stiffness criterion. It has been shown that the static alternate path analysis is only an approximate simulation of the progressive collapse phenomenon and this analysis is not adequate by it self. Consequently dynamic alternate path analyses must be undertaken to evaluate accurately the progressive collapse behaviour of the structures. Also in this study, the effects of strengthening grids on the behaviour of steel space frames have been evaluated. Finally, the obtained results from the alternate path analyses have been used to draw some important conclusions and to suggest some general recommendations for progressive collapse resistant design of steel space frames.

The surface of titanium exposed to atmosphere is covered with thin layer of TiO2. This layer oxide due to low thickness, high porosity and low mechanical strength can not protect its surface from corrosion. So, in order to produce oxide layers on the surface of titanium, anodizing is performed. In this research, anodizing of titanium was performed in H2SO4 and (NH4)2SO4 solutions at 25°C. Anodizing of titanium in H2SO4 solution was performed under galvanstatic conditions and in (NH4)2SO4 was performed under potentiostatic conditions. The results show that layers formed in H2SO4 are compact and then they are been porous and stable. These layers contain high relative porosity and the variations of thickness relative to time are logarithmic. Anodic layers formed in (NH4)2SO4 are compact and insulator. The thickness of layers increases with increasing of concentration, but after decreasing of current and reaching to zero, increasing of time had no affected in thickness. The SEM and XRD techniques show that these layers are amorphous.

In the domain of changing the world, advanced manufacturing concepts and introducing new philosophies, Total Quality Management (TQM) plays a vital role. As one of the excellent management philosophies TQM has been applied to improve quality more than before by satisfying and delighting customer, achieving objectives and goals of organizations and answering social needs. Approaching these demands, TQM has successfully integrated a various number of tools, techniques, methods and applicable concepts. On the other hand to apply efficiently and effectively any philosophy, technique, method, model, tool and so, the first step is to deeply and carefully understand history, concept, principles and other aspect of them. This paper attempts to investigate and identify history, definitions, concept and other futures of TQM.

In the present paper, progressive collapse and its main causes have been investigated. The approaches for reducing the risk of progressive collapse are event control, indirect design and direct design. Two basic means of direct design are local resistance design and alternate path method. Based on the studies undertaken on the progressive collapse behaviour of the structures, it has been demonstrated that the alternate path method is the most efficient and economical way for progressive collapse resistant design. Using this method, it is possible to assess the ability of structures against progressive collapse. In the present study, the progressive collapse behaviour of steel space frames has been investigated using alternate path method. The first step in the alternate path method is to find the veridical members in the mechanism of crack growth are brittle fracture with linear elastic material properties. Thus, the size of plastic zone around the crack tip is assumed to be negligible. Fracture is predicted using both the singular term and the second term in the series expansion for strains. The aim is to study the effect of the second term on the direction of fracture as well as the fracture load in plane stress. The results show that this term can influence significantly brittle fracture in mixed mode loading. The results obtained for plane stress are compared with earlier results corresponding to plane strain. The effect of Poissons ratio on the fracture angle and fracture load is also studied.

The purpose of this article is to present software for transient analysis of rotor bearing systems, developed for solving any number of non-linear second order ordinary differential equations. Transient solutions are still widely used for evaluating the vibrational behavior of rotor bearing systems containing dynamically loaded journal bearings with large unbalance or noncircular orbit type squeeze film dampers, such as dampers without centralizing springs. For parametric design studies, such transient analysis need rapid means for evaluating the motion dependent fluid film forces and for narrow bearings or dampers (aspect ratios less than 0.5) modified short bearing approximation to the Reynolds equation, developed by this author, has generally been assumed. Runge-Kutta integration and Modal approach routines were developed side-by-side including the associated force evaluation and post processing software. The routines obtain solutions and steady state vibration behavior predictions for a journal bearing (or a squeeze film damper) supporting a general multi-mass rotor bearing system on flexible supports. It can be equally applied to rigid rotors as well as flexible rotors. A combination of direct integration of system equations of motion and a modal approach were used to obtain instantaneous absolute displacement, velocity and acceleration of an n degree of freedom system. The utilization of both approaches serves as a valuable numerical method to overcome the problems associated with the need for appropriate system reduction to avoid unnecessarily high natural frequencies. Post processing of the output motions and forces at any location is developed to provide both numerical and graphical output involving time and orbital motions as well as spectral analysis. As a result, phenomena of interest to design such as critical speeds, bi-stability, instability and jump can be checked for rotor bearing systems.

The crushing of tube subjected to lateral loads is a complicated problem governed by highly non-linear equations for stress, strain and displacement because of the large deformation and material non-linearity. The aim of this paper is to analyse the elastic-plastic behaviour of the tube subjected to lateral loads by using a simple numerical simulation. This simulation is a mixed method of finite element method and finite difference method. Thus, it simplifies the analysis of process and reduces the computational time. This simulation can be used for analysis of mechanical absorbers and for design of the casing. By using the simulation, the effect of amount of deformation on stress and strain distributions and the collapse load have been studied. The obtained results and comparison them with experimental results and finite element results using software ANSYS verified the accuracy and reliability of the proposed simulation.

Due to strategic importance of purchasing in the success of firms, more research required to be done in the area. This paper develops a procedure to select the reliable suppliers. The procedure considers the main strategies of firms and provides information, evaluated candidates and filters them step-by-step. Using compensatory and non-compensatory criteria, the superior, good and weak suppliers are specified. The mathematical models are used in each step if necessary. The advantage of hierarchical models is to use the new information is available in each step.

In this paper the existing methods of strengthening for reinforced concrete beams were introduced and also using ANSYS structural software, reinforced concrete beams strengthened with external unbonded reinforcements were modeled and analyzed nonlinearly to determine their ultimate flexural strength and deformability. For this purpose, 24 beams with different dimensions and different properties were modeled, analyzed and compared with the experimental results. The effect of different parameters, such as percentage of internal reinforcement, shear span to effective beam depth, the existence of deflectors to hold in place external reinforcement, span length to effective beam depth ratio, and the percentage of external reinforcement on the ultimate flexural strength and deformability Were studied. The results of the analysis show that increase in shear span to effective beam depth ratio, will cause a decrease in the external reinforcement force, flexural strength and deformability of the beam. The use of deflectors for external reinforcement will decrease deformability but increase flexural strength of the beam. Increasing percentage of internal reinforcements will decrease both the force in external reinforcement and deformability of the beam. In spite of the decrease in deformability due to the usage of external unbonded reinforcement for strengthening of reinforced concrete beams, the method can be safely used for flexural strengthening of reinforced concrete beams. Finally the model introduced in this research can be properly used for the analysis of the beams strengthened by external unbonded reinforcement.