Sharif Digital Repository

Locking plates have threaded holes, in which threaded-head screws are affixed. Hence, they do not need to be in intimate contact with underlying bone to provide fixation. There are, however, reports that a large distance between the plate and the bone might cause clinical complications such as delayed union or nonunion, screw pull out, and screw and plate breakage. Considering the diversity in the capabilities and costs of different plate customization techniques, the purpose of this study was to investigate the effect of the plate contouring quality on the biomechanical performance of high tibial osteotomy (HTO) fixation. A finite element model of proximal tibia was developed in Abaqus,... 

Titanium alloys are widely used in various areas, particularly in medical and dental industries, due to their remarkable properties. Still, the optimum cutting conditions for titanium alloys are under consideration. Ti alloyed with Cu has been reported to provide unique properties such as good mechanical performance, good biocompatibility, acceptable corrosion resistance, and relatively lower melting point. The properties of Ti-Cu alloys mentioned above are sensitive to microstructure. They are highly dependent on microstructural characteristics such as the formation, growth, and morphological features of intermetallics and precipitates, dependent on the amount of Cu and the manufacturing... 

Natural and biodegradable polymers are of particular interest as green sources with low-cost and environmentally friendly features, and have been widely used for polymer composite development. The term “Green Composites” refers to polymer/filler systems in which polymer, filler, or sometimes both components are green in view of sources from which they are yielded or their biodegradability. Natural fibers obtained from plants, animals, and/or geological processes are a big class of green sources widely applied in green composite development. There has also been continued research on recycling of green composite as well as developing hybrid systems for advanced applications. In view of their... 

Scalability has always been a challenge in software development, and agile methods have faced their own ordeal in this regard. The classic solution is to use modeling to manage the complexities of the system while facilitating intra-team and inter-team communication; however, agile methods tend to shy away from modeling to avoid its adverse effect on productivity. Model-driven development (MDD) has shown great potential for automatic code generation, thereby enhancing productivity, but the agile community seems unconvinced that this gain in productivity justifies the extra effort required for modeling. The challenge that the MDD community faces today is to incorporate MDD in agile... 

Application of composite lattice structures in aerospace application can bring about considerable weight savings, thus allowing for increased payload weight. This study is devoted to reliability analysis of composite anisogrid lattice interstage structure (CALIS) used in typical launch vehicle (LV). CALIS is usually formed in to thin-walled cylindrical or conical shell via helical and circumferential ribs that can act as a lightweight load bearing support structure interfacing any two stages of the LV. Thus, the current study is of practical importance as the interstage structure is acted upon by rather high axial and bending forces emanating from LV external aerodynamics, thrust and... 

Due to the remarkable progress in the field of the manufacturing process, smart composites have become the desired target for high-tech engineering applications. Accordingly, for the first time, thermal buckling, critical voltage and vibration response of a thermally affected graphene nanoplatelet reinforced composite (GPLRC) microdisk in the thermal environment are explored with the aid of generalized differential quadrature method (GDQM). Also, the current microstructure is coupled with a piezoelectric actuator (PIAC). The extended form of Halpin-Tsai micromechanics is used to acquire the elasticity of the structure, whereas, the variation of thermal expansion, Poisson’s ratio, and density... 

Wind energy has been continuously considered as a green, available, and economical alternative source of energy. For centuries, the transformed wind energy to drag-force has been used for transportation in watercrafts. With improvement of aerodynamics, the airfoil was invented to create and use a higher magnitude aerodynamic force, lift-force, in order to elevate airplanes. Later, the lift-force was horizontally applied as the thrust force in land/water wind-crafts. Whereas in airplanes horizontal airfoils (wing) create a vertical lift-force, installed vertical airfoils (wing-sail) produce a horizontal lift-force in wind-crafts. Therefore, this force can be used as thrust (driving) force in... 

Leakage power has already become the major contributor to the total on-chip power consumption, rendering its estimation a necessary step in the IC design flow. The problem is further exacerbated with the increasing uncertainty in the manufacturing process known as process variability. We develop a method to estimate the variation of leakage power in the presence of both intra-die and inter-die process variability. Various complicating issues of leakage prediction such as spatial correlation of process parameters, the effect of different input states of gates on the leakage, and DIBL and stack effects are taken into account while we model the simultaneous variability of the two most critical... 

In this study, mathematical modelling of oxidative coupling of methane (OCM) to C 2 hydrocarbons (C 2H 6 and C 2H 4) over La 2O 3/CaO catalyst in a fixed-bed reactor operated under isothermal and non-isothermal conditions was investigated using the MATLAB program. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i-butane and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed however; if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process would enhance the conversion, selectivity towards desired product and process yield. A comparison between the... 

Injection molding is one of the most important manufacturing processes for mass production of complex plastic parts. In this study, mold filling is simulated by using the OpenFOAM software for Non- isothermal Newtonian fluid. The OpenFOAM is an open source software that is used in Computational Fluid Dynamics (CFD) tools. The studied mold shape has a rectangular structure with a gate for Newtonian fluid injection. The simulation carried out at non-isothermal conditions and two-dimensional flow is considered. The velocity, shear stress and temperature changes in different parts of the mold are critically studied. We show that vortex formation plays an important role on changes of shear stress... 

In order to decrease CO 2 emission into the atmosphere and develop renewable energy sources for carbon capture, an integrated system is considered for co-production of electricity and methanol. In this research, methanol synthesis unit through captured CO 2 from fossil fuel power plant and produced H 2 from water electrolysis unit by wind renewable energy is developed. An oxy-fuel combustion carbon capture method is considered in large scale Matiant power plant based on utilization of oxygen from water electrolysis unit. Technical and economical analysis of the proposed system shows that when the price of natural gas is 7.8US$/GJ, the total CO 2 avoided cost is 93US$/(tonne of CO 2) and... 

A novel semi-active control system for suspension systems of passenger car using Magnetorheological (MR) damper is introduced. The suspension system is considered as a mass-spring model with an eight-degrees-of-freedom, a passive damper and an active damper. The semi-active vibration control is designed to reduce the amplitude of automotive vibration caused by the alteration of road profile. The control mechanism is designed based on the optimal control algorithm, Linear Quadratic Regulator (LQR). In this system, the damping coefficient of the shock absorber changes actively trough inducing magnetic field. It is observed that utilizing the present control algorithm may significantly reduce... 

Purpose - This paper aims to conduct a comprehensive fault tree analysis (FTA) on the critical components of industrial robots. This analysis is integrated with the reliability block diagram (RBD) approach to investigate the robot system reliability. Design/methodology/approach - For practical implementation, a particular autonomous guided vehicle (AGV) system was first modeled. Then, FTA was adopted to model the causes of failures, enabling the probability of success to be determined. In addition, RBD was used to simplify the complex system of the AGV for reliability evaluation purpose. Findings - Hazard decision tree (HDT) was configured to compute the hazards of each component and the... 

It is always crucial to estimate process capability index (PCI) when the quality characteristic does not follow normal distribution, however skewed distributions come about in many processes. The classical method to estimate process capability is not applicable for non-normal processes. In the existing methods for non-normal processes, probability density function (pdf) of the process or an estimate of it is required. Estimating pdf of the process is a hard work and resulted PCI by estimated pdf may be far from real value of it. In this paper an artificial neural network is proposed to estimate PCI for right skewed distributions without appeal to pdf of the process. The proposed neural... 

This paper is concerned with the study of the constant due-date assignment policy in a multistage assembly system. The multistage assembly system is modeled as an open queueing network. It is assumed that the product order arrives according to a Poisson process. In each service station, there is either one or infinite machine with exponentially distributed processing time. The transport times between every pair of service stations are independent random variables with generalized Erlang distributions. It is assumed that each product has a penalty cost that is some linear function of its due-date and its actual completion time. The due date is found by adding a constant to the time that the... 

In this study, the homotopy analysis method (HAM) is used to study dynamic pull-in instability in microbeams considering different sources of nonlinearity. Electrostatic actuation, fringing field effect and midplane stretching causes strong nonlinearity in microbeams. In order to investigate dynamic pull-in behavior, using Galerkin's decomposition method, the nonlinear partial differential equation of motion is reduced to a single nonlinear ordinary differential equation. The obtained equation is solved analytically in time domain using HAM. The problem is studied by two separate manners: direct use of HAM and indirect use of HAM in conjunction with He's Modified Lindstedt- Poincaré Method.... 

Scaling transistor size to the scale of the nanometer coupled with reduction of supply voltage has made SRAMs more vulnerable to soft errors than ever before. The vulnerability has been accentuated by increased variability in device parameters. In this paper, we present an analytical model for critical charge in order to assess the soft error vulnerability of 6T SRAM cell. The model takes into account the dynamic behavior of the cell and demonstrates a simple technique to decouple the nonlinearly coupled storage nodes. Decoupling of storage nodes enables solving associated current equations to determine the critical charge for an exponential noise current. The critical charge model thus... 

Massive amounts of spent lead-acid battery separators with 50 wt % silica nanoparticles (SiNPs) can be recycled for further use. One compelling application is form-stable phase change materials (FSPCMs). This study proposes a novel tertiary eutectic mixture of green and non-toxic lauric acid, palmitic acid, and paraffin, and recycled SiNPs to find a sustainable approach to deal with industrial wastes and energy consumption. Fatty acids and paraffin are promising for thermal energy storage in buildings. However, they lack sufficient thermal conductivity, mechanical strength, and suffer from leakage. To give mechanical strength, high-density polyethylene (HDPE) was added and sintered.... 

A comparison of various hydrogen production processes indicates that the thermal decomposition of methane (TDM) provides an attractive option from both economical and technical points of view. The main problem for this process is the deposition of the nano-carbon particles on the reactor wall (or catalyst surface). This research concentrates on the numerical simulation of the TDM process without use of a catalyst to find a technique that decreases the carbon accumulation in a tubular reactor. In this model, the produced carbon particles are tracked with the Lagrangian method under thermophoretic, Brownian, van der Waals, Basset, drag, lift, gravity, pressure and virtual mass forces. In... 

The process kinetics of a lab-scale upflow aerobic immobilized biomass (UAIB) reactor using simulated sugar-manufacturing wastewater as feed was investigated. The experimental unit consisted of a 22 l reactor filled with high porosity pumice stone. The UAIB reactor was tested under different organic loads and different hydraulic retention times (HRT) and the substrate loading removal rate was compared with prediction of Stover-Kincannon model, second-order model and the first order substrate removal model. After obtaining steady-state conditions, organic loading rate was increased from 750 to 4500 g COD/m3 day to resemble wastewater from sugar production lines, and hydraulic retention time...