Sharif Digital Repository

In the present study, the effects of increasing the value of shale gas production, either due to increased production or price increases, have been studied on economic variables such as employment, wage, property value and the number of births. In this regard, the data for each of these variables was used at the county level in the United States of America between 2000 and 2011. In order to estimate the desired effects, counties are divided into two types of boom and non-boom counties. The findings indicate that increasing natural gas production will lead to more employment and wage growth in boom counties than non-boom counties. Also, during the period of increasing production, the value of... 

This work describes a new approach to the so called “Engineering Requirements Process” based on abilities to develop a meaningful task. We first describe how a meaningful is created from scratch and then we explain how requirements could be added to a level where the predefined task is no-longer doable. The process is then applied to design of an aircraft wing to show how requirements could be avoided during a design process. The method is expected to be applicable to all aircraft sub-systems and parts. The process is particularly useful where all design requirements are not available at once, rather they increase as time goes on and new stakeholders become apparent. In this work, we have... 

In this study, orthosilicate materials with chemical formula of Li2MSiO4 (M one or two transition metal/metals) were investigated experimentally and theoretically as cathode material of Li-ion batteries. The most important material in this category i.e. Li2FeSiO4 was synthesized by three methods including nitrate-based sol-gel, oxalate-based solid state reaction and oxide-based solid state reaction. Based on XRD and SEM evaluations, grain size of synthesized powders was estimated to be between 15 to 100 nanometers. Of these three methods, oxide-based solid state reaction was employed in this study for the first time. This syntheses method is very important due to the significant lower... 

The MP210 superalloy belongs to the category of multi-phase superalloys, designed for specific applications at high temperatures, such as components in gas turbine engines. However, its usage is limited due to hot fracture concerns at temperatures around 800 degrees Celsius. This research delves into the mechanism of hot fracture in this alloy. To explore this, the microstructural changes in samples subjected to hot tensile testing in the temperature range of 500 to 1000 degrees Celsius were studied using microscopic and microanalytical techniques. The yield strength and ultimate tensile strength at 500 degrees Celsius were 475 and 850 megapascals, respectively, decreasing to 105 megapascals... 

Researchers have long considered the phenomenon of parametric amplification. This phenomenon is introduced first in nonlinear structures and then in limited systems of time-varying linear structures. Time-modulated systems have many capabilities, such as amplification, non-reciprocity, and other phenomena in wave propagation. So far, time-varying circuits have been studied in terms of stability and analytical solution. The purpose of this project is to investigate parametric amplification in time-varying linear systems. Studying a structure under a circuit model is essential to other analyses practically implemented in various frequency ranges from microwave to light. As a result, this... 

Hadith, as one of the most important sources of classical Arabic text, presents the sayings and the conduct of Prophet Muhammad (PBUH) and his family (A.S) as narratives of life and religious teachings. In this context, Hadith processing includes tasks such as sorting, extraction, linking, categorization, and alignment of information from hadith texts, which assist in easy access to information and better understanding of the meanings of the hadiths. The absence of a comprehensive database of hadiths presents a challenge, making access to information diffcult and comparison across different works impossible. Preprocessing of hadith texts faces challenges like information extraction (such as... 

All supersonic intakes with external compression, having a good level of performance at all the critical poin t. Exhibit a marked instability of flow in subcritical operation below some value of the flow ratio, in the form of an oscillation of the shock system, colloquially known as “buzz", which can lead to thrust loss, engine surge or even structural damages. Therefore the effort to understand the nature and cause of this phenomenon is important in order that the starting of buzz can be predicted and more effectively avoided without losing performance. This phenomenon has been the subject of many studies, mainly experimental. In this research, we design and build an axisymmetric supersonic... 

Low back pain is one the most prevalent disease and major economic issue facing modern countries. Epidemiological studies suggest that maximum trunk flexion, the angular velocity of trunk and the rate of repetitive movements (such as flexion-extension), are associated with low-back disorders. From biomechanical point of view, lack of stability during dynamic repetitive movements, increases the risk of injuries. On the other hand, some researchers suggest increasing motor variability could be an intrinsic factor to intervene muscuskeletal disorders during repetitive movements. Pace of repetitive occupational tasks could affect both, motor variability and dynamic stability. The goal of this... 

Introducing the basic concepts of solar desalination systems, improving the performance and efficiency of the solar system under vacuum has been investigated. Further, according to the classification of the types of solar desalination systems, the details of their existing designs have been discussed. The solar desalination system under vacuum is classified into two types of solar systems under natural vacuum and under forced vacuum. The solar system under natural vacuum is divided into one-story and multi-story, while the solar system under forced vacuum is classified into two types, single-effect and multi-effect. Previous studies as well as the most important recent developments in this... 

Many efforts have been put into increasing the efficiency of dye-sensitized solar cells that part of it has been devoted to structure and chemical composition of photoanode electrode. In this thesis, the effect of changes in the composition and its influence on light scattering ability in photoanode of dye sensitized solar cells was studied.First, the nanoparticles of titanium dioxide powder through solvothermal method as well as spherical particle and barium titanate powder by sol-gel method were synthesized. XRD and FE-SEM analyses indicated that synthesized powders are in good size and morphology regarding the intended chemical composition. Optical properties of TiO2 particles were... 

Fine-tuning language models has become a prevalent approach to tackling various natural language processing tasks. However, fine-tuning a model sequentially on a series of tasks leads to catastrophic forgetting: as the model learns a new task, it tends to forget the previously learned tasks. This research aims to address this issue by proposing a soft prompt tuning approach, a parameter-efficient fine-tuning method introduced in recent years. We introduce an improved version called SuperPositon Prompts, which is evaluated on the T5 model using tasks from the GLUE and SuperGLUE benchmarks. The results demonstrate the superior performance of the proposed method compared to previous approaches.... 

The purpose of this research is to establish a neutron reference field for the calibration of neutron dosimeters based on the beam of the neutron radiography system in the Isfahan miniature neutron source reactor (MNSR). The aim is to address the several limitations, including the inability to achieve a wide range of dosimetry, high uncertainty due to variations in distance from the source, significant scattering, and non-uniformity. To overcome these issues, a linear, stable, and wide-range dosimetry field based on MNSR have been established, characterized and evaluated by using the variations of the reactor power. In the first step of establishing the calibration field, the linear and...