Sharif Digital Repository

Today, Quantitative Risk Assessment (QRA) has become an efficient tool in decision making for safety and process experts. To assess the risk of any accident scenario, it is necessary that the probability of that event be determined in addition to estimating the probable consequences. Event tree and fault tree analysis are known to be the standard tools for calculating the frequency of incident outcomes.
In this research, a new method based on Markov chin and Fuzzy theory is presented to estimate the occurrence probability of events. A one of important parameter which has sufficient effect on probability of incident frequency, is inspection and maintenance interval. in this research... 

In high-voltage power electronics systems where the supply voltage exceeds the maximum voltage these devices can withstand, series-connected IGBTs with TO-247 packaging and simultaneous gate command circuitry are used to create a high-voltage switch with an on and off time equivalent to a single IGBT. By considering voltage protection circuits for the series IGBTs, the large supply voltage is approximately evenly divided among the series switches. The resulting high-voltage switch has smaller conduction and switching losses compared to single high-voltage switches, has a lower finished price, and its turn-on time is much shorter due to their smaller gate-emitter junction capacitance... 

Solar panels are still rather expensive equipments. At current electricity prices, it takes several years to return the investment made to install them in a household. Smarter use of their produced energy can help reduce this break-even time, and hence, would motivate more households to be willing to install and use them which would finally result in a more sustainable society with less reliance on fossil fuels. Electricity prices usually differ at different times of day with the common, but unfortunate, property that the price is maximized at evenings when the solar energy production is minimal or non-existent while at the peak production of the solar panels, i.e., around noon, the price is... 

Polymer flooding can yield considerable increase in percentage recovery. However, there are limitations with the existing polymer flooding technology, such as thermal, mechanical, bacterial degradation, surface absorption and undesirable plugging. A novel nanocore shell structure of polyacrylamide and polystyrene designed and prepared to intellectually control mobility ratio in oil reservoirs and overcome weakness and limitations of classical polymer flooding. Polyacrylamide particles have been obtained using spray drying of dilute solution of polyacrylamide. Then, polystyrene shell has been produced on polyacryamide particles by in-situ polymerization of styrene monomer in hydrophobic... 

In recent years, requirement engineering and goal modeling have gained more attention among different organisations. Therefore, different methods have been designed to discover stakeholders’ requirements and translate them into process and organizational goals. Various goal models have been introduced to represent these goals and their relations towards each other. Still, these methods are manual representations of different process scenarios and do not relate to the actual behavior. In 2014, Map Miner Method (MMM) was introduced to discover intentional process models from event logs. MMM uses Hidden Markov Model (HMM) as a means to represent the process as a map model of strategies and... 

Recommending routes to city taxis in order to improve their performance in finding passengers can reduce traffic, pollution and waiting time for passengers, as well as this, increasing the efficiency of taxis can increase their income. In this study, by analyzing trajectory data obtained from 536 taxis in San Francisco over a period of one month, we generated networks of cells, each of which has time-dependent characteristics such as the probability of finding a passenger, the capacity of each cell, or the amount of demand exists is in the cell and the average speed of passing through that cell. also, the connections between these cells in order to make more use of the experiences of taxi... 

The purpose of the present study is to develop neural network estimation method for hybrid or panel data which have a combination of two cross-sectional and time series structures and because of the features of both structures, their use in different sciences offers many advantages; and the analytical methods for this data structure are also different from other one-dimensional structures, so different and specific regression models are presented for this data structure. However, in the artificial neural network method, modeling the development for this data structure is neglected, so in the present study, using the concepts of panel regression methods and their application to the... 

One of the utmost important factors during salvage operation of drowned ships is raising velocity. Uncontrolled raise is a dynamic phenomenon which can lead to the sudden tensions, collapse in airbags or ships. Studing this issue helps the engineers which kinds of problems are more important during salvage operations. This study focus on modeling and analysis of raising movment of the ship with FLOW-3D and ABAQUS software.
In FLOW-3D environment, hydrodynamic analysis of rising movment of drowned ship has been done. We should mention that applied forces and velocities and other parameters from the FLOW-3D output should be passed IMCA Criteria to avoid uncontrollable raise. In ABAQUS... 

Profile Monitoring is a new research topics in the field of statistical process control. In many applications of statistical quality control, sometimes quality of a process or product described by a relationship between a response variable and one or more independent variables.The researchers call this relationship profile. The study seeks to demonstrate that monitoring profiles In addition, the industry can be effective in medical field and improves control of the patient's condition by a doctor. Profiles are usually modeled with a linear regression equation, non-linear or polynomial. finally, the results of this study, using actual data, models and methods to predict and control... 

Two experimental models were designed and tested to extract energy from vortex induced vibrations of a elastically mounted one degree of freedom rigid cylinder in the Reynolds range of 120000 < Re <220000. In the first model the amplitude and frequency of the movement was measured then a second model was designed to be tested in the Emam Hossein marine laboratory. The model was designed in a way that many of its properties like mass ratio, spring constant and damping coefficient were able to be altered. In this study the vortex induced vibration of an elastically mounted cylinder was scrutinized in high Reynolds and very low mass ratios for the first time and an amplitude ratio of 2.49 were... 

As a method of cancer treatment or improvement of cancer-related complications, external radiation therapy is prescribed by physicians, in case of detection of a tumor in a region of patient’s body. Over time, various techniques have been developed for external beam radiation therapy. Among which, Intensity Modulated Radiation Therapy (IMRT), due to its ability to adjust the intensity of radiation beams, has a higher capacity to generate appropriate dose distribution based on tumor size and volume and it is one of the most widely used techniques in cancer treatment centers.The core process in treatment planning is using appropriate computer algorithms which results in posing enough damage to... 

The aim of Emergency Medical Services (EMS) is to provide fast medical care and to transport patients to hospitals at the earliest possible time, so as to reduce injury and fatality rate. Healthcare managers try to improve healthcare systems by reducing the response time to demands. In this thesis, we present mathematical models for the problem of location and relocation of emergency vehicles after the end of their service time or after they have returned to a hospital. We believe that implementing these models can help managers improve the performance of emergency medical services. In the first part of this study, we present a two-level deterministic optimization model considering demand...