Sharif Digital Repository

Today, with improvements in industries such as the sensitive equipment’ industries and the optics industries which need great precision for their optimum performance, the need for a vibration-free environment is felt more than ever. The main objective in this thesis is the effective reduction of the effects of ambient vibrations on points on an optical concrete table using active control. In this research, other than separating the table with the passive method, the reduction of vibrations with active control and the LQR algorithm is investigated. In order to study the dynamic characteristics of the table and to observe the active control process better and more carefully, finite element... 

The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels.... 

Along with the emergence of the smart city concept and the increasing demand for a wide range of vehicles, the Internet of Vehicles (IoV) has attracted a lot of attention by providing numerous benefits including vehicle accident warning, reducing pollution levels and traffic congestion, as well as entertainment services. Furthermore, IoV offers various services combining Vehicular ad hoc networks (VANETs) and IoT in smart cities. However, these types of networks are exposed to a variety of security and privacy risks due to the wireless nature, because the sensitive message is transmitted through an insecure channel in the IoV-based smart city environment, therefore, it is necessary to... 

Separation of biomolecules such as enzymes is the most important part of biotechnology process which 10-90 % of costs is for separation and purification. There are several methods for purification of bio materials and one of them is chromatography which use in enzyme purification but this method have several problem such as cost ,time consuming and scale up Because of this a suitable alternative demands for industrial separation. An alternative is aqueous two-phase systems (ATPS). In this project was studied about partial purification of alkaline protease produced by Bacillus licheniformis ATCC 21424 in aqueous two-phase system and comparison with chromatography method. an aqueous two-phase... 

The use of wearable surveillance systems and wireless body sensor networks is an economical solution to medical care, which is capable of detecting abnormal conditions early, and by controlling the health status and enabling one to engage in normal and daily activities, improves the patient's quality of life. Information and communication security is very important in this area and its violation may even endanger the life of the patient. The selection and application of the appropriate security mechanism for a wireless body sensor network is subject to consider the requirements and limitations of the network. One of the most important security requirements in this area is the... 

With the expansion of the Internet of Things (IoT) and the growing need for real-time data processing, cloud computing has been adopted as a solution for convenient access to large-scale computational resources. However, transmitting massive volumes of distributed data to the cloud can lead to increased network congestion, latency, and reduced efficiency. In response to this challenge, edge computing has emerged with the aim of performing computation and storage closer to data-generation sources, attracting the attention of both researchers and industry practitioners. The proximity of edge nodes to IoT devices reduces latency and improves the utilization of data; nevertheless, the limited... 

Confronting with cosmic rays in electronic parts of space systems, especially in processors and their peripherals, has always been noteworthy topic. By decreasing the aspects of transistors and their voltages, fault occurrence problem in digital integrated circuits not only has been increased in space systems, but also infects on mission critical systems that work at ground level. Since there are many reports about the effect of high energy particles, like neutrons which are present in earth atmosphere, in sub-100 nm digital circuits.In this thesis we are discussing about architecture level techniques for hardening processors against soft errors of radiation.It has been done for each part of... 

In this project rotational barrier around the C-N bond in 4-ethyle-morpholine- carboxylate has been studied using DNMR spectroscopy. Spectra were taken at variable temperature, and then with simulation of bandshape broadening pattern at coalescence region, rate constants of exchange were obtained for all temperatures. For simulation of line-shape broadening Spinworks software was used, that with two interfaces made possible simulation with two bandshape simulator programs, DNMR and MEXICO. The rate constants obtained from simulations, were used for calculation of thermodynamic activation parameters (∆G#, ∆H#, ∆S# and Ea). ∆G# 298 value of 13.66 Kcal/mol for 4-ethyle-morpholine- carboxylate... 

We study colorings of quasiordered sets (qosets) with a least element 0. To any qoset Q with 0 we assign a graph (called a zerodivisor graph) whose vertices are labelled by the elements of Q with two vertices x; y adjacent if the only elements lying below x and y are those lying below 0. We prove that for such graphs, the chromatic number and the clique number coincide  

The cornea is a transparent, avascular, multilayer, connective tissue. When the erosion process of these cells occur, where natural and quick restoration is expected, corneal disorders begin. Regeneration of corneal tissue, using a biocompatible method is a great point of interest. Nowadays, scaffold based on amniotic membrane is used as a basement membrane in the regeneration of corneal tissue. Lots of researches focused on using auto graft scaffold to decrease the inflammation and infection of an allografts and synthetic scaffolds, while overcoming amniotic membrane’s weak mechanical properties. The aim of this survey is to construct an appropriate scaffold from patient’s own blood to... 

Today's modern industrial control systems (ICS) and SCADA infrastructures, use industrial networks to communicate with the sensors and actuators installed in the field. In recent years the increase in use of standard protocols in this networks, and also the connection of industrial networks to the internet introduced new challenges in the area of industrial network security. The difference in the property, size, and requirements of this networks in comparison to legacy computer networks have made the legacy security solutions such as firewalls and IDS to not have enough efficiency. Some researches work on implementing new solution to meet the requirements of industrial networks in the area... 

Free-Space Optical (FSO) communication has received an increasing attention in recent years with its ability to achieve ultra-high data rates (at the order of multiple gigabits per second) over unlicensed optical spectrum. A major degrading factor, particulary in long links is the stmospheric turbulence induced fading. In this thesis, we use spatial diversity and use and make several contributions to the performance analysis of MIMO (Mutli Input-Multi Output) FSO systems. We use MRC(Maximum Ratio Combining),EGC(Equal Gain Combinig),SC(Selection Combinig) and yield significant performance improvments. Finally we import the charectristic of different beamshapes and yields performance...