A. Saatchi, H. Yan, and S. J. Harris,
Volume 20, Issue 1 (7-2001)
Abstract
Zinc was electrodeposited from an acidic sulphate solution on commercial steel sheet substrates galvanostatically at 10, 20, and 100 mA/cm2. The steel substrates had an average roughness number of 1.34 microns and a high percentage of its grains had their (111) planes parallel to the plate surface. During electrodeposition at 10 mA/cm2, on some specimens, there was an intense potential fluctuation around –870 mV vs Saturated Calomel Electrode (SCE). During this period zinc hydroxide precipitated on the surface. After a certain time, the potential dropped to –1020 for zinc deposition. Zinc nuclei were seen to precipitate from zinc hydroxide. Increasing current density changed nucleation mode from progressive to instantaneous, and also changed the size, morphology, and texture of zinc deposits.
Keywords: Zinc Electroplating, Current Density, Morphology, Orientation
E. Esmailzadeh, H. R. Bahrampuri and N. Niksefat,
Volume 20, Issue 1 (7-2001)
Abstract
Articulated liquid cargo vehicles transporting inflammable fuels and dangerous chemical products require special consideration when traveling on urban roads or cruising at highway speeds. The road safety and handling of these kinds of vehicles may be adversely affected when negotiating sharp turns or travelling on slippery roads, which may result in either lateral instabilities or complete rollover of these tanker vehicles. Moreover, directional instabilities in these kinds of vehicle may also introduce an excessive yaw swing or may initiate the jack-
knifing of the articulated tanker trucks. In order to overcome the instabilities of these tanker vehicles, installation of lateral baffles in the form of separating walls in the tanker were considered. The static roll and yaw plane models of these vehicles including lateral translation of the liquid inside the tank were developed. Using the static roll model, the rollover threshold of the vehicle is analyzed and the effect of these separating walls on the stability of the vehicle is studied. The yaw plane model is then used to predict the transient response and stability of the tanker vehicle under various road maneuvers. The governing differential equations were solved numerically to obtain the simulation results and optimum values of the parameters.
Keywords: Tanker, Vehicle, Stability, vehicle dynamic, rollover, lateral baffles
S. Mirzaei, M. Saghaein - Nejad, V. Tahani and M. Moallem,
Volume 20, Issue 2 (4-2001)
Abstract
This paper introduces a novel passive suspension system for ground vehicles. This system is based on a flexible Electromagnetic Shock Absorber (EMSA). In the proposed system, efforts are made to a) select a high damping coefficient usable in a car b) determine Physical dimensions and geometry not much different from those of the mechanical shock absorbers and c) seletct EMSA weight and volume low enough for the core not to be saturated. A model is designed and developed followed by determining the dynamic equations for the model. The results from the simulation in a quarter car model are then compared with those from passive and active suspension systems.
Keywords: Active Suspension Systems, Electromagnetic damper, Finite Element method
S.samavi, V. Tahani and P. Khadivi,
Volume 20, Issue 2 (4-2001)
Abstract
Routing is one of the basic parts of a message passing multiprocessor system. The routing procedure has a great impact on the efficiency of a system. Neural algorithms that are currently in use for computer networks require a large number of neurons. If a specific topology of a multiprocessor network is considered, the number of neurons can be reduced. In this paper a new recurrent neural network and its energy function is introduced. This network requires a significantly smaller number of neurons compared to its counterparts. Also presented is the performance of this neural network.
Keywords: Routing, Multicomputer systems, Recurrent neural networks, Mesh interconnection networks.
M.e. Hamedani Golshan, H. Ghoudjehbaklou and H. Seifi,
Volume 20, Issue 2 (4-2001)
Abstract
Finding the collapse susceptible portion of a power system is one of the purposes of voltage stability analysis. This part which is a voltage control area is called the voltage weak area. Determining the weak area and adjecent voltage control areas has special importance in the improvement of voltage stability. Designing an on-line corrective control requires the voltage weak area to be determined by a sufficiently rapid and precise method. In this paper, a new algorithm based on assigning a vector to
each power system bus is presented. These vectors indicate buses conditions from the viewpoint of voltage stability. In this new method, using the clustering methods such as kohonen neural network, fuzzy C-Means algorithm and fuzzy kohonen algorithm, voltage control areas are determined The proposed method has advantages such as determining PV and PQ buses which belong to the weak area simultanously, under all operating conditions and without a need to system model. Also by comparing the results of applying clustering methods, it has been observed that, due to simplicity of implementation and precision of the results, the two dimensional kohonen neural network is a more suitable tool for clustering power system to voltage control areas than the fuzzy C-Means and fuzzy kohonen methods.
Keywords: Voltage stability, Voltage weak area, Voltage control area, Corrective control, Pattern recognition, Kohonen neural network, Fuzzy C-Means algorithm, Fuzzy Kohonen algorithm.
F. Nateghi-A and N.a. Hosseinzadeh,
Volume 20, Issue 2 (4-2001)
Abstract
This paper presents a methodology for the assessment of ductility and strength capacities in low-rise buildings. This method utilizes the characteristics of force-displacement for the lowest story level or considers the weakest story in any given low-rise building for its primary analysis. Calculations are based on two levels of earthquake motions, namely strong earthquakes (PGA=0.3 g), and very strong earthquakes (PGA=0.45). Failure mechanism for the structure is established based on three criteria which are: a) bending mode, b) shear mode, and c) shear-bending mode. Evaluation is then performed using a five step procedure starting with a: modeling the building, b) developing the non-linear properties of the model, c) strength calculations, d) ductility calculations, and finally, e) assessing the safety of the building under consideration. All these evaluations are performed based on a matrix format, which simplifies the whole procedure. Developed equations and step-by-step procedure are presented and described in this paper Satisfactory results are obtained from the use of the method developed.
Keywords: Strength, Ductility, Failure mechanism, Low-Rise R. C. Buildings
N. Talebbeydokhti and M. Nikmanesh,
Volume 20, Issue 2 (4-2001)
Abstract
In this paper, longshore sediment transport in littoral zones is investigated. For investigation of sediment transport in the nearshore zone, the effects of waves, currents and topographical conditions of coast are considered. Linear wave theory was used for the investigation of the wave behaviour. Governing equations of littoral current are continuity and momentum ones. For calculating concentraion profile of suspended sediments at depth, the convection-diffusion equations must be solved.
A computer program called “PLSTP” (Prediction of Sediment Transpornt in Littoral Zones) is developed for investigation of sediment transport process in littoral zones. The finite difference method is used for solving governing equations. The results show a good agreement between this model and the measurements available.
Keywords: Littoral transport, Wave, Shore, current, sediment transport
M. Saffarzadeh and Gh. Masoumi,
Volume 20, Issue 2 (4-2001)
Abstract
In the process of the optimum design of aprons, solutions should be found for problems and such issues as the optimum area and dimensions of the apron, including the passenger and the cargo the number and dimensions of the gates on the basis of different types of aircraft parking configuration aircraft simulation and arrangement in different time periods of the given day at the airport. In this research, a mathematical model was developed for the analysis and design of airport aprons based on minimum transportation cost. Some of the parameters of transportation cost include user, capital, and operational costs. Moreover, based on the fundamentals of the mathematical model, a computerized simulation model was developed taking into consideration the actual parameters of design of airport aprons such as stochastic demand, passenger behaviour, and evaluation of analytical model. The results obtained from the computerized simulation model indicate that policies of the airport authorities and air carriers such as flight schedules, gate use strategy, the mix of aircraft fleet during the planning horizon, operational conditions, and economic cosiderations have significant impacts on the design of the aprons.
Keywords: Airpornt, Apron, Optimization, Design.
K. Eshghi and S. Pasalar,
Volume 20, Issue 2 (4-2001)
Abstract
Multicommodity distribution problem is one of the most interesting and useful models in mathematical programming due to its major role in distribution networks. The purpose of this paper is to describe and solve a special class of multicommodity distribution problems in which shipment of a commodity from a plant to a customer would go through different distribution centers. The problem is to determine which distribution centers to use so that all customer demands are satisfied, production capacities are not exceeded, and the total distribution cost is minimized.The proposed problem is formulated as a mixed integer linear program and a solution technique based on tabu search is developed, implemented and successfully applied to the test problems.
Keywords: Commodity Distribution Systems, Tabu Search, Mathematical Programming
S. M. Haeri, N. Sadati and R. Mahin-Rousta,
Volume 20, Issue 2 (4-2001)
Abstract
In this research, behaviour of clayey soils under triaxial loading is studied using Neural Network. The models have been prepared to predict the stress-strain behaviour of remolded clays under undrained condition. The advantage of the model developed is that simple parameters such as physical characteristics of soils like water content, fine content, Atterberg limits and so on, are used to model the stress-strain behaviour of clays under triaxial loading, without performing exact and time-consuming tests on samples.
Results from the network show that neural network is a good tool for prediction of stress-strain behaviour of clayey soils using simple physical characteristics of such soils
H. Z. Aashtiani and B. Hejazi,
Volume 20, Issue 2 (4-2001)
Abstract
Bus network design is an important problem in public transportation. A main step to this design is determining the number of required terminals and their locations. This is a special type of facility location problem, which is a time-consuming, large scale, combinatorial problem. In a previous attempt by the authors, this problem had been solved by GAMS, based on a branch and bound algorithm.
In this research, different techniques for solving the problem are investigated to choose the best one. One of these methods is Simulated Annealing (SA), which is an efficient algorithm for solving complex optimization problems. SA’s parameters vary from one problem to another. Here, for the bus terminal location problem, SA’s parameters are determined, then the problem is solved. Another algorithm is the Implicit Enumeration method.
In this paper, the results obtained from the above 3 techniques are compared. The criteria for this comparison are the CPU time and the accuracy of the solution. In all the cases studied, SA gave the most accurate results. Its CPU time is lower than the others, too. Solving the bus terminal location problem for the Mashhad network shows that SA is about 150 times faster than GAMS and 50 times faster than Implicit Enumeration. Moreover, bus terminal location problem for the network of the city of Tehran, which is a more difficult problem, has been solved by the SA algorithm successfully.
Keywords: Bus network, Lacation problem, Heuristic, Simulated Annealing, Implicit Enumeration
A. R. Pishehvar and H. Ahmadi Kia,
Volume 20, Issue 2 (4-2001)
Abstract
In this study, the missile staging process by implementing a side-injected jet is simulated numerically. The problem is considered to be axisymmetric and the thin shear layer approximation of Navier-Stokes equations along with an algebraic turbulence model is used in a quasi-static form for the calculations. The free stream corresponds to a very high altitude flight condition with a Mach number of 10 and an injected jet pressure ratio of about 63000. An explicit Godunov-type scheme is used in the calculations, which is second-order in time and space. Computations are performed on the attached and separated geometry for a range of distances between the body and the warhead. The intense interactions between the jet flow and the main free-stream and its overall influences on the warhead aerodynamic loading are finally demonstrated.
Keywords: Missile Staging, Jet Interaction flow, TVD Scheme, Riemann problem
A. Sabounchi and A. Hajian-Nejad,
Volume 20, Issue 2 (4-2001)
Abstract
The objective of this study is to find the temperature distribution of a slab as it moves through the pusher-type preheat furnaces. First, the imaginary planes method (IPM) as a new and applicable method for calculation of radiation heat transfer in industrial furnaces is studied, and the two-dimensional form of this method is used to calculate heat flux and temperature distribution in the furnace enclosure. Next, the equation for the conduction heat transfer in a finite-difference form is developed for slabs and, finally, using IPM to calculate heat flux distribution on slabs surface, temperature distribution is obtained in the steady state condition.
Keywords: Pusher-type preheat furnace, Finite difference, imaginary planes method
A. Shadaram, H. Khaleghi and M.s. Sadeghipour,
Volume 20, Issue 2 (4-2001)
Abstract
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
M. R. Soltani and A. R. Davari,
Volume 20, Issue 2 (4-2001)
Abstract
A wind tunnel investigation was performed to study the flow field over a 70° swept sharped edge delta wing model at high angles of attack. The experiments were conducted in the subsonic wind tunnel at the Department of Mechanical Engineering, Sharif University of Technology. Velocity profiles have been measured using a special pitot tube and hot wire anemometer at angles of attacks of 10 to 35 degrees and Reynolds numbers between 1.5 to 5´105 over half and a full model. From these studies the shape of the leading edge vortices as well as the turbulence intensity inside the vortices were obtained and analyzed. This study revealed a region of increased velocity highly tubulent flow at the vortex core. As a result, the lift will increase nonlinearly with angle of attack.
Keywords: Leading edge vortex, Turbulence Intensity, Delta Wing, Vortex Bursting, Vortex core
M. R. Modarres- Razavi, H. Niazmand and S. A. Mirbozorgi,
Volume 20, Issue 2 (4-2001)
Abstract
In this paper, the flow-field of an incompressible viscous flow past a solid-sphere at low Reynolds numbers (up to 270) is investigated numerically. In order to extend the capabilities of the finite volume method, the boundary (body) fitted coordinates (BFC) method is used. Transformation of the partial differential equations to algebraic relations is based on the finite-volume method with collocated variables arrangement. For solving the obtained algebraic relations, the TDMA in periodic state is used. To approximate the convective fluxes, the differencing scheme of Van leer is used and SIMPLEC handles the linkage between velocities and pressures. The verification of the code is checked by the analysis of flow past a solid sphere at low Reynolds numbers of 20 to 210. A good agreement is obtained between the present results and the available experimental and numerical data. The flow-field past a sphere at low Reynolds numbers of 210 to 270 shows that the steady non-axisymmetric regime is going to build up at the Reynolds number of 211.
Keywords: Solid-Sphere, Wake, Three Dimensional Analysis, Boundary Fitted Cordinates
G. A. Barani, M. J. Khanjani and J. Ahmad- Auli,
Volume 20, Issue 2 (4-2001)
Abstract
In recent years, installation of plates in canal beds have been considered for sedimentation control and bed load reduction at canal intake. These planes, called submerged vanes, are different in dimensions. They are installed at intakes in-group with reasonable distance from each other. Presence of these vanes at intakes initiate transverse shear stress on river bed and causes sediment transport in the transverse direction. Investigation of flow and sediment transport equations, along with different experiments on physical models, have resulted in a suitable range of sizes and distances for vane installation. But, the determination of optimum sizes and distances for vane installation so as to minimize sedimentation requires the use of optimization techniques.
In this study, the hydrodynamic and optimization models of the vane system are first introduced. As the flow and sediment transport governing equations at intakes was nonlinear, the feasible direction method is used. Optimum size of vanes, distances between them at longitudinal and transverse directions, and the angle of flow inclination have also been determined. The optimum quantities of vane parameters were used to calculate the river bed profile at intakes by Wang et. al. [1] procedure. Comparison of the obtained results with Wang el. al. [1] recommendations confirms the advantage of vanes instalation at optimum conditions to control sedimentation.
Keywords: Submerged Vanes, Feasible Direction, Intake and Sedimentation
V. Tahani, S. M. Saghaeian Nezhad and G. R. Arab,
Volume 21, Issue 1 (7-2002)
Abstract
Because of extreme local saturation at pole tips of excited phase and uncircular shape of rotor and stator, a Swithed Reluctance Motor (SRM) does not have a simple and accurate mathematical model. Therefore, the output control of this motor requires a robust controller which is not based on an accurate model of the process. Fuzzy controllers, to some extent, will satisfy these requirements. Teta-on and teta-off are controller outputs. The output of teta-off controller is a Variable Structure Controller (VSC) which contains two parts: coarse controller which is used when the speed error is large and its output causes large changes in teta-on angle. This part of the controller is similar to a fuzzy PI controller. The other part of the controller is a fine controller and is used when the speed error is low. The fine controller increases the speed of response and reduces the speed error to zero. This part is similar to a fuzzy I or PI controller. Finally, experimental results of no-load and underload speed controls are demonstrated. The fuzzy controller robustness to measurement noise and parameter uncertainty is also studied.
Keywords: Fuzzy Controller. SRM Variable Structure Controller
R. Keypour, H. Seifi, A. Yazdian,
Volume 21, Issue 1 (7-2002)
Abstract
In this paper, two algorithms have been developed for allocation and size determination of Active Power Filters (APF) in power systems. In the first algorithm, the objective is to minimize harmonic voltage distortion. The objective in the second algorithm is to minimize the new APF injection currents while satisfying harmonic standards. Genetic algorithm is proposed for these two optimization problems. The simulation results for an 18-bus system show the effectiveness of the genetic algorithm for these two optimization problems.
Keywords: Genetic Algorithm, Active Power Filter, Harmonics, Allocation, Optimization
F. Mokhatab Rafiee,
Volume 21, Issue 1 (7-2002)
Abstract
A Two-phase model for configuring a cellular manufacturing system is proposed. In phase (I), for the first time, number of cells is considered as a decision variable. In phase (II), pursing two different objectives, one minimization of underload and the other, maximization of similarity of parts within a group, the design procedure is performed. As one cannot have these two objects together, a heuristic algorithm based on cellular similarity coefficient and integration of two objects is proposed. The results confirmed that the proposed heuristic procedure has reasonable outcomes.
Keywords: manufacturing cell, cellular similarity coefficient, two-phase model, heuristic algorithm
