Sharif Digital Repository

The aim of this study was to investigate the rate of increase in temperature of a phantom equivalent to body tissue by different groups of magnetic iron nanoparticles in the external magnetic field to kill cancer cells based on the hyperthermia method. To achieve this goal, three groups of dextran magnetic nanoparticles with different properties and reduced iron oxide-graphene oxide magnetic nanoparticles by M-rGO supercritical synthesis method were used. After XRD, FTIR, SEM, FESEM, VSM, TEM characterization tests, these materials were placed in a phantom made of agarose gel and with the same properties, in a magnetic field with fixed characteristics for all groups and during the process of... 

Managing health data and providing remote treatment services to patients has always faced security and privacy challenges. Because of the importance and sensitivity of this data, the use of centralized networks such as cloud space and trustin a cloud server can be dangerous, due to the lack of complete trust in the cloud server. To prevent the threats of centralized systems, we provide a decentralized blockchain-based system in which miners, in addition to authenticating physicians and patients, are also responsible for searching encrypted data and all user activities can be tracked in the distributed ledger. The proposed scheme preserves data privacy, and there is no need to trust a server.... 

Disorders of the lumbar spine are prevalent within the realm of musculoskeletal issues, emphasizing the importance of investigating contributing factors. This research focuses on assessing how flexible footwear influences the kinematics and dynamics of the vertebral column during drop vertical jump. The study involves mechanical tests on various footwear types, including simple, flexible and re entrant shoes with differing levels of rigidity. Bending tests were performed on simple and flexible shoes with hardness of 50 Asker C and flexible shoes with hardness of 40 Asker C. Additionally, compression tests were carried out on all soles at two different angles. The Bending tests revealed that,... 

Distal humerus fractures commonly take place in adults with low bone mineral density causing major technical challenges upon orthopedic surgeons. Persian fixation method was introduced as a novel technique to stabilize small fragments in comminuted distal humerus fractures using a set of K-wires and reconstruction plate. The objective of the present study is to measure the stiffness and stability of this technique and analyze the effect of influential parameters with numerical simulation and biomechanical testing on a cadaveric specimen. Furthermore, we were able to propose new method to model plastic deformation of implants in surgery.Validation of the finite element (FE) model was... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related... 

A liquid crystal is a state of matter composed of highly anisotropic building blocks. When liquid crystals are exposed to surfaces with given shapes and anchoring conditions, the orientation of their molecules gets spatially disordered and topological defects may form in the system. The interplay between liquid crystals and the geometry and topology of the colloidal particles has motivated extensive recent studies.In this thesis, we present the numerical modeling results for two faceted colloidal particles in a thermotropic nematic liquid crystal. To obtain the equilibrium nematic field with a finiteelement method, we numerically minimize the free energy of the system that based on the... 

Providing high bandwidth network infrastructures for ever increasing need of data transport is of great importance. The underling infrastructure for many communication services such as GSM/3G/4G mobile networks and Internet services is Synchronous Digital Hierarchy (SDH) optical transport systems. SDH are standardized protocols that multiplex multiple lower rate digital bit streams, such as E1 and Ethernet, and transfer them synchronously over optical fiber using lasers or LEDs. In addition to high data transfer rates, flexible network management and protection mechanisms have great importance, hence are part of SDH standards. In order to obtain flexible network architecture and protected... 

Development of Smart Grid and deployment of smart meters in large scale has raised a lot of concerns regarding customers’ privacy. Consequently, several schemes have been proposed to overcome the above mentioned issue. These schemes mainly rely on data aggregation as a method of protecting users’ privacy from the grid operators. However, the main problem with most of these schemes is the fact that they require a large amount of processing power at the meter side. This, together with the fact that smart meters don’t usually have a powerful processor, can cause the unavailability of smart meter data at the required time for operators of the grid, and at the same time disables smart meters from... 

Secure routing is a major key to service maintenance in wireless ad hoc networks. Ad hoc nature exposes the network to several types of node misbehavior or attacks. Wormhole attack is one of the most severe active attacks to mobile ad hoc networks. Noting the resource limitations in such networks, nodes may have a tendency to behave selfishly. Selfish behavior can have drastic impacts on network performance. We have proposed a Misbehavior-Tolerant Multipath Routing protocol (MTMR) which detects and punishes all types of misbehavior such as selfish behavior, wormhole, sinkhole and grey-hole attacks. The protocol utilizes a proactive approach to enforce cooperation. In addition, it uses a... 

In recent years, parallel to the development of industrial, the use of organic solvents and the environmental pollution caused by their increasing, more attention to remove these contaminants growing. Among the various absorbents to absorb pollutants from the environment, iron oxide nanoparticles have many applications in absorption and removal of environmental pollutions due to their high specific surface area, magnetic properties and ease of separation. The aim of this research is synthesis of a magnetic gel for absorption of organic solvents which in its structure magnetic nanoparticle and hydrophobic monomer is used. The most important advantages are the ease of isolation of the desired... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

Nowadays adhesives with the development of technology and the numerous benefits they have, are becoming a replacement for traditional joining methods in industries like electronics, automotive, aerospace, and naval. That’s why the need for studying the fracture behavior of adhesive joints becomes vital. So far, many engineers and designers are trying to investigate the behavior of adhesive joints in different conditions that these joints actually deal with. Also, finding solutions to predict the behavior of adhesive joints is the researchers’ other concern. The purpose of this research is to find the effect of factors that are less focused in the literature, on the fracture of adhesive... 

Auxetic materials have a negative Poisson ratio (NPR), which is their most distinguishable characteristic as compared to regular materials. Test specimens were made of conventional polyurethane (PU) foams according to ASTM ; then, with a thermo-mechanical process, the foam was converted to auxetic PU foam. The reproducibility of specimens' fabrication was checked with CoV= for the final foam thickness. With regard to the fact that changing loading conditions can vary Poisson's ratio, in this study, the variations occurred in Poisson's ratio due to changing loading conditions are investigated. The applied strain and strain rate were altered in experiments and statistical analysis was... 

In the past, lead-based solders with homogeneous and isotropic behavior were used in microelectronic packages. But today, due to the environmental concerns of lead, lead-free solders have been developed, which consist of a high weight percentage (more than 90%) of tin. Tin crystal shows significant anisotropic behavior, which leads to an anisotropic joint response in miniature solder joints with a small number of grains. In the first part of this research, using the crystal plasticity model, the anisotropic plastic response of tin grain was extracted from bulk solder stress-strain curve, then it was implemented in Abaqus software using built-in Hill's anisotropic plasticity model to consider... 

Single lap-shear (SLS) specimens of 2.54, 6.35 and 12.7 mm long SAC305 solder joints were prepared with three different adherend thicknesses. The fracture force was measured at a shear strain rate of 0.01 s-1 for different geometries in the lap-shear configuration in which mode ІІ loading is established. Elastic-plastic fracture mechanics (EPFM) theory was considered to find the energy dissipated in each case using a finite element model (FEM). The fracture energy was found by cohesive zone modeling (CZM) using pre-defined parameters. Both 2D and 3D models were used to explain the variations of fracture energy by evaluating the effective factors that demonstrated the level of constraints on... 

Double cantilever beam (DCB) specimens were prepared according to standard surface mount technology (SMT). The samples were stored inside an environmental chamber at two different relative humidity values (i.e. 40 or 100%) for either 2 or 4 hours. Then they were aged at 25ºC, 75ºC or 125℃ for the same time. Finally, after being cooled to room temperature, fracture tests were performed under mode-I loading conditions at a strain rate of 0.03 s-1 at room temperature. Storage time did not have a significant effect on the fracture behavior. The fracture load and energy of the solder joints decreased significantly when the temperature was increased from 25 to 75℃. By further increase in the... 

In this investigation, the mode I fracture behavior of an epoxy adhesive joint has been investigated to probe the combined effects of adherend Young's modulus and thickness, strain rate, and adhesive length. Experimental fracture testing was conducted on double-cantilever beam (DCB) specimens under three various strain rate thresholds, namely, quasi-static (0.0005 s-1), low (0.015 s-1), and intermediate (0.5 s-1). The specimens were constructed with varying adherend materials (i.e., copper, aluminum), thickness (12-20 mm), and adhesive lengths (25-75 mm). The fracture load was measured in each experiment, and the critical strain energy release rate, JCi, was calculated via a finite element...