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1
Terrier, Benoit. "Flow characteristics in straight compound channels with vegetation along the main channel". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6326.
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This study investigates the complex flow structure generated by riparian emergent vegetation along the edge of floodplain. Detailed velocity and boundary shear stress measurements were carried out for various arrangements of emergent rigid cylindric rods of 3 mm, 6 mm and 9 mm diameters and for three different rod densities. In addition, the impact of foliage on the flow field was assessed during a series of experiments where brushes were used instead of smooth rods. The results of these new experiments are first presented. In addition to the laboratory data, field data was obtained through Acoustic Doppler Current Profiler measurements for two flood events in a stretch of the river Rhône that can be approximated to a straight compound channel with vegetated banks. The analysis of the flow structure highlights the presence of strong secondary circulation and increased vorticity on the river banks. The rods on the edge of the floodplain increase significantly flow resistance, reducing velocity and decreasing boundary shear stress. Flow rate was seen to decrease with increasing vegetative density for all cases except when foliage was added. This suggests that an optimum threshold density, for which a smaller density would lead to an increased flow rate might exist. Wakes trailing downstream of the vegetation stem, planform coherent structures advected between the main channel and the floodplain, and eddying motion in the flow due to enhanced turbulence anisotropy are among the defining patterns observed in the studied compound channel flows with one line of emergent vegetation along the edge of the floodplain. The Shiono and Knight Method (SKM) was modified in order to account for the increased turbulence activity due to the rods. The drag force term was introduced in the same way as in the work of Rameshwaran and Shiono (2007). However, a new term was added to the transverse shear stress term in the form of an Elder formulation, incorporating a friction drag coefficient which can be derived from the experimental data. In this proposed version, the advection term was set to zero. Another version of the SKM, similar to Rameshwaran and Shiono (2007), was also tested with the addition of a local drag friction only applied in the rod region. The proposed SKM version without the advection term was favored as it can be more closely related to the experimental data and to physical processes. Finally, the capabilities of Telemac-2D were tested against the experimental data for various turbulence models. The Large Eddy Simulation turbulence model highlighted some unsteady flow patterns that were observed during experiments, while satisfactorily predicting the lateral velocity and boundary shear stress distributions.
2
Gorman, Robert William Carleton University Dissertation Geography. "Sea ice characteristics of the Parry Channel". Ottawa, 1988.
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3
Taparugssanagorn, A. (Attaphongse). "Evaluation of MIMO radio channel characteristics from TDM-switched MIMO channel sounding". Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514286506.
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Abstract
The present dissertation deals with the evaluation of multiple-input multiple-output (MIMO) radio channel characteristics from time-division multiplexing (TDM)-switched MIMO channel sounding. The research can be divided into three main areas. First, the impacts of phase noise in TDM-switched MIMO channel sounding on channel capacity are studied. Second, we focus on those impacts on channel parameter estimation using the SAGE algorithm. And in the last part, spatial correlation, channel eigenvalue distribution, and ergodic capacity in realistic environments are analyzed.
The rationale behind the first two areas is that most advanced MIMO radio channel sounders employ the TDM technique, which has significant problems from phase noise of the TX and RX phase locked loop (PLL) oscillators causing measurement errors in terms of estimated channel capacity and parameters. We propose statistical models that reproduce the capacity estimates. The effects of the sounding mode (SM), the length of pseudo-random noise (PN) sequence L of the sounding signal, and the system size are disclosed. The distinctive basis is to consider the impact of the actual phase noise in TDM switched MIMO channel sounding, instead of assuming white Gaussian-type phase noise. In a reality, the short-term phase noise component affecting one measurement cycle of a MIMO system plays an important role in the traditional estimators of the radio channel parameters and capacity. We show that the performance impairment is less than that been under the hypothesis of uncorrelated white Gaussian phase-noises samples. The difference is due to the non-vanishing correlation of phase-noise within the measurement cycle. Two approaches to mitigating the impact of phase noise are proposed. The former is the simple and efficient sliding averaging method, where the signal-to-noise ratio (SNR) of the channel impulse response can be increased. The latter is the choice of SM and L, which is more thorough. In the second part, two approaches to mitigating its impact on channel parameter estimation using the SAGE algorithm are also discussed. Besides the sliding averaging, which in general can increase the SNR, the new SAGE algorithm based channel parameter estimation based on the improved signal model accounting for the phase noise in the measurement device is proposed. Finally, the channel eigenvalue distribution and ergodic capacity based on complex hypergeometric functions and their asymptotic characteristics are analyzed. It is shown that the derived theoretical expressions closely approximate the simulated results of the measured finite-dimensional MIMO channels. The spatial correlation and the eigenvalue statistics in frequency selective channels for single and dual polarized antennas are investigated. This knowledge is useful when different MIMO and beamforming techniques are applied.
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Pottkotter, Andrew A. "Maximizing Channel Capacity based on Antenna and MIMO Channel Characteristics and its Application to Multimedia Data Transmission". University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1430317210.
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SUGIURA, Yoshie, Takaya YAMAZATO, Masaaki KATAYAMA e 正昭 片山. "Measurement of Narrowband Channel Characteristics in Single-Phase Three-Wire Indoor Power-Line Channels". IEEE, 2008. http://hdl.handle.net/2237/11152.
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Green, Edward. "Propagation characteristics of a narrowband microcellular radio channel". Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480724.
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Fahmi, Ahmed Ismat. "Molecular characteristics of the cardiac sodium channel subunits". Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621334.
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Ottosson, Anton, e Viktor Karlstrand. "Gaussian Process Methods for Estimating Radio Channel Characteristics". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-289449.
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Gaussian processes (GPs) as a Bayesian regressionmethod have been around for some time. Since proven advant-ageous for sparse and noisy data, we explore the potential ofGaussian process regression (GPR) as a tool for estimating radiochannel characteristics.Specifically, we consider the estimation of a time-varyingcontinuous transfer function from discrete samples. We introducethe basic theory of GPR, and employ both GPR and its deep-learning counterpart deep Gaussian process regression (DGPR)for estimation. We find that both perform well, even with fewsamples. Additionally, we relate the channel coherence bandwidthto a GPR hyperparameter called length-scale. The results show atendency towards proportionality, suggesting that our approachoffers an alternative way to approximate the coherence band-width.Gaussiska processer (Gaussian processes,GPs) har länge använts för Bayesiansk regression. Då de visat sigfördelaktiga för gles och brusig data utforskar vi möjligheternaför GP-regression (Gaussian process regression, GPR) som ettverktyg för att estimera egenskaper hos radiokanaler.Isynnerhetbetraktasskattningaventidsvarierandeöverföringsfunktion utifrån diskreta samplingar. Vi presenterarden grundläggande teorin kring GPR, och använder både GPRoch dess djupinlärningsmotsvarighet DGPR (deep Gaussian pro-cess regression) för skattning. Båda ger goda resultat, även när samplingarna är få. Utöver detta så relaterar vi koherens-bandbredden hos en radiokanal till en hyperparameter i GPR-modellen. Resultaten visar på en tendens till proportionalitet,vilket antyder att vår metod kan användas som ett alternativt sätt att approximera koherensbandbredden.
Kandidatexjobb i elektroteknik 2020, KTH, Stockholm
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Lundberg, Oscar. "Channel Characteristics Variations from Switching Between Narrow Beams". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65628.
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The demand for higher throughput and lower latency in telecommunication systems is growing. Upcoming telecommunication systems will operate at higher frequencies (above 15 GHz) compared with previous systems (below 6 GHz). Antenna arrays will be employed in upcoming systems for increased link budget (coverage) and multiple input multiple output channels. This implies that narrow beams will be used. Beam tracking and beam steering is necessary to follow the user equipment. It is hypothesised that changing beam direction changes the channel condition for the communication link. In this work beam changes in data gathered with a 5G testbed is analysed at both 15 GHz and 28 GHz. The results show that the channel is indeed affected by beam changes. Statistical results of the conducted analysis are presented followed by specific examples on how the channel is affected by the beam changes. Knowledge on how the channel is affected by beam changes is of interest when designing systems for beam selection. The results show a nearly threefold increase of rank changes immediately after a beam change at 15 GHz. The probability for a rank change up or down is found to be equal. At 28 GHz the metric used for channel richness is singular value ratio. The statistical results show that the difference in singular value ratio before and after a beam change is increased by a factor 2. It is also shown that grating lobes may have a significant effect on the channel richness when changing beam direction.
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Yilmaz, Emre. "Algorithms for estimating reverberation characteristics for single channel dereverberation". Thesis, KTH, Signalbehandling, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168016.
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Speech enhancement systems achieving a joint suppression of reverberation and background noise can be used in digital hearing aids, voice controlled systems or hands-free telephony. Demanding requirements for computational complexity, signal delay and speech quality must be fulfilled in order to achieve a satisfactory performance. The speech quality depends on how accurate the reverberation characteristics such as the reverberation time or the spectral variance of the late reverberant speech are estimated. In this thesis, an efficient algorithm for a blind reverberation time estimation based on maximum likelihood approach is introduced. The new algorithm allows to estimate reverberation times from a much wider range with acceptable accuracy. Variance of the late reverberant speech is another important quantity in dereverberation systems. Two late reverberant spectral variance estimation methods are compared with regard to estimation accuracy and computational complexity. Finally, the performance of the considered speech enhancement system is analyzed with the improved reverberation time estimator.
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Tin, Tin Htwe. "Bed Deformation and Navigable Channel Characteristics in Braided Stream". Kyoto University, 2018. http://hdl.handle.net/2433/235073.
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Halo, Issufo F. M. "The Mozambique Channel eddies : characteristics and mechanisms of formation". Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/6477.
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Includes abstract.Includes bibliographical references.
The model outputs and the satellite data have shown a number of cyclonic and anticyclonic eddies being generated within the Mozambique Channel. The eddies were identified using a newly designed eddy detection algorithm. The algorithm has shown that cyclonic eddies appeared to be more ubiquitous than the anticyclonic and had a single mode sizedistribution. On the other hand, the anticyclonic eddies seemed to have a favorite site for their formation, and have shown a bi-modal size-distribution.
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Zhang, Qian. "Wireless Near-ground Channel Characteristics in Several Unlicensed Bands". Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1219170596.
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Gangadharan, Divya. "Simulation Study of Device Characteristics and Short Channel Effects of Nanoscale Germanium Channel Double-Gate MOSFETs". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1226530654.
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Tamjidi, Mohammad R. "Characteristics of N-channel accumulation mode thin film polysilicon mosfets. /". Full text open access at:, 1987. http://content.ohsu.edu/u?/etd,132.
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Scott, Christopher L. "Channel and recipient characteristics effects on communication effectiveness and performance /". Online access for everyone, 2008. http://www.dissertations.wsu.edu/Dissertations/Spring2008/c_scott_042108.pdf.
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Cottrell, Graham Trevor. "Functional characteristics of heterogeneous Cx40/Cx43 gap junction channel formation". Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279862.
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Cells of the cardiovascular system express multiple connexins (Cx) with Cx40 and Cx43 being commonly coexpressed in many tissues. The expression levels of connexins are dynamic and can vary in response to a growth stimulus. It is not clear why cells express multiple connexins, or what advantage such dynamic regulation of expression patterns have on cell function. These issues are further complicated by the ability of some connexins to interact to form heterogeneous gap junction channels, with little being known regarding functional properties of such channels. The purpose of these experiments was threefold: (1) To determine whether Cx40 and Cx43 are capable of interacting to form heteromeric/heterotypic gap junction channels; (2) To characterize the functional properties of Cx40/Cx43 heteromeric/heterotypic channels; and (3) To determine the effect that changing Cx40:Cx43 expression ratio has on functional properties of heteromeric/heterotypic channels. Cell lines were developed that express only Cx43 (Rin43), Cx40 (Rin40), and Cx40 and Cx43 in varying Cx40:Cx43 expression ratios (6B5n, A7r5, A7r540C1, and A7r540C3). The Cx40:Cx43 expression ratios in the 6B5N, A7r5, A7r540C1, and A7r540C3 cells are approximately 1:1, 3:1, 5:1, and 10:1, respectively. Functional properties of the gap junction channels formed between these cells were determined using both electrophysiological and dye coupling techniques. Pairing of Rin43 and Rin40 cells demonstrated that Cx40 and Cx43 are capable of forming homomeric/heterotypic gap junctions with unique voltage-dependent gating and single channel behaviors. Rin43/A7r5 cell pairs displayed voltage-dependent gating and single channel conductance profiles that could only be explained by the presence of heteromeric/heterotypic gap junction channels between these cells. Pairing Rin43 cells with coexpressing cells of high Cx40:Cx43 expression ratio resulted in channel activities that were not predicted by the gating and conductance patterns of Cx40/Cx43 heterotypic channels. However, the dye coupling characteristics of these same cells in coculture demonstrated that the permeability of the channels formed between these cell types reflected that of Cx40 channels. In summary, Cx40 and Cx43 are capable of forming heteromeric/heterotypic gap junction channels. Increasing the Cx40:Cx43 ratio in coexpressing cells results in channels with unique gating and conductance properties, however dye permeability of these cells is predicted by their relative Cx40 content. Therefore, varying Cx40:Cx43 expression ratio provides cells with a mechanism to finely control the types of molecules shared between cells.
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Karabatsos, Christos P. Carleton University Dissertation Engineering Electrical. "Investigation of the gate capacitance characteristics of short channel MOSFETs". Ottawa, 1989.
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Wang, Ping Carleton University Dissertation Engineering Systems and Computer. "A study of indoor radio propagation channel characteristics by simulation". Ottawa, 1995.
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RON, CARLOS VINICIO RODRIGUEZ. "WIDEBAND RADIO CHANNEL CHARACTERISTICS AT 3,5 GHZ IN URBAN REGIONS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=32622@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O correto planejamento de novas redes de comunicação sem fio de voz e dados representa um grande desafio ao incluir serviços cada vez mais avançados com diferentes requisitos de qualidade, suporte a mobilidade, altas taxas de transmissão e capacidades de tráfego elevadas. Os ambientes nos quais estas redes operam são dos mais diversos e contemplam desde na áreas abertas até centros urbanos com alta densidade de edificações. O presente trabalho apresenta resultados experimentais que permitem caracterizar o canal de radio-propagação num ambiente urbano com mobilidade do receptor. Como resultado de campanhas de medições, são identificados modelos do canal que permitem ao projetista da rede definir a melhor configuração de parâmetros e critérios de projeto para a implantação de uma rede móvel de acesso sem fio em banda larga. As medições foram realizadas nos bairros da Gávea, Leblon e Lagoa, no Rio de Janeiro, com estação transmissora instalada na PUC-Rio (prédio LEME) na frequência de 3,5 GHz, destinada para novos serviços móveis. Os principais resultados obtidos são: o desenvolvimento de uma metodologia de medição simples e precisa, utilizando a técnica OFDM, e das ferramentas de software para pré-processamento e analise de dados; o desenvolvimento de modelos semi-empíricos para a previsão da perda média de propagação; a obtenção de perfis de retardo do canal e dos valores médio e desvio padrão do retardo em condições de visibilidade (LOS) e obstrução (NLOS), e de expressões empíricas para sua estimativa; a obtenção do valor médio das amplitudes relativas dos multipercursos e sua modelagem em função do valor de retardo relativo.
Best practices of radio planning for new wireless networks with mixed trac of voice and data are a big technical challenge due to the need to provide of advanced services with different quality requirements, high data throughput, mobility and high traffic demands. Environments for operation of this kind of networks are diverse and include open areas with low population density as well as urban centers. This thesis presents experimental results obtained to characterize the wideband radiopropagation channel on urban environments with a mobile receiver. The analysis of measured data allows the identification of channel models and propagation mechanisms needed for the design engineer to define the best parameter configuration and project criteria in the deployment of a wideband mobile wireless network. The measurement campaign was executed on Gavea neigborhood in Rio de Janeiro city with a transmitter station located in a PUC-Rio university building (Lcme Building) operating at 3,5 GHz, frequency used for the new wideband mobile services. The main results are: the development of a simple and precise methodology for measuring, using the OFDM technique OFDM, and the software tools for pre-processing and analysis; the development of semi-empirical models for predicting the average propagation loss in the urban environment; measurements of multipath delay profiles of the channel and the average values and standard deviation of the RMS delay spread in visibility (LOS) and obstruction (NLOS) conditions, and derivation of empirical expressions for their estimation; measurements of the average values of multipath amplitudes its modeling in function of the relative delay.
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Pai, Guruprasad. "5 GHz Wireless Channel Characteristics on The Ohio University Campus". Ohio University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1190390609.
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Chan, Morgan Hing-Lap. "Communication channel characteristics and behaviour of intrabuilding power distribution circuits". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25081.
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Intrabuilding power distribution circuits offer a number of unique advantages for local area networking. To enable the selection of proper error-control codes and protocols for reliable data communication services, error pattern statistics of intrabuilding power line channels are obtained. Also, error-causing disturbances are identified and their relationships to specific types of error patterns are determined. It is found that error occurrence is highly periodic, with periodicity being a function of the power line frequency which is nominally 60Hz in North America. Furthermore, results indicate that error pattern behaviour is relatively insensitive to communication carrier frequency and modulation schemes.
Based on the measurement results, hybrid ARQ with bit-interleaving is suggested for reliable data transmission at high data rate (19,200bps). Burst error correcting codes can be used to reduce decoder cost and complexity with some sacrifices in performance. At lower data rates (1,200bps or below), effective error control can be accomplished more easily.
Finally, the attenuation characteristics of a number of typical power line channels are presented. It is found that high frequency bypass can be used to improve signal transmission between different phases of the distribution transformer.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Welsh, Susan A. "Hydrodynamic characteristics of countercurrent gas-pseudoplastic liquid two-phase channel flow". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/16923.
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Kironoto, Bambang Agus. "Turbulence characteristics of uniform and non-uniform, rough open-channel flow /". [S.l.] : [s.n.], 1993. http://library.epfl.ch/theses/?nr=1094.
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Torriano, Federico. "Investigation of the 3D flow characteristics in a rotating channel setup". Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/23957/23957.pdf.
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Chen, Xi Mei. "Channel characteristics and communication performance of galvanic coupling human body communication". Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691880.
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Taylor, Daniel. "Channel Fulfillment Characteristics, Retail Network Structure and Buy-Online-Ship-From-Store Performance: Inventory Behavior and Channel Service Implications". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531426717885577.
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Karlis, Alexandros K., Fotios K. Diakonos, Christoph Petri e Peter Schmelcher. "Fermi acceleration induces self-organized critical characteristics to the driven Lorentz channel". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183123.
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Fares, Youssef Ramsis. "Effects of cut-off (flood relief) channel intersection on bend flow characteristics". Thesis, University of Glasgow, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254320.
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Michaelidou, Nina. "The role of individual, product and channel characteristics in brand switching behaviour". Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/105609/.
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In consumer research, variety-seeking has been recognised as a major cause of exploratory purchase behaviour and specifically brand switching. A major contribution from Hoyer and Ridgway (1984) examines the circumstances under which brand switching occurs as a result of the internal need for variety isolating other external factors (such as out-of-stock conditions and promotional activities) which also motivate brand switching. The authors’ theoretical model proposes that the occurrence of brand switching is a function of two factors; individuals difference characteristics and product characteristics. The present thesis proposes that in today’s retailing environment, with the proliferation in shopping channels, the increase in non-store retailing and the rise of the Internet, a third factor that of the ‘channel’ is likely to influence brand switching behaviour. A ‘channel’ factor is added to the original model of Hoyer and Ridgway (1984) and it is posited that channel characteristics (e.g. channel involvement, channel perceived risk, channel loyalty channel similarity and hedonism in channels) as well as the individual difference characteristics and product characteristics (proposed in the original model) will have an influence on brand switching behaviour. The new framework is tested in the context of consumer shopping for clothes in both store and non-store retailing environments (e.g. retail store, catalogue and the Internet), measuring consumer individual characteristics and perceptions of product and channel characteristics to clarify the nature of channel characteristics, their interaction and finally determine the influence of the three factors (individual, product and channel) on brand switching. A questionnaire is used (administered online) for a sample drawn from a company’s database. The data analysis involves a number of techniques including factor and reliability analyses for summarising the data and correlation and regression analyses for investigating associations among variables. Results indicate no linear relationships between brand switching and the three factors, although a number of conclusions are reached which emphasise the role of the ‘channel’ in consumer behaviour research.
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Kim, Yeonsu. "Probabilistic Estimation of River Discharge Considering Channel Characteristics Uncertainty with Particle Filters". 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/180482.
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Keogh, Darren Paul. "An experimental investigation on the flow characteristics of open-channel slot flow". Thesis, Edinburgh Napier University, 2000. http://researchrepository.napier.ac.uk/Output/4273.
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Shrestha, Sanjeet. "WAKE CHARACTERISTICS DOWNSTREAM OF A RIGID UNSUBMERGED CYLINDER IN A RECTANGULAR CHANNEL". OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1379.
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Wakes form when a fluid flows past stationary objects. Within the wake, the velocity of the fluid is reduced, that is, there is a velocity defect. Limited information is available for predicting the magnitude of the velocity defects and the width of wakes that form behind rigid cylinders in open-channel flows. Therefore, the objective of this study is to develop relationships for predicting wake geometry downstream of a rigid unsubmerged cylinder. This study was conducted in a 0.46-m-wide rectangular channel with either medium sand (median size, d50 = 0.33 mm) or fine gravel (d50 = 6.35 mm) bed material. A wooden dowel (6.35 mm to 38.1 mm in diameter) was used as a rigid cylinder. Point velocity data was collected for varied hydraulic conditions; the data was used to compute the maximum velocity defect (umax) and half-width of the wake (2b1/2) at sections located different distances downstream from the cylinder (&Deltax). The data were also used to compute parameters for models that predict umax and 2b1/2 as a function of x. It was expected that the study results would yield two equations: one for predicting umax and 2b1/2; instead, the parameters varied with cylinder size and bed material. Since the results were not as expected, evaluation tests were performed to determine why the parameters varied. The evaluation tests (pump configuration tests, point-velocity repetition-tests, point-velocity sampling-time tests, and boundary-layer-development tests) revealed that the turbulent boundary layer (the layer of fluid where the effects of viscosity are significant) was not fully developed in most of the sections where point velocity data was collected. In addition, it was determined that the point-velocity sampling-time of 100 s was not sufficient for keeping the velocity measurement within 2% of the long-term mean velocity (the mean velocity based on a 500-s sample); to achieve this goal it is recommended that a 200-s sampling time should be used.
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Karlis, Alexandros K., Fotios K. Diakonos, Christoph Petri e Peter Schmelcher. "Fermi acceleration induces self-organized critical characteristics to the driven Lorentz channel". Diffusion fundamentals 20 (2013) 52, S. 1-2, 2013. https://ul.qucosa.de/id/qucosa%3A13625.
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TERAGUCHI, Hiroshi. "Study on Hydraulic and Morphological Characteristics of River Channel with Groin Structures". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/151951.
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Law, Eugene L. "Estimating the Characteristics of the Aeronautical Telemetry Channel during Bit Error Events". International Foundation for Telemetering, 1999. http://hdl.handle.net/10150/608759.
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International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, NevadaThis paper presents estimated aeronautical telemetry channel characteristics during bit error events. A T-39 aircraft was flown around various test corridors while transmitting a filtered 10 Mb/s pseudo-noise (PN) sequence binary phase shift keying (BPSK) signal. The received signal was down converted to 70 MHz, digitized when trigger criteria were met, and stored for later analysis. Received signal strength was also recorded. The first step in data analysis consisted of dividing the fast Fourier transform (FFT) of the recorded signal by the FFT of the expected signal. The received signal strength data was then used to correct for flat fade effects. The resulting signal is the difference (dB) between the expected signal at the receiver intermediate frequency (IF) output and the measured receiver IF output during the error event. This difference is the aeronautical telemetry channel characteristic. The characteristics of this difference signal were then matched against a 2-ray and 3-ray multipath fading model with reflected signal amplitude and path delay as the variables.
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CHUAN-YI, WANG, e 王傳益. "Characteristics of Rapid Channel Flow". Thesis, 2000. http://ndltd.ncl.edu.tw/handle/41654387074265020694.
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博士國立中興大學
土木工程學系
88
ABSTRACT The Fiber-optic Laser Doppler Velocimetry (FLDV) was adopted in this experimental study to investigate the characteristics of the rapid channel flow over smooth and rough boundaries. In this study, the effects of aspect ratio (ratio of channel width to depth), channel bed slope and vertical position on the flow were analyzed. The Reynolds Stress Model (RSM) was used to predict various parameters for the rapid channel flow. Both the two-dimensional and the three-dimensional flows were discussed. Most of the experiments conducted in this study belonged to supercritical flow. The main items analyzed in this research were the mean velocity profiles, the turbulence intensities, and the Reynolds stress of the rapid channel flow. The measured velocity profiles were compared with the law of the wall, the velocity defect law, the power law, and Chiu’s velocity theorem. The velocity profiles for conditions with the maximum point velocity occurred both on (α=1) and below (α< 1) the water surface were discussed. The measured distributions of the turbulence intensities and the Reynolds stress were analyzed and compared with the results of Nezu and Rodi (1986), and Tominaga and Nezu (1992). The measured mean velocity profiles for the outer region (y/H > 0.2 ) compared well with the velocity defect law for the smooth bed when α=1. The Chiu’s velocity theorem gave fair prediction for the smooth bed when α< 1. The power law fitted the measured mean velocity profiles well for the smooth and rough beds, including the conditions with the maximum point velocity occurred both on and below the water surface. The measured longitudinal turbulence intensities for the rapid channel flow over the smooth bed were consistent with Nezu and Rodi’s (1986) model. A modified model, however, provided a better prediction for the rapid channel flow over the rough bed. The measured vertical turbulence intensities can be estimated by a modified model proposed in this study for both the smooth bed and the rough bed channels. When the maximum point velocity located on the water surface (α=1), the measured Reynolds stress distributions for both the smooth and the rough bed channels can be expressed by a theoretical expression for the two dimensional flow. When the maximum point velocity located below the water surface (α< 1), the peak of measured Reynolds stress decreased with an increase of the channel slope for the smooth bed, and it tended to increase with an increase of the channel slope due to the secondary flow effect for the rough bed channel. The mean velocity profiles simulated by the Reynolds Stress Model (RSM) were better than those by the standard model for both the smooth and the rough bed channel flows. The simulated vertical turbulence intensities by the RSM were consisted with the measured data, and the simulated longitudinal turbulence intensities were lower than the experimental results. The predicted spanwise turbulence intensities by the RSM were consistent with the results of Nezu’s (1977) model except for the rough bed channel flow with low aspect ratio. In addition, a preliminary study for the characteristics of the deep narrow natural river flow was also performed. It was found that the amount of depression for the point of maximum velocity below the water surface increased with a decrease of the aspect ratio, which was consistent with the results of the laboratory experiment.
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Ching, Hao-hui, e 程瀚輝. "A Co-relation Study of Consumer Characteristics and Consumer Internet Shopping Tendency Toward Channels—Channel Characteristics and Product Characteristics as Moderating Variables". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/65948628393656869579.
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碩士世新大學
企業管理研究所(含碩專班)
98
The latest changes in the consumer’s purchase behavior shed light on the importance of the on-line shopping. It is even more significant, thanks to the up-to-date broadband and wireless technology for the popular internet environment. In fact, the revenue is declined in traditional 3C physical channel after the financial crisis in 2008. On the contrary, the virtual on-line shopping business remains relatively strong. It’s no wonder that more and more traditional companies are entrance on-line shopping business. The on-line shopping behaviors vary depending on a variety of the consumer and channel characteristics, as well as the products. Therefore, this study is to understand what factors are important for consumers when switch from traditional physical channel to on-line shopping environment. In this research, it would be easier to create a better on-line shopping environment to attract the target audience who has interest shopping. There a lot of interaction elements between the traditional physical channel and the virtual shopping businesses during consumer behavior shift. This study of motivation is base on consumer characteristic of factor that determines the individual purchase behavior with scholastic theories. It’s summarizes several factors related to the decision-making process during shopping 3C products in on-line environment to demonstrate the hypotheses in terms of questionnaire methodology. Meanwhile, the purpose of this study to understand there are have any characteristics of relationship between product, sell channel, and consumer in which to selected on-line shopping environment, especially for 3C products. Sampled by the students and official workers of population in Taipei area, the survey released 400 copies of questionnaires, while 350 copies were written, 5 of them were void and 345 copies were valid. The overall return rate is 86.25%. This survey shows that influence factors of consumer characteristic are shift when select on-line purchase for 3C products. Eventually, those firms should to understand relationship of characteristics between consumer and product in on-line shopping behavior and to constitute a better on-line shopping environment to attract consumer willing purchase it.
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Haque, AKM Enamul. "Some characteristics of open channel transition flow". Thesis, 2009. http://spectrum.library.concordia.ca/976403/1/MR63268.pdf.
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Flow separation is a common phenomenon in decelerated subcritical flows as in open channel expansions. A highly distorted velocity and shear stress distribution due to flow separation can lead to a continuous reduction of energy and trigger an adverse pressure gradient resulting in flow separation. This causes loss of energy and hydraulic efficiency of the systems. An experimental investigation was conducted with the use of a gradual rising hump on the bed of an expansion in a rectangular open channel. Besides the hump, split vanes in the flow field were also used to reduce the expansion angle and in turn reduce the adverse effect of flow separation. These modifications resulted in a relatively more uniform velocity and shear stress distribution in the transition and in the channel downstream of the expansion. A laboratory model of rectangular open channel transition expanding was constructed with Plexiglas plates. It facilitated the measurement of the flow velocity and turbulence characteristics with the aid of Laser Doppler Anemometer (LDA). The total divergent angle of the transition was 19.78 degrees. Velocities were measured along the x, y and z directions, positioning the LDA from both the bottom and the side of the channel. Two humps with gradual linear rises of 12.5 mm and 25 mm were used. A second device included the use of a single vane and a three vane splitter plates system formed with thin Plexiglas plates. Mainly velocity distributions, with and without humps and the splitter vanes were the results sought. The variations of energy and momentum coefficients were analyzed to find the effectiveness of the devices used in the transition to control flow separation. As a small addition to the study, the use of computational fluid dynamics (CFD) to predict the flow characteristics of open channel was also undertaken. Due to their lower time demand and lower cost, these numerical methods are preferred to experimental methods after they are properly validated. In the present study, the CFD solution is validated by experimental results. A limited number of CFD simulations were completed using the commercial Software ANSYS-CFX. In particular, mean velocity distributions for the rectangular open channel transitions were used for model validation. To this end, the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations and the two equations k-[varepsilon] models were used. The validation of the model using test data was reasonable.
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Li, Chen-Hao, e 李振豪. "Hydraulic Characteristics in Meandering Compound Channel Flow". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/72328434063793394793.
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碩士國立嘉義大學
土木與水資源工程學系研究所
94
In natural rivers, the flow courses are almost meandering and their cross sections are compound type. Due to the interaction between the main channel and the flood plain, the flow structure and the hydraulic characteristics of meandering compound channel flow are extremely complicated. Flume tests were used to investigate the hydraulic characteristics of meandering compound channel with overbank flow. Three dimensional electromagnetic current and wave gauge were used to measure velocity and stage respectively. In addition, the visualization technique was used to capture and interpret the surface flow behavior. The difference in direction of rotation of the flow before and after inundation at a bend section was clearly observed by velocity measurement. At the middle section of the crossing reach, there was a secondary cell in the main channel due to the flow form flood plain plunging into the main channel. The core flow in the upper layer of the main channel occurred near convex side at a bend and at middle in crossing reach. According to the visualization technique results, the flow which from flood plain plunged into the main channel will flow in the core flow region in the main channel while the water depth was not deep. As the water depth increased, the flow both in the main channel and in the flood plain will flow parallel to the boundary of the flood plain. For experimental results of velocity profile in the main channel, the power law used for simulating primary velocity profile in the main channel is found to be quite inadequate.
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Chen, Cheng Chung, e 陳振中. "Measurements and Simulation for Microcellular channel characteristics". Thesis, 1998. http://ndltd.ncl.edu.tw/handle/05278277662572018076.
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碩士國立臺灣大學
電機工程學系
86
This study use narrowband and wideband measurements system to measure radio propagation mechanism. On the narrowband measurement, we put the transmitted antenna on high and low position respectively. We observe the power fading phenomena, compare the power distribution to Rayleigh and Rician distribution, and discuss the space selective diversity. Moreover, we discuss the influence when the electromagnetic wave were obstructed. On the wideband measurement, we have done two parts of measurements. Part 1, we separate the direct wave, reflection, diffraction, and scattering. And compare with simulation result to discuss the difference between them. Part 2, we focus on the measurement of tree attenuation, and apply the result to explain the influence by tree in narrowband measurement.
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Lin, Chih-Yu, e 林致佑. "Characteristics of the Human Body Channel and Design the Human Body Channel Transceiver". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/g2qz5k.
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碩士國立中正大學
資訊工程研究所
103
In recent years, the wearable devices or personal healthcare devices for biomedical applications to build up the body area network (BAN) become more and more popular. Traditional electronic medical devices such as ECG, EMG, thermometers, and sphygmomanometers are quite large and require wire line connection. Therefore, human body communication (HBC) uses the human body skin as a transmission medium to replace wire line connection. As compared to wireless transmission methods, HBC is more stable and has less power attenuation. Furthermore, it is almost insensitive to the motion of the human body. However, the body antenna effects cause interferences in human body channel communication. Moreover, the transmission distances, signal frequencies, and power attenuations must be considered in building up a human body channel model. In this thesis, the human body channel characteristics are measured by an analog front-end (AFE) PCB board. The AFE board consists of a voltage gain amplifier (VGA) and a Schmitt trigger. The measured transmission distance is 10 cm, 40 cm, and 140 cm. The measured frequency ranges from 1 MHz to 80 MHz. In addition, the jitter of the received signal is also measured to build up a human body channel model. Finally, a wideband signaling (WBS) transceiver is proposed according to the measured human body channel characteristics. In the transmitter part, the NRZI-encoded data are sent directly to the human body channel. In the receiver part, after an AFE board amplified the received signals and recovered them back to digital waveform, a clock and data recovery (CDR) circuit recovers the signals and clock with jitter and frequency drift tolerance.
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Chien-Hung, Chen. "Channel Characteristics and Modeling for Wireless Communication System". 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0002-2408200613055600.
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Tang, Shiang-Guo, e 唐相國. "Analysis and Measurement of MIMO Radio Channel Characteristics". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/65180842173153463384.
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碩士國立臺灣大學
電信工程學研究所
90
This thesis introduces a new structure for improving the transmitted data capacity in fixed bandwidth — the multiple-input multiple-output (MIMO) communication system, which is composed of two antenna arrays at both ends of the transmission link. The MIMO communication system exploits the low correlation among radio channels that is caused by rich multipath environment and transmits several kinds of data simultaneously with less interference. For further investigation of MIMO channel features, first we constructed a measurement platform for detecting the characteristics of MIMO channels. By the eigenanalysis and waterfilling capacity distribution method, the statistical feature of MIMO channels can be obtained. We found that the number of significant (available) 4x4 MIMO channel gain in indoor is larger than that in picocell case because the effect of multipath; the total capacity with 10% outage is around 25~30bits/s/Hz in indoor compared with 15~20bits/s/Hz in picocell scenario. In microcell scenario, for larger spatial coverage the RUSK channel sounder was exploited for measurement. Although the error that resulted from the difference of SIMO and MIMO system existed, the phenomenon that capacity when LOS exists is smaller than that in NLOS case can still be observed.
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Hung-PinChiu e 邱宏彬. "Investigation on channel characteristics and fish habitat use". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7j4uw4.
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博士國立成功大學
水利及海洋工程學系
106
After Typhoon Morakot, dredging engineering was conducted while taking the safety of humans and structures into consideration, but some stream reaches were formed in multiple-channel sections in Cishan Stream because of anthropogenic and natural influences. This study mainly explores the distribution of fish species (Hemimyzon formosanus, Rhinogobius nantaiensis, Acrossocheilus paradoxus, Onychostoma alticorpus) in both multiple- and single-channel sections in Cishan Stream. Some of the environments did not exhibit significant differences according to a one-way ANOVA comparing multiple- and single-channel sections, but certain areas of multiple-channel sections had more diverse habitats. Fish species was widely distributed by non-metric multidimensional scaling in multiple-channel sections as compared to those in single-channel sections. In addition, according to the principal component analysis, fish species has a preferred environment, and all of them have a wide choice of habitat environments in multiple-channel sections. This shows that the existence of multiple-channel sections could significantly affect the existence of the fish species under consideration in this study. However, no environmental factors were found to have an influence on fish species in single-channel sections, with the exception of H. formosanus. The results of this study found that multiple-channel sections after dredging activities could improve fish habitat environments as compared to single-channel sections. Because the fish assemblages and environments are not fully recovered in Cishan Stream from 2009 to 2014, this study identified suitable habitat environments for fish species in multiple-channel sections. In the future, if it is necessary to carry out dredging engineering again, it is recommended that multiple-channel section can be adopted to favor the recovery of fish.
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Chen, Chien-Hung, e 陳建宏. "Channel Characteristics and Modeling for Wireless Communication System". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/15035105585626124402.
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博士淡江大學
電機工程學系博士班
94
The main purpose of this thesis is to research on channel characteristics for wireless communications and present the bit error rate (BER) performance analysis for high-speed personal communication service in multipath environment. This thesis has three parts. The first part, a new indoor path loss prediction model is proposed. The second part, the BER performance analysis for high-speed personal communication service in different multipath environments is investigated. The third part is the impulse responses calculation for ultra-wide band (UWB) indoor communication. In office environment, a novel prediction model for small rooms with metallic furniture is proposed. Both the propagation loss and the diffraction loss have been considered in this model. The receiver power prediction from the transmitter to the receiver antenna is predicted based on the layout of the environment. The advantages of this model are less computational load and high accuracy. It is not necessary to trace every path compared with the ray-tracing technique. However, all wireless systems must be able to deal with the challenges of operating over a multipath propagation channel, where objects in the environment can cause multiple reflections, diffraction, and scattering to arrive at the receiver. To understand the radio propagation and channel characteristics for different multipath environments, such as office, buildings, and tunnels, the BER performance analysis for high-speed personal communication service are investigated. Numerical results have shown that the multipath effect is an important factor in an adverse communication environment and using sectored antenna, diversity techniques and decision feedback equalizer can efficiently reduce multipath effect, improve the quality of communication and increase the bit transmission rate in indoor environments. Finally, a method for calculating the channel of UWB indoor communication systems has been presented by SBR/Image techniques and inverse Fourier transform. The frequency dependence of materials utilized in the structure on the indoor channel is accounted for in the channel simulations. By using the impulse responses of the multi-path channels, the impact of metallic cabinet to indoor multi-path is presented.
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Lee, Sen-Iuan, e 李森淵. "on Characteristics of Particle Saltation in Channel Bed". Thesis, 1993. http://ndltd.ncl.edu.tw/handle/02426194569777047134.
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Huang, wei-chin, e 黃偉晉. "Characteristics and Reliability of n-channel High-Voltage Transistors". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/93663394088110569172.
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碩士國立成功大學
微電子工程研究所碩博士班
95
In recent years, applications of high voltage integrated circuits are on the increase day by day. LDMOS transistors have been widely used in high voltage integrated circuits. That is due to its process flow being compatible with traditional low voltage CMOS devices. LDMOS transistors are operated under high gate and drain voltage, thus hot carrier reliability becomes a serious issue. In this thesis, the device characteristics and hot-carrier reliability of LDMOS transistors will be investigated. There are two important features in high-voltage(HV) devices. One is low on-resistance (Ron) and the other is high breakdown voltage (VBV). As we know, increasing the length of drift region could get higher breakdown voltage, but it also causes a rise of on-resistance. We will discuss the effects of different device dimension in the following five chapters. In Chapter 1, there will be some introductions of HV devices and its applications, and we also introduce the background of hot-carrier effect and Kirk effect. In Chapter 2, we will show all the parameters extracted from our experiments, measurement methodology, stress methodology, and device structure in our experiments. Then, we will discuss device parameters and degradation in Chapter 3. From our experiments, we discover that Ron degradation is related to the first Isub peak magnitude, and saturation in degradation was found in long time stress. In particular condition, recovery phenomena of device characteristics would happen. After discovering the phenomena, we discuss what cause the phenomena happen, and in what kind of condition. Finally, we try to find out the mechanism. We choose different kinds of device dimension for comparing characteristics and degradation in chapter 4. It is useful for optimizing devices. In Chapter 5, a conclusion and a future work will be presented for further investigation.
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Lin, Chen Wen, e 陳文玲. "A study on channel aggradation using multimode characteristics thod". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/64176601139577055825.
Texto completo da fonteResumo:
碩士國立交通大學
土木工程研究所
82
The purpose of this study is to develop a numerical model based on multimode characteristics method for fully coupled simulation of water and sediment movement in mobile-bed alluvial channels with nonuniform bed materials. According to multimode characteristics method, the characteristics equations and tota- -lly differential compatible equations of the numerical model could be obtained by consolidating water continuity and momen- -tum equations, sediment continuity equation and bed material sorting equtaions. The model contains explicit scheme, spatial reachback scheme, temporl reachback scheme and implicit scheme for solving flow depth, velocity, bed elevation, and bed-mate- -rial size fraction at each time step. The multimode scheme has the advantages of releasing Courant constraint and of effectively dealing with the problem of large differences in celerities among water-surface waves, bed-mate- -rial sorting waves. The multimode scheme is based on Lagrangian concept. The unknows could be computed from one time step to another by solving the compatible equations along the corres- ponding characteristics curves. When there are more then three governing equations, the eignvalues can only be solved numeri- -cally. The concept of buffer reach was adopted in this study to improve the stabilty and accuracy in numerical simulation affected by the upstream boundary condition. The simulation results for aggradation based on experimen- -tal data of Soni et al.(1980) and Yen et al.(1987) show that the proposed model can reasonably predict the evolution of bed elevation. Through the numerical simulation, the effect of boun- -dary condition on simulation results was examined. Furthermore, an assessment of model applicability was made through the analy- -sis of models stabilty, accuracy, and sensitivity.
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Tu, Ting-Chieh, e 杜定傑. "Simulation Analysis and Channel Characteristics for Outdoor Wireless Communications". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/68713868387444434817.
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博士淡江大學
電機工程學系博士班
97
In this thesis, using different diversity techniques and different simulation environments for outdoor wireless communication systems are presented. However, more obstructions such vehicles, trees, and buildings will degrade the received signal in the outdoor environments. Our purpose is that analyzing and understanding the channel characteristics of outdoor wireless communication. In the Chapter 3, we use the 2.5D SBR-Image ray tracing method to set up the outdoor simulation environment. Moreover, we take account of different types of antenna arrays to evaluate path loss in the outdoor environment. Moreover, by using the genetic algorithm, antenna pattern can be improved to have a good directivity and the reduction of path loss. The Chapter 4 shows different polarization schemes to calculate the cross polarization discrimination (XPD) value in different routes and environments. Polarization diversity is one of the most promising techniques to reduce fading with a compact antenna configuration requiring only one antenna location for the mobile terminal. The applicability of polarization diversity can partly be evaluated to analyze signal cross correlation and cross polarization discrimination (XPD) values. It is helpful to understand what polarization is suitable for the LOS and NLOS routes or urban and semi-urban environments Finally, outdoor channel characteristics with and without traffic in Ultra-wideband system are presented. Most researches of UWB system are concentrated on indoor scenes, but we proposed applications for outdoor UWB systems. By combining with 2.5D SBR/Image method, inverse fast Fourier transform (IFFT) and Hermitian processing, the channel impulse response in the UWB system can be calculated to get the bit error rate. Bit error rate (BER) and outage probability can be used to evaluate the performance of outdoor UWB systems with and without traffic. Based on the large bandwidth of UWB systems, the scale of time resolution on the time domain is just about several nanoseconds. So we take account of the S-rake receiver technique to increase the signal-to-noise ratio (SNR) in order to reduce multipath effect.