Sharif Digital Repository

Polychlorobiphenyl compounds are a class of persistent organic pollutants consisting of two biphenyl rings and chlorine substations. Polychlorobiphenyls do not dissolve in water, are very stable at high temperatures, and are considered a good conductor. Due to the mentioned properties in the 1930s and 1940s, these compounds were widely used in various industries such as power plants, Painting industry, Plastics industry, etc. After years of use, these substances have been found to be very dangerous to the health of living organisms and the environment due to their high resistance to decomposition and the ability to accumulate in adipose tissue. Today, although the production and use of these... 

Quantum mechanics provides a deep understanding of atoms and their interaction with light. As long as we consider only microscopic systems on the scale of an atomic radius, objections to quantum properties such as quantum superposition are nevertheless rare, mainly because of the overwhelming experimental evidence. When it comes to macroscopic systems, many things are not clear anymore. For example,everyday objects of macroscopic size do not exist in superposition of their different states. The reason is that a quantum system interacts with its environment locally,which destroys non-local quantum correlation within the system, larger objects interact with the environment more intensively and... 

One of most important type of dams are concrete gravity dams, This structures maintain their stability against the load from their weight. The study of stability of dams is very important issue because Iran is placed on a seismic zone and instability of constructed dams will cause many problems for us. There are two method in study of concrete gravity dams: in first method which is named rigid approach the body of dam consider as a rigid body and by equilibrium equations and traditional strength of material concepts the safety factors of stability and stresses are determined. In second method that is named flexible approach, we should prepare a finite element method from the dam, reservoir... 

Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the... 

In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon... 

Understanding of the Molecules is the main purpose of the chemistry. Ab-initio molecular dynamics (AIMD) as a branch of the computational chemistry, tries to give us a deep comprehension of the molecule, and its chemical, physical and optical activities. This comprehension, relies on the accuracy of quantum mechanics, in addition to the speed of the classical mechanics. The mixing of the quantum mechanics and the classical mechanics could simulate activities of the atoms in the time-domain, provided the mixing is done with precaution. This, in turn, helps us to forecast the response of a molecule in different situations, and also translating the macroscopic phenomena in a nanoscopic... 

To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have... 

In this research, the problem of locating fire stations and allocating equipment has been studied and a simulation-optimization approach has been presented to solve the problem. The mathematical models of this research were developed based on the idea of the randomness of the covered demand and the maximum expected coverage model. In these models, the issue of non-availability of equipment to cover accidents, the random nature of accidents, various fire incidents and the equipment needed to cover them are considered. Two mathematical models with deterministic and non-deterministic approach with different scenarios for demand are proposed. The non-deterministic model is developed with the aim... 

One of the main concerns of industrial companies’ managers is providing an efficient logistics system. To achieve an efficient logistics system, the fleet planning problem is studied by many researchers in recent years. This problem consists of multiple sub-problems at three levels: operational, tactical, and strategic. These sub-problems are closely related to each other and need to be studied and addressed in an integrated manner. In this research, an attempt is made to provide an integrated framework to solve the vehicle routing problem (operational), outsourcing problem (tactical), and fleet composition problem (strategic). These problems have various uncertainties, including customer... 

Wireless Sensor Networks (WSNs) are rapidly emerging as an important area in mobile computing research. Applications of WSNs are numerous and growing, some of them are even highly critical, like military or safety applications. Security measures must be applied to protect the network from a variety of attacks. Since no intrusion prevention measure is perfect, intrusion detection becomes an important second wall to protect the network. WSNs have unique nature which is different from other kinds of networks. In this project, we examine the characteristics and vulnerabilities of WSNs and propose a new intrusion detection model to protect the network security. In this work we have not only... 

Nowadays Human Resource Management (HRM) has a critical and fundamental importance in organization management. In the beginning and middle of 20th century and even in the last decades of that century financial investments were important in different economic sectors and industries, but in the beginning of 21th century human resource and training is one of the most fundamental issues in all of economic sectors and industries, especially in power industry. Following this point of view, people with appropriate education and qualifications should be employed in power industry. These employees should be skillfully able of working with complicated technology of power industry as well as being... 

Methodology engineering is a branch of software engineering which deals with the design, development, and modification of methodologies, and the techniques and tools for developing information systems. Methodology engineering requirements demand the support of Computer Aided Methodology Engineering (CAME) tools. Recently, method engineering focus has shifted towards Situational Method Engineering (SME); i.e. context-specific methodology development. The emergence of SME approaches has brought about various methods for methodology development; including ad hoc, paradigm-based, extension-based and assembly-based approaches. In the assembly-based strategy, appropriate method chunks are... 

Nowadays, development of renewable electricity generation technologies, the advent of small efficient generators and increasing number of grid-connected consumers, have caused increasing interest in energy production next to the consumers locations. Distributed generation (DG) is often defined as small-scale generators that produce several kilowatts to tens of megawatts of electricity. One primary reason for using DG is its potential to reduce power losses in transmission and distribution networks. Several loss reduction methods such as capacitor placement, network reconfiguration and load management are used in distribution systems. Employing DG results in the highest loss reduction and...