Sharif Digital Repository

In this paper, the Immersed Moving Boundary-Lattice Boltzmann (IMB-LB) method is compared with the single relaxation time and multiple-relaxation-time versions of the Immersed Boundary-Lattice Boltzmann (IB-LB) method in terms of the amount of numerical velocity slip produced on solid boundaries. The comparisons are performed for both straight and curved boundaries based on the effects of thickness of virtual domain used in the IB method for the first time, and relaxation time parameter(s) of the LB method. For the straight boundaries, a shear flow problem is studied while for the curved boundaries, a falling circular cylinder in an infinite channel is investigated. First, sensitivities of... 

Body force modeling is studied in the Generalized Newtonian (GN) fluid flow simulation using a single relaxation time lattice Boltzmann (LB) method. First, in a shear thickening Poiseuille flow, the necessity for studying body force modeling in the LB method is explained. Then, a parametric unified framework is constructed for the first time which is composed of a parametric LB model and its associated macroscopic dual equations in both steady state and transient simulations. This unified framework is used to compare the macroscopic behavior of different forcing models. Besides, using this unified framework, a new forcing model for steady state simulations is devised. Finally, by solving a... 

High-bainite dual phase (HBDP) steels with 34. vol.% ferrite were subjected to tensile strains of 1%, 3%, and 5% at intermediate temperatures (150-450. °C). Mechanical behavior of pre-deformed steels was then investigated at room temperature. A maximum value for both yield stress and ultimate tensile strength was observed for pre-deformed steels. A minimum elongation was also found in the same pre-deformed specimens at the range of 250-350. °C. It was found that dynamic strain aging (DSA) plays the major role in mechanical properties of pre-strained HBDP steels. The DSA indicator parameter (DSAP) was introduced to evaluate DSA mechanism. Maxima of DSAP were likewise observed at the range of... 

High-energy milling technique was used to synthesize Al-10 wt.%AlN-nanostructured composite powder in a planetary ball-mill under argon atmosphere up to 25 h. To show the role of AlN particles, process was conducted for monolithic aluminum. The changes in powder characteristics were investigated by time. Microstructure of powders was studied after different milling times by scanning electron microscope (SEM). The morphological evolutions showed that relative equiaxed powder could be synthesized after 25 h milling. Structural analysis was performed by X-ray diffraction method (XRD) to determine the grain sizes and lattice strain. Furthermore, particle size analysis (PSA) revealed the... 

We model the problem of assigning counsel to poor defendants as a matching problem. A novel aspect of this matching problem is the moral hazard component on the part of counsel. Within the model, we show that holding the total expenditure for counsel fixed and changing the matching procedure to accommodate defendants' and attorneys' preferences, i.e., switch from random matching to stable matching, defendants become worse offbecause a stable matching exacerbates the moral hazard problem on the part of counsel. In addition, we show that under suitable conditions random matching is the efficient way to allocate defendants to counsel. © 2018 American Economic Association  

This study presents a bilayer structure as a skin scaffold comprised of an electrospun sheet layer made of polycaprolactone and polyvinil alcohol and a porous hydrogel layer made of chitosan and gelatin. The hydrogel layer was fabricated by employing the freeze-gelation technique. The bilayer structure was achieved by pouring the hydrogel solution on the electrospun sheet at the bottom of a mold followed by the freeze-gelation technique to obtain a porous structure in the hydrogel. The hydrogel and hydrogel-electrospun samples were characterized by scanning electron microscopy, swelling, tensile strength, in vitro and in vivo analyses. From a mechanical strength standpoint, the combination... 

In this paper, a novel, A-shaped microrobot with nanometric resolution for precision positioning applications is addressed. The locomotion concept of the mechanism is founded on the "friction drive principle". To achieve the translational motion, a stack piezoelectric actuates the microrobot near its natural frequency. The dynamic modeling of the mechanism is based on the assumptions of linear behavior of piezo stack actuator and Coulomb friction model at contact points. The suitability of three simple, friction-based locomotion modes for implementation on the proposed device is presented. Influences of different friction coefficients on the behavior of the microrobot, with respect to... 

Advanced Encryption Standard (AES) is the most popular symmetric encryption method, which encrypts streams of data by using symmetric keys. The current preferable AES architectures employ effective methods to achieve two important goals: protection against power analysis attacks and high-throughput. Based on a different architectural point of view, we implement a particular parallel architecture for the latter goal, which is capable of implementing a more efficient pipelining in field-programmable gate array (FPGA). In this regard, all intermediate registers which have a role for unrolling the main loop will be removed. Also, instead of unrolling the main loop of AES algorithm, we implement... 

Network on Chip (NoC) is the most common interconnection platform for multiprocessor systems-on-chips (MPSoCs). In order to explore the design space of this platform, we need a high-speed, cycle-accurate, and flexible simulation tool. In this paper, we present AdapNoC, a configurable cycle-accurate FPGA-based NoC simulator, which can be configured via software. A wide range of parameters are configurable in FPGA side of the proposed simulator, and the software side is implemented on an embedded soft-core processor. We transfer some parts of simulator, such as Traffic Generators (TGs) and Traffic Receptors (TRs), to software side without any degradation in simulation speed. Moreover, we... 

In this work, a general semi-analytical method for the determination of the elastic fields within an anisotropic homogeneous elastic solid with an inclined edge or interior crack is developed. In this method, the displacement field is represented as a sum of a function and a finite series of functions with unknown coefficients. The functions are constructed in such a way that all the essential homogeneous and inhomogeneous boundary conditions are satisfied exactly and, moreover, the displacement discontinuity across the crack faces as well as the exact singular behaviour of the stress field at the crack-tip are captured. The unknown coefficients are determined by utilizing the principle of... 

The friction drive principle, which is based on the superposition of two synchronized perpendicular vibrations at the interface of the robot and the work floor, plays a fundamental role in the locomotion of miniaturized robots. In this paper, the iteration perturbation method proposed by He is used to generate a periodic solution for this type of friction drive microrobot. The equation of motion for the system reveals a parametrically excited oscillator with discontinuity, the elastic force term for which is proportional to a signum function. The obtained solutions are in excellent agreement with those achieved from numerical integration and experiments reported in the literature. Results...