Sharif Digital Repository

Base isolation is an acknowledged means to reduce the transmission of earthquake accelerations from the ground into the structure. Of particular interest here are systems where the bearing slides on a concave surface which produces a self-centering force restoring the building to its original position. While the idea behind the technology is straightforward, the numerical simulation of the structural response is difficult, since the contact between the bearing and the sliding surface changes continually between sticking and sliding in a nonlinear process. The research presented here aims at developing a computational model for base-isolated building which would allow the engineer to simulate... 

To date various commercial systems have been used in the GAIT analysis. These systems have some difficulties for clinical use, such as interfering with normal movement and high prices. The possibility of utilization of Kinect as a sensor for GAIT analysis has been studied in this research. The accuracy of Kinect in calculation of GAIT parameters such as lower limb joint angles, stride time, and stride length were computed during normal walking. The effects of the sensor's position and direction relative to the walkway were also investigated. The Kinect sensor was installed at different positions toward the motion path. In each position the data was recorded by both Kinect and a commercial... 

An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading  

The use of 1,3-bis(N-heterocyclic)carbene ligands with different alkyl wingtip groups (alkyl = methyl, isopropyl and tert-butyl) is an effective method for the palladium-catalysed direct S-arylation of methylphenyl sulfoxide and C-C coupling of various of aryl halides with alkenes. The reactions proceed in moderate to good yields. Interestingly, it is shown experimentally that, by using bulkier bidentate N-heterocyclic carbene ligands, more selective catalytic systems towards cis products in Heck coupling reactions can be achieved  

In quantum approaches to consciousness, the authors try to propose a model and mechanism for the mind-brain interaction using modern physics and some quantum concepts which do not exist in the classical physics. The independent effect of mind on the brain has been one of the challenging issues in the history of science and philosophy. In some recent mind-brain interaction models, the direct influence of mind on matter is either not accepted (as in Stapp's model) or not clear, and there have not been any clear mechanism for it (as in Penrose-Hameroff's model or in Eccles's model). In this manuscript we propose a model and mechanism for mind's effect on the matter using an extended Bohmian... 

In quantum approaches to consciousness, the authors try to propose a model and mechanism for the mind-brain interaction using modern physics and some quantum concepts which do not exist in the classical physics. The independent effect of mind on the brain has been one of the challenging issues in the history of science and philosophy. In some recent mind-brain interaction models, the direct influence of mind on matter is either not accepted (as in Stapp's model) or not clear, and there have not been any clear mechanism for it (as in Penrose-Hameroff's model or in Eccles's model). In this manuscript we propose a model and mechanism for mind's effect on the matter using an extended Bohmian... 

Power and bandwidth constraints are two major challenges in wireless sensor networks. Since a considerable amount of energy in sensor networks is consumed for data transmission, compression techniques may prolong the life of such networks. Moreover, with fewer bits to transmit, the network can cope better with the problem of inadequate bandwidth. In this paper, we consider an image sensor network and propose a paradigm based on the principles of Distributed Source Coding (DSC) for efficient compression. Our method relies on high correlation between the sensor nodes. The algorithm consists of two phases: the Training Phase and the Main Phase. In the Training Phase an aggregation node or a... 

The use of 1,3-bis(N-heterocyclic)carbene ligands with different alkyl wingtip groups (alkyl = methyl, isopropyl and tert-butyl) is an effective method for the palladium-catalysed direct S-arylation of methylphenyl sulfoxide and C–C coupling of various of aryl halides with alkenes. The reactions proceed in moderate to good yields. Interestingly, it is shown experimentally that, by using bulkier bidentate N-heterocyclic carbene ligands, more selective catalytic systems towards cis products in Heck coupling reactions can be achieved. Copyright © 2016 John Wiley & Sons, Ltd  

The 2,6-bis(diphenylphosphino)pyridine/palladium catalytic system successfully catalyzes the Heck coupling reaction of less reactive aryl chlorides as well as aryl bromides with styrene to give the corresponding olefins in reasonable yields. TBAB (tetrabutylammoniumbromide) as an additive was found to be essential for these reactions. The results of Heck reaction exhibited a high selectivity (>99/1) favoring the trans product  

An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading  

The use of commercially available 2,6-bis(diphenylphosphino)pyridine as a ligand in conjunction with K2CO3, DMAc and TBAB is an effective method for the palladium-catalyzed CN coupling of a variety of aryl halides with anilines, N-heterocyclic aromatic amines, and a cyclic secondary amine. The reactions proceed in good to excellent yield (up to 98%) while the loading of Pd(OAc)2 was as low as 0.025 mol %  

Motivated by recent laboratory and field observations, this paper reports the first quantitative measurements of the stabilization phase of interfacial instability in a two-layer fluid in surface wave motion. The instability results from the formation of a resonant triad between the surface wave and noise-level sub-harmonic interfacial waves. To exclude the effects of interfacial mixing on the interaction, the experiments were carried out with immiscible fluids. Carrying out a resonant interaction analysis to the third order of nonlinearity using a Lagrangian formulation, we also show for the first time that the three-wave resonance is inherently accompanied by a harmonic four-wave resonant... 

The reactions of the bis-NHC platinum complex cis-[PtMe2(bis–NHC–1)], 1, in which bis–NHC–1 = 1,1′-methylene-3,3′-bis[(N-(tert-butyl)imidazole-2-ylidene], with strong acids and thermolysis of the reaction products were investigated. The reaction of 1 with 1 equiv B(C6F5)3 in acetone gave the borate complex cis-PtMe(bis–NHC–1)[OHB(C6F5)3], 2, that undergoes C–H bond activation of one of the tBu wingtips at 50 °C and yields the cyclometalated platinum complex Pt(bis–NHC–1′)[OHB(C6F5)3], 3, (where the prime denotes the cyclometalated ligand). However, the migration of two C6F5 groups from boron to the platinum center was observed when the thermolysis of 3 carried out in the presence of a large... 

In this paper, we consider a relay-assisted uplink non-orthogonal multiple access (NOMA) system where two radio frequency (RF) users are grouped for simultaneous transmission, over each resource block, to an intermediate relay which forwards the amplified version of the users' aggregated signals in the presence of multiuser interference to a relatively far destination. In order to cope with the users' ever-increasing desire for higher data rates, a high-throughput free-space optics (FSO) link is employed as the relay-destination backhaul link. Dynamic-order decoding is employed at the destination to determine the priority of the users based on their instantaneous channel state information... 

Optimized and informed design of impinging jets can effectively enhance their rate of heat transfer. One practical pathway for such designing is to add nanoparticles to a background fluid. Here, we determine the effects of nanoparticle chemistry, their size, and their total volume fraction in water on the rate of heat transfer. We perform a comprehensive optimization using artificial neural network (ANN) and genetic algorithm (GA) to systematically study the enhanced heat transfer in nanofluids compared to pure water in obtaining a uniform cooling on a constantly heated surface in a turbulent flow. Our results indicate that increasing the size and concentration of nanoparticles enhances the... 

This work takes a new approach to solving non-hydrostatic equations of layered flows over bottom topography. A perturbation technique is used to find explicit expressions for a flow for different regimes of single- and two-layer flows over a sill. Excellent agreement with previous solutions and experimental data is obtained, and more details of the non-hydrostatic flow over a sill are revealed. The proposed method is simple and compact and removes the need for complex numerical techniques to solve the non-hydrostatic equations. It is shown that in the approach-controlled regime of two-layer flow over a sill, the flow upstream and farther downstream the sill crest can be described by the... 

This study is concerned with numerical modeling of viscous surface wave motion using boundary element method (BEM). The equations of motion for thin boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the viscosity-related quantities such as wave damping rate, shear stress, and velocity distribution inside the boundary layer. The technique is presented for standing surface wave motion. An excellent agreement is obtained between the numerical predictions and the previous results. The extension to other free surface problems is straightforward. © 2005 Elsevier Ltd. All rights reserved  

An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to model the wave motion and the corresponding boundary layer flow. A mixing-length theory is used for turbulence modelling. The model results are in good agreement with previous physical and numerical experiments. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 John Wiley & Sons, Ltd  

This study is concerned with evolution of selective withdrawal of a linearly stratified fluid through a line sink at the base of a reservoir with bottom topography in the form of a sill of small height. The problem is investigated theoretically in the linear, inviscid limit using a perturbation technique. The induced flow due to motion of the first few shear waves is studied. It is shown that the effect of a sill on the flow field is confined mostly to the withdrawal layer in the vicinity of the sill. Equations are proposed for the steady withdrawal layer thickness and the critical Froude number in the presence of a sill. © 2003 American Institute of Physics  

An effective numerical technique is presented to model turbulent motion of a standing surface wave in a tank. The equations of motion for turbulent boundary layers at the solid surfaces are coupled with the potential flow in the bulk of the fluid, and a mixed BEM-finite difference technique is used to obtain the wave and boundary layer characteristics such as bed shear stress. A mixing-length theory is used for turbulence modeling. Although the technique is presented for a standing surface wave, it can be easily applied to other free surface problems. Copyright © 2005 by ASME