Sharif Digital Repository

Traffic safety is one of the fundamental part of the transportation planning which is led to lowest the number of crashes and its following consequences by in-depth studying. Thus, determining the severity of accidents, including damage, injury and fatal injury is very important. The aim of this study is analysis of the accident-injury severities in single-vehicle and multi-vehicle crashes and providing the policies in Iran. The approach used in this study to select the most effective parameters of the injury-severity is based on the data gathered in Iran Road Maintenance and Transportation Organization during the year 2011. Accident probabilistic model based on analysis of relations among... 

High swirl combustors with circulative structures in the flow field, have a highly flame stability with a wide range of operating conditions. In this study, Sharif Gas Turbine Model Combustor (SGTMC) which is a double high swirl burner, was investigated experimentally and numerically. In experimental studies, SGTMC with different settings of swirlers is investigated in terms of flame lean blow-out(LBO), wall temperature, the exhaust gas composition and pollutant and also flame geometry parameters. Setting of burner are changed by variations in air fraction between inner and outer air inlets or swirlers’ vanes degrees and flow rotation directions. The results indicate that the concentrations... 

In this study the spouted bed with draft tube was investigated by discrete phase model for particulate phase and was tried to simulate the spouted bed with high precision by using of experimental data. So, the most accuracy combination of different parameters and sub models was specified. According to this study, the dispersed k-ԑ turbulence model and standard wall function make best prediction. Gidaspow drag model was used for prediction interaction between phases. This study include the effect of Saffman lift force and Rubinow-keller model was chosen for coefficient of Magnus lift force. In Addition, the solid movement pattern was studied in different area of bed especially in fountain... 

Domino accidents are those which are initiated from one equipment and extend to neighbor equipments or units and as a result the consequence of the primary accident is increased. Risk management is one of the tools for reducing risk of accidents and Quantitative Risk Analysis is a crucial stage in risk management. Despite the importance and severity of domino accidents, in most of QRA studies the effect of these accidents on risk is not considered. In the present work tools for Quantitative Risk Analysis with considering domino accidents has been developed. Two major methods for this reason are used; analytical method and simulation. First, software based on analytical method was developed... 

The aim of this study is to evaluate post-earthquake travel behavior in Tehran. After a horrible disaster, like earthquake, people’s travel behavior may change substantially in comparison with normal condition. If people’s travel behavior can be predicted after an earthquake, then authorities can manage travels for emergency medical services in a more efficient way, so the casualties are profoundly diminished. To collect a formation, a questionnaire about socio-economic characteristics of people and their post-earthquake travel behavior was designed. According to the obtained results, time of occurrence and severity of the earthquake are of the utmost importance. So if the earthquake occurs... 

With prominent features such as lower power consumption, shock resistance, and smaller size, SSDs are widely being used in portable applications. In addition, SSDs are becoming more popular in data storage systems and servers due to their even access and fast response time. Several efforts have been made in the past few years to improve the performance of SSDs. One common technique to improve performance is designing an Input/Output (IO) scheduler based on SSD organization.
In this thesis, we propose an IO scheduling algorithm to improve both performance and endurance of SSDs. Since in-place update is not allowed in flash chips, erasure before any data overwriting is required. As... 

Crack propagation in materials is an attractive problem in engineering because of the impact on the safety as well as economic issues. Much research studies have been done on the crack initiation, crack propagation criteria and path in the materials with different characteristics and conditions. Crack modeling depending on the material properties in brittle and quasi-brittle materials is done as Linear Elastic Fracture Mechanics (LEFM) and cohesive crack, respectively. The aim of this thesis is the modeling of crack propagation using energy method and comparing it with the cohesive crack. In order to model this problem, it is necessary to solve the governing equilibrium equation of the... 

In recent years, with the rise of data-driven applications, ensuring performance has become a major challenge in the design of storage systems. One of the main reasons for the lack of performance guarantees is the presence of the Flash Translation Layer (FTL) in solid-state drives (SSDs). Recently, Zoned Namespace SSDs (ZNS SSDs) have been commercially introduced. In these drives, FTL tasks such as data placement and garbage collection are delegated to the operating system. Many research efforts on these devices have explored their potential as application-specific storage stacks. However, a review of prior studies shows that none have examined the performance issues caused by the FTL on... 

Modification by crumb rubber is a useful means of improving the resistance of asphalt binders and mixtures against rutting, fatigue cracking, and low temperature cracking. Increase binder viscosity and decrease stability at high temperatures are accompanied by most modifiers, and crumb rubber is no exception. Recent research efforts have shown that development of cross bonds across polymer chains and sulfur can improve the storage stability of modified binders. Also, WMA additives can considerably decrease the binder viscosity. This research showed that addition of small amount of sulfur during the crumb rubber modification can improve the workability and storage stability of this binder.... 

Recently, security of integrated circuits has received more attention as ICs have become more complex and their usage has increased in safety critical systems. Many orgeniaztions use the ICs that made by third party companies. This is due to the high costs to build and maintain state-of-the-art semiconductor factories. This subject puts the trustworthiness of the ICs under the question. The chips might be maliciously modified in each stage of the manufacturing chain. This threat is called hardware backdoor in scientific community. The aim of this project is to assess the features embedded in a microprocessor and evaluate the side channel effect of various hardware backdoors. hardware... 

Recently, there has been a great interest toward site–specific modeling of outdoor radio wave propagation. Wave propagation in very large environments compared to a wavelength builds up an important category of electromagnetic wave propagation problems which occurs in
versatile criteria from optical devices to long wireless microwave links. Well-known methods such as different ray tracing schemes used in these problems suffer from long execution time and great amount of needed memory. A new method has been proposed in this thesis to overcome such difficulties for high frequency wave propagation in large scale problems. The proposed method is based on tracing 3D vectorial Gaussian beam.... 

Despite low time intervals between requests in many real-world workloads, the flash chip utilization remains very low, leaving the storage device mostly idle. This affects the performance of flash chips in Solid-State Drives (SSDs) and directly correlates with the diminished operational efficiency of these storage devices. Recent studies involve statistical analyses and workload behaviour modelling to maintain the operational efficiency of SSDs. However, due to the unavailability and non-disclosure of the internal control unit structure of conventional SSDs, namely Flash Translation Layer (FTL), the underlying assumptions of these methodologies are deviating from practical realities.... 

The impact of droplets is a widely used method for creating direct heat transfer between two fluids. This method enhances heat transfer between the working fluid and the phase change material (PCM). Therefore, a thorough investigation has been carried out on the impact of an acetone droplet on the surface of a pool of molten paraffin, which leads to the simultaneous boiling of the acetone droplet and solidifying part of the paraffin in contact with the acetone. The dynamics of impact, the depth and width of the crater, the jet, and the crown formed as a result of the impact have been reported with varying Weber numbers (ranging from 74 to 375), and the temperature of the pool surface of the... 

The main EOR method after heat recovery is gas injection. Minimum miscibility pressure is one of the parameters that affect gas injection. This project includes computational and laboratory sections to estimate the MMP. The MMP were estimated during the injection of CO2, Ga, Gb and methane gases into two oil samples. In the computational part of the project, MMP is estimated through cell to cell simulation and using Peng_Robinson equation of state. Also, the MMP is measured by using slim tube apparatus which is used so widely in the industry. According to the results, CO2 has the lowest miscibility pressure among other gases. It was miscible into oil even at pressures near the bubble...