INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2004 | Volume:15 | Issue:4|Papers Count:18

In cases of supply chain management, various objectives should be considered such as, minimizing the number of suppliers and purchasing cost of required items and maximizing the items quality and so on. In this paper, we deal with selecting the best suppliers in a multi-criteria field by developing a new mathematical model. In order to show the validity and the flexibility of the model, the model is solved for a real world problem.

Quality is considered as an important key factor for achieving business goals and it is used usually by customers as a measure to evaluate products and services. Quality improvement is synonymous to variation reduction and conformance to design specifications. This paper provides a heuristic approach for evaluating performance of a process using distributions for two quality characteristics. Two gamma distributions are considered to evaluate the performance of the proposed approach. Application of this method is also investigated for detecting shifts in the process mean and variation.

Damage identification from changes in vibration characteristics of structures is the subject of many current researches. In this regard, several different methods, Le. vibration frequency changes, mode shape changes, strain energy mode shape changes, and the wavelet analysis, have been suggested. In this paper, these methods are applied to a rectangular cracked plate. The vibrational characteristics of the plate are obtained, and the results for different locations and sizes of the crack are studied. This comparison shows that the method of vibrational frequency changes has the least sensitivity to the presence of the damage, while the methods of the damage index changes and the wavelet analysis are most sensitive to the damage. The damage detection in all of the above mentioned methods except the wavelet analysis is done through detection of any changes in the vibrational characteristics before and after the introduction of the damage.

incorrect utilization of cement kiln returned dust not only can produce variations in kiln operation conditions, resulting in the corresponding undesirable consequences such as decrease in clinker quality, but also may lead to the enhancement of volatiles circulation and the subsequent repeated kiln stoppages due to the phenomenon of cyclone jamming. The importance of regulating the amount of returned dust content of kiln feed should be considered since higher contents of volatile constituents in kiln returned dust along with their considerably higher volatilities compared to the corresponding fresh kiln feed are liable factors for the enhancement of volatiles circulation.

In this paper we present an exact method for finding optimal replenishment over a fixed planning horizon for items with linearly time varying demand and under inflationary condition. We consider a perishable item that follows two parameters weibull distribution. Two numerical examples are taken up to illustrate the solution procedure and sensitivity analysis of the optimal solutions with respect to the parameters of system is also carried out.

In this study the effect of the amount of Nickel in melted Zn and the amount of Si in base metal (steel) and also the duration of immersion time have been studied on three alloyed steels (DIN 1.0012, DIN 1.0037 and DIN 1.0042). Some parameters of coated layers such as total thickness, the thickness of the layers, the uniformity of coated layer, the cohesion of layer and finally the resistance against corrosion has been investigated. For this study optical and scanning electron microscopy which was equipped by EDX system and also salt spray test have been used. By studying several galvanized coatings it is shown that the best uniformity, cohesion and corrosion properties can be achieved by making use of a liquid bath, with 0.1%Ni.

Inferring reservoir operating rules is a complementary stage in applying long-term or medium-term implicit stochastic models to reservoir operation optimization problems. The method of dynamic programming (DP) has been used as an optimization tool to provide the input-output data set to be used by ordinary least square regression (OLSR) and an adaptive neuro-fuzzy inference system called ANFIS to derive reservoir operating rules. The OLSR and ANFIS based rules are then simulated and compared based on their performance in simulation. The methods are applied to Dez reservoir in a long-term planning problem as well as in a medium-term implicit stochastic optimization model. The results indicate that ANFIS does not make a significant improvement over simpler OLSR model in long term planning problem. However, ANFIS is more beneficial in medium term implicit stochastic optimization as it is able to extract important nonlinear features of the system from the generated input-output set and represent those features as general operating rules. It is emphasized that using ANFIS along with an adaptive learning algorithm would be justified where we face with the problem of knowledge extraction from a nonlinear or ill-defined information existing in the data set of the problem.

For large-scale structures, the pattern of structural matrices are of great importance. Improving the patterns of sparse matrices not only reduces the cost of solution, but also makes the processing of large matrices feasible.In the present paper, concepts and definitions from graphs and algebraic graph theory are briefly presented. Various methods are investigated for optimal ordering to reduce the profile of the structural matrices. Special attention is paid to Sloan s method as a powerful approach for profile reduction. In order to show the capability of this method, examples of Everstine are examined. Different values are adopted for the priority function of Sloan and the results are compared. Three parameters are used in place of two, and the resulting profiles are compared. The uniformaty and non-uniformaty of nodal degrees in various models are also studied.The spectral method using the Laplacian matrix of the models is programmed and applied to Everstine s examples. The difficulty of computational time is reduced employing improved hybrid spectral-graph method. Combining the hybrid Ritz method and Sloan's approach, an improved hybrid Ritz method is developed.

To optimize simultaneously machine loading, operation planning and operation routing in a flexible manufacturing system (FMS), a binary as well as a mixed integer programming (MIP) is developed in this paper. The model is designed based on the concept of just-in-time. The objective is to make the load of the machines balanced, to decrease lot sizing for more flexibility as well as to adjust the scheduling for on-time delivery. Since the resulting model for real world problems happens to be a very large scale one, the classical methods are not capable of solving it. Thus, we also design a meta-heuristic algorithm to solve this model. It is called Tabu-SA. The computational experiments show the proposed model is superior over the existing methods as far as the computation time and the accuracy of the solution is concerned.

In this paper, the bronze alloy coating was created on steel using acidic and basic baths and the effect of various parameters was investigated. Electrodeposition of bronze alloys in acidic bath of sulfate solutions was performed.The essential components in this bath were copper sulfate (CuS04.5H2O) with concentration of 20 g/l and tin sulfate (SnS04) with concentration of 30 g/l. to achieve the optimum conditions, sulfuric acid (l00g/l), phenol sulfonic (40g/l), gelatin (2g/l) and β-naphtol (lg/l), was added. Coating with 10-12%wt Sn was obtained in acidic bath at 3 A/dm2 and 25°C. Also the basic cyanide solution was used for electroplating. The essential components was copper cyanide (CuCN) with concentration of 25 g/l and K2Sn03.H2O with concentration of 40 g/l. while also KOH (l0g/l) , KCN (64g/l) and Rochelle salt (45 g/l) were added to the bath. In the latter bath, the current density and temperature were 3 A/dm2 and 40°C respectively and %Sn of coating obtained 10-12. The cathodic current efficiency and coating morphology were investigated for the both baths.

The primary function of a Zinc Oxide Varistors is to sense and limit transient voltage surges without being destroyed. Their Current (I)-Voltage (V) characteristic is non linear similar to that of a Zener diode. Varistor can be used in both AC and DC field and over a wide range of voltage, current and energy absorption capability.The ZnO Varistor shows degradation in I-V characteristic in excess of 10% to 20% when subjected to high current surges. However, each application requires a reliable characteristic of a Varistor and to be remained stable to its original value during usage and after experiencing the oncoming surges.In this study by using Annealing, stability of Varistor will be evaluated and its effect on increasing of energy absorption capability will be studied.The results showed that after annealing at 600oC for 2 hrs, the stability of the system has been increased. The temperature range of formation of γBi203 phase was determined to be 600-700 oC. The data showed some changes in other properties of the system after this process.

Aluminum sacrificial anode is an important anode which is used vastly by industries. Due to its availability and also its high driving potential, is used for catholic protection of structures in sea water. Pure aluminum is not used because of forming a passive layer on its surface and causing reduction in anode efficiency Therefore some elements such as, indium , mercury, tin, gallium are added to anode to prevent passivation. Also other elements such as manganes , magnesium, titanium, cadmium and bismut are added to anodes for the improvement of its electrochemical properties.The aim of this research was to determine the effect of titanium and cadmium added together and also individually. Tests were carried out to determine anode efficiency, polarization behaviour, open and closed circuit potential, corrosion rate. Metallographic analysis, EDAX, SEM and XRD were carried out on samples with different concentrations of titanium and cadmium. The results show that titanium causes homogeneous microstructure and increases the anode efficiency and shifts the potential to more negative values. It was revealed that cadmium reduces adhesion of corrosion products and causes the elimination of passive region in polarization curve and shifts the potential to more negative values. Addition of 0.02% cadmium and 0.02% titanium (optimum position) to aluminum anode results in increasing anode efficiency from 84% to 94% and reducing the corrosion rate from 113 mpy to 45 mpy and shifting the potential from -1084 mV to -1283 mV (SCE).

In order to seismic microzonation of Urmia city, micro tremor measurements were carried out in 200 sites. Data were recorded both on sediment and rock outcropping reference sites. First different analyzing methods were investigated including H/V and Hs/Hr techniques. Results show that whenever sediment site is far from reference site, Hs/Hr can not demonstrate resonance peak despite to H/V method. Whenever sediment site is close to reference site, Hs/Hr method is able to declare site characterization. However H/V method does it better. It is concluded from this section that H/V technique is more applicable. In second part microtremors were evaluated for detecting topographical effect on ground response. An example hill called Tappeh Shahrak Electronic was investigated as a case study. Five microtremor measurements were carried out and by computing two horizontal components and a vertical one it is shown that microtremors are able to detect topographical ground response. Then reference rock outcropping sites were examined in this regard and it is concluded that they must be evaluatedfrom this point of view.

Memory and computer time consumption are the two major obstacles in applying dynamic programming to complex multi-reservoir systems. This challenge has initiated the so-called curse of dimensionality solutions in water resources studies. Among many others, Discrete Differential Dynamic Programming (DDDP) is a mean to deal with the dimensionality problem. The method, which is based on the traditional dynamic programming, narrows the solution space through the assumption of a corridor around a nominal trajectory. Optimization is carried out through the iterations around this trajectory. At the end of each iteration, the final solution is assumed as the new nominal trajectory for the next iteration. The process is continued until no further improvement is possible.In this paper, a general multi-purpose multi-reservoir computer program is developed that is flexible in accepting any type of system configuration. The proposed model, in addition of using DDDP method, can handle joint water supply allocations with reservoirs in series or parallel. It is also possible to reduce the firm demand deficits, such as municipal needs, through water transfer from upstream allocations to non-firm uses, such as agricultural demands. The model was applied to a complex system with seven reservoirs and several demand points. The results indicate a distinguished improvement over the usual DP method. It was noticed that the appropriate assumption of state variable and initial nominal trajectory are crucial in reaching the optimum solution. Furthermore, changing the number of states has an insignificant effect on finding the final optimum solution. It should be noted that, there are no restrictions on the number of reservoirs within the model; however, available CPU and time consumption must be considered in mode ling complex systems.

In this Article for thermal and resulting thermal stress analysis of the exhaust valve, the finite element method and commercial package of ANSYS code is used. The exhaust valve of the four stroke engine of the PAYKAN vehicle with 65 hp power in 4700 rpm, is considered. For analysis the maximum engine loading is used. The analysis is began from an initial condition and followed until steady state condition. In steady state the temperature of the valve is almost constant. After thermal analysis, resulting thermal stresses are calculated. The initial valves of the boundary conditions such as temperature and pressure of the gas in the cylinder, are given from the Irankhodro motor research company (IPCO), and analysis is carried out base on actual values of the boundary conditions. The results are compared with the results of the other researchers, and observed that there are no differences between them.

After a short review of the poroelastic theory and presentation of a Finite- Element formulation, a one-dimensional elastodynamic analysis of aortic tissue has been carried out. Using a computer program ( in Visual Basic) and applying the material and geometrical parameters, elastic and poroelastic theories have been compared. Effect of certain parameters including fluid density, permeability and porosity, on tissue behavior has been studied.