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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.
71

Metas de manejo para pastos de Tifton 85 submetidos a diferentes estratégias de utilização : impactos na estrutura do pasto, eficiência de colheita e produção de forragem / Management targets for pastures of tifton 85 submitted to different utilization strategies : impacts on sward structure, harvesting efficiency and forage production

Eidt, Jeferson January 2015 (has links)
Este estudo teve por hipótese que o manejo de pastos de Tifton 85 baseado em parâmetros ingestivos dos animais (pastoreio Rotatínuo – RN), resulta em colheita do pasto mais eficiente que no manejo tradicional. Foram estudadas três estratégias de manejo de pastoreio rotativo em pastos de Tifton 85 pastejados por novilhas leiteiras no Sul do Brasil. Os tratamentos consistiam em variações de critério de altura de pasto para entrada e retirada dos animais. O primeiro tratamento foi o método de pastoreio rotativo “clássico” (máximo aproveitamento do pasto) com metas de altura de manejo pré-pastejo de 30 cm e pós-pastejo de 5 cm (30-05). O segundo tratamento foi o Rotatínuo (RN) que permite a máxima taxa de ingestão de forragem, com altura pré-pastejo de 19,2 cm e pós-pastejo de 11,5 cm. No terceiro tratamento foi utilizada uma proposição de rebaixamento de apenas 40% da altura pré-pastejo tradicionalmente recomendada no país, 30 cm de altura pré-pastejo e 18 cm de altura pós-pastejo (30-18). Foram utilizados animais da raça Holandês, com idade de 20±2 meses e peso médio de 496±22 kg. O delineamento experimental foi em blocos completos casualizados com três repetições. O período experimental foi de 67 dias, entre 14 de janeiro a 22 de março de 2014. Os número de pastejos chegaram a 7 para o RN, 2 para o RT e 5 para o 30-18. A taxa de ingestão de forragem foi semelhante entre os tratamentos. Para manter a taxa de ingestão constante os animais utilizaram diferentes componentes do comportamento. No tratamento 30-05 os animais apresentaram maior massa do bocado, e no RN maior taxa de bocado (P<0,05). O RN obteve maior taxa de acúmulo diária de forragem frente aos demais tratamentos, maior massa de forragem colhida e maior eficiência de colheita do pasto (P<0,05). A adoção de metas de manejo do pasto via alturas pré e pós-pastejo definidas por parâmetros ingestivos, conforme previsto no Rotatínuo, possibilitou obter adequada eficiência de colheita de pasto, sem comprometer o potencial de regeneração dos pastos. / This study hypothesized that the grazing management of Tifton 85 based on animal ingestive behavior parameters (Rotatinuous grazing - RN), results in higher harvesting efficiency than traditional management. Three rotational grazing management strategies were tested on Tifton 85 pastures grazed by dairy heifers in southern Brazil. The treatments were different sward height targets to put and take the animals from the strip. The first treatment was the traditional rotational grazing method named "Classic" (maximum pasture harvest) with pre-grazing height of 30 cm and post-grazing of 5 cm (30-05). The second treatment was named Rotatinuous (RN), aimed to maximize the animal herbage intake rate, where the pre-grazing height was 19.2 cm and post-grazing of 11.5 cm. In the third treatment it was proposed the grazing down of 40% of pre-grazing height traditionally recommended in Brazil (30 cm), resulting in 30 cm and 18 cm of pre and post-grazing height, respectively (30-18). Holstein animals, aged 20 ± 2 months, were used with an average weight of 496 ± 22 kg. The experimental design was a randomized complete block design with three replicates. The experimental period was 67 days, from 14 January to 22 March 2014. The numbers of grazing cycles were 7 on RN, 2 on 30-05 and 5 on 30-18 treatments. Herbage intake rate did not differ among treatments (P>0.05). The animals behaved differently using distinct grazing behavior strategies during the grazing down in order to reach the same level of intake rate. In the treatment 30-05 animals presented higher bite mass, whist RN higher bite rate (P <0.05). The RN had higher daily herbage accumulation rate, amount of forage harvested and pasture harvest efficiency (P <0.05). The grazing management goals defined by ingestive parameters (Rotatínuous) provided adequate pasture harvest efficiency without compromising pasture regrowth potential.
72

Design, manufacturing, and testing of high speed rotating graphite/epoxy shafts

Bauchau, Olivier André January 1981 (has links)
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO. / Includes bibliographical references. / by Olivier Andre Bauchau. / Sc.D.
73

Collision Broadening of Microwave Spectral Lines of Monomeric Formaldehyde and Formic Acid

Venkatachar, Arun C. 08 1900 (has links)
Line width parameters for a number of spectral lines in the pure rotational spectrum of formaldehyde (CH20) and formic acid (HCOOH) have been measured using a sourcemodulated microwave spectrograph. All transitions studied in this investigation were of the type ΔJ=O (i.e. Q-branch transitions), with ΔK-1=0 and ΔK+1 =+l. The center frequencies of the measured lines varied from 8662.0 MHz to 48612.70 MHz. The experimentally determined collision diameters for self broadening interactions involving HCOOH and CH2 Q molecules were found to be 2 - 27 per cent less than those calculated by the Murphy-Boggs theory of collision broadening. Much better agreement between a simplified broadening scheme for symmetric top molecules and the observed foreign-gas collision diameters is obtained by using Birnbaum's theory.
74

An experimental investigation of compressor performance in rotating stall

Eastland, Anthony Henry James January 1982 (has links)
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO. / Includes bibliographical references. / by Anthony Henry James Eastland. / M.S.
75

Shot-noise correlation theory for weak measurement of a single spin in a quantum dot. / 量子點內自旋弱量度的散粒噪聲相關理論 / Shot-noise correlation theory for weak measurement of a single spin in a quantum dot. / Liang zi dian nei zi xuan ruo liang du de san li zao sheng xiang guan li lun

January 2008 (has links)
Fung, Shu Hong = 量子點內自旋弱量度的散粒噪聲相關理論 / 馮書航. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 80-85). / Abstracts in English and Chinese. / Fung, Shu Hong = Liang zi dian nei zi xuan ruo liang du de san li zao sheng xiang guan li lun / Feng Shuhang. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Review on measurement theory --- p.5 / Chapter 2.1 --- Weak measurement --- p.5 / Chapter 2.2 --- POVM formalism --- p.7 / Chapter 2.3 --- Noise spectroscopy --- p.8 / Chapter 3 --- Review on spin decoherence --- p.11 / Chapter 3.1 --- Longitudinal relaxation --- p.12 / Chapter 3.2 --- Transverse relaxation --- p.12 / Chapter 3.3 --- Inhomogeneous broadening --- p.13 / Chapter 3.4 --- Typical relaxation timescales --- p.14 / Chapter 4 --- Proof-of-principle setup --- p.15 / Chapter 4.1 --- Faraday rotation --- p.15 / Chapter 4.2 --- Polarization beam splitter --- p.17 / Chapter 4.3 --- Quantum state of the system --- p.19 / Chapter 5 --- Weak measurement on the spin --- p.22 / Chapter 5.1 --- POVM of measurement --- p.22 / Chapter 5.2 --- POVM of dephasing --- p.25 / Chapter 5.3 --- Interval distribution operator --- p.26 / Chapter 5.4 --- Interval distribution function without dephasing --- p.27 / Chapter 5.5 --- Second order correlation function without dephasing --- p.31 / Chapter 5.6 --- Interval distribution function with dephasing --- p.34 / Chapter 5.7 --- Second order correlation function with dephasing --- p.40 / Chapter 5.8 --- Effect of inhomogeneous broadening on g(2)(t) --- p.42 / Chapter 5.9 --- Third order correlation function --- p.43 / Chapter 5.10 --- Monte Carlo simulation --- p.44 / Chapter 5.11 --- Results and discussion --- p.46 / Chapter 5.11.1 --- Characteristics and implications of g(2)(t) --- p.46 / Chapter 5.11.2 --- "Characteristics and implications of g(3)(t1,t2)" --- p.47 / Chapter 6 --- Interval distribution function with random force models --- p.49 / Chapter 6.1 --- Impact collision model --- p.51 / Chapter 6.2 --- Modified diffusion model --- p.53 / Chapter 6.3 --- Difficulties in the calculation of g(2)(t) --- p.54 / Chapter 6.4 --- Kn as a measured quantity --- p.57 / Chapter 7 --- Conclusion --- p.59 / Chapter A --- Alternative derivation of k and higher order corrections --- p.62 / Chapter B --- Evaluation of integrals in the exponential --- p.70 / Chapter B.1 --- Integral of the form ∫ts + ∫vu --- p.70 / Chapter B.2 --- Integrals of the form ∫ts + ∫vu + ∫yz --- p.72 / Chapter C --- Evaluation of four-click events --- p.74 / Bibliography --- p.76
76

Multiscalar line measurements in nonisobaric high-pressure underexpanded supersonic jets using rotational-vibrational raman spectroscopy

Cohen, Benjamin Nathan 15 May 2009 (has links)
This work describes the development of a Raman spectroscopy system for measuring aerothermochemistry in high-speed jets and flames. A transmissive grating spectrometer was newly developed for capturing pure rotational Raman and rotationalvibrational Raman with a single CCD camera. Previous state-of-the-art experiments applied line imagining in known flowfields of constant pressure. The system described herein is designed to provide local measurement of pressure, with full thermochemistry, along a line. In every point, temperature will be measured by examining the Boltzmann decay of the rotational spectrum, while molar fraction will be measured from the vibrational Raman spectrum. The temperature and concentrations will then be combined to obtain partial pressure measurements via the equation of state. This work examines the phenomenology of rotational and vibrational Raman scattering and proposes algorithms that can be used for data extraction.
77

A Study Of Precoding Schemes For Ofdm Systems

Cakar, F.selcen 01 August 2008 (has links) (PDF)
We examine the effect of precoding on OFDM systems. The precoding operation, which is also known as constellation rotation, leads to a gain in diversity order for fading channels. In this thesis, we examine the effect of precoding for different receivers such as Maximum Likelihood (ML), Minimum Mean Squared Error (MMSE), and Zero Forcing (ZF) receivers. The diversity gain due to precoding comes at no cost of bandwidth expansion or power increase. Therefore it is an attractive and practical alternative. We also examine the precoding gain, when some reduction of rate is tolerable and compare the performance of rate reduced system with the uncoded system with the system which is coded by rateless unitary precoders, and with the hard-decision decoded BCH coded coded system.
78

Epitaxial graphene on silicon carbide: low-vacuum growth, characterization, and device fabrication

Sprinkle, Michael W. 04 June 2010 (has links)
In the past several years, epitaxial graphene on silicon carbide has been transformed from an academic curiosity of social scientists to a leading candidate material to replace silicon in post-CMOS electronics. This has come with rapid development of growth technologies, improved understanding of epitaxial graphene on the polar faces of silicon carbide, and new device fabrication techniques. The contributions of this thesis include refinement and improved understanding of graphene growth on the silicon- and carbon-faces in the context of managed local silicon partial pressure, high-throughput epitaxial graphene thickness measurement and uniformity characterization by ellipsometry, observations of nearly ideal graphene band structures on rotationally stacked carbon-face multilayer epitaxial graphene, presentation of initial experiments on localized in situ chemical modification of epitaxial graphene for an alternate path to semiconducting behavior, and novel device fabrication methods to exploit the crystal structure of the silicon carbide substrate. The latter is a particularly exciting foray into three dimensional patterning of the substrate that may eliminate the critical problem of edge roughness in graphene nanoribbons.
79

Untersuchung und Modellierung eines Dieselmotors zur Bestimmung von Verbrennungsmerkmalen aus der Motordrehzahl /

Schmidt, Thorsten, January 1900 (has links)
Originally presented as the author's Thesis--Universität Karlsruhe. / Includes bibliographical references.
80

Ensemble and single molecules fluorescence studies of polymers

Kim, Yeon Ho, 1973- 29 August 2008 (has links)
The effects of chain conformation on the photo-oxidation and green emission of poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) are investigated at both single molecule and ensemble levels. Single molecule studies reveal the conformation of PFO chains to be more globular when cast from THF than from toluene. Intensity transients of single molecules show that the elongated molecules cast from toluene have more fluctuations due to a fewer number of emitting centers on the polymer. Photochemical degradation leads to intensity fluctuations for the elongated molecules, while the globular chains show monotonic decays. Emission spectra of the single molecules show that photochemical oxidation leads to reduction in the emission of the molecule with no change in the emission spectra. No green emission is detected for single molecules indicating that formation of emissive ketone defects occurs rarely. Ensemble studies show that molecule cast from THF develop some green emission upon photodegredation while those cast from toluene don't. The increase in green in the globular molecules suggests that interchain contacts are necessary for the photochemical formation of emissive ketone defects in the PFO. All emission spectra of the aggregated and nonaggregated PFO during photooxidation are also analyzed by using a modified FranckCondon progression model with an additional independent Gaussian component and fitting results from single PFO spectrum. While emission spectrum of single PFO molecule shows a good fitting result to the model, the other two bulk PFO films display needs to introduce an additional term for better fit. This additional independent Gaussian component implies that green emission comes from non-Franck-Condon process. Rotational dynamics of poly(methyl acrylate) is investigated by single molecule spectroscopy. Polarized fluorescence transients from single rhodamine 6G dye embedded in polymer matrix above glass transition are analyzed and the correlation function of reduced linear dichroism is fit by a stretched exponential function. The fitting results suggest that non-exponential decay of correlation function. However, more rigorous study is needed because of the intrinsic statistical error of limited experimental data and the effect of high numerical objective.

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