Sharif Digital Repository

With the expansion of wireless communication technology and the advent of the fifth generation of mobile communication, there is a growing need for broadband systems. Consequently, RF engineers are currently focusing their attention on broadband transceiver systems. The low noise amplifier (LNA) is a critical component in the receiver of a telecommunication system. In this research, the design of a broadband LNA in the K and Ka frequency band (18 ~ 40 GHz) is presented. The main challenge in designing a broadband LNA lies in achieving simultaneous power matching and noise matching through the input impedance matching network. Various types of broadband impedance matching networks have been... 

Tehran possesses various environmental crises due to excessive population growth, a huge increase of vehicles and heavy concentrated industries. One of the most important concern is air pollution. Spectral Analysis by discrete Fourier transform are described and applied to harmonic analysis of time series for detecting Present periodicities.
The current work proposes an approach for the determine the contribution of different frequencies to the data variance using air quality measured data. In this research, we present a comprehensive review of methods for spectral analysis of nonuniformly sampled data. Because of The air quality data in Tehran have irregular sampling periods and... 

In this study, the magnetite protective oxide layer was successfully formed on carbon steel substrate in an alkaline solution by an electrochemical method. The electroblackening was performed at a constant potential of 2 volts and in a 50 wt% solution at 75 ° C for 10 minutes. The properties of coating characterized using X-ray diffraction, field emission-scanning electron microscopy, polarization test and visible light spectrophotometery and porosity and thickness of oxide coating investigated. By adding 50 grams per liter of each of nitrate and chromate oxidizers, the porosity of oxide coating decreased from 24 percent to 14 percent and coating thickness increased from 1 micron to 3... 

Currently PM2.5 is a major air pollution concern in Tehran, Iran due to frequent high levels and possible adverse impacts. In this study, which is the first of its kind to take place in Tehran, composition and sources of PM2.5 and carbonaceous aerosol were determined, and their seasonal trends were studied. In this regard, fine PM samples were collected every six days at four station for two years from February 2014 to February 2015 (first phase) and March 2015 to February 2016 (second phase). The samples were analyzed for ions, organic carbon (including water-soluble and insoluble portions), elemental carbon (EC), and all detectable elements. The source apportionment was performed using... 

According to expanding penetration of Internet and the increased power of processing devices in the recent years, softwares are incisingly used for daily acitivies. The variety of hardware configuration and operating system of such devices leds the companies to take advantage of cross-platform software development methods. Although the production of cross platform software, resude development costs, it results in an specific type of faults known as platform-specific failures. These faults occur when software is running on specific platforms, and therefore, to identify and resolve them, the software test process should be performed on different platforms. To deal with this problem, we present... 

The numerical simulation of asphalt concrete and pavement has gained considerable attention in recent decades. Information about the response of asphalt pavements during construction and in-service traffic loading is required by pavement specialists for improvement of pavement analysis and design methods. The goal of this study was to propose a constitutive relationship and a numerical modeling method for asphalt concrete compaction in the laboratory and in situ. Asphalt binders exhibit rate-dependent viscoelastic and viscoplastic mechanical behavior in asphalt concrete. The current study examined the viscoelastic and viscoplastic mechanical behavior of asphalt concrete under various loading... 

Many countries use a single water meter for multiple units within a building. This creates a cost externality where the cost of water consumed is spread over all units. Using administrative data from Tehran Water and Wastewater Co. for 2013 and 2014, we find an increase in the number of units on a communal meter on average increases per unit use by 0.4 percent. Estimation at different levels of units reveals that almost all communal meters have higher per unit water use. The results suggest that the externality is responsible for 2.7 percent of water consumption in our sample.
JEL classification: L9, Q25, Q50, Q58
 

In recent years, the user interface of web-based applications has become more and more complicated. Various technologies, architectures, and tools are being used to create a modern user interface. Users interact directly with the user interface, so its functionality has a significant impact on their satisfaction and it is required to design special test suites for the user interface. Furthermore, we need a method to measure the quality and effectiveness of test suites. An effective test suite is a test suite which is able to detect real faults. But this definition is ambiguous, and hence, not practical. A method called Mutation Testing solves this problem and instead of real faults, uses... 

Laufer and Hulstijn (2001) proposed the Task-Induced Involvement Load Hypothesis stating that in the retention of new words in an incidental context, tasks with higher involvement load will be more effective than tasks with lower involvement load. The present study aimed to examine whether the retention of vocabulary is enhanced with an increase in the amount of task-induced involvement load in an intentional learning environment. Moreover, it was investigated whether proficiency level of learners had a role in the effectiveness of the vocabulary tasks with different involvement loads. Four groups of university students, male and female, participated in the study. They were given a TOEFL... 

Nowadays, Internet of Things is considered as a global infrastructure to establish communication between physical world and virtual world by using existing technologies. Its purpose is enabling things to establish communication with anything and any person in any time and any place by using existing networks and services. This technology makes different aspects of people's life smarter, facilitates doing works, and increases the quality of people's life. But, the development of Internet of Things faces to fundamental challenges that one of the most important of them is security and privacy preserving of users. According to the projects of European Research Cluster on the Internet of Things... 

Wireless Body Area Network (WBAN) is a set of various physiological sensors for remote monitoring and controlling of the patient’s health status. Detection of anomalies, containing faults and physiological stresses, and distinguishing between them can eliminate the need for constant presence of specialists and decrease the occurrence of False Alarm Rate (FAR).A supervisory hardware platform for WBAN architecture is introduced and implemented in this thesis. The proposed architecture contains three sensors for recording of biomedical signals, heart rate, SpO2 and body temperature simultaneously and transmitting them to central node wirelessly through Wi-Fi standard. This proposed architecture... 

In this projekt, nanophotocatalysts containing metal oxides and oxy-acids based on the nanoporous materials were synthesized. The photocatalytic properties of the prepared samples were evaluated by the photodegradation of day moleculs in photocatalytic systems. The catalytic results revealed that Ag3VO4/Cu-MOF/rGO exhibits noticeably an improvement in both efficiency and rate of AB92 photodegradation in comparison with the pure Ag3VO4. Using different scanning mechanisms for the catalytic properties of the synthesized nanocomposites, it was clearly demonstrated that the anionic superoxide plays a decisive role. Reduction of 4-NP in the presence of NaBH4 was also used to investigate... 

The purpose of this thesis is to obtain a logical decision making for the landing of multiple electric vertical takeoff and landing (eVTOL) aircraft that are simultaneously approaching a skyport. This research was conducted in response to the expansion of cities and the increased demand for transportation. In fact, the increase in population in cities makes the existence of a new mode of air transportation unavoidable, and in this regard the landing and take-off of such aircraft is very important because using a control tower for managing the take-off and landings of these aircraft doesn’t seem possible. To do this, the problem of simultaneous landing of multiple eVTOL aircraft was divided... 

Object oriented analysis and design hase become the paradigm of choice for many software builders. For, it has filled the gap between the problem domain and its solution. However, most of object oriented methods can not prove their model against the software specification and do not ensure that they realize what the customer needs. Formal method is one of the methods used for building softwares. Since a software is specified accurately by this method, the specification can be used to build the software in addition to being used as a test for the final software. A specification can be refined to code step by step. Since an object oriented model is close to problem domain in real world, a... 

Medical ultrasound imaging is one of the common imaging methods in modern medicine, which is used to diagnose and even treat some diseases due to its cheapness and harmlessness. Medical ultrasound transducer arrays have a significant error rate. They are a major cause of failure in ultrasound imaging systems. This problem causes a noticeable decrease in the quality of the images and medical misdiagnoses. The topics of accurate detection of the location and severity of the error or failure, as well as the compensation for weak transducers by signal processing methods, have received less attention from predecessor researchers. In this thesis, an innovative method for accurate error detection... 

One of the key issues in the design of vessels is their proper stability and performance in waves. Therefore, the use of twin-hull vessel designs such as conventional catamaran and SWATH is suitable for improving stability and seakeeping quality. Although SWATH has a better seakeeping quality than a conventional catamaran, it has been observed that at high forward speeds, especially in head waves, the vertical motions of the vessel is greatly enhanced. Various methods such as correction of the hull form and the use of fin stabilizers can be used to modify SWATH vessel motion behavior. These control surfaces can respond appropriately to the dynamic forces from the waves, reducing the motions... 

Nowadays, with the development of machine learning and deep learning on one hand, and the dramatic increase in the amount of information available and the complexity of models on the other hand, it is practically impossible to implement learning algorithms on a single node. Thus it is inevitable to distribute learning algorithms on several machines. In a distributed system, the main operations are divided into smaller tasks and performed by different nodes. The final result is then calculated by exchanging messages among the existing nodes.In this thesis, a method is introduced to compute the gradient of a massive data set in a distributed system. In this problem, there are a number of... 

Concrete is the most used man-made material on earth, albeit is responsible for the ten percent of the carbon dioxide gas emitted by human to atmosphere. Also the most important constituent of concrete, hydrated cement, has a sophisticated structure yet its precipitation, composition, mechanical properties and morphology has been the subject of dispute among cement researchers. On the other hand, according to the increasing focus on sustainable development, design of optimum materials has become important. Several models have been proposed for the structure of cement hydrate while every model has its own advantages and disadvantages. Recently, a combinatorial model at atomic scale has been... 

In this study, the feasibility and optimization of recovering uranium from the tailings of the Meidok copper plant using heap leaching on a laboratory scale were investigated. The initial phase involved evaluating the agglomeration process and stabilizing particles. Parameters such as drum speed, acidity level, coarse-to-fine particle ratio, and residence time were examined and optimized. Following the optimization of the agglomeration process, column leaching tests (heap leaching method) with dimensions of 50 cm in height and 10 cm in diameter were performed. The selection of an appropriate and optimized heap leaching system considered parameters like solution injection rate, pH, and...