Sharif Digital Repository

The objective of this study is to investigate the effects of both rubbery phase and nanosilica on mechanical properties of epoxy. Three series of formulations based on epoxy including nanosilica, rubber and rubber/nanosilica were prepared. Transmission electron microscopy showed that nanoparticles were homogeneously dispersed throughout the epoxy matrix. Compression and fracture toughness tests along with scanning electron microscopy and transmission optical microscopy were also done to evaluate the properties of the compounds. Although the results of compression tests indicate that addition of nanosilica could not change elastic modulus and yield strength of neat resin significantly,... 

The economic production quantity (EPQ) model is often used in manufacturing environments to assist firms in determining the optimal production lot size that minimizes the overall production-inventory costs. While there are some unrealistic assumptions in the EPQ model that limit its real-world applications, in this research, some of these assumptions such as (1) infinite availability of warehouse space, (2) all of the produced items being perfect, and (3) the existence of one product type are relaxed. In other words, we develop a multi-product EPQ model in which there are some imperfect items of different product types being produced such that reworks are allowed and that there is a... 

Changes in business environment are leading firms to adopt a new production model called agile manufacturing. This term moves away from the traditional mass production paradigm and focuses on manufacturing highly customised products when customers require them. In this paper, we present an initial approach to agile organisation based on case studies in an Iranian industrial organisation. An agile organisation conceptual model has been drawn up, based on the conclusions of the case study. The study presented here is of an exploratory factor analysis and the conclusions are drawn through path analysis, propose possible routes for future research in the field of agile organisation. By the... 

Design and optimization of centrifugal compressors, based on main blades configuration of impeller have been vastly discussed in open literature, but less researches have addressed splitters. In this research, the impeller of a commercial turbocharger compressor is investigated. Here, profiles of main blades are not changed while the effect of changing the configuration of splitters is studied. An optimization study is performed to find the best configuration using genetic algorithm over a complete operating curve of the compressor. CFD codes with experimental support are used to predict the compressor performance. Quantumetric tests beside destructive analysis of two impellers are... 

Purpose - the purpose of this study is the measuring of the human movement using printed wearable sensor. Human movement measurement is one of the usages for wearable sensors. This technology assists the researchers to collect data from the daily activities of individuals. In other words, the kinematics data of human motion will be extracted from this data and implemented in biomechanical aspects. Design/methodology/approach - This study presents an innovative printed wearable sensor which can be used for measuring human movement orientations. In this paper, the manufacturing process, implementation, measurement setup and calibration procedure of this new sensor will be explained, and the... 

Due to aging, circuit reliability has become extraordinary challenging. Reliability-aware circuit design flows do virtually not exist and even research is in its infancy. In this paper, we propose to bring aging awareness to EDA tool flows based on so-called degradation-aware cell libraries. These libraries include detailed delay information of gates/cells under the impact that aging has on both threshold voltage (Vth) and carrier mobility (μ) of transistors. This is unlike state of the art which considers Vth only. We show how ignoring μ degradation leads to underestimating guard-bands by 19% on average. Our investigation revealed that the impact of aging is strongly dependent on the... 

Application of composite patches in repair of damaged/aged aircraft structures is one of the most popular repairing methods in aerospace engineering. Since running experiments are difficult, time consuming, expensive, and also require high level of expertise, simulation of the behavior of the patch and also the faulty components after repair can assist designers and engineers in optimization of their designs. In this article, full-scale simulation of a damaged panel that is experimentally repaired with a composite patch will be considered using ABAQUS, a commercial finite element code. The crack growth process is modeled with the extended finite element method and the cohesive zone model... 

In this manuscript, a vehicle allocation problem involving a heterogeneous fleet of vehicles for delivering products from a manufacturing firm to a set of depots is considered. Each depot has a specific order quantity and transportation costs consist of fixed and variable transportation cost. The objective is to assign the proper type and number of vehicle to each depot route to minimize the total transportation costs. It is assumed that the number of chartering vehicle types is limited. It is also assumed that a discount mechanism is applied to the vehicles renting cost. The discount mechanism is applied to the fixed cost, based on the number of vehicles to be rented. A mathematical... 

Process planning (PP) has an important role in manufacturing systems design and operations. Volume decomposition and machinable volumes (MVs) or machining features determination is the core activity in process planning. This process requires extraction of elementary volumes (EVs), merging or clustering EVs to construct feasible MVs and finally selecting an optimal combination of MVs. Development of MVs is an important activity, so that better solution is obtained by better developed MVs. Generation of limited number of MVs or machining features, which is often performed by experts may miss the optimal solution. Also, using exact methods such as combinatorial optimization not only generate... 

A millimeter wave H-plane duplexer using E-plane filters has been designed. T-junction is used for connecting the channel filters compensated by cylindrical post and analyzed by integral contour method. Moreover the junction discontinuity effects have been taken into account. The combination of filters and compensated T-junction allows for low-cost manufacturing. The E-plane filters are analyzed separately, by mode matching method. The scattering parameters of the combination of filters and T-junction are obtained. The diameter and position of the compensating rod and length of T arms are optimized to achieve desired performance. This procedure saves time and memory in computations. The 38... 

Availability of a system is a crucial factor for planning and optimization. The concept is more challenging for modern systems such as robots and autonomous systems consisting of a complex configuration of components. In this paper, a reliability evaluation framework is developed for a system of binary state autonomous robots in an automated manufacturing environment. In this framework, the concepts in functional block diagram, table of truth, and sum of state are employed simultaneously to develop a binary state reliability model. Due to inefficacy of the method for larger number of components involved in complex systems, an extension of the Bernoulli trials is proposed. In an... 

Advances in semiconductor technology have made integration of multiple processing cores into one single die a promising trend towards increasing processing performance, lowering power consumption, and increasing reliability for embedded systems. Multicore processors, due to their intrinsic redundancies, are good choices for critical embedded systems for which the reliability is a crucial component. In this paper, an aging-aware adaptive fault tolerance method for DVFS-enabled multicore processors is presented. The analytical results show 3 to 6 order of magnitude increase in reliability of the system without addition of cores or redundant software. By using an aging-aware approach, the... 

This article deals with technology strategy and its linkage with overall strategy at multi-business, diversified groups. In the last two decades, the alignment of technology and business strategy has been one of the important research fields in strategy and technology management literature. These researches has been concentrated on single companies through which different frameworks, models, and decision support tools have been developed and widely utilized by industries. Although multi-business and diversified groups play an important role in national economy of developing countries and need a comprehensive and overall plan for the management of their diversified technological capabilities,... 

Statistical process control provides useful tools to improve the quality of multistage machining processes, specifically in continuous manufacturing lines, where product characteristics are measured at the final station. In order to reduce process errors, variation source identification has been widely applied in machining processes. Although statistical estimation and pattern matching-based methods have been utilized to monitor and diagnose machining processes, most of these methods focus on stage-by-stage inspection using complex models and patterns. However, because of the existence of high rate alarms and the complexity of the machining processes, a surrogate modelling is needed to solve... 

Design and manufacturing of a high performance micro-hydro-kinetic turbine is discussed in the present paper. The main goal is manufacturing an equipped experimental model of hydro-kinetic turbine with highest energy absorption from water current. A multi-shape ducted turbine comprised of a multi-part diffuser was manufactured that can be converted to many experimental models for studying various diffuser enhancing effects. Turbine's rotor included a three-blade axial propeller and a mixed six-blade propeller with high power coefficient. Simple experiments on propeller were performed for flow visualization, torque measurement and illustrating dynamic balance at high speed rotation in air and... 

Many modern industrialized systems such as aircrafts, rotating turbines, satellite booms, etc. cannot perform their desired tasks accurately if their uninhibited structural vibrations are not controlled properly. Structural health monitoring and online reliability calculations are emerging new means to handle system imposed uncertainties. As stochastic forcing are unavoidable, in most engineering systems, it is often needed to take them into the account for the control design process. In this research, smart material technology is utilized for structural health monitoring and control in order to keep the system in a reliable performance range. In this regard, a reliability-based cost... 

The present work developed a mixed-mode cohesive zone model (CZM) with a mode I failure criterion to predict the delamination bending loads of multilayer, composite printed circuit boards (PCBs) assembled with soldered ball grid array (BGA) components that were reinforced with an underfill epoxy adhesive. Two different delamination modes were observed in these microelectronic assemblies: delamination at the interface between the solder mask and the first conducting layer of the PCB, and PCB subsurface delamination at the interface between the epoxy and glass fibers of one of the prepreg layers. The cohesive parameters for each of the two crack paths were obtained from fracture tests of... 

Carbon-doped zinc oxide/reduced graphene oxide (C-ZnO/rGO) was prepared by a facile one-pot supercritical methanol method. The synthesized C-ZnO/rGO nanocomposite with flower-like ZnO micro-rods (MRs) synergistically inherited all the advantages of carbon doping and rGO heterojunction and exhibited high photocatalytic activity for the photodegradation of methyl orange (MO) under visible light. The x-ray diffraction (XRD) results indicated that in presence of GO, a new carbon-doped phase was formed at the high temperature and pressure of supercritical methanol. The x-ray photoelectron spectroscopy (XPS) at low binding energies demonstrated that the valence band of C-ZnO-rGO is up-shifted by... 

The problem of allocating different types of vehicles for transporting a set of products in an existing transportation network, to minimize the total transportation costs, is considered. The distribution network involves a heterogeneous fleet of vehicles each with the given capacity and with a variable transportation cost and a fixed cost with a discounting mechanism. Due to nonlinearity of the discounting mechanism, a nonlinear mathematical programming model is developed. A prioritized K-mean clustering encoding is introduced to designate the distribution depots distances, their demands, and the vehicles’ capacity. Using this priority clustering, a heuristic routine is developed by which... 

This paper presents a new design process of a low-cost swirler employed in axial micro-turbines. The swirler is simple in design, inexpensive and easy to produce and has good adaptability to different potential conditions without major changes. The blades are shaped from trapezoid-shaped steel sheets curved to a certain radius to form a tin airfoil with suitable outlet angle distribution from hub to tip. The formed blades are then welded between two concentric rings to form a round cascade. Correction from flow to blade angles, namely induced incidence and trailing edge deviation angles, were calculated by CFD analysis and considered in blade shape design. The manufactured prototype made on...