Dissertations / Theses: 'Asymmetrical Designs'

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Abel, Heiko. "Frigate defense effectiveness in asymmetrical green water engagements." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://handle.dtic.mil/100.2/ADA508855.

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Thesis (M.S. in Modeling, Virtual Environments and Simulation (MOVES))--Naval Postgraduate School, September 2009.
Thesis Advisor(s): Sanchez, Paul J. ; Second Reader: Kline, Jeffrey E. "September 2009." Author(s) subject terms: Agent Based Simulation, Asymmetric Warfare, Data Farming, Design of Experiments, Evolving Design, MANA, Modeling and Simulation, Naval Swarm Defense, Robust Design, Regression Analysis, Simulation Experiments and Efficient Design Center, Taguchi Method Description based on title screen as viewed on November 03, 2009. DTIC Descriptor (s): Frigates, Theater Level Operations, Defense Systems, Experimental Design, Confined Environments, Asymmetry, Statistical Analysis, Sea Water, Small Ships, Threats, Survivability, Weapons, Theses DTIC Identifier (s): SSTR (Stability Security Transition and Reconstruction), Asymmetric Warfare, Mana Includes bibliographical references (p. 125-132). Also available in print.

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Aney, Madhav Shrihari. "Institutional design under asymmetric information." Thesis, London School of Economics and Political Science (University of London), 2009. http://etheses.lse.ac.uk/3001/.

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This thesis contributes to the literature that seeks to understand institutions. In particular the aim of this thesis is to shed light on how certain institutions arise in society as a result of collective choice, how in turn they shape behaviour of agents, and finally what their welfare properties are. These questions are tackled using the methodology of microeconomic theory where agent preferences, the state of technology, and the informational environment are taken as exogenous. In particular it is argued that the existence of different constraints on the informational environment can give rise to a rich theory of institutions that can explain why inefficient and seemingly inefficient institutions arise in a second best world. The first chapter of this thesis is concerned with the incidence of costly dispute resolution in society. The question of why agents fail to revolve disputes costlessly is tackled. This contributes to the positive theory of individual behaviour given the existence of certain institutions. The second chapter of this thesis tackles the question of why the judiciary is characterised by certain inherently costly attributes. This contributes to the normative theory of institutional choice. The last chapter deals with the positive question of how institutions are chosen. A model is presented where the political alignments in a society are endogenously generated and the effect of varying the informational environment on these alignments is analysed. These three chapters collectively contribute to the incipient theory of institutions that comprises of two elements; first where the existence of institutional structure arises as an equilibrium interplay between individual choices and technological and informational constraints, and second where conversely, individual games are shaped by the structure of existing institutions.

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Sarvghad-Moghadam, Abdoreza. "Seismic torsional response of asymmetrical multi-storey frame buildings." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/NQ42874.pdf.

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Botha, Ruan. "Design and characterization of asymmetrical porous nickel membranes / Ruan Botha." Thesis, North-West University, 2006. http://hdl.handle.net/10394/14.

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As an alternative to organic membranes, ceramic membranes are suitable for the chemical industry due to their intrinsic thermal, chemical and mechanical stability. The centrifugal dispositioning technique has the advantage that it produces membranes that are asymmetrical with a smooth inner surface. In this study, nickel powders were used in the place of regular a-alumina powders to produce an asymmetrical porous membrane, and to determine its characteristics. Sub-micron nickel powders can be produced by the hydrothermal reduction of a nickel salt with hydrazine. The particles obtained are of the correct size and size distribution and can be processed to be suitable for centrifugal dispositioning. Dispersants like polyacrylamide-codiallyldimethylammoniumchloride, polyvinylpirrolidone (PVP) and ammonium-polymetacrylate (APMA) were investigated to determine their ability to stabilize Ni powder in an aqueous dispersion. Nickel powder manufactured by the hydrothermal reduction of a nickel salt with hydrazine were moulded into a tubular membrane by means or the centrifugal dispitioning technique. A stable dispersion was made with PAAco with little agglomeration or segregation. The membranes were successfully removed from the stainless steel moulds without breakage of the membrane. The greencasted membranes obtained were sintered without membrane failure, where after they were subjected to numerous tests to determine their characteristics. SEM photographs were taken from the Inner surface and cross-sections to determine the morphology of the membranes. It was demonstrated that a change in the crystal phase occurred at 1200"C, changing the morphology as well as the membrane characteristics. The nickel membrane shrinkage during the sintering experiments was found to increase linearly. It was shown with mercury intrusion that the bimodal pore size distribution of the membranes decreased with increasing sintering temperature, while larger pores were exchanged for smatter pores. It was found that water permeation varied from 5 to 69 L.m-2.h-1.bar-1, depending on the sintering temperature (950°C to 1250°C) of the membrane. The water permeation decreased linearly with increasing sintering temperature.
Thesis (M.Sc. (Pharmaceutical Chemistry))--North-West University, Potchefstroom Campus, 2007.

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Castillo, Rolando. "Seismic design of asymmetric ductile systems." Thesis, University of Canterbury. Department of Civil Engineering, 2004. http://hdl.handle.net/10092/5055.

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The research promotes a better understanding of the response of torsionally unrestrained and restrained ductile systems by examining the mechanism developed during the torsional response of systems as they are affected by the dynamic actions of the translational and rotational mass. A simple but effective design strategy for the seismic design of torsionally asymmetric systems is suggested based on the estimate of the system displacement ductility capacity and the distribution of the estimated system strength to its elements. The strength eccentricity is considered the main parameter to influence the ductile response of asymmetric systems. The possible success of the design strategy to limit displacement demands of the elements to less than their displacement ductility capacity, for zero and increasing strength eccentricities, was examined against the effects of key parameters expected to influence response. These parameters are: strength eccentricity and the associated increase of system strength, mass eccentricity, ratio of radii of gyration of strength and mass, reduced system displacement ductility capacity, transverse elements and their degree of torsional restraint, the ratio of element nominal yield displacement, i.e., α=Δye2/Δye1. and associated stiffness eccentricity, uncoupled translational period, consideration of different earthquake records and their direction of application. Elements are modelled with a realistic relationship between element strength, stiffness and nominal yield displacement. The stiffness is strength dependant and the nominal yield displacement is a geometric and material property independent of strength. The centre of strength and stiffness are, therefore, not independent parameters. This research focuses on analytical studies of torsionally unrestrained and restrained single-mass asymmetric systems. Single, two and multi-element systems were examined. An experimental programme was also undertaken on single-mass models to verify some of the analytical findings. The findings suggest that the suggested design strategy is successful in limiting the displacement demands on elements to less than their displacement capacity for zero and increasing strength eccentricities. No differentiation is required between systems having or not having mass eccentricity. The proposed design strategy is slightly different for torsionally unrestrained and restrained systems. It promises to be straightforward, rational and in terms of design efforts most user friendly.

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James, Samantha N. "Design and Development of Asymmetric Organocatalysts." Thesis, Griffith University, 2014. http://hdl.handle.net/10072/367034.

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This thesis describes the design and synthesis of a new class of hydrogen bonding organocatalysts. After various synthetic strategies were investigated, a convenient two-step process, involving an amide coupling followed by borane reduction of the resulting N-acylsulfonamide, resulted in the formation of the targeted racemic 1,5-bis-sulfonamides. This synthesis also provided access to a second series of potential organocatalysts, the N-acylsulfonamides. The catalytic ability of both libraries of racemic compounds was tested in Friedel-Crafts type reactions of N-methylindole with ethyl glyoxylate and p-nitrostyrene. Following on from this work, a small number of N-acylsulfonamides were synthesised in enantiomerically enriched form, after resolution of the starting material trans-1,3-cyclohexanedicarboxylic acid using strychnine. Testing of the enantiopure N-acylsulfonamides showed that they were able to promote the Friedel-Crafts type reaction between N-methylindole and P-nitrostyrene, in good yields but poor enantioselectivities. A second group of catalysts were synthesised based on the TAD DOL class of compounds. Attempts to form his-sulfonamide TADDOL derivatives were unsuccessful, with only mono-sulfonamides being isolated, possibly due to a stabilising intramolecular hydrogen bond present in the mono-sulfonamides. A p-tolyl N-acylsulfonamide TADDOL derivative was also synthesised. The mono sulfonamide and N-acylsulfonamide TADDOL derivatives did not effectively catalyse the Friedel-Crafts type reaction between N-methylindole and P nitrostyrene. The TADDOL derivatives catalysed the model reaction between N methylindole and ethyl glyoxylate with low to moderate efficiency.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
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Bremberg, Ulf. "Asymmetric catalysis : ligand design and microwave acceleration." Doctoral thesis, KTH, Chemistry, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2962.

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This thesis deals partly with the design and synthesis ofligands for use in asymmetric catalysis, and partly with theapplication of microwave heating on metal-based asymmetriccatalytic reactions.

Enantiomerically pure pyridyl alcohols and bipyridylalcohols were synthesized from the chiral pool for future usein asymmetric catalysis. Lithiated pyridines were reacted withseveral chiral electrophiles, yielding diastereomeric mixturesthat could be separated without the use of resolutiontechniques.

New pyridino- and quinolinooxazolines were synthesized andtested in palladium-catalyzed asymmetric allylation using1,3-diphenyl-2-propenyl acetate and dimethyl malonate. Theconformational preferences of the ligands in palladiumcomplexes were studied with crystallography, 2D-NMR techniquesand DFT calculations. Conclusions about how the chirality wastransferred from the ligand to the substrate could be drawnfrom the conformational analysis.

The effect of heating Pd- and Mo-catalyzed asymmetricallylic substitution reactions was investigated with oil bathheating and microwave irradiation. With a few exceptions,ligands with high room temperature selectivity were shown toretain their selectivity on heating. Reaction rates, catalyststability and product selectivities of microwave-heatedreactions were compared with those of reactions performed inoil bath.

Palladium-catalyzed asymmetric allylation was studied withseveral ligand types, allylic substrates and nucleophiles. Someof the experimental procedures had to be adapted to microwaveheating conditions.

The procedure for asymmetric allylation catalyzed bybispyridylamide molybdenum complexes was developed into aone-pot microwave-mediated reaction. With microwaves, Mo(CO)₆could be used as an easily-handled metal sourceand inert conditions could be omitted. Derivatives of thebispyridylamide ligandswere synthesized and tested withmolybdenum as catalysts to investigate the effects ofsubstituents on the pyridine ring.

Keywords: ligand, asymmetric catalysis, pyridylalcohols, oxazolines, conformational study, Pd-allyl, fastchemistry, microwave chemistry, Mo-allyl, bispyridylamides.

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Hallman, Kristina. "Asymmetric Catalysis : Ligand Design and Conformational Studies." Doctoral thesis, KTH, Chemistry, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3275.

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This thesis deals with the design of ligands for efficientasymmetric catalysis and studies of the conformation of theligands in the catalytically active complexes. All ligandsdeveloped contain chiral oxazoline heterocycles.

The conformations of hydroxy- and methoxy-substitutedpyridinooxazolines and bis(oxazolines) during Pd-catalysedallylic alkylations were investigated using crystallography,2D-NMR techniques and DFT calculations. A stabilising OH-Pdinteraction was discovered which might explain the differencein reactivity between the hydroxy- and methoxy-containingligands. The conformational change in the ligands due to thisinteraction may explain the different selectivities observed inthe catalytic reaction.

Polymer-bound pyridinooxazolines and bis(oxazolines) weresynthesised and employed in Pd-catalysed allylic alkylationswith results similar to those of monomeric analogues;enantioselectivities up to 95% were obtained. One polymer-boundligand could be re-used several times after removal of Pd(0).The polymer-bound bis(oxazoline) was also used in Zn-catalysedDiels-Alder reactions, but the heterogenised catalyst gavelower selectivities than a monomeric analogue.

A series of chiral dendron-containing pyridinooxazolines andbis(oxazolines) were synthesised and evaluated in Pd-catalysedallylic alkylations. The dendrons did not seem to have anyinfluence on the selectivity and little influence on the yieldwhen introduced in the pyridinooxazoline ligands. In thebis(oxazoline) series lower generation dendrimers had a postiveon the selectivity, but the selectivity and the activitydecreased with increasing generation.

Crown ether-containing ligands were investigated inpalladium-catalysed alkylations. No evidence of a possibleinteraction between the metal in the crown ether and thenucleophile was discovered.

A new type of catalyst, an oxazoline-containing palladacyclewas found to be very active in oxidations of secondary alcoholsto the corresponding aldehydes or ketones. The reactions wereperformed with air as the re-oxidant. Therefore, this is anenviromentally friendly oxidation method.

Keywords:asymmetric catalysis, chiral ligand,oxazolines, conformational study, allylic substitution,polymer-bound ligands, dendritic ligands, crown ether,oxidations, palladacycle.

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Tong, Ka Pui. "Design of new ligands for asymmetric catalysis /." View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202003%20TONG.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 107-111). Also available in electronic version. Access restricted to campus users.

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Nixon, Tracy Dawn. "Catalyst design for the asymmetric phospho-aldol reaction." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424504.

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Wu, Huafeng. "Design and synthesis of novel chiral arsines for asymmetric wittig reactions and Pd-catalyzed asymmetric allylic alkylation and asymmetric heck reactions /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202004%20WU.

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Bommana, Srinivasarao. "Design of a Miniaturised Asymmetrical Power Splitter Using Low Impedance Artifical Transmission Lines." Thesis, University of Canterbury. Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/5030.

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Transmission lines are the basic building blocks of any RF and microwave circuits. The width of a microstripline increases as the characteristic impedance is lowered for a given substrate. Wide microstriplines suffer from spurious and higher order modes at higher frequencies and may not behave as transmission lines. This means the lower limitation for a realisable microstripline is about 10 ohm. In this project microstriplines with characteristic impedances of 7 ohm and 25 ohm at a frequency of 2 GHz were designed and realised using the artificial transmission lines (ATL) concept. Detailed theoretical analysis and circuit and EM simulations were used for the design and implementation of the ATLs. Taconic TLY-5 substrate was used for the PCB fabrication. The substrate thickness was 0.787 mm and the dielectric constant was 2.2. The measured results were de-embedded and compared with the simulation results. The detailed procedure of modelling and de-embedding of an SMA connector is also given. The 25 ohm ATL was realised using microstriplines only, where as microstriplines and chip capacitors were used in realising the 7 ohm ATL. The measured characteristic impedance of the 25 ohm ATL was 24.4 ohm and the measured electrical length of the 25 ohm ATL was 180 degrees at 2.1 GHz. To realise a 25 ohm ATL with 90 degrees electrical length, the half-wavelength 25 ohm ATL geometry was cut into half and one of the half geometries was EM simulated. The EM simulated electrical length of the 25 ohm ATL was 90 degrees at 1.9 GHz. The measured characteristic impedance of the 7 ohm ATL was 5.9 ohm and the measured electrical length of the 7 ohm ATL was 90 degrees at 1.8 GHz. The main advantage of an ATL is size reduction. A 25 ohm meandered microstrip line (substrate thickness = 0.787 mm, dielectric constant = 2.2) with 180 degrees electrical length at 2 GHz has a size of 34 mm x 15 mm. The 25 ohm ATL with 180 degrees electrical length at 2.1 GHz was realised in a size of 22 mm x 19 mm. The design of the 25 Ω ATL resulted in 18 percent reduction in area compared to the meander line. A 7 ohm conventional microstripline (substrate thickness = 0.787 mm, dielectric constant = 2.2) with 90 degrees electrical length at 1.8 GHz has a size of about 28 mm x 27 mm. The 7 ohm ATL with 90 degrees electrical length at 1.8 GHz was realised in a size of 7 mm x 8.4 mm which is only 8 percent of the conventional 7 ohm microstripline area. In general, a spacing of 3h where h is the substrate thickness is required between the adjacent microstriplines. In this project detailed investigations were done to see if the spacing can be reduced without any detrimental coupling affects and a spacing of 0.6 mm was used. This reduction in spacing has resulted in reduced size of the ATL. For an asymmetrical power splitter based on the Wilkinson topology, the power splitter output power split ratio depends on the square of the characteristic impedances of the quarter-wavelength arms. In this project an asymmetrical power splitter was designed and realised using a 7 ohm ATL and a 25 ohm ATL as the quarter-wavelength arms. The desired centre frequency of the power splitter was 2 GHz and the measured centre frequency was 1.6 GHz. At the centre frequency the phase difference between the output ports of the power splitter will be zero. The simulated power split ratio was 10.1 dB and the measured power split ratio was 13 dB. The power split ratio calculated using the measured characteristic impedances of the ATLs (24.4 ohm and 5.9 ohm) will be 12.4 dB which is very close to the measured power split ratio.

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Raskatov, Jevgenij A. "Rational design of chiral ionic recognition for asymmetric catalysis." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497082.

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Smith, Robin C. "The design, fabrication and measurement of asymmetric LDD transistors." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12141.

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This thesis describes the design fabrication, measurement and analysis of asymmetric lightly doped drain transistors. The transistors were fabricated so that adjacent transistors in columns were of a slightly different but determinable asymmetry. This approach has been termed the progressional offset technique. The progressional offset technique has the advantage in that it can be used to fabricate transistors with different lightly doped drain lengths the same wafer. The resulting devices consist of a range of transistors with different degrees of asymmetry which can be quantified. The thesis shows that the asymmetry of these devices can be determined by simple electrical measurements. The progressional offset technique was used to show that an asymmetric lightly doped drain implant can have a large effect on the electrical properties of the devices. This occurs when the lightly doped drain implant is shadowed by the polysilicon gate during the angled implantation which is routinely used by industry. The progressional offset technique is a useful tool for analysing the effects of asymmetry on LDD transistors. It also has been shown to produce transistors with different LDD lengths on a single wafer.

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Cobzaru, Cecilia. "Asymmetric metallocene catalysts: design of ultrahigh molecular weight polypropylene plastomers." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-55721.

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Yamaguchi, Yukako. "Molecular Design of Bifunctional Amino Sulfonamides for Asymmetric Enamine Catalysis." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124447.

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Doughty, Jeffrey Jon. "Symmetric Near-Field Probe Design and Comparison to Asymmetric Probes." PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/390.

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Tip Enhanced Near-field Optical Microscopy (TENOM) is a method for optically imaging at resolutions far below the diffraction limit. This technique requires optical nano-probes with very specialized geometries, in order to obtain large, localized enhancements of the electromagnetic field, which is the driver behind this imaging method. Traditional methods for the fabrication of these nano-probes involve electrochemical etching and subsequent FIB milling. However, this milling process is non-trivial, requiring multiple cuts on each probe. This requires multiple rotations of the probe within the FIB system, which may not be possible in all systems, meaning the sample must be removed from vacuum, rotated by hand and placed back under vacuum. This is time consuming and costly and presents a problem with reproducibility. The method presented here is to replace multiple cuts from a side profile with a small number of cuts from a top down profile. This method uses the inherent imaging characteristics of the FIB, by assigning beam dwell times to specific locations on the sample, through the use of bitmap images. These bitmaps are placed over the sample while imaging and provide a lookup table for the beam while milling. These images are grayscale with the color of each pixel representing the dwell time at that pixel. This technique, combined with grayscale gradients, can provide probes with a symmetric geometry, making the system polarization independent.

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Wilkinson, Sean. "Simplified analysis of asymmetric buildings subjected to earthquakes." Thesis, Queensland University of Technology, 1997.

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Tarar, Mohsin Mumtaz. "Design and Implementation of as Asymmetric Doherty Power Amplifier at 2.65 GHz in GaN HEMT Technology." Thesis, Linköpings universitet, Elektroniska komponenter, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-75976.

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Power amplifiers are an indispensible part of the wireless communication systems. Conventional PAs provide peak efficiency at peak output power which is obtained at a certain fixed optimum resistance. These kind of amplifiers are normally called switched-mode power amplifiers (SMPAs) and are used for constant envelope signals. However, there is low efficiency at low output power which is the linear operation of a PA and is used for the amplification of non-constant envelope signals. For an optimum PA design, linearity and efficiency are the requirements. There are efficiency enhancement techniques and Doherty architecture is one such approach. Classical Doherty (symmetric) approach entertains the signals that have peak to average power ratio (PAPR) of 6 dB. Applications like Long Term Evolution (LTE) having high PAPR of nearly 9 dB demand efficiency throughout the back-off range. Therefore the challenge is to design and implement an asymmetric Doherty power amplifier that ensures high efficiency in the back-off range greater than 6 dB. This work presents the design and implementation of an Asymmetric Doherty Power Amplifier (ADPA) for 12 dB back-off at 2.65 GHz in Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs) technology. The carrier and peaking amplifiers are biased in class-B and C mode of operations, respectively. A branchline coupler is used to divide the input signal equally to amplifiers input. A 10 W GaN HEMT transistor is used as an active device for both amplifiers. The design has been implemented with ideal transmission lines and then shifted to microstrip lines using 508 um substrate. The measurement results of the ADPA prototype, when drain of carrier and peaking devices are biased at 24 V and 28 V respectively, showed an input power back of (IPBO) of 9.68 dB with almost same power added efficiency (PAE) of 44% throughout the entire back-off range. The simulations are done with Agilent ADS and Momentum is used for Electromagnetic (EM) simulation.

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Carelli, Robert Beltri. "Use of an asymmetric propeller for unmanned underwater vehicles." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122609.

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Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019
Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, System Design and Management Program, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (page 83).
This thesis describes the development and execution of a test program to determine the suitability of an asymmetric propeller for unmanned underwater vehicles (UUV). The idea to utilize a single blade propeller had been pioneered in the past for aviation as an attempt to generate greater thrust, but was quickly abandoned. Recently, Woods Hole Oceanographic Institute reevaluated the concept for use on a UUV, but for two different objectives. The first was a possible improvement in propulsive efficiency. For UUVs meant to operate for long periods without recharging, any increase in propeller efficiency can result in more time on station. The second object was to allow for an alternate method of steering the UUV. By controlling the speed of the propeller through each revolution, the thrust at any given point can be controlled. This allows for a non-uniformly distributed thrust about the longitudinal axis of the UUV which can be used to steer the UUV. This thesis evaluated the efficiency of using such a propeller. This data was used to determine the suitability for UUVs and in which use cases an asymmetric propeller used for propulsion and steering. Due to issues during testing the control authority provided along a variety of speeds could not be determined for comparison to a traditional propeller and rudder configuration.
by Robert Beltri Carelli.
Nav. E.
S.M. in Engineering and Management
Nav.E. Massachusetts Institute of Technology, Department of Mechanical Engineering
S.M.inEngineeringandManagement Massachusetts Institute of Technology, System Design and Management Program

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Suresan, Abhishek. "Load Distribution Modeling of Asymmetric Involute Gear Pairs." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587635749289172.

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Hartikka, Antti. "Towards Rational Design of Asymmetric Catalyst for Organometallic and Organocatalytic Reactions." Doctoral thesis, Uppsala : University Library / Universitetsbiblioteket, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7905.

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Hedberg, Christian. "Design, Synthesis, Mechanistic Rationalization and Application of Asymmetric Transition-Metal Catalysts." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5740.

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Bennett, Malcolm William. "Design of new asymmetric copper(I)-catalysts for conjugate addition chemistry." Thesis, University of Hull, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310254.

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Topping, Chris Mark. "Design and synthesis of chiral ligands for copper catalysed asymmetric synthesis." Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301496.

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Yoshinaga, Yukako. "New Design of Bipyridine Ligands for Copper-Catalyzed Asymmetric Molecular Transformations." Kyoto University, 2020. http://hdl.handle.net/2433/253507.

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Wilkerson, Phillip D. "Synthesis of Chiral N-Heterocyclic Carbene Precursors and Key Intermediates for Catalytic Enantioselective Cyclizations of Conjugated Trienes." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/chemistry_theses/49.

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Cocatalyzed reactions using Brønsted acids and chiral N-heterocyclic carbenes to yield highly enantioselective products have been reported recently in many journals. The development of new chiral N-heterocyclic carbenes is a competitive field among synthetic chemist. In a recent study we found that conjugated trienes could be cyclized using Brønsted acids and chiral N-heterocyclic carbenes. The synthesis of novel chiral N-heterocyclic carbene precursors, and the precursors to novel conjugated trienes are reported herein.

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Liu, Zhihua. "THE DESIGN AND SYNTHESIS OF NOVEL UNNATURAL AMINO ACIDS AND THE DESIGN AND SYNTHESIS OF PEPTIDES & PEPTIDOMIMETICS CONTAINING UNNATURAL AMINO ACIDS FOR THE STUDY OF G-PROTEIN COUPLED RECEPTORS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/204274.

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Nature has gifted peptides as important modulators in the human body, but these types of molecules often have not been favored when we were looking for therapeutic agents. The poor bioavailability, fast degradation and until recent high manufacturing costs of some bioactive peptides lowered their potential usage in the health industry. Under these circumstances, unnatural amino acids were developed as indispensible tools providing enormous support to peptide science. By incorporating proper unnatural amino acids into a peptide or protein, we now can significantly improve peptide's or protein's half-life, cell permeability, bio-distribution, etc. In addition, their potency and receptor/acceptor selectivity could also be enhanced. Site-specific modifications of peptides and proteins under physiological conditions with the use of unnatural amino acids also have been made easier with the advance of biotechnology. Therefore, my research described in this dissertation contributes to the efforts in the development of novel unnatural amino acids. In particular, I have focused on novel methods in the synthesis of anti beta-functionalized gamma,delta-unsaturated amino acids. These amino acids have special interests in peptide chemistry: they can provide conformational constraints to the peptide 3D structures; the beta-functionalization allows the introduction of pharmaceutically interesting side chain groups; and the terminal double bond which is orthogonal to peptide synthesis provides access to further chemical modifications. Two general methodologies for the synthesis of both racemic and optically active anti beta-functionalized gamma,delta--unsaturated amino acids were developed by using the thio-Claisen rearrangement (TCR) reaction. Excellent diastereoselectivies and enantioselectivities were obtained when C2-symmetric chiral auxiliaries were selected to control the stereochemistry outcome. The mechanism and the scope of the TCR reaction were also studied, showing unique advantages in the preparation of these biological interesting amino acids.Another effort of developing angiotensin II type 1 (AT1) receptor biased peptide ligands is also documented in this dissertation. The AT1 receptor is a 7-transmembrane G-protein coupled receptor, which recent researches have shown could be activated through a beta-arrestins only, but G-protein independent, pathway. We synthesized 12 analogs of Sar1,Ile4,Ile8-AngII (SII), and tested them in biological assays, and obtained valuable information for further "perfect" biased ligands design.

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Saha, Shamik. "SSAGA: Streaming Multiprocessors (SMs) Sculpted for Asymmetric General Purpose Graphics Processing Unit (GPGPU) Applications." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5196.

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The evolution of the Graphics Processing Units (GPUs) over the last decade, has reinforced general purpose computing while sustaining a steady performance growth in graphics intensive applications. However, the immense performance improvement is generally associated with a steep rise in GPU power consumption. Consequently, GPUs are already close to the abominable power wall. With a massive popularity of the mobile devices running general-purpose GPU (GPGPU) applications, it is of utmost importance to ensure a high energy efficiency, while meeting the strict performance requirements. In this work, we demonstrate that, customizing a Streaming Multiprocessor (SM) of a GPU, at a lower frequency, is significantly more energy efficient, compared to employing Dynamic Voltage and Frequency Scaling (DVFS) on an SM, designed for a high frequency operation. Using a system level Computer Aided Design (CAD) technique, we propose SSAGA - Streaming Multiprocessors Sculpted for Asymmetric GPGPU Applications, an energy efficient GPU design paradigm. SSAGA creates architecturally identical SM cores, customized for different voltage-frequency domains.

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Mon, Quílez Ignacio. "Design, synthesis and application of supramolecular ligands in asymmetric hydrogenation and hydroformylation." Doctoral thesis, Universitat Rovira i Virgili, 2014. http://hdl.handle.net/10803/145772.

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En la present Tesi Doctoral s’han dissenyat i sintetitzat una família de lligands supramoleculars de tipus bis(fosfina) i una de tipus bis(fosfit) que combinen un lloc de coordinació de metalls de transició per a catàlisi i un altre de regulació, tipus cadena polioxietilènica, per a interaccions no covalents. El concepte de regulació ha estat provat en els catalitzadors de rodi derivats d’aquests lligands en hidroformilació i hidrogenació asimètrica de diferents alquens. Paràmetres com l’activitat catalítica i l’enantioselectivitat (i la regioselectivitaten el cas de la hidroformilació) han estat millorats amb l’adició d’espècies catiòniques. Aquests estudis han estan complementats amb estudis de coordinació i d’afinitat. En el marc d’aquesta Tesi Doctoral també es va desenvolupar un dels pocs exemples de receptors amb regulació distal per a àcids dicarboxílics.
In the present PhD Thesis, two families of supramolecular bis(phosphite) and bis(phosphine) ligands have been designed and synthesized. These ligands combine a catalytic site for enantioselective organometallic catalysis and a regulation site based on a polyoxyethylene chain for ion-dipole non-covalent interactions. The concept of regulation has been proven inrhodium-mediated asymmetric hydroformylation and hydrogenation reactions of different alkenes using catalysts derived from the ligands that incorporate a distal regulation site. Parameters such as catalyst activity and enantioselectivity (and regioselectivity for hydroformylation) were improved by thesimple addition of cationic species as regulating agents. Within this thesis,one of the few known examples of receptors with distal regulation for dicarboxylic acids has also been developed.

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Palmer, Andrew John. "The Design and Synthesis of Chiral Sulfides for Use in Asymmetric Epoxidations." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486012.

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This thesis describes the design and synthesis of chiral sulfides for use in asymmetric cpoxidations. Chiral sulfides have been designed around the naturally-occurring chiral starting materials carvone and 'limonene. This has enabled the synthesis of new chiral sulfides as single enantiomers without the need for any resolution to be performed. Carvone-based sulfides 43 and 53 have been synthesised and can be used to produce cpoxides in high selectivity. The synthesis of racemic chiral sulfides has also been investigated and conditions have been developed for the addition 'of non-nucleophilic heterocycles to bicyclic sulfide 76. These conditions have been used with a range of heterocycles that are unreactive towards addition to 76 via existing conditions. C2-symmetric sulfides 81, 82, 86, and 87 have been synthesised but were found to be unreactive towards alkylation. The addition of sulfenyl chlorides to alkenes has also been investigated as a method for synthesising chiral sulfides from chiral naturally-occurring alkenes. Epoxidations using ylides ,stabilised by anionic amide groups have also been researc~ed. Chiral sulfonium salt 67 has been synthesised, but failed to produce epoxides in high enantioselectivities.

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Tadikonda, Udaya Bhaskar. "Design, synthesis and applications of tetradentate transition metal complexes towards asymmetric alkylations." Diss., Tucson, Ariz. : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1131%5F1%5Fm.pdf&type=application/pdf.

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Wang, Jianli. "Design and Characterization of Central Functionalized Asymmetric tri-Block Copolymer Modified Surfaces." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29574.

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Well-defined central functionalized asymmetric tri-block copolymers (CFABC) were designed as a new type of polymer brush surface modifier, with a short central functionalized block that can form chemical bonds with a suitable substrate surface. A combination of sequential living anionic polymerization and polymer modification reactions were used for the synthesis of two CFABCs: PS-b-poly(4-hydroxystyrene)-b-PMMA and PS-b-poly(4-urethanopropyl triethoxysilylstyrene)-b-PMMA. GPC and NMR characterization indicated that the block copolymers possessed controlled molecular weights and narrow molecular weight distributions. CFABC polymer brushes were successfully prepared by chemically grafting PS-b-poly(4-urethanopropyl triethoxysilylstyrene)-b-PMMA onto silicon wafer surfaces. AFM, XPS and ellipsometry were used to confirm the CFABC polymer brush structures and thickness. The surface properties of CFABC polymer brush modified silicon wafer substrates subjected to different environmental parameters were studied. Reversibly switchable surface energies were observed when the polymer brush modified surfaces were exposed to solvents with different polarities. The phenomenon was attributed to the chain configuration auto-adjustment in the polymer brush systems. The same mechanism was also used to explain the enhanced adhesion capability between the modified surfaces and different polymer materials (PS and PMMA). Phase behaviors of polymer thin films on unmodified and CFABC polymer brush modified silicon wafer surfaces were also studied. For thin films of polymer blends, PS blend PS-co-PMMA, the effects of film thickness, chemical composition and temperature on the phase separation mechanism were investigated. The phase behavior in thin films of triblock copolymers with or without central functionalities were compared to reveal the role of the central functionalized groups in controlling film structures. Finally, the presence of CFABC polymer brush at the interface between PS-b-PMMA diblock copolymer thin film and silicon wafer substrate was found to decrease the characteristic lamellar thickness in the thin film. A mechanism of tilted chain configurations in the thin film due to the interactions with the CFABC polymer brushes was proposed.
Ph. D.

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Rogers, Jeremy David. "Miniature Microscope Design And Construction Based On Tilted Rotationally Asymmetric Printed Lenses." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194489.

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Successful treatment of many types of cancer is improved when early detection is possible. One method of early detection is microscopic inspection of the tissue at risk. Microscopic inspection can be performed by extracting a biopsy and using traditional microscopes, but biopsy is painful and inconvenient which limits its use. An alternative is in vivo microscopy using an endoscope or microendoscopy. This dissertation describes the design, construction, and evaluation of a miniature microscope or microendoscope based on new microfabrication technologies.All components typically found in a traditional bench-top microscope were designed and built on a miniature scale. The objective was comprised of one planoconvex spherical glass lens and three printed microlenses. The printed lenses were patterned using grayscale lithography in a custom engineered photosensitive hybrid sol-gel glass material. Illumination was delivered by high-brightness Light Emitting Diodes (LEDs) via multimode fiber. The design incorporated a custom imaging detector and a Micro-Electrical-Mechanical-Systems (MEMS) actuator for optical sectioning using structured illumination. The opto-mechanical system is designed using a new concept called "zero alignment assembly" in which the lens elements snap into place and are constrained to a precise position with tolerances tighter than the optical tolerances. This scheme requires no post-assembly alignment or adjustment and simplifies system assembly. The miniature microscope was designed to image in several modes including reflectance, fluorescence, and using structured illumination for optical sectioning. A unique optical design incorporated tilted elements to remove ghost images and internal reflections from the image plane. This design enabled microscopic imaging of extremely low reflectance samples like tissue where the "in-focus" component of the object reflects only 0.04% of the illumination. The miniature microscope was built and tested by imaging a variety of test objects including cancer tissue phantoms and pig tissue. The results demonstrated the successful implementation of many new microfabrication technologies and design concepts to build a working prototype miniature microscope measuring only 3x4x15 mm capable of imaging cellular structure of tissue in reflectance or flourescence.

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Chang, Po-Yi, and 張伯毅. "Parameterized Optical Design of Asymmetrical Automobile Headlamp." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/g67772.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
102
The proposed research provided an alternative approach to design an automobile headlamp base on the parameterized optical design. Differing from the traditional free form reflectors, this paper uses eight variable-focus-parabolic curves, in which each curve is determined by four parameters, construct a free form reflector. In order to obtain a certain light pattern (e.g. Europe ECE R112 regulations for automotive headlamps), sensitivity analysis is necessary to determine the relationship between the curves’ parameters and the certain light pattern. Base on the results of sensitivity analysis, we can tune the useful parameters to finally satisfy the requested light pattern. The validity of the final design is demonstrated by means of ZEMAX simulations. It is shown that the parameterized free form reflector design yields a significant improvement in efficency compared to conventional free form reflector design.

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Huang, Tao-chen, and 黃道朕. "Analysis and Design of Asymmetrical Half-Bridge Converter." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/32903001425969773187.

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碩士
國立臺灣海洋大學
電機工程學系
96
In traditional switching power supplies, hard switching is detrimental to high switching loss, high electromagnetic interference and high switch voltage stress. For improving above-mentioned shortcomings, the soft switching technique is used to reduce switching losses, EMI noises and the switch voltage stresses.The soft switching circuit consists of two power switches, a blocking capacitor and a resonant inductor. Zero-voltage switching also can be used in this converter. This paper proposes to analysis and design of the converter circuit. The steady state circuit is simulated by the software IsSpice to verify the analysis. The output of dc-dc converter is 120 watt. The input dc voltage is 400V.The output voltage is 24V.The simulation result verify the feasibility of the proposed method.

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Chang, Yu-Yun, and 張又允. "Single Asymmetrical Lens Design for Laser Diode Collimator." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/92889093737640222546.

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碩士
輔仁大學
物理學系
96
Since Optical Information Storage System has advanced into a high volume era, in order to increase the storage density, during the design process of the Pickup-head we can either choose to use a laser diode which has shorter wavelength; or, we can increase the numerical aperture of the Objective lens. Both options allow us to decrease the spot size of the laser. However, owing to the special structure of the resonator in the laser diodes, the output beams of the laser diode are usually elliptically diverging with a certain amount of astigmatism. Therefore the collimator within the system has a major impact on the quality of the spot size. In conclusion, the purpose of this article is to design a single asymmetrical aspherical collimator with the laser diode of ROHM RLD65MPT7 and with the lens aperture of objective lens in US Patent 6995929. The expected value of diameter of circular-parallel output beam is 2.2875mm, and the value is 2.2904mm after computing. Hence, the error has only 0.13%.

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38

Poon, Samuel. "Wireless receiver designs for asymmetric constellations." 2004. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=95037&T=F.

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Leu, Yi-Hsin, and 呂宜興. "Analysis and Design of Asymmetrical Half-Bridge Forward Converter." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/14142706798327158438.

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博士
國立臺灣大學
電機工程學研究所
92
For applications under 1kW, asymmetrical half-bridge forward converter has been adopted widely because of its simple structure, low voltage stress on power switch, and zero-voltage-switching (ZVS) capability. Analysis and design of the asymmetrical half-bridge forward converter are provided in this dissertation. The characteristics of the conventional asymmetrical half-bridge forward converter will be analyzed first, and then the two-transformer asymmetrical half-bridge converter will be also discussed. The operating principle, ZVS conditions of power switches and design considerations of the above converters are investigated. Finally, a new asymmetrical half-bridge converter topology is proposed. Compared with the conventional asymmetrical half-bridge forward converter, the proposed converter permits extension of the allowable duty cycle to above 50%. Additionally, the ZVS condition, current stress on power switch and overall efficiency are improved.

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ZENG, WEN-ZHAO, and 曾文炤. "The design of asymmetrical register structure for VLIW/FC." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/91103296487539033274.

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Li, Ching-Shiang, and 李清祥. "Study on the backlit design with asymmetrical light source." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/20888302767026532665.

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碩士
國立交通大學
光電工程系所
93
The major concern of this thesis is to analyze the light distribution on the light-guide plate of backlight module with asymmetrical light sources for a liquid-crystal display(LCD). The major function of the light-guide plate is to make a LCD having good luminance uniformity and the design of light-guide plate directly impacts the performance of image quality of LCD. We can sort the backlight module to two types of direct type backlight module and side-edge backlight module by location of the light sources. There are also two kinds of side-edge backlight module having symmetrical or asymmetrical light sources. Because having difference of the location of light sources, the design of light-guide plate is also different. In this thesis, we will do theoretical analysis of light-guide plate with asymmetrical light sources and run simulation to test and verify our result by optical software , Tracepro. In this thesis, the experimental observation of a commercial product is also included.

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42

Pong, Chen-Yin, and 彭成銀. "Design and Applications of Asymmetrical Half Bridge DC-DC Converter." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/68582976159588570263.

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碩士
清雲科技大學
電機工程研究所
96
This thesis consists of two parts. The first part presents analysis and design of an asymmetrical half bridge converter with flyback type transformer, in which the power switches can be turned on with ZVS and the output diode can be turned on and off with ZCS or low di/dt . The maximum voltage stress of power switches is not greater than the input voltage. While the ZVS is obtained from the magnetizing current, the ZCS is achieved from the resonant current. The soft switching conditions can be maintained from no load to full load range. The characteristics of the proposed converter rely on the utilization of resonant inductor and blocking capacitor as resonant devices rather than linearly charging and discharging components. The operational principle and design consideration of the proposed converter is described in this thesis. The experimental test along with computer simulation of a 90W/12V prototype converter is performed and the results are presented. The secondary part of this thesis deals with the design and implementation an asymmetrical half bridge DC-DC power converter with current doubler and synchronous rectifier for high efficiency power supply application. The operation modes, analysis and design, components selection, experimental prototype and measurements, and energy consumption analysis are performed in the thesis. In the proposed 300W/12V/25A converter, the synchronous rectifiers are driven by the transformer windings at the secondary side. Both the power switch and synchronous rectifier can be turned on with ZVS from no load to full load conditions, which results in high efficiency. The prototype test results show that the converter efficiency at full load is 88.25%, and is 92.6% at half load. The major energy consumptions focus on the conduction losses from semiconductor devices and hysteresis losses from magnetic components.

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LIAO, KANG-CHUN, and 廖罡淳. "Design and Analysis of Ultra-Wideband Antenna for Asymmetrical Patch." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/17864334330080672138.

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碩士
臺北城市科技大學
機電整合研究所
102
In this thesis, there is great possibilities that the radiated structure of antenna can be shrunk about 50% area by using the image charge theorem. Compared with the full-patch antenna in this work, the patch area is only 57% for image semi-patch structure antenna. The impedance bandwidth of full-path antenna extends from 3.3GHz to 6.54GHz, or percentage bandwidth = 65%. The peak of antenna gain is about is 3.3dBi at 5.8GHz. On the one hand, the impedance bandwidth of semi-path antenna extends from 3.12GHz to 6.92GHz, or percentage bandwidth = 75%. The peak of gain is only 2.7dBi at 6.2GHz. From the results above, the small size semi-patch antenna radiate similar frequency band to the full-patch one. It implies that the semi-patch antenna can substitution for full-patch one in spite of antenna gain. Semi-patch structure can also be designed in ultra-wideband antenna. The bandwidth of our ultra-wideband antenna with semi-patch structure is from 2.42GHz to 12.4 GHz, or percentage of bandwidth = 130.4% , covering the use of ultra-wideband antenna range.

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44

Lin, Jing-Han, and 林敬瀚. "Design and Implementation of Current-fed Asymmetrical Half-bridge Converter." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/81995770699527156612.

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碩士
國立臺灣科技大學
電子工程系
103
The conventional hard-switching power converter presents serious electromagnetic interference (EMI) issue and a poor efficiency. By using the zero-voltage-switching (ZVS) asymmetrical half-bridge converter, switching losses and EMI noises can be reduced. This thesis aims to study and implement a current-fed asymmetrical half-bridge converter with simple circuit, low device stress and soft-switching features. Operating frequency and conversion efficiency can be effectively raised. The operation principles and design considerations of the studied current-fed asymmetrical half-bridge converter are analyzed and discussed in details. Simplis simulation and experimental results for a 400W prototype converter were implemented and tested for verify the feasibility.

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45

Hsu, Meng-Nien, and 許孟年. "Design of LED Lens with Asymmetrical Irradiance Distribution and Application." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/52874987775269839994.

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碩士
國立臺灣科技大學
電機工程系
103
The thesis focused on the design of secondary optical lens of asymmetrical distribution. The idea of zonal flux analysis provides us a fast and efficient way to analyzing the luminous flux of the sources and our targets while using the proposed secondary optical TIR lens design method to develop the luminaires. By using 3D model software SolidWorks we can build up our lens and verifying our design through ray tracing software TracePro. A TIR lens with symmetrical distribution was given in the thesis to prove the feasibility of the proposed methods. Moreover, due to the needs of designs to improve the lighting environments of current lecture halls, we designed two luminaires with asymmetrical distribution for the blackboard and the desks. A lecture hall was further built within lighting design software DIALux to show the results of the luminaires. To guarantee the proposed luminaires were ideal, an evaluation system was set up and two control groups were compared, with one using conventional T5 luminaires and the other using a LED blackboard luminaire with asymmetrical distribution and a LED desk luminaire with symmetrical distribution. The designed evaluation system mainly focused on the feeling of human so as to take uniformity and UGR more seriously. The results showed that the proposed luminaires provide better lighting environment for the lecture hall.

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Li, Lung-Shiang, and 李龍翔. "Study of traffic lamp lens design of asymmetrical optical field." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/70180444938338124213.

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碩士
國立高雄應用科技大學
光電與通訊研究所
98
The study mainly design a lamp, which have the special optical field (asymmetrical optical field ).and the lamp is combination the lens system and the light source to redistribution the optical field of light source, and in order to more accurately to reach out requires, so we use numerical compute the curvature of lens surface to design the lens surface profile. This lens system is combining the convergence lens and the wedge-shaped lens, that is not only to control the range of light of convergence and accurate guide light source to ideal position. For example, we will meet the requirement of traffic signal light, so that to verify the feasibility of lens system of symmetrical luminance distribution, and we will use the optical simulation software TraceProTM to simulate in different conditions such as the range of light of convergence, convergence lens and the wedge optical component space and so the effect. The research is carried out by analyzing the different parameters of experiment to obtain the best choose. As the result, the design lamp in this study, it can accurately achieve optical field of requirement of traffic lamp, and we can arrangement of superposition and symmetrical to make up the lack of demand for light intensity, and this is not to affect the optical field distribution of light source.

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47

Liu, Hong-Jun, and 劉鴻鈞. "Design of Miniaturized Asymmetrical CPW-fed Antennas for Wireless Communication." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/g9m63n.

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碩士
國立虎尾科技大學
光電與材料科技研究所
95
Antenna which is put at the front and always significantly affects the communicationquality has become a most important element for a communication system. For potential usein a modern mobile communication system, the trend of antenna design is focused on thecritics of light weight, planar profile and compact size. Therefore, the planar microstrip antenna is the most suitable prototype for wireless communication due to its wide bandwidth, good impedance matching, simple structure of a single metallic layer, no soldering point, and easy integration with system circuit etc. In this thesis, the structure of a coplanar-waveguide (CPW) feeder with two asymmetrical grounds, printed on an FR4 substrate, was utilized to design a multi-band compact antenna for wireless local area network (WLAN) application. Also, the electromagnetic coupling effects on resonant frequencies between the feeding line and the asymmetrical grounds were studied. The design based on a CPW-fed antenna with an asymmetrical ground structure hasfirstly been studied to achieve a resonant mode suitable for 5.2 GHz or 5.8 GHz WLAN use by adjusting lengths of the feed line and the inverted-L shaped ground. The electromagnetic coupling effect on resonant frequencies between the radiating elements has been investigated,too. Thereafter, by way of properly extending the loaded radiating patch of the antenna and embedding a slot into the patch, the proposed antenna can produce triple-band resonance covering the 2.4/5 GHz WLAN bands and the C-band satellite communication. Finally, the technology of meander line is applied to miniaturize the antenna size and increase the impedance bandwidth in 5.2 GHz band. The modified antenna is only 9×17 mm2 and can excite resonant modes at 2.44, 5.07, and 7.17 GHz bands with measured -10 dB impedance bandwidths of 14.3 %, 16.3%, and 19.8 %, respectively. The antenna is very compact and able to cover the 2.4/5.2 GHz WLAN as well as the satellite communication operating at C band.

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Chen, Chih-You, and 陳祉佑. "Asymmetric Microsatellite Constellation Design for Communication." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/95838813651530210361.

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碩士
淡江大學
機械與機電工程學系碩士班
98
The main purpose of this thesis focus on design of Microsatellite Constellation Communication, use the range of tasks to Taiwan as the center of the coverage radius of 2,000 km, adopt the circular orbit of 800 km, 1,500 km and asymmetric circular orbit combination 800 km and 1,500 km with the inclination 35° , to simulate the Walker Constellation, in order to achieve the minimum number of satellites for the purpose, to achieve mission objectives that coverage gap is zero. The calculated result shows that in the circular orbit of 800 km at less need 34 satellites, the circular orbit of 1,500 km at less need 18 satellites, then use the asymmetric circular orbit constellation can select 27, 32, 35 and 39 satellites to achieve mission objectives. Obtain the optimization constellations in fix orbit inclination. Finally, discuss contain coverage gaps of the constellation can be used situation and extension the scope of this thesis design constellations.

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Chen, Huang-Yun, and 陳皇運. "Design and Implementation of a High Efficiency Asymmetrical Half-Bridge Converter." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/83905137269578995920.

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碩士
國立臺灣科技大學
電子工程系
96
Existing hard-switching power supply produces electromagnetic interference and inadequate efficiency. By using the Zero-Voltage-Switching (ZVS) asymmetrical half-bridge (AHB) Pulse-Width-Modulation (PWM) converter, switching losses and noises can be reduced, thus increasing the operating frequency and circuit efficiency. An asymmetrical half-bridge has the following advantages: simple structure, lower switches’ voltage rating, ZVS, and its appropriateness for application in higher than 1kW power supply systems. This thesis focuses on the design of an asymmetrical half-bridge converter with synchronous current-doubler rectification, and with its front-end part added with a power factor corrector (PFC). The power MOSFETs are utilized instead of Schotky diodes for the secondary-side current-doubler rectification. Therefore, the efficiency of the low-voltage high-current converter can be increased. The basic principle of the asymmetrical half-bridge converter is analyzed, several circuit techniques are discussed, and circuit simulations using SIMETRIX are implemented. Then a prototype of the 200W converter is realized and the experimental results verify the theoretical and simulation analysis. In order to meet the size-minimization requirement, the size of this converter is optimized down to 12.8cm (L)、7.6cm (W) and 4.7cm (H), with Surface Mounted Devices (SMD) adopted.

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林一志. "Design and Implementation for Asymmetrical Half-Bridge Converter with Synchronous Rectifier." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/04791897919463069368.

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碩士
國立臺北科技大學
機電整合研究所
90
The objective of this thesis is to implement an asymmetrical half-bridge converter with synchronous rectifier. The main switching device can be turned on under zero voltage, and thereby reducing the switching losses. A synchronous rectifier is used to replace diodes at out stage in order to reduce the conduction losses. At first, the operation principle of asymmetrical half-bridge converter with synchronous rectifier is described in this thesis. Then, design considerations for a practical 3.3 V/10 A asymmetrical half-bridge converter with synchronous rectifier is illustrated. Moreover, a conventional asymmetrical half-bridge converter for the same specifications is realized for comparisons and confirming that the presented topology can significantly improve the efficiency.

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Dissertations / Theses on the topic 'Asymmetrical Designs'

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