INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2004 | Volume:15 | Issue:1|Papers Count:16

In this research, different steps of steel production of Mobarake Steel Company of Isfahan were investigated. Several samples were taken from different steps of the production. The oxygen chemical potential of the molten steel in each stage was measured. With the use of thermodynamic calculations and considering the working conditions (temperature, chemical composition, and...) the relationship between the dissolved oxygen and other elements were plotted and the activity of the oxides with respect to the chemical composition of element was calculated. The chemical composition of the slag according to the amount of added materials and the amount of material loss was calculated. The samples were investigated by the optical and the scanning electron microscope and the chemical composition of inclusions were analyzed. The chemical compositions of the inclusions in the samples were investigated by scanning electron microscope. The chemical composition of the slag was analyzed. Finally, with the use of these results, a close relationship between the kinds of inclusions formed in each step with the oxygen partial pressure was developed.

At the present time Bioleaching is one of major areas of research in metal sulfide concentrate. In this paper the bacterial leaching of Sarcheshmeh copper sulfide concentrate with sulfuric acid in the presence of Thiobacillus ferrooxidans (Sarcheshmeh mine (PTCC1647) and DSM583 from Germany) were investigated to increase the recovery of copper.The chemical composition of the concentrate is 30% Cu, 24% Fe and 31% S. The main mineralogical components of the concentrate are chalcopyrite, chalcocite and pyrite. The effect of parameters such as pH, pulp density and additives FeS2 were studied. The results indicated that leaching of the concentrate with sulfuric acid led to increase the recovery of copper in the presence of Thiobacillus ferrooxidan. This effect was more active using the bacteria from the Sarcheshme mine. Finally the results showed that the addition of FeS2 to the concentrate was beneficial in the recovery of the copper.

In this paper, a comprehensive model is developed for job-shop scheduling problems using fuzzy methodology and concepts. Processing time are considered as fuzzy numbers, and shifting bottleneck is applied and modified as an effective heuristic in solving such problems. In developed method, a heuristic algorithm is used for optimization sub-problem. This algorithm is applied for single machine scheduling problem (1׀rj׀Lmax) when release time of jobs is considered and the goal is minimization of lateness. All processing times, due dates, and release times are uncertain and they are shown by fuzzy numbers.Since 1׀rj׀Lmax is known as an NP-hard problem, the developed heuristic shows acceptable results. Solved numerical examples at the end of this study prove the capability of the developed heuristic in shifting bottleneck algorithm.

The Impedance Law can control both position and interacting force of a robot during those tasks which encounter a contact with the environment. In this paper, Multiple Impedance control (MIC) which is an algorithm that enforces designated impedance on all cooperating manipulators, and the manipulated object, is extended to fulfill force tracking requirements. It is shown that the MIC algorithm in this completed format can satisfy force-tracking desires in object manipulation tasks. Next, the disturbance rejection characteristics of this algorithm are studied. Finally, a system of two manipulators during an object manipulation task, subjected to force and torque disturbances applied on several points, is simulated. This simulation study reveals that the effect of disturbances substantially reduces through appropriate tuning of the controller mass matrix gain .The simulation results also reveal the merits of the MIC algorithm in controlling multiple robotic arms even in the presence of significant disturbances, i.e. negligible small errors in both position and force tracking aspects.

In this paper, an analog Low pass Gm/C filter with tunable cutoff frequency from 1.5 to 5.5 MHZ is designed. This filter is used in adjustable - bandwidth antialiasing video filters. Cut off frequency tuning is done using depletion - mode substrate - biased MOS gate capacitors. A fifth order elliptic filter is designed by cascade synthesis method. The filter consists of a first order and two notch Biquadratic fully differential Gm/C sections. The cutoff frequency of each section can be tuned independently by substrate bias voltage of Mos gate capacitors.The Hspice simulation results show the efficiency of this tuning method for tunable video filters.

The removal of destabilized and agglomerated particles in the filter bed includes two interconnected processes, particle transport and particle attachment to filter grains, smaller filter grains, smaller filter velocity, increase of water temperature and increase of particle size (only for particles>1µm) improve particle transport and consequently filtration efficiency. Minimum transport and filtration efficiency can be expected for particles of approximate 1µm. efficient attachment of agglomerates to the filter grains can be achieved only when the colloidal matter destabilized. In direct filtration, impurities as turbidity and color will be removed after destabilization by coagulation. This coagulation reaction takes place within a few seconds during rapid mixing. At this point the formed particles are very smaller. In Line direct filtration the setting and flocculation step are eliminated and the destabilized water is transported directly to a filter. Consequently flocculation, takes place in the bed filter. The rate of agglomeration of small destabilized particles to visible flocks is dependent principally upon the number of effective collision of particles. In contrast in conventional treatment 5 to 45 minutes may be needed for complete agglomeration of all particles. At this point enough collisions have occurred so that the flock particles have grown to a size that will settle rapidly. Fe (III) has fewer tendencies to form polynuclear species compared with A (III). The positive ions (polymers) absorb at the surface of negatively charged colloidal matter which results in a reduction of their negative potential. Therefore, it can be seen that pH plays very important role in stability of different iron hydrolysis products.

In this paper, the nonlinear bending vibration of a free-free beam is analyzed using the perturbation theory. The nonlinear part of the equation of motion is obtained using two separate approaches i.e. the invariant manifold approach, and the perturbation theory. By application of the multiple scale method, the nonlinear differential equation of motion with necessary boundary conditions is solved and the vibrational mode shapes are obtained. The advantage of using perturbation method with regard to the well known numerical approaches is the possibility of simulating analytically the effect of magnitude changes of nonlinear part in the final solution. The result shows that magnitude changes of nonlinear part causes noticeable changes in the vibrational mode shapes of the beam. Also, it is shown that in the higher modes, the effect of the nonlinear part will increase dramatically.

In this method has been studied mechanism and causes and ways of deleting or decreasing of hot cracking in welding Nickel base super alloy (UDIMET 520) in the way of GTAW in this study it has been used scanning electron microscopy (SEM) machine and quantometry. The results of this tests show that interesting to solidification hot cracking at the time of the super alloy welding with internal temperature above the melding and increasing percentage of Al.Ti is numerous and interesting to melting hot cracking because of heterogeneity of melting structure and segregation it become stronger for quick warming in welding.

The aim of this paper is to present a new applicable and suitable technique for research projects scheduling. Research projects have uncertain parameters, so there is a need for special tools and techniques for scheduling these projects. Conventional scheduling techniques are not able to model research projects or have a lot of errors. Fuzzy GERT networks using capabilities of GERT and FUZZY, is powerful tools for scheduling research projects. This paper presents a new method for solving fuzzy gert networks. In this method, activity duration time and loops trapezoidal fuzzy numbers states repetition number, and output activities from nodes of network belong to a fuzzy set. In this method, the first time gert networks Computations are done based on evaluating nodes. Process outputs are schedualated network and project fuzzy completion time. These outputs are fuzzy numbers and can be analyzed by (X-cuts. This method is more applicable and needs less computation than existing fuzzy and probability gert methods. Besides, this method can get computerized and up to date easily.

Adsorption of heavy metal ions from aqueous solutions by biomass wastes is a proper and low-cost method for heavy metals removal from industrial wastewater, since these materials are abundant in nature (renewable sources). The use of fly ash and carbon prepared from date pits ability to adsorb Cr (VI) ions from aqueous solutions are studied.The Cr (VI)-adsorption experiments were carried out to analyze the influence of pH, initial Cr (VI) concentration and adsorbent dosage, on the efficiency of Cr (VI) removal by the adsorbents. Our results showed that the Cr (VI) - adsorption mainly was depended on both final pH of solution and initial Cr (VI) concentration .At optimum conditions, while initial Cr (VI) concentration and initial pH were 10 (mg/L) and 2 respectively, by using of 2.5 (g/L) date .pits carbon efficiency of Cr (VI)-adsorption is 77%. Also it was known that adsorption of Cr (VI) ions well matched the Freundlich isotherm.

A method for defining autofrettage optimum pressure is presented. This method combines a fatigue life criterion for the vessel with a strength criterion. The optimum autofrettage pressure is obtained based on actual loading-unloading material behavior. This value is compared with the value obtained using ideal models. Material removal effect on this value is also studied. It is shown that consideration of the Bauschinger effect has a significant influence on the optimum pressure level. Several case studies are reviewed and discussed.

The Global System for Mobile Communications (GSM) Phase 2+ specifies a type of packet data service called General Packet Radio Service (GPRS). GPRS allows dynamic bandwidth allocation in which channels are allocated to a Mobile Station based on its demand. These results in better resource utilization compared to the circuit-based data services. In general, packet-based communication has a more bursty traffic and a longer connection time than circuit-based. A communication session may last for an extended period of time with intermittent packet transmissions. This traffic behavior coupled with flexible bandwidth allocation in a GPRS network results in multiplexing gain over the circuit switched data networks. This paper investigates the throughput and buffer utilization in a GPRS network under popular Internet traffic models, such as, WWW suppose the (Logical Link Control) LLC and (Radio Link Control/Medium Access Control) RLC/MAC layers in GPRS.The layers are considered to work either in acknowledged or non-acknowledged mode. A new protocol for the acknowledged mode of LLC layer, "channel dependent LLC protocol", is proposed. This protocol dynamically takes in to consideration the quality of wireless channel. When the quality is good, the transmission is allowed. On the other hand when the channel condition deteriorates, the transmission can not take place.

A new algorithm for reconstruction of design relation matrix(DRM) is presented. The reconstruction of an unknown DRM is discussed based on some design matrix projections, which was expressed by design experts. The reconstruction algorithm has been formed based on the new concept of DRM. It shows the relation between functional requirements and design parameters that exists in the related design matrix. The specifications of uncoupled, decoupled and coupled design matrices are scrutinizable by the DRM and related concepts such as design set (DS), design row set (DRS) and design column set (DCS). Then, the DRM reconstruction algorithm and algorithm for selecting the unbiased reconstruction from reconstruction family members are presented based on reconstruct ability analysis. The DRM reconstruction algorithm is applicable in reverse engineering, design evaluation and improvement.

This paper investigates a category-based statistical language model for Persian continuous speech recognition. The language models are based on variable-length category-based n-grams. Instead of finding patterns among individual words, a language model may be designed to discover relationships between word categories. In this research, this has been accomplished in 3 steps; clustering words into groups, exploitation of the statistical language model employing tree data structure and its application to the recognition system. The most important advantage of this model has found to be its ability to return to correct path in situations where ordinary statistical modeling does not allow it.

The effect of discontinuities on the design of ornamental stone quarries can be evaluated by using IBSD or In Situ Block Size Distribution. This was practiced during a research work at Shahrood University. In this respect software was developed to assist quarry designers to have a better understanding in the assessment of the feasibility of the operation. The main function of the software is the analysis of the IBSD. Using the IBSD factor Kashkak ornamental stone quarry was selected as a case study. Scan line Sampling method was used to collect discontinuity data from the field and K-means method was used to cluster the discontinuities and classify the discontinuity sets. The results obtained from the application of the software can play a key role in making decision about the future of the mine.

This paper explains response surface methodology (RSM), a powerful collection of mathematical techniques, and discusses its role in optimization problems. Based on the optimization method, the existing studies are classified into three categories, namely, loss function, desirability function, and classical methods. Since the desirability function approach incorporates the decision maker's points of view in the analysis, it is considered as the primary method in this paper to determine the desirability function. An important aspect of the proposed method is its ability to incorporate the relationship among quality attributes and its flexibility to provide guidance to the decision maker (DM). The performance and efficiency of the proposed method is investigated via two numerical examples.