Journal of Advanced Materials in Engineering (Esteghlal)

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Using the highly recommended numerical techniques, a finite element computer code is developed to analyse the steady incompressible, laminar and turbulent flows in 2-D domains with complex geometry. The Petrov-Galerkin finite element formulation is adopted to avoid numerical oscillations. Turbulence is modeled using the two equation k-ω model. The discretized equations are written in the form of a set of nonlinear equations by block implicit method and are then linearized by the Newton-Raphson method. The set of linearized equations are, finally, solved Through Frontal method. This generates a full implicit solution. A few laminar and turbulent flow sample problems are solved using the code. Results obtained are in perfect agreement with those obtained from numerical and experimental works reported in the literature.

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The excess accumulation of water in lung interstitial or alveolar is called pulmonary edema which is caused by factors that upset the normal Starling balance in micro-circulation. Pulmonary edema disturbs the alveolar gas exchanges which are normally regulated by the respiratory system. Mathematical modelling of pulmonary edema may help to predict the lung conditions and the mechanisms involved in the formation of edema. With the help of lung anatomy and physiology, the properties of alveolar sheet were determined and the Starling forces were considered during pulmonary filtration. A nonlinear partial differential equation was solved for the blood pressure in alveolar sheet. The mathematical simulation of lymphatic pumps was obtained and the process of fluid accumulation under normal and abnormal conditions was investigated. The results indicate that the rate of edema formation is strongly related to lung blood pressured, serum protein concentration, and reflection coefficient physiological data also confirm the results from this study.

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A nonlinear model consisting “yaw, roll, longitudinal, lateral and pitch” has been developed in which, tire and suspension characteristics have been considered. Tire model is based on the elliptic concept and tire Calspan data. According to this tire model, cornering force and aligning moment are computed as a function of slip and camber (inclination) angles, normal load, tire adhesion characteristics and skid number. The effects of suspension systems and the component of lateral and longitudinal weight transfers, are considered. Finally the equations of motion are droven, vehicle handling behavior and effect of anti roll stiffness on handling characteristics are shown.

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The present work introduces a modified scheme for the solution of compressible 2-D full Navier-Stokes equations, using Flux Vector Splitting method. As a result of this modification, numerical diffusion is reduced. The computer code which is developed based on this algorithm can be used easily and accurately to analyze complex flow fields with discontinuity in properties, in cases such as shock wave boundary layer interactions. This scheme combines advantages of both Advective Upstream Splitting (AUSM) and Low Diffusion Flux Vector Splitting (LDFVS) Methods. To increase accuracy and monotonicity, the conservative variables are extrapolated at the cell interfaces by using the MUSCL approach with limiter. This algorithm has been used to solve four sample problems. It has been shown that the numerical diffusion has been reduced and the results are in good agreement with published numerical and/or experimental data. Keywords: Compressible Navier Stokes Equations, Flux Vector splitting, Advective upwind, Numerical diffusion

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Physical properties of cotton yarns are affected by the characteristics of cotton fibers such as fineness, length, maturity and strength. This relationship has been worked out by means of multivariable regression and stepwise method for an open-end spun (NeC 20) cotton yarn. Moreover, with the help of linear programming, it was made possible to determine the percentage of different cottons in the blend with the aim of reducing the yarn price to a minimum while keeping the yarn quality to a certain level.

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The use of roller compacted concrete (R.C.C) without conventional cover in important hydraulic structures is investigated through laboratory observation of abrasion phenomena sujected to high velocity flow and floating particles. The main parameters affecting abrasion and erosion resistance of R.C.C. studied in the present study include: "Mixed Hydraulic Mean Radius" (which collectively represents several different parameters such as shape, type of surface, fine and coarse aggregate ratio, mixture irregularity, and energy of compaction), water cement ratio, and age of R.C.C. samples. It should be noted that most references in this filed concentrate on conventional concrete abrasion with often soft surfaces. In the present study, however, research findings on abrasion-erosion resistance of R.C.C. and their applications in new investigations will be investigated using a new test device called "Evaluation of Concrete Resistance" designed by H. Bayat. The device works with several phase flows. Single and multivariate analyses of the results, graphs, and empirical relations are used to determine abrasion and erosion resistance in terms of the above parameters. It is expected that in future only one parameter, namely, the Mixture Hydraulic Mean Radius", will suffice for evaluating R.C.C. abrasion resistance.

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The mechanical behavior of cold rolled sheets is significantly related to residual stresses that arise from bending and unbending processes. Measurement of residual stresses is mostly limited to surface measurement techniques. Experimental determination of stress variation through thickness is difficult and time-consuming. This paper presents a closed form solution for residual stresses, in which the bending-unbending process is modeled as an elastic-plastic plane strain problem. An anisotropic material is assumed. To validate the analytical solution, finite element simulation is also demonstrated. This study is applicable to analysis of coiling-uncoiling, leveling and straightening processes.

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The aim of this investigation was to produce Ti47Al48Mn5 intermetallic compounds with different microstructures in order to study their oxidation behavior. The reason for selecting manganese as an alloying element was to enhance the toughness of the compound. Ti47Al48Mn5 alloys were obtained through mechanical alloying, cold pressing and heat treatment. XRD results showed that milling of the elemental powder mixture for 30 hours causes the formation of Al and Mn in Ti solid solution, while by increasing milling time up to 50 hours, amorphization of powder mixture occurs. To obtain duplex and fully lamellar microstructures, the mechanically alloyed powders were cold pressed and then heat treated at 1100 °C and 1400 °C in argon atmosphere for 50 hours, respectively. The results of the oxidation test at 1000 °C revealed that the different microstructures of Ti47Al48Mn5 alloy investigated in this study have little effect on the oxidation resistance, and similar oxidation mechanisms existed for the two microstructures.

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In the present study, the copper anode slime was leached in chloride media. Then, pregnant leach solution (PLS) was purified using solvent extraction method and Octanol-kerosene solution. HAuCl4.2L was determined as the extracted macromolecule, and separation of impurities, such as copper, iron and selenium was done in the presence of gold. McCabe-Thiele diagram of Au–HCl (3 M)– Octanol (40% v/v) in O/A=3/4 showed that Au concentration in aqueous phase decreased from the initial value of 200 to 7 mg/L, after 5 stages. Ammonia solution was proposed as the stripper and McCabe-Thiele diagram was presented to obtain the number of gold stripping steps by ammonia solution