Sharif Digital Repository

Operating rooms has always been considered as one of the most expensive, yet most profitable part of a hospital. Since many units in the hospitals are related to the operating room, improving efficiency in the operating room will result in increased efficiency in other units, so offering proper solutions in this area is very important. Suitable Planning and scheduling has a great impact on increasing the level of service and efficiency of the hospital. in this thesis, a mixed integer programming model for scheduling weekly elective patients in the surgical theater with the objective of maximizing the number of elective patients for the surgery and also the workload of the operating room... 

The objective of this project is to design and control and optimize a single-stage three-phase three-switch unity power factor telecom rectifier. For this purpose, the topology of three-phase three-switch converter has been investigated for both isolated and un-isolated converters. Following a comprehensive investigation on the converter structure, the power dissipation factors have been detected and the quantity of the power dissipation has been calculated by analytical methods and it confirmed by simulation results. To avoid extra power losses some novel soft-switched structures for three-phase three-switched converters have been introduced. the proper operation of the soft-switched... 

A quasi-Z-source inverter is a beneficial structure in photovoltaic applications. In a transformerless grid-connected inverter system, the common-mode voltage fluctuations cause the leakage current flow through the ground. The low-frequency harmonics of the common-mode voltage results in the malfunction of the residual current device. On the other hand, the high-frequency harmonics of the common-mode voltage cause EMI problems, additional loss and disturbance in the output currents. In this thesis, some methods are presented to reduce the leakage current in a three-phase quasi-Z-source inverter. First, different shoot-through implementation methods are investigated. By modifying the number... 

Existing Intrusion Detection Systems (IDSs) are not designed to deal with all categories of processing environments. This thesis focuses on IDSs for the Grid computing environment, and concentrates on feature selection and performance. An existing framework, Globus, is used as the basis for the consideration and development of the research issue in Grid computing. The system is based on two engine designs: (a) Signature and (b) Support Vector Machine; SVM has been selected for pattern discovery in traffic analysis. We found that the performance of the system greatly depends on the efficiency of the underlying framework and the number of Intrusion Detection System instances. We demonstrate... 

When organizations prefer to outsource their data, security protection of data will be more important. Using cryptography in addition to access control techniques is a natural way for saving confidentiality of data against untrusted server. However, encryption and decryption of data result in database performance degradation. In such a situation all the information stored in encrypted form, one cannot make the selection on the database content any more. Data should be decrypted first, so an unwilling tradeoff between the security and performance is normally forced. The appropriate approaches to increase the performance are methods to deal directly with the encrypted data without firstly... 

Data outsourcing is considered as a promising approach in today computing and connected world. This approach enables organizations to outsource their data to anexternal third party server which is responsible for storing and propagation of outsourced data. Although data outsourcing offers many benefits, especially for those organizations with limited resources and increaseing data volume, but this approach in security aspects like providing confidentiality and privacy about curious external third party or other threats, is faced by serious challenges. In the recent decade many approaches for solving or at least decreasing the potential threats over providing confidentiality of outsourced... 

Electronic voting refers to voting methods that is done using electronic devices or via the Internet or Web. Helios and Civitas protocols are among the recent protocols introduced in this field. Importance and high sensitivity of electronic voting protocols has led researchers to pay high attention about their security analysis. In recent years, different approaches have been used to inspect and analyze electronic voting protocols. In many of such approaches, analysis had been done in a very abstract environment and without considering the operational requirements.The purpose of this thesis is to evaluate the security features of electronic voting protocols, considering their operational and... 

Today many communications take place over asynchronous insecure networks which do not provide any guarantee of security (as Internet); hence there is a must in authenticating party or parties with which we are going to interact. In many cases, more than two parties (entities) are going to interact, resulting in need of group authentication. Since authentication is inseparable from key exchange, we are going to introduce a new authenticated group key exchange protocol in this thesis which benefits from all known features for such a protocol in the literature such as contributiveness and deniability. To overcome the problem of concurrency, we use a framework dedicated to security in concurrent... 

End-to-end electronic voting protocols for electronic voting systems are used to hold a secure election with the two features of anonymity and verifiability. Verifiable mixnets are a fundamental element of electronic voting systems, which can keep the voters anonymous by mixing their votes, and provide a verifiability mechanism to prove their performance correctness. As the design of electronic voting protocols is error-prone, researchers consider the use of mathematics-based and systematic methods for their analysis. Therefore, based on formal methods and the process algebra approach, several studies have been conducted to analyze these systems, but none have properly analyzed verifiable...