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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.
111

Argos: Practical Base Stations for Large-scale Beamforming

Shepard, Clayton 06 September 2012 (has links)
MU-MIMO theory predicts manyfold capacity gains by leveraging many antennas (e.g. M >> 10) on wireless base stations to serve many users simultaneously through multi-user beamforming (MUBF). However, realizing such a large-scale design is nontrivial, and has yet to be achieved in the real world. We present the design, realization, and evaluation of Argos, the first reported large-scale base station that is capable of serving many (e.g., 10s of) terminals simultaneously through MUBF. Designed with extreme flexibility and scalability in mind, Argos exploits hierarchical and modular design principles, properly partitions baseband processing, and holistically considers real-time requirements of MUBF. To achieve unprecedented scalability, we devise a novel, completely distributed, beamforming technique, as well as an internal calibration procedure to enable implicit beamforming across large arrays. We implement a prototype with 64 antennas, and demonstrate that it can achieve up to 6.7 fold capacity gains while using a mere 1/64th the transmission power.
112

Asymmetric Alkenylation of Enones and Other α,β-Unsaturated Carbonyl Derivatives Using Chiral 3,3′-Disubstituted Binaphthols and Boronates

Guobadia, Bobby 22 May 2009 (has links)
Various α,β-unsaturated carbonyl compounds and derivatives were explored in order to expand the range of substrates for the 1,4-addition of alkenylboronates using 3,3′-disubstituted binaphthols. Enones 2.60 were examined and found to be suitable for conjugate addition under our proposed reaction conditions. The asymmetric 1,4-additions of alkenylboronates to enones 2.60 using catalytic amounts of 3,3′-disubstituted binaphthols was shown to occur with moderate to good yields and high enantioselectivities. The chiral products could serve as enantioenriched substrates for further transformation such as asymmetric reduction, which was performed with good yield and selectivity. The absolute configuration for the alkenylation of enones was also confirmed to be the (R) enantiomer using (S)-3,3′-disubstituted binaphthols via X-ray crystallographic analysis. Investigations into selective Baeyer-Villiger oxidation of 1,4-addition products of enones was also examined. Although the desire ester products were not obtained, intriguing informative findings were still obtained from the investigation.
113

Regularization Using a Parameterized Trust Region Subproblem

Grodzevich, Oleg January 2004 (has links)
We present a new method for regularization of ill-conditioned problems that extends the traditional trust-region approach. Ill-conditioned problems arise, for example, in image restoration or mathematical processing of medical data, and involve matrices that are very ill-conditioned. The method makes use of the L-curve and L-curve maximum curvature criterion as a strategy recently proposed to find a good regularization parameter. We describe the method and show its application to an image restoration problem. We also provide a MATLAB code for the algorithm. Finally, a comparison to the CGLS approach is given and analyzed, and future research directions are proposed.
114

Asymmetric Alkenylation of Enones and Other α,β-Unsaturated Carbonyl Derivatives Using Chiral 3,3′-Disubstituted Binaphthols and Boronates

Guobadia, Bobby 22 May 2009 (has links)
Various α,β-unsaturated carbonyl compounds and derivatives were explored in order to expand the range of substrates for the 1,4-addition of alkenylboronates using 3,3′-disubstituted binaphthols. Enones 2.60 were examined and found to be suitable for conjugate addition under our proposed reaction conditions. The asymmetric 1,4-additions of alkenylboronates to enones 2.60 using catalytic amounts of 3,3′-disubstituted binaphthols was shown to occur with moderate to good yields and high enantioselectivities. The chiral products could serve as enantioenriched substrates for further transformation such as asymmetric reduction, which was performed with good yield and selectivity. The absolute configuration for the alkenylation of enones was also confirmed to be the (R) enantiomer using (S)-3,3′-disubstituted binaphthols via X-ray crystallographic analysis. Investigations into selective Baeyer-Villiger oxidation of 1,4-addition products of enones was also examined. Although the desire ester products were not obtained, intriguing informative findings were still obtained from the investigation.
115

Quantitative Conjugate Imaging of Iodine-123 and Technetium-99m Labeled Brain Agents in the Basal Ganglia

Jangha, Desiree Nicole 10 July 2006 (has links)
In the research reported in this dissertation, the concept of classic conjugate imaging, a non-tomographic nuclear medicine technique, is modified such that activity of a radiopharmaceutical distribution in the striata can be estimated. A mathematical model is developed that extended the application of classic conjugate imaging to estimation of two distinct and aligned activity distributions. Error analysis of the mathematical model is performed to characterize the accuracy of the model and to benchmark the limitations of the model. Phantom experiments are performed to demonstrate the practical application of the model and to evaluate its accuracy. A Monte Carlo simulation model of conjugate imaging of activity uptake in the striata of a primate is developed to evaluate the accuracy of the modified conjugate imaging technique as applied in the use of a dedicate conjugate imaging system. In addition, the simulation model is used to determine and characterize the shielding design of the small field of view gamma cameras comprising the dedicated conjugate imaging system. The application of scatter correction is investigated to address the downscatter of high-energy photon emissions into the photopeak window and the inclusion of scattered primary photons in the photopeak window. In this dissertation, it is shown that the modified conjugate imaging technique developed can be used to estimate accurately activity uptake in each of two distinct and aligned activity distributions. The accuracy of the technique is shown to be comparable to that of clinical quantitative SPECT. The modified conjugate imaging technique used with the dedicated conjugate imaging system may, therefore, be a viable quantitative nuclear medicine technique for activity estimation of radiopharmaceutical uptake in the striata of Parkinsonian and schizophrenic patients. The portability and low cost relative to SPECT systems make a dedicated conjugate imaging system advantageous for clinics with Parkinsonian and schizophrenic patients, who are unable to travel due to physical or mental limitation.
116

Generalized minimal polynomial over finite field and its application in coding theory

Jen, Tzu-Wei 27 July 2011 (has links)
In 2010, Prof. Chang and Prof. Lee applied Lagrange interpolation formula to decode a class of binary cyclic codes, but they did not provide an effective way to calculate the Lagrange interpolation formula. In this thesis, we use the least common multiple of polynomials to compute it effectively. Let E be an extension field of degree m over F = F_p and £] be a primitive nth root of unity in E. For a nonzero element r in E, the minimal polynomial of r over F is denoted by m_r(x). Then, let Min (r, F) denote the least common multiple of m_r£]^i(x) for i = 0, 1,..., n-1 and be called the generalized minimal polynomial of over F. For any binary quadratic residue code mentioned in this thesis, the set of all its correctable error patterns can be partitioned into root sets of some generalized minimal polynomials over F. Based on this idea, we can develop an effective method to calculate the Lagrange interpolation formula.
117

Design of Conjugate Cam Mechanisms for Internal Combustion Engines

Chung, Huai-Sheng 04 January 2012 (has links)
Due to the kinematic limitation of slider-crank mechanisms used in traditional internal combustion engines, such devices driven by their piston motions have a difficulty to reach the better fuel efficiency. In order to make the fuel efficiency better, many engine mechanisms that can be tuned to obtain desired piston motions have been proposed. Since most of the proposed engine mechanisms have complex linkages and bulky size, they become impractical for real applications. The design of a conjugate cam engine mechanism containing a conjugate cam with a slider crank mechanism can be conveniently tuned to produce a desired piston motion in consideration of a limited space, weight, and the number of linkages. The aim of this research is to set up a systematic design and analysis procedure for conjugate cam engine mechanisms. First of all, the kinematic analysis of conjugate cam engine mechanisms is performed based on the rigid body transformation method to determinate the conjugate cam profiles. Then, the geometric properties including the pressure angle and radius of curvature are investigated. Also, in order to characterize the rigid body dynamic behavior of the mechanism, the Newton¡¦s Law is used to derive equations of motion. Finally, it is conducted to design and analyze a real system, and observe the real condition from the experiment to prove the theory is correct.
118

Massively-Parallel Direct Numerical Simulation of Gas Turbine Endwall Film-Cooling Conjugate Heat Transfer

Meador, Charles Michael 2010 December 1900 (has links)
Improvements to gas turbine efficiency depend closely on cooling technologies, as efficiency increases with turbine inlet temperature. To aid in this process, simulations that consider real engine conditions need to be considered. The first step towards this goal is a benchmark study using direct numerical simulations to consider a single periodic film cooling hole that characterizes the error in adiabatic boundary conditions, a common numerical simpliflication. Two cases are considered: an adiabatic case and a conjugate case. The adiabatic case is for validation to previous work conducted by Pietrzyk and Peet. The conjugate case considers heat transfer in the solid endwall in addition to the fluid, eliminating any simplified boundary conditions. It also includes an impinging jet and plenum, typical of actual endwall configurations. The numerical solver is NEK5000 and the two cases were run at 504 and 128 processors for the adiabatic and conjugate cases respectively. The approximate combined time is 100,000 CPU hours. In the adiabatic case, the results show good agreement for average velocity profiles but over prediction of the film cooling effectiveness. A convergence study suggests that there may be an area of unresolved flow, and the film cooling momentum flux may be too high. Preliminary conjugate results show agreement with velocity profiles, and significant differences in cooling effectiveness. Both cases will need to be refined near the cooling hole exit, and another convergence study done. The results from this study will be used in a larger case that considers an actual turbine vane and film cooling hole arrangement with real engine conditions.
119

Numerical Investigation On Cooling Of Small Form Factor Computer Cases

Orhan, Omer Emre 01 January 2007 (has links) (PDF)
In this study, cooling of small form factor computer is numerically investigated. The numerical model is analyzed using a commercial computational fluid dynamics software Icepak&trade / . The effects of grid selection, discretization schemes and turbulence models are discussed and presented. In addition, physical phenomena like recirculation and relaminarization are addressed briefly. For a comparison with the computational fluid dynamics results, an experiment is conducted and some temperature measurements are obtained from critical locations inside the chassis.The computational results were found to be in good agreement with the experimental ones.
120

One-pot Synthesis Of Chloroalcohols And Their Lipase Mediated Kinetic Resolution - Ferrocenyl Aziridinylmethanols As Chiral Ligands In Enantioselective Conjugate Diethylzinc Addition To Enones

Isleyen, Alper 01 September 2007 (has links) (PDF)
An unexpected tricyclic ether formation instead of acetate addition to the double bond of a norbornene derivative aroused our interest to explore the mechanism of this reaction. Mechanistic studies showed that methylene diacetate (MDA) was formed in the stock solution (NBu4OAc + dichloromethane) and decomposed to formaldehyde under Lewis or Br&oslash / nsted acid conditions. Formaldehyde and olefin condensation (Prins reaction) clearly explains the formation of the unexpected product. Same methodology was then successfully applied to develop a one-step procedure for the synthesis of 3-chloro-3-arylpropanols, which are important starting materials for the synthesis of biologically active benzanilide derivatives. Styrenes were reacted with MDA in the presence of boron trifluoride to give the corresponding 3-chloro-3-arylpropanols in 36&amp / #8211 / 84% yield. The second part of the thesis involves kinetic resolution of 3-chloro-3-arylpropanols by lipase mediated acylation which are described for the first time. Acylation with the CCL provided the best enantioselectivity amongst the enzymes used. Enantiomerically enriched products with up to 78% ee were obtained after two successive lipase-mediated acylations. Different substituents on the aromatic ring and bromide, instead of chloride, at the benzylic position of the substrates were found to have no drastic influence on the enantioselectivity of the reaction. In the last part, easily available ferrocenyl substituted aziridinylmethanols (FAM) were complexed with nickel to catalyze the enantioselective diethylzinc addition to various enones with ee&amp / #8217 / s reaching 82%. The ligands can be recovered and used without losing their activity. The sense of asymmetric induction was found to be dependent on the configuration of the aziridine ring.

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