Sharif Digital Repository

Hybrid photovoltaic thermal system (PV/T) is a pioneer mechanical and electrical system which can produce both thermal and electrical energy for domestic or industrial purposes. As the solar cell’s material is semiconductor, the electrical output of them reversely modifies with the reduction of solar cell’s operating temperature. One of the most operational and cost-effective methods that has been investigated is active cooling. The photovoltaic panel cools down with a channel under the PV’s rear surface and a fan in the channel outlet. The producing heat can warm up cold water of a house or a factory. In addition to active cooling, it is smart to utilize passive cooling such as artificial... 

Solid oxide fuel cells as high temperature electrochemical devices draw much attention in the last decades due to their fuel flexibility, high efficiency and low pollution. However, lowering operating temperature from about 850°C to around 650°C without significant overpotential loss, in order to lower costs and increase cells life time has remained a challenge. Recently, a new family of mixed ionic and electronic conducting ceramics (MIECs) which are formulated Ln2NiO4+δ (Ln= La,Nd,Pr) and crystallized in Ruddlesden–Popper structure, have been regarded as appropriate cathode materials for the low or intermediate temperature solid oxide fuel cells (IT-SOFC). Amongst these compounds,... 

In auction-based cloud investment environments, consumers desire the least possible cost and high satisfaction, while providers seek strategies to maximize profit and return on investment. In these environments designing an adequate resource allocation that can satisfy both consumers and providers is of utmost importance. Yet, most available models in resource allocation focus on providers’ needs and do not concern themselves with the consumers. Therefore the present study aims to present an efficient and optimum model for resource allocation problem that takes into account various factors, e.g. resource price, service quality, reputation and fairness, and is capable of satisfying all honest... 

In this dissertation, we will attempt a discussion of some ethical implications of genetic enhancement and present an argument against certain group of enhancements. We will demonstrate that this discussion requires a distinction between therapy and enhancement, therefore the arguments for and againt this distinction will be examined but it will be adopted in the end based on its merits. We will also show how genetic enhancement is a real possibility that will be available for consumers in the near future; and how probing the ethical issues surrounding the technology is quite necessary. We will then turn our focus to different theories of normative ethics and an examination of their merits... 

English research articles (henceforth RAs) have evolved into a vital medium for conveying and disseminating scientific knowledge. Mastering textual and linguistic conventions of academic prose assists English native and non-native authors in writing scientific RAs. Lexical bundles (LBs) refer to word combinations that co-occur frequently in a particular register (Biber, Johansson, Leech, Conrad & Finegan, 1999). In fact, they are an integral component of “fluent linguistic production” (Hyland, 2018, p. 4). For more than a century, LBs have attracted researchers' attention in corpus-driven studies, although the extent to which LBs vary between English native and non-native authors remains... 

Natural gas contains small amount of benzene, toluene, ethyl benzene and meta-xylene (BTEX). These compounds are soluble in amine solutions and accumulate in aqueous amine solution during sour gas removal process. They produce problems such as foaming in amine adsorption columns. The aim of this work is to study BTEX removal from aqueous amine solution by means of activated carbon. Three different commercially available granular activated carbons were used in experiments. Experiments were divided in static and dynamic adsorption categories. In the static tests, equilibrium adsorption of all three activated carbons were performed and the most effective activated carbon sample determined by... 

In this study some experiments were performed to investigate the effect of sweep angle on the transition location of laminar flow to turbulent flow. Three half wing models were used, each having a different sweep angle but with the same aspect ratio in various angles of attack. Two flat plates were used at the ends of the swept wing models to prevent the flow from rolling up over the wing. By simulating flow over infinity swept wing by eliminating tip vertices, the effect of sweep angle on flow transition phenomenon was investigated.
The experiments included the study of transition flow via hot-film sensors, which were glued on the wing surface. We found that the small leading-edge... 

Both handling and ride comfort play an important role in the performance and quality of a vehicle, and all the vehicle companies in addition to power and transmission system, pays special attention to these properties in the way of improving their products. This thesis is performed with the aim of study on effects of rubber bushing's characteristics of suspension system on handling behavior of a homeland built vehicle (pride). Role angle, slip angle, yaw rate and lateral acceleration are interrelated and are important quantities in studying on handling behavior of a vehicle. We have chosen slip angle as one these quantities and studied on effects of rubber bushing's characteristics on slip... 

due to high mineralization rate of Zinc oxide، chemical and physical stability, non-toxicity and low price as the most promising photocatalysts studied, although its use is not too satisfactory. Because of the wide energy gap(3.2 ev) and for photocatalytic activity needs to UV light Unfortunately, the solar spectrum is made up only 5-7% of UV light, while 46-47% is the spectrum of visible light and infrared. Doped zinc oxide nanoparticles with metal and non-metallic atoms could increase the photocatalytic properties under visible light irradiation. In this research, nanoparticles of zinc oxide was doped by fluorine as Dopant. The results showed that photocatalytic activity of the modified... 

Implant primary stability is a crucial component of implant survival. Primary mechanical stability is correlated with implant type, surgical technique, quantity and quality of bone at the recipient site. Since bone integration (BI) significance has been acknowledged, a variety of techniques have been developed to quicken BI and achieve faster fixation. Studies have shown that material type, and many surface properties, including as surface composition, roughness, topography, and energy, have a significant influence during the early stages of bone integration to the implant. In this work, we did synthesis one-dimensional nanoneedle-like arrays of hydroxyapatite using the injection method... 

In this thesis, equations related to large deformation of a polymer were derived by considering viscoelastic effects. To express type of material behavior which includes elastoplastic and viscoelastic property at the same time, two-layer viscoplastic model was used. An axisymmetric model was used for modeling problem in finite element software. By derivation of parameters related to two layer model and entering them in finite element software and also entering other properties required to model the forming process, modeling was performed by special profile connecting input and output sections. Due to favorable properties of spline functions, profiles used in die geometry, were selected from... 

In this project, a ceramic biocompatible coating was applied on Titanium which is included Hydroxyapatite by AC Plasma Electrolyte Oxidation method. First, coating was performed in 5 different solutions and various duration in 500mA/Cm2 as a current density. Then, by microscopic and macroscopic images and size of porosity and also thickness of coat, 3 solutions were chosen for adding nanoparticles: Solution 1 which includes NaH2PO4 and Ca(CH3COO)2 , Solution 3 which includes Ca(CH3COO)2 and Na-Beta G and Solution 4 which includes Ca(H2PO4)2, HMP, NA2(EDTA) and Ca(CH3COO)2 . Also the time 10 minutes was chose as a appropriate time. The average of the porosities size in solution 1 was about... 

Stop-skipping and timetable synchronization in a transit network for subway operation are two effective strategies to reduce passengers' total travel time.Most of the current research on the topic does not consider stop-skipping strategy and timetable synchronization simultaneously. This paper proposes a mixed-integer programming model based on passenger smart-card data concerning the trains' capacity to minimize passengers' total waiting time and in-vehicle time and maximize the number of passengers who successfully reach their destination. Since increasing the number of trains, stations, or the study horizon, exponentially increase the size of the problem, seeking practical methods to... 

For many reasons the Montecarlo method is chosen for investigation of problems like shielding. Nowadays, superiority of utilizing the codes based upon Montecarlo methods such as using cross sections with continuous energy or using exact models of complex geometries, is obvious for everyone. But obtaining results with least possible variance is extremely important. variance reduction methods usedfor achieving exact results with less calculating time. Up to now in the MCNP codes, many methods have been utilized for reducing the variance. One of the methods which have recently attracted attentions is using the importance function. For obtaining importance function we need to solve the... 

One of the most vital aspects of understanding the traffic phenomenon is scrutinizing the traffic transition status, such as the transition from free flow to congestion. The Percolation Theory is a renowned theory focusing on analyzing various network types to detect the critical zones, which are the zones including links that are important to control to improve stability. By calculating the quality indices of network links, the Percolation Theory can simulate the traffic percolation propagation in the network and determine possible critical zones for further analysis. Most studies in this field assume access to data of several traffic parameters for the entire transportation network, such...