Dissertations / Theses on the topic 'Channel modelling'
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MELLO, RODRIGO SILVA. "PLC CHANNEL MODELLING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6687@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROO crescente interesse na utilização das redes de distribuição de energia elétrica como uma alternativa para o fornecimento de serviços de telecomunicações, tem motivado a pesquisa e o desenvolvimento de sistemas capazes de superar as características hostis deste ambiente como canal de comunicação. Com esta finalidade, este trabalho procura estimar o comportamento da rede PLC através da modelagem da função de transferência do canal, para a faixa de freqüência de 300 kHz a 30 MHz, por meio de um conjunto de parâmetros, os quais podem ser deduzidos da medição da resposta em freqüência. Dois modelos são apresentados para descrever a resposta em freqüência complexa de típicos canais power line, cobrindo todos os efeitos que os caracterizam, tais como o efeito de propagação por multipercursos causado pelas inúmeras reflexões nas junções da rede e o desvanecimento seletivo em freqüência. Os experimentos revelam que estes modelos apresentam todas as características principais da rede PLC podendo representar ferramentas úteis e efetivas na prática, oferecendo a possibilidade de realizar pesquisas para diferentes topologias de rede, a fim de estudar seu impacto no sistema de comunicação pela rede de energia elétrica. Além disso, propõem-se modelos de ajuste da função de transferência do canal a dados empíricos pelo método dos mínimos quadrados.
The crescent interest on the utilization of the low voltage power distribution grid as an alternative to provide services of telecommunication has motivated the systems development able to surpass the hostile characteristics of this environment as a communication channel. Therefore, this work seek to estimate the behavior of PLC network (Power Line Communication) through the modelling of the channel transfer function, to the range of 300 kHz to 30 MHz, by means of a set of parameters, which can be derived from the measure of the frequency response. Two models are presented to describe the complex frequency response of power line channels, covering all effects that define them, for example, the multipaths propagation generated by uncountable reflections on the network connections and selective fading in the frequency. The results of experiments show that these models present the most important characteristics of PLC network, representing useful and effective tools in the practice, offering the possibility to do researches to different network topologies, in order to study the impact of these effects on the PLC system. Moreover, they`re proposed channel transfer function adjustment models through empiric data and the least square method.
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Hopton, Stephen. "Modelling open channel flow." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11594/.
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The study of open channel flow and dam breaking is not a new topic in computational fluid dynamics. However it has only recently started to gain significant attention from researchers using meshless methods, i.e. numerical modelling techniques which do not rely on the use of a mesh to discretise the domain. The research presented here is an attempt to use the meshless method known as smoothed particle hydrodynamics (SPH) to simulate the flow of water down a channel. Hydra, a pre-existing SPH code designed originally for astrophysical simulations, was converted to simulate water flow and then applied to the problem of dam bursting and flow over a weir. The conversion of the code to its new purpose was verified by simple code tests and then extensive validation was performed via the modelling of multiple dambreaks. The validation process can be split into three broad categories: 1) Comparison against the published data gained from other numerical methods both meshless and traditional. 2) Comparison against physical experiments performed by the author. 3) Comparison against independent experimental data found in the literature. Hydra in its newly converted form was satisfactorily applied to the majority of the tests presented to it and the same level of accuracy was achieved as with any of the other codes tested. A limit to the SPH method for performing this type of simulation was proposed based on particle number, smoothing length and initial conditions. A formula for the calculation of the number of ghost particles required to prevent spurious boundary pressures was also proposed. An analysis of various kernels used by different SPH researchers was presented and it was discovered that a relatively simple cubic spline kernel proved sufficient and that increasing complexity did not provide an increase in solution accuracy. The flow of water over a weir was presented next and results compared to published data which utilised a leading mesh based fluid simulation package. Results gained from Hydra simulations showed good downstream water level prediction but overestimation of upstream levels. A steady state solution was achieved within a similar timeframe compared to the grid based method. It was concluded that use of the SPH method and the Hydra code in particular can provide solutions to problems involving water flow down a channel and accuracy on the dambreak tests was equal to any rival codes/methods tested. However when the complexity of the boundaries involved in the model increased there was some evidence that the CFX simulation package could be used to achieve a more accurate solution than Hydra. Suggestions for continuation of research into Hydra as a water flow modelling code are presented in addition to recommendations for improving the experimental methods used.
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Khoo, Soo Hee. "Indoor optical wireless channel modelling." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393595.
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Darbari, Faisal. "Wireless channel modelling for specknet." Thesis, University of Strathclyde, 2008. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21973.
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A wireless sensor network (WSN) consists of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as pressure, temperature, sound, vibration or motion at different locations. The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor retworks are now used in many commercial applications, including environment and habitat monitoring, healthcare applications, home automation, and traffic control. The physical size of these devices is shrinking due to advances in semiconductor technology. The main challenge is to produce low cost and miniature sensor nodes. Energy is the scarcest resource for these nodes as it determines the WSN lifetime. Since these nodes will be deployed close together to form a dense wireless network the received signaI to noise ratio at any instant of time not only depends on physical channel (i. e. path loss and fading) but also on various design parameters like CSMA/CA inhibition threshold, polarization, deployment strategy and node density. This thesis characterises the propagation channel for miniature wireless nodes. A characterization of the short range (<10cm), narrowband, wireless channel, appropriate to a dense network of wireless transceivers operating in the 2.4 GHz ISM band, is presented. Transmission loss measurements have been made in the laboratory at 2.45 GHz and a fading model derived. Aggregate interference due to neighboring carrier-sense-multiple-access (CSMA) nodes has been calculated. The resulting dependence of signl-to-interference ratio (SIR) on node density is presented to allow density dimensioning. Cumulative distributions of SIR have been used to establish performance statistics for example modulation and detection schemes. A simulation model has been developed to characterise the physical link experienced by these networks.
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Mota, Susana de Jesus. "Channel modelling for MIMO systems." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14961.
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Doutoramento em Engenharia ElectrotécnicaSystems equipped with multiple antennas at the transmitter and at the receiver, known as MIMO (Multiple Input Multiple Output) systems, offer higher capacities, allowing an efficient exploitation of the available spectrum and/or the employment of more demanding applications. It is well known that the radio channel is characterized by multipath propagation, a phenomenon deemed problematic and whose mitigation has been achieved through techniques such as diversity, beamforming or adaptive antennas. By exploring conveniently the spatial domain MIMO systems turn the characteristics of the multipath channel into an advantage and allow creating multiple parallel and independent virtual channels. However, the achievable benefits are constrained by the propagation channel’s characteristics, which may not always be ideal. This work focuses on the characterization of the MIMO radio channel. It begins with the presentation of the fundamental results from information theory that triggered the interest on these systems, including the discussion of some of their potential benefits and a review of the existing channel models for MIMO systems. The characterization of the MIMO channel developed in this work is based on experimental measurements of the double-directional channel. The measurement system is based on a vector network analyzer and a two-dimensional positioning platform, both controlled by a computer, allowing the measurement of the channel’s frequency response at the locations of a synthetic array. Data is then processed using the SAGE (Space-Alternating Expectation-Maximization) algorithm to obtain the parameters (delay, direction of arrival and complex amplitude) of the channel’s most relevant multipath components. Afterwards, using a clustering algorithm these data are grouped into clusters. Finally, statistical information is extracted allowing the characterization of the channel’s multipath components. The information about the multipath characteristics of the channel, induced by existing scatterers in the propagation scenario, enables the characterization of MIMO channel and thus to evaluate its performance. The method was finally validated using MIMO measurements.
Os sistemas equipados com múltiplas antenas no emissor e no recetor, conhecidos como sistemas MIMO (Multiple Input Multiple Output), oferecem capacidades mais elevadas, permitindo melhor rentabilização do espectro e/ou utilização de aplicações mais exigentes. É sobejamente sabido que o canal rádio é caracterizado por propagação multipercurso, fenómeno considerado problemático e cuja mitigação tem sido conseguida através de técnicas como diversidade, formatação de feixe ou antenas adaptativas. Explorando convenientemente o domínio espacial os sistemas MIMO transformam as características multipercurso do canal numa mais-valia e permitem criar vários canais virtuais, paralelos e independentes. Contudo, os benefícios atingíveis são condicionados pelas características do canal de propagação, que poderão não ser sempre as ideais. Este trabalho centra-se na caracterização do canal rádio para sistemas MIMO. Inicia-se com a apresentação dos resultados fundamentais da teoria da informação que despoletaram todo o entusiamo em torno deste tipo de sistemas, sendo discutidas algumas das suas potencialidades e uma revisão dos modelos existentes para sistemas MIMO. A caracterização do canal MIMO desenvolvida neste trabalho assenta em medidas experimentais do canal direcional adquiridas em dupla via. O sistema de medida é baseado num analisador de redes vetorial e numa plataforma de posicionamento bidimensional, ambos controlados por um computador, permitindo obter a resposta em frequência do canal rádio nos vários pontos correspondentes à localização dos elementos de um agregado virtual. As medidas são posteriormente processadas com o algoritmo SAGE (Space-Alternating Expectation-Maximization), de forma a obter os parâmetros (atraso, direção de chegada e amplitude complexa) das componentes multipercurso mais significativas. Seguidamente, estes dados são tratados com um algoritmo de classificação (clustering) e organizados em grupos. Finalmente é extraída informação estatística que permite caracterizar o comportamento das componentes multipercurso do canal. A informação acerca das características multipercurso do canal, induzidas pelos espalhadores (scatterers) existentes no cenário de propagação, possibilita a caracterização do canal MIMO e assim avaliar o seu desempenho. O método foi por fim validado com medidas MIMO.
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Cox, C. L. "Modelling channel dynamics and riparian ecology." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598103.
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This study aimed to develop and evaluate a numerical simulation model of the interdependent dynamics of channel form, processes and floodplain vegetation using cellular automaton approaches. The model was developed and evaluated using data from the River Feshie, Scotland. Firstly, field and historic data were examined in order to understand the ecology and dynamic nature of the study site. The braidplain was shown to exhibit a number of different mechanisms of change, varying from a wandering anabranch river to a more fragmented braided pattern; however the relationship between channel pattern and vegetation was not found to be straightforward, and multiple successional pathways were identified, depending on local abiotic conditions. Secondly, the capability of cellular automata models to simulate realistic patterns of discharge, channel change and floodplain ecology was evaluated. Cellular automata models involve a high level of simplification in order to facilitate the modelling of medium time and space scales with highly mobile boundary conditions. The models can predict realistic patterns of discharge and reach-scale ecology compositions, but further work is needed to improve the sediment transport functions. Finally, a cellular automata model was applied to investigate how floodplain ecology responds to different flood disturbance regimes and land management practices. This showed that cellular automata models may be used successfully to explore relationships between discharge, land use management and floodplain ecology. However, uncertainties regarding the lack of physical realism in some aspects of the model predictions meant it was unclear to what extent the results accurately represented future conditions for the River Feshie. Therefore, at this stage cellular automata models cannot be recommended for detailed applied management purposes in specific contexts.
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Hicks, C. M. "Modelling of multi-channel audio signals." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603997.
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This dissertation is concerned with the mathematical modelling of musical and audio signals. The emphasis is on multi-channel signals where either more than one copy of a single original is available for analysis, or where the signal comprises two or more parts. The most common example of this latter class is stereo signals which comprise a left and a right signal to create an auditory illusion of space. Two models are analysed in which we have multiple observations of a single signal. Both are based on the well-known auto-regressive (AR) model which has previously been successfully deployed in many audio applications. The first of these is the Multiply-Observed AR Model in which a single AR signal is contaminated by a number of independent interference signals to give multiple noisy observations of the original. It is shown that the statistics of the noise sources can be determined given certain broad assumptions. The model is applied to the problem of broadband noise reduction of a 78 r.p.m. record, of which a number of copies are available. The second model is the Ensemble-AR Model in which an ensemble of excitation sources drive identical AR filters to give multiple observed signals. Methods for estimation of the AR parameters from the observed data are derived. The model is applied to the detection of impulsive noise in audio signals, and interpolation of the missing data. The E-AR model is demonstrated to be superior to a similar single-channel approach in both of these areas. There is such a variety of stereo signals in existence that a very general model is needed to encompass their whole spectrum. The Coupled-ARMA Model put forward here is based on the ARMA model, but generates a pair of interdependent signals. Its structure allows efficient estimation of its parameters, and various methods for this are examined. Interpolators for Coupled-ARMA signals are derived. For much multi-channel audio work it is necessary to ensure that the observed signals are accurately aligned with each other. Where multiple copies of a disc or tape are under examination this is a difficult problem, since even minute time offsets and speed fluctuations lead to effects such as time-varying comb-filtering when the signals are summed. We examine this problem in detail, and develop a robust scheme for resynchronising signals in a Bayesian statistical framework. Quantisation of audio signals has received much recent research effort. The final part of the dissertation presents a flexible model-based quantisation algorithm. The algorithm is demonstrated in the quantisation of narrow-band signals, and as a powerful enhancement to a simple linear prediction coding system.
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Delis, Anargiros. "Computational modelling of open channel flow." Thesis, University of the West of England, Bristol, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244309.
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Lin, Min. "Channel modelling for wireless sensor networks." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611656.
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Lehner, Andreas. "Multipath channel modelling for satellite navigation systems /." Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016152468&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Tan, Bo. "Channel modelling and relay for powerline communications." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8062.
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The thesis discusses the channel modelling and relay techniques in powerline communications (PLC) which is considered as a promising technology for the Smart Grid communications, Internet access and home area network (HAN). In this thesis, the statistical PLC channel characteristics are investigated, a new statistical channel modelling method is proposed for the in-door PLC. Then a series of the relay protocols are suggested for the broadband communications over power grid. The statistical channel modelling method is proposed to surmount the limits of the traditional deterministic PLC channel models such as multipath model and transmission line model. To develop the channel model, the properties of the multipath magnitudes, interval between the paths, cable loss and the channel classification are investigated in detail. Then, each property is described by statistical distribution or formula. The simulation results show that the statistical model can describe the PLC channels as accurate as deterministic models without the topology information which is a time-consuming work for collecting. The relay transmission is proposed to help PLC adapting the diverse application scenarios. The protocols covers the main relay aspects which include decode/amplify forwarding, single/ multiple relay nodes, full/half duplex relay working mode. The capacity performance of each protocol is given and compared. A series of the facts which improve the performance of the PLC networks are figured out according to simulation results. The facts include that the decode-and-forward is more suitable for the PLC environment, deviation or transforming station is better location for placing relay node and full duplex relay working mode help exploiting the capacity potential of the PLC networks. Some future works are pointed out based on the work of statistical channel model and relay. In the last part of this thesis, an unit based statistical channel model is initialled for adapting various PLC channel conditions, a more practical relay scenario which contains multiple data terminals is proposed for approaching the realistic transmission scenario. At last, the relay for the narrowband PLC Smart Grid is also mentioned as future research topic.
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Rainbird, Peter Charles Bruce. "Depth averaged numerical modelling in channel bends." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317973.
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Weng, Jialai. "On advanced channel modelling for network planning." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/22361/.
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With the increasing demand for high speed wireless network services, the next generation wireless networks are proposed to use advanced wireless communication technologies. These technologies include massive MIMO, mmWave and distributed MIMO. In order to deploy wireless networks equipped with these technologies, channel models capturing the channel features and characteristics of these wireless technologies are essential in the planning and optimisation of networks. However, conventional channel models lack the capability to support these next generation network technologies. In this PhD thesis, I investigated the channel models for the next generation wireless technologies, including massive MIMO, mmWave communications and distributed MIMO. I developed channel models for network planning and optimisation based on conventional ray launching algorithms for these wireless technologies. The models have been validated and applied to optimise network performance. The existing challenge in wireless channel modelling is the improvement of modelling accuracy without increasing modelling complexity. In order to achieve this goal, a new calibration method is developed to improve the accuracy of the predication model when measurements are available. Moreover, in order to use the channel models as an effective tool in wireless network planning and optimisation, a new wireless capacity definition from radio propagation perspective is also investigated. It provides insight to the physical limit of wireless channel capacity from a radio propagation perspective.
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Pang, Jiayan. "Geological reservoir modelling of fluvial channel sands." Thesis, University of Aberdeen, 1993. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU052787.
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Fluvial channel sandstones form some of the major hydrocarbon reservoirs throughout the world. They are also the most difficult for reservoir geologists and engineers to deal with, because of the variety of sedimentary environments and complex sand body geometries and relationships which directly contribute to the reservoir quality and distributions. Successful geological reservoir modelling of fluvial channel sandstones involves proper understanding of the geological background of the target area, choosing a suitable method for each particular modelling purpose, and making available appropriate well data and analogue data. It is also the key to providing reservoir engineers with essential information for further oil exploitation and production activities. Two 3D modelling methods for fluvial channel sandstone reservoirs have been explored and contrasted in this Ph.D. project: Vertical Sequence Generation (VSG) and Geometry Based Generation (GBG). Computer software had to be written specially for each as it is not available, commercially or otherwise. Markov stochastic theory is employed in VSG in two aspects of geological reservoir characterisation. The first is to analyse the vertical statistical transition characteristics of different reservoir types or geological units of interest; and the second is to generate pseudo-vertical sequences of unsampled reservoirs by using the obtained Markov transition properties. This is a further development of the use of Markov statistics in geological description, and is a new approach to geological reservoir modelling developed in this Ph.D. project. The GBG method takes channel sand body dimensions and orientation into consideration and generates each channel sand body, three-dimensionally in the area of interest, with its location, thickness, width, length and orientation.
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Maharaj, Bodhaswar Tikanath Jugpershad. "MIMO channel modelling for indoor wireless communications /." Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-07292008-130655/.
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Son, Ill. "Modelling the hydrological effects of land-use change in small catchment." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358382.
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Konstatinos, Sasloglou. "Channel measurements and modelling for sensor network applications." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12833.
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Sun, Yue. "Channel modelling of blood capillary-based molecular communication." Thesis, University of Essex, 2018. http://repository.essex.ac.uk/22451/.
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Molecular communication (MC) is a new and promising interdisciplinary bio-inspired communication paradigm, which uses molecules as information carriers. Differing from traditional communication, MC is proposed as a feasible solution for nanoscale communication with the help of biological scenarios to overcome the communication limitations. Meanwhile, it is inspired by intracellular and intercellular communication, which involves exchange of information through the transmission, propagation, and reception of molecules. Blood capillaries, extensively distributed in the human body and mutually connected with tissues, are potentially applied to MC, which is the major motivation of this thesis. The focus of this PhD thesis is on the channel modelling of blood capillaries or blood vessels. The objectives of the research are to provide solutions to the modelling of blood capillary-based MC from a communication engineering and information theory perspective. The relationship of the biological scenario in blood capillaries to a communication system is studied. After demonstrating the mapping from biological phenomenon to emission, propagation and reception processes, system models are established. There are three models of blood capillaries behind different biological scenarios. Firstly, the thesis establishes a basic model of vesicle release, vesicle diffusion through blood capillary and ligand reception processes within the endocrine phenomenon. Moreover, differing from previous research in macroscopic Fick's diffusion, this work involves microscopic Langevin diffusion to describe the propagation process with a frequency domain method being proposed to calculate the information-theoretical performance channel capacity. Secondly, a much more realistic blood capillary model with blood flow drift which matches a laminar flow regime is presented, where a generalised Langevin equation is used to model the drift force exerted by blood flow. Finally, the thesis establishes a single input and multiple output MC model with hierarchical levels of Y-shaped bifurcation of blood capillaries, then BER, SNR, and channel capacity performance are analysed.
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Weir, Alexander James. "Channel characterisation and modelling for transcranial Doppler ultrasound." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3341.
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The detection of micro-embolic signals (MES) is a mature application of transcranial Doppler (TCD) ultrasound. It involves the identification of abnormally highpitched signals within the arterial waveform as a method of diagnosis and prediction of embolic complications in stroke patients. More recently, algorithms have been developed to help characterise and classify MES using advanced signal processing techniques. These advances aim to improve our understanding of the causes of cereberovascular disease, helping to target the most appropriate interventions and quantifying the risk to patients of further stroke events. However, there are a number of limitations with current TCD systems which reduce their effectiveness. In particular, improvements in our understanding of the scattering effects in TCD ultrasound propagation channels will benefit our ability to develop algorithms that more robustly and reliably identify the consistency and material make-up of MES. This thesis explores TCD propagation channels in three related research areas. Firstly, a method of characterising TCD ultrasound propagation channels is proposed. Isotropic and non-isotropic three dimensional space (3-D) spherical scattering channel models are described in terms of theoretical reference models, simulation models, and sum of sinusoids (SoS) simulators, allowing the statistical properties to be analysed and reported. Secondly, a TCD ultrasound medical blood flow phantom is described. The phantom, designed to replicate blood flow in the middle cerebral arteries (MCA) for TCD ultrasound studies, is discussed in terms of material selection, physical construction and acoustic characteristics, including acoustic velocity, attenuation and backscatter coefficients. Finally, verification analysis is performed on the non-isotropic models against firstly, the blood flow phantom, and secondly, a patient recordings database. This analysis expands on areas of agreement and disagreement before assessing the usefulness of the models and describing their potential to improve signal processing approaches for detection of MES. The proposed non-isotropic channel reference model, simulation model, SoS simulator, and blood flow phantom are expected to contribute to improvements in the design, testing, and performance evaluation of future TCD ultrasound systems.
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MacDonald, Ian. "Analysis and computation of steady open channel flow." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336664.
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Selvarasa, G. (Gowshigan). "Map-based channel model parameterization and comparison of three different deterministic channel modelling methods." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201907162704.
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Abstract. The interest in studying the channel characteristics is exponentially increasing with the growth of the communication systems. Various channel modelling approaches have been discussed in the past decades. The ray-tracing based channel models are distinguished from the other channel models as they consider the environmental information and thus are expected to reflect the real propagation phenomena that exist in that specific environment. The goal of this thesis is to study the propagation channel characteristics of the three different channel models. The two deterministic channel models are the simplified map-based ray tracing channel model implemented in the METIS project and the full ray tracing-based channel model implemented by the Beijing Jiaotong University. The third channel model is the hybrid model based on METIS map-based channel. It uses the deterministic part of the METIS map-based channel model.
Full ray-tracing based models require detailed description of the propagation environment or map and they target on site-specific channel modelling. Such site-specific models are not typically required in performance testing of devices, where the target is to ensure device performance in a typical propagation environment and possibly to cover some extreme cases. The simplifying map-based approach contradicts with the full ray tracing method in the way that the information of the map is reduced by approximating the building shapes and introducing artificial tiles to make scattering in the walls and ground reflections. Map-based channel modelling provides additional realism in channel models compared to traditional stochastic models applied in performance testing.
The urban street canyon scenario was chosen to be modelled. The comparison was carried out at 3.5 GHz by means of performance metrics such as total path loss, LOS and NLOS propagation conditions at UE positions, K-factor, RMS delay spread, statistics of angles, angle spreads, and cross polarization ratios.
The results have showed similarities in the LOS UE positions and dissimilarities in the NLOS UE positions. The reasons are identified and explained in the discussion section. It is decided to investigate the radio channel characteristics of the METIS map-based channel model and hybrid channel model for the future study purpose.
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McGuinness, James. "Implications of potassium channel heterogeneity for model vestibulo-ocular reflex response fidelity." Thesis, University of Stirling, 2014. http://hdl.handle.net/1893/21844.
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The Vestibulo-Ocular Reflex (VOR) produces compensatory eye movements in response to head and body rotations movements, over a wide range of frequencies and in a variety of dimensions. The individual components of the VOR are separated into parallel pathways, each dealing with rotations or movements in individual planes or axes. The Horizontal VOR (hVOR) compensates for eye movements in the Horizontal plane, and comprises a linear and non-linear pathway. The linear pathway of the hVOR provides fast and accurate compensation for rotations, the response being produced through 3-neuron arc, producing a direct translation of detected head velocity to compensatory eye velocity. However, single neurons involved in the middle stage of this 3-neuron arc cannot account for the wide frequency over which the reflex compensates, and the response is produced through the population response of the Medial Vestibular Nucleus (MVN) neurons involved. Population Heterogeneity likely plays a role in the production of high fidelity population response, especially for high frequency rotations. Here we present evidence that, in populations of bio-physical compartmental models of the MVN neurons involved, Heterogeneity across the population, in the form of diverse spontaneous firing rates, improves the response fidelity of the population over Homogeneous populations. Further, we show that the specific intrinsic membrane properties that give rise to this Heterogeneity may be the diversity of certain slow voltage activated Potassium conductances of the neurons. We show that Heterogeneous populations perform significantly better than Homogeneous populations, for a wide range of input amplitudes and frequencies, producing a much higher fidelity response. We propose that variance of Potassium conductances provides a plausible biological means by which Heterogeneity arises, and that the Heterogeneity plays an important functional role in MVN neuron population responses. We discuss our findings in relation to the specific mechanism of Desynchronisation through which the benfits of Heterogeneity may arise, and place those findings in the context of previous work on Heterogeneity both in general neural processing, and the VOR in particular. Interesting findings regarding the emergence of phase leads are also discussed, as well as suggestions for future work, looking further at Heterogeneity of MVN neuron populations.
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Broadhurst, Lucy. "Channel form flow resistance in gravel bed rivers." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267272.
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Bhatnagar, Rajeev Mohan. "Modelling and design of a dual channel magnetorheological damper." Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/8037.
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A limitation with the current analytical models for predicting the performance of a magnetorheological (MR) damper is that they fail to capture the hysteretic variation of force versus velocity variation correctly. This can significantly underestimate the damper force and overestimate the dynamic range of the device. In this work a transient analytical fluid dynamics model is developed by using a combination of Laplace and Weber transform and Duhamel’s superposition of velocity boundary condition, to overcome these limitations. The solution of the system of nonlinear simultaneous equations, obtained by applying mass flow balance, velocity compatibility conditions and force equilibrium of Bingham plastic plug flow, gives the damper force. This method is shown to generate direct and inverse model of an MR device. The proposed model has been validated against a commercially available MR damper at low speed, to a range of test signals. The mean error using the above model has been shown to be 5% for all the test signals. This compares well with three conventional models which give; transient constant velocity model 35%, quasi static model 35% and phenomenological model 35%. The phenomenological model gives 10% mean error for a sinusoidal input signal. The application of the proposed analytical model has been demonstrated by the design of a novel dual channel damper. The design of the electromechanical components has been shown to be np-hard problem and the optimisation using genetic algorithm has been applied to minimise the volume and electrical time constant. The performance of the dual channel damper has been simulated for various combinations of values of shear yield stress for two channels. Compared to the conventional single channel damper the novel design is shown to give 30% higher damper force, 50% improved dynamic range and limits the effect of transients to within 10% of the damper force. The dual channel damper is an effective solution to resist the onset of turbulent flow in the channels up to 20m/s piston velocity.
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Wadley, Martin Robert. "Modelling the bottom water circulation in the Vema Channel." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482778.
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Ly, Jim. "Physical Modelling of Pier Scour in a Constricting Channel." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31011.
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Experiments were completed in order to examine the effects of combined constriction and pier scour. Scour is cited as being a leading cause of bridge failure. It was found that in cases where both constriction and pier scour are present, the sum is greater than the linear addition of each individual case. This is contrary to the current industry assumption which states that the total depth of scour is the linear sum of the constriction and pier scour depth.
Velocimetry and scour data were collected enabling comparisons to be made in order to determine how the flowfield influences the equilibrium scour conditions. In addition, experiments were performed examining the effect that the pier shape has on the scour depth and distribution.
Since the results are contrary to the assumption used in industry, they are especially important and may help reduce future bridge failures.
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Wang, Zhenyu. "Channel modelling for urban multi-hop/ad hoc networks." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435742.
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Sharifi, Soroosh. "Application of evolutionary computation to open channel flow modelling." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/478/.
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This thesis examines the application of two evolutionary computation techniques to two different aspects of open channel flow. The first part of the work is concerned with evaluating the ability of an evolutionary algorithm to provide insight and guidance into the correct magnitude and trend of the three parameters required in order to successfully apply a quasi 2D depth averaged Reynolds Averaged Navier Stokes (RANS) model to the flow in prismatic open channels. The RANS modeled adopted is the Shiono Knight Method (SKM) which requires three input parameters in order to provide closure, i.e. the friction factor (\(f\)), dimensionless eddy viscosity (λ) and a sink term representing the effects of secondary flow (Γ). A non-dominated sorting genetic algorithm II (NSGA-II) is used to construct a multiobjective evolutionary based calibration framework for the SKM from which conclusions relating to the appropriate values of \(f\), λ and Γ are made. The framework is applied to flows in homogenous and heterogeneous trapezoidal channels, homogenous rectangular channels and a number of natural rivers. The variation of \(f\), λ and Γ with the wetted parameter ratio (\(P_b\)/\(P_w\)) and panel structure for a variety of situations is investigated in detail. The situation is complex: \(f\) is relatively independent of the panel structure but is shown to vary with P\(_b\)/P\(_w\), the values of λ and Γ are highly affected by the panel structure but λ is shown to be relatively insensitive to changes in \(P_b\)/\(P_w\). Appropriate guidance in the form of empirical equations are provided. Comparing the results to previous calibration attempts highlights the effectiveness of the proposed semi-automated framework developed in this thesis. The latter part of the thesis examines the possibility of using genetic programming as an effective data mining tool in order to build a model induction methodology. To this end the flow over a free overfall is exampled for a variety of cross section shapes. In total, 18 datasets representing 1373 experiments were interrogated. It was found that an expression of form \(h_c\)=A\(h_e\)\(^{B\sqrt S_o}\), where \(h_c\) is the critical depth, \(h_e\) is the depth at the brink, \(S_o\) is the bed slope and A and B are two cross section dependant constants, was valid regardless of cross sectional shape and Froude number. In all of the cases examined this expression fitted the data to within a coefficient of determination (CoD) larger than 0.975. The discovery of this single expression for all datasets represents a significant step forward and highlights the power and potential of genetic programming.
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Laurensen, David Irvine. "Indoor radio channel propagation modelling by ray tracing techniques." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/12397.
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In response to the requirement for a more detailed channel model based on the physical characteristics of the environment within which indoor radio communications operate, this thesis presents a channel model based on ray tracing techniques. The mathematical basis for the model is presented in terms of the electromagnetic properties of simple objects. The resulting model is coded into a simulation system which takes a description of a building in terms of the structure of internal walls, floors and ceilings. Through repeated application of the reflection process, a description of the channel impulse response is created for a given transmitter and receiver position from the multipath components generated. This model is applied, in progressing degrees of complexity, to two buildings for which narrowband physical measurements are available. Comparison is made between the measured results and the narrowband simulation results which leads to an analysis of the various propagation mechanisms involved in in-building communications. It is found that the model, while not accurately predicting the measured results, does produce a model that, considering the unknown parameters of the environment and experimental procedure, relates well to the channel experienced by a communication system. Wideband channel characteristics are determined from the simulation model, and found to give access to more detailed information on the channel than is obtainable through physical measurement. The results of the wideband simulations are compared with published material containing measurement results, and the relationship to the narrowband results already presented is shown.
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Konstantinou, Konstantinos. "Low-height channel modelling with application to multihop UMTS." Thesis, University of Surrey, 2008. http://epubs.surrey.ac.uk/843650/.
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Applying the relaying concept to a Code Division Multiple Access (CDMA) mobile network is not a new idea, and many such systems employing relaying capabilities have been suggested. An obstacle to their evaluation with respect to capacity and coverage gains over the conventional non-relaying networks has been the inapplicability of the existent path loss models for low height terminal communications. Herein, empirical propagation models for relaying systems with low height terminals are proposed. The new models consist of line-of-sight and non-line-of-sight branches, and they take into account the effect of transmitter and receiver height, citing and environmental parameters. They are also complemented by shadowing and fast-fading distribution and correlation statistics. The models are evaluated by their performance in accurate estimations of other sets of measurement data. Before the derived models are applied in an analytical and a simulation model, the thesis continues with a discussion on the distributed power control function and frequency allocation schemes in a multihop Universal Mobile Telecommunications System (UMTS), deployed in a Manhattan grid. This is in order to derive closed-form expressions, for selected frequency schemes, for the minimum transmit powers which satisfy the link quality criteria. The propagation models are then employed in these expressions to evaluate the system performance by both simulation and analysis and improvement by employing relays is shown. A dynamic system-level simulation, which was utilised to perform further analysis, is then presented. The measurement-based path loss, fading and shadowing models, derived from the previous chapters are employed. Both uplink and downlink operations of the cellular system are considered at the same time. The simulation outcomes showed that the transmit power savings and coverage and capacity gains are in agreement with the expected analytical results, but dependent on the frequency scheme, relaying, antenna directivity gains and other assumed parameters.
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Kendall, James D. (James Douglas) 1959 Carleton University Dissertation Engineering Electrical. "Two-dimensional analytical modelling of the short-channel mosfet." Ottawa.:, 1987.
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Wu, Shangbin. "Massive MIMO channel modelling for 5G wireless communication systems." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/2889.
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Massive Multiple-Input Multiple-Output (MIMO) wireless communication systems, equipped with tens or even hundreds of antennas, emerge as a promising technology for the Fifth Generation (5G) wireless communication networks. To design and evaluate the performance of massive MIMO wireless communication systems, it is essential to develop accurate, flexible, and efficient channel models which fully reflect the characteristics of massive MIMO channels. In this thesis, four massive MIMO channel models have been proposed. First, a novel non-stationary wideband multi-confocal ellipse Two-Dimensional (2-D) Geometry Based Stochastic Model (GBSM) for massive MIMO channels is proposed. Spherical wavefront is assumed in the proposed channel model, instead of the plane wavefront assumption used in conventional MIMO channel models. In addition, the Birth-Death (BD) process is incorporated into the proposed model to capture the dynamic properties of clusters on both the array and time axes. Second, we propose a novel theoretical non-stationary Three-Dimensional (3-D) wideband twin-cluster channel model for massive MIMO communication systems with carrier frequencies in the order of gigahertz (GHz). As the dimension of antenna arrays cannot be ignored for massive MIMO, nearfield effects instead of farfield effects are considered in the proposed model. These include the spherical wavefront assumption and a BD process to model non-stationary properties of clusters such as cluster appearance and disappearance on both the array and time axes. Third, a novel Kronecker Based Stochastic Model (KBSM) for massive MIMO channels is proposed. The proposed KBSM can not only capture antenna correlations but also the evolution of scatterer sets on the array axis. In addition, upper and lower bounds of KBSM channel capacities in both the high and low Signal-to-Noise Ratio (SNR) regimes are derived when the numbers of transmit and receive antennas are increasing unboundedly with a constant ratio. Finally, a novel unified framework of GBSMs for 5G wireless channels is proposed. The proposed 5G channel model framework aims at capturing key channel characteristics of certain 5G communication scenarios, such as massive MIMO systems, High Speed Train (HST) communications, Machine-to-Machine (M2M) communications, and Milli-meter Wave (mmWave) communications.
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Sgarabotto, Alessandro. "Modelling the plano-altimetric equilibrium of a tidal channel." Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422836.
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Tidal channels are ubiquitous features of the tidal landscape which play a critical role in the morphodynamic evolution of these landscapes. In addition, tidal channels represent a substantial ecological and economic value, being however vulnerable to climate changes and increasing anthropogenic pressures. Improving current knowledge on tidal channel form and function is therefore key step to model and predict the evolution of tidal systems.
A number of studies have analyzed the evolution and equilibrium configuration of tidal channels, focusing on the equilibrium profile of the channel bed for a given channel-width distribution as well as on channel equilibrium cross-sectional shape. However, the role that vegetation growth on the marsh platform plays on the equilibrium morphology of salt-marsh channels has received less attention. Here we developed a model which analyzes the equilibrium configuration of a channel and the adjacent salt-marsh platform and provides a useful tool for quantitative analyses of long-term eco-morphodynamic studies in tidal landscapes. The open channel flow is studied by a 1D hydrodynamic model developed to describe the flow field within the channel and, if present, on the lateral shoals. The 1D hydrodynamics was “validated” considering some test cases comparing the results obtained with a full-fledged 2D model as a reference.
The tidal channel evolution can be sought using three different setups which single out landforming effects: purely erosional model, in which the erosion is the only effect shaping the channel; depositional model, in which erosion, sea level rise and settling deposition scour and promote the vertical accretion of the basin; depositional model with vegetation, in which vegetation effects are included in the previous setup.
Model results reproduce several observed channel characteristics which are deemed to be relevant from a geomorphological point of view. Model results also show that vegetation encroachment on the marsh surface produces two competing effects. Enhanced marsh accretion associated with the increased particle trapping and with the organic production by halophytic plants, increases marsh elevation in the tidal frame, thus reducing the landscape forming tidal prism and the channel cross-sectional area. However, the increased flow resistance on the canopy promotes flow concentration within the channel, leading to more incised cross sections characterized by smaller width-to-depth ratios. Our simulations indicate that the second process is more important in marshes which are lower in the tidal frame, whereas the first process is more important in marshes higher in the tidal frame when most of the tidal fluxes are already confined within the channel.I canali a marea innervano gli ambienti a marea costituendo dei percorsi preferenziali per il trasporto di acqua, sedimenti e nutrimenti. Inoltre, i canali a marea rappresentano un sostanziale valore ecologico ed economico, essendo tuttavia vulnerabili ai cambiamenti climatici e alle crescenti pressioni antropiche. La comprensione dei meccanismi che regolano la forma ed il funzionamento dei canali a marea è cruciale per migliorare la previsione delle tendenze evolutive degli ambienti a marea. Numerosi studi hanno analizzato l'evoluzione e la configurazione dell'equilibrio dei canali di marea, concentrandosi sul profilo di equilibrio del letto di canale per una data distribuzione della larghezza del canale e sulla forma della sezione trasversale di equilibrio del canale. Tuttavia, il ruolo che la crescita della vegetazione sulla piattaforma di barena svolge sulla morfologia di equilibrio dei canali a marea ha ricevuto meno attenzione. In questa tesi è stato sviluppato un modello che analizza la configurazione di equilibrio di un canale e l'adiacente barena e fornisce uno strumento utile per analisi quantitative di tipo eco-morfodinamico a lungo termine in ambienti a marea. L'idrodinamica è studiata attraverso un modello idrodinamico 1D sviluppato per descrivere il campo di moto all'interno di un canale e, dove presenti, sui bassofondali laterali. L'idrodinamica 1D è stata validata considerando alcuni casi test e confrontando i risultati ottenuti con un modello 2D scelto come riferimento. L'evoluzione del canale a marea può essere analizzata utilizzando tre diverse impostazioni che consentono di considerare separatamente o congiuntamente gli effetti responsabili della formazione del canale: modello puramente erosivo, l'erosione è l'unico effetto che modella il canale; modello deposizionale, in cui gli effetti considerati sono erosione, innalzamento del livello del mare e deposito per sedimentazione; modello con vegetazione, in cui si aggiungono alla precedente configurazione gli effetti di vegetazione. I risultati del modello riproducono diverse caratteristiche osservate del canale ritenute rilevanti dal punto di vista geomorfologico. I risultati del modello mostrano anche che la presenza della vegetazione sulla superficie di barena produce due effetti contrastanti. La crescita della vegetazione associata ad un incremento dell'effetto di intrappolamento di particelle di sedimento e della produzione organica da parte di piante alofite, aumenta la quota della superficie di barena rispetto all'escursione di marea, riducendo così il prisma di marea e l'area della sezione trasversale del canale. Tuttavia, la maggiore resistenza al flusso sulle piattaforme laterali promuove la concentrazione del flusso all'interno del canale, portando a sezioni trasversali più incise caratterizzate da rapporti larghezza-profondità più piccoli. Le nostre simulazioni indicano che il secondo processo è più importante sulle superfici di barena a quote più basse rispetto all'escursione di marea, mentre il primo processo è più importante sulle superfici di barena a quote più alte rispetto all'escursione di marea quando la maggior parte dei flussi di marea sono già confinati all'interno del canale.
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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.
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García, Ariza Alexis Paolo. "Modelling and experimental analysis of frequency dependent MIMO channels." Doctoral thesis, Universitat Politècnica de València, 2009. http://hdl.handle.net/10251/6563.
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La integración de tecnologías de ulta-wideband, radio-cognitiva y MIMO representa una herramienta podersoa para mejorar la eficiencia espectral de los sistemas de comunicación inalámbricos. En esta dirección, nuevas estrategias para el modelado de canales MIMO y su caracterización se hacen necesarias si se desea investigar cómo la frecuencia central y el acho de banda afectan el desempeño de los sistemas MIMO. Investigaciones preliminares han enfocado menos atención en cómo estos parámetros afectan las características del canal MIMO. Se presenta una caracterización del canal MIMO en función de la frecuencia, abondándose puntos de vista experimentales y teóricos. Los problemas indicados tratan cinco áreas principales: medidas, post-procesado de datos, generación sintética del canal, estadística multivariable para datos y modelado del canal.
Se ha diseñado y validado un sistema de medida basado en un analizador vectorial de redes y se han ejecutado medidas entre 2 y 12 GHz en condiciones estáticas, tanto en línea de vista como no línea de vista. Se ha propuesto y validado un procedimiento confiable para post-procesado, generación sintética de canal y análisis experimental basado en medidas en el dominio de frecuencia. El procedimiento experimental se ha focalizado en matrices de transferencia del canal para casos no selectivos en frecuencia, estimándose además las matrices complejas de covarianza, aplicándose la factorización de Cholesky sobre ls CCM y obteniéndose finalmente matrices de coloreado del sistema. Se presenta un procedimiento de corrección para generación sintética del canal aplicado a casos MIMO de grandes dimensiones y cuando la CCM es indefinida. Este CP permite la factorización de Cholesky y de dichas CCM. Las características multivariables de los datos experimentales han sido investigadas, realizándose un test de normalidad compleja multivariable.García Ariza, AP. (2009). Modelling and experimental analysis of frequency dependent MIMO channels [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/6563
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Hussan, Jagir R. "Modelling the influence of ion channel distributions in cardiac arrhythmias." Thesis, University of Auckland, 2012. http://hdl.handle.net/2292/19263.
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Understanding cardiac electrophysiology in general and the role of ion channels in particular, is a problem of practical significance. Limitations on experimental investigations have necessitated the development of theoretical and computer models. In this thesis, a theoretical perspective informed by published experimental observations and computer modelling tools is adopted. Myocyte organisation and distribution of ion channels in the cardiac ventricular tissue greatly influence its mechanical and electrical behaviour. Computer simulations of these systems are computationally-expensive, nontrivial and limit model based investigations. A novel algorithm that substantially reduces the computational expenses under specific conditions is developed. The integration of multiple models to reproduce the cardiac behaviour across spatial and temporal scales, introduces non-trivial computing and the mathematical issues. Using an analytic approach that partially resolves these issues, novel models of the passive cardiac-muscle-tissue, extracellular excitation-propagation and stability of the tissue are developed. A rational approach to model deformation of cellular aggregations is presented together with relevant proofs. A remarkable relationship, that the minimisation of local mean angular distortion and Dirichlet energy are identical (up to a measure) is presented. It is anticipated that the results presented in this thesis will initiate further investigation to expand the proposed models and increase understanding the dynamics and control of the heart.
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Holmstedt, Elise. "Modelling Transport of Non-Spherical Particles in Small Channel Flow." Doctoral thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60402.
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A model has been developed to predict the movement of oblate and prolate particles on amicro- and nano-scale in laminar channel flow, both for purposes of statistical aggregationand to study motion of single particles. For the purpose of this thesis the model has beenadapted to examine particle deposition patterns in the human lung and the filtration ofparticles during manufacturing of composites, but the possibilities of the model extendto all areas where the particle Stokes and Reynolds numbers are small.To examine the influence the breathing pattern has on the deposition of inhalednano- and micro-fibres deposition rates were compared at different injection points ofthe breathing cycle, where maximum deposition was found when the particles releasedat the beginning of the respiratory cycle while minimum deposition occurred when therelease came at peak inhalation. A comparison between a quasi-steady flow and a cyclicflow was done and it was found that a quasi-steady solution provides a reasonably goodapproximation if the velocity used is a mean of the velocity during the residence time ofthe simulations.A statistical study was done to compare the deposition rates of oblate and prolateparticles of different size and aspect ratio as they travel down narrowing bronchi in asteady, fully developed parabolic flow field. The model shows a clear correlation betweenincreased particle size and increased deposition, it also consistently yielded a higherdeposition rate for oblate particles compared to prolate particles with a similar geometricdiameter. A study of the motion and orientation of single oblate and prolate particleswith large aspect ratio and the same geometric diameter has also been done.In liquid moulding of fibre reinforced composites the resin can be enhanced by nanoandmicro-particles to give the final product additional properties. This is a processthat can be simulated by approximating the gap formed between the fibre bundles to achannel flow with a radially suctioning component caused by the capillary pressure in themicro channels in the bundles. First this flow field is described with a radial componentthat is constant over the length of the channel and compared with a flow purely drivenby an applied pressure gradient without radial forces. Particle size showed a small butstill noticeable influence, particularly for larger particles under the influence of gravity.The second flow field used is time dependent where the flow front in the bundlesand channel mimics that of previous observations. There is initially a period where theflow front in the channel is leading but the radial capillary fluid transport causes thisto retreat and be overtaken by the flow front in the bundles. Particles mixed in theresin will in general travel with a velocity greater than that of the fluid front until theradial velocity component at that point filters the particles by transporting them to thechannel wall. Particle geometry has a smaller impact on the deposition rates in compositemanufacturing than in inhalation since the effect of Brownian forces and gravity are muchsmaller, although there is still some discernible patterns such as a higher deposition ratefor spherical particles during the transport to the flow front.
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Morrison, Gerald Dale. "Measurement, characterization, and modelling of the indoor radio propagation channel." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq64829.pdf.
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Osawe, Maxwell Osayande. "Open channel turbulence modelling using layer-averaged large eddy simulation." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392113.
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Kumarapeli, Pushpa. "Modelling the computerised clinical consultations : a multi-channel video study." Thesis, Kingston University, 2011. http://eprints.kingston.ac.uk/22364/.
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This study aims to understand the use of a computer during GP consultations and to enable the development of EPR systems which are easier to review, enter data into, use to take action, and is more sensitive to the clinical context. This thesis reports the development of a multi-channel video and data capture toolkit, the ALFA (Activity Log File Aggregation) because existing observation techniques have limitations. None of the existing tools are designed to assess human-computer interaction in the context of the clinical consultation, where the social interaction is the prime focus. The ALFA tool-kit has been used to observe and study 163 live primary care consultations supported by computer systems with four different designs. A detailed analysis of consultation interactions was then performed focusing on doctor-patient communication and the integration of the computer into the consultation workflow. The data collection elements of the ALFA supported recording of consultation activities by providing rating techniques attuned with the characteristics of those interactions. The Log File Aggregation (LFA) component of the ALFA toolkit aggregated those multitudes of data files into a single navigable output that can be studied both quantitatively and qualitatively. A set of Unified Modelling Language (UML) sequence diagrams were then created as they could be used by software engineers to develop better systems. This research proposes a framework with three elements to analyse the computerised clinical consultation; (1) the overview of the context within which the consultation was carried out, (2) time taken to perform key consultation tasks and (3) the process used. Traditional analysis with its emphasis on the technology often misses crucial features of the complex work environments in which the technology is implemented. Direct observation could inform software designers in developing systems that are more readily integrated into clinical workflow. Direct observation of the consultation, using the ALFA toolkit is acceptable to patients; captures the context of the consultation the precise timing and duration of key tasks; and produces an output a software engineer can understand. ALFA offers a range of possibilities for research in the consulting room. The computer should be considered as an active element of the consultation; room layout and consultation models should let the computer in, while software engineers take in the capacity to sustain patient centred social interactions as a core facet of their design agenda.
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Neville, Kevin. "Channel attribution modelling using clickstream data from an online store." Thesis, Linköpings universitet, Statistik och maskininlärning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-139318.
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In marketing, behaviour of users is analysed in order to discover which channels (for instance TV, Social media etc.) are important for increasing the user’s intention to buy a product. The search for better channel attribution models than the common last-click model is of major concern for the industry of marketing. In this thesis, a probabilistic model for channel attribution has been developed, and this model is demonstrated to be more data-driven than the conventional last- click model. The modelling includes an attempt to include the time aspect in the modelling which have not been done in previous research. Our model is based on studying different sequence length and computing conditional probabilities of conversion by using logistic regression models. A clickstream dataset from an online store was analysed using the proposed model. This thesis has revealed proof of that the last-click model is not optimal for conducting these kinds of analyses.
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Lu, Zhihua. "Stochastic modelling of unsteady open channel flow and reliability analysis /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202008%20LU.
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Smithson, Allan Geoffrey. "Wide area radio channel modelling across the indoor/outdoor interface." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423492.
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Chaganti, Vasanta Gayatri. "Wireless body area networks : accuracy of channel modelling and prediction." Phd thesis, Canberra, ACT : The Australian National University, 2014. http://hdl.handle.net/1885/150112.
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Toffano, Alberto Antonio <1989>. "Protein Modelling Focused on Voltage-Gated Sodium Channel NaV 1.7." Master's Degree Thesis, Università Ca' Foscari Venezia, 2019. http://hdl.handle.net/10579/15049.
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As the state-of-the-art stands at present, it is recognised the narrow correlation between the behavior of voltage-gated sodium channel transmembrane human isoform NaV 1.7 and pain perception .
Gain of function mutations are strictly related with several neurophaty (IEM, PEPD). On the other way round, loss of functions are associated with congenital insensivity to pain. Drugs actually avaiable are not able to relief effectively patients with pain disorders. It is thus necessary improve the knowledge in this sense, difficulties in obtaining these informations resides in production and purification of enough proteins to XDR analysis for each genetic variants. In order to achive these goals, computational chemistry comes in help. It allows to develop large amount of structural models of proteins of which are known only the primary sequence
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Finotello, Alvise. "Tidal Channel Patterns: Field Investigations, Numerical Modelling and Laboratory Experiments." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3425863.
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Tidal meandering channels are ubiquitous features of tidal landscapes and play a fundamental role on the eco-morphodynamic evolution of these environments. However, only a handful of papers provide details on tidal meander planimetric shape, morphometric characteristics and morphodynamic evolution, and the internal achitecture of tidal meanders has not been explored in detail. Moreover, the morphodynamic evolution of tidal meanders and the related sedimentary products have often been interpreted on the basis of the well developed models and theories existing for their fluvial counterparts, despite a number of differences were a priori identifiable. Toward the goal of improving current understanding of the morphodynamic evolution of tidal meanders, five main issues have been investigated in the present work: i) rates of migration and evolutionary dynamics of tidal meanders; ii) assessment and quantification of differences and analogies existing between the planform features of tidal and fluvial meanders; iii) variations of tidal meander hydrodynamics in response to different tidal phases, and the role that these variations exert on tidal meander sedimentary products; iv) role played by bidirectional flows, tidal asymmetries and lateral tributaries; v) assessment of influence of tide amplitude, basin slope and initial shoreline configuration on tidal channel network ontogeny and evolution via laboratory experiment. A multidisciplinary approach has been adopted, with different methodologies encompassing remote sensing techniques, field observations, numerical modelling and physical-laboratory experiments. Activities have been carried out in parallel with sedimentological studies, in order to provide a comprehensive framework. The main results from this work highlighted that: I) once conveniently scaled with channel width, tidal meander migration rates are very similar to those displayed by fluvial meanders, thus challenging the paradigm of tidal meanders as a stable landscape features; II) differences and analogies between tidal and fluvial meander planforms can be addressed in a quantitative way, and different metrics exist thta allow one to successfully quantify these differences; III) strong asymmetries exist between different tidal phases, exerting a crucial role on the depositional patterns of tidal meanders; IV) under certain conditions, lateral tributaries can strongly influence the evolution of bends modifying local mechanisms of flow and sediment distribution; V) tidal channel network features evolve differently in response to different tidal ranges, basin slopes and relative sea level changes, whereas the number of breaches along the initial shoreline seems to have little effect on the evolution of the network itself.Le reti di canali meandriformi costituiscono una delle principali componenti dei sistemi mareali, e giocano un ruolo di fondamentale importanza nell’evoluzione eco-morfodinamica di questi ambienti. Tuttavia, solo un numero limitato di studi scientifici ne ha analizzato le configurazioni planimetriche, le caratteristiche morfometriche e l’evoluzione morfodinamica. Inoltre, l’evoluzione morfodinamica e i prodotti sedimentari dei meandri a marea sono spesso stati interpretati sulla base di teorie e modelli sviluppati per i loro omologhi fluviali, nonostante numerose differenze tra le due tipologie siano identificabili a priori. Nell’intento di comprendere più approfonditamente l’evoluzione morfodinamica dei meandri a marea, nel presente lavoro sono stati studiati 5 differenti argomenti: i) tassi di migrazione e dinamiche evolutiove dei meandri a marea; ii) stima e quantificazione delle differenze planimetriche esistenti tra meandri fluviali e tidali; iii) variazioni dell’idrodinamica dei meandri a marea in risposta all’alternanza delle fasi mareali, e influenza di queste variazioni sui prodotti sedimentari propri dei meandri a marea; iv) ruolo della bidirezionalità del flusso, delle asimmetrie mareali e dei tributari laterali; v) stima dell’influenza dell’ampiezza di marea, delle pendenze topografiche del bacino tidale e della configurazione iniziale della linea di costa sulla nascita ed evoluzione morfologica delle reti di canali a marea. Nelle suddette analisi é stato utilizzato un approccio di tipo multidisciplinare, combinando metodologie quali remote-sensing, osservazioni in situ, modellazione numerica ed esperimenti su modelli fisici. Le attività sono state condotte in parallelo con studi sedimentologici, così da fornire un quadro che fosse il più esaustivo possibile. I principali risultati ottenuti evidenziano che: I) se convenientemente normnalizzati con la larghezza del canale, i tassi di migrazione dei meandri a marea sono molto simili a quelli dei loro corrispettivi fluviali, inficiando così il paradigma che vede i meandri tidali come un’entità morfologica essenzialmente stabile; II) le differenze tra meandri tidali e fluvali non sono solo qualitative, e diverse sono le metriche che possono essere utilizzate per quantificare queste differenze; III) le asimmetrie tra le diverse fasi di marea sono significative, e influenzano i patterns deposizionali in modo determinante; IV) gli affluenti laterali possono influenzare fortemente l’evoluzione dei meandri, modificando i meccanismi locali di distrubuzione dei flussi e dei sedimenti; V) le reti di canali a marea evolvono in modo diverso in risposta a differenti ampiezze di marea, pendenze del bacino tidale e cambiamenti del livello relativo del medio mare, mentre la configurazione iniziale della linea di costa non sembra avere effetti significativi sull’evoluzione della rete stessa.
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Greenhill, Rosemary Kate. "An investigation into the mechanisms of compound meandering channel flow." Thesis, University of Bristol, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334230.
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Randle, Andrew Martin. "Dynamic radio channel effects from L-band foliage scatter." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341630.
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Downham, S. E. "Modelling the two-phase performance of a centrifugal pump." Thesis, Cranfield University, 2000. http://dspace.lib.cranfield.ac.uk/handle/1826/11005.
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A review was carried out which revealed that no simple mathematical model was available which could be used to predict the performance of a centrifugal pump when it is operating under two phase flow conditions. Experimental analyses were carried out to aid the development of such a model. A rotating channel test rig was designed to study the structure of airwater flow through an impeller passageway. The observations generated a large amount of qualitative data. A full scale centrifugal pump was also tested which provided data that allowed the results of the rotating channel experiments to be considered in more quantitative terms. These two sets of experimental work allowed a conceptual model of the two phase flow through a centrifugal pump to be constructed. The model assumes that forces act on the bubbles as they pass through the impeller passageway because of the rotation and the curvature of the impeller passageway. These forces cause the bubbles to decelerate and coalesce creating a stationary air void which leads to a partial blockage of the channel. This causes the velocity of the fluid passing through the pump to be modified. The model uses a onedimensional velocity vector approach adjusted for hydraulic losses to calculate the head raised by the pump under such conditions. The model presented provides the basis upon which a predictive tool could be developed and used in the development engineering environment. Currently operational problems that arise because of two phase flow are often quantified using scaled hydraulic models, which are expensive, or within the actual application where costly engineering solutions may be required to give acceptable performance. A mathematical model is a much more cost effective tool and its application allows the engineer to decide whether system performance would be compromised by the two phase conditions encountered and propose possible solutions. In recommending the development of such a model it is necessary to consider where and how in the project cycle it should be used. A number of companies were canvassed and it was concluded that in many cases such models are used too late in the project cycle to provide maximum return. In the case of projects which include participants from a number of companies it is suggested that an inter-company team should be constructed if development models are to be widely used. This team should be used to plan and implement the use of development models efficiently and ensure that the data produced is communicated effectively and is of the maximum value to the participants.
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Mundangepfupfu, Tinotenda Leslie. "Simulation modelling of QoS enhancements in IEEE, 802. 11 networks and the effects of channel modelling." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/11682.
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