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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Development of Automatic Coupling Alignment System

Wang, Jhih-Min 13 October 2003 (has links)
The most complicated and important step in optical packaging is coupling alignment. It is very difficult to handle too many parameters at the same time during the coupling alignment process. Most of the parameters are neglected in coupling alignment process, especially the parameters of angles. According to the analysis, we found that the misalignment of angles do not have influence on the position of highest coupling efficiency in XY plane. A 2+2 freedom searching method has been developed to reach the four axis coupling alignment. An automatic coupling alignment system has been carried out. And it can reach higher coupling efficiency and faster coupling alignment process.
22

Synthetic Studies of Phenanthridines

Lin, Chao-hung 03 August 2005 (has links)
none
23

A study on single mode fiber coupling to hybrid antiresonant reflection optical waveguide

Lee, Kuan-Mo 16 June 2000 (has links)
Abstract The work presented in this thesis is intend to develop the required technologies for fabrication optical interconnection between a single mode fiber (SMF) and a hybrid antiresonant reflection optical waveguide(ARROW). In addition, the coupling characteristic between the SMF and ARROW are theoretically investigated. The fabrication of the optical interconnection includes three major techniques: fabrication of hybrid ARROW waveguide, V groove formation and U groove deep etching. The ARROW waveguide centered at 1.3mm was fabrication using semiconductor process technologies. Propagation losses of the device as low as 0.6dB/cm for TE polarized and 2.55dB/cm for TM were obtained. Anisotropic etching of Si-V grooves were formed using EDP solution, and room temperature sputtered Ta2O5 was used as the etch mask. At a etching temperature of 1200C, the under cut is 1.6mm. In order to increase the coupling efficiencies, we employed the U groove deep etching to reduce the distance from SMF to ARROW . The trenches with a depth 58mm were etched with SF6/O2 dry etching. Based on our calculation, the coupling efficiency as high as 90% can be obtained when the hybrid ARROW has a core thickness and a waveguide width of 12mm. The 3-dB alignment tolerance in X and Y directions between the SMF and ARROW are ¡Ó3.6mm and¡Ó3.7mm respectively.
24

Strategies for detecting poor coupling in an OBS experiment

Putro, Fitrix Primantoro 15 November 2004 (has links)
We present a method for detecting and correcting poor coupling in an Ocean Bottom Seismic (OBS) experiment. The basic idea of our method is that the normal component (with respect to the seafloor) of particle velocity is continuous at the water-solid interface. A comparison of the normal component of particle velocity just above and below the seafloor allows us to assess poor coupling. In other words, our method for detecting poor coupling consists of analyzing vertical particle velocities measured just above and below the seafloor. The normal component of particle velocity above the water is measured using either a vertical receiver array or a vertical source array (dipole source), whereas the normal component of particle velocity below the water is directly measured in this OBS experiment. In general, the quantities recorded in the OBS experiment are vertical and horizontal components of particle velocity, but continuity of the boundary is based on the normal component of particle velocity being oriented perpendicularly to the seafloor. For a flat seafloor, the vertical component of particle velocity values just above and below the seafloor must be almost equal according to the continuity condition at the water-solid boundary. However, for a dipping seafloor this is not the case. We have established that we can differentiate a poor coupling effect from a dipping-seafloor effect by using the vertical component of particle velocity. We have tested our method on real (Eugene Island) data and synthetic (finite-difference) data. For finite-difference synthetics, we have used a grid spacing 0.25 meters to properly simulate the water-solid interface. By examining the uniformity (with respect to offset) of cross-correlation between the vertical component of particle velocity just above and below the seafloor, we were able to detect poor coupling and to differentiate it with any dipping effect at the seafloor. The energy of data just above and below the seafloor were also used for detecting poor coupling and for differentiating it from dipping-seafloor effect.
25

The effects of torsional-lateral coupling on the dynamics of a gear coupled rotor

Emery, Michael Aaron 25 April 2007 (has links)
This thesis focuses on the torsional-lateral interactions seen in gear coupled rotors. Of particular interest are cases where the torsional stiffness parameters affect the lateral critical speeds and where lateral stiffness and damping parameters affect torsional critical speeds and amplitudes. A common procedure for critical speed calculations has been to solve lateral and torsional systems separately. This procedure is tested through an eigenvalue analysis. It is shown in this thesis, however, that torsional-lateral interactions play major roles in each other's critical speeds. Some research has seemingly uncoupled two lateral degrees of freedom from the gear system by choosing bearing forces and a coordinate system pointing along the line of action and normal to the line of action. This simplification method has been tested for cases when the lateral bearing stiffness becomes asymmetric. The force generated by a rotating imbalance also creates a variable moment arm as the center of mass rotates about the geometric center of the gear. This variable moment arm is commonly neglected, but is included in the last case study and its effects are displayed in the results section of this thesis.
26

Effect of visual feedback on learning of a 2:1 isometric bimanual coordination pattern

Wilson, Christopher Ryan 16 August 2012 (has links)
The primary purpose of this study was to examine if the coupling effect could be overcome in a bimanual isometric tracking task, using methods similar to those of the Kovacs et al. team in previous bimanual kinematic research. Thirty right-handed participants, with a mean age 22.5 (SD 3.5) years, free from any neurological disorder or physical ailment, were randomly assigned to one of three groups that differed in percent of feedback provided during the practice trials (100%, 50% or 0%). The participants then performed a bimanual isometric manipulation tracking task that was a 2:1 rhythm (backwards C shape) scaled to 30% maximum voluntary contraction (MVC). Participants performed five blocks of five trials with the feedback schedule assigned to their group, rested for 30 minutes, then performed a retention task. Significant differences (p<.05) in Root Mean Square Error (RMSE) occurred between the 100% group and both the 50% and 0% groups during the practice blocks. Significant differences (p<.05) also occurred between the 50% group and the 100% and 0% group for the first four practice blocks. Though differences occurred between the groups during the practice trials, no differences occurred between the groups during the retention block. These findings support the position that the coupling effect in bimanual isometric manipulation tasks is very strong and cannot be as easily overcome as it is in kinematic bimanual task. This may be due to the feedback systems used in isometric conditions versus kinematic tasks (i.e. force and pressure sensation vs. position and motion proprioception). / text
27

A new, improved precatalyst for Suzuki-Miyaura cross-coupling reactions

NORTON, DANIELLE 23 July 2009 (has links)
Carbon-carbon bond formation is one of the most important reactions in organic chemistry, and the Suzuki-Miyaura cross-coupling reaction has become a forerunner in this area. Considerable research has been directed at the mechanistic aspects and synthetic utility of the reaction; however, little attention has been given to the formation of the putative PdL2 catalysts. Due to their high reactivities, these catalysts are typically difficult to store and therefore are often generated in situ in unknown yields and at unknown rates via any number of available palladium precursors. This thesis describes research directed towards determining the optimum conditions to quantitatively generate compounds of the type Pd(0)Ln (L = PMePh2, PPh3, PCy3, PMeBut2, PBut3, dppe, dppp, dppf) from Pd(h5-C5H5)(h3-1-Ph-C3H4). Pd(h5-C5H5)(h3-1-Ph-C3H4) has been found to be a superior precursor for synthesizing catalytically active PdL2 compounds due to its ease in handling and reactivity with tertiary phosphines. Furthermore, investigations into the role of water in the transmetallation step of the Suzuki-Miyaura reaction are presented. The research indicates that water is necessary to effect the transmetallation step when coupling [NBu4][PhBF3] with 4-bromotoluene in toluene; however, the amount of water above one equivalent has no significant effect on the rate or yield of the reaction. / Thesis (Master, Chemistry) -- Queen's University, 2009-07-23 12:57:10.248
28

INVESTIGATIONS INTO CROSS-COUPLING OF SECONDARY ORGANOBORONIC ESTERS

Holland, Amy Marie 23 September 2010 (has links)
Until recently, secondary organoboronic esters were not viable substrates in the Suzuki-Miyaura cross-coupling reaction; however under recently reported conditions from the Crudden group1, which includes the addition of silver oxide to a palladium/phosphine catalyst system, this coupling can now be achieved. This thesis centres on optimizing the reaction conditions and expanding the substrate scope of this difficult but important secondary coupling. Optimal coupling conditions, for the example reaction of 4-iodoacetophenone and (R)-pinacol(1-phenylethyl)boronate, were found to be 8 mol% Pd(PPh3)4, 32 mol% PPh3, 1.5 eq. Ag2O and 1.5 eq. K2CO3 in DME at 85 °C for 24 h. This gave the desired coupling product in 64 % yield with 99.5 % retention of stereochemistry. Using this set of conditions, an array of aryl iodides were screened. The reaction conditions could not be extended to triflate or diazonium electrophiles. Amide functionality is important in many natural products and pharmaceuticals. The extension of reaction conditions to amides possessing boronic ester functionality at the β-position was attempted; however, no conditions could be determined to generate the cross-coupling product. An α-substitution pattern would better exemplify the benzylic positioning found to work for the original substrates. Attempts to synthesize the α-substituted amide were made without success. The optimal reaction conditions gave hope for differentiation between an aryl and a secondary aliphatic boronic ester. Using an aryl triflate to couple the aryl position and an aryl iodide to couple the aliphatic position, conditions for selective coupling were determined and applied to a one-pot procedure. / Thesis (Master, Chemistry) -- Queen's University, 2010-09-22 23:33:10.984
29

Perturbations of respiratory locomotor entrainment in experienced runners: the influence of vocalization and fluid ingestion.

McMurray, Robert Michael 13 January 2010 (has links)
The exact mechanism underlying the coupling between breathing and locomotion is still unknown; the visceral piston theory is a putative mechanism but has gone largely untested. The study assessed the visceral piston theory by examining the effect of perturbations (vocalization and fluid ingestion) on the coupling of breathing and locomotion. 10 experienced runners performed a speed running trial (6.5 to 8.0 mph in 0.5 mph increments), followed by a vocalization trial and a fluid ingestion trial at their preferred running speed while on a treadmill. Continuous recordings of respiratory flow and single leg, tibial acceleration was acquired (500 Hz). Rating of perceived exertion for breathing (RPEB), effort (RPEE), stitch (RPES) and heart rate (HR) were also recorded during the trials. The magnitude (SIFTMAG) and timing (SIFTT) of step induced flow transients were determined, along with the breath cycle duration (BCD) and respiratory locomotor entrainment (RLE) ratios. RPEB, and HR showed an increase in all three trials, RPEE showed an increase in the speed trial and the fluid ingestion trial but not the vocalization trial. SIFTMAG had a significant increase post perturbation (vocalization and fluid ingestion). SIFTT increased significantly post fluid ingestion but not after the vocalization perturbation. RLE ratios were increased post fluid ingestion but not post vocalization perturbation, however BCD was reduced after vocalization trials. The SIFTMAG was increased as result of perturbations corresponding to respiratory flow suppression which could lead to increased respiratory load. A shift in timing after fluid ingestion is consistent with an increased mass of a visceral spring mass system. Four of ten runners experienced a stitch after fluid ingestion. These findings strongly support the visceral piston theory of RLE, and this becomes a plausible mechanism for the induction of a stitch in the side.
30

Perturbations of respiratory locomotor entrainment in experienced runners: the influence of vocalization and fluid ingestion.

McMurray, Robert Michael 13 January 2010 (has links)
The exact mechanism underlying the coupling between breathing and locomotion is still unknown; the visceral piston theory is a putative mechanism but has gone largely untested. The study assessed the visceral piston theory by examining the effect of perturbations (vocalization and fluid ingestion) on the coupling of breathing and locomotion. 10 experienced runners performed a speed running trial (6.5 to 8.0 mph in 0.5 mph increments), followed by a vocalization trial and a fluid ingestion trial at their preferred running speed while on a treadmill. Continuous recordings of respiratory flow and single leg, tibial acceleration was acquired (500 Hz). Rating of perceived exertion for breathing (RPEB), effort (RPEE), stitch (RPES) and heart rate (HR) were also recorded during the trials. The magnitude (SIFTMAG) and timing (SIFTT) of step induced flow transients were determined, along with the breath cycle duration (BCD) and respiratory locomotor entrainment (RLE) ratios. RPEB, and HR showed an increase in all three trials, RPEE showed an increase in the speed trial and the fluid ingestion trial but not the vocalization trial. SIFTMAG had a significant increase post perturbation (vocalization and fluid ingestion). SIFTT increased significantly post fluid ingestion but not after the vocalization perturbation. RLE ratios were increased post fluid ingestion but not post vocalization perturbation, however BCD was reduced after vocalization trials. The SIFTMAG was increased as result of perturbations corresponding to respiratory flow suppression which could lead to increased respiratory load. A shift in timing after fluid ingestion is consistent with an increased mass of a visceral spring mass system. Four of ten runners experienced a stitch after fluid ingestion. These findings strongly support the visceral piston theory of RLE, and this becomes a plausible mechanism for the induction of a stitch in the side.

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