Coupling beams are structural elements used to connect two or more shear walls. The most common material used in the construction of coupling beam is reinforced concrete. The use of coupling beams along with shear walls require them to resist large shear forces, while possessing sufficient ductility to dissipate the energy produced due to the lateral loads. This study has been undertaken to produce a computational model to replicate the behavior of conventionally reinforced coupling beams subjected to cyclic loading. The model is developed in the finite element analysis software ABAQUS. The concrete damaged plasticity model was used to simulate the behavior of concrete. A calibration model using a cantilever beam was produced to generate key parameters in the model that are later adapted into modeling of two coupling beams with aspect ratios: 1.5 and 3.6. The geometrical, material, and loading values are adapted from experimental specimens reported in the literature, and the experimental results are then used to validate the computational models. The results like evolution of damage parameter and crack propagation from this study are intended to provide guidance on finite element modeling of conventionally reinforced concrete coupling beams under cyclic lateral loading.

Along with the rising and flourishing development of the modern technology and human knowledge, the demands for optical-electric products and communication systems are getting more and more. By combining the semi-conductor technology process with micro optical elements, a complete micro optical system can be integrated. The functions of a micro optical system include beam-splitting, beam-light offsetting, focusing, and switching, etc. Letting micro optical elements be integrated on a substrate, the fix and alignment problems, which are caused by the relative displacements between the elements, can be improved. Also, the production rate can be increased and cost can be reduced if the products are made by micro mold and array fabricated process. Thus, the technology of the Micro Optical Electro Mechanical System is widely applied to manufacture the products of optical-electric and communication, such as the backlight module of a LCD, projector, and optical fiber communication system, etc. The main purpose of this study is to design and fabricate a microball-lens array, and to apply it to couple optical fibers. The proposed product is a 3D micro-ball-lens array with vertical and non-vertical focus directions and better coupling efficiency. A v-groove is fabricated by using semi-conductor technology in order to fix the micro-ball-lens array and optical fiber such that an optical fiber switch coupling system can be obtained. The packaging of the optical fiber switch coupling system is formed by UV-cure and a microcap which is fabricated by MEMS. It can provide the protection to the system. Also, the completed system can achieve the demands of the industry fields such as precise localization, cost reduction and so on.

A simulation algorithm is proposed in this thesis to investigate the effects of lensed fiber parameters on the variation of radius of curvature of the melted lens and the coupling efficiency of butterfly type laser diode transiver module. Two different endface shapes, i.e. the taper and the conical-wedge type lensed fibers, will be studied. The effect of endface shapes, sizes, and the melting zone volume on the coupling efficiency of lensed fibers are simulated and discussed. In the study on the conical type lensed fiber, the MARC¡¦s elastic-plastic-thermal finite element model is employed to simulate the melting and the solidification processes at the fiber tip endface with different conical angles. The temperature dependent material properties are used to calculate the melting zone and the post-melten deformation during the heating process. The Surface Evolver Software has also been employed to simulate the solidified lens shapes. The variation of radius of curvature of the tip lens is analyzed. The ZEMAX optical analysis software is applied to explore the relation between the coupling efficiency and the distribution of the radius of curvature. The variation of laser signal coupling efficiency introduced from different conical lensed fibers is simulated numerically. A good agreement between the published measured data and the simulated results indicate the proposed simulation model is feasible. The effect of endface shape and molten zone size on the conical wedge type lensed fiber has been studied in a similar way. The coherence between the shape of solidified elliptical lens at fiber tip and the coupling efficiency for the 980nm LD will be explored. Different endface shapes will also be investigated by using the simulation model proposed previously. Different aspect ratio of the conical-wedge type tip will be introduced to compensate the elliptical LD ray model and to recover the coupling efficiency loss. The agreement between the results simulated using the proposed model and the measured data is examined. The simulated results indicate that the coupling efficiency of a butterfly type laser diode transever can be improved significantly by controlling the shape of the lens introduced in this type lensed fiber. The optimal grinding parameters and the melting parameters used to fabricate the lensed fibers will also be studied. The effects of the shape parameters, i.e. the conical taper angle, the wedge angle and the size of molten zones on the curvature variation of the lens will also be studied. A better understanding about the design and fabrication of the lensed fiber of a laser diode based transever module is expected from the results presented in this thesis.

For getting the position which can obtain the maximum coupling efficiency, fiber array and laser array need to be adjusted while the module of fiber array is packaging, than fastening it on the base. Nowadays, there are some methods for fastening the fiber array like adhesive, soldering and laser welding. But the material will discover some phenomenons like expansion and contraction during the process of heating and solidification. Those phenomenons will lead the system to deviate on the six degree of freedom (D.O.F). Because of the fiber array system will confront with the situation of deviation, the magnitude of coupling efficiency will drop down. It is because that the technique of laser welding will cause smaller deviation than other methods just mentioned, so the research choose the method of laser welding for packaging. The distance between fiber and laser array is too small to fasten the CCD on the directions of X, Y and Z axes while the research measures the deviation. So the research uses a mirror to reflect the image for obtaining the correct position of the space and Post-Weld-Shift measurement the deviation of system. Afterward, the research designs a structure for reducing the deviation and increasing the coupling efficiency of system.

Two new schemes of fiber microlenses for coupling between the high-power 980nm laser diodes and single-mode fibers (SMFs) are proposed. The quadrangular-pyramid-shaped fiber microlens (QPSFM) is fabricated by grinding a quadrangular-pyramid-shaped endface and then through heating in a fusing splicer to form an elliptical microlens endface. In comparison to the traditional wedge-shaped fiber microlens, the QPSFM structure can control two axial curvatures to form an elliptical microlens endface, and then control the aspect ratio of fiber far-field pattern to match the elliptical mode fields of lasers. The coupling efficiency of 83% for the QPSFM has been demonstrated. Another scheme of fiber microlens is the conical-wedge-shaped fiber microlens (CWSFM). The CWSFM is fabricated by grinding a conical-shaped fiber endface, then grinding a pair of wedge planes on the conical-shaped fiber endface, and finally through heating in a fusing splicer to form a good elliptical microlens endface. The coupling efficiency of 84% for CWSFM has been demonstrated. The fabrication of QPSFM requires five-step grinding processes. The range of grinding offset is 0.5~3.0£gm, and the average of grinding offset is 1.5£gm. The fabrication yield of QPSFM is low due to the large grinding offset. The fabrication of CWSFM requires only three-step grinding processes. The range of grinding offset is 0.3~1.5£gm, the average of grinding offset is 0.8£gm. The fabrication yield of CWSFM is high due to the small grinding offset. The fabrication yield is about 60% for 70% coupling efficiency; whereas the fabrication yield becomes 96% for 60% coupling efficiency. The laser-to-SMFs coupling of the fiber microlens was modeled based on the diffraction theory. The coupling efficiency, the tolerance of alignment, and the tolerance of fiber microlens offset were calculated according to this model. There is a good agreement between the simulation and the experiment values. In this study, two new scheme of fiber microlenses of the QPSFM and CWSFM with high coupling efficiency have been demonstrated. The CWSFM structure has the benefits of simple process and high yield that is suitable for use in commercial high power laser module.

A new scheme of asymmetric elliptic-cone-shaped microlens (AECSM) employing a single-step fabrication technique for efficient coupling between the high-power 980nm laser diodes and the single-mode fibers is proposed. The asymmetric elliptic-cone-shaped fiber endface (AECSFE) was fabricated by a single-step grinding and polishing a cleaved fiber by applying a periodically variable torque on the fiber ferrule to change the grinding pressure. The periodically variable torque was made by an eccentric mass with a constant rotation speed double that of the fiber. After the AECSFE was formed, an AECSM was obtained by heating the fiber tip in a fusing splicer. In comparison with the previous works on asymmetric fiber microlenses fabricated by the multi-step processes with complicated fabrication, the advantages of the AECSM structure for achieving high coupling are a single-step fabrication, a reproducible process, and a high-yield output. In this study, we demonstrated that the average grinding offset of the AECSM structure for 30 measurements was about 0.4 £gm, the average coupling efficiency was 71%, and the maximum of the measured coupling efficiency was 83%. The yield of the AECSM for coupling efficiency over 70% was 47%, for coupling efficiency over 60% was almost 100%.

Abstract Optical fiber communications have been become one of the most popular researches since 1970s. In this field, there are many studies on the coupling between semiconductor lasers and fibers and many conclusions are demonstrated. In this thesis we build a 2-D numerical model to simulate energy coupling between laser diodes (LDs) and tapered optical fibers. Our model is based on the spectral domain integral equation (SDIE) formulation which is derived from Maxwell equations and the principle of mode matching. Through this numerical model we will be able to show the field distribution in LD waveguide junctions. We may also use this tool to study the coupling parameters such as the separation distance and tapered fiber geometry.

Abstract We propose a new scheme of lensed fiber employing a quadrangular-pyramid-shaped fiber endface (QPSFE) for the coupling high-power 980nm laser diodes and single-mode fibers. The quadrangular-pyramid-shaped fiber was accomplished by first grinding and polishing a flat surface to the center of fiber at the desired inclination angle of £c, rotating the fiber to £p and polishing to the center of fiber, repeating the same process on the other sides of the fiber by rotating the fiber to £k-£p and £p. Then the QPSFE was fabricated by heating the tip of quadrangular-pyramid-shaped fiber in a fusing splicer to form an elliptical microlens endface. A coupling efficiency of 85% has been demonstrated. This higher coupling efficiency of the QPSFE lensed fiber is attributed to the better matching of the elliptical Gaussian field distribution between the laser source and the fiber.

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The mechanism of carbon coupling reactions is traditionally represented in a very broad schematic. This thesis seeks to explore the mechanism of these reactions by focusing on Heck olefination. The Heck reaction has become a powerful tool in synthetic labs but the mechanism of this reaction has remained a topic of debate since the reaction's discovery. The catalytic cycle that has come to be accepted, while accurate in its own right, is not nearly as detailed as the complexity of the various stages of the Heck reaction suggest it should be. This study seeks to elucidate the nature of the oxidative addition of aryl halide to a palladium catalyst using a ligand that has been shown to have high activity in facilitating oxidative addition of aryl chlorides and bromides in other coupling reactions. This information is then compared to other studies in the field so that conclusions can be drawn about the oxidative addition. Also, selectivity studies seek to determine the nature of the migratory insertion of an olefin into the Pd-Ar bond. Again, comparison of results obtained in this study are compared to previous results so that a more definitive conclusion can be drawn about the oxidative addition.