Sharif Digital Repository

In this study, mechanical properties of neat isotactic polypropylene (iPP) were evaluated on local and global scales. Depth-sensing indentation with nanoscale resolution (nanoindentation) and traditional macromechanical tests were incorporated for this purpose at different temperatures and strain rates. Various morphologies and crystalline structures of iPP was obtained via changing processing conditions in melt state. A certain relation was found between the local and global mechanical properties, i. e. yield stress, modulus of elasticity and hardness. Moreover, developed yield models were evaluated on the local scale. The results showed that while crystal plasticity theory is not valid for... 

Nanotechnology inrecent yearshas attractedthe attention of manyscientists and industrialists. Having atiny structure with extraordinary properties of nanoparticlesin the fields of electrical, mechanical and thermal, leading to their use isgrowing and newer application sarebeing found forth eseparticles. One of them Nanodiamond powderiswidely usedin the industryhas found wideapplication. Among these can be used in electrochemistry, chemical coatings, pastesand suspensions, add thepolymer, ceramic and industrial rubber and adhesives,adsorbentsand catalysts, filters and membranes, and finally cancer treat mentnoted. One of these applicationsisinPolymers and Rubber Industry. According to earlier... 

In this study solid lubricants MoS2 nanoparticles with average size 50 nm and hard ZrO2 nanoparticles with average size 51 nm were used in watts bath and Ni/ZrO2-MoS2 composite coatings were prepared by pulse plating technique. Effect of current density, frequency, duty cycle, surfactant type and concentration of particles in the electrolyte on the amount of particles in the coatings were investigated and optimum conditions were determined to create composite coatings. Scanning Electron Microscopy (SEM) and x-ray diffraction (XRD) analysis were performed to study the morphology, structure, chemical composition of coatings. Corrosion testing of coatings by potentiodynamic polarization in... 

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... 

This thesis is related to applying survey of scientific inventory control methods in Khoramshahr Oil Extraction Company (KHOEC). KHOEC is the producer of edible oils in I.R of Iran and is a subset of E.T.K.A holding organization. The inventory costs of high consuming items are studied and optimized based on the optimal ordering policy (r, Q). First, the company raw materials are identified and classified based on ABC analysis method. For developing the new method of inventory control, the demand for each item is predicted, and the probability distribution of demand during the lead time is determined. Then according to this information and the desired service level of management, order point... 

One of the security issues in database outsourcing scenario is the correctness of the query results. Correctness verification includes integrity, completeness and freshness of the results. Most of the proposed approaches for correctness verification impose high overhead on the components of the scenario which prevents the scenario to implemented in practical applications. In this thesis, we have proposed a probabilistic approach which imposes acceptable overhead for correctness verification of returned results of service provider. The approach uses the previous behavior of the service provider to calculate a trust value toward it which is used to adjust the imposed overhead. In other words,... 

Inventory control has been always considered important due to its prominent role in managing and better application of resources in the field of operational systems. Ordering system or review stock policy in supply chain management can be mentioned as one of the inventory control study fields of management. A lot of researches have been done in investigating ordering system in supply chain under certainty conditions; however, since the real world is full of uncertainties, parameters such as demand cannot be predicted exactly and we encounter with ambiguity. In this case, using crisp (exact) values can cause to decide wrongly (a wrong decision). On the other hand, due to absence of sufficient... 

In this paper, we consider a three-echelon supply chain consisting of a producer, a distributor and a retailer. Generally each echelon tends to minimize his own inventory costs. On the other hand, competitive environment of business market, force companies to develop strategic alliances. In order to boost their partnership, separated echelons must integrate their policies, so that the total cost of the system be minimized. The model, extends the research of Wang et al.(2011) by changing the No shortage assumption into backlog shortage model.
This study assumes different deterioration rates among different echelons, and deterioration rates are time-sensitive, which is very helpful in...