Sharif Digital Repository

Nowadays, many biological systems are modeled by bipartite networks. So, using network's concepts and techniques such as community detection may lead us to more accurate outcomes.In this thesis, we have presented an algorithm for detection of communities in a network of patients with Peripheral Nervous System (PNS) issues. The bipartite network of the patients is formed based on the dataset which is collected with cooperation of a Spinal Specialty Clinic. In our algorithm, called MRComSim, three different methods are used to project the bipartite graph to unipartite graph. Then the projected unipartite graph of each method is used for community detection. The output result of our algorithm... 

The fabrication of potassium sodium niobate piezoceramic with oriented microstructure and study of its piezoelectric properties is one of the main objectives of the present study. For this purpose, first the raw materials were synthesized. solid state reaction and topochemical reaction were used for the synthesis of potassium sodium niobate and sodium niobate respectively. The X-ray diffraction results determined that the powder synthesized by the solid state method in the binary system KNbO3-NaNbO3 is closer to the morphotropic phase boundary compared to the powder synthesized in the ternary system Na2CO3-K2CO3-Nb2O5. Particles morphology also includes coarse cubic shape and small equiaxed... 

Neither state planning nor economic liberalization has been the answer for developing countries to escape from the middle-income trap, mainly due to presence of institutional voids and due to the governance of hindering institutions. Therefore, we need another explanation for how of the development, which must include how institutions change and how new institutions and new institutional fields emerge. Developing countries are full of institutional voids and the governance of hindering institutions. Therefore, the process of economic development in these countries, is beyond the power of market and state, and needs agency. Responding to the recent call by the literature for doing more... 

Detecting small particles is one of the needs of researchers. Industrial and research developments in nano and biotechnology expands the need of suitable equipments. One of the challenges in this field is detecting the qualitative and quantitative properties in the sample. Until today there are numerous methods to detect the properties of the particles and different commercial machines are presented for this purpose. In this method, based on one the methods of detecting particles, called resistive pulse sensing, a mechanism is composed and by its help 7 um and 800 to 2000 nm particles are distinguished separately. This sensor has two important parts: the fluid and the electronic. In the... 

Titanium alloy Ti-6Al-4V ELI with high biocompatibility and corrosion resistance, has a lot of applications in biomedical engineering. Disadvantage of this alloy is it’s disability to create a fast and good contact with the host/bone environment, after implanting in the body. Beside that it has low wear resistance. Nowadays to optimize the wear resistance, bioactivity and osteoconduction of surface of implants which are made from this alloy, the surface morphology are optimized in size and distribution. Different surface treatments are used for producing rough and porous surfaces to improve bioactivity along with wear resistance. In this study, surface modification of Ti-6Al-4V ELI was done... 

Commercially pure titanium (CP-Ti) is an important groups of titanium family and because of high strength, low density, high corrosion resistance and biocompatibility, this group of titanium is a suitable choice for application at chemical, petrochemical and medicine industry. Nowadays surgeons have a tendency toward use of CP-Ti instead of Ti-6Al-4V alloy. Moreover, because of body anatomy limitation, use of thick sheets result in high volume and damage soft tissue. Therefore, for sheet thickness reduction, study of the effects of metallurgical and geometrical parameter on fracture behavior of thin sheets is important. In this study, the fracture behavior of CP-Ti thin sheets investigated.... 

Reviewing trends of energy consumption in the world reveals that sooner or later energy resources will be depleted. This concerning rate of consumption has brought about more greenhouse gases (GHG) emission influencing deleteriously on environment and climate. Human has continued energy consumption to maintain and improve the quality of his life through industrial production. Industry as a significant energy user owns considerable contribution to this consumption. Several attempts have been carried out to develop energy management systems in order to improve the energy efficiency of industrial sectors. Whilst they are comprehensive and could be applied to any sector, there is lack of... 

There are many industries in the world that produce colorized wastewater. Because of the complex structure and good solubility of dyes, such industries have problem treating this wastewaters. On the other hand, because of the toxicity of these materials for water living, dye removal from discharged wastewater of these industries is very important. In recent years, researchers have become interested in the synthesis of dye Nano adsorbents and they have published many works on this subject. The important parameters in the synthesis of such adsorbent include; non-toxicity, high adsorption capacity and easy separation. In this project, cellulose was extracted from bagasse and then CMC was... 

In this thesis, the Artificial Neural Networks (ANN) will be used in Automatic Speech Recognition (ASR) instead of Hidden Markov Models (HMM). Hidden Markov Model is one of the most dominant Bayesian network technologies and is the most successful model in current ASR systems. However, excessive training time is a major issue in speech recognition based on Hidden Markov Model (HMM). This thesis presents an Artificial Neural Network language model for human speech by mapping the spectral features of speech namely the formants, cepstrum (Mel-Frequency Cepstral Coefficients (MFCCs)) and Power Spectral Density (PSD) as features of samples of specific words into a discrete vector space. The... 

Solid oxide fuel cells are used to convert solid-state energy to direct electrical current by electrochemistry mixing a gas fuel and an oxidant in an oxide electrolyte. One of the most interesting aspects of this field for the researchers is the reaction between the metal interconnect and the glass sealant. In the current research, deposition of the YSZ coating onto the metal interconnect in order to impede the reaction with glass sealant and prohibition of its oxidation in oxidizing/reducing environment in high temperature, was mainly investigated. Effect of applying YSZ Thin layer in the intersection of Crofer steel and glass sealant on strength and chemical durability of these two... 

Blockchains are not scalable by design, and it is known to be the most important barrier in the way of development of these systems. One of the main approaches to this problem is sharding, that is under development in industry and academia. Sharding scales the system up by reducing redundancy, that makes blockchains vulnerable in terms of security. In this paper, we will study the effect of sharding on availability of these systems, and will show that sharding can magnify the unavailability of the service, and introduce an adversary threat model that takes real concerns of availability in today’s Internet like DoS attacks into account. We also introduce a basic unavailability-resistant... 

Land subsidence is a gradual settling or sudden sinking of the land surface from changes that take place underground. There are different causes of land subsidence; most notably, groundwater overdraft and severe weather conditions. Subsidence of the land surface due to ground water overdraft is caused by an increase in the intergranular pressure in unconsolidated aquifers, which results in a loss of buoyancy of solid particles in the zone dewatered by the falling water table and accordingly compaction of the aquifer. In this study, an experimental approach was developed to examine applicability of Microbially induced carbonate precipitation (MICP) for land subsidence control under... 

The emerging applications of machine learning algorithms on mobile devices motivate us to offload the computation tasks of training a model or deploying a trained one to the cloud or at the edge of the network. One of the major challenges in this setup is to guarantee the privacy of the client data. Various methods have been proposed to protect privacy in the literature. Those include (i) adding noise to the client data, which reduces the accuracy of the result, (ii) using secure multiparty computation (MPC), which requires significant communication among the computing nodes or with the client, (iii) relying on homomorphic encryption (HE) methods, which significantly increases computation... 

In this thesis, we consider multiple-antenna K-user interference channels with backhaul collaboration in one side (among the transmitters or among the receivers) and investigate the trade-off between the rate in the channel versus the communication load in the backhaul. In this investigation, we focus on a first order approximation result, where the rate of the wireless channel is measured by the degrees of freedom (DoF) per user, and the load of the backhaul is measured by the entropy of backhaul messages per user normalized by log of transmit power, at high power regimes. This trade-off is fully characterized for the case of even values of K, and approximately characterized for the case of... 

Lightweight clients are a type of blockchain users who do not store all the blocks in the blockchain due to limited resources. These users store only a small part of each block and when needed, request transactions from full nodes that store the entire blockchain. These users have no role in block validation and only want to receive transactions related to their addresses with proof of the inclusion in the block from full nodes.Since light clients rely on full nodes for receiving transactions, their privacy against full nodes is important. The current implementation of Bitcoin uses Bloom filters for privacy, but this offers very little privacy to the users.In this thesis, we study the... 

Blockchain technology presents a decentralized management structure designed to cater to various needs, such as decentralization and the elimination of single points of failure. With the evolution of blockchain technology, smart contracts have emerged as a remarkable platform for facilitating financial activities in a decentralized manner. Among the different types of smart contracts, decentralized exchanges stand out by their absence of a central authority overseeing user transactions. This lack of a central oversight exposes users of such exchanges to potential attacks from malicious entities. A key challenge faced by these exchanges is the concept of Miner Extractable Value. Miner... 

Hydrogen can serve as a green alternative to fossil fuels and contribute to improving environmental conditions. In this context, reducing the cost of hydrogen production is of fundamental importance. It is necessary to examine the impact of influential environmental parameters on hydrogen production cost reduction. In this study, a relationship for optimizing hydrogen production in two scenarios, with constant anode pressure and variable cathode pressure, as well as both variable anode and cathode pressures, has been presented. Furthermore, the effect of various parameters, including temperature, pressure, proton exchange membrane thickness, and solar cell efficiency, on hydrogen production... 

The present study provids an experimental investigation on two-pase flow characteristics in microchannels. Experiment were conducted with a mixture of air and water in horizontal circular pyrex channel with 400µm inner diameter. The pressure drop and flow rates of the liquid and gas were measured using new method and images of the flow patterns recorded by high shutter speed camera. The gas and liquid superficial velocity ranges were 0.025-12.5m/s and 0.016-3.6m/s, respectively. The flow pattern map is developed from the observed flow patterns based on phases superficial velocity as wel as We numbers of liquid and gas phases. The flow pattern map is compared with those of larger channels.... 

A finite difference technique is developed to predict the second stage creep displacement rates and stress analysis of a short fiber metal matrix composite subjecting to a constant axial load. The exponential law is adopted to describe the matrix creep behavior. Also, a method for prediction of interfacial debonding at fiber/matrix interface is developed using a stress based method. The obtained results could greatly help to better understand the flow pattern of matrix material and the load transfer mechanism between fiber and matrix. The stress components and strain rates are also validated by the available FEM and experimental results