AMIRKABIR
Year:2003 | Volume:14 | Issue:53|Papers Count:37

Adsorption of p-Cresol by three different activated carbons was carried out at 301 K and at controlled pH conditions. Langmuir-Freundlich isotherm equations were studied and relative parameters were found. In acidic conditions that pH of solution is well below the pKa of p-cresol (in molecular form), it was observed that the adsorb ate solubility and the electron density of aromatic ring were the influencing factors on the extent of the adsorption by affecting the extent of London dispersion forces. It was found that the uptake of the molecular form of the aromatic solute was dependent on the PZC and surface area of the carbon. In higher solution pH conditions (in ionic form), the electrostatic forces played a significant role on the extent of adsorption. The effect of pH must be considered from its combined effects on the carbon surface and on the solute molecules. Adsorption capacity (Qmax) and affinity (K) decrease with pH. Adsorption of the solute in higher pH values was found to be dependent on the concentration of anionic form of the solute. All isotherms were fitted in to Langmuir-Freundlich isotherm equations to find the relative factors.

This paper deals with the problem of determining of an unknown coefficient in an inverse: elliptic boundary value problem. Using a nonconstant overspecified data, it has been shown that the: solution to this inverse problem exists and is unique.

This paper is intended to show the use of Discontinuous Deformation Analysis (DDA) in stability analysis of rock slopes. In general, static stability analysis methods for rock slopes mainly derived from the limit equilibrium concepts that are very tedious in computation and not safe for dynamic loading. The Discontinuous Deformation Analysis (DDA) method that has been developed by Shi is one of the most advanced methods that can be applied in this case. To improve the capability of the Shi's method to meet the requirements for analysis of rock slopes under earthquake loading, some improvements have been applied to the original program. The main improvements are time dependent (time history) loading, damping and energy loss for which some numerical examples are presented to show the capabilities of the modified program.

In this paper, using hierarchical control system, we have introduced a new method for control of double inverted pendulum. In this method first we separate the system into three sub-system and for each sub-systems we design a local controller which is independent from the others. Then, in the higher level considering the interaction between the sub-systems we design a supervisory control. (this is done by producing a number of weight function corresponding to our sub-systems). The results show that fuzzy controllers stabilize the system in a wide range of initial condition in about 20 to 24 seconds.

There are several geotechnical and geoenvironmental problems involve water flow through soils. The coefficient of permeability is the most important parameter that dominates the water flow pattern through soils, both in transient and steady state conditions. In the current paper the stress dependency of permeability and its effect on the ground water flow is evaluated. The results of a field instrumentation program to establish pore water pressure profile is presented and the dominant effect of stress dependent permeability characteristics of soil over ground water pressure and flow is demonstrated and compared with an analytical solution. Also, the procedure and results of a laboratory experimental work to evaluate stress dependency of permeability is elaborated. Finally, referring to the site and laboratory investigations the nature of stress dependent permeability of soil and the validity of the related equation are assessed.

The Theory Of Constraints Along With MRP-Ii And JIT Is Considered To Be A Fairly New Concept In Production Planning. The Implementation Of This Technique In Scheduling Is Called Drum Buffer Rope Scheduling (Dbrs) Where In A Multistage Production Planning, The Time Allocated For The I Entire Stages Is Considered To Be The Same As The Bottleneck Resource. In This Paper, We Use The Relationship Between Transfer Batches And Throughput In A Production System In Order To Develop A New Improved Concept For Dbrs To Result More Throughput In A Given Time Interval.

By adopting the concept of the probabilistic logic neuron which represents a class of RAM- based neural networks, this paper introduces a model-free optimization method called Ring Probabilistic Logic Neural Networks (RPLNN) that are more suitable for optimization problems. To highlight performance of the RPLNN, some different optimization problems are considered. The simulation results show that the Ring Probabilistic Logic Neural Networks remarkably outperform the conventional genetic algorithms and some gradient based methods as well.

In water resource development project, where separation of saline and nonsalin water resources is an important subject, saline water storages behind the earth dams may be an economical solution. in such cases, the long term effect of saline water on the soil parameters is a controlling factor. in this research, an apparatus which is able to apply higher hydro-static pressures was prepared. soil samples were selected from fine grained soil resources of ajichai project and both saline and semi-saline waters were jlowed through the samples. essential soil parameters were measured after a long termjlow in soil mechanics laboratory and were compared with original soil parameters. at least for selected soil samples smal improvement in engineering parameters of soil can be concluded.

A mathematical model for hydrogen recovery from a feed gas using a four-bed, ten step PSA system, is proposed. Methane and Carbon Monoxide is the impurities of the feed gas from which hydrogen is recovered. The numerical solution of the proposed model resulted in pressure, concentration and velocity profiles within the beds. Finally, the effect of some important  parameters such as adsorption pressure, cycle time, etc. are discussed and the optimum operational condition for this separation process is suggested.

In the present work the effect of simultaneous temperature and moisture on A. niger growth in the soild state fermentation was modeled. Experiments were designed as a two-factor design. Logistic model was used to calculate growth parameters in SSF. The results depicted tltat 35°C and 60% were optimum conditions respectively for cultural temperature of A. niger and wheat bran initial moisture. Two polynomial expressions were obtained to model the effect of temperature and moisture simultaneously on both µ m and Xm of A. niger were inoculated on steamed wheat bran.

In this paper crushing of honeycomb panels subjected to impact of cylindrical projectiles is i studied and the minimum velocity of projectile required for densification of panel is analytically determined. This study shows that the minimum impact velocity needed for panel densification is directly proportional to the cell wall thickness, the panel thickness and compressive yield strength of honeycomb material; and is inversely proportional to the cell size and projectile's mass. These results are in good agreement with the available experimental data.

Context dependent modelling is a well-known technique used to improve recognition rate in continuous speech recognition. However, it can also dramatically increase the overall system parameter count which usually leads to a grave problem known as sparse training data condition. Different techniques such as model parameter tying and MAP estimation are used to overcome this problem. In this paper, a new approach, namely weighted training, has been introduced which benefits from both MAP estimation and parameter tying strengths and also outperforms the widely used parameter tying approach. The trip hone models are used in this implementation.

This paper describes a new algorithm for solving the flow-shop scheduling problem to minimize maximum flow time on the base of combinational approach method. A set of randomly produced problems of different sizes was solved and compared with three well-known heuristics. The result reveals that the new algorithm improves the best heuristics in performance measures by a significant percentage. Also, since the number of necessary operations for solving problems in this algorithm is independent of the number of machines involved, it is apt for systems with large number of machines.

Various schemes are presented for on-line detection of turn faults in induction motor, but none of them deal with the magnitude of the fault ,or in other words, the number of short turns.this paper presents a novel scheme, for turn fault detection, based on parameter identification of a model in which the turn fault is considered. parameter identification is done by a genetic algorithm. by using this technique, in addition to fault detection, the exact magnitude of the fault is also determined. The scheme requires neither prior data collection nor turning for each specific motor, and at the same time is valid for motors with inverter supplies. Insensitivity of the technique to load variation, supply voltage variation and unbalanced supply voltage is shown by many experimental tests. necessary modification and validation of the model used for turn fault real number coded genetic algorithm, and schemes for its convergence speed up are other subjects discussed in this paper.

In this paper, the frequency and the time responses of a separated absorption and multiplication avalanche photodiode are studied by solving the carrier continuity equations, in the low gain regime. The discrepancy between the carrier velocities in different layers is considered for the first time. It is shown that considerable error occurs, if the device characteristics are calculated: assuming uniformly distributed velocities in the depletion layer, especially when the different layers have almost equal thickness

Thin-layer approximate engineering methods are used for calculation of in viscid hypersonic flows over blunt-nosed bodies. In these methods, the pressure is obtained using Maslen's pressure relation and the normal velocity component is calculated using an approximate relation which is not accurate enough in the leeward region. In this paper, a new relation for calculation of normal velocity has been derived from the continuity equation using thin shock layer assumptions. It has been shown that the present relation has critically improved the profiles of velocity in the leeward region. Results are presented for a cone at angle of attack and are compared with finite difference solutions of Euler equations. Since the method is fast, it can be used for preliminary design or parametric study of hypersonic vehicles.

In this article beside the review of the properties and specifications of the corrosion, abrasion and impact resistant coatings based on the Glass flake are studied, and one type of high solid epoxy- polyamide coating based on GF formulated and its chemical and electrochemical properties such as resistance against salt spray and electrochemical Impedance studied and result from the variation of the Glass-flake and silane coupling agent is illustrated in tables and figures. For better understanding of flakes orientatipon, electronic microscope photographs are also presented

In this article an improved procedure to identify people based on their iris features is proposed. These features are obtained from zero crossing of wavelet transform. The procedure has two step In the first of which. the gray level information .i in the second step, different are extracted as one dimensional. signals and representation of their zero crossing are produced. I in the second step. different irises are compared. To have computational efficiency and to be immune of noise. several level of wavelet transform in the mid band have been used. To make iris images independent of the location camera, they have been mapped to the double and dimensionless polar coordinate system. The proposed procedure has been applied on our image bank which contains both original and noisy images. The results show tlIat our proposed procedure is able to identify people in our data bank without any error

A two-dimensional Transmission line Matrix(TLM) method has been used to calculate the radiation pattern of three-dimensional antennas that are nearly cylindrical. By applying the Spectrum of 2-Dimensional Solutions method (S2DS), the three-dimensional field solutions can be obtained from numerically obtained two-dimensional solutions. This method has been employed on a linear array of longitudinal waveguide slots when radiating into an exterior structure and the results have been verified by measurements and other methods.

The basic part of a cooling dehumidifying system is the rotary desiccant wheel. Such a system is used in drying of gases and materials which are sensible to the heat. The use of rotary dehumidifier in desiccant cooling systems is investigated by analyzing the its performance. The rotary desiccant dehumidifier mathematical model was presented by using the mass and energy conservation equations. The optimum rotary velocity is an important parameter for achieving an optimum dehumidification. This parameter was obtained for a given system at optimum condition and also the relative humidity profiles of the air of exit of the system were determined.

A numerical model based on potential theory is developed for a two dimensional nonlinear water waves using the Cauchy boundary integral equation together with a Lagrangian time marching method for free water surface. This model can deal with stable deformations of free water surface.Applying this model, the forces exerted by waves on fixed or mobile objects can be computed

An axisymmetric approximate viscous shock layer method has been developed to calculate laminar and turbulent hypersonic viscous flows of perfect gas over blunt-nosed bodies. In this method, Maslen's second-order pressure expression has been used instead of the normal momentum equation to obtain a simplified form of the axisymmetric viscous shock layer equations. In this approach, equations have been solved in a shock-oriented curvilinear coordinate system. The shock shape is obtained using an inverse method which provides a smooth shock shape in subsonic and supersonic regions. It is noted that the approximate pressure relation is given in the stream function coordinate. Since the governing equations are solved in the computational coordinate system, the relation between these two coordinate systems must be specified In the present study an approximate relation between the computational and the stream function coordinate systems has been developed. This approximate relation, which is a third-order, polynomial, is derived using four boundary conditions on the shock and the body surfaces. The very first gain one can benefit from it is the increase of computation speed Since the present method fast, it can be used for preliminary design or parametric study of hypersonic vehicles. Solutions have been presented for air flows over spherically blunted cones. The results of present method compare very well with the experimental data and detailed viscous shock layer solutions.

This paper presents a numerical method for calculation of all inductances and their derivatives in  winding function model. The scheme substitutes manual function extraction for windings, inductances, and their derivatives. Also it has made it possible to implement any desired winding distribution including the actual one. It is shown when actual distribution is implemented, exact match of experimental data and simulation results is obtained, while otherwise significant error in simulation results especially in transient response, can be seen. The scheme has provided flexibility and simplicity for changing parameters and also has made it possible to achieve real time simulation.

The present investigation is concerned with the understanding of the effect of numerical dissipation on viscous supersonic flow variables. The numerical dissipation is added to the central difference scheme in order to control numerical instability and to enable the capturing of shock waves. Unfortunately, the dispersive nature of this scheme introduced oscillations around discontinuities. On the other hand, the upwind schemes perform well in these regions. But due to inherent dissipative property of upwind schemes, the accuracy of flow variables especially in high gradient region within the boundary layer can be deteriorated A systematic study is performed in order to investigate the effect of numerical dissipation used in the central difference scheme compared with upwind schemes. The viscous supersonic flow variables at the wall and their profiles computed based on "Roe", "TVD" and "Beam-Warming" methods are compared with each other in order to gain some insight about the effect of numerical dissipation. Moreover, the computed results; are compared with experimental data.

server ways of calculating non-Hermitian shape functions are considered. Also, disabilities of these techniques in generating triangular elements are mentioned. A direct method of behaviour understanding for finding shape functions of triangular element with side nodes is suggested. In addition, this technique is generalized to include internal nodes. Finally, suggested elements with these kinds of shape functions are evaluated numerically

Noise measurement in the optical communication systems is of great importance. In this paper, we analyze noises in a multi-mode semiconductor lasers considering the nonlinear gain and cross- saturation effect. Then, we measure relative intensity noise (RIN) and frequency noise spectrum (FNS) of a typical communication laser diode with special method using an optical spectrum analyzer. In two-mode semiconductor laser, mode partition noise is dominant. The results of analysis showed is observed that the total RIN is less than RIN of each mode, and also is decreased with higher mode numbers Intensity noises measurement of multi-mode semiconductor laser includes mode partition, mode hopping and relative intensity noises. Phase noise measurement include line width and phase/frequency noise spectrum Experimental and analysis results are in good agreement

For the wide use of concrete in different climates and consequently outbreak types of damages in concrete, attention to concrete durability has special importance. One of the most important damages in reinforced concrete structures is corrosion of steel. Chloride intrusion in concrete and carbonation are most common reasons of steel corrosion. The aim of the present study was investigation and comparison of durability of concrete specimens due to variation of water to cementitious ratio (W/CM), silica fume and slag percent and their components as cement replacement. Furthermore, the optimum percent of the aforementioned components to reach to a durable concrete against steel corrosion was intended to be determined. To reach to the mentioned aims, specimens were made in 0.5, 0.4 and 0.3 W/CM ratios with 52 mix proportions (468 specimens); which specimens in each W/CM ratio contained 0,20,35 and 50 percent of slag as cement replacement, while in each case, 0, 5, 10 and 15 percent of silica fume were used as cement replacement. In the current study, to obtain the best durability against steel corrosion, the optimum amounts of slag and silica fume in concrete were determined which will be presented in the full paper

in this research, the Iranian wool yarns were first mordanted with aluminium potassium sulphate, and then dyed with pomegranate shells. The dyed yarns were treated with different percentages of liquid ammonia solutions and some of the physical and chemical properties of the ammonia treated yarns were investigated. The UV-visible Spectrophotometer used to measure the absorbency of the remaining ammonia solution and FT-IR spectroscopy to observed the changes in the chemical structure of the yarn. Also wicking, light and wash fastness tests" were carried out on the pomegranate dyed yarns and the ammonia treated yarns. The surface characterization of the ammonia treated yarns were also investigated by the scanning electronic microscope and the j changes on the wool fiber surfaces were shown.

In the present work, reflectance values of acrylic fibers along their length and cross-section were predicted using a geometric model and its modified shape. Experimental and theoretical results were compared and the possibility of applying the model for predicting the reflectance value of fibers with different fitness and colour was investigated.To fulfill the requirements of theoretical work, an existed geometric model, which has been presented to predict the reflectance value along fiber length, was employed also, because of different geometric orientation of fibers in cross-section, that the output of the model and its modified shape is almost acceptable although the increase of transmitted material in fibers and high reflectance cause a difference between theoretical and experimental results

Researches on M/M/C Queuing models with triangular fuzzy parameters show that triangular fuzzy results for queue attributes provide large errors. In this paper, M/M/C queue attributes with fuzzy parameters that result in another triangular fuzzy are proposed and with simulation proved that results have more validity with lower error. Also, M/M/∞ quing models with triangular fuzzy parameters are discussed and new results of this models with numerical examples are showed.

Todays science and technology involves in identifying exact behavior and performance in engineering materials for the purpose of optimizing the material behavior: Classical models such as Tresca Vonmises Moher-Coloumb and Drucker-Prager are not able to present the actual behavwur of materials in high lateral stress positions: In this research an elasto-plastic cap model has been introduced to show the actual behavior of materials and asphalt concrete in various stress paths which include tensile shear and compression stress positions This behavioral model makes the numerical computations of structures easier and more exact for the sake of its own specifications This model conforms itself to the asphalt concrete properties and is in line with lab results and can be used satisfactorily in pavement anlyses and performance predictions Three subjects have been studied paralleltically and with constant follow-up in this research as under: 1- Giving a new behavioral model that is the difference between this model and the already existing cap models which is the non-occurrence of singularity at the cap and intersection Also the yield surface has here been formulated in such a way to make the cap and body tangent at intersection. 2- Writing a computer program namely POLYMAT using finite element method. This program can include various stress paths and also all different material behaviors such as elastic elasto- plastic visco elasto-plastic and overlay models .3- Back analysis and comparison between the results obtained from the model given and the other two models according to the lab results the back analysis shows more accurate conformation than the ADINA and NOSTRUM ones.

Production of Glutamic acid via fermentation of C. glutamicum was studied. Among the parameters which affect the bacterial growth and GA production, are the medium composition, dissolved oxygen and hydrodynamics. Therefore, effect of change in the broth constituents, rate of aeration and type of the bioreactor including shake flask, stirred bioreactors and airlift were investigated. At the first stage, in the shake flask, sugar consumption and biomass production was checked in the media based on beet and cane molasses. In the next step, a fed batch protocol in which a 12% ammonia solution was used to set the pH was studied in the stirred bioreactor. Following this, due to the too low sugar concentration at the onset of the production phase, double and mixed fed batch modes of operation in which aside from ammonia, molasses was fed to the fermenter at the specific rate was tested. In the stirred bioreactor, the best result in the mixed fed batch and at the optimum conditions namely aeration rate of 1.2 vvm and rotation speed of 500pm was as high as 10g/l of Glutamic acid. At the 3rd stage, result of the stirred bioreactor was compared against that of an Airlift fermenter. In the ALF. in the aeration rates from 1.2-3vvm, the best production was achieved in the maximum aeration as 18/l and the best production vs. energy Consumption was at the 2vvm aeration as 1989/energy. At the 2vvm aeration, production in the beet and cane molasses based media were compared in the ALF. The best result was obtained in the medoum based on cane molasses which was as high as 30g/l.