Sharif Digital Repository

Air filter paper is a combination of cellulosic, polymeric and resin materials with a certain permeability to air, which is used to prevent dust from entering the internal combustion process.The purpose of this research was to study and make air filter paper, based on which 4 samples of automobile air filter paper were produced. Samples with a combination of 2 types of cellulose fibers, imported short Kraft fibers and long Bangladeshi Kenaf fibers (skin) and one type of polymer fibers, Polyester fibers with a type of self-networking water-based Acrylic resin with glass conversion temperature (Tg) About 33 degrees Celsius and in the range of 20% by weight with a mass of about 120 g/m2 were... 

AISI 4340 steel bars were austenitized at 900°C for 1 hour followed by heating at 740°C (ferrite and austenite region) for 100 min and quenching into a salt bath at 300°C for different times followed by quenching into water to obtain triple phase microstructures with 34 Vol.% ferrite and various martensite (or bainite) contents. Presence of three phases in adjacent of each other confirmed by metallographic analysis and TEM technique. Volume fraction of different phases was measured by image analyser. The results of optical microscopy showed that by increasing VM, morphology of martensite varies from uniform distribution of small spherical network particles to large blocky islands with... 

A methodology is developed for designing optimum passive energy dissipation systems using active control algorithms. A combination of stiffness reduction and increase of damping is utilized to reduce both acceleration and displacement response. In this method, first an active control system is designed using pole assignment and sliding mode control algorithm. Here, the methods to use the actives algorithms aremodified such that the resulting properties can be achieved by a passive control system using viscous fluid dampers. Next, a passive control system is designed to result in the structural properties close to those extracted from the actively controlled system. It is shown that this... 

The main goal of this study is to evaluate the seismic performance of HV circuit breakers of power substations and optimize their seismic behavior using base isolation systems. Iran is in a region with high seismicity and has experienced severe earthquakes in recent decades that have resulted in serious damages to critical infrastructures. These include power substations that are important during and even after an earthquake in providing electricity for homes, industries, amenities, emergency facilities, public transportation and more. The seismic performance of HV circuit breakers, which is an important equipment for power substations, has not been satisfactory in past earthquakes and has... 

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... 

In this study, a new resorcinol-formaldehyde xerogel was synthesized based on sol-gel technology and employed as a sorbent for micro solid phase extraction (µ-SPE) of BTEX and some selected pesticides from aqueous samples.
In the first part, a µ-SPE method in combined with headspace solvent microextraction (HS-SME) along with gas chromatography- mass spectrometry detection (GC–MS) was developed for the analysis of BTEX in aqueous samples. In our knowledge, this is for the first time that these two different extraction methods has been coupled to maximize the advantage of each extraction method. Influential parameters such as the peristaltic pump flow rate, extraction volume, extraction... 

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... 

In recent years, climate change due to greenhouse gases caused an increase in frequency and intensity of the natural disasters such as hurricanes, blizzards and floods. Moreover, it is anticipated that such events will increase in the future. As a result, power system decision makers are looking for methods to improve power system resiliency against such natural disasters with low occurrence probability and high impact. In this report, the distribution system resiliency has improved via placing remote control sectionalizing switches and micro grids formation during natural disasters. In this regard, the concept of resiliency and its characteristics along with the effect of remote control... 

In this investigation, silica-based iron-metal catalyst was synthesized by the Atomic layer deposited (ALD) method with iron-acetylate (Fe(acac)3) as a precursor in different loading dosages. The synthesized catalyst were characterized by nitrogen absorption and excretion (BET), by Field Emission Scanning Electron Microscope (FESEM), X-ray diffraction (XRD), and Temperature-Programmed Reduction (TPR), Fourier-transform infrared spectroscopy (FTIR), Atomic Emission Spectroscopy (ICP) etc.
The temperature range of 180 to 200 °C was determined for the self-limited chemisorption of Fe(acac)3 on the silica surface as the first and the most important step in a single atomic cycle. Also the... 

There are many methods for direction finding (DF) of radar targets, while the complexity and time elapsed calculation are their main drawbacks, thus the real time implementation of this methods are difficult. Artificial neural network (ANN) for DF is one of the optimum and good ways to implementation that have better result versus other techniques. In this thesis, direction finding problem for radar targets by using artificial neural networks have been studied. A new method is presented to detect the multiple targets simultaneously, that it can be implemented in digital form easily. Here one-dimensional DF by using uniform linear array (ULA) discussed and formulated, then the proposed... 

The problem of Origination of The Universe is one of the most important issues in the history of philosophy whether in western edition or in Islamic thought. The most problematic aspect of the Origination is Temporal Origination. From about 30 years ago as a result of the works of a famous American philosopher William Lane Craig, the debate between temporality and Eternity of the Universe became a fresh topic in western philosophy. In this research we want to survey the philosophical arguments for and against the temporality of the Universe based on the views of: W.L.Craig, Q.Smith and Allamah S.M.H Al-Tabatabaie.
 

The subgradient method is one of the most favoriate methods to solve discrete optimization problems. The Easy Implementation and flexibility enbles us to solve a vast types of complicated combinatorial optimization problems. However, the algorithm can be improved by adjusting its parameters and steps.In present research, we present a heuristic structure to modify and improve the algorithm. Then, the proposed algorithm has tested on special classes of discrete optimization problems such as Generealized Assignment and Uncapacitated Warehouse location problems. The results show that the proposed algorithm can improve the efficiency of the classic form of subgradient method.The three main... 

This thesisconsiders new fundamental approaches to yield heterogeneous catalysts in to three sections. The first section described the immobilization of the molybdenum-Schiff base complexes in pores of SBA-15 in two different methodologies depending on the actual structure of the complexes., (i) stepwise formation of the complex by initial covalent anchoring of one of the components and consecutive solid phase synthesis consisting of the condensation of the other components of the salen complex (iii) one-step complex immobilization by covalent binding through the ligand.Based on the first methodology, we report the preparation of ordered mesoporous silica SBA-15 containing a molybdenum... 

A complete 6DOF flight dynamic model of an elastic flapping wing (EFW), integrated with unsteady aerodynamic theory is developed. In this respect, initially efficient high fidelity modules for EFW structural dynamics (SD) as well as unsteady aerodynamics loadings (UAL) to be coupled with its flight dynamics are prepared. A modal approach is followed to model structural dynamics of plain and 3D EFWs. This is in contrast with the Euler-Bernoulli beam theory that is mostly utilized for SD in the existing literature. In addition, due to the possibility of large wing deformations as well as the existence of non-linear displacement regime for realistic EFW flights, non-linear modal approaches such... 

With the development of electrical engineering and the electrical industry, the use of copper and its alloys has grown tremendously. On the other hand, with development and modern industry, it will be difficult to meet the requirements such as high performance, cost reduction and weight reduction of the structure if only one metal material is used in the production of the desired component or structure. Aluminum can be used in combination with copper because of its properties such as high thermal and electrical conductivity. Al/Cu bonding is used in industries such as microelectronics, automobiles and batteries. This study has investigated parametrically the feasibility of uneven bonding of... 

Shadows are one of the most important details in graphical images. There exist many shadow generation algorithms each of which suffers from some problems. High processing time and ill-shaped shadow borders, known as alasing, are some of such problems. In this paper, we propose a heuristic method based on standard shadow map technique, named rotated shadow maps, to generate excellent hard shadows. Our method uses some shadow maps which are generated from the same view but objects are slightly rotated around the center of view area. Rotated shadow maps can be considered as an independent hard shadow generation algorithm. Also it can be combined with other shadow map based approaches. Utilizing...