Sharif Digital Repository

The 1991 NIOSH Lifting Equation (NLE) is widely used to assess the risk of injury to the spine by providing estimates of the recommended weight limit (RWL) in hands. The present study uses the AnyBody modeling software to verify whether the RWL generates L5-S1 within the limits (e.g., 3400 N for compression recommended by NIOSH and 1000 N for shear recommended in the literature). Twenty-four symmetric and asymmetric lifting activities were simulated to evaluate the RWL by the NLE and the L5-S1 loads by AnyBody. In two activities, involving large trunk flexion and 30 and 60 degrees of load asymmetry, the estimated RWL generated L5-S1 spine loads exceeding the recommended limits. The NIOSH... 

Delay is an important factor in modeling and describing many chemical processes, mechanical systems, teleoperation and networked control systems. On the other hand, model predictive control is a very useful and powerful tool for handling different types of systems including time delayed systems. The main disadvantage of model predictive control is massive computational load and which may lead to wasting system resources. One of the best options for dealing with this issue is to employ event-triggered strategy in model predictive control. Using this approach can relax computational efforts and save system resources. This thesis is focused on introducing a robust model predictive control using... 

Fatigue crack growth can have harmful effects on the reliability rotary machine. While an early warning to crack, can be used to extend the life of these expensive machines and increase reliability.Structural Vibration Condition Monitoring as a primary fault detection method, achieved to a lot amazing result and for this reason studies vibration behavior of cracked rotational shaft is a big issue for engineers of dynamic machine.In this research, first check the fault detection methods based on structural vibration condition monitoring, mode shape methods were extracted. Then by modeling rotational shaft in computer and creation of crack on it, fault detection quality of these methods have... 

Cooperative coexistence of two kinds of users with different priorities in random access wireless networks has been studied in this thesis. Source burstiness, a phenomenon in data communication networks, allows using silence periods of primary users (PUs) to have a better spectrum utilization. In this respect, new users, known as secondary users (SUs), are considered to exploit the resources opportunistically. In usual spectrum sharing systems, SUs have to act in a way to be transparent for the PUs. Therefore, they are allowed to access the common spectrum band only when PUs are silent. However, seeking such opportunities needs sensing capability of secondary nodes.In this thesis, sensing... 

Predicting the trend of stock prices is always one of the concerns that stock market analysts and investors face with, which plays a critical role in maximizing the profit from investing in stocks. Past stock price charts, raw material prices, the value of the company's assets, the impact of global markets, the company's products, the organization's development plans, and the same other factors influencing the stock price. News reports are an important source of information for people. Recently, a lot of research has been done to examine the impact of news on stock price trends. This research has two research phases. In the first phase, a text mining method is presented which is using... 

Graph partitioning, or graph clustering, is an essential researa problem in many areas. In this thesis, we focus on the partitioning problem of unweighted undirected graph, that is, graphs for which the weight of all edges is 1. We will investigate spectral methods for solving the graph partitioning and we compare them. In addition to theoretical analysis,We also implement some of spectral algorithms in matlab and apply them on standard graph data sets. Finally, the experimental
results obtained are offering  

A random vector with binary components that are independent of each other is referred to as a Bernoulli random vector. A Bernoulli Mixture Model (BMM) is a combination of a finite number of Bernoulli models, where each sample is generated randomly according to one of these models. The important challenge is to estimate the parameters of a Bernoulli Mixture Model or to cluster samples based on their source models. This problem has applications in bioinformatics, image recognition, text classification, social networks, and more. For example, in bioinformatics, it pertains to clustering ethnic groups based on genetic data. Many studies have introduced algorithms for solving this problem without... 

Network coding, as a promising method for data exchange in wireless communication network, is investigated by many researchers. However, the random nature of packet generation and transmission as well as the collision among transmitted packets have not been fully addressed in network codingrelated literature. In this dissertation, we analyze the network coding-based wireless network from this point of view. In order to achieve this goal, we apply mathematical tools such as probability theory and queuing theory. In the first part of this dissertation, we address the interaction between MAC and network coding. In this respect, we consider a multihop tandem wireless network, where each node is... 

In this dissertation we discuss various results presented in the literature on single user channels with causal or noncausal side information and multiuser channels with side information such as multiple access channel and broadcast channel. The Series Relay Networks (SRN) with delays, with and without channel state information (CSI) are investigated from an information theoretic point of view. For SRN with unlimited look ahead where the relays can use the whole received block to encode, upper and lower bounds on the capacity are derived which are tight for the degraded case. For SRN without-delay where the relays have access to the present received symbols in addition to the past symbols,... 

Nowadays, with a constant increase in life expectancy, joints pain and deficiencies have become a major problem and the use of prosthesis is increasing. One of the most important joint in human body is the hip joint which bear a major share of forces in daily activities. Hip joint is a cup-sphere joint with 3 degrees of freedom (DOF). Therefore, design and manufacturing of such prosthesis is very important. The objective of this thesis is to develop the know how for manufacturing of a standard hip prosthesis by hot forging of Ti6Al4V alloy. First a review of kinematics of bones and joints and forces on hip joint is presented, then the proper process for manufacturing of the hip prosthesis... 

Time-dependent origin-destination demand is a key input in dynamic traffic assignment in advanced traffic management systems, and the result of dynamic traffic assignment is dependent on the accuracy of this information. One method to achieve time dependent demand matrices is using a primary demand matrix and volume traffic counts in some links of network. In this thesis a bi-level model is used to correct the demand matrix and the extended gradient method is suggested to solve the problem. The extended gradient is an iterative method that in each iteration, corrects the demand matrix in a way that the estimated traffic flow be close to the observed traffic flow. Execution of this method in... 

Pricing problem in transportation networks focuses on determining tolls that cause travellers, motivated only by their travel costs, to choose routes that would collectively benefit all travellers and results in optimal utilization of transport network resources.This thesis addresses the toll pricing problem in which the objective is to minimize the number of required toll facilities in a transportation network. Minimum tollbooth problem (MINTB) has binary variables and is very difficult to solve. In this thesis a new heuristic approach has been presented for solving MINTB problem. The results show that, this approach is much faster than the existing algorithms and is able to solve real size... 

Groundwater is the primary source of freshwater in many coastal areas and small islands around the world. The most important hazard to groundwater quality in coastal aquifers is seawater intrusion (SWI) resulting from over pumping, prolonged drought conditions and sea level rise due to climate change impacts. Numerical models of SWI are an important tool in the management of coastal aquifers. However, numerical modeling of SWI is one of the most challenging problems in groundwater hydrology. One of the reasons for the challenging nature of SWI numerical modeling is the relatively large level of uncertainty associated with the estimation of the model input parameters. This study focused on... 

Sensitive ecosystem and scarcity of freshwater are the main characteristics of small islands. These islands have small catchments and usually lack tangible surface water resources. As a result these islands are dependent almost entirely on groundwater. Groundwater on small islands usually occurs in the form of a freshwater lens floating on the more dense saline water. The freshwater lens is highly sensitive to various stresses such as drought, pumping, sea tide, etc. Due to the importance of freshwater lens in islands, proper and optimal use of this vital resource should be studied. Kish island`s freshwater lens was three dimensionally simulated using the numerical model SUTRA. The aim was... 

Due to the importance of hazardous materials (hazmat) transportation, this problem should be programmed and solved appropriately. Hazardous materials are substances that may endanger the health of humans, animals and the environment. One of the most important parameters in hazmat transportation problem is risk, since other routing researches don’t involve risk as an influencing parameter. In the scientific literature of the transport of hazardous materials, the risk is defined by the calculation of the probability and severity of damage to the endangered recipient through unwanted warnings from hazardous substances. In the model of this research, the accident rate is considered as the... 

In recent years, neural networks have been widely used in most machine learning domains. However, it has been shown that these networks are vulnerable to adversarial examples. adversarial examples are small and imperceptible perturbations applied to the input which lead to producing wrong output and thus, fooling the network. This will become an important issue in security related applications of deep neural networks, such as self-driving cars and medical diagnostics. Since, in the wort-case scenario, even human lives could be threatened. Although, many works have focused on crafting adversarial examples for image data, only a few studies have been done on textual data due to the existing... 

In the present thesis, the SPASER is investigated, from theory to structure design. SPASER is a counterpart of laser in 3D subwavelength dimentions. In other words, SPASER does not suffer from the diffraction limit of photons which is a drawback in laser technology. It potentially can generate intense coherent dark and bright surface plasmon modes. The small size of SPASER gives it the capability of being integrated with electronic chips. So, the electronic technology will become faster if the SPASER is realized. In this thesis, we intend to use the unique plasmonic properties of graphene in our designs. Plasmons on graphene platforms have longer propagation length and larger lifetime in...