Sharif Digital Repository

The last-mile delivery is one of the most challenging problems in supply chain management. In recent years, many studies addressed last-mile delivery and investigated vehicle synchronization to serve customers. The speed and flexibility of drones and the transportation capacity of trucks attracted the attention of researchers to investigate the synchronizing problem of these vehicles. However, most previous works assumed fixed locations for customers, which may not be accurate in real-world environments. The goal of this research is to addresses a more realistic problem, in which customer movements and mobile locations are considered for the first time. A mixed-integer mathematical... 

The rapid advancement of information technology and computer networks raised concerns of the users and network administrators regarding security. The development of computer networks and the increase in the number of specialists in this field led to the increase in the number of people who seek to abuse these networks, people known as attackers. The attackers look for security defects in a network to penetrate and abuse it proportionate to their needs. Considering the risks of these attacks, it is necessary to have an intrusion detection system (IDS). IDSs are capable of detecting attack traffic or suspected traffic, then, they alert the network administrators, and consequently, stop the... 

Coral reefs are one of the most important ecosystems in terms of animal diversity and affect the life of organisms in different ways. This ecosystem is under many stresses today. Among the most important events that threaten corals is the event of coral bleaching, the most important cause of which is the increase in Sea Surface Temperature (SST). Therefore, it is highly important to monitor changes in SST affecting corals. Generally, temperature anomalies are investigated using the Degree Heating Weeks index (DHW) and SST data. DHW index is variable in different coral areas and changes with time. Consequently, in the present study, this index has been investigated due to the lack of... 

In this text to find the answer of the question “ what is it to be physical” in a definition form or a scheme of the term physical, firstly we sought for a possible consensus among recent physicists and philosophers. But from their answers not only we did not find any clear consensus but also most of them confess that the term is ambiguous and unclear. In a general aspect, we can categorize the answers to two theoretical and realistic perspective. The theoretical perspective, beside circularity and Hempel’s triviality, seems not to present any criteria for being physical. In realistic perspective, it seems that there is no ontologic constraint for being physical, that is from “being... 

The application of membranes for separate of particles in mainly microbial flacs , are fast growing in biological treatment systems. Membrane bioreactors are now considered as one of the major new processes in wastewater treatment. However , membranes are expensive and costly. This study is carried out to test an innovative , locally made filters for separation of flocs in an MBBR reactor. This innovative filter is replacing a traditional settling tank. This type of filters is made very cheaply and has important advantages in installing and operation. Experiments were carried out in a laboratory scale MBBR unit. A filter unit consisting of 3 innovative filter tubes were placed and the... 

This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems and issues arising in its applications. The new electric utility environment has an immedi-ate consequence of emphasis on reliability and secure operation of power systems. This requires faster and more precise methods to assess the dynamic aspect of se-curity. On the other hand, this issue is becoming challenging when the determined dispatch might not be accommodated due to violation of the limits.This thesis addresses the problem of dynamic security assessment in power sys-tems with an emphasis on its application in restructured power systems... 

Are the returns of the mineral companies in Tehran Stock Exchange affected by the changes in the commodity price at the Iran Mercantile Exchange? By implementing a Multi-Factor Model we will calculate the firms’ value elasticity to the commodity price changes. We try to explain the estimated elasticities on the basis of the firm’s fundamental variables using a discounted cash flow valuation model. An unbalanced panel data estimation is employed for this purpose. Afterwards, we will suggest a novel model on the ground of the assumption that the commodity prices and firm values follow the Geometric Brownian Motion. The result of the model is that the elasticity can be explained by commodity... 

Rotor contact with a stationary element of a rotating machine and the subsequent rubbing at the contact area is a serious malfunction that may lead to the machine’s catastrophic failure. In the past decades, many studies have been done on the rubbing phenomena, its different regimes and its various consequences on the machine performance and safety. However, most of them have used a simple model to investigate the rubbing interaction between the rotor and the stator. This simple model consists of the Jeffcott rotor, as a model for the real rotors, and a rigid annular block surrounding the rotor, as a model for the real stators. The objective of this thesis is to build an algorithm to... 

Complex networks serve as generic models for many social, technological and biological systems that have been shown to share a number of common structural properties such as power-law degree distribution and small-worldness. These networks determine interactions and influence the spread of diseases, behaviours and ideas. Epidemics and failures like new behaviours ideas and innovations can spread throughout a network and prevent it from doing its functionalities. In this work, we investigate error and attack tolerance of epidemic spreading in complex networks. The main content of this thesis is arranged in three sections as follows: Firstly, the effect of random and systematic failures is... 

Value at risk of an asset, is the asset’s expected maximum loss for a certain period of time and at a specified confidence level. Value-at-Risk can be calculated in the bank with its inter-nal method or standardized method. when a method have more violation number then bank need to keep more daily capital requirements. under the Basel 2 agreement if the violation of method more than 10 times in year, the Bank uses the standardized method.
There are trade off Between daily capital charge and violations. Therefore, existing methods for calculating the value at risk, usually lead to much daily capital charge or many violations. Studies show with combination of different methods to calculate...