Sharif Digital Repository

Most motorcycles in developing countries use carburetor systems as the fuel delivery method especially for models with the cubic capacity of less than 150 cc. However, a small gasoline fuelled engines operating using carburetor system suffer from low operating efficiency, waste of fuel and produce a higher level of hazardous emissions to the environment. A retrofit fuel injection system (FIS) is a system that is developed to entirely replace the conventional carburetor system to improve its fuel economy and exhaust emissions providing a low-cost alternative in an effort to reduce fuel costs and air pollution. In this study, an electronic control unit (ECU) is designed for a fuel injection... 

Gas turbine engine control is a demanding task that requires the regulation of the thrust as well as the satisfaction of the limitations such as engine aerodynamic instability, over temperature and over speed. Fuzzy logic is an attractive technique for the control of poor understood unmodeled, or complex systems especially where the experience of human operators is available to provide qualitative rules. In such cases, it has been found that control decisions can be made on the basis of linguistic measures or fuzzy algorithms. The controller that is designed on the basis of this theory is called fuzzy logic controller. The main objective of this thesis is hardware implementation of fuzzy... 

This work describes the effect of hydroxyapatite with different morphology including nanorods and whisker on the properties of hydroxyapatite/polycaprolactone (HA/PCL) composite. Biodegradable polymer/Hydroxyapatite (HA) composites with the morphology of nanorods and whisker of (HA) as bone replacement scaffolds are synthesized by sol-gel and hydrothermal methods, respectively with a Ca/P ratio of 1.67 and 20:80 (HA/PCL).The crystallization behavior and porosity of HA/PCL composite are studied by scanning electron microscope and X-Ray diffraction. The response of bone marrow-derived human mesenchymal stem cells (hMSCs) in terms of cell proliferation and differentiation to the osteoblastic... 

The present study is work on fabrication and characterization of a chitosan/ gelatin/ Mg substituted hydroxyapatite nano composite scaffold for bone tissue engineering. At the first step pure and Mg-substituted hydroxyapatite (HA) (Ca10-xMgx(PO4) 6OH2) nano-hexagonal rods with 14–45 nmdiameter.for this, calcium nitrate, magnesium phosphate hydrate and potassium dihydrogenphosphate were used as precursors for Ca, Mg, and P, respectively. Calculated amounts of magnesium ions (Mg+2) especially from 0 to 8% (molar ratio) were incorporated as substituted into the calcium sol solution. Deionized water was used as a diluting media for HA sol preparation and ammonia was used to adjust the pH= 9.... 

In present work, hydroxyapatite nano-rods are synthesized using a simple sol-gel method with calcium nitrate and potassium dihydrogenphosphate as calcium and phosphorus precursors respectively and ammonia was used for adjusting the pH=9. To obtain rod shape hydroxyapaite powder, multi wall carbon nanotubes were added to the solution, nHA powder was calcinated at 60 and 450 ℃. In second step, chitosan-gelatin/nanoHA solution were prepared by blending chitosan and gelatin in different concentrations with nanoHA powder, then the solution was freeze dried to maintain a composite scaffold. The prepared HA powder and bio-composite scaffold were characterized by X-ray diffraction (XRD), field... 

Nervous system plays an intricate biological process of man body.Damage of nervous system has serious consequences and is hard to recover, as well as the other parts of the body may not work properly. Many strategies have been used to repair spinal cord injuries in which the main objective is to improve the regeneration of axons and functional recovery. The purpose of this research is introducing neural tissue engineering concepts (e.g. scaffolds, stimulation and etc.) and also design and fabrication suitable for neural tissue engineering. For this purpose the combination of biodegradable polymers (chitosan),conductive polymer (poly-aniline) and carbon nanosheets (graphene) was chosen as the... 

Energy management in vehicles is ann important issue, because it can significantly influence the performance of the vehicles and component sizing., Although the bbatteries have been widely used in electric vehicles (EVs), However the large current impact of battery cycle life is still a difficult problem that remains to be resolved and because of that, Hybrid Electric Vehicles (HEVs) areis the way that allows to to achievinge the advantages of both engines.Hybrid cars uses both an electric motor and internal combustion engine (ICE) used together, so, itwhich can benefit from the advantages of both engine types. ImprovImprovement ofing energy management in (HEVs) can providedeliver important... 

Assessment of the probability of collapse or exceeding other limit states is one of the major goals of Performance-Based Earthquake Engineering. Moreover, other beneficial materials such as estimation of loss of money and downtime, which make it convenient for decision makers to judge the condition of a structure and take wise steps about it, can be drawn from the results of such an assessment.Current work investigates the probability of collapse and also immediate occupancy limit states at three discrete hazard levels of 50%, 10% and 2% in 50 years and also by utilizing mean annual frequency approach for three archetypes of steel special moment-resisting frames of 4, 8 and 12 stories.Ten... 

"Programmable networks" are to facilitate and evolve the computer networks. Specifically, Network Defined Software (SDN) is an advanced and innovative solution in the new computer network in which the hardwares are completely independent of the control and decision regarding data transfer. Based on this logic, network management becomes much simpler and enables innovation and new solutions for different parts of the network. In SDN, the program or network intelligence is logically present in software-based controllers (on the control panel) and can be changed and programmed, and network devices are converted into network packet sending hardware (on the data page) through an interface, Such... 

In the recent years, cloud data center issues have been the center of attention. Also for them topologies with multi paths between end hosts are offered. For use of multi path traffic engineering is essential. Researches show congestion occurred in the cloud data center networks, because the mean of link utilization is down. This means, some of links are congested while there are some other with much available bandwidth. Currently, the most common method is Equal Cost Multipath (ECMP) algorithm for routing flows in the data center network. ECMP decides on routing without any attention to network congestion condition. There, may be two big flows placed in the one path and it causes creation... 

The 60 GHz high speed technology, is the interesting category in network world nowadays. In this study, we consider one of the 60 GHz technologies as it is called WiGig. WiGig works under IEEE802.11ad standard, one of the WLAN standards that works at 60 GHz frequency band. We have surveyed the total MAC and physical layer of this standard to find the way to enhance the MAC protocol. This MAC protocol is applying the CSMA/CA and TDMA methods to access the channel. We have applied the CSMA/CA in our thesis that is a contention based access method. We found that with this method our network is not fair. Since there are not any studies about the value of Fairness in this standard, we... 

The rapid growth of information on the web and the need for information sharing on one hand and also as news plays an important role in our life and internet becomes the biggest repository for keeping this news on the other hand, lead us to research in this domain.
In this thesis, we introduce a new framework for searching news by considering the relation between news and events. This framework called NewsSe. NewsSe considers news as a series of events in order to cover all aspects of news. NewsSe uses Domain Ontology and Event Ontology to extract the concepts and relations existed in news. NewsSe consists of 4 different modules. NewsCr is a crawler which uses a new methodology for... 

Security has become more important in IT systems. Thus, to protect such systems from related potential threats and harms, robust and dependable security solutions should be devised. In designing security systems, a number of other issues such as assurance and verifiability are also of concern. Due to their mathematical nature, formal methods are very suitable for the above purposes. Using these methods, one can accurately define a system, its boundaries, and the requirements from design. It also makes it possible to verify that the design meets the requirements. In this dissertation, we propose a general IT security system using RAISE specification method. To do so, the specification...