INTERNATIONAL JOURNAL OF INDUSTRIAL ENGINEERING AND PRODUCTION MANAGEMENT (IJIE) (INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE) (PERSIAN)
Year:2002 | Volume:12 | Issue:4|Papers Count:18

In this paper analytical experimental investigation of wrinkling of cone in the explosive forming is presented. An analytical method based on energy analysis is present which gives governing equation of wrinkling. Solution of this equation determines the number and initiation point of wrinkles, Effects of mechanical property and plate dimensions on wrinkling may be analyzed by this equation. The analytical results of this paper agree with the experimental results.

Film cooling technique is currently used in the gas turbine hot sections, such as the combustor wall and the turbine blades, to prevent those sections from failing at elevated temperatures. In the single hole film cooling method, coolant air is injected from a hole into the mainstream and thus the flow is naturally three dimensional. In this paper, the Navier - Stokes and the energy equations are solved on a flat plate by the finite Element method using cubic elements. Algebraic equations are obtained by the use of the Petrov-Galerkin method. The pressure term is vanished from the momentum equations, by employing the penalty method. The governing equations are transient and the flow is incompressible and turbulent. The model of turbulence in the near wall region is the wall function method, and in the fully turbulent region is the k-a model. The systems of the algebraic equations are solved by the Frontal method. The film cooling effectiveness data, at the optimum conditions, was directly compared with the experimental results of Goldstein et al. (1968), and a good agreement is demonstrated.

A parametric study has been performed on the leaching behavior of Iranian (Sarcheshme, Kerman, Iran) chalcopyrite concentrates in Ferric Chloride solution as leaching agent. Effects of leach solution concentration, leaching agent molar ratio, temperature, time, grain size, and air blowing have been studied. Stirring speed has been kept constant at 150 rpm. Maximum extraction of 95% for copper has been obtained under the optimum conditions of 2 hours leaching at 95°C with reagent (Ferric Chlorid) molar ratio of 2.35 and 614 g/l concentration. Kinetic analysis of the experimental data shows that under the conditions studied, mass transfer is the predominant mechanism in controlling the overall reaction rate.

One of the important issues in the message passing multiprocessors is the routing method. With the increase in the number of processors in these systems the probability of fault increases and the use of fault tolerant routing is inevitable. The classical fault tolerant routing schemes that have been used in the Mesh interconnection networks generally use the local information. This is because the local occupies less space and then the routing would require less computational efforts. With the today's technology, obtaining a memory for the global information on the interconnection faults is not difficult. But still, the amount of computational processes is an obstacle for using the global information in the fault tolerant routing. In this paper a new scheme, which is called the arc analysis, is introduced for the fault tolerant routing purposes in the Mesh interconnection networks. This new scheme, which uses global information, is capable of finding paths with the average shorter length than the classical algorithms.

In this research the effects of various parameters on design of composite peressure vessels are studied. For this purpose a composite pressure vessel is designed based on netting analysis approach. Then by using parameters obtained trom the analysis, a simplified model of the capsule is made by a finite element technique. In the next step, by optimizing the simplified model, effective parameters such as variable thickness of the composite shell, variation of the fiber angle in the cap area, and existence of flanges and metallic liner are studied in detail. The results obtainedf all three techniques (netting, simplified and modified models) are compared with each other.Using the modified model, yield pressure for the composite pressure vessel is calculated and the elasto-plastic behavior of metallic liner and propagation of plasticity in this component are studied. The composite material is assumed to be linear-elastic and the liner is considered as an elasto-plastic material. The stress and displacement fields obtained from the modified and netting models are compared. It is shown that netting analysis is not able to design an optimum pressure vessel.Finally, using a failure analysis approach, the first ply failure of the composite pressure vessel is analyzed for all three models. The results show that the magnitude of first ply failure pressure for the netting and simplified models is lower than that of the modified model. To design an optimum composite pressure vessel, all effective parameters studied in this research should be considered in design process.

In the present article, precipitated phases such as G.P zones, and other transitional phases, of the high temperature Super saturated of Zn- Al (40%)-Cu (2%), due to ageing process at l00oc for various times, have been investigated. T.E.M and S.T.E.M, were employed in order to achive the aformentioned goals.

Magnesite, after thermal treatment is mainly used as a refractory material in steel making, cement and nonferrous metals. Recent development of these industries in Iran has increased the demand for magnesia.The major magnesite deposits in Iran are located in the east and eastern south parts. Refractory production plant, erected in Birjand produces about 30,000 tpy dead burned magnesia. The high grade feed crushed, screened and the fraction finer than about 3 mm separated and disposed as tailing. It is too fine in size to be treated in the kiln. Also its free silica content is higher than the coarse fraction.The present work presents the results obtained for reduction free silica of a representative sample of the tailing dam by gravity and flotation methods.After characterisation of the sample, it was divided into various size fractions, on which heavy liquid tests were carried out. The results revealed that by means of a 2.8 gr/cm3 liquid a concentrate with 92.5% magnesite, 2.1% Sio2 and 3.7%CaO.Flotation tests were performed with cationic collectors in alkaline conditions. Initial results showed that desliming of the feed was essential. By using collectors . Initial A17 or A18 manufac tured by AKZO, a product containg more than 91% magnesite and less than 2% Sio2 . The briqueting of the concentrate is necessary to feed the klin.

In this paper a modified magnetic equivalent circuit approach is presented for the steady state and transient analysis of squirrel cage induction motor. The effects of all spatial harmonics, stator and rotor tooth reluctances, saturation effects, rotor skewing, air gap permeances and leakage permeance of slots, and type of winging connection are taken into account. Since there is no restriction on stator winding, rotor bar and air gap length symmetry this approach is able to model the induction motor under both healthy and faulty conditions. In the proposed model, by considering the actual dimensions of stator and rotor laminations, some simplifications have been considered. Hence, the number of variables in the system of algebraic of the system of algebraic equations improves and this leads to better convergence of numerical solution.

Characteristics of two-dimensional turbid density currents and the effects of their confining were experimentally investigated. Sedimentation rates of confined turbidity currents in 10% channel width were measured. Data show that at low bed slopes (less than 2%), two - dimensional density currents are laminar and subcritical and entrainment is low. Meanwhile coarser particles deposit at the bed continuously, silt and clay particles can suspend. Increasing in concentration and bed slope, decrease the height of density current and increase the average velocity. Confining of turbidity current increases the height and velocity in several times and can change the subcritical regime to supercritical flow. This can alter the flow from depositive to erosive. In this case, even at low bed slope, the flow might become supercritical and its turbulence and perturbation remains coarser particles in suspension. Sedimentation profiles of confined turbidity currents show that sedimentation mass was reduced considerably.

In this paper a least square numerical method is presented for the solution of the junction of cylindrical waveguides. First, the electromagnetic fields in the input, output and the aperture waveguides are expressed by their modal expansions. Then, using the boundary conditions on the tangential electric and magnetic fields over the waveguide junction, an error function is constructed which is a positive definite quadratic function of the modal amplitudes. The unique minimum point of this error function may be obtained by the inverse of a hermitian matrix. This method of least squares (MLS) is applied to parallel- plate and also rectangular waveguide junctions including conducting diaphrgms. The outputs from computer implementations are compared with the data in the literature. In the present version of MLS similar to the method of moments for the solution of waveguide junction problems, the phenomenon of relative convergence appears where the relative number of modes in various sections of the waveguide has a definite effect on convergence of the numerical methods and should be selected in proportions to the size of the waveguides. On the other hand, in the customary method of least squares, a weighting factor appears in the error functions [1], which has a definite effect on the solution and the conservation of power and reaction should be used to determind its correct value. Therefore, there is an uncertainty of the solution of the waveguide junction problems by the various versions of the method of least squares, and it is necessary to adopt appropriate measures to reduce errors.

Nowadays modifying specifications of bitumen propounded in form of a new subject in producing hot asphalt in the world.In Iran modifying of biumen can increase operative age of asphalt up to a noticeable level. This research wants to find modified bitumen producing mechanisms with polymers which have been produced in our country and then act a limit consideration about modified bitumens.A strong shear machine with controled equipment was designed and made for producing modified bitumens. This machine can remit the obtained product to the reliable adaptation under chronological coditione and proposed temperatur in each exam.Results from experiments and studies showed that polymer APP has improved such traits as penetration, softening point, viscosity, frass breaking point and ductility to an acceptable degree. Calculations of thermal sensitivity has put the improved tar at this research in the group of tars with little thermal sensitivity.

Diversion of some portion of river flow is possible in many ways. Apparently the most effective solution for diverting clear water is to keep botton material and course suspended silt out of the intake. Frontal intake are among the gravity river intakes which are suitable in mountain rivers which carry a large amount of large particle sediment as bed 10ad.In frontal intake ,a flow parallel to the river flow is established by designing a canal on one side of the river. The water is diverted from the side of this channel at the downstream end. The review of the literature reveals that the geometry of this canal has a significant role on both flow and sediment entry to the in take but this important issue has not been received the attention of the investigators. In this study by conducting an experimental hydraulic model of frontal intake with different geometry and flow discharge and two different sediment sizes, and conducting over 186 tests the criteria for design of the approaching canal are developed. It was found that for best performance and minimum bed sediment entry , flow velocity in the channel must be equal or less than the threshold velocity of bed sediments.

Power swing is one of the important dynamic phenomena that occur in power systems. It lasts for a time period ranging from one to seconds and causes distance protection maloperation. The oscillation of voltage and current variables, resulting from a fault on the system, causes the oscillation of the impedance sen by distance relays. The impedance may therefore enter the operating zones of the relay and causes unwanted tripping of healthy lines. This paper preating an algorithm for best method of maximum line loading in order to detemine the time settings for the power swing zone of distance relays used in 230kV and 400V transmission network of Fars Regional Power Company in Iran The effectiveness of the .algorithm has been tested by simulation studies on the network. The proposed methodology is described and time settings for selected relays of the network will be presented.

This paper discusses the scheduling and allocation of common and constrained resources of parallel projects with consideration of activities precedeuce’s to take maximum benefit of resources. At the present time the general problem of multi - project resource allocation is formulated as a zero- one programming and goal programming models [1,2]. But the complexity in the cited models would be highly increased when the size of projects will grow up. This complexity is especially important when the level of available resources varies during the project implementation. This paper tries to model the problem in the from of some subproblems of multidimensional knapsach kind. Then, a heuristic method is proposed to faciliate the solution of the problem. This method is capabable to obtain near– optimal solutions. To evaluate the accuracy of the proposed method, the numerical results gained by the method are compared with optimal values.

CA and CA2 are the principal anhydrous constituents of calcium aluminate cements. Once it hydrates, Crystals of CAHIO forms at low temperatures while C2AH8 at higher temperatures. Both hydrates converts to C3AH6 under certain circumstances. There are two proposed mechanisms for the beginning of the crystallization of cements. a) When Water is mixed with cement a suspension is formed and the solid begins to dissolve. By the time that the water has become saturated with calcium and aluminate ions, it is already super- saturated with respect to the formation of various calcium aluminate and alumina hydrates. These hydrates nucleate and grow, allowing more anhydrous cement to dissolve into the solution. This through- solution mechanism may lead to the formation of a strong microstructure of interlocking hydrate crystals.b) Once cement hydrates a kind of gel forms on the surface of the grain that depending on the temperature of hydration, the composition of the gel varies. At low temperatures (less than 20oC) it is calcium aluminate gel, while at higher temperatures it is reach from THE aluminum compounds. After the gel forms, the gydrates start to nucleate and growth of the crystals takes place and cenents sets.The mechanism of hydration was investigated by Transmission Electron Microscope and X - ray microanalyses.Results confirmed the hydration through the gel formation.

In this paper the problem of the adaptive parameter estimation of 2-D systems is defined, and a solution method based on identification model is presented for it. In this solution method, the system parameters are decomposed into two blocks, namely the horizontal and vertical blocks. The estimations of the horizontal and vertical blocks, which are the identification model adjustable parameters, are adjusted along the horizontal and vertical directions respectively. Thus a 2-D adaptive algorithm is obtained for estimating the 2-D systems parameters. The convergence (stability) of the 2-D algorithm is analyzed via 2-D layponov approach, and also the algorithm asymptotic stability conditions, that are the 2-D persistent excitation conditions, are obtained in terms of the system locally controllability and the system input generality. In the end of paper the effectiveness of the presented procedure is illustrated by computer simulation.