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1
Cassady, Charles Richard. "The frequency distribution of availability." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09052009-040624/.
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Holman, Kevin W. "Distribution of an ultrastable frequency reference using optical frequency combs." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p3190346.
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Farahat, Sameer Ismail. "Electron energy distribution functions in radio-frequency discharges." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361940.
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XAVIER, GUILHERME BARRETO. "MODULATION SCHEMES FOR FREQUENCY CODED QUANTUM KEY DISTRIBUTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6483@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA criptografia quântica foi proposta como uma solução para o problema da distribuição de chaves criptográficas com segurança total garantida pelos princípios da mecânica quântica. Através dessa técnica é possível saber se um espião tentou interceptar a transmissão, o que é impossível utilizando técnicas de transmissão clássicas. Nesse trabalho foi feito um breve resumo da teoria de criptografia quântica, de suas técnicas de transmissão e dos problemas tecnológicos enfrentados. Foi analisada em detalhes a técnica de transmissão de qubits utilizando codificação de freqüência e feita uma comparação dos diferentes esquemas de modulação frente aos protocolos BB84 e B92. Foi demonstrado que os dois esquemas de modulação existentes (AM-AM e PM-PM) são na realidade equivalentes e foi proposto um novo esquema, o AM-PM o único que suporta o protocolo BB84 clássico. Medidas foram realizadas classicamente nos formatos AM-AM e AM-PM.
Quantum cryptography has been proposed as a solution to the cryptographic key distribution problem with absolute security guaranteed by the principles of quantum mechanics. Through this scheme it is possible to find out whether a spy tried to eavesdrop on the transmission, which was impossible to discover using classical transmission techniques. In this work a brief review of quantum cryptography theory, transmission techniques and technological problems involved were performed. It was analyzed in detail the transmission technique employing frequency coding, and a comparison was made between the different modulation schemes and the BB84 and B92 protocols. It was demonstrated that the two existing modulation formats (AM-AM and PM-PM) are in fact equivalent and a new format (AM-PM) was proposed, the only one able to accommodate classical BB84. Classical measurements were performed on the AM-AM and AMPM formats.
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Wilbur, Thomas M. "Energy distribution of Cerenkov radiation for finite frequency intervals." Thesis, Monterey, California. Naval Postgraduate School, 1987. http://hdl.handle.net/10945/22254.
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Tagluk, Mehmet Emin. "Time-frequency analysis of the ECG including optical processing." Thesis, University of Sussex, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388701.
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Guo, Wennan. "An ac-ac inverter for high frequency power distribution system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ59305.pdf.
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Hegazy, Yamen Mohammed. "Ruminant brucellosis in Egypt : frequency, distribution and potential control strategies." Thesis, Royal Veterinary College (University of London), 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558965.
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Ekmarker, Linda. "Frequency Control : Optimal distribution of FCR-N in real-time." Thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230897.
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Frequency control systems are used to keep the grid frequency at the nominal value of 50.00 Hz. Vattenfall employ hydropower plants for this purpose as they can easily adapt their production to counteract frequency deviations. This master thesis focuses on trying to improve Vattenfall’s mechanism to provide FCR-N (Frequency Containment Reserve in Normal operation) for primary frequency control, i.e. the turbine governor. The efforts are made to operate the plants more efficiently, decreasing distribution losses and thus increasing the profits. The current control system was modelled in MATLAB’s simulation tool Simulink to understand its complexity and to be used as base for comparison. Then a new model was developed based on the idea to introduce a global governor for the frequency control in each plant which controls the input signal to the individual turbine governors of each unit. OPT-data (tabulated data indicating how to operate a plant at the highest possible efficiency) was used to determine how to optimally distribute the FCR-N among the active units in a plant in real-time. The conclusions which can be drawn from this master thesis are that it is possible to make a more optimal distribution of FCR-N in real-time. However, it has not been possible to make a good comparison between the two models and the results regarding the profits which can be made by introducing this new type of governor are therefore inconclusive. It is of crucial importance to make a better match of the regulating strengths of the two models in order to perform the comparison. Improving the parameter values for the proportional and integral gains of the individual controllers and the precision of the OPT-table lookups may further improve the new model and also make it possible to perform a valid comparison between the two models.
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Becker, Emily Jones. "The frequency distribution of daily precipitation over the United States." College Park, Md. : University of Maryland, 2009. http://hdl.handle.net/1903/9226.
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Thesis (Ph.D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Atmospheric and Oceanic Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Xi, Huifeng. "Allele Fequency Distribution and Its Implication in Association Studies." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1226446329.
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Sucic, Victor. "Parameters Selection for Optimising Time-Frequency Distributions and Measurements of Time-Frequency Characteristics of Nonstationary Signals." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15834/.
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The quadratic class of time-frequency distributions (TFDs) forms a set of tools which allow to effectively extract important information from a nonstationary signal. To determine which TFD best represents the given signal, it is a common practice to visually compare different TFDs' time-frequency plots, and select as best the TFD with the most appealing plot. This visual comparison is not only subjective, but also difficult and unreliable especially when signal components are closely-spaced in the time-frequency plane. To objectively compare TFDs, a quantitative performance measure should be used. Several measures of concentration/complexity have been proposed in the literature. However, those measures by being derived with certain theoretical assumptions about TFDs are generally not suitable for the TFD selection problem encountered in practical applications. The non-existence of practically-valuable measures for TFDs' resolution comparison, and hence the non-existence of methodologies for the signal optimal TFD selection, has significantly limited the use of time-frequency tools in practice. In this thesis, by extending and complementing the concept of spectral resolution to the case of nonstationary signals, and by redefining the set of TFDs' properties desirable for practical applications, we define an objective measure to quantify the quality of TFDs. This local measure of TFDs' resolution performance combines all important signal time-varying parameters, along with TFDs' characteristics that influence their resolution. Methodologies for automatically selecting a TFD which best suits a given signal, including real-life signals, are also developed. The optimisation of the resolution performances of TFDs, by modifying their kernel filter parameters to enhance the TFDs' resolution capabilities, is an important prerequisite in satisfying any additional application-specific requirements by the TFDs. The resolution performance measure and the accompanying TFDs' comparison criteria allow to improve procedures for designing high-resolution quadratic TFDs for practical time-frequency analysis. The separable kernel TFDs, designed in this way, are shown to best resolve closely-spaced components for various classes of synthetic and real-life signals that we have analysed.
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Mai, Wei Xiong. "Time frequency distribution associated with adaptive Fourier decomposition and its variation." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2590643.
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Barke, Simon [Verfasser]. "Inter-spacecraft frequency distribution for future gravitational wave observatories / Simon Barke." Hannover : Technische Informationsbibliothek (TIB), 2015. http://d-nb.info/1081557958/34.
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Harding, John E. "Time frequency domain distribution and its application to reciprocating machinery analysis." Thesis, Monterey, California. Naval Postgraduate School, 1994. http://hdl.handle.net/10945/30565.
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Accurate assessment of shipboard machinery condition is essential in increasing the operational capability of naval vessels. Current shipboard machinery vibration monitoring and diagnostic procedures use frequency domain spectra to identify possible faults and problem areas. This method has proven to be inadequate for reciprocating machinery analysis. In reciprocating machinery the vibration signal is no longer a stationary, ergodic process, but is time-dependent and in some cases transient. This study proposes the use of Pseudo Wigner-Ville Distribution and introduces Wavelet analysis as two advanced methods for condition monitoring of non-stationary and transient shipboard machinery. These methods employ a time-frequency domain distribution for the detection of fault location and severity level. To demonstrate the benefits of a time-frequency representation, vibration data from two types of reciprocating air compressors will be processed for analysis. To simulate faulty conditions, constructed artificial fault signals will be introduced into the vibration data and analyzed. It is proposed Wavelet Analysis will play a complementary role to the Pseudo Wigner-Ville Distribution technique.
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Hizam, H. "Fault location on a distribution feeder using high frequency travelling waves." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403225.
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Wadden, David. "Rainfall distribution in the City of St. John's : temporal distribution, spatial variation, frequency analysis, and Tropical Storm Gabrielle /." Internet access available to MUN users only, 2002. http://collections.mun.ca/u?/theses,49727.
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Nguyen, Linh Trung. "Estimation and separation of linear frequency- modulated signals in wireless communications using time - frequency signal processing." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15984/.
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Signal processing has been playing a key role in providing solutions to key problems encountered in communications, in general, and in wireless communications, in particular. Time-Frequency Signal Processing (TFSP) provides eective tools for analyzing nonstationary signals where the frequency content of signals varies in time as well as for analyzing linear time-varying systems. This research aimed at exploiting the advantages of TFSP, in dealing with nonstationary signals, into the fundamental issues of signal processing, namely the signal estimation and signal separation. In particular, it has investigated the problems of (i) the Instantaneous Frequency (IF) estimation of Linear Frequency-Modulated (LFM) signals corrupted in complex-valued zero-mean Multiplicative Noise (MN), and (ii) the Underdetermined Blind Source Separation (UBSS) of LFM signals, while focusing onto the fast-growing area of Wireless Communications (WCom). A common problem in the issue of signal estimation is the estimation of the frequency of Frequency-Modulated signals which are seen in many engineering and real-life applications. Accurate frequency estimation leads to accurate recovery of the true information. In some applications, the random amplitude modulation shows up when the medium is dispersive and/or when the assumption of point target is not valid; the original signal is considered to be corrupted by an MN process thus seriously aecting the recovery of the information-bearing frequency. The IF estimation of nonstationary signals corrupted by complex-valued zero-mean MN was investigated in this research. We have proposed a Second-Order Statistics approach, rather than a Higher-Order Statistics approach, for IF estimation using Time-Frequency Distributions (TFDs). The main assumption was that the autocorrelation function of the MN is real-valued but not necessarily positive (i.e. the spectrum of the MN is symmetric but does not necessary has the highest peak at zero frequency). The estimation performance was analyzed in terms of bias and variance, and compared between four dierent TFDs: Wigner-Ville Distribution, Spectrogram, Choi-Williams Distribution and Modified B Distribution. To further improve the estimation, we proposed to use the Multiple Signal Classification algorithm and showed its better performance. It was shown that the Modified B Distribution performance was the best for Signal-to-Noise Ratio less than 10dB. In the issue of signal separation, a new research direction called Blind Source Separation (BSS) has emerged over the last decade. BSS is a fundamental technique in array signal processing aiming at recovering unobserved signals or sources from observed mixtures exploiting only the assumption of mutual independence between the signals. The term "blind" indicates that neither the structure of the mixtures nor the source signals are known to the receivers. Applications of BSS are seen in, for example, radar and sonar, communications, speech processing, biomedical signal processing. In the case of nonstationary signals, a TF structure forcing approach was introduced by Belouchrani and Amin by defining the Spatial Time- Frequency Distribution (STFD), which combines both TF diversity and spatial diversity. The benefit of STFD in an environment of nonstationary signals is the direct exploitation of the information brought by the nonstationarity of the signals. A drawback of most BSS algorithms is that they fail to separate sources in situations where there are more sources than sensors, referred to as UBSS. The UBSS of nonstationary signals was investigated in this research. We have presented a new approach for blind separation of nonstationary sources using their TFDs. The separation algorithm is based on a vector clustering procedure that estimates the source TFDs by grouping together the TF points corresponding to "closely spaced" spatial directions. Simulations illustrate the performances of the proposed method for the underdetermined blind separation of FM signals. The method developed in this research represents a new research direction for solving the UBSS problem. The successful results obtained in the research development of the above two problems has led to a conclusion that TFSP is useful for WCom. Future research directions were also proposed.
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Sandhu, Amritpal Singh. "Manipulating the frequency and distribution of genetic crossovers during meiosis in barley." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6316/.
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In commercial barley cultivars meiotic crossover (CO) distribution is skewed to the distal regions of the paired chromosomes. This restricts recombination to these regions thereby reducing the potential genetic variation that can be exploited in plant breeding programs. The aim of this project was to develop experimental strategies that will enable the frequency and distribution of meiotic crossovers to be modified in order to generate progeny with novel gene combinations. Treatment with the histone deacetylase inhibitor trichostatin A, led to significant modifications in crossover frequency in a concentration-dependent manner with lower concentrations not greatly impacting fertility, allowing for the extraction of fertile seeds. The genetic screening of a treated marker population at The James Hutton Institute (JHI), demonstrated subtle but significant shifts in the distribution of meiotic recombination, indicating that modifying recombination through chemicals applied via the transpiration stream is indeed feasible in barley and hence, possibly in other cereals. The cytological study of a barley desynpatic mutant \(des8\) in collaboration with JHI revealed that synapsis is normal despite reduced chiasma frequency. Genetic mapping studies are in progress to identify the mutant gene responsible for this phenotype which will help us to improve our current knowledge of meiosis in barley.
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Reis, Thaís Carolina Santos dos. "Extensões da Distribuição Weibull Aplicadas na Análise de Séries Climatológicas /." Presidente Prudente, 2017. http://hdl.handle.net/11449/152391.
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Orientador: Josmar MazucheliResumo: Na análise de séries climatológicas, a metodologia conhecida como “análise de frequências” inicia-se, após a verificação da validade de algumas suposições, pela escolha e ajuste de uma distribuição de probabilidade. A etapa mais importante desta análise é a escolha ou seleção da distribuição de probabilidade que melhor descreva o verdadeiro comportamento da variável em estudo. Uma vez adotada uma distribuição de probabilidade que esteja bem ajustada, segundo um ou vários critérios, é de interesse, por exemplo, estimar a probabilidade de que eventos de certa magnitude sejam igualados ou excedidos em T anos. O inverso desta probabilidade é chamado de período de retorno, sendo esta uma medida de extrema importância na avaliação de riscos associados a fenômenos climatológicos. Em princípio, qualquer distribuição de probabilidade com suporte nos números reais positivos pode ser utilizada na descrição do comportamento de séries fluviométricas, pluviométricas, eólicas, entre outras. Em se tratando de séries pluviométricas, formadas, por exemplo, pelas pluviosidades diárias, decendiais, mensais, trimestrais e anuais, as distribuições Gama e Weibull são as mais utilizadas. Nos últimos anos, a partir de métodos específicos, uma infinidade de novas distribuições vêm sendo propostas para a análise de observações contínuas e estritamente positivas, cujas aplicações, em sua grande maioria, restringem-se a dados de sobrevivência e confiabilidade. Nesta dissertação de Mestrado, foram avaliad... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In the climatological series analysis, a methodology known as “frequency analysis” begins, after the validity of some assumptions, by choice and adjustment of a probability distribution. The most important step of this analysis is the choice or selection of probability distribution that best describes the true behavior of the variable under study. Once a probability distribution, that is well adjusted according to one or several criteria, is adopted, it is of interest, for example, to estimate a probability of events of a certain magnitude that are matched or exceeded in T years. The opposite of this probability is called a return period, which is a measure of extreme importance in the evaluation of risks associated with climatological phenomena. In principle, any probability distribution supported by positive real numbers can be used to describe the behavior of fluviometric, pluviometric and wind series, among others. When it comes to the case of rainfall series, formed, for example, by daily, decendial, monthly, quarterly and annual rainfall, the Gamma and Weibull Distributions are more used. In recent years, from specific methods, a plethora of new distributions are being proposed for an analysis of continuous and strictly positive observations, which applications, for the most part, are restricted to survival and reliability data. In this Master’s dissertation, the performances of the Odd Weibull, Marshall-Olkin Weibull, Exponentiated Weibull and Transmutated Weibull Dist... (Complete abstract click electronic access below)
Mestre
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Kim, Youngtae. "Spatial resolution limits for the reconstruction of acoustic source distribution by inverse techniques." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274706.
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Ahmed, Tamer M. "Three-dimensional frequency-domain singularity distribution methods for seakeeping predictions : deficiencies and remedies." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405530.
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Michael, Michael Nasri. "Dynamic voltage and frequency scaling with multi-clock distribution systems on SPARC core /." Online version of thesis, 2009. http://hdl.handle.net/1850/10750.
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Lawson, Gareth L. "Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39220.
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Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2006.Includes bibliographical references (p. 297-311).
The physical and biological forces that drive zooplankton distribution and patchiness in an antarctic continental shelf region were examined, with particular emphasis on the Antarctic krill, Euphausia superba. This was accomplished by the application of acoustic, video, and environmental sensors during surveys of the region in and around Marguerite Bay, west of the Antarctic Peninsula, in the falls and winters of 2001 and 2002. An important component of the research involved the development and verification of methods for extracting estimates of ecologically-meaningful quantities from measurements of scattered sound. The distribution of acoustic volume backscattering at the single frequency of 120 kHz was first examined as an index of the overall biomass of zooplankton. Distinct spatial and seasonal patterns were observed that coincided with advective features. Improved parameterization was then achieved for a theoretical model of Antarctic krill target strength, the quantity necessary in scaling measurements of scattered sound to estimates of abundance, through direct measurement of all necessary model parameters for krill sampled in the study region and survey period.
(cont.) Methods were developed for identifying and delineating krill aggregations, allowing the distribution of krill to be distinguished from that of the overall zooplankton community. Additional methods were developed and verified for estimating the length, abundance, and biomass of krill in each acoustically-identified aggregation. These methods were applied to multi-frequency acoustic survey data, demonstrating strong seasonal, inter-annual, and spatial variability in the distribution of krill biomass. Highest biomass was consistently associated with regions close to land where temperatures at depth were cool. Finally, the morphology, internal structure, and vertical position of individual krill aggregations were examined. The observed patterns of variability in aggregation characteristics between day and night, regions of high versus low food availability, and in the presence or absence of predators, together reinforced the conclusion that aggregation and diel vertical migration represent strategies to avoid visual predators, while also allowing the krill access to shallowly-distributed food resources. The various findings of this work have important implications to the fields of zooplankton acoustics and Antarctic krill ecology, especially in relation to the interactions of the krill with its predators.
by Gareth L. Lawson.
Ph.D.
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Pagmar, David. "Frequency, Form, and Distribution of Illocutionary Speech Acts in Swedish Parent-Child Interaction." Thesis, Stockholms universitet, Institutionen för lingvistik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-131459.
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In this study, young children’s development of speech acts was examined. Interaction between six Swedish-speaking parents and their children was observed. The frequency, form and distribution of speech acts in the output from the parents were compared with the frequency, form and distribution of the children’s speech acts. The frequency was measured by occurrences per analysed session. The aim of the analysis was to examine if the parent’s behaviour could be treated as a baseline for the child’s development. Both the parents’ and the children’s illocutionary speech acts were classified. Each parent-child dyad was observed at four different occasions, when the children were 1;0, 1;6, 2;0, and 2;6 years of age. Similar studies have previously shown that parents keep a consistent frequency of speech acts within a given time span of interaction, though the distribution of different types of speech acts may shift, depending on contextual factors. The form, in terms of Mean Length of Speech Act in Words (MLSAw), were correlated with the longitudinal result of the children’s MLSAw. The distribution of the parents’ speech acts showed extensive individual differences. The result showed that the children’s MLSAw move significantly closer the MLSAw of their parents. Since the parent’s MLSAw showed a wide distribution, these results indicate that the parent’s speech acts can be treated as a baseline for certain aspects of the children’s development, though further studies are needed.
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Ahmed, Sara Mohamed. "Modeling of Power Electronics Distribution Systems with Low-frequency, Large-signal (LFLS) Models." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27787.
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This work presents a modeling methodology that uses new types of models called low-frequency, large-signal models in a circuit simulator (Saber) to model a complex hybrid ac/dc power electronics system. The new achievement in this work is being able to model the different components as circuit-based models and to capture some of the large-signal phenomena, for example, real transient behavior of the system such as startup, inrush current and power flow directionality. In addition, models are capable of predicting most low frequency harmonics only seen in real switching detailed models. Therefore the new models system can be used to predict steady state performance, harmonics, stability and transients. This work discusses the modeling issues faced based on the author recent experiences both on component level and system level. In addition, it recommends proper solutions to these issues verified with simulations.
This work also presents one of the new models in detail, a voltage source inverter (VSI), and explains how the model can be modified to capture low frequency harmonics that are usually phenomena modeled only with switching models. The process of implementing these different phenomena is discussed and the model is then validated by comparing the results of the proposed low frequency large signal (LFLS) model to a complete detailed switching model. In addition, experimental results are also obtained with a 2 kW voltage source inverter prototype to validate the proposed improved average model (LFLS model). In addition, a complete Verification, Validation, and Uncertainty Quantification (VV&UQ) procedures is applied to a two-level boost rectifier. The goal of this validation process is the improvement of the modeling procedure for power electronics systems, and the full assessment of the boost rectifier model predictive capabilities.
Finally, the performance of the new models system is compared with the detailed switching models system. The LFLS models result in huge cut in simulation time (about 10 times difference) and also the ability to use large time step with the LFLS system and still capture all the information needed. Even though this low frequency large signal (LFLS) models system has wider capabilities than ideal average models system, it still can’t predict all switching phenomena. Therefore, another benefit of this modeling approach is the ability to mix different types of models (low frequency large signal (LFLS) and detailed switching) based on the application study they are used for.Ph. D.
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Kalyoncu, Ozden. "Noise Reduction In Time-frequency Domain." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608768/index.pdf.
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In this thesis work, time-frequency filtering of nonstationary signals in noise using Wigner-Ville Distribution is investigated. Continuous-time, discrete-time and discrete Wigner Ville Distribution definitions, their relations, and properties are given.
Time-Frequency Peak Filtering Method is presented. The effects of different parameters on the performance of the method are investigated, and the results are presented.
Time-Varying Wiener Filter is presented. Using simulations it is shown that the performance of the filter is good at SNR levels down to -5 dB. It is proposed and shown that the performance of the filter improves by using Support Vector Machines.
The presented time-frequency filtering techniques are applied on test signals and on a real world signal. The results obtained by the two methods and also by classical zero-phase low-pass filtering are compared. It is observed that for low sampling rates Time-Varying Wiener Filter, and for high sampling rates Time-Frequency Peak Filter performs better.
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Vermelho, Alexandre Filipe Correia Cajana. "Calculating best estimates in a GLM framework. Frequency/severity models vs total loss models." Master's thesis, Instituto Superior de Economia e Gestão, 2014. http://hdl.handle.net/10400.5/7040.
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Mestrado em Ciências ActuariaisWhen using generalized linear models to predict future claim payments, should actuaries use separate frequency/severity models or a single loss cost model? This is the question this paper addresses, covering some theoretical background, testing both alternatives on real data from the Industrial Multiple Risks (IMR) sub-‐branch and analysing its results. Data was provided by 7 companies operating in Portugal in the years 2010 and 2011, who own a 70% share of the Portuguese IMR market and was collected by Associação Portuguesa de Seguradores (APS).
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Akhanli, Deniz. "Radar Range-doppler Imaging Using Joint Time-frequency Techniques." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608325/index.pdf.
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Inverse Synthetic Aperture Radar coherently processes the return signal from the target in order to construct the image of the target. The conventional methodology used for obtaining the image is the Fourier transform which is not capable of suppressing the Doppler change in the return signal. As a result, Range-Doppler image is degraded. A proper time-frequency transform suppresses the degradation due to time varying Doppler shift.
In this thesis, high resolution joint-time frequency transformations that can be used in place of the conventional method are evaluated. Wigner-Ville Distribution, Adaptive Gabor Representation with Coarse-to-Fine search algorithm, and Time-Frequency Distribution Series are examined for the target imaging system.
The techniques applied to sample signals compared with each other. The computational and memorial complexity of the methods are evaluated and compared to each other and possible improvements are discussed. The application of these techniques in the target imaging system is also performed and resulting images compared to each other.
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Antaloae, C. C. "Feasibility of high frequency alternating current power distribution for the automobile auxiliary electrical system." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/6792.
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This study investigates the feasibility and potential benefits of high frequency
alternating current (HFAC) for vehicle auxiliary electrical systems.
A 100Vrms, 50kHz sinusoidal AC bus is compared with 14V DC and 42V DC electrical
systems in terms of mass and energy efficiency. The investigation is focused on the four
main sub-systems of an on-board electrical network, namely: the power generation,
power distribution, power conversion and the electrical loads. In addition, a systemlevel
inquiry is conducted for the HFAC bus and a comparable 42V DC system.
A combination of computer simulation, analytical analysis and experimental work has
highlighted benefits for the HFAC power distribution sub-system and for low-torque
motor actuators. Specifically, the HFAC conductor mass is potentially 70% and 30%
lighter than comparable 14V DC and 42V DC cables, respectively. Also, the proposed
cable is expected to be at least 80% more energy efficient than the current DC
conductor technology. In addition, it was found that 400Hz AC machines can
successfully replace DC motor actuators with a rated torque of up to 2Nm. The former
are up to 100% more efficient and approximately 60% lighter and more compact than
the existing DC motors in vehicles. However, it is argued that the HFAC supply is not
feasible for high-torque motor actuators. This is because of the high energy losses and
increased machine torque ripple associated with the use of HFAC power.
The HFAC power conversion sub-system offers benefits in terms of simple power
converter structure and efficient HFAC/DC converters. However, a significant limitation
is the high power loss within HFAC/AC modules, which can be as high as 900W for a
2.4kW load with continuous operation. Similar restrictions are highlighted for the
HFAC power generation sub-system, where up to 400W is lost in a 4kW DC/HFAC
power module.
The conclusion of the present work is that the HFAC system offers mass and energy
efficiency benefits for the conventional vehicle by leveraging the use of compact lowtorque
motor actuators and lightweight wiring technology.
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Hesarkazzazi, Sina. "Stationary vs. non-stationary modeling of flood frequency distribution across North West England (UK)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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As environmental change is happening at an unprecedented pace, a comprehensive and holistic approach is needed in order to mitigate the increasing negative effect of extreme natural events occurring based on the natural and anthropogenic variations. Of all the geophysical phenomena, flooding is one of the most catastrophic events, leading to quite a few losses and damages across the World. Recent extraordinary flood events happened in north – western England, precisely sequences of the severe floods in the county of Cumbria, Lancashire and Manchester in 2004, 2009 and 2015, have brought many concerns not only for the residents but also for the community of hydrologists in UK. These extreme events in these areas comparing with their typical river discharge values have raised an important question of whether any significant changes in the magnitude of river flows can be detected as a result of natural/human - induced clime change. If so, whether they can be attributed to any meteorological predictors such as rainfall frequency analysis. The results, performed for 39 river gauging stations based on annual maxima (AM) approach, indicate that around 92% of the river gauging stations show non – stationary behaviour; whereas only in 8%, stationarity is dominant. More importantly, annual rainfall is deemed as the best explanatory variable to express the variability of our data much better than other covariates for a vast majority of stations (around 60%).
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Mehra, Arun 1967. "An approximate method for determining the frequency dependent current distribution in a ground plane." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278176.
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This MS thesis proposes a methodology to compute a frequency dependent current distribution for a ground plane with the ultimate aim of utilizing this current distribution to compute the plane parasitics. A iterative finite differencing technique is utilized to solve a two dimensional diffusion equation for the current distribution on the plane. Starting with an initial DC current density over the entire plane grid, the frequency dependent current density is obtained by imposing the necessary boundary conditions and allowing the current to redistribute itself over the plane. An iterative procedure based on simultaneous over relaxation is employed to get faster convergence. This method takes into account the presence of sources, sinks and holes on the plane. Finally the plane parasitics are computed using integral methods and energy considerations.
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Rödiger, Jasper. "Time-Frequency Quantum Key Distribution: Numerical Assessment and Implementation over a Free-Space Link." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21046.
Full textAbstract:
Die Quantenschlüsselverteilung (QKD), die erste anwendbare Quantentechnologie, verspricht informationstheoretisch sichere Kommunikation. In der vorliegenden Arbeit wurde das Zeit-Frequenz (TF)-QKD-Protokoll untersucht, das Zeit und Frequenz, nämlich Puls-Positionsmodulation (PPM) im Zeitbereich und Frequenzumtastung (FSK) im Frequenzbereich als die beiden komplementären Basen verwendet. Seine Sicherheit beruht den Quanteneigenschaften von Licht und auf der Zeit-Frequenz-Unschärferelation.
TF-QKD kann mit größtenteils Standard-Telekommunikationstechnologie im 1550-nm-Band implementiert werden. Die PPM-Basis kann mit Modulatoren und die FSK-Basis mit Hilfe der Wellenlängenmultiplex-Technologie realisiert werden. Das TF-QKD-Protokoll ist in der Lage, ein beliebig großes Alphabet bereitzustellen, was mehr als 1 bit/Photon ermöglicht. Darüber hinaus ist es robust gegenüber athmosphärischen Störungen und somit für die Übertragung über den Freiraumkanal geeignet.
In der vorliegenden Arbeit wird das TF-QKD-Protokoll theoretisch bewertet, mit Standardkomponenten für 1 bit/Photon implementiert und die Freiraumübertragung mit optischem Tracking über eine 388 m Teststrecke wird bei Tageslicht demonstriert. Unter Verwendung der vorhandenen Komponenten konnte eine sichere Schlüsselrate von 364 kbit/s back-to-back und 9 kbit/s über den Freiraumkanal demonstriert werden.Quantum key distribution (QKD), the first applicable quantum technology, promises information theoretically secure communication. In the presented work the time-frequency (TF)-QKD protocol was examined, which uses time and frequency, namely pulse position modulation (PPM) in the time domain and frequency shift keying (FSK) in the frequency domain as the two complementary bases. Its security relies on the quantum properties of light and the time-frequency uncertainty relation. TF-QKD can be implemented mostly with standard telecom-technology in the 1550 nm band. The PPM basis can be implemented with modulators and the FSK basis with help of wavelength-division multiplexing technology. The TF-QKD protocol is capable of providing an arbitrarily large alphabet enabling more than 1 bit/photon. Moreover, it is robust in the atmosphere making it suitable for transmission over the free-space channel. In the present work the TF-QKD protocol is assessed theoretically, implemented with off-the-shelf components for 1 bit/photon and free-space transmission with optical tracking over a 388 m testbed is demonstrated in daylight. Using components at hand, secret key rates of 364 kbit/s back-to-back and 9 kbit/s over the free-space channel could be demonstrated.
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Takuno, Tsuguhiro. "High Frequency Switching of SiC Transistors and its Applications to In-home Power Distribution." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157586.
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Brauer, Patrik. "High-Frequency Voltage Distribution Modelling of a Slotless PMSM from a Machine Design Perspective." Thesis, KTH, Elkraftteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224174.
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The introduction of inverters utilizing wide band-gap semiconductors allow for higher switching frequency and improved machine drive energy efficiency. However, inverter switching results in fast voltage surges which cause overvoltage at the stator terminals and uneven voltage distribution in the stator winding. Therefore, it is important to understand how next generation machine drives, with higher switching frequency, affect the voltage distribution. For this purpose, a lumped-parameter model capable of simulating winding interturn voltages for the wide frequency range of 0-10 MHz is developed for a slotless PMSM. The model includes both capacitive and inductive couplings, extracted from 2D finite element simulations, as well as analytically estimated resistive winding losses. The developed model of a single phase-winding is used to investigate how machine design aspects such as insulation materials and winding conductor distribution affects both voltage distribution and winding impedance spectrum. Validation measurements demonstrate that the model is accurate for the wide frequency range. The sensitivity analysis suggests that the winding conductor distribution affect both impedance spectrum and voltage distribution. For the slotless machine, capacitance between the winding and the stator is several times smaller than capacitance between turns. Therefore, the high-frequency effects are dominated by the capacitance between turns. Insulation materials that affect this coupling does therefore have an impact on the impedance spectrum but does not have any significant impact on the voltage distribution.Nästa generations inverterare för styrning av elektriska maskiner, baserade på bredbandgaps komponenter, tillåter högre switchfrekvenser vilket skapar en energieffektivare drivlina. Nackdelen är att snabba spänningsflanker från den höga switchfrekvensen skapar överspänning på stators anslutningar och en ojämn spänningsfördelning i statorlindningen. Det är därför betydelsefullt att förstå hur dessa nya drivlinor påverkar lindningens spänningsfördelning. I denna rapport används en modell kapabel att simulera lindningens spänningsfördelning i det breda frekvensspektrumet 0-10 MHZ. Modellen är framtagen för en faslindning av en PMSM, utan statoröppning, som inkluderar både kapacitiva och induktiva kopplingar samt analytiskt beräknade lindningsförluster. Modellen används för att undersöka spänningsfördelningen i lindningen samt inverkan från designparametrar som isolationsmaterial och lindningsdistribution. Känslighetsanalysen visar att lindingsdistributionen har en signifikant påverkan på både impedansspektrumet och spänningsfördelningen. För den studerade maskintypen är det kapacitansen mellan varv som är dominerande för högfrekventa fenomen. Isolationsmaterial som påverkar denna koppling har en påverkan på impedansspektrumet men är liten för spänningsfördelningen.
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Oliveira, Fernandes Moreira P. M. "Timing signals and radio frequency distribution using ethernet networks for high energy physics applications." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1461109/.
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Timing networks are used around the world in various applications from telecommunications systems to industrial processes, and from radio astronomy to high energy physics. Most timing networks are implemented using proprietary technologies at high operation and maintenance costs. This thesis presents a novel timing network capable of distributed timing with subnanosecond accuracy. The network, developed at CERN and codenamed “White- Rabbit”, uses a non-dedicated Ethernet link to distribute timing and data packets without infringing the sub-nanosecond timing accuracy required for high energy physics applications. The first part of this thesis proposes a new digital circuit capable of measuring time differences between two digital clock signals with sub-picosecond time resolution. The proposed digital circuit measures and compensates for the phase variations between the transmitted and received network clocks required to achieve the sub-nanosecond timing accuracy. Circuit design, implementation and performance verification are reported. The second part of this thesis investigates and proposes a new method to distribute radio frequency (RF) signals over Ethernet networks. The main goal of existing distributed RF schemes, such as Radio-Over-Fibre or Digitised Radio-Over-Fibre, is to increase the bandwidth capacity taking advantage of the higher performance of digital optical links. These schemes tend to employ dedicated and costly technologies, deemed unnecessary for applications with lower bandwidth requirements. This work proposes the distribution of RF signals over the “White-Rabbit” network, to convey phase and frequency information from a reference base node to a large numbers of remote nodes, thus achieving high performance and cost reduction of the timing network. Hence, this thesis reports the design and implementation of a new distributed RF system architecture; analysed and tested using a purpose-built simulation environment, with results used to optimise a new bespoke FPGA implementation. The performance is evaluated through phase-noise spectra, the Allan-Variance, and signalto- noise ratio measurements of the distributed signals.
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Pavlov, Garcia Olivia C. "Intentional Control of Cognitive Dynamics." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1446547138.
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Slagmolen, Bram Johannes Jozef, and BRAM SLAGMOLEN@ANU EDU AU. "Direct Measurement of the Spectral Distribution of Thermal Noise." The Australian National University. Faculty of Science, 2005. http://thesis.anu.edu.au./public/adt-ANU20051128.104552.
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This thesis investigates the direct measurement of the thermal noise spectral distribution.
Long base line gravitational wave detectors, being commissioned around
the world, are limited in sensitivity in the intermediate frequencies by the thermal
noise. These detectors are utilising suspended test mirrors for the detection of gravitational
waves by measuring their relative displacement. One of the fundamental
noise sources in these detectors is the thermally induced displacement of the suspension
onto and within the mirrors. This thermally induced motion of the test mirrors
limits the displacement sensitivity of the gravitational wave detectors. Knowledge
of the spectral behavior of thermal noise over a wide frequency range will improve
predictions and understanding of the behavior of the suspension and test mirrors.¶
In this thesis the direct measurement of the thermal noise spectral distribution
of a mechanical flexure resonator is described. The mechanical flexure resonator is
an unidirectional ’wobbly table’ made from copper-beryllium, which hinges around
four thin flexures 15 mm wide, 1 mm high and ~116 µm thick. The mechanical
flexure resonator has a resonant frequency of 192 Hz, with a quality factor of ~3000.¶
The thermal noise induced displacement of the mechanical flexure resonator was
measured using an optical cavity. The end mirror of a two mirror optical cavity was
mounted on the mechanical flexure resonator. A laser was made resonant with the
test cavity by use of a locking control system. Thermal noise induced displacement
moved the test cavity away from resonance. By measuring the error-signal in the
control system, the equivalent thermal noise displacement was obtained.¶
The thermal noise induced displacement of the mechanical flexure resonator was
predicted to be in the order of 10^(−12) to 10^(−17) m/sqrtHz over a frequency range of
10 Hz to 10 kHz. All other external noise sources needed to be suppressed to below
this level. A major noise source was the laser frequency fluctuations. When the
test cavity was locked to the laser, the laser frequency fluctuations dominated the
read out signal. To suppress the frequency fluctuations, the laser was locked to a
rigid long optical reference cavity. This allowed the frequency fluctuations to be
suppressed to below the equivalent thermal noise displacement of the test cavity
over the frequency range of interest.¶
Acoustic noise was suppressed by placing the whole experiment inside a vacuum
chamber, and evacuating the air inside the chamber down to a pressure level of
10^(−4) mbar. A seismic vibration isolation system was used to suppress the seismic
noise in the laboratory to below 10^(−14) m/sqrtHz at frequencies above 4 Hz.¶
With the experimental set up, the thermal noise displacement of the mechanical
flexure resonator has been measured. Due to the degradation of the isolator performance,
measurement of the thermal noise behavior over a wide frequency range of
the mechanical flexure resonator was unsuccessful. By using an analytical curve fitting
routine around the fundamental and first order resonant modes of the resonator,
a loss factor of (3.5 ± 1.5 − 3.7 ± 1.5) × 10^(−4) for the copper-beryllium mechanical
flexure resonator was obtained and structural damping was inferred.
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Roy, Jyotirmoy. "Effects of ancillary service markets on frequency and voltage control performance of deregulated power systems." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/j_roy_112607.pdf.
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Narasimha, Pavan. "TRACKING R-R INTERVAL DYNAMICS BETWEEN MEN AND WOMEN DURING ORTHOSTASIS USING TIME-FREQUENCY DISTRIBUTION." UKnowledge, 2007. http://uknowledge.uky.edu/gradschool_theses/458.
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To track evolution of autonomic responses during orthostasis in men and women, we used discrete pseudo-Wigner distribution based time-frequency analysis to compute dominant frequencies and spectral powers in RR intervals and Systolic Blood Pressure (SBP). Data were collected from 38 healthy volunteers (22 men, 16 women) during 10 min supine posture followed by 30 min of 700 head up tilt. The RR intervals were computed from ECG and systolic blood pressure was and spectral amplitudes of RR intervals were integrated in two regions viz., Low Frequency (LF) region defined between 0.05-0.15 Hz and High Frequency region (HF), sometimes referred to as respiratory frequency region, defined as mean breathing frequency of the individual +/- one standard deviation. Dominant frequencies of RR intervals in the LF region decreased in both men and women. There were no significant differences between men and women as far as the SBP data were concerned for the dominant frequencies, however women had higher values than men. Dominant frequencies of RR intervals in the HF region increased both in men and women from supine to tilt. No significant differences in dominant frequencies were found between men and women. Also there were no significant differences even for the SBP data, however men had higher values than women Integrated powers within the auto spectra of RR showed that in the HF region, power decreased significantly for both men (pandlt;0.005), and women (pandlt;0.001) during tilt compared to supine. However, the HF power in women was significantly higher for men during both supine (pandlt;0.001), and tilt (pandlt;0.005). In LF region integrated power spectrum showed no significant difference between men and women although women showed a slight increase from supine to tilt. These results suggest that men have a higher sympathetic control while women have greater para-sympathetic influence.
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Mattejat, Peter Paul. "Frequency analysis of low flows: comparison of a physically based approach and hypothetical distribution methods." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/101453.
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Several different approaches are applied in low flow frequency analysis. Each method's theory and application is explained. The methods are (1) physically based recession model dealing with time series, (2) log-Pearson type III and mixed log-Pearson type III using annual minimum series, (3) Double Bounded pdf using annual minimum series, (4) Partial Duration Series applying truncated and censored flows.
Each method has a computer program for application. One day low flow analysis was applied to 15 stations, 10 perennial streams and 5 intermittent streams. The physically based method uses the exponential baseflow recession with duration, initial recession flow, and recharge due to incoming storm as random variables, and shows promise as an alternative to black box methods, and is appealing because it contains the effect of drought length. Log-Pearson is modified to handle zero flows by adding a point mass probability for zero flows. Another approach to zero flows is the Double Bounded probability density function which also includes a point mass probability for zero flows. Maximum likelihood estimation is used to estimate distribution parameters. Partial Duration Series is applied due to drawbacks of using only one low flow per year in annual minimum series. Two approaches were used in Partial Duration Series (i) truncation, and (ii) censorship which represent different low flow populations. The parameters are estimated by maximum likelihood estimation.M.S.
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Liang, Zhibang. "High impedance fault detection in power distribution systems with impedance-based methods in frequency domain." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59530.
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High Impedance Faults (HIFs) in electrical distribution systems generally present serious public safety hazards, utility liability problems and equipment damage due to a risk of arcing ignition of fires. However, it is extremely difficult to detect HIFs in electrical distribution systems by conventional overcurrent relays or fuses because they do not generate enough fault current to be detectable. This thesis presents a new detection scheme for HIFs in electrical distribution systems based on observing the harmonic content in the one-sided amplitude spectrum of the impedance. The proposed new HIF detection algorithm can distinguish HIF events from other non-fault events with current waveforms that similar to HIF current waveforms. Four simulation cases have been tested in this thesis to verify the new HIF detection algorithm. The simulation results indicate a potential ability to establish a high impedance fault detection function block in BC Hydro’s distribution system protective devices.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Le, Ngoc Tuan. "Optimisation of sludge pretreatment by low frequency sonication under pressure." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0129/document.
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L'objectif de ce travail est d'optimiser le prétraitement de boues par des ultrasons de puissance (US) à basses fréquences, et en particulier d‘étudier pour la première fois des améliorations possibles en modifiant la pression hydrostatique, et la fréquence jusqu’à l’audible. Après un examen préliminaire des conditions du procédé (conditionnement des boues, type de boues, alcalinisation préalable, contrôle de la température), les effets des paramètres ultrasonores (puissance, intensité, énergie spécifique, fréquence) et de la pression hydrostatique ont été spécifiquement étudiés, séparément et simultanément, d’abord à température constante (28°C), puis sans refroidissement. On a ainsi vérifié que l’énergie spécifique joue un rôle clé dans la désintégration des boues sous US (i.e. solubilisation de la matière organique) et que l'élévation de température pendant la sonication adiabatique est bénéfique grâce aux effets combinés d’hydrolyse thermique et de cavitation. Pour une énergie spécifique donnée, une faible fréquence (12 kHz contre 20 kHz) et une haute puissance améliorent la solubilisation de la matière organique grâce à une cavitation plus violente, tandis qu’on observe un optimum de pression hydrostatique en raison de ses effets opposés sur le seuil et l'intensité de la cavitation. Un résultat important est que la pression optimale dépend de l’intensité ultrasonore et du profil de température, mais pas de l’énergie spécifique, ni de la fréquence, ni du type de boues. Après avoir fixé les conditions les plus favorables (soit 12 kHz, 360 W, 28 gTS/L et conditions adiabatiques), l‘optimisation finale a fourni la pression de travail (3,25 bar) et les paramètres du mode séquentiel (US ON/OFF, permettant d‘éviter de hautes températures qui amortissement l‘intensité de la cavitation et peuvent endommager le transducteur). Ces conditions ont permis d‘atteindre un rendement d’extraction de la DCO très élevé, mais n’améliorent que faiblement le rendement ultérieur de méthanisationThe objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc.), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (PUS) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield
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Schrama, Judith Marije. "High-frequency magneto-conductivity studies of low-dimensional organic conductors." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365779.
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Hamaguchi, Fujihito. "The effect of static ear canal air pressure on the time-frequency analysis of transient evoked OTO-acoustic emissions." Ohio University / OhioLINK, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1177441506.
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Chiwaya, A. A. W. "Polarised polyphase current differential protection for distribution feeder circuits using a digital voice frequency communications channel." Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760664.
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Kerslake, Christopher Wayne. "A method for analyzing the delivery frequency from a distribution center to a retail grocery store." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33321.
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Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2005.Includes bibliographical references (leaves 67-68).
Currently, no adequate method exists for determining how frequently a retail store in a supermarket chain should receive deliveries from its distribution center. Existing methods neglect many crucial constraints, such as the necessity for deliveries to fall on fixed days of the week, severely limited shelf space, and the inability for many stores to hold additional overstock product in a backroom. This paper addresses the problem by outlining a new method for determining the delivery frequency by developing a simulation model for the replenishment process of a supermarket chain. The model can also be used to provide insight into other aspects of the replenishment process, such as shelf space allocation, and reorder rules. Using this model, we were able to show that significant cost savings were available to the supermarket chain we worked with on the project by changing the delivery schedules for their stores.
by Christopher Wayne Kerslake.
M.Eng.in Logistics
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Boucher, Guillaume. "Biphoton Frequency-Correlations Engineering and Measurement with a Semiconductor Microcavity." Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC071.
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Ce travail porte sur l'ingénierie et la caractérisation des propriétés temps-fréquence de paires de photons générées par une source semiconductrice. Ce dispositif utilise la conversion paramétrique à température ambiante pour émettre des paires de photons se propageant dans des directions opposées et aux longueurs d'onde télécom. Une microcavité intégrée à la source permet d'augmenter l'efficacité de l'interaction nonlinéaire par résonance du champ de pompe transverse. Nous présentons la théorie de la conversion paramétrique dans cette source et nous montrons comment les propriétés spatiales et spectrales du faisceau de pompe influencent les propriétés des photons, en particulier leur degré d'intrication en fréquence, permettant un ingénierie souple. La variété d'états pouvant être produits est illustrée à l'aide de l'amplitude spectrale jointe. Deux techniques permettant la caractérisation de l'intensité spectrale jointe ont été implémentées. La première est un spectrographe à photons uniques ; la seconde, basée sur la stimulation du processus de conversion paramétrique, a permis une amélioration dramatique de la résolution et du temps d'intégration. Les deux approches ont permis la démonstration de l'ingénierie des corrélations en fréquences en variant la taille et la courbure du faisceau de pompe. Des exemples d'états plus exotiques et une méthode pour caractériser leur fonction de Wigner chronocyclique sont étudiés théoriquement. La relation entre les propriétés temps-fréquence et le degré d'intrication en polarisation de la paire est aussi exploréeThis work is focused on the engineering and characterization of the frequency-time properties of photon pairs generated with a semiconductor source. This device emits photons propagating in opposite directions at telecom wavelengths using spontaneous parametric down-conversion at room temperature. A microcavity integrated in the source allows the resonance of the transverse pump beam, enhancing the efficiency of the nonlinear interaction. We give a theoretical description of the down-conversion process in the source and we show how the spatial and spectral properties of the pump beam impact the properties of the photons, in particular their degree of entanglement in frequency allowing a versatile engineering. The variety of states that can be produced is illustrated using the Joint Spectral Amplitude. Two techniques allowing the characterization of the Joint Spectral Intensity have been implemented. The first one is a single photon spectrograph. The second one, based on the stimulation of the down-conversion process showed a dramatic improvement in terms of resolution and integration time. Both techniques allowed the demonstration of the frequency correlation engineering by varying the waist and curvature radius of the pump beam. Examples of more exotic states and a technique to characterize their chronocyclic Wigner function are theoretically investigated. The relationship between time-frequency properties and degree of entanglement in polarization of the biphoton is also explored
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Chen, Xiaojun. "Multiple Scattering from Bubble Clouds." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_theses/36.
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Multiple scattering effects from bubble clouds are investigated in this study. A high performance, general purpose numerical tool for multiple scattering calculations is developed. This numerical tool is applied in three computational scenarios in this study. The total scattering cross section of a bubble cloud is investigated. Numerical results indicate that the resonant frequency of the bubble cloud is much lower than that of a single bubble. The variation of resonant frequency of multiple scattering is also studied. It is found that the resonant frequency decreases as the number of bubbles increases, or as the void fraction of the bubble cloud decreases. Phase distributions of bubble oscillations in various multiple scattering scenarios are presented. It is found that, at resonance, the bubbles synchronize to the same phase, which is indicative of the lowest mode of collective oscillation. At wave localization, half of the bubbles oscillate at phase 0 while the other half oscillate at phase Pi. An intuitive interpretation of this behavior is given.
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Exley, Katherine Ann. "Structure, frequency and distribution of P elements in relation to P-M hybrid dysgenesis in Drosophila melanogaster." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279706.
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