Sharif Digital Repository

With the development of science and technology and its application in IT (e.g. internet, intranet and URL) the sharing of manufacturing resources reaches higher research attention, where resource virtualization enables new possibilities in terms of collaboration. As a result of these changes, with the intention of sharing optimum allocation of cloud manufacturing resource and capability among service providers and service users, the concept of service composition was introduced. Cloud services can be combine to build virtual manufacturing chain, so a strategy focusing on the evaluation and selection of virtual manufacturing resources to fulfill given services is fundamental exercise to... 

Nowadays, due to the indensible role of electrical energy in life of societies, the reliability of service should be provided in an economic form. Researches has shown that, about 80% of faults occur in the distribution network. In a distribution network that is equipped with automation systems, through the acceleration in the determination of the fault location, and also possibility of reacting against transient and steady faults, the electricity interruption time duration is minimized. This thesis aims to determine the number and to locate the auto reclosers and fault indicators in a distribution network optimally. To make it economically feasible, a limited number of these devices and... 

Nowadays the combination of mechanical and electronic systems in small scales is gaining attention. Micro electro-mechanical systems are widely used in various industries such as car manufacturing and electronic chips. In these devices, the most important and useful mechanical structures are beams and plates. Therefore, investigating the mechanical properties of these structures in very small scales (micro and nano) is of great importance. Decreasing the size to these scales leads to the dependence of the behavior of these structures to size. Accordingly, some theories for prediction of these behaviors have been presented, one of which is the strain gradient theory. This theory is used in... 

Cardiovascular diseases are one of the leading causes of death in the world. Identifying the mechanical behavior of arteries and their growth and remodeling under applied loadings can help to better understand the progression of the disease and provide more effective clinical interventions. Therefore, many researchers in recent decades have turned their attention to modeling the process of stress-mediated growth and remodeling in soft tissues. Among the most important models proposed to study this process are the constrained mixture model proposed by Humphrey et al. and the volumetric growth model proposed by Hoger et al.. The constrained mixture model is based on the continuous turnover of... 

One of the extensively used, yet complex, structures in the industry is pre-twisted Micro/Nano beams. Studying their mechanical behavior helps to have a broader view of them. In this present study, explores and analyzes the behavior of a pre-twisted Micro/Nano beam with a quadrangular/rectangular cross-section using the strain gradient theory and modified couple stress theory. Using the calculus of variations and the Hamiltonian principle the elastodynamics governing partial differential equations of transverse deflection of the pre-twisted Micro/Nano beam with hinged-hinged boundary conditions are derived. Then the mechanical behavior of the pre-twisted Micro/Nano beam in static mode and... 

In this research, we have used green tea polyphenols as green reductants for reduction of graphene oxide. Furthermore, for the first time, the presence of some metals such as iron, tungsten and copper in the efficiency of reduction is investigated. XPS spectra indicate that iron can be considered as one of the best choices for helping polyphenols in the reduction process. Hence, we used AFM, XPS, Raman spectroscopy and I-V diagram to characterize graphene oxide reduced by polyphenols and iron. In recent years, hydrazine has been recognized as one of the standard reducing agents for effective reduction of graphene oxide. In our analysis, it is found that the conductivity of our reduced... 

With the development of science and industry increasingly need for seamless and high-strength rings, the attention of many researchers and industrialists paid on the ring rolling process. Then, Studying details of ring rolling process is very important. The most important issues in ring rolling process which are not sufficiently considered are: stress components distribution in ring, real amounts of friction coefficient, pressure distribution over the rollers, required power, required torque and force, and finally the minimum thickness of the ring during the process, all of these parameters have developed as analytical functions. In the present study, the minimum possible thickness of the... 

Keratoconus is one of the most common optical (visual, eye) diseases that usually occurs in youth or early third decade of life. In this disease, cornea gets thin and loses it initial shape and becomes conical. Doctors use different methods for its treatment including use of glasses, contact lenses (hard or soft), cornea transplantation and also cross linking of cornea. Each of these methods have their limitations, on the other hand, considering that this disease progresses and intensifies, ophthalmologists use corneal ring implant surgery for the treatment of this disease in its advanced levels. A good ring implant in corneal causes increased strength and also cause corneal to get back to... 

To expand the applications of alginates as carbohydrate-based biopolymers, calcium alginate beads were developed as catalytic support for the encapsulation of functionalized heteropolyacid with ionic liquid. This novel heterogeneous acid catalyst was applied for the 5-HMF production from fructose. Here, the roles of heteropolyacids as acidic species and ionic liquids for better stabilization of such materials were more clearly understood. The impact of the heteropolyacid type on catalyst efficiency was also investigated. Under optimal reaction conditions (i.e., 120 °C, 100 min reaction duration, and 28 wt.% of reactor catalyst loading), which were obtained by RSM analysis, the 5-HMF... 

Due to importance of micro electromechanical systems (MEMS), inability of the classical continuum theory to predict the mechanical behavior of micro-scale structures accurately, and vast applications of finite element method (FEM) in modeling of the MEMS, in this dissertation, the static and dynamic mechanical behavior of electrostatically actuated micro structures has been investigated using newly developed finite elements based on strain gradient continuum theory. The governing equations and boundary conditions have been developed for longitudinal and torsional behavior of microbars as well as flexural behavior of Euler-Bernoulli and Timoshenko microbeams based on strain gradient... 

Competitive world of industrial production need more speed and faster reaction for the customer needs. This should be carried out in low cost activities while satisfying what the consumers and customers require. Business of commercial refrigerators and freezers is a big industry targeting small to big customers. In this thesis a systematic method relying on reduction of cost, reworking and unexpected expenditures in product life is utilized. Stands for Design for Manufacturing, DFM is a series of principles and guideline simply to achieve a faultless design of a product so that the non-incurred costs of the product travel through its life cycle become minimized. Freezers and refrigerators... 

In this dissertation, we investigate the problem of the existence of finite geodetic sequences from point to point (0, n). This has not been proven in the general case. In this dissertation, we present an article that illustrates this question in a particular case of z ^ 2 subspaces whose self and complement are infinite and connected (e.g., slit planes, half-planes, and sectors). Writing x_n for the sequence of boundary vertices, we show that the sequence of geodesics from any point to x_n has an almost sure limit assuming only existence of finite geodesics. For all passage-time configurations, we show existence of a limiting Busemann function. Specializing to the case of the half-plane, we... 

A single-degree-of-freedom model is considered for flexible exercise bars based on the lumped-element approach. By considering the side segment of a flexible exercise bar as a cantilever beam with an equivalent mass at the free end, its free-vibration response and forced one under excitation of the grip of the flexible bar is written parametrically. Some experiments are performed on a specific flexible bar to obtain numerical values for the parameters in the model to have it quantitatively known. In the next step, simulation of the model results in the response of the flexible bar under a considered excitation. The response is imported into a multi-segment musculoskeletal software, AnyBody,... 

The low female labor force participation rate in the Iranian labor market relative to the global average and even to countries that do not differ significantly from the socio-economic characteristics of our country is one of the important questions of the Iranian labor market. In this study, we seek to answer the question of whether the economic participation rate of married women will increase if the gender gaps in wages, job findings and job losses among women and men are eliminated in the Iranian labor market. To answer this question using household expenditure and income data and labor force data, we show that between the two categories of occupations, in terms of the share of women's... 

With the rapid development of wireless communication standards, the co-existence of multiple standards in a single chip becomes inevitable. It is also fueling interest in analog to digital converters (ADCs) that are reconfigurable over a wide range of bandwidths and resolutions with adaptive power consumption. Employing such ADCs rather than using multiple individually power-optimized ADCs results in a great reduction of silicon area. Hence, a reconfigurable ADC can reduce time to market, and save costs.
This thesis addresses the challenges exists in conventional reconfigurable methods, and presents a novel reconfiguration methodology for changing resolution in pipeline ADCs. The... 

Since the development of various anti-cancer drugs, numerous attempts have been made to decrease their off-target adverse effects anhance their efficiency.Among these efforts developing novel drug delivery systems have been demonstrate promising potentials and lots of carriers have reached the market and clinical phases.Although plentiful researches on different drug carriers, lots of problems in drug loading, release and final efficiency are yet remaind.In recent decade, graphene oxide and graphene aerogel have been attracted remarkable intrest as drug carriers, due to their biodegradable and biocompatible characteristics.Accordingly, in this study graphene aerogel have been synthesized... 

Ruthenium based-oxide coatings on Titanium anodes are widely used as DSA (Dimensionally Stable Anode) for chlorine and chlorate production. Coatings consisting of composition of highly conductive oxide of noble metals (Ru, Ir and Pt) make them as long lasting anodes in chlor-alkali technology.In this work, a newly anode by a ternary coating of IrO2, RuO2, and TiO2 on the Pt-coated Ti was developed through thermal decomposition of iridium and titanium and ruthenium inorganic salts dissolved in n-pentane. The effect of deposition parameters such as current density, time, different condition of baking, heating, mole ratio and pulling up the samples was investigated to find out reasonable... 

During the past decade, micromachining technology has become available to fabricate micron-sized mechanical parts. The miniaturization of almost all types of devices and systems is arguably a greater opportunity for commercial profit and beneficial technological advances (e.g., micromechanical, microfluidic, microthermal, micromagnetic, microoptical and microchemical). However, instead of the traditional evolutionary engineering effort to reduce size and power while simultaneously increasing the performance of such a diverse set of systems, the field of microelectromechanical systems (MEMS) represents an effort to radically transform the scale, performance and cost of these systems by... 

From the past, the damask rose has an important place in various pharmaceutical, food, health and cosmetic industries. This product has the largest cultivated area in Iran, which is about 24,000 hectares, equal to 60% of its total cultivation in the world. Considering the conditions required for the cultivation of this plant, including the low water requirement, the expansion of its cultivation has been considered. One of the important obstacles to not expanding cultivation is manual harvesting, which strongly affects the quality and mass of essential oil and rose water. The efforts that have been made so far in the field of designing and producing the rose harvesting machine have not had... 

Characterization and simulation of carbon nanotube-reinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNT-reinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction...