Nanomaterials have been studied extensively in the last decade in the context of many applications such as polymer composites, energy harvesting systems, sensors, ‘transparent’-like materials, field-effect transistors (FETs), spintronic devices, gas sensors and biomedical applications. Graphene, a recently discovered two-dimensional form of carbon has captured the interest of material scientists, and physicists alike due to its excellent electrical, mechanical and thermal properties. Graphene has also kindled a tremendous interest among chemists and cell biologists to create cellular-electronic interface in the context of bio-electronic devices as it can enable fabricating devices with enhanced potential as compared to conventional bio-electronics. Graphene’s unique electronic properties and sizes comparable with biological structures involved in cellular communication makes it a promising nanostructure for establishing active interfaces with biological systems. In the recent past Field effect transistors (FETs) have been successfully fabricated using carbon nanotubes (CNTs) and nanowires (NWs) and electrical characterization of these FETs were done by interfacing them with various cell cultures, tissues and muscle cells. In these cases, exceptionally high surface area to thickness ratio of FETs provides high percentage of collectible signals and the cells that are used for the study are typically placed on the FET. In this thesis, we examine a different approach towards forming bio-electronic interfaces by covering the graphene oxide (reduced) sheets on the yeast cells. Graphene oxide and reduced graphene oxide sheets as two-dimensional electronic materials have very high charge carrier mobility, extremely high surface area to thickness ratio, mechanical modulus and elasticity. We report the synthesis of graphene oxide using wet chemistry method, reduction of graphene oxide using different reducing agents and electrical characterization of graphene oxide’s conductivity. Micro-meter sized graphene sheets are used to encapsulate the yeast cells with the aid of calcium and gold nanoparticle chains. We also demonstrate that graphene sheets form electrically conductive layers on the yeast cells and developing an electromechanical coupling with the cell. The mechanical and electrical characteristics of graphene sheets are highly dependent on the cell volume and structure which are in turn related to the environment around the cell. Furthermore, using the same principle of electromechanical coupling we study the dynamics of cell surface stresses and cell volume modification, which are of importance in processes such as cell growth, division, and response to physiological factors such as osmotic stresses.

<i>N</i>-heterocyclic carbenes (NHC) have widely been used as spectator ligands in organometallic chemistry. Chelating bidentate di-<i>N-</i>heterocyclic carbenes (diNHC) provide additional entropic stability to their complexes relative to monodentate analogues. The steric and electronic environment around the metal centre can be fine-tuned by varying the substituents on the nitrogen atoms of the diNHC ligand. Synthesis and characterization of air and moisture stable bis(diimidazolylidene)nickel(II) complexes, [(diNHC)2Ni]2+, and their corresponding silver(I) and palladium(II) analogues are described.<p> Investigations into the catalytic potential of diNHC complexes of nickel as an alternative to palladium systems in carbon-carbon coupling reactions are discussed. In the Suzuki-Miyaura coupling reaction, the [(diNHC)2Ni]2+ complex was active for the coupling of aryl chlorides as well as aryl fluorides. The analogously synthesized Pd(II) complexes resulted in formation of (diNHC)PdCl2 species which were not active for the coupling of aryl fluorides. Transition-metal free coupling reactions were investigated and the results indicated that in the Mizoroki-Heck reaction, aryl iodides could be activated in the absence of nickel or palladium precatalysts when using Na2CO3 or NEt3 as base, while in the Suzuki-Miyaura reaction, aryl iodides and aryl bromides could be activated without any precatalyst when K3PO4 was used as base.<p> A general route into the synthesis of non-symmetrically substituted ligand precursors has been developed. Synthesis and characterization of non-symmetrically substituted ligand precursors, and their corresponding silver(I), palladium(II) and nickel(II) complexes are described. The activity of one of the non-symmetrically substituted (diNHC)Pd(II) complexes in the Suzuki-Miyaura coupling reaction of bulky substrates has been investigated. Non-symmetrically substituted diNHC ligand precursors with a hemi-labile pyridine arm have been synthesized and their corresponding Ni(II) and Pd(II) complexes are described.<p> Attempts to synthesize three-coordinate Pd(II) complexes using bulky â-diketiminato ligands are also discussed.

Active electronically scanned array (AESA) radar systems for military and commercial applications have fueled interest in low-cost, high-performance technologies capable of delivering integrated circuits for transmit-receive (T/R) modules and monolithic radar systems. Silicon-Germanium (SiGe) Heterojunction Bipolar Transistor (HBT) technology has been flagged as a strong candidate for such applications because of its high-speed low-noise devices, high integration capabilities, and relatively low cost. This work investigates integration issues associated with monolithic silicon-germanium radar systems for military (8-12 GHz) and automotive (24 GHz) applications. The design and implementation of critical circuits, such as phase shifters, power amplifiers, up-conversion mixers, down-conversion mixers, and voltage-controlled oscillators will be investigated, along with the system level considerations associated with these components. These building blocks have been fabricated and tested at wafer level, utilizing commercially available SiGe HBT BiCMOS technologies, demonstrating acceptable performance for these applications. Preliminary research into substrate coupling associated with these BiCMOS technologies will also be presented, demonstrating the potential for circuit-to-circuit substrate coupling to occur at these microwave frequencies.

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A study of double-variable-curvature microlenses (DVCM) for promoting coupling efficiency between the high-power 980-nm pumping laser diodes and the single-mode fibers has been proposed. In comparison with the previous works on asymmetric fiber microlenses fabricated by the multi-step processes with complicated fabrication, the advantages of the DVCM structure for achieving high coupling are a single-step fabrication, a reproducible process, and a high-yield output. In the fusing procedure, the slight arc fusion was mainly applied for fine polishing merely instead of reshaping for the reason that the fabricated double-variable-curvature fiber endface (DVCFE) was very close to the ideal shape. Hence, the fabrication time was reduced and the yield was promoted due to the withdrawn step of tip elimination. In this study, the geometric center of the fiber was defined through, the cladding diameter and the core diameter, for comparison to measure the offset. The offset measured by the core diameter was more accurate and coincidence with the coupling efficiency in the experiment. In the fabricated 45 DVCMs, to achieve the average coupling efficiencies higher than 84%, the offsets were ought to be controlled in merely less than 0.6£gm with the curvature radii in the minor axis ranged from 2.4 to 2.9£gm (with tolerance of 0.5£gm). Alternatively, the offsets were ought to be controlled in less than 0.3£gm though the curvature radii in the minor axis ranged from 2.4 to 3.7£gm (with larger tolerance of 1.3£gm). However, it was more difficult to control over the offsets than the curvature radii in the minor axis while fabricating the DVCMs. In conclusion, to achieve higher yield, it was relatively practical to control the offsets of fiber microlenses to be less than 0.6£gm with 2.4 to 2.9£gm curvature radius. As a result, the coupling efficiencies were all higher than 80%.

The purpose of this study is to use multi-functional optical fiber processing platform produce 2X2 single-mode fiber coupler, and use theory and simulation to analyze, as the basis of the starting, development of novel fused coupler device. The characteristics of this coupler is a 2x2 single-mode fiber coupler in which a single-mode fiber replaced by our laboratory to manufacture the capillary fiber. The use of this coupler is similar to the use of single-mode fiber refractive index of the solution pumped capillary fiber to a liquid switch fiber coupler. We know that the refractive index decreases as the wavelength increases, the slope of the different materials for this change is different, and due to the different materials, the thermal coefficient of refractive index is different, so we can be found in the case of different temperatures, the refractive index of the two materials are equal, and other wavelength is different, therefore, only when the same refractive index of the wavelength in order to fully coupled. The advantages of this coupling is temperature control of its maximum coupling wavelength range, and the capillary fiber core is liquid, we can use this measurement technique for the development of liquid, if the later then the single-mode fiber to replace the other refractive index different fiber, you can use this method to measure the other liquid. Next, use simulation software to simulate this coupler, the coupling wavelength and coupling efficiency values of the change in refractive index different cases, in order to facilitate the produce this novel fused coupler device.

Use the adjustable diameter fiber splicing platform to manufactured coupler, N fibers were put into the appropriate aperture silica capillaries, and then changed the taper model to manufactured fiber coupler [1], and adjusted the taper model and fusion parameters to reduce the fiber transmission loss and reduce the diameter of the fibers to achieve the optical coupling effect. We preferred to the Eisenmann & Weidel in 1988 [2]. It is a low loss of the fusion type equilateral triangle of 3¡Ñ3 fiber coupler. And we will study the asymmetric shape of an 3¡Ñ3 fiber coupler, the research method is the use of arc heating. The fiber has smaller heating area and the heating position which can be controlled. With the parameters which BeamPorp, we cut the fiber coupler and to discuss its cross-section. By the different geometric distribution of fibers, and the core spacing, we discuss the spectra of the OSA to change the coupling site. We changed the interior structure to make the power coupling to a marked effect; if we could control the asymmetric coupler explicitly then we could achieve the transmission power [3], power coupling, and the multiple spectra of light.

In this paper, we propose tag antennas and reader antennas, which are suitable for radio frequency identification system. Antennas operating in the ISM and the UHF bands are designed. The antenna dimensions are minimized by employing the meander-line technology. Adopting the concepts of Yagi-Uda antennas, We use parasites to increase the antenna gain and to create an end-fire radiation pattern. The fact that the design comes without a ground plane can achieve cost down of the antenna. Higher antenna gains allow a greater effective read-zone distance. Also, the directional radiation pattern eliminates the degradation of performance due to multi-path loss. The design of tag antennas shows good performances in terms of both cost and antenna characteristics for radio frequency identification systems. The reader antennas are designed. Etching a slit in a square patch can achieve the requirement of circular polarization. It can effectively reduce the polarization mismatch when the tags are point to different orientation. Therefore the reliability of system operation will be improved. The antenna performance is measured by the experiments. Moreover, it will be compared with the simulation. In the latter part of paper, the simulation of the power coupling will be carried out. According to the result of power coupling simulation, we analyze and discuss which factor will affect the reliability of the identification. Identification failure will be effectively avoided and a robust identification system can be built if the analyses are properly employed.

Curvic couplings have been widely applied to various industrial applications. Presently the Gleason No.120 special grinding machine developed by Gleason Works Co. is one of the commonly used machine tool for the curvic coupling manufacturing. On the other hand, in response to the issue of improving the domestic design and manufacturing ability, an alternative manufacturing method of curvic coupling is introduced in this study. In this study the geometrical characteristics of the novel gear profile are investigated. Firstly, applying the spatial transformation matrix theorem to the relationship between the cutting tool path and the cutting tool position, the cutting tool profile equation of curvic coupling is successfully derived. Secondly, the mathematical model of the envelope surface of the generating tool, or generally being called the gear surface, is constructed based on the trajectory equation of the generating tool motion and the tool-workpiece meshing equation. Finally, the solid model is established based on the obtained mathematical model, and the comparison works with the conventional curvic coupling are also carried out. The analysis of gear surface is graphically depicted with respect to the various machining parameters. It is believed that this thesis provides a useful tool for the following studies of curvic couplings for the different demand of application fields.

In recent year, wireless communications systems require transmission of higher and higher data rates to foster various multimedia services. The multiple-input multiple-output (MIMO) antennas system has been studied to increase wireless channel capacity and reliability. The mutual coupling of MIMO antennas affects the capacity of the wireless channel. Traditionally, the minimal mutual coupling distance between antenna elements needs to be at least one half wavelength. When MIMO antenna system is used in miniature mobile device, the problem of mutual coupling becomes even more serious. In the first part of this thesis we propose a WLAN/WiMAX antenna that can be operated in 2.4 GHz (2.4¡V2.48 GHz) WLAN band; 2.5 GHz (2.5¡V2.7 GHz) and 3.5 GHz (3.4¡V3.7 GHz) WiMAX band. We use the inverted U slot band notch and omega slot band notch to reduce the mutual coupling in MIMO antennas. Our design is able to reduce the mutual coupling to be less than ¡V20 dB in all interested bands. In the second part, we propose a planar WLAN/WiMAX antenna that can be operated in 2.4 GHz (2.4¡V2.48 GHz), 5.2/5.8GHz (5.15-5.35GHz/5.725-5.825GHz) WLAN band; 2.5 GHz (2.5¡V2.7 GHz), 3.5 GHz (3.4¡V3.7 GHz) and 5.5 GHz (5.25-5.85 GHz) WiMAX band and mutual coupling of MIMO antenna is less than ¡V20 dB in all interested bands.