Dissertations / Theses: 'Channeled'

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Palmieri, Benoit. "Diffusion in channeled structures." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18269.

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The theory of Ronis and Vertenstein [J. Chem. Phys. vol. 85, 1628, (1986)] is used to calculate the permeability of Xenon in Theta-1 and of Argon in alpha-quartz, both crystalline sodalites containing large, one-dimensional channels in the first case and narrow interconnected channels in the second. The simulated dynamics of a small part of the crystal atoms exactly reproduce those of the full crystal by the means of a generalized Langevin classical equation of motion. An approximate expression for the potential of mean force inside the crystal is derived. The Theta-1 energy landscape is smooth with small energy barriers while the alpha-quartz has large energy barriers to diffusion. The permeability is reported for both systems and compared in detail with that obtained from transition state theory. The role of the lattice vibrations is also investigated. For Xenon in Theta-1, transition state theory does not properly describe the diffusion process and the lattice vibrations do not play a large role. For Argon in alpha-quartz, transition state theory is more appropriate but there, the lattice vibrations cannot be neglected. For systems where the lattice vibrations play a role, the quantum mechanical corrections to the diffusion are computed. The diffusion is studied using the path integral formalism. Forward-Backward path integrals are combined and, using the MSR [Phys. Rev. A., vol. 8, 423 (1973)] formalism, are transformed to a set of generalized Langevin equations that reduce to the classical equations of motion at high temperatures. The quantum mechanical treatment of the lattice vibrations results in a decreased permeability. The quantum corrections to the potential of mean force are computed from an approximate density matrix. A modification to the original Feynman-Kleinert variational method[Phys. Rev. A., vol. 34, 5080 (1986)] to calculate quantum mechanical partition functions is sugges
La méthode dévelopée par Ronis et Vertenstein [J. Chem. Phys. vol. 85, 1628, (1986)] est utilisée pour calculer la perméabilité du Xénon à l'intérieur du zéolite Theta-1 et de l'Argon à l'intérieur d'un cristal d'alpha-quartz. Ces deux sodalites contiennent des canaux qui sont larges et unidimensionnels dans le premier cas et étroits et interconnectés dans le deuxième. La dynamique d'une petite partie des atomes du cristal est explicitement simulée. Cette dynamique est décrite à partir d'équations de Langevin généralisées qui reproduisent l'effet du reste du cristal. L'énergie libre du gaz absorbé à l'intérieur du cristal est approximée. Le profil énergétique à l'intérieur du zéolite Theta-1 est presque plat et contient des barrières énergétiques peu élevées. Celui à l'intérieur du quartz contient de larges barrières à la diffusion. La perméabilité des deux systèmes est rapportée et comparée en détail avec celle obtenue à partir de la théorie dite des états de transitions. Le rôle qu'ont les modes de vibrations du cristal sur la diffusion est aussi étudié. Pour le Xénon à l'intérieur du zéolite Theta-1, la théorie des états de transitions ne décrit pas adéquatement la diffusion du gaz et les vibrations du cristal ne jouent pas un grand rôle. Pour l'argon dans le quartz, la théorie des états de transitions est plus appropriée et les vibrations du cristal ne peuvent être négligées. Pour les systèmes où les vibrations du cristal jouent un rôle, les premières corrections quantiques sont calculées. Dans ce cas, la diffusion est étudiée à partir de la formulation des intégrales de chemins. Les intégrales de chemins sont combinées et, en utilisant la théorie développée par Martin, Siggia et Rose [Phys. Rev. A., vol. 8, 423 (1973)], réduites à un système d'équations de Langevin généralisées q

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Yang, Shannon X. (Shannon Xuan). "Positive pressure induced channeled suction cups." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83829.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 39-40).
Leaking in water pipe is a critical issue in Middle Eastern countries such as Kuwait where water is scarce. In-pipe robots can be dispatched to discover the network and inspect the inner surface of the pipe. This thesis describes the design and characterization of suction pads for in-pipe robots. The suction cups are made of hyperelastic materials that contain air channels inside. Instead of using conventional suction technique that is prone to leaking and loosing adhesion force, the suction cup is actuated by compressed air or liquid, which deforms the geometry of the cup to achieve suction. In order to verify the geometry changes during actuation, a uniaxial tension test was done on the elastic material used to acquire the material properties and the suction cup designs were then simulated using FEA in ABAQUS. Next, prototypes were designed in SolidWorks and fabricated using soft lithography techniques. To measure the suction force, pressure measurements were taken both inside the prototype channels and underneath the suction cup. Results show that a Positive Pressure Actuated Suction-cup (PPAS) of diameter forty millimeters can achieve suction force up to 68 N. As more air is inserted into PPAS, the suction force also increases. The concept has proved to be a feasible solution for pipe inspection robot.
by Shannon X. Yang.
S.B.

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Fraschetti, F., J. J. Drake, O. Cohen, and C. Garraffo. "Mottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627037.

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The evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought to be due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares, or traveling shock waves, and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T. Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesized along the individual particle trajectories. We have investigated the energy range [0.1-10] GeV, consistent with expectations from Chandra X-ray observations of large flares on T. Tauri stars and recent indications by the Herschel Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding a dominance of energetic particles over X-rays in the ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area, except within narrow regions where particles are channeled onto the disk by the strongly tangled and turbulent magnetic field. The radial thickness of such regions is 5 stellar radii close to the star and broadens with increasing radial distance. This likely continues out to large distances from the star (10 au or greater), where particles can be copiously advected and diffused by the turbulent wind.

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Trexler, Christina M. "Biology, ecology and control of the invasive channeled apple snail, Pomacea canaliculata." Master's thesis, University of Central Florida, 2011. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5062.

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Invasive species are detrimental to native biotas worldwide. Recently, Florida was invaded by a freshwater snail (Pomacea canaliculata) native to Argentina. This snail is a serious pest of rice crops in Asia, but little is known about its interactions within Florida ecosystems. Possible competitive exclusion of the native congener (P. paludosa) is a concern because it is the almost exclusive prey of the federally endangered Everglades snail kite (Rostrhamus sociabilis). My research consisted of three parts. First, to identify possible methods to control P. canaliculata in the egg stage, I experimentally evaluated the effects of photoperiod, substrate availability, and food type and availability on hatching success and hatchling survival. None of these factors significantly affected hatching or survival, suggesting that P. canaliculata could invade many water bodies. Second, I used a randomized block design to assess the separate and combined effects of population density and food availability on growth and spawning of P. canaliculata. Food availability but not density significantly affected growth; snails fed less food grew less, but neither factor affected spawning. Third, I used a replacement series design to assess competition between P. canaliculata and P. paludosa under food limitation. For both species, snails fed less grew significantly less, and snails exposed to greater congener densities spawned less than when exposed to conspecifics only. While my results predict that P. paludosa should exclude P. canaliculata, previous literature and current invasions suggest that the exotic snail may co-exist with its North American congener.
ID: 030422795; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.)--University of Central Florida, 2011.; Includes bibliographical references (p. 53-63).
M.S.
Masters
Biology
Sciences

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Rusz, Ján, Shunsuke Muto, and Kazuyoshi Tatsumi. "Energy Loss by Channeled Electrons: A Quantitative Study on Transition Metal Oxides." Cambridge University Press, 2013. http://hdl.handle.net/2237/20834.

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Rusz, Ján, Ikuo Nishida, Shunsuke Muto, and Kazuyoshi Tatsumi. "Site-specific electronic configurations of Fe 3d states by energy loss by channeled electrons." AIP publishing, 2010. http://hdl.handle.net/2237/20791.

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Straut, Christine M. "Fundamental aspects of small molecules and macromolecules on poly(ethylene terephthalate) capillary-channeled ploymer fibers." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1247508460/.

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Nelson, Dwella M. "Characterization of capillary-channeled polymer fibers as stationary phases for high-performance liquid chromatography of macromolecules." Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1171041566/.

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Stonecipher, Clint. "Mitigation of Medusahead (Teaniatherum caput-medusae) Through Grazing and Revegetation on the Channeled Scablands of Eastern Washington." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4595.

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A large portion of the historical steppe and shrub-steppe habitats in eastern Washington have been altered through biotic and abiotic processes resulting in the annual grass medusahead (Taeniatherum caput-medusae (L.) Nevski) becoming a large component of the altered vegetation. Experiments were conducted to determine whether: 1) protein supplementation would help increase utilization of medusahead by cattle, 2) native and introduced grass cultivars could establish in the region, and 3) mechanical disturbance would aid in establishing Vavilov II Siberian wheatgrass (Agropyron fragile [Roth] P. Candargy) and Immigrant forage kochia (Bassia prostrata [L.] A.J. Scott). Cattle grazing medusahead-infested rangeland for 10-d periods during summer months increased consumption of medusahead due to a reduction in the quality of forage alternatives. Cattle supplemented with a protein concentrate increased consumption of medusahead during d 6 to 10 of the grazing periods resulting in a reduction of medusahead abundance over time. Introduced grass cultivars; Vavilov II, Hycrest IIcrested wheatgrass (Agropyron cristatum [L.] Gaertn.), and Bozoisky II Russian wildrye (Psathyrostachys juncea [Fisch.] Nevski), and a native grass mix; Sherman big bluegrass (Poa secunda J. Presl), Secar Snake River wheatgrass (Elymus wawawaiensis J. Carlson & Barkworth), Bannock Thickspike wheatgrass (Elymus lanceolatus [Scribn. & J.G. Sm.] Gould), and Recovery Western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve) were planted at three locations. Sherman big bluegrass was the only native species that established with 47 % initial establishment and persistence increasing to 65 % over the course of the study. Hycrest II had 64 % stand establishment but persistence decreased to 48 % and Vavilov II had 57 % initial establishment and decreased to 50 %. Sherman Big bluegrass had greater biomass production in May however, the later maturing Hycrest II and Vavilov II had similar biomass production to Sherman Big bluegrass in July. Bozoisky II had poor stand establishment and decreased over the course of the study. Mechanical disturbance from disking in the fall was successful in establishing Vavilov II and Immigrant forage kochia. In conclusion, cattle can be used to reduce medusahead abundance in rangelands and revegetation with Vavilov II, Hycrest II and Sherman big bluegrass was successful. Mechanical disturbance was successful in aiding in establishment of Vavilov II and Immigrant forage kochia.

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Alenin, Andrey S. "Matrix structure for information-driven polarimeter design." Thesis, The University of Arizona, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3700194.

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Estimating the polarization of light has been shown to have merit in a wide variety of applications between UV and LWIR wavelengths. These tasks include target identification, estimation of atmospheric aerosol properties, biomedical and other applications. In all of these applications, polarization sensing has been shown to assist in discrimination ability; however, due to the nature of many phenomena, it is difficult to add polarization sensing everywhere. The goal of this dissertation is to decrease the associated penalties of using polarimetry, and thereby broaden its applicability to other areas.

First, the class of channeled polarimeter systems is generalized to relate the Fourier domains of applied modulations to the resulting information channels. The quality of reconstruction is maximized by virtue of using linear system manipulations rather than arithmetic derived by hand, while revealing system properties that allow for immediate performance estimation. Besides identifying optimal systems in terms of equally weighted variance (EWV), a way to redistribute the error between all the information channels is presented. The result of this development often leads to superficial changes that can improve signal-to-noise-ration (SNR) by up to a factor of three compared to existing designs in the literature.

Second, the class of partial Mueller maitrx polarimeters (pMMPs) is inspected in regards to their capacity to match the level of discrimination performance achieved by full systems. The concepts of structured decomposition and the reconstructables matrix are developed to provide insight into Mueller subspace coverage of pMMPs, while yielding a pMMP basis that allows the formation of ten classes of pMMP systems. A method for evaluating such systems while considering a multi-objective optimization of noise resilience and space coverage is provided. An example is presented for which the number of measurements was reduced to half.

Third, the novel developments intended for channeled and partial systems are combined to form a previously undiscussed class of channeled partial Mueller matrix polarimeters (c-pMMPs). These systems leverage the gained understanding in manipulating the structure of the measurement to design modulations such that the desired pieces of information are mapped into channels with favorable reconstruction characteristics.

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Fornea, Donald Seth. "Incorporation of capillary-channeled polymer (C-CP) fibers into micropipette tips for solid phase extraction with applications in bioanalysis." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1202937631/.

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Bateman, Timothy M. "Exploring and Describing the Spatial and Temporal Dynamics of Medusahead in the Channeled Scablands of Eastern Washington Using Remote Sensing Techniques." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6896.

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Medusahead is a harmful weed that is invading public lands in the West. The invasion is a serious concern to the public because it can reduce forage for livestock and wildlife, increase fire frequency, alter important ecosystem cycles (like water), reduce recreational activities, and produce landscapes that are aesthetically unpleasing. Invasions can drive up costs that generally require taxpayer’s dollars. Medusahead seedlings typically spread to new areas by attaching itself to passing objects (e.g. vehicles, animals, clothing) where it can quickly begin to affect plants communities. To be effective, management plans need to be sustainable, informed, and considerate to invasion levels across large landscapes. Ecological remote sensing analysis is a method that uses airborne imagery, taken from drones, aircrafts, or satellites, to gather information about ecological systems. This Thesis strived to use remote sensing techniques to identify medusahead in the landscape and its changes through time. This was done for an extensive area of rangelands in the Channel Scabland region of eastern ashington. This Thesis provided results that would benefit land managers that include: 1) a dispersal map of medusahead, 2) a time line of medusahead cover through time, 3) “high risk’ dispersal areas, 4) climatic factors showing an influence on the time line of medusahead, 5) a strategy map that can be utilized by land managers to direct management needs. This Thesis shows how remote sensing applications can be used to detect medusahead in the landscape and understand its invasiveness through time. This information can help create sustainable and effective management plans so land managers can continue to protect and improve western public lands threatened by the invasion of medusahead.

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Zhao, Zhiyong. "Angular Dependence of the Stopping Processes and the Yields of Ion-induced Electron Emission from Channeled MEV Protons in <100> Silicon Foils." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc279025/.

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Potter, Christopher G., Adam G. Panagos, Kurt Kosbar, and William Weeks. "OPTIMAL TRAINING PARAMETERS FOR CONTINUOUSLY VARYING MIMO CHANNELS." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/605025.

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ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada
To correctly demodulate a signal sent through a multiple-input multiple-output (MIMO) channel, a receiver may use training to learn the channel parameters. The choice of training parameters can significantly impact system performance. Training too often yields low throughput while training infrequently produces poor channel estimates and increased transmission errors. Previous work on optimal training parameters has focused on the block fading Rayleigh model. This work examines a more general case; finding the training parameters that maximize throughput for a continuously varying channel. Training parameters that maximize a lower bound on channel capacity are determined via simulation, and general guidelines are presented for selecting optimal training parameters.

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Männikkö, Roope. "Voltage sensor movements in shaker and HCN channels /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-739-8.

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Zhang, Hongling. "Sigma Receptors Modulation of Voltage-gated Ion Channels in Rat Autonomic Neurons." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001183.

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Shiao, Fu-Sheng. "Combined Channel Estimation and Turbo Equalization for Wireless Channels." Thesis, University of Canterbury. Electrical and Computer Engineering, 2007. http://hdl.handle.net/10092/1189.

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Single-carrier linear modulation techniques combined with frequency-domain equalization provide a viable alternative to multicarrier techniques for combating multipath fading in channels with large delay spread. Such modulations tolerate frequency offset and have well controlled peak to average power ratio. They have comparable complexity to orthogonal frequency division multiplexing (OFDM) systems, and are more robust to synchronization errors. If error correction coding is used, then information can be iteratively passed between the equalizer and the decoder to improve performance. This is referred to as turbo equalization. To date, several turbo equalization schemes have been proposed, but little work has been done to address the problem of channel estimation for the turbo equalization process. The work in this thesis considers frequency-domain turbo equalization with imperfect channel state information (CSI) at the receiver for different wireless channels. A receiver structure incorporating joint frequency-domain turbo equalization and time- domain channel estimation is developed. The novelty of this scheme lies in the combination of time-domain channel estimation and frequency-domain turbo equalization, and in its extension to high level modulation formats. The performance of the system is investigated by a combination of analysis and computer simulation. It is found that the system performs well over a range of dispersive channels.

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Liew, Tong Hooi. "Channel coding and space-time coding for wireless channels." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341591.

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Potter, Chris. "Modeling Channel Estimation Error in Continuously Varying MIMO Channels." International Foundation for Telemetering, 2007. http://hdl.handle.net/10150/604490.

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ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada
The accuracy of channel estimation plays a crucial role in the demodulation of data symbols sent across an unknown wireless medium. In this work a new analytical expression for the channel estimation error of a multiple input multiple output (MIMO) system is obtained when the wireless medium is continuously changing in the temporal domain. Numerical examples are provided to illustrate our findings.

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Peterson, Blaise. "Molecular determinants of dihydropyridine binding on L-type calcium channels /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6269.

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Ferner, Matthew C. "Environmental Modification of Chemosensory Interactions between Predators and Prey: The World According to Whelks." Diss., Connect to this title online, 2006. http://etd.gatech.edu/theses/available/etd-04102006-140436/.

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Thesis (Ph. D.)--Georgia Institute of Technology, 2006.
Title from PDF t.p. (viewed on Oct. 28, 2006). Weissburg, Marc, Committee Chair ; Dusenbery, David, Committee Member ; Hay, Mark, Committee Member ; Webster, Donald, Committee Member ; Blanton, Jackson, Committee Member. Includes bibliographical references (p. 108-119).

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Pastore, Adriano. "Communication rates for fading channels with imperfect channel-state information." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/279247.

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The present thesis studies information rates for reliable transmission of information over fading channels in the realistic situation where the receiver has only imperfect channel-state knowledge. Of particular interest are analytical expressions of achievable transmission rates under imperfect and no CSI, that is, lower bounds on the mutual information and on the Shannon capacity. A well-known mutual information lower bound for Gaussian codebooks is obtained when conflating the additive (thermal) noise with the multiplicative noise due to the imperfections of the CSIR into a single effective noise term, and then assuming that this term is independent Gaussian. This so-called worst-case-noise approach allows to derive a strikingly simple and well-known lower bound on the mutual information of the channel. A first part of this thesis proposes a simple way to improve this worst-case-noise bound by means of a rate-splitting approach: by expressing the Gaussian input as a sum of several independent Gaussian inputs, and by assuming that the receiver performs successive decoding of the corresponding information streams, we show how to derive a larger mutual information lower bound. On channels with a single transmit antenna, the optimal allocation of transmit power across the different inputs is found to be approached as the number of inputs (so-called layers) tends to infinity, and the power assigned to each layer tends to zero. This infinite-layering limit gives rise to a mutual information bound expressible as an integral. On channels with multiple transmit antennas, an analogous result is derived. However, since multiple transmit antennas open up more possibilities for spatial multiplexing, the rate-splitting approach gives rise to a whole family of infinite-layering bounds. This family of bounds is closely studied for independent and identically zero-mean Gaussian distributed fading coefficients (so-called i.i.d. Rayleigh fading). Most notably, it is shown that for asymptotically perfect CSIR, any bound from the family is asymptotically tight at high signal-to-noise ratios (SNR). Specifically, this means that the difference between the mutual information and its lower bound tends to zero as the SNR tends to infinity, provided that the CSIR tends to be exact as the SNR tends to infinity. A second part of this thesis proposes a framework for the optimization of a class of utility functions in black-Rayleigh fading multiple-antenna channels with transmit-side antenna correlation, and no CSI at the receiver. A fraction of each fading block is reserved for transmitting a sequence of training symbols, while the remaining time instants are used for transmission of data. The receiver estimates the channel matrix based on the noisy training observation and then decodes the data signal using this channel estimate. For utilities that are symmetric functions of the eigenvalues of the matrix-valued effective SNR (such as, e.g., the worst-case-noise bound), the problems consisting in optimizing the pilot sequence and the linear precoder are cast into convex (or quasi-convex) problems for concave (or quasi-concave) utility functions. We also study an important subproblem of the joint optimization, which consists in computing jointly Pareto-optimal pilot sequences and precoders. By wrapping these optimization procedures into a cyclic iteration, we obtain an algorithm which converges to a local joint optimum for any utility.
Aquesta tesi estudia les taxes d'informació per la transmissió fiable d'informació en canals amb esvaïments sota la hipòtesi realista de que el receptor té un coneixement tan sols imperfecte de l'esvaïment aleatori. De particular interès són les expressions analítiques de les taxes de transmissió assolibles amb coneixement imperfecte i sense coneixement de l'estat del canal, és a dir, cotes inferiors de la informació mútua i de la capacitat de Shannon. Una cota inferior de la informació mútua per a codis gaussians ben coneguda s'obté combinant el soroll additiu (tèrmic) amb el terme de soroll multiplicatiu causat per les imperfeccions del coneixement de l'estat del canal en un únic soroll efectiu, i assumint que el soroll és gaussià i independent. Aquesta aproximació del pitjor soroll permet obtenir una expressió molt simple i ben coneguda de la informació mútua del canal. Una primera part d'aquesta tesi proposa un procediment senzill per a millorar aquesta cota associada al pitjor cas mitjançant una estratègia de repartiment de taxa: expressant l'entrada gaussiana del canal com a la suma de diverses entrades gaussianes independents i suposant que el receptor realitza una descodificació seqüencial dels fluxos d'informació, es mostra com obtenir una major cota inferior de la informació mútua del canal. En canals amb una única antena en transmissió, la distribució òptima de potència als diferents fluxos s'obté quan el seu nombre (capes) tendeix a infinit, i la potència associada a cada capa tendeix a zero. El límit associat a un nombre infinit de capes dóna lloc a una expressió integral de la cota de la informació mútua. En canals amb múltiples antenes s'obté un resultat similar. No obstant això, atès que la utilització de múltiples antenes proporciona més possibilitats de multiplexat espacial, el procediment dóna lloc a tota una família de cotes inferiors de la informació mútua associades a una combinació de capes infinita. S'estudia en detall aquesta família de cotes per al cas de coeficients d'esvaïments gaussians de mitjana zero, independents i idènticament distribuïts (conegut com esvaïment i.i.d. Rayleigh). S'obtenen diverses propietats de la família de cotes. És important destacar que per a coneixement asimptòtic perfecte del canal en recepció, qualsevol membre de la família de cotes és asimptòticament ajustat per alta relació senyal a soroll (SNR). En concret, la diferència entre la informació mútua i la seva cota inferior tendeix a zero quan la SNR tendeix a infinit sempre que el coneixement del canal tendeixi a ser exacte a mesura que la SNR tendeix a infinit. Una segona part d'aquesta tesi proposa un marc per a l'optimització d'una classe de funcions d'utilitat en canals amb múltiples antenes i esvaïments Rayleigh per blocs amb correlació en transmissió i sense informació sobre el canal a recepció. Una fracció temporal de cada bloc d'esvaïment es reserva per transmetre una seqüència de símbols d'entrenament mentre que la resta de mostres temporals s'utilitzen per transmetre informació. El receptor estima la matriu del canal partint de la seva observació sorollosa i descodifica la informació mitjançant la seva estimació del canal. Per a una classe de funcions d'utilitat que són funcions simètriques dels autovalors de la SNR matricial efectiva, els problemes consistents en optimitzar la seqüència pilot i el precodificador lineal són transformats en problemes convexos (o quasi-convexos) per a funcions d'utilitat còncaves (o quasi-còncaves). També s'estudia un subproblema important de l'optimització conjunta, que consisteix en el càlcul de les seqüències d'entrenament i dels precodificadors conjuntament Pareto-òptims. Integrant aquests procediments d'optimització en una iteració cíclica, s'obté un algoritme que convergeix a un òptim local conjunt per a qualsevol utilitat quasi-còncava

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Mason, Amy. "Single-Channel Characterisation of Potassium Channels with High Temperature Studies." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491373.

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Potassium channels control the conduction of K+ across cell membranes, down their electrochemical gradient. This rapid and highly selective movement of K+ is essential to many biological processes. K+ channels are largely alpha helical, tetrameric proteins that span the lipid bilayer. Diversity in K+ channels arises primarily in the mechanism of gating by various ligands or voltage; however, the basic structural elements, notably the selectivity filter are conserved within the family. Studies ~n this thesis focus on the single-channel behaviour of the K+ channels KcsA and Kcv. KcsA is a proton-activated channel from the bacterium Streptomyces lividans and its crystal structure was the first of a K+ channel to be solved. Kcv expressed by the Paramecium bursaria Chlorella virus is the smallest known K+ channel and thus represents the minimal structural entity necessary to form a functional and selective pore. Studies on the bacterial inward rectifying channels, KirBacs, have also been initiated. The KirBacs are a superfamily of prokaryotic channels homologous to eukaryotic Kir channels. In this work, KcsA and Kcv were found to form stable tetramers, which can be expressed by coupled in vitro transcription and translation and purified by polyacrylamide gel electrophoresis. The purified tetramers were reconstituted into planar lipid bilayers and studied at the single-channel level. Through single-channel recordings the ionic selectivity, gating behaviour, functional effects of site-directed mutagenesis and the interaction between Kcv and blockers have been studied. In addition, single-channel studies at elevated temperatures have revealed the remarkable thermostability of Kcv, as well as insight into the transport of ions through a narrow and selective pore. Through temperature studies, it has been possible to obtain the thermodynamic and kinetic parameters describing Kcv activity.

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Cheng, Julian Zhishen. "Channel optimized quantization of images over binary channels with memory." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22287.pdf.

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VIEIRA, ROBSON DOMINGOS. "MIMO MEASURED CHANNELS: CAPACITY RESULTS AND ANALYSIS OF CHANNEL PARAMETERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2005. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=7954@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Sistemas com múltiplas antenas transmissoras e receptoras, também conhecidos como sistemas MIMO (Multiple Input-Multiple Output), têm sido apontados como uma solução para aumentar a capacidade de enlaces sem fio, permitindo aos usuários utilizar aplicações com altas taxas de dados. Isto é extremamente importante em sistemas onde a capacidade obtida com as técnicas tradicionais é bastante limitada devido às características do ambiente de propagação. Com o sistema MIMO, algumas destas características são exploradas para criar canais paralelos e obter aumento expressivo de capacidade. A análise da capacidade de sistemas MIMO se baseia em uma modelagem desenvolvida a partir do comportamento estatístico dos pares de enlaces existentes entre as múltiplas antenas transmissoras e receptoras. Existe, portanto, um grande interesse em medir este comportamento para situações típicas bem como em relacioná-lo a determinados parâmetros do sistema. Nesta tese apresentam-se os resultados de uma campanha de medidas visando caracterizar canais MIMO de faixa estreita e faixa larga em ambientes fechados (indoor) com uma freqüência de portadora de 2GHz. A partir dos dados medidos, avalia-se a capacidade e diversos parâmetros do canal espaço-temporal. Os parâmetros do canal MIMO são estimados através do algoritmo FD-SAGE e as dispersões temporal e espacial do canal são calculadas a partir dos parâmetros estimados. Uma análise dos autovalores da matriz do canal MIMO é realizada com o objetivo de relacionar os valores da capacidade ao número de canais paralelos. É analisada, ainda, a correlação entre a capacidade e os parâmetros físicos do canal, tais como espaçamento entre os elementos do arranjo, espalhamento angular, espalhamento dos retardos, número e potência dos multipercursos.
Multiple antenna systems known as MIMO (Multiple Input Multiple Output) systems have been proposed as an effective way to address the user demand for high data rate applications in wireless systems. This is especially important in systems where the capacity attained with traditional techniques is very limited due to the adverse characteristics of the propagation environment. With MIMO, some of these characteristics are used to create parallel channels producing significant increase in capacity. The analysis of MIMO capacity is based on models developed from the statistical behavior of the multiple links between the transmitting and receiving antennas, and therefore there has been large interest in measuring these characteristics in typical scenarios and in relating the data to system parameters. In this thesis the results of a MIMO wideband measurement campaign carried out in an indoor scenario with a carrier frequency of 2 GHz is presented. The wideband and narrowband channel capacity and several channel parameters are evaluated from the measured data. The channel parameters are estimated using the frequency domain Space-Alternating Generalized Expectation maximization (FD- SAGE) algorithm. Temporal and spatial dispersions of the multipath channel are calculated from the estimated parameters and an eigenvalue analysis is performed seeking to relate the capacity values to the number of parallel channels. In addition, the correlation between channel capacity and physical parameters as antenna spacing, angle spread, delay spread, number and power of multipath components is investigated.

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Khan, Anwer Ali. "Iterative Decoding and Channel Estimation over Hidden Markov Fading Channels." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/32470.

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Since the 1950s, hidden Markov models (HMMS) have seen widespread use in electrical engineering. Foremost has been their use in speech processing, pattern recognition, artificial intelligence, queuing theory, and communications theory. However, recent years have witnessed a renaissance in the application of HMMs to the analysis and simulation of digital communication systems. Typical applications have included signal estimation, frequency tracking, equalization, burst error characterization, and transmit power control. Of special significance to this thesis, however, has been the use of HMMs to model fading channels typical of wireless communications. This variegated use of HMMs is fueled by their ability to model time-varying systems with memory, their ability to yield closed form solutions to otherwise intractable analytic problems, and their ability to help facilitate simple hardware and/or software based implementations of simulation test-beds.

The aim of this thesis is to employ and exploit hidden Markov fading models within an iterative (turbo) decoding framework. Of particular importance is the problem of channel estimation, which is vital for realizing the large coding gains inherent in turbo coded schemes. This thesis shows that a Markov fading channel (MFC) can be conceptualized as a trellis, and that the transmission of a sequence over a MFC can be viewed as a trellis encoding process much like convolutional encoding. The thesis demonstrates that either maximum likelihood sequence estimation (MLSE) algorithms or maximum a posteriori (MAP) algorithms operating over the trellis defined by the MFC can be used for channel estimation. Furthermore, the thesis illustrates sequential and decision-directed techniques for using the aforementioned trellis based channel estimators en masse with an iterative decoder.

Master of Science

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Shimizu, Atsuya, Ryoko Niwa, Zhibo Lu, Haruo Honjo, and Kaichiro Kamiya. "Effects of Dronedarone on HERG and KCNQ1/KCNE1 Channels." Research Institute of Environmental Medicine, Nagoya University, 2003. http://hdl.handle.net/2237/7585.

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Panagos, Adam G., and Kurt Kosbar. "MIMO CHANNEL TIME VARIATION AS A FUNCTION OF MOBILE USER VELOCITY." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605780.

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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California
The analysis of multiple-input multiple-output (MIMO) communication systems often assumes a static, or quasi-static, environment. Platform motion and changes in the environment makes this an unreasonable assumption for many telemetry applications. This paper uses computer simulations to characterize the time variation of MIMO channel parameters when there is relative motion between the transmitter and receiver. These simulation results yield explicit time intervals over which a MIMO channel can be considered static for a given relative velocity and propagation environment. These results can be used to predict the practical limitations of proposed MIMO system algorithms.

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Choi, Eun Kyung. "Regulation of KCNQ1 potassium channel trafficking and gating by KCNE1 and KCNE3 /." Access full-text from WCMC, 2009. http://proquest.umi.com/pqdweb?did=1692648191&sid=1&Fmt=2&clientId=8424&RQT=309&VName=PQD.

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PETER, COSTANZO. "Capturing reservoir production uncertainty for channelized reservoirs using channel amalgamation indexes." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2644036.

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One of the main concerns in reservoir studies is to accurately define the internal architecture and the geological characteristics of the reservoir so as to estimate the amount of hydrocarbons that could be recovered for a given development strategy. This can represent a major challenge especially during the appraisal stage of a reservoir, because the information available is still very limited, or in the presence of geological heterogeneities, which increase the architectural complexity and the uncertainty associated to the internal description, such as in channelized depositional settings. At the appraisal stage of a reservoir study, all the uncertainties affecting the quantity and distribution of hydrocarbons in the reservoir should be captured and accounted for in the evaluation of the final hydrocarbon recovery to properly assess the viability of any development plan. A typical modeling workflow accounting for geological uncertainties consists in creating a large set of 3-D stochastic geological (static) models from a set of geological input parameters. Subsequently, a few representative reservoir realizations are selected out of this set based on the calculated hydrocarbons originally in place and simulated to estimate future production so as to propagate the uncertainty onto the final recovery factors. However, even in homogeneous reservoirs, the estimation of the hydrocarbon stored in the reservoir can be affected by uncertainties because it is calculated mostly from local petrophysical parameters, which might not be representative of the rock properties at the reservoir scale. This especially applies to channelized reservoirs characterized by depositional elements with high geological heterogeneity, both in the lateral and in the vertical directions. Thus for these depositional settings a more attractive criterion for the model selection is offered by the study of the connectivity layout of the reservoir elements. In the technical literature, connectivity is defined through numerical indexes that account for geological connectivity between reservoir elements, which might not be indicative of reservoir production performance. In fact, the latter is influenced by the degree of connectivity among sand bodies and only deep merging of the channels guarantees that the reservoir can be efficiently drained by just a few wells. Therefore, in the first place, the present study was aimed at thoroughly investigating the validity of the indexes previously proposed in the technical literature by evaluating the reservoir production uncertainty associated to sets of synthetic equi-probable models of channelized oil reservoirs. Secondly, the goal of the research was to develop new indexes to express the channel connectivity, capable of incorporating information on the quality of the connectivity through the evaluation of channel amalgamation. When applied to the same set of reservoir equi-probable realizations, these indexes proved that a more effective selection of the geological realizations can be made to capture the uncertainty affecting the forecasted reservoir production performance.

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Håkonsen, Greg Harald. "Joint Source-Channel Coding for Image Transmission over Flat Fading Channels." Doctoral thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1695.

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In this thesis, transmission of images over a at fading channel using joint source-channel coding (JSCC) is considered. Through the use of nonlinear dimensional changing mappings, the system becomes robust. The system will not experience a clear breakdown, but have a graceful degradation which is visually pleasant. It is shown how multiple ways of adapting the source to the channel, and using the knowledge about the channel, results in a performance comparable to state-of-the-art systems but with less complexity. By relying on the robustness, reduction in channel information does not mean a large loss in performance.

The proposed system has low computational complexity as there are no separate source and channel coders. Compression and generation of channel symbols are done in one operation. By using nonlinear dimensional changing mappings, the dependency between the channel symbols are low. This leads to a system where the received image can be progressively decoded, and where the received information is still usable if the transmission stops unexpectedly.

By allowing a small variation around target time and transmission power constraints, the variation of the quality of the received image is kept small. This is done through planning and on-the-fly adaptation of the transmission. The planning depends on the distribution of the channel quality, and makes sure the channel is used bandwidth efficiently.

Through the results, the impact and importance of the design of some of the system parameters are analyzed and discussed.

By using theoretical models, it is shown how practical limitations of the system contributes to loss in performance. Similar techniques are also used to analyze where in the system effort should be made to improve the system.

The proposed system has a framework that can be easily extended to other scenarios.

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Zeydan, Engin. "Channel Phase And Data Estimation In Slowly Fading Frequency Nonselective Channels." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607419/index.pdf.

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In coherent receivers, the effect of the multipath fading channel on the transmitted signal must be estimated to recover the transmitted data. In this thesis, the channel phase and data estimation problems are investigated in a transmitted data sequence when the channel is modeled as slowly fading, frequency non-selective channel. Channel phase estimation in a transmitted data sequence is investigated and data estimation is obtained in a symbol-by-symbol MAP receiver that is designed for minimum symbol error probability criterion. The channel phase is quantized in an interval of interest, the trellis diagram is constructed and Viterbi decoding algorithm is applied that uses the phase transition and observation models for channel phase estimation. The optimum coherent and noncoherent detectors for binary orthogonal and PSK signals are derived and the modulated signals in a sequence are detected in symbol-by-symbol MAP receivers.Simulation results have shown that the performance of the receiver with phase estimation is between the performance of the optimum coherent and noncoherent receiver.

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Mongol, Bayarpurev, Takaya Yamazato, Hiraku Okada, and Masaaki Katayama. "Channel Estimation for BFDM/OQAM System in Dispersive Time-Varying Channels." IEEE, 2006. http://hdl.handle.net/2237/7762.

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Song, Xuegui. "Channel estimation techniques for OFDM systems in dispersive time-varying channels." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/8897.

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Coherent modulation is more effective than differential modulation for orthogonal frequency division multiplexing (OFDM) systems requiring high data rate and spectral efficiency. Channel estimation is therefore an integral part of the receiver design. In this thesis, two iterative maximum likelihood based channel estimation algorithms are proposed for an OFDM system in dispersive time-varying channels. A multipath channel model is proposed for OFDM uplink transmission in macrocellular systems. The multipath fading channel is modeled such that the channel state can be determined by estimating the unknown channel parameters. A second-order Taylor series expansion is adopted to simplify the channel estimation problem. Based on the system model, an iterative maximum likelihood based algorithm is first proposed to estimate the discrete-time channel parameters. The mean square error performance of the proposed algorithm is analyzed using a small perturbation technique. Based on a convergence rate analysis, an improved iterative maximum likelihood based channel estimation algorithm is presented using a successive overrelaxation method. Numerical experiments are performed to confirm the theoretical analyses and show the improvement in convergence rate of the improved algorithm.

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Wang, Yi. "Joint OFDM symbol detection and channel estimation over doubly selective channels." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121486.

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Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique for high data rate transmission, that is widely used in modern wireless communication systems because of its good performance over frequency selective channels. However OFDM systems are sensitive to channel time variation resulting in Inter-Carrier Interference (ICI), that without suitable detection methods can degrade performance. Channel State Information (CSI) is essential to various OFDM data detection schemes and its acquisition is a critical factor, in particular over time-varying channels. This work considers a technique for integrating the Kalman filter channel estimation with a version of Sphere Decoding (SD) adapted to OFDM detection. By modelling the OFDM system in frequency domain as a Multiple Input Multiple Output (MIMO) system, we derive a powerful SD technique for data detection. By approximating the channel matrix as banded, we are able to maintain a feasible complexity for SD and deliver competitive performance when compared to other existing scheme. For acquisition of CSI, the Basis Expansion (BE) method is used to model the time-varying channels and a Kalman filter is constructed for tracking. The Kalman filter employs decision-feedback from the SD, requiring only a low pilot symbol density, and hence improves bandwidth efficiency. The performance of this scheme is evaluated by Monte-Carlo computer simulations. Results show that compared with competing algorithm, this scheme provides performance gains. When it is used over moderate time-varying LTE channels, this scheme shows good performance even in the presence of carrier phase noise.
Le multiplexage par répartition en fréquence orthogonale (OFDM, pour Orthogonal Frequency Division Multiplexing) est une technique prometteuse pour la transmission de données à haut débit. Il est largement utilisé dans les systèmes de communication sans fil actuels en raison de ses bonnes performances sur les canaux sélectifs en fréquence. Toutefois, les systèmes reposant sur l'OFDM sont sensibles aux variations de temps de voie, qui entraînent un brouillage inter-porteuses (ICI, pour Inter-Carrier Interference). En l'absence de méthodes de détection appropriée, ce brouillage peut réduire les performances. Les informations d'état de canal (CSI, pour Channel State Information) constituent un élément essentiel des divers systèmes de détection de données basés sur l'OFDM et leur acquisition est un facteur crucial, surtout sur les canaux variables en temps. La présente examine une technique permettant d'intégrer l'évaluation de canaux reposant sur un filtre de Kalman à une variante du décodage par sphères (SD, pour Sphere Decoding) adaptée à la détection OFDM. En modélisant le système d'OFDM dans le domaine fréquentiel comme un système « entrées multiples, sorties multiples » (MIMO, pour Multiple Input Multiple Output), nous obtenons une puissante technique de SD pour la détection des données. En tenant pour acquis que la matrice de canal est une matrice bande, il est possible de maintenir une complexité recelant le potentiel pour une implantation réelle du SD et d'obtenir des performances concurrentielles comparativement à d'autres systèmes existants. En ce qui a trait à l'acquisition des CSI, on utilise la méthode de l'« expansion de base » (BE, pour Basis Expansion) pour modéliser les canaux variables en temps et on crée un filtre de Kalman pour le suivi des variations de temps des canaux. Le filtre de Kalman utilise les retours de décisions tirés du SD. Il ne nécessite ainsi qu'une faible densité de symboles pilotes, ce qui accroît l'optimisation de la bande passante. Les performances de ce système sont évaluées à l'aide de simulations informatiques reposant sur la méthode de Monte-Carlo. Les résultats montrent que par rapport à l'algorithme mis en concurrence, ce système permet des gains de performance. Quand il est utilisé sur des canaux LTE (Long Term Evolution) modérément variables en temps, ce système atteint une bonne performance, même en présence de brouillage de la phase des porteuses.

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Clark, Alan Douglas. "Analysis and design of source/channel codes for noisy communication channels." Thesis, De Montfort University, 1987. http://hdl.handle.net/2086/4246.

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37

Wong, K.-H. H. "Transmission of channel coded speech and data over mobile radio channels." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235340.

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Choi, Jihwan Patrick 1975. "Channel prediction and adaptation over satellite channels with weather-induced impairments." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9070.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
Includes bibliographical references (leaves 85-87).
Title as it appears in MIT commencement exercises program, June 2000: Satellite channels with weather-induced impairments.
Bad weather conditions, especially due to rain, cause satellites operating at high frequencies (above 10 GHz) to have significant link attenuation. Usually extra link margins are used to assure link availability. These margins cause inefficient use of precious satellite and terminal power, and unnecessarily limit data throughputs. Efficiency improvements using channel prediction and adaptation over satellite channels with weather-induced impairments are considered in this thesis. First, we consider scintillation and rain attenuation as two dominant factors for signal fading over satellite-earth paths above 10 GHz, and explore physical and mathematical modeling of the two processes. Statistical and spectral analyses of these processes using one or two pole autoregressive (AR) models yield simple linear estimators for the received signal attenuation. Using these estimators, we present results where we can predict the received signal attenuation within ±0.5 dB 1 second ahead and within ± 1.0 dB 4 seconds ahead. For adaptation, we change the signal transmission power, the modulation symbol size, and the code rate adaptively. In particular, we suggest a continuous power control and discrete rate control strategy, through which we build a set of modulation/code states, and discretely change the modulation symbol size and the code rate from state to state. Within each state, continuous power control is implemented. Several examples that use this technique and quantitative analyses of power increase and capacity are provided. The analyses indicate that there is a substantial gain in performance either in capacity and/or power consumption with the adaptive schemes.
by Jihwan Patrick Choi.
S.M.

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Liang, Yifan. "Separation optimality and generalized source-channel coding for time-varying channels /." May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.

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40

Pachai, Kannu Arun. "Communications over noncoherent doubly selective channels." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173887288.

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41

Thompson, Christopher Hal. "Identification and characterization of a peptide toxin inhibitor of ClC-2 chloride channels." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26604.

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Thesis (Ph.D)--Biology, Georgia Institute of Technology, 2009.
Committee Chair: McCarty, Nael; Committee Co-Chair: Harvey, Stephen; Committee Member: Hartzell, Criss; Committee Member: Kubanek, Julia; Committee Member: Lee, Robert. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Craven, Kimberley Beth. "Structural rearrangements during gating in cyclic nucleotide-modulated channels /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10654.

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Panagos, Adam G., and Kurt Kosbar. "A GRAPHICAL USER INTERFACE MIMO CHANNEL SIMULATOR." International Foundation for Telemetering, 2004. http://hdl.handle.net/10150/605799.

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International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California
Multiple-input multiple-output (MIMO) communication systems are attracting attention because their channel capacity can exceed single-input single-output systems, with no increase in bandwidth. While MIMO systems offer substantial capacity improvements, it can be challenging to characterize and verify their channel models. This paper describes a software MIMO channel simulator with a graphical user interface that allows the user to easily investigate a number of MIMO channel characteristics for a channel recently proposed by the 3rd Generation Partnership Project (3GPP).

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44

Teotia, Seemant. "Influence of the Number of Degrees of Freedom on the Capacity of Incoherent Optical Fiber Communication Systems." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/27497.

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The purpose of this dissertation is to find the channel capacity in optical fiber communication systems when incoherent detection is used with single (polarization filtering) and two-polarizations (no polarization filtering). Optical fiber systems employ photodetectors that convert optical intensity to electrical current. Bandpass vector fields may be represented by four orthogonal baseband components corresponding to two quadrature phases and two orthogonal polarizations. Intensity is proportional to the sum of the squares of these four components. In the case of a coherent receiver, a strong optical local oscillator (in phase and with same polarization as the signal) is added to the signal prior to the photodetector. This results in the removal of the quadrature phase and polarization components, and reduces to the one degree of freedom (DOF) case of signal plus local oscillator shot noise for which the Shannon channel capacity formula applies. Electrical noise following the photodetector may also be neglected if there is an optical amplifier before the photodetector in the receiver. The amplifier introduces amplified spontaneous emission noise containing both quadrature phase components and both polarizations (4 DOFs), but the 2 DOF case would result if a polarization filter were used. Although the 1 and 2 DOF cases are of less practical interest than the 4 DOF case, they provide useful benchmarks for comparing performance limits. We evaluate both spectral efficiency limits (bps/Hz) in the limit of high and low SNR for the 1,2 and 4 DOF cases and also find the power efficiency (minimum number of photons per bit) for each of these cases. It is shown that for high SNR the spectral efficiency is the same independent of the number of DOFs and that the half-Gaussian distribution is the optimum distribution. We are able to thus obtain a compact equation for spectral efficiency which behaves in a similar way to the Shannon capacity formula but with the SNR scaled by a constant. We also show that for low SNR the half-Gaussian distribution is not the optimum distribution as the slope of the mutual information changes with the square of SNR which would lead to the number of photons per bit becoming infinite in the limit of SNR going to zero. We use a modified half-Gaussian distribution which has a discrete component (an impulse function at the origin) and provide a simple proof that this distribution results in a mutual information that goes to zero linearly with SNR resulting in a minimum number of photons per bit. Furthermore, by increasing the magnitude of the discrete component at the origin, it is shown that the minimum number of photons per bit for the incoherent channel approaches that of the coherent channel.
Ph. D.

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Matulef, Kimberly Irene. "Cysteine-scanning mutagenesis of the ligand-binding domain of cyclic nucleotide-gated channels /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/5032.

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Neff, Stephan. "Heavy-ion beam transport in plasma channels transport properties and channel stability /." [S.l. : s.n.], 2005. http://elib.tu-darmstadt.de/diss/000561.

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Donini, Oreola Anna Teresa. "Ion channels in motion, developing computational approaches to dynamic ion channel modeling." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35957.pdf.

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Song, Liying Tugnait Jitendra K. "Channel estimation and equalization for doubly-selective channels using basis expansion models." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Dissertation/Song_Liying_29.pdf.

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49

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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Holm, Henrik. "Adaptive Coded Modulation Performance and Channel Estimation Tools for Flat Fading Channels." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2150.

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The need for spectrally efficient transmission on mobile and wireless channels is prevalent. A promising scheme for such transmission is adaptive coded modulation. In this thesis, techniques for assessing the performance of such systems are presented. One of the vulnerable points of such systems is the need for a reliable feedback channel. Channel prediction is proposed as a technique to combat the harmful effects of feedback delay. The Nakagami distribution is often employed in a model for the fading envelope of a wireless channel; this leads to a gamma-distributed signal-to-noise ratio. Nakagami (1960) provides expressions for the probability density function (PDF) of the product, sum, and ratio of two correlated gamma-distributed random variables (RVs). However, such an expression for the difference between two such RVs has not been provided by Nakagami. Anew expression for this PDF is provided in this dissertation, and it is shown that it is closely related to a distribution first described by McKay (1932). Applications of the new PDF include outage probability calculation in an environment with self-interference and assessment of the quality of certain channel estimation techniques.

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Dissertations / Theses on the topic 'Channeled'

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