Sharif Digital Repository

In this study, we numerically determined the performance of a microscale separator comprising a lateral and a main channel to separate a two-phase flow. It was aimed to conduct continuous phase through the lateral channel and dispersed phase through the main channel. The continuous and dispersed phases were modeled as incompressible Newtonian fluids with the corresponding interface tracked by the phase-field model. The dynamics, including pressure fluctuations in the separator, were further examined. It was mechanistically demonstrated how the geometry of the separator modulates the phase separation. Further examined were the influences of various geometrical parameters on the performance of... 

In this paper we have proposed an efficient method based on Genetic Algorithms (GAs) to design quantum cellular automata (QCA) circuits with minimum possible number of gates. The basic gates used to design these circuits are 2-input and 3-input NAND gates in addition to inverter gate. Due to use of these two types of NAND gates and their contradictory effects, a new fitness function has been defined. In addition, in this method we have used a type of mutation operator that can significantly help the GA to avoid local optima. The results show that the proposed approach is very efficient in deriving NAND based QCA designs  

This paper aims to study the soil dynamics characteristics of central part of Shiraz city near the monument of Persepolis, southwest of Iran. The parameter investigated is natural period of soil sediment. The technique used to obtain this parameter is microtremor measurements. Microtremor measurements were obtained at 120 stations in the city. The data was recorded for two periods of fifteen minutes. Segmental Cross Spectra were applied to calculate spectra. Nakamura's method (H/V) was used for analyzing the measured data. At each site, natural period values were obtained. Because of low accuracy of amplification factors that achieved by microtremor measurements, this factor is neglected in... 

A high-temperature superconductor slab irradiated by a desired pattern of light is proposed to behave as a completely controllable 2-D photonic media that could be applied in a wide range of photonic devices. In this case, the permittivity spatial variation, which is fundamentally required in many photonic devices, can be achieved by means of the selective variation of cooper-pair density under patterned irradiation. The process of photo-effect in superconductors is the proposed mechanism for the deformation of the spatial distribution of cooper-pair density and for the creation of nonuniform permittivity. In this perspective, the effects of nonuniform photon irradiation on the density of... 

Mixtures of aluminium powder and nanoscaled SiC particles (n-SiC) at various volume fractions of 0, 1, 3, 5, 7 and 10 are comilled in a high energy planetary ball mill under an argon atmosphere to produce nanocrystalline Al-SiC nanocomposites. High resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) method, laser particle size analysis and powder density measurement were used to study the morphological changes and microstructural evolution occurred during mechanical alloying. Al-SiC composite powder with microscaled SiC particles (1 μm) was also synthesised and characterised to examine the influence of reinforcement particle size on the milling process. It was found that... 

Aluminum powder and various volume fractions of SiC particles with an average diameter of 50 nm were milled by a high-energy planetary ball mill to produce nanocrystalline Al-SiC nanocomposite powders. Double pressing/sintering process was used to consolidate powders to cylindrical specimens. It was shown that a double cycle of cold pressing and sintering can be utilized to obtain high density Al-SiC nanocomposite parts without using a hot-working step. High resolution scanning electron microscopy (HRSEM), X-ray diffraction (XRD) and laser particle size analyzer (PSA) were used to study the morphological and microstructural evolution of nanocomposite powders and bulk samples. The role of... 

Alg -(1, 3, 5, 7, 10 vol%) SiC nanocomposites were produced by mechanical alloying (MA) and double pressing/sintering route. The characteristics of the milled powders and the consolidate specimens were examined using high resolution scanning electron microscopy and X-ray diffraction method. Compression and hardness tests were used to study the effect of SiC volume fraction on the strength of Alg -SiC nanocomposites. It was shown that with increasing the SiC volume fraction, finer particles with narrower size distribution and smaller crystallite size are obtained after MA. During sintering close to the melting point of aluminum, the presence of nanometer-scaled SiC particles was found to... 

All Rapid Prototyping and CNC material removal processes use information which is extracted from a CAD system. There are several ways to convert CAD data into usable manufacturing information. In this paper, five methods of translating CAD data into a usable manufacturing format are explained. These five methods are data translation from CAD files in STL, DXF, STEP-NC, and IGES formats as well as a platform-dependent area method of manufacturing information in a desirable format. For each method, algorithms and details about the CAD data translation into usable manufacturing and prototyping processes formats are presented. Finally, applications of each approach and its pros and cons are... 

Distal radius fractures are prevalent injuries. Unstable fractures with joint involvement generally require surgical fixation to optimize outcomes. One of the ways to treat unstable fractures is percutaneous pinning, which usually has less stiffness compared to the common method of plating in treating this type of fracture. Still, it has some advantages compared to the plating method. Pi clamp fixation method is one of the novel approaches for stabilizing distal radius fractures that utilizes a set of K-wires and a small clamp. This study uses the finite element method (FEM) to examine the effect of the four factors that are expected to have an effect on the stability of fixation. To conduct... 

The introduction of microgrids (MGs) and renewable energy sources (RESs) has caused significant shifts in the operation of power systems. Despite many benefits, integration of RESs has emerged new issues in the power systems operation. One of the issues recently raised by some utilities, is the severe ramps which are seen in systems with high penetration of RES. On the other hand, the traditional flexible power plants could not provide the ramp required in these systems. As a result, flexible local resources in independent entities like MGs should be employed to tackle this issue in these systems. In this paper, a novel model is developed to investigate the effects of MGs and gas grid... 

Power systems have been undergoing significant restructuring as a result of increasing independently operated local resources. Consequently, new entities, i.e. microgrids (MGs), are developed, which facilitate the integration of local resources, specifically renewable energy sources (RESs), into the operation of power systems. Despite many benefits, the integration of RESs could cause severe rampings in the net-load, which would challenge the reliable operation of the system. Therefore, it seems essential that flexible local resources in an MG should be employed to provide flexibility services to the main grid, thus ensuring that ramping in the MG's net-load would meet the ramping capability... 

Introduction of renewable energy sources (RESs) and independently operated multi-microgrid (MMG) systems have led to new issues in the management of power systems. In this context, uncertainty associated with RESs as well as intense ramps inflicted on the network called system flexibility constraints have raised new challenges in power systems. The new condition necessitates the implementation of novel frameworks that enable local system operators to efficiently manage the available resources to cope with the flexibility-ramp constraints. Moreover, the new framework should facilitate energy management in a system with an MMG structure considering uncertainty of RESs. Consequently, in this... 

Introduction of renewable energy sources (RESs) and independently operated multi-microgrid (MMG) systems have led to new issues in the management of power systems. In this context, uncertainty associated with RESs as well as intense ramps inflicted on the network called system flexibility constraints have raised new challenges in power systems. The new condition necessitates the implementation of novel frameworks that enable local system operators to efficiently manage the available resources to cope with the flexibility-ramp constraints. Moreover, the new framework should facilitate energy management in a system with an MMG structure considering uncertainty of RESs. Consequently, in this... 

Background: Basic epidemiological data can provide estimates when discussing disease burden and in the planning and provision of healthcare strategies. There is little quantitative information in the literature regarding prevalence of traumatic injuries from developing countries. Objectives: The aim of the current preliminary study was to reveal the prevalence and age and gender distribution of various traumatic injuries in a tertiary referral orthopedic hospital in Iran. Patients and Methods: In a prospective descriptive study, all traumatic injured patients attending the Orthopedic Trauma Unit of our center in a five year period were included. Demographic details, the cause of injury,... 

Distal humerus fractures commonly occur in adults with low bone mineral density causing major technical challenges for orthopedic surgeons. Persian fixation method was introduced as a novel technique to stabilize small fragments in comminuted distal humerus fractures using a set of K-wires and a reconstruction plate. The present study aims to measure this technique's stiffness and stability of this technique and analyze the effect of influential parameters with numerical simulation and biomechanical testing on a cadaveric specimen. Validation of the finite element (FE) model was conducted based on results of experiments. The results indicated that Delta configuration mainly led to a higher...