Sharif Digital Repository

Congenital heart defects are a type of heart diseases that some babies get at birth. These diseases generally have symptoms such as shortness of breath, headache, impaired blood supply, hyperplasia of the lungs, enlarged heart, and so on. In the past, open heart surgery was commonly used to treat such diseases, which was a costly and risky procedure. But over time, occluders made it easier. An occluder is referd to a device that is generally minimally invasive in the area of the fault and could block it. The occluders are usually braided type, with inside polyethylene fibers, where tissues can grow and clogs the defect over time. Although occluders have greatly increased the success rate of... 

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... 

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... 

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,... 

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... 

A new types of architected cellular materials are those with negative poisoon’s ratio named auxetic. This materials indicate unormal behavior under different loads as if they were stretched in one direction, they also expanded in other directions and if pressure is exerted in one direction, they are compressed in all directions. Auxetic materials can improve mechanical properties such as shear strength, strength to weight ratio, thoghness, energy and vibration dissipation and crack expansion due to fatigue.The useful features of this material have been taken into account in a variety of industries, including the automotive industry, in the manufacture of parts such as body and bumper,... 

Deduplication is a data reduction technique, which eliminates redundant data by storing only a single copy of each file or block, along with a reference to the unique copy of data. Deduplication reduces the storage space and bandwidth requirements of data storage systems, and becomes more effective when applied across multiple users. All deduplication techniques use cryptographic algorithms to detect duplication instead of byte-by-byte comparison between input data and all previously stored data. In this manner, the data stream is divided into non-overlapping chunks of data. Then, the hash values of non-overlapping chunks create an exclusive criterion to identify duplicates. In this thesis,... 

With ever increasing amount of digital data, numerous efforts have been made in recent years towards improving reliability and availability of data storage systems. Previous studies have reported significant gap between estimated failure rates and observed failure rates in the field. This gap is mainly due to neglecting correlated failures in Redundant Array of Independent Disks (RAIDs). Proposing a model to consider correlated failures can significantly improve reliability models. In this thesis, we present a reliability model which considers correlated failures in RAID arrays. In the propose model, we use a correlation probability to take into account the correlation of failures between... 

Hoganas is a gas based process which is more than a hundred years old. In this research, studying parameters affecting the quality of sponge iron like temperature, time, particle size, type of reductant, type and dimension of crucible were discussed. Groups of particle size was 0-150,150-500,500-1000microns and temperature range was 900, 950, 1000, 1100, 1150°C. Time of tests was between 2 to 30 hours.at 1000 °C and 10 hours maximum metallization degree was 94.76.while at 1100 °C and 5hours better metallization degree was achieved. at 1000 °C and 5 h, particles with 500-1000micron size had better result than other groups.at higher temperature effect of particle size was gradually decreased... 

The reconstruction of SSD arrays in enterprise storage systems often incurs significant performance degradation due to resource contention between user I/O requests and reconstruction operations. This study introduces LsTReX, an innovative framework for capturing both short-term and long-term reuse patterns, enhancing performance during reconstruction by accurately predicting I/O access patterns and redirecting read and write requests to a surrogate device. LsTReX maintains data coherency with minimal overhead using a logical-to-physical zone mapping table and sector maps, reducing array reconstruction time by up to 44% while achieving up to 60% IOPS speedup and 25% lower latency compared to... 

In recent years, with the remarkable advancement of genetic technologies, a vast amount of genomic data has become available to researchers. The analysis of these data introduces various challenges, one of the most important of which is Genome-Wide Association Studies (GWAS), aiming to identify genetic loci influencing traits or diseases. Conventional methods in this field are often limited to univariate analyses or fail to account for the complex structure of genetic data, and in many cases, they do not guarantee control over the Type I error rate. In this thesis, a novel method based on the Knockoff statistical framework and its extensions is proposed. Inspired by the idea of KnockoffGAN,... 

Reservoir computing, a computational paradigm nested within recurrent neural networks, offers a powerful framework for processing time-dependent inputs, exhibiting remarkable performance in tasks such as voice recognition and time series approximation. Recently, there has been a burgeoning interest in implementing reservoir computing in the realm of optics due to its potential for reduced power consumption, increased bandwidth, and enhanced parallelization. The crux of implementing a reservoir computer with artificial neurons lies in utilizing a nonlinear function with a delay line, which accumulates temporally delayed outputs of the function, integrates them with new inputs, and feeds them... 

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... 

The air distribution is the main factor of contaminant transportation in cleanrooms. The experimental method is the most reliable one for investigation of flow field, which the difficulties associated with it, has limited not only the examination of the flow field in cleanrooms, but also the improvement of their qualities. Most of the experimental researches in indoor air quality concern conventional rooms and do not take into account specific supply-exhaust diffuser configurations, which are used in cleanrooms. Using small-scale models can reduce the complexity and the cost of measurements. In this research, the 3D velocity field of a small-scale cleanroom is measured in three different... 

The aim of this research is to analyze the failure and investigate crack growth in graphene using peridynamic theory. The presence of spatial partial derivatives in the equations of classical continuum mechanics has led to the fact that methods based on this theory are not valid in displacement discontinuities such as cracks. Peridynamic theory emerges as a nonlocal reformulation of mechanics, uniquely well-suited for modeling discontinuities and dynamic fractures in both continuous and discrete media. Its adaptability extends to various dimensions, encompassing phenomena at the nanoscale. In the present study, based on the ordinary state-based peridynamic theory, we investigated the... 

In this thesis, a numerical analysis of micro chamber filling in centrifugal microfluidics is investigated. In the development of micro total analysis systems, it is often necessary to achieve complete and uniform filling of relatively large micro chambers. With centrifugal devices, these large micro chambers must often be orientated perpendicularly to the direction of centrifugal force and are usually bounded by materials with varying surface properties. On the other hand, the mixing characterization of two fluid by centrifugal microfluidic method has been also conducted. The multiphase flow analyses based on Eulerian-Eulerian approach have been conducted and the VOF method was used for ... 

The study on new rheoforming technologies of semi-solid alloys has recently been one main subject interesting many researchers and industrials, and so many new methods about preparing semi-solid alloy slurry and rheoforming process have been suggested. Among more than 20 proposed methods, only MHD (Magneto Hydro Dynamics) and EMS (electromagnetic stirring) methods has been industrialized. In this research, the semi-solid slurry of A356 aluminum alloy was fabricated by electromagnetic stirrer under different conditions of stirring current, stirring time and pouring temperatures. Then the semi-solid slurry prepared in optimum conditions was injected into a step-die cavity by a drop device and... 

During the various stages of uranium processing in Uranium Conversion Facility (UCF) in Isfahan, significant amounts of liquid waste stream is produced which is sent to evaporation ponds. In addition to environmental considerations, uranium recovery from existing pools is also economically feasible due to high concentration uranium in liquid waste. Several methods have been evolved over the years to remove dissolved uranium from uranium bearing solution. These methods are: chemical precipitation, liquid-liquid extraction, ion exchange and membrane processes. The purpose of this study is recovery of uranium from liquid waste of Isfahan UCF plant by using ion exchange method. Although this... 

Solid-State Disks (SSDs) offer advantages such as no mechanical parts, low power consumption, and constant read latency. SSDs, however, suffer from shortcomings such as erase-before-update requirement and limited endurance.Redundant Array of Independent Disks (RAID) are commonly used in storage servers to enhance performance and reliability. To further enhance system performance, one can employ efficient Input/Output (I/O) scheduling algorithms suitedto the disk structure in RAID-based systems.In this thesis, we present an I/O scheduling method to improve endurance and performance of SSD-based RAID systems. In the proposed I/O scheduling algorithm, read requests are sent directly to SSDs and...