Sharif Digital Repository

In this investigation, cellular structure of a weakly unstable detonation wave in H2/O2/Ar mixture is studied. The detonation is simulated using 2D reactive Euler equations and one step Arrhenius type reaction model developed by Mr. Barkhordari. The numerical technique is the high order Piecewise Parabolic Method on the basis of Godonov method. The numerical fluxes are computed based on a high-order extension of the Godunov's method; the piecewise parabolic method (PPM). The initial cell formation processes and different machanisms involved in cell size changes are studied. This study shows that the form of initial perturbation used to intrigate the instability of detonation is not important... 

Shape Memory alloys are a kind of intelligent materials developed in recent years due to their comprehensive use in medical, robotics, and other advanced sciences. Two main characteristics of them are shape memory effect and superelasticity put these materials in the category of advanced materials. Recently, the new branch of them attracted many studies which is the porous shape memory alloys. The importance of this class of material is related to their properties such as bio-compatibility, superelasticity and shape memory effect. Since shape memory alloys are usually expensive, a new field is developed known as functionally graded porosity distribution. This method is performed by... 

The coronary arteries of the heart are one of the most important arteries in the body's cardiovascular system, which carry oxygen and nutrients to the heart.Therefore, coronary heart disease is one of the most important causes of death in society. In this disease, when the adhesion of sediments and blood plugs to the walls of the arteries increase, the ducts become narrow and the circulatory system gets hard. As a result, the risk of heart attack and mortality increases.Due to the increase in mortality caused by coronary heart disease, working on treatment methods for this disease is important. Angioplasty and stent implantation in a vein are the latest treatments for this disease and have... 

The current research was conducted to investigate the sealing behavior of single-string and dual-string completion Packer. In order to transfer the oil from reservoir located underground to the surface, the string of tubings is used which is called oil well completion string. A typical completion string not only consists of tubings but also the other facilities such as safety valve, traveling joint, sliding side door and Packer as well. Some reasons including: the cost of drilling and challenges in setting wellhead equipment at some geographical situations, producing more oil and gas lead to extraction oil form more than one zone in the oil well. In addition, taking into the account that,... 

Nowadays, variable generation and renewable energy resources are increasingly penetrating the energy systems to supply the users' demand at the distribution grid. Variable Energy Resources (VER) can provide energy at a lower cost, and they also guarantee cleaner energy. Still, the uncertainty and variability from these resources' output can affect the net-load of the system at each hour. Besides, the issue of energy balance has always been a challenge for the energy distribution networks. A comprehensive way to unravel this problem is to use flexible resources. One of the crucial issues in the flexibility debate is meeting this need by different energy resources. It is always an issue for... 

One of the most important tools in industries such as oil, gas, mining and groundwater is inflatable packers. These tools are used for plugging and zonal isolation of a well. The most important member of this cylindrical tool is the elastomer, which is reinforced by metal wire ropes. These cables are placed at an angle relative to the axis of the cylinder and are wound in a helix shape. At both ends of the tool are rings that hold the cylinder. After running the tool into the well and placed in the desired position, by a pipe connected to it, fluid is pumped into it. This increases the diameter or inflation of the tool, and the outer skin of the elastomeric cylinder contacts the well and... 

In this project Mordinate and Eu-1 zeolite were synthesized by hydrothermal method and then bifunctional catalysts including acid-base zeolite and Pt-Al2O3 metal base were mixed and made using a planetary mill. The modified catalysts were detected by various methods such as XRD, SEM, FTIR. The aim of this project is to synthesize and characterize the modified catalysts and to escalate their catalytic properties. Our focus is primarily on the synthesis of zeolite-based catalysts modified with unique features such as having active acid sites, high thermal stability and appropriate selectivity for the purpose of investigating the mechanism and kinetics of the C8 aromatic Compounds... 

In this research Fe3O4 magnetic nanoparticles were prepared. To protect against oxidation, a shell of SiO2 was deposited on Fe3O4. Graphene oxide was prepared by the modified Hummer method and supported on the Fe3O4@SiO2 core-shell. Then, ionic liquid layer was impregnated on it. Afterward, PtAu nano alloy were synthesized on the surface of nanocomposite with the different molar ration including 100:0, 75:25, 50:50, 25:75 and 0:100. The as-prepared nanocomposite was characterized by SEM, XRD, and FT-IR analytical methods.For investigation of kinetically activity of catalysts, reduction of 4-nitrophenol with NaBH4 as reducer was used. The adsorption in different times was obtained by UV-vis... 

Neural Networks have been applied to Language Modeling to solve a major problem that N-gram language models could not overcome: discreteness of the words. Generally, neural networks were successful in solving this problem and improved Language Modeling by reducing the perplexity of the models. Neural networks can find grammatical and semantic connections among the words using word embedding which maps each word to a low dimensional feature vector of real numbers. In this research, different kinds of neural network applied to Language Modeling has been reviewed. Also, it has been tried to reduce the perplexity of Persian language models on a 100-million scale data set using a single-layer... 

Keyphrase extraction, as an important open problem of Natural Language Processing (NLP), is useful as a stand-alone task in the field of Information Extraction and as an upstream task for Information Retrieval, text summarization and classification,etc. In this study, regarding the needs in Persian NLP, artificial neural networks are adopted to extract keyphrases from single documents and a graph-based re-scoring method is proposed for multidocument keyphrase extraction. The proposed method for extracting keyphrases from multiple documents consists of two steps: (1) extracting keyphrases of each document in a cluster using a sequence to sequence model with attention, and (2) re-scoring the... 

This thesis examines the modal characteristics of the payload after connecting to the carrier via the adapter. Basically, the modal characteristics of a payload change after connection to the carrier due to the different stiffness of the coupling mechanism. In this report, it is attempted to split and model the assembly structural system into two substructures interconnected by the V band clamp mechanism. Then, each of the substructures analyze individually and the modal characteristics of the integrated system are extracted using the infrastructure coupling methods. The coupling method is the "Component Mode synthesis" (CMS) method and input data, dynamic and modal characteristics required... 

In recent years, word embeddings as the word representation have captured the attention of natural language processing (NLP) researches. One of the great advantages of word embeddings is their capability in representing the relationships of the words. Therefore, using word embeddings in NLP applications results in better performance.Despite widespread attention towards word embedding in late years, Persian word embeddings have not achieved sensible progress. One of the Persian word embeddings difficulties is related to that, Persian is a low-resource language in comparison with worldwide languages. Therefore, Persian word embedding quality is lower than English. Consequently, the accuracy of... 

Elderly falls are one of the leading causes of injury and death to this growing population. In this project, an elderly fall detection system has been designed and built in the form of a wearable device that allows the elderly to be constantly monitored by wearing it continuously. The system hardware is made in the form of a wearable watch that fastens to the left hand of the elderly and continuously monitors the signals of its three sensors, which are accelerometer, gyroscope, and magnetometer. The system continually applies its initial diagnostic method to the signals and sends motion information to a host computer via a wireless connection in the event of a fall. The primary diagnostic... 

This project has been conducted in two related phases: In the first phase, we have attempted to write a program capable of answering thematic similarity multiple-choice questions without utilizing any training data. The best performance in this phase was attained by the 25-topic LDA model using the Hellinger distance between the probability distributions of the poetic verses. This model managed to attain an accuracy of 42%, which is very close to the average human performance of 43%. In the second phase, two tasks of seven-class classification and binary classification were defined based on the p-value of the questions. To this end, the questions were initially ranked according to the... 

An optimal-fuzzy low altitude two phase CLOS guidance algorithm for a vertically launched flying vehicle is presented. In addition, the required relations for determining the proper rotation angle of interceptor in the launch phase are derived. The guidance algorithm is designed for a three point guidance system and utilizes fuzzy sliding mode control as a regulator to compensate the guidance loop errors. Furthermore, for the purpose of trajectory shaping, a fuzzy system was employed to calculate the augmented elevation angle. Finally, a multi-objective optimization algorithm is used to determine 20 unknown parameters of the guidance law and 11 parameters of trajectory shaping system.... 

Unique characteristic behavior of shape memory alloys (SMAs), known as shape memory effect (SME) and superelasticity (SE), make them an appropriate choice for innovative engineering. Design of SMA applications calls for development of constitutive models. To accurately predict SMA behaviors, employing a suitable model with low computational costs is required. In some experimental data, SMAs have coupling in mechanical and thermal behavior. Therefore, mechanical loading changes temperature of the material and variation in temperature affects the mechanical behavior as well. This behavior is called coupled thermo-mechanical effect. In SMA applications, since coupled thermo-mechanical behavior... 

In this thesis, an analytical solution is presented for pure bending of SMA curved beams with rectangular cross section and both loading and unloading stages are considered. Moreover, by appropriate simplification, its application in elastoplastic pure bending of curved beams made of regular materials is investigated. Elastic-linear kinematic hardening behavior of the material is assumed and both loading and unloading stages are considered. Exact plane plasticity solution of the elastoplastic pure bending of curved beams made of regular materials which exists in loading and is available for rectangular cross section has many unknowns and longsome equations. Therefore, it is difficult to use... 

News plays a very important role in stock market trading. Nowadays news from a different part of the world and about different fields can be accessed easily, and for a successful trade, it is necessary to analyze accurately and use this big data and information as soon as possible. For this reason, this thesis tries to present and study models based on Deep Learning networks and Natural Language Processing for financial news analysis and predicting stock indices movement. This research takes advantage of a language model for learning and representing news text, and beside this language model it uses deep learning networks at multiple levels to extract proper features from each news in a day...