Sharif Digital Repository

Despite eye-catching progressive trends in highway safety, there have been a great number of unpleasant incidents in highways. A number of 8841 people died in road accidents in the first 6 month this year with 1.7% increase compared to the accidents occurred in 1396 [59]. Operation of a modeling process shall provide the engineers with more opportunities to identify the affecting factors in roads incidents. Safety infrastructure management is mainly aimed at ensuring the efficient measurement, systematic recognition and consequently deterioration of road accidents when they have been designed, constructed and used [37]. Building information modeling (BIM) tends to be a developed managerial... 

Since robustness of peer-to-peer networks depends heavily on voluntary resource sharing among individual peers, the intrinsic problem of free riding exists among autonomous rational peers that consume resources of others without contributing anything in return. One solution to the free riding problem in peer to peer networks is to have incentive mechanisms that aim to improve network efficiency by encouraging peers to cooperate. In this project, we have proposed a hybrid double-auction-based incentive mechanism for centralized peer-to-peer file sharing systems. In addition, a cryptography-based trust management scheme has been proposed to prevent peers from sending fake data. We have... 

Liquefaction is one of the probable consequences of earthquake in soil layers of saturated loose sands. Various aspects of liquefaction have been investigated using different methods of field, laboratory, and numerical studies. Numerical simulation of liquefaction constitutes a major part of these researches. A proper constitutive law must be implemented in the numerical analysis for modeling the complicated behavior of saturated sands during dynamic loading. Simplicity of formulation, limited number of parameters and good performance are the main features of a proper constitutive law. In this study, Endochronic model for simulating liquefaction has been introduced. This model is implemented... 

Sign Language Recognition using cameras is an alternative way of human communication with personal computers. These systems don’t need to use keyboard. They are used when touching keyboard is not possible or for what ever reason, when we don’t want to use keyboard. In this problem the person shows one of the alphabets with his hand and we capture and process that in real-time to recognize the letter. The problem of previous works in this area are the decreasing rate of detection in condition where the angle of sign and viewer changes. The purpose of our work is getting better result by using depth image from Kinect. We use Pugeault and Bowden dataset (that has fingerspelling sign in multiple... 

In this study, a fully coupled three-dimensional numerical analysis of two-phase fluid flow and heat transfer through deformable porous media is presented in the context of extended element free Galerkin method. By coupling momentum balance equation for the whole mixture, continuity equations of wetting and non-wetting fluid phases and energy balance equation, the developed numerical algorithm is capable of simulating a wide range of engineering problems such as CO2 sequestration, nuclear waste disposal in deep underground strata, hydraulic fracturing in oil and gas reservoirs and so on.By taking the advantages of partition of unity property of MLS shape functions, weak and strong... 

The popularity of Internet-based video services has increased in recent years, while in 2017 reached nearly 70% of the total Internet traffic. Changes in network status and the problems that result in the user experience leading to poor quality of the video watching experience, online video players have been using adaptive algorithms to match the quality of the received stream to the current state of the network. Different algorithms have been proposed for optimization of matching operations, but due to the different and sometimes contradictory nature of the constituents of the quality of user experience, the priority and focus of each of these algorithms is based on different challenges... 

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...