Sharif Digital Repository

A method for simultaneous phase identification and equilibrium calculations is put forward and applied on the highly nonlinear multiphase reactive distillation calculations. The method is based on modifying mole fraction summation equations. In the proposed methodology phase identification, phase equilibrium, and chemical reaction equilibrium calculations can be performed simultaneously and effectively. Simulation and optimization of equilibrium reactive distillation can be done efficiently using this approach. The methodology has been verified with the help of case studies. The method provides phases actually present at equilibrium, their quantities and compositions in each stage of the... 

Previous researches have shown the success of using reinforcement learning in solving combinatorial optimization problems. The main idea of these methods is to learn (near) optimal evaluation function to improve local searches and find (near) optimal solutions. Stage algorithm introduced by Boyan & Moore, is one of the most important algorithm in this area. In the other hand fuzzy methods have been used in all fields of science to solve problems but still never used in combinatorial optimization problems. In this paper we focus on Bin Packing Problem. We introduce two basic fuzzy algorithms (ALM and IDS) and then solve our problem with these fuzzy algorithms. We run ALM and IDS algorithms on... 

A process cycle of resin transfer molding (RTM) consists of two sequential stages, i.e. filling and curing stages. These two stages are interrelated in non-isothermal processes so that the curing stage is dominated by the resin flow as well as temperature and conversion distributions during the filling stage. Therefore, it is necessary to take into account both filling and curing stages to analyze the process cycle accurately. In this paper, a full three-dimensional process cycle simulation of RTM is performed. Full three-dimensional analysis is necessary for thick parts or parts having complex shape. A computer code is developed based on the control volume/finite element method (CV/FEM).... 

We study the kidney market in Iran. The most effective treatment for end-stage renal disease is a kidney transplant. While the supply of cadaveric kidneys is limited, the debate has been focused on the effects of the existence of a free market for human organs. Economists as well as medical and legal researchers are divided over the issue. Iran has a unique kidney market which has been in place for over 20 years, frequently reporting surprising success in reducing the waiting list for kidneys. This paper demonstrates how the Iranian system works  

Concrete arch dam is a complex geometric structure and designing such a structure requires experience and high knowledge. One of the important parameters in designing concrete arch dams is the tensile stress in arch concrete material. The static analysis results of high arch dam structure depend on structure analysis model, intensively. Stage construction is needed to be focused in modeling high arch dams. In this study, the necessity of considering stage construction in static analysis of dam structure is focused. Modeling stage construction uses Birth and Death technique of elements. Therefore, six stage construction models are provided including applying dam wall weight outright, two... 

This paper attempts to calculate column shortening and differential shortening between columns and walls in concrete frames using a nonlinear staged construction analysis based on the Dirichlet series and direct integration methods. Prototype frame structures are idealized as two-dimensional and the finite element method (FEM) is used to calculate the creep and shrinkage strains. It is verified with respect to published experimental and analytical results. B3 model and methods such as AAEM, EMM, IDM, and RCM are used for verification purposes. For each frame, effects of creep and shrinkage parameters such as relative humidity percent, rate of construction, shrinkage parameter, and concrete... 

The present study is concerned with introducing a new configuration of equal channel angular extrusion (ECAE) process nominated as multi-stage ECAE. This die configuration is not a real processing die and is just used to calculate strain in ECAE dies with outer curved corner. A solution is presented for evaluating total strain in those dies consisting of two or more ECAE sub-dies. The solution is extended for calculating strain in frictionless ECAE dies with outer curved corner. A complete agreement is found between calculated and previously published results by other authors. © 2006 Elsevier B.V. All rights reserved  

The effect of one of the surfactants such as Tiron, a compound based on the benzene molecule, on the morphology and chemical composition of zinc oxide deposits, produced from a zinc complex solution using two-stage chemical deposition (TSCD) technique, has been investigated. TSCD technique is a novel and simple chemical route for the deposition of ZnO film from aqueous solution. Zinc oxide films deposited on high purity alumina (HPA) as a substrate. The results show that the addition of Tiron changes the surface morphology and causes to form the fine-grained structure. With a dense and nodular-shape appearance, the film produced from the precursor of zinc complex-containing Tiron, is... 

A 1-V CMOS current steering digital to analog converter with enhanced static and dynamic linearity is presented. The 14-bit static linearity is achieved by a novel background analog self calibration technique which is suitable for low voltage applications and does not require error measurement and correction circuits. To improve dynamic linearity at high frequencies, a new low power track/attenuate output stage is used at the DAC output. Integral and differential nonlinearities of the proposed DAC corresponding, to 14-bit specification are less than 0.35LSB and 0.25LSB, respectively. The DAC is functional up to 400MS/S with SFDR better than 71dB in the Nyquist band. The circuit has been... 

A new architecture for constant-gm rail-to-rail(R-R) input stages is presented that has less than 5% deviation in gm over the entire range of the input common-mode voltage. Furthermore, a new structure for folded cascode amplifier based on the use of a floating current source is presented. Employing these techniques a low-power operational transconductance amplifier(OTA) with 100MHz unity-gain bandwidth, 106dB gain, 60° phase margin, 2.65V swing, and 6.4nVA/√Hz input-referred noise with R-R input common-mode range is realized in a 0.8μm CMOS technology. This amplifier dissipates 10mW from a 3V power supply  

This study investigates validity of continuity assumption of error terms underlying multiple linear regression approach of trip generation models for infrequent trips. Since not many household members make daily trips for purposes like shopping or personal business, estimation of such trips with their discrete and non- negative nature and still close to zero averages, using conventional multiple linear regression, needs to be investigated. This study employs a two-stage trip generation model; the probability of making/not making trip is modeled first by binary probit, then, number of trips for those who have already made trips are estimated by the weighted least square method. The results... 

The inverse solution is helpful to determine the drawability of a part and drawing parameters at the initial design stage. The usual inverse algorithms consider the drawing process that occurs in one step and therefore they are not able to analyze the processes which need more than one drawing step. Therefore, multistep inverse solution has been used for such problems. The multistep inverse solution deals with finding the initial guesses of nodal positions on intermediate stages and solving inverse equations between two consecutive steps. In this paper, a new mapping method has been developed to find the initial nodal positions on intermediate stages and the unfolding technique has been... 

Over the time, multistaging has proved to have some great benefits such as less electrical usage, so, nowadays; optimization of the electrical power usage in centrifugal compressors is an important issue to lead to the least usage of power. In this paper, we present a novel algorithm that provides this desire; it also shows different arrangement of the stages for the considered compressor. Simple single-stage compressor pressure ratio is normally limited by constraints of both aerodynamic and structural types. Reaching to minimum power leads to the least usage of electrical power. In this paper, we utilize theoretical relations which are extracted and have been presented a novel numerical... 

Solving the facility layout problems by graph theory consists of two stages. In the first stage, a planar graph that specifies desired adjacencies is obtained and in the second stage, a block layout is achieved from the planar graph. In this paper, we introduce face area as a new concept for constructing a block layout. Based on this idea, we present a new algorithm for constructing block layout from a maximal planar graph (MPG). This MPG must be generated from deltahedron heuristic. Constructed block layout by this algorithm satisfies all of adjacency and area requirements  

A multi-stage secret sharing (MSS) scheme is a method of sharing a number of secrets among a set of participants, such that any authorized subset of participants could recover one secret in every stage. The first MSS scheme was proposed by He and Dawson in 1994, based on Shamir's well-known secret sharing scheme and one-way functions. Several other schemes based on different methods have been proposed since then. In this paper, the authors propose an MSS scheme using All-Or-Nothing Transform (AONT) approach. An AONT is an invertible map with the property that having "almost all" bits of its output, one could not obtain any information about the input. This characteristic is employed in the... 

A methodology for controlling three phase PFC Sepic converter is presented, and behavior of the system is evaluated. The converter is connected in delta at the input and parallel at the output side, and is controlled by variable hysteresis current control method. By this approach, the current drawn by each of the individual converters is controlled to be in phase with its own input voltage. Detailed design criteria for the power and control stages of the single-phase SEPIC converter are presented and effects of this method on THD are verified  

In recent years, end-to-end approaches to automatic speech recognition have received considerable attention as they are much faster in terms of preparing resources. However, conventional multistage approaches, which rely on a pipeline of training hidden Markov models (HMM)-GMM models and tree-building steps still give the state-of-the-art results on most databases. In this study, we investigate flat-start one-stage training of neural networks using lattice-free maximum mutual information (LF-MMI) objective function with HMM for large vocabulary continuous speech recognition. We thoroughly look into different issues that arise in such a setup and propose a standalone system, which achieves... 

A low-power comparator is presented. pMOS transistors are used at the input of the preamplifier of the comparator as well as the latch stage. Both stages are controlled by a special local clock generator. At the evaluation phase, the latch is activated with a delay to achieve enough preamplification gain and avoid excess power consumption. Meanwhile, small cross-coupled transistors increase the preamplifier gain and decrease the input common mode of the latch to strongly turn on the pMOS transistors (at the latch input) and reduce the delay. Unlike the conventional comparator, the proposed structure let us set the optimum delay for preamplification and avoid excess power consumption. The... 

The optimal feeder design in gravity casting processes is considered. The design problem is formulated as an additive, growth-like, evolutionary topology optimization problem. The initial design of the presented method is a casting part which is placed in a suitable environmental mould box. The method is composed of three stages: determining the feeder-neck connection point on the casting surface, constructing the feeder-neck and the feeder growth. During the growth stage, the feeder topology is changed gradually until satisfying some predefined criteria. The design of multiple feeders is also considered in this work. In the presented method, feeders are designed in a descending order of...