Sharif Digital Repository

Tensors or multi-way arrays are useful tools to identify unknown quantities thanks to the uniqueness of their decomposition. Tensor decompositions have been widely applied to obtain unknown components with physical meanings in many applications such as medical image and signal processing, hyperspectral images analysis, chemometrics, etc.In this thesis, we investigate the application of tensor decomposition for probability estimations, which are required for some targeted data/text mining tasks such as unsupervised clustering of data/documents. Besides criticizing the existing tensor decomposition algorithms for probability estimations, we propose to apply some proper constrained tensor... 

Performance-based design (PBD) has been accepted as one of the most reliable design methods in the past few decades. PBD can overcome inherent deficiencies associated with force-based design (FBD) and has advantages over this traditional method. Various PBD methods have been developed, which Displacement-based design (DBD) has been considered as one of the effective design approaches of the PBD method. In this study, the Displacement coefficient method (DCM) is developed for stub-type integral abutment bridges (IABs). For this purpose, two coefficients are proposed to determine the target displacement of these types of bridges. Validation of this method by nonlinear time-history analysis... 

The use of raed cache of hard disk or solid state drives has a magnificent effect on their performance, power consumption, and their endurance. However, one of the main problems of their read cache is its low hit ratio. Thus, the read cache must be used more efficiently. Based on previous studies, nearly all of the blocks which are brought to the read cache are zero-reuse or dead-on-arrival, which means that after the blocks enter to the read cache, they are not accessed until they are evicted. Thus, a large portion of the disk read cache is nearly unused because of these dead blocks. In this thesis, we will design a disk read cache which does not allow to the dead blocks to enter the... 

One of the key challenges and issues in proper supply chain planning is that decision-making in one area affects other areas, and one-dimensional optimization of goals leads to inefficiency in other goals. One of the problems in this field is the realization of a multi-objective model of simultaneous economic and environmental planning in the supply chain. Accordingly, this study aimed to present a multi-objective model of simultaneous economic and environmental programming in the supply chain based on the goal programming of aggregator algorithms. This study is practical in terms of purpose and it is descriptive and developmental in terms of research method. In this way, using two models of... 

In a network of caches, the precious cache space must be efficiently managed. A wasteful cache management algorithm might make redundant copies of the same content at several caches. Therefore, there must be an algorithm (a.k.a admission policy) to find a proper location in the network for every content to be cached. One way to locate different content at different caches is based on content popularity. Thus, popular content is closer to requesters. However, measuring content popularity at every router is not practical due to the high overhead the algorithm imposes on the routers. A more practical approach is to distribute different parts of the content to several caches along the path from... 

The aim of this study is to evaluate the seismic performance of structures using a semi-active tuned mass damper minimizing the amount of structural damage caused by earthquakes. One of semi-active control mechanisms, which has been studied in recent years, is the damper with fluid controlled by a magnetic field (Magnetorehological Damper, MR). These type of dampers react to the magnetic fields that cause significant changes in the behavior of fluid flow. These dampers are acknowledged because of their simplicity, broad operating range as well as not requiring high-power energy sources. In this thesis, a MR damper is used instead of the existing viscous element of tuned mass damper. To... 

In this thesis, performance bounds for the optimal control of discrete-time LTI plants are proposed. Results of stable plants with relative degree but no finite nonminimum-phase zero that have been done in the literature, are reported. According to model-matching problem and Nehari’s Theorem for finding performance bound in discrete-time, an algorithm in seven steps is posed. Meanwhile by using of presented algorithm, a case of nonminimum phase stable plants and several cases of unstable plants for finding performance bound is studied. By using of Matlab, A program for performance bound in plants with no poles Nor zeros on the unit circle is presented.

 

CDMA is one of the main multiple access techniques. The aim of this work is to propose optimum signature codes to improve the performance of such systems. First, we introduce criteria such as Sum Channel Capacity and Bit Error Rate (BER) to measure the performance of a CDMA system. Also a set of measures named as Distance criteria are proposed to reduce the computational complexity. Various optimization methods are used to optimize these criteria such as Genetic Algorithms and the Particle Swarm Optimization techniques. Then, several sub-optimum signature matrices are derived based on different factors and criteria to improve the performance of Overloaded CDMA systems in terms of the sum... 

One of the most significant problems of oil regions is salinity of the produced water extracted from the well. Penetrating the produced water through the surrounding environments of the oil well in recent years, plenty of environmental problems, especially agricultural ones have been caused in these areas. According to the increasing trend of water salinity during the time, one of the urgent action in the oil industry of the country should be finding a way to reduce the amount of dissolved salt in the produced water. The purpose to this project has been representing a more appropriate configuration for desalination of the produced water. Therefore, the water sample containing less than 70000... 

A novel application of diazonium salts for grafting the sol-gel based sorbents was sucessfully introduced. Preparation of unbrekable sorbents has been on highly demand and sough after by many researches for several years. However, there are a few achivements in this regard, but it still remains as a big challenge.Regarding to this issue, diazonium salts were sucessfully applied for functionalizing the different substrates, in which there is no limitation in selection of substrates. Different substrates, metallic and non metallic, such as copper, brass, stailess steel and PTFE were chosen to be functionalized by chemical or electrochemical reduction of 4-Amino phenyl acetic acid. Then,... 

The ability of blockchain to record transactions and automatic execution feature in smart contracts, increase the speed of the supply chain and reduce unnecessary delays. A blockchain-enabled supply chain is more dynamic and responds to changes faster. This makes many processes more efficient in the supply chain. Supplier performance evaluation is an essential field in Supply chain management. At any time, by recording real-time data through smart contracts in the blockchain, it is possible to see the supplier’s performance in different aspects according to all the information recorded up to that moment. This research investigates the use of smart contracts and blockchain in solving supply... 

Due to the numerous climate fluctuations and inefficient management of water resources during recent decades in Iran, the condition of some wetlands has become critical and the need for rehabilitation has increased. The importance of the wetlands and plains ecosystem have led to initiate some extensive projects to preserve and revive them. While implementing the projects some questions have been raised by the scientists and public whether the impact and success of these projects are in direct with objectives of the restoration program or not.For instance, Urmia Lake as one of the most precious natural habitats of Iran and as one of the biological reservoirs of the world is selected for this... 

This study has been carried out for investigating the need for an appropriate and fast seismic analysis method to be applied in performance based design (PBD), and show the application of Endurance Time (ET) method and it’s advantages in PBD. Necessary theories were generated in hazard analysis, bi-directional seismic analysis, introduction of dynamic push-over curve and application. As a secondary goal, potential of this method in more complicated nonlinear domains is assessed. Application of ET and its advantages in PBD is shown with an example of SMF, NDCBF, CBF and BRBF building after modeling nonlinear interactional behavior of beams and columns, and also modeling buckling and... 

The preliminary design of building structures is normally based on the equivalent lateral forces provided in seismic design guidelines. The height-wise distribution of these loads is predominantly based on elastic vibration modes. However, as structures exceed their elastic limits in severe earthquakes, these design load patterns may not necessarily lead to efficient distribution of strength within the structures. To address this issue, several alternative load patterns have been proposed for the seismic design of non-linear structures. However, due to the simplifications involved in the development of these design load patterns, their adequacy needs to be assessed for different structural... 

The present paper discusses the possibility of adding recycled polymer fibres to high performance concrete (HPC). Fibres used in this study were recovered from discarded car timing belts. To investigate different characteristics of the concrete specimens several destructive and non-destructive tests, such as compressive strength, modulus of rupture, flexural toughness, ultrasonic velocity and electrical resistance tests were carried out. In addition, slump flow tests were conducted on the fresh concrete. Experimental results from the study showed that the use of low percentages (up to 0.5%) of waste fibres improved the modulus of rupture and flexural toughness. Based on ultrasonic and... 

This study proposes a probabilistic framework to quantify the seismic resilience of urban natural gas distribution networks. Infrastructure resilience is defined as the ability to maintain performance after a hazard or, in case of a loss of performance, return to the minimum desired level in the optimal time. The framework presented in this research is comprised of multiple interconnected probabilistic models. These models work in harmony to characterize the impact of the earthquake on various infrastructures such as the buildings and urban gas distribution network components, as well as the probable consequences of the earthquake. The post-earthquake recovery of the gas distribution network... 

In the last years, we have seen a rapid growth of data generation that leads to an increasing need for data analysis and big data technologies. Meanwhile, cloud computing witnessed great popularity and has become one of the best platforms for big data analytics due to its flexibility and scalability. However, there is not an obvious method for choosing the right cluster configuration for running big data jobs in clouds. Because different big data applications, workloads and cloud configurations can lead to different costs. Moreover, a heterogeneous cluster can use the benefits of distinguished properties of each machine to reduce the cost and execution time of the big data application. The... 

When the keywords in academic articles are collected and accumulated to achieve a certain amount, they will display a network property. This property can help us to get the hotspot graph of science by using the keywords network, which is directly related to the subject of the paper. Also by analyzing this network, it is possible to forecast the future science hotspots.By analyzing keywords network from complex networks point of view, we are able to predict the future hotspots based on current trends, previous growth patterns that happened or with the power of different centrality measures like eigenvector etc. As an example, when a new keyword appears in a paper for the first time, a complex... 

Deciding for the future is one of the key tasks that project managers must carry out. Accurate Estimate at Completion helps them make the right decision. Numeruse novel methods have been proposed for calculation of estimate at completion which most of them are based on Earned Value Management. The question is whether considering the resources, as the essential elements of activities and therefoe the project, would result in a more accurate Estimation. In this Thesis, we propose a method that uses resource performance and activity structure to calculate the Estimate at Completion. The method also forecasts future resource usage. To evaluate the proposed method, we generated fictitious... 

The performance evaluation involves a process by which the employees are periodically and officially evaluated. Major reasons of performance evaluation include, among others, identification of efficient employees and granting bonuses to them to create stimuli to improve their and other employees' performances. The main objective of performance evaluation constitutes study of people's performances in the organization in order for directors to take proper and required decisions to enhance both quantities and qualities of the employees' works. The performance evaluation is deemed to be a major critical function of the management of human resources to facilitate organizational effectiveness. In...