Sharif Digital Repository

Hydrodynamic mesoscopic equations are solved using boundary integral method to investigate the coarsening dynamics of two dimensional nanodroplets. The dynamics is probed by locating two drops on homogeneous, chemical heterogeneous and physical heterogeneous substrates respectively. For homogeneous substrate, the effect of different parameters like droplets distance, slip boundary condition, surface contact angle and disjoining pressure type on the dynamics is studied. Results reveal that increasing the contact angles to values larger than a critical value may qualitatively change the coarsening process and the profile of the disjoining pressure can appreciably modify the coarsening rate.... 

A droplet placed on the boundary of two solids with different wettabilities will move to the more wettable part. This is a well-known phenomenon and has been extensively used in a variety of processes and applications ranging from biological systems and ink jet printing to the commercial lab-on-a-chip. Because of its importance, many studies are conducted around this phenomenon. The difference between the equilibrium contact angles of the droplet on the two parts gives rise to an interfacial driving force which moves the droplet. Such a motion is not continuous as the droplet slides to the more wettable area, the driving force diminishes and consequently the droplet stops. A non-stop motion... 

Mesoscopic hydrodynamic equations are solved employing a VOF based method to investigate the equilibrium shape of nanodroplets positioned over various topographic geometries of the supporting substrate for three-dimensional systems. By taking into account liquid-liquid and liquid-solid interactions a complex distribution for inter-molecular forces over the substrates (the disjoining pressure) is observed. In this research we show that motion of nanodroplets not only caused by contact angle difference in drplets two sides, but also depend on disjoining pressure parameters.Geometries with increasing complexities, from wedges to three dimensional edges and wedges, were explored with the main... 

Due to the physical limitations of the conventional 2D ICs at Giga-Scale Integration, modern technologies have been emerged. Among them, through silicon via (TSV) - based 3D ICs have been used to continue Moore’s law in the interconnect era. In these systems, dies are stacked at z-direction after wafer thinning. Electrical connections between stacked dies are done by TSVs. One important advantage of 3D integration technology is their ability to stack heterogeneous systems with different technologies on a single chip. This will not only increase interconnect density but also will reduce the delay and power consumption. However, nowadays, fabrication and optimum design of TSVs are still big... 

Millimeter-wave imaging is used in a vast applications like security, medical and non-destrcutive testings. Frequency scanning antenna is one of the optimum solution in mm-wave imaging systems, because of its accuracy, agility and low cost. In this method, changing the frequency plays the main role and leads the main beam to scan the space. In this thesis, by observing different frequency scanning structures, like microstrip antenna, slotted waveguide antenna array, substrate integrated waveguide leaky-wave antenna, different structures are designed and simulated. The antenna, which results in the best performance for an imaging system is selected for fabrication and measurement. The... 

An important issue in High-Frequency circuits is the transmission of electrical signals in Integrated Circuits and Printed Circuit Boards (PCBs). At high frequencies, however, the often used transmission lines suffer from high conductor and substrate loss as well as unwanted electromagnetic coupling to other circuit elements caused by parasitic substrate surface. One method through which both of the above problems may be solved is utilizing waveguide structures on PCBs and ICs. In this way, due to the reduction of conductor loss, a large proportion of signal passes easily. Moreover, and because of closed nature of cavity waveguides, neighboring circuits are protected against electromagnetic... 

The Cu2ZnSnS4 (CZTS) quaternary compound, with suitable optical and electrical properties, is one of the most interesting materials for absorber layer of thin film solar cell. Since all constituents of CZTS, are abundant in earth’s crust and non-toxic, it is a proper replacement for the materials like CdTe and CuInSe2. The CZTS pellet was synthesized by the solid-state reaction and deposited on soda lime glass substrates by pulsed laser deposition (PLD) method. PLD technique has the advantages of offering stoichiometric preservation during the materials transformation from target to substrate and good crystallinity due to the highly energetic species. CZTS has was deposited in order to... 

Ridge gap waveguide is a new technology with low loss and high power handling capability in millimeter wave(mm-wave) frequencies. In this technology there is no need for electrical connection between the constitutive parts and using dielectric material as a substrate. This thesis focuses on the capabilities of this technology in realization of devices used in communication systems at the mm-wave frequency. Novel devices based on this technology have been designed, fabricated and tested. The main goal of the thesis is realization of the whole RF front end of a communication system in Ka band based on this technology. So at first step, a ridge gap waveguide transmission line is evaluated and a... 

By considering the effect of surface/interface stress, classical problems of the interaction between dislocations and inhomogeneities are addressed. Especifically two distinct problems are solved, the first one is consisted of an edge dislocation located near an elliptical nano-inhomogeneity and the second one hasa screw dislocation laid in the core-shell nanowire. The stress field as well as the image force on the dislocation are calculated and discussed in detail. Results show that by decreasing the dimension of the problem to nano-scale, the differences between classical elasticity and surface approachincrease rapidly. By considering the effect of the surface/interface stress, new... 

Graphene is a single-atomic two-dimensional crystal that has considerable properties due to its unique structure and physics with applications in different fields. Due to its atomic thin thickness, substrates have a considerable effect on the electrical properties of Graphene. As these effects are determinative of the general behavior of systems, one should consider this effect in the design and fabrication of a device. Moreover, the conventional fabrication methods for Graphene-based electronic devices restrict the possibility of the device fabrication on a wide range of substrates, specially flexible and biocompatible substrates.In this work, the LPCVD Graphene growth process has been... 

In this thesis a substrate integrated waveguide (SIW) filter is designed and constructed using the contour integral method. A substrate integrated waveguide can overcome the drawbacks of regular waveguides, namely bulkiness, high costs and the difficulty to be integrated with other elements in high frequencies. In planar structures with arbitrary shapes where green’s functions aren’t available, we can use the contour integral method to construct the impedance matrix. Because the SIW structure supports TEn0¬ modes, we can consider SIW as a planar structure and thus use the contour integral method. Regular filter structures are usually analyzed using the FEM method (with HFSS) or the FIT... 

In the recent years, there has been great interest in exploring methods for assembly and manipulation at the micro/nanoscale to build miniaturized systems, devices, structures, and machines. This thesis aims at two-dimensional manipulation of nanoparticle using Atomic Force Microscope (AFM) probe. The nanoprobe is used to push the spherical micro/nanoparticle. Continuum based modeling and simulation of the manipulation task is presented. The proposed nanomanipulation model consists of all effective phenomena in nanoscale. Nanoscale interaction forces, elastic deformation in contact areas, and friction forces in tip/nanoparticle/substrate system are considered. The utilized friction models... 

Hydroxyapatite (HA) is an attractive biomaterial due to its close chemical composition to bone and teeth. However, HA is brittle and has low strength under bearing loads, resulting in limition for orthopedic and dental applications. Two creative approaches have been developed to overcome this problem, using bioactive HA as coatings on metallic implants or as ceramic/metal composites. Carbon nanotubes (CNT) possess excellent mechanical properties to play the role as reinforcement for imparting strength and toughness to brittle hydroxyapatite (HA) bioceramic coating. Moreover, The addition of TiO2 to HA coatings has attracted considerable attention, since TiO2 is capable of increasing the... 

In this thesis, the improving effects of deposited metal oxides onto or next to each other and the advantages of every metal oxide were considered. In the next step, the substrate improvement was studied and the porous metal oxides with ideal supercapacitive properties with porosity increase of substrate were obtained.CoFeO2 supercapacitor was prepared by chronoamperometric ethod.CoFeO2waselectrodeposited at room temperature and presents wide potential window and good capacitive properties in comparison with other metal oxides.Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by chronometric method onto stainless steel substrate.... 

In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy... 

In this research, sliding contact problem of a rounded apex wedge with a FG coated substrate is investigated. The structure includes two components. The first is the FG coating and then, the homogeneous substrate which is connected to the FG coating. Usually, it is considered that the homogeneous substrate is a metal and properties at the connection are metallic. Then, properties varies gradually through the thickness of the FG coating, so, the material at the surface of the structure is a ceramic. It is assumed that, properties varies exponentially and continuously through the FG coating and the poisson’s ratio is constant. Beside, it is supposed that the conditions of coulomb friction... 

Thin films of materials, in order to have magnificent structure and properties, can use in complicated technology such as; electronic, optic and magnetic systems. Printed interconnects can be made by the deposition of suspensions of metal nanoparticles (e.g., silver and gold) followed by thermal sintering. The nanoparticle sintering process involves atomic diffusion resulting in shrinkage. As a result, the interconnects are prone to residual stresses generated during the thermal sintering process. The residual stress can cause cracks and delamination in the thin films and can cause permanent geometrical changes in the underlying substrates which may affect the functionality of the... 

A microbial fuel cell (MFC) is a bioreactor that utilizes chemical energy in the chemical bonds of organic compounds to electrical energy production through catalytic reactions of microorganisms under anaerobic conditions. In this study, the performance of a dual chamber, mediator-less anode, graphite electrodes MFC employing mixed consortia as anodic inoculums and using a combination of formalin and glucose as substrate was investigated. Different MFCs with different concentration of formalin and fixed concentration of glucose was operated to elucidate the difference in power generation and removal of formalin as an industrial pollutant under similar operating conditions [ambient pressure;... 

Asparagainase is a therapeutic enzyme which has been a subject of research for decades. The enzyme catalyzes the hydrolysis of the amide group in asparagine and similar amides. Altering the substrate specificity and stabilization of this enzyme can increase its therapeutic properties. Moreover, asparaginases may be evolved to catalyze the hydrolysis of other similar compounds. These can be achieved through directed evolution and computational methods.In this study, the gene encoding L-asparaginase II enzyme from E. coli was amplified by polymerase chain reaction (PCR) and was cloned into an expression vector. The recombinant protein was expressed by an appropriate host secreting the... 

L-asparaginase II is an amidohydrolase which hydrolyzes L-asparagine to furnish L-aspartic acid and ammonia. The enzyme has played an important role for 40 years in treating cancer in persons with juvenile leukemias or lymphomas. Furthermore, the enzyme has become important in food industries and biosensors technology.In this study, the expression of recombinant L-asparaginase II in E. Coli was optimized and the purification of this enzyme from growth culture was carried out with nickel-charged affinity resin. Afterwards, the activity, and kinetic parameters of purified recombinant L-asparaginase II including Km, kcat, Vmax, and enzyme efficiency were measured.In the next step, random...