Sharif Digital Repository

Understanding of the effect of cementation on dynamic behaviour of cemented soil in an earthquake prone area could be crucial for earthquake resistance design. The major section of the city of Tehran has been developed on cemented coarse-grained alluvium. In order to understand the dynamic behaviour of this soil, a series of undrained cyclic triaxial tests were performed on uncemented and artificially calcite-cemented samples. In this paper, two dynamic parameters including dynamic shear modulus and damping ratio based on different definitions are investigated. In this regard the effects of cement content, confining pressure and cyclic deviatoric stress were studied as well. In general by... 

The low-cycle fatigue performance of shear panel damper (SPD) highly depends on the geometry of its shape and the criterion considered for its design. The main contribution of the current study is to find the optimum shape of the SPD subjected to cyclic loading by considering two different objective functions. The maximum equivalent plastic strain and the ratio of energy dissipation through plastic deformation to the maximum equivalent plastic strain are selected as the first and second objective functions, respectively. Since the optimization procedure requires high computational efforts, a hybrid computational approach is used to perform two paramount phases of estimating the inelastic... 

The ODYSSEY design methodology has been recently introduced as a viable solution to the increasing design complexity problem in the ASICs. It is an object-oriented design methodology which models a system in terms of its constituting objects and their corresponding method calls. Some of these methods are implemented in hardware; others are simply executed by a general purpose processor. One fundamental element of this methodology is a network on chip that implements method invocation for hardware-based method calls. However this network is prone to faults, thus errors on it may result into system failure. In this paper an architectural fault-tolerance enhancement to the ODYSSEY design... 

Numerical simulation of resin transfer molding (RTM) is known as a useful method to analyze the process before the mold is actually built. In thick parts, the resin flow is no longer two-dimensional and must be simulated in a fully three-dimensional space. This article presents numerical simulations of three-dimensional non-isothermal mold filling of the RTM process. The control volume/finite element method (CV/FEM) is used in this study. Numerical formulation for resin flow is based on the concept of nodal partial saturation at the flow front. This approach permits to include a transient term in the working equation, removing the need for calculation of time step to track the flow front in... 

The fracture mechanism of isotactic polypropylene has been studied by three- and four-point bending tests. The result of three-point bending test shows that a wide spread damage zone is present in front of the notch. Looking in more detail via cross-polarised light shows the evidence of birefringence in the stress-whitened zone. Increasing the applied load causes it to spread out the stress-whitened zone. Then the craze-like features are nucleated inside the stress-whitened region. The result of four-point bending test shows that craze-like damage appears in front of pre-crack and its propagation is dictated by spherulite microstructure. © 2003 Elsevier Science Ltd. All rights reserved  

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).... 

The main goal of this study is to further understanding of the role of rubber particles on deformation mechanisms in PP/EPR blend. For doing this standard tensile specimens were produced using injection molding. The results of microscopic evaluation of tensile specimen after some stretching show that damage forms in some points and then propagates in different directions. Also some elongated voids are observed, those are probably formed due to cavitation of rubber particles or debonding at the interface. With regard to achieved micrographs one may conclude that the deformation mechanism in PP/EPR blend can be massive dilatational shear banding due to repeated cavitation. © 2003 Elsevier Ltd.... 

We present and evaluate Deep Private-Feature Extractor (DPFE), a deep model which is trained and evaluated based on information theoretic constraints. Using the selective exchange of information between a user's device and a service provider, DPFE enables the user to prevent certain sensitive information from being shared with a service provider, while allowing them to extract approved information using their model. We introduce and utilize the log-rank privacy, a novel measure to assess the effectiveness of DPFE in removing sensitive information and compare different models based on their accuracy-privacy trade-off. We then implement and evaluate the performance of DPFE on smartphones to... 

A thorough understanding and accurate prediction of non-Newtonian fluid flow dynamics in rotating annular media are of paramount importance to numerous engineering applications. This is in particular relevant to oil and gas industry where this type of flow could occur during, e.g., drilling, well completion, and enhanced oil recovery scenarios. Here, mathematically we report on physical-based (numerical) and data-driven (intelligent) modeling of three-dimensional laminar flow of non-Newtonian fluids driven by axial pressure gradient in annular media that consist of a coaxially rotating inner cylinder. We focus on the dynamics of pressure loss ratio (PLR)—the ratio of total pressure loss in... 

A destabilizing effect at pH 7 of sodium phosphate on several lipases immobilized via interfacial activation is shown in this work. This paper investigates if this destabilizing effect is extended to other inactivation conditions, immobilization protocols or even other immobilized enzymes (ficin, trypsin, β-galactosidase, β-glucosidase, laccase, glucose oxidase and catalase). As lipases, those from Candida antarctica (A and B), Candida rugosa and Rhizomucor miehei have been used. Results confirm the very negative effect of 100 mM sodium phosphate at pH 7.0 for the stability of all studied lipases immobilized on octyl agarose, while using glutaraldehyde-support the effect is smaller (still... 

Bridgehead C-H bond dissociation enthalpies of 105.7 ± 2.0, 102.9 ± 1.7, and 102.4 ± 1.9 kcal mol -1 for bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, and adamantane, respectively, were determined in the gas phase by making use of a thermodynamic cycle (i.e., BDE(R-H) = ΔH° acid(H-X) - IE(H •) + EA(X •)). These results are in good accord with high-level G3 theory calculations, and the experimental values along with G3 predictions for bicyclo[1.1.1]pentane, bicyclo[2.1.1]hexane, bicyclo[3.1.1]heptane, and bicyclo[4.2.1]nonane were found to correlate with the flexibility of the ring system. Rare examples of alkyl anions in the gas phase are also provided  

We use multifractal detrended fluctuation analysis (MF-DFA) to study the electrical discharge current fluctuations in plasma and show that it has multifractal properties and behaves as a weak anti-correlated process. Comparison of the MF-DFA results for the original series with those for the shuffled and surrogate series shows that correlation of the fluctuations is responsible for the multifractal nature of the electrical discharge current  

Despite the importance of deformation mechanisms on mechanical behavior of materials, not much attention is paid to this subject for glass-fiber/polypropylene (GF/PP) composite. Thus, it is noteworthy that it is the type of deformation mechanism that largely determines the energy absorbed prior to fracture. Hence, understanding this phenomenon is of great importance in analyzing the mechanical performance of this composite system. This paper aims to present a physical model for elucidating the role of short glass fibers and their adhesion to the matrix on the deformation behavior of polypropylene composites  

Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected when the light of remote stars crosses a Galactic - disk or halo - refractive medium such as a molecular cloud. We present the promising results of a test performed with the ESO-NTT, and consider its potential  

Since in a highly filled polymer, a major problem arises from non-uniformity of properties due to the poor dispersion of filler, the application of coupling agents have been directed to overcome this problem and also to enhance the mechanical performance of the composites by improving the adhesion at the interface. In this study, a comparison between two major coupling approaches is conducted: 1) Using PPgMA as a kind of compatibilizer which changes the nature of the matrix, 2) Using titanate coupling agent which takes action at the interface and reacts with hydroxyl groups at the inorganic filler surface, resulting in the formation of monomolecular layer on the inorganic surface to increase... 

Interaction of Carbon Nanotubes (CNTs) and nanovoids embedded in a metal matrix is studied comparatively. For this purpose, two nearby CNTs/nanovoids are modeled as two similar cylindrical inclusions/holes in an infinite matrix. The nonlocal stresses around the CNTs/nanovoids are obtained by applying the integral constitutive equation of the nonlocal elasticity to the stresses from the complex stress potential method. Also, in order to bring different nonlocality effects of dissimilar media into account, the influence function of the nonlocal elasticity is modified. Effects of the CNTs/nanovoids size and distance as well as far-field loading ratio on the stress state in the matrix are... 

The Vapour Assisted Petroleum Extraction (VAPEX) process, a newly developed Enhanced Heavy Oil Recovery process, is a promising EOR method for certain conventional non-fractured heavy oil sandstone reservoirs such as those in Canada, but its applicability on low permeable Naturally Fractured Reservoirs (NFR) such as those in the Middle East and Persian Gulf still remained as a question. Previous studies show that the foremost concern for VAPEX application in the case of NFR is the low non-economical production rates. The aim of the present work is to study the effect of fractures geometrical properties such as orientation (vertical or horizontal), density, spacing, location and networking on... 

Stress distribution in Carbon Nanotube (CNT) reinforced composites is studied using nonlocal theory of elasticity. Two nearby CNTs are modeled as two circular inclusions embedded in an infinite elastic medium, and classical stresses are obtained using the complex stress potential method. Nonlocal stresses are calculated using nonlocal integral elasticity equation. Effects of the distance between CNTs as well as effects of the nonlocal parameters on the stress distribution and stress concentration are studied. For unit normal stress at infinity, stress at the interface of the CNT and matrix increases from 0.1 for classical analysis to 0.85 for nonlocal analysis. Furthermore, when two CNTs... 

Most condensate gas reservoirs discovered in Iran are rich in intermediate components. The phase diagram of these fluids is essential for reservoir management. The available commercial reservoir fluid simulators are not able to find the critical point of some of these condensate gas reservoirs to obtain the phase diagram quality lines. The quality lines of these reservoir's samples can be obtained experimentally using the constant mass expansion test data. The authors present experimental development of gas condensate phase diagram along with retrograde condensation and revaporization characterization during the reservoir depletion process of one Iranian condensate gas reservoir  

The top-down in situ combustion (ISC) involves the stable propagation of the combustion front from the top vertical injector to the bottom horizontal producer. Apart from laboratory studies in conventional sandstones, no application of the process in fractured carbonates has been addressed yet. The authors modified a successful combustion tube history matched model of an Iranian low-permeable heavy oil reservoir called Kuh-E-Mond to investigate the feasibility of ISC in fractured carbonate reservoirs mimicking block-scale combustion cells. Effects of fractured geometrical properties such as orientation, location, extension, density, spacing, and dispersion were considered. Results confirmed...