Sharif Digital Repository

Execution speed seriously bothers application developers and users for wearable devices such as Google Glass. Intensive applications like Mobile Augmented Reality (MAR) suffer from significant delays when CPU is busy. Energy is another concern when the devices are in low battery level but users need them for urgency use. To ease such pains, one approach is to expand the computational power by cloud offloading. This paradigm works well when the available Internet access has enough bandwidth. Another way, however, is to leverage nearby devices for computation offloading, which is known as device-to-device (D2D) offloading. In this paper, we present Dandelion, a unified code offloading system... 

Based on numerous laboratory and field evidence, low-salinity waterflooding or engineered salinity waterflooding can lead to enhanced oil production. According to the literature, the mechanisms involved in this process can be divided into two general categories: fluid-fluid interactions and solid-liquid interactions. These mechanisms are caused by intermolecular and electrostatic forces at the rock and fluid interfaces. The most important controlling factor of the electrostatic forces is the concentration of ions at/near fluids-rock interface. Therefore, improving the concentration of ions causes a shift in wettability toward a more water-wetting state, eventually leading to increased oil... 

A total of twenty-four reinforced concrete arches with dimensions of 110 × 30 × 10 cm were casted, fabricated and tested. There are three variables, including: height to span ratio, longitudinal reinforcement ratio and arrangement and number of FRP layers.Based on results, with increasing height to span ratio, the efficiency of FRP strengthening method decreases. It is due to the fact that FRP materials inherently behave better in tension. From another point of view, in lower arches (L group) extrados bonding technic has better effect on increasing peak load of the arches, while in higher ones (H group) intrados bonding is discerned as the best method of strengthening. This paradoxical... 

Bioactive glasses are able to bond to soft and hard tissues in living body and their application as coating on metallic implants like 316L stainless steel has two important effects: (1) intimate link between bone and materials and (2) corrosion protection of metallic implant in body fluid and protection from tissues in front of corrosion products. Therefore, in this research, 45S5 bioactive glass prepared via sol- gel method was dip coated on 316L stainless steel substrates and its characteristics was investigated.Results of phase analysis showed that by sintering 45S5 bioglass at 600 ˚C for 5 h, an amorph sample with small amount of Na2Ca2Si3O9 was obtained. So, the bioglass coated samples... 

Today, with the development of micro-technology in chemical reactions, the use of appropriate systems for the separation and purification of synthesized chemicals seems to be necessary. In this study, the continuous synthesis of bromide-lithium exchange reaction and the separation of organic and aqueous phase products in micro systems was investigated.The method used to construct micro-separator and micro reactor, a laser engraving technique, and thermal bonding of glass to glass.In the first step, the factors affecting the separation of organic and aqueous phase in the capillary micro-separator, such as the width of the capillary, the length of the capillary, the number of capillaries and... 

It has always been a challenge to make self-cleaning coatings based on super-hydrophobic properties that can provide the necessary features to be operational in the industry. One of these necessary features is the ability to easily apply the coating on the substrate and reduce the cost by finding the optimal amount of consumables. Therefore, in this research, at first, it was tried to produce silica nanoparticles with a particle size of less than 011 nm using the Stober method, and then the surface of the synthesized nanoparticles was coated with HDTMS (Hexadecyltrimethoxysilane) to make the silica particles, which are hydrophilic in nature, hydrophobic. According to the conducted studies,... 

In this work, we have used a 3D printer and unidirectional ice-templating technique in conjunction, to fabricate a novel composite scaffold to facilitate local osteochondral defects tissue regeneration with a cell-free approach. Using ice-templating to induce radially-aligned porosity formation in type I bovine collagen is known to expedite host cells' migration into the scaffold which their ECM secretion shifts cellular milieu toward that of its neighboring tissue layer. We used numerical analysis to design and optimize appropriate freeze-casting mold, finding the optimum value for pin height and metal slab depth to be 4mm and 14mm, respectively. Collagen content equivalent to 2%w/v was... 

Formation damage in petroleum engineering is an important and fundamental phenomenon. During drilling operation, penetration of either the solid phase of drilling fluid or the base-fluid into the porous medium, reduces the permeability of the formation. While most experiments in the literature have focused on core-scale and beyond, there is lack of pore-scale studies. Moreover, presence of fractures has an undeniable effect on the extent of formation damage. Thus, the main objective of this dissertation is to investigate the effects of fractures on the severity of formation damage caused by the water-based drilling fluid and the mechanisms of formation damage at the pore scale, using glass... 

Metallic glasses have been applied in industry owing to their attractive mechanical, physical, and chemical properties. such as high electrical resistivity, soft-type superconductivity, good magnetic softness, high strength and large elastic strain. These unusual properties make the amorphous alloys potentially useful for various applications, which originate from the intrinsic random atomic configuration. but their plasticity is low and this disadvantage limites their applicable range as a engineering material. In this study we try to improve plasticity of metallic glasses by structural rejuvenation. Structural rejuvenation in metallic glasses by a thermal process (i.e. through recovery... 

Solid oxide fuel cells are used to convert solid-state energy to direct electrical current by electrochemistry mixing a gas fuel and an oxidant in an oxide electrolyte. One of the most interesting aspects of this field for the researchers is the reaction between the metal interconnect and the glass sealant. In the current research, deposition of the YSZ coating onto the metal interconnect in order to impede the reaction with glass sealant and prohibition of its oxidation in oxidizing/reducing environment in high temperature, was mainly investigated. Effect of applying YSZ Thin layer in the intersection of Crofer steel and glass sealant on strength and chemical durability of these two... 

This research work deals with application of poly-saccharide to improve coating process of bioactive ceramic composite on aNd-Fe-B magnetic alloy substrate. Bioactive glass particles were synthesized through a sol-gel process and coated in the form of composite with poly-saccharide onto a magnetic substrate by electrophoretic deposition technique. Stable suspensions of 0.5 gr/lit polysaccharide polymer-ceramic were prepared using bioactive glass particles (<1µm), acetic acid 1%. The influence of added water to ethanol, pH and tri-ethanol-amine (TEA) additive on suspension stability, deposition rate and coating’s structure was investigated. It was shown that by increasing the water to ethanol... 

Delamination is a major problem in drilling of fiber-reinforced composite materials. Thrust force is an important factor leading to propagation of delamination during drilling process. One of effective methods to reduce machining forces is application of ultrasonic vibrations. In this study ultrasonic assisted drilling is applied to reduce thrust force in drilling of GFRP laminates. In order to conduct experiments a setup is designed and fabricated to apply both vibrations and rotation to drill bits. Using Taguchi method, a set of experiments is conducted with feed rate, spindle speed, point angle and ultrasonic vibration amplitude as control factors. The results show that applying... 

PMMA bone cement lacks biodegradability and the ability to bond with surrounding bone tissue. Therefore, the development of a new generation of bioactive bone cements that are biodegradable and possess adequate mechanical properties as well as desirable setting time is receiving remarkable interest.In this study, we have developed novel mineral-based bioactive bone cements. Our mineral bioactive bone cements were composed of Calcium Sulfate Hemihydrate, Bioactive Glass, and Tricalcium Silicate. Firstly, a binary system composed of Calcium Sulfate Hemihydrate and Bioactive Glass was optimized based on mechanical and setting behavior. Secondly, Tricalcium Silicate was added to the powder phase... 

Recently, diamond nanoparticles have attracted interest for biomedical applications such as drug delivery, targeted cancer therapies, fabrication of tissue scaffolds and biosensors. In the present work, elecrophoretic deposition (EPD) of nanodiamond-bioactive glass-alginate nanocomposite was studied. In vitro bioactivity and biocompatibility of the nanocomposite were evaluated in simulated body fluid (SBF) and by MTT assay. The EPD process was performed under different conditions in order to obtain a uniform coating on the surface of 316L stainless steel substrate. The stability of the suspension was determined via optical sedimentation method and zeta potential analysis. It was found that... 

Eyesight is one of the most important tools for humans to communicate with environment and consequently, blindness or poor eyesight results in unsatisfactory effect on life quality. Owing to the importance of the sense and to assist to the patients, this thesis aims to design and assemble cybernetic glasses using ultrasound waves. To this end, firstly, the notion of waves focusing on ultrasound waves is described and reactions of human hearing system to the waves are studied. Then, the transducers as a key device are introduced. Afterward, bat sense system to communicate with environment which is based ultrasound waves is described. Next, attenuation effects on ultrasound wave pressures are... 

Wound healing is a complex and regular process. It makes more challenge when the volume of wound exudate becomes uncontrollable. To solve this problem, hydrofiber wound dressings which contain carboxymethyl cellulose fibers are being used. Fast absorption and keeping the moisture in balance specially in chronic wounds, is one of the major features of hydrofiber wound dressings. In this research, which was conducted with the aim of investigating the synergy effect of active glasses and Hydrofiber commercial wound dressing for the healing of skin wounds, especially chronic wounds, the sol-gel method has been used to synthesize bioactive glasses based on borosilicate, replacing a part of CaO... 

The rehabilitation of old structures holds a lot of importance, as many structures with a life span of over 30 years are prone to severe damage and even collapse. To overcome this problem, the use of FRP sheets to strengthen structures is suggested. RC-arches have been used in many structures such as bridges and require specific consideration in terms of strengthening. So far, the influence of the number of FRP layers and location, the height of arch and percentage of reinforcement on strengthened arch behavior have not been investigated. In this research, reinforced concrete arch members strengthened with GFRP and CFRP were investigated. A total of 28 Specimens, including four... 

Recent investigations on construction engineering have determined that repairing of Reinforced Concrete (RC) by means of fiber reinforced polymer (FRP) composites is an effective method of retrofitting existing columns. The main research in this thesis focuses on the repair of concrete specimens which are damaged and their initial strength has been reduced. To achieve this purpose, through experimental procedures, the effect of confining damaged concrete cylinders by FRP, has been investigated. The experimental program included three parameters: type of fibers (glass or carbon), type of confining (full or partial), and the number of layers. First concrete cylinders were made and loaded to... 

During all operations in oil and gas reservoirs, it is possible to cause formation damage. These damages can greatly reduce the rate of production. One of the major damages that can seriously affect the performance of a reservoir is the damage caused by drilling fluid. The main purpose of this thesis is to study the main mechanisms of formation damage caused by water-based drilling fluid using a glass micromodel for the first time. An accurate understanding of the mechanisms of formation damage can provide a good understanding of the selection of the type and concentration of materials used, as well as appropriate methods to control and eliminate damages. for controlling the drilling fluid... 

Understanding biological systems requires extensive knowledge of individual parameters, and to study the processes of cell differentiation and cell behavior, a suitable environment must be created with the physiological conditions of the human body. For this purpose, with the knowledge of microfluidics, a microenvironment can be provided to study the behavior of cells on a small scale. The use of bone tissue model microfluidic chips is an alternative and new method in which it is possible to study the behavior of cells to differentiate into bone and to examine the toxicity of drugs, which in itself can help in the effective and successful treatment of these cases show. Therefore, in this...