Sharif Digital Repository

Due to the growing complexity of today's digital circuits, the speed of fault simulation has become increasingly important. Although critical path tracing (CPT) is faster than conventional methods, it is not fast enough for fault simulation of complex circuits with a large number of faults and tests. Exact stem analysis is the most important obstacle in accelerating the CPT method. The simplification of stem analysis eliminates time-consuming computations and makes the CPT method more parallelizable. An approximate and bit-parallel CPT algorithm is proposed for ultrafast fault simulation for both stuck-at-fault (SAF) and transition delay fault (TDF) models. Time linearity, speedup, and... 

Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME  

Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v̄2 - f model which show similarity. Also results show good agreement with experimental data... 

Density current is a dense fluid, which is continuously released from a source and spreads down a sloping surface inside a lighter, motionless fluid. A low-Reynolds number k-ε model (Launder and Sharma, 1974) has been used to simulate the behavior of 3-D density currents. Density current with a uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with the experimental data sets. Although the k-ε Launder and Sharma model is applied here to a conservative density current, it seems the analysis is valid in general for turbidity current laden with fine particles. Copyright © 2006 by ASME  

Dense underflows are continuous currents, which move down the slope due to the fact that, their density are heavier than ambient water. In turbidity currents the density differences arises from suspended solids. Vicinity of the wall make density currents and wall jets similar in some sense but Variation of density cause this flows more complex than wall jets. An improved form of 'near-wall' k-ε turbulence model is chosen which preserve all characteristics of both density and wall jet currents and a compression is made between them. Then the outcomes from low Reynolds number k-ε model is compared with v2̄-f model which show similarity. Also results show good agreement with experimental data... 

A CFD code has been developed to describe the salt solution density current, which propagates three-dimensionally in deep ambient water. The height and width of the dense layer are two dominated length scales in a 3-D structure of the density current. In experimental efforts, it is common to measure the height and width of this current via its brightness. Although there are analytical relations to calculate the current height in a two-dimensional flow, these relations cannot be used to identify the width and height of a 3-D density current, due to the existence of two unknown parameters. In the present model, the height and width of the dense layer are obtained by using the boundary layer... 

The gravity currents on the inclined boundaries are formed when the inflow fluid has a density difference with the ambient fluid and a tangential component of gravity becomes the driving force. If the density difference arises from the suspended particles, the currents are known as particle-laden density currents, or turbidity currents in which the local density depends on the concentration of particles. A low Reynolds k- Turbulent model is used to simulate three dimensional turbidity currents. Also some laboratory tests were conducted to study the 3D flow resulting from the release of particle laden density currents on a sloping surface in a channel of freshwater via a sluice gate. Kaolin... 

The authors consider the problem of finding a minimum cost multicast sub-graph based on network coding, where delay values associated with each link, limited buffer-size of the intermediate nodes and link capacity variations over time are taken into account. The authors consider static multicast (where membership of the multicast group remains constant for the duration of the connection) in lossless wireline networks. For such networks, first the continuous-time (asynchronous packet transmissions) model is formulated. Subsequently, the discrete-time model for the synchronous packet transmissions scenario is derived. Then, by using an auxiliary time-expanded network, a decentralised algorithm... 

The gravity currents on the inclined boundaries are formed when the inflow fluid has a density difference with the ambient fluid and a tangential component of gravity becomes the driving force. If the density difference arises from the suspension of particles, the currents are known as particle-driven density currents, in which the local density of the gravity current depends on the concentration of particles. A low Reynolds k-ε turbulence model is used to simulate three dimensional turbidity currents. Also a laboratory apparatus was built to study the 3D flow resulting from the release of particle laden density currents on a sloping surface in a channel of freshwater via a sluice gate and... 

Flows generated by density differences are called gravity or density currents which are generic features of many environmental flows. These currents are classified as the conservative and non-conservative flows whether the buoyancy flux is conserved or changed respectively. In this paper, a low Reynolds k-ε turbulence model is used to simulate three dimensional density and turbidity currents. Also, a series of experiments were conducted in a straight channel to study the characteristics of the non-conservative density current. In experiments, Kaolin was used as the suspended material. Comparisons are made between conservative and non-conservative's height, concentration and velocity profiles... 

In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3].the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000 has beeen found. A new dimensionless number introduced that indicates the theoretical relation between cosserat theory and... 

In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3].the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000 has beeen found. A new dimensionless number introduced that indicates the theoretical relation between cosserat theory and... 

In this paper, we consider the problem of Minimum-Cost Multicast (MCM) sub-graph optimization with network coding subject to uncertainty in link costs. A number of uncertainty sets such as ellipsoids and bounded polyhedral are taken into account. A robust optimization model is developed to obtain the optimal sub-graph by replacing an uncertain model of MCM by its Robust Counterpart (RC). Then, the analytic and computational optimization tools to obtain robust solutions of an uncertain MCM problem via solving the corresponding explicitly-stated convex RC program is developed and validated through simulations  

In present paper the theory of the micropolar fluid based on a Cosserat continuum model has been applied for analysis of Couette flow and turbulent flow through rough pipes. The obtained results for the velocity field have been compared with known results from experiments done by Reichardt at Max Plank institute for fluids in Gottingen [1,2] and analytical solution of the problem from Gradient theory by alizadeh[3] for couette problem and with known results from experiments done by Nikuradse (1932).the boundary condition used here was the no slip one and Trostel's slip boundary condition[4].a good agreement between experimental results and the results of the problem for Reynolds near 18000... 

Four 5-, 10-, 20- and 30-story moment frames, representing low-, mid-, and two high-rise structures, were subjected to a great number of idealized directivity pulses. The amplitudes and periods of pulses vary from 0.02 g to 1.0 g and 0.5 to 12 sec, respectively. Over 1400 nonlinear dynamic analyses of low- to high-rise moment frames were performed which were feasible through using modified fish-bone model. The distribution of interstory drift along the height was studied and two applied contours were proposed: (i) the maximum interstory drift contour, and (ii) the critical story contour. These contours were demonstrated versus the ratio of natural period of the structure to the pulse period... 

In this article singular points of a parallel manipulator are obtained based on a novel geometrical method. Here we introduce the constrained plain method (CPM) and some of its application in parallel mechanism. Given the definition of constraint plane (CP) and infinite constraint plane (ICP) the dependency conditions of constraints is achieved with the use of a new theorem based on the Ceva geometrical theorem. The direction of angular velocity of a body is achieved by having three ICPs with the use of another theorem. Finally, with the use of the above two novel theorems singularities of the 3UPF_PU mechanism are obtained. It should be emphasized that this method is completely geometrical,... 

An analytical model is proposed to study the effect of particle size on melting enthalpy and entropy of metallic nanoparticles (NPs). The Mott's and Regel's equations for melting entropy in the combination of core average coordination number (CAC) and surface average coordination number (SAC) of freestanding NPs are considered. Clusters of icosahedral (IC), body centered cubic (BCC), and body centered tetragonal (BCT) structure without any vacancies and defects are modeled. Using the variable coordination number made this model to be in good agreement with experimental and molecular dynamic (MD) results of different crystal structures. The model predicts melting entropy and enthalpy of... 

Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress... 

Adaptive Noise Cancellation (ANC) is a well-known technique for background noise reduction in automobile and vehicular environments. The noise fields in automobile and other vehicle interior obey the diffuse noise field model closely. On the other hand, the ANC does not provide sufficient noise reduction in the diffuse noise fields. In this paper, a new multistage post-filter is designed for ANC as a solution to diffuse noise conditions. The designed post-filter is a single channel Linear Prediction (LP) based speech enhancement system. The LP is performed by an adaptive lattice filter and attempts to extract speech components by using intermediate ANC signals. The post-filter has no... 

Self-Compacting Concrete (SCC) is a unique type of concrete that can flow and fill spaces without the need for vibrating compaction, resulting in a dense and uniform material. This article focuses on estimating the compressive strength of SCC utilizing Artificial Neural Networks. Specifically, the study employs multilayer perceptrons with back-propagation learning algorithms, which are commonly used in various problem-solving scenarios. The study covers essential components such as structure, algorithm, data preprocessing, over-fitting prevention, and sensitivity analysis in MLPs. The input variables considered in the research include water, fine aggregate, super-plasticizer, fly ash, coarse...