Dissertations / Theses on the topic 'Transmission properties'
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1
Reisemann, Matthias Heinrich. "Ultrasonic transmission properties of sea ice." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624200.
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Sahin, Levent. "Transmission And Propagation Properties Of Novel Metamaterials." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610277/index.pdf.
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Metamaterials attracted significant attention in recent years due to their potential to create novel devices that exhibit specific electromagnetic properties. In this thesis, we investigated transmission and propagation properties of novel metamaterial structures. Electromagnetic properties of metamaterials are characterized and the resonance mechanism of Split Ring Resonator (SRR) structure is investigated. Furthermore, a recent lefthanded metamaterial structure for microwave regime called Fishnet-type metamaterial is studied. We demonstrated the left-handed transmission and negative phase velocity in Fishnet Structures. Finally, we proposed and successfully demonstrated novel approaches that utilize the resonant
behavior of SRR structures to enhance the transmission of
electromagnetic waves through sub-wavelength apertures at microwave frequency regime. We investigated the transmission enhancement of electromagnetic waves through a sub-wavelength aperture by placing SRR structures in front of the aperture and also by changing the aperture shape as SRR-shaped apertures. The incident electromagnetic wave is
effectively coupled to the sub-wavelength aperture causing a strong localization of electromagnetic field in the sub-wavelength aperture. Localized electromagnetic wave gives rise to enhanced transmission from a single sub-wavelength aperture. The proposed structures are designed, simulated, fabricated and measured. The simulations and experimental
results are in good agreement and shows significant enhancement of electromagnetic wave transmission through sub-wavelength apertures by utilizing proposed novel structures. Radius (r) of the sub-wavelength aperture is approximately twenty times smaller than the incident
wavelength (r/λ
~0.05). This is the smallest aperture size to wavelength ratio in the contemporary literature according to our knowledge.
3
Jiang, Leaf Alden 1976. "Propagation properties of duobinary transmission in optical fibers." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46195.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (leaves 121-126).
by Leaf Alden Jiang.
B.S.
M.Eng.
4
Chen, Jianbing James 1971. "Transmission and reflection properties of layered left-handed materials." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38681.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2007.Includes bibliographical references (p. 179-189).
This thesis is concerned with the reflection and transmission properties of layered left-handed materials (LHM). In particular, the reflection properties of (LHM) slabs are studied for the Goos-Hanchen (GH) lateral shift phenomenon. We demonstrate a unique GH lateral shift phenomenon, which shows that both positive and negative shifts can be achieved using the same LHM slab configuration. This phenomenon is different from previously established cases where the GH lateral shift can be only negative or only positive when different LHM slab configurations are used. We also show that there exist two distinct cases with this unique phenomenon. One case has two regions of incident angles where the GH lateral shift directions are different, while another case has three regions with alternated GH shift directions. A generalized analytical formulation for analyzing the GH lateral shift direction is provided, which reveals that this unique phenomenon is related to the relative amplitudes of the growing and decaying evanescent waves inside the LHM slabs. The energy flux patterns within LHM slabs are further studied to show the influence of the evanescent waves on the GH shift direction change.
(cont.) Furthermore, the transmission property of LHM slabs are studied on the finite slabs' maging capability. First, the development of the numerical simulation tool - the Finite-Difference Time-Domain method (FDTD) - investigates the ability of the method to model a perfect lens made of a slab of homogeneous LHM. It is shown that because of the frequency dispersive nature of the medium and the time discretization, an inherent mismatch in the constitutive parameters exists between the slab and its surrounding medium. This mismatch in the real part of the permittivity and permeability is found to have the same order of magnitude as the losses typically used in numerical simulations. Hence, when the LHM slab is lossless, this mismatch is shown to be the main factor contributing to the image resolution loss of the slab. In addition, finite-size LHM slabs are studied both analytically and numerically since they have practical importance in the actual experiments. The analytical method is based on Huygens' principles using truncated current sheets that cover only the apertures of the slabs. It is shown that the main effects on the images' spectra due to the size of the slabs can be predicted by the proposed analytical method, which can, therefore, be used as a fast alternative to numerical simulations.
(cont.) Furthermore, the property of negative energy streams at the image plane is also investigated. This unique property is found to be due to the interactions between propagating and evanescent waves and can only occur with LHM slabs, of both finite-size and infinite size. The last part of the thesis deals with multi-layered media for the application to antenna isolations. The setup is with two horn antennas located beneath the ground plane with 10 A distance apart. In order to reduce the coupling between antennas, multi-layered media placed on top of the ground plane need to be designed to suppress the fields. After the problem is simplified to the dipole antenna coupling in infinite slabs, the method to evaluate the fields inside layered media is presented. This method obtains the spectral domain Green's function first and then transforms the fields to the spatial domain using the Sommerfeld-type integration. After the method is validated using right-handed materials (RHM) from references, it is extended to include media like LHM as well as p. negative material and : negative material . The validation with these materials are done by comparing the results with CST microwave studio simulations. The first configuration for the antenna isolation design if one layer slab backed by the grounded plane. Two different approaches are used to find the optimum slab parameters for the isolation.
(cont.) One approach is to use Genetic Algorithm (GA) to optimize the slab's constitutive parameters and the thickness for a minimum coupling level. The other approach is to develop an analytic asymptotic expression for the field, and then used the expression to design the slab parameters for the best isolation. We conclude that both approaches yield the same design for the given configuration. The effectiveness of the design is also validated on a grounded finite slab, which is the representation of the actual application. Finally, multi-layered media for the antenna isolation is studied. GA method is applied with an optimization scheme tailed for a five layered structure. We show that GA converges very fast to the solution and the result yields satisfactory isolation between the antennas.
by Jianbing James Chen.
Ph.D.
5
Coneybeer, Robert T. "Transient thermal models for substation transmission components." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/17686.
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Weis, R. Stephen. "Electromagnetic transmission and reflection characteristics of anisotropic multilayered structures." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/13546.
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Paul, John. "Modelling of general electromagnetic material properties in TLM." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267589.
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Woo, Kwangje. "Transmission properties of sub-wavelength hole arrays in metal films." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015340.
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Bilge, Serafettin. "Transmission Properties Of Fishnet Structure As A Left Handed Metamaterial." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610467/index.pdf.
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Left handed metamaterials are one of the most populer topic attracting attentions of scientists nowadays. Metamaterials are engineered materials which can possess inordinary properties when compared with common materials existing in nature. The main structure investigated in this thesis is fishnet metamaterial which is a left handed metamaterial. Firstly some left handed metamaterials and their properties are surveyed. A retrieval procedure in order to obtain permittivity, permeability and refractive index of any periodic material was summarized. Left handedness of fishnet structure was investigated and proven numerically. Effects of change in polarization of an incoming wave to symmetric and asymmetric fishnet structure were searched. A parametric analysis of fishnet structure was done. Phase advance in a three layered fishnet structure was investigated and compared with phase advance in an ordinary material. Fishnet wedge structure was surveyed and negative refraction and negative phase advance in this structure are shown. Finally, some types of disorderness of fishnet structure, then its effects on transmission results and retrieval results are demonstrated. In order to obtain transmission and reflection through a material, CST Microwave Studio®was used. A code following a numerical procedure in order to retrieve constitutive parameters of a periodic structure which was written in Matlab®
was used in this thesis.
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Ramanathan, Sathish Kumar. "Sound transmission properties of honeycomb panels and double-walled structures." Doctoral thesis, KTH, MWL Marcus Wallenberg Laboratoriet, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96538.
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Sandwich panels with aluminium face sheets and honeycomb core material have certain advantages over panels made of wood. Some of the advantages of these constructions are low weight, good moisture properties, fire resistance and high stiffness to-weight ratio etc. As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist during early design stages. In this thesis, tools are developed for predicting the sound transmission through honeycomb panels, typical for inner floors in trains and later through double-walled structures typical for rail-vehicles, aircrafts and ships. The sandwich theory for wave propagation and standard orthotropic plate theory is used to predict the sound transmission loss of honeycomb panels. Honeycomb is an anisotropic material which when used as a core in a sandwich panel, results in a panel with anisotropic properties. In this thesis, honeycomb panels are treated as being orthotropic and the wavenumbers are calculated for the two principal directions. The wavenumbers are then used to calculate the sound transmission using standard orthotropic theory. These predictions are validated with results from sound transmission measurements. The influence of constrained layer damping treatments on the sound transmission loss of these panels is investigated. Results show that, after the damping treatment, the sound transmission loss of an acoustically bad panel and a normal pane lare very similar. Further, sound transmission through a double-leaf partition based on a honeycomb panel with periodic stiffeners is investigated. The structural response of the periodic structure due to a harmonic excitation is expressed in terms of a series of space harmonics and virtual work theory is applied to calculate the sound transmission. The original model is refined to include sound absorption in the cavity and to account for the orthotropic property of the honeycomb panels. Since the solution of the space harmonic analysis is obtained in a series form, a sufficient number of terms has to be included in the calculation to ensure small errors. Computational accuracy needs to be balanced with computational cost as calculation times increases with the number of terms. A new criterion is introduced which reduces the computational time by up to a factor ten for the panels studied. For all the double-leaf systems analysed, the sound transmission loss predictions from the periodic model with the space harmonic expansion method are shown to compare well with laboratory measurements.QC 20120607
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Heydarnejad, Jahangir. "Molecular characterization and transmission properties of Iranian wheat stripe virus." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250732.
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Karlsson, Linda. "Transmission Electron Microscopy of 2D Materials : Structure and Surface Properties." Doctoral thesis, Linköpings universitet, Tunnfilmsfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127526.
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During recent years, new types of materials have been discovered with unique properties. One family of such materials are two-dimensional materials, which include graphene and MXene. These materials are stronger, more flexible, and have higher conductivity than other materials. As such they are highly interesting for new applications, e.g. specialized in vivo drug delivery systems, hydrogen storage, or as replacements of common materials in e.g. batteries, bulletproof clothing, and sensors. The list of potential applications is long for these new materials. As these materials are almost entirely made up of surfaces, their properties are strongly influenced by interaction between their surfaces, as well as with molecules or adatoms attached to the surfaces (surface groups). This interaction can change the materials and their properties, and it is therefore imperative to understand the underlying mechanisms. Surface groups on two-dimensional materials can be studied by Transmission Electron Microscopy (TEM), where high energy electrons are transmitted through a sample and the resulting image is recorded. However, the high energy needed to get enough resolution to observe single atoms damages the sample and limits the type of materials which can be analyzed. Lowering the electron energy decreases the damage, but the image resolution at such conditions is severely limited by inherent imperfections (aberrations) in the TEM. During the last years, new TEM models have been developed which employ a low acceleration voltage together with aberration correction, enabling imaging at the atomic scale without damaging the samples. These aberration-corrected TEMs are important tools in understanding the structure and chemistry of two-dimensional materials. In this thesis the two-dimensional materials graphene and Ti3C2Tx MXene have been investigated by low-voltage, aberration-corrected (scanning) TEM. High temperature annealing of graphene covered by residues from the synthesis is studied, as well as the structure and surface groups on single and double Ti3C2Tx MXene. These results are important contributions to the understanding of this class of materials and how their properties can be controlled.
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Xie, Yong. "Transmission Properties of Sub-Wavelength Metallic Slits and Their Applications." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195217.
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With the manufacture of nano-scale features in the last ten years, it is possible to do optical experiments on features as small as a tenth/hundredth wavelength. It turns out that the experimental data cannot be explained by classical diffraction theories. Thus, it is necessary to develop new methods or use existing approaches which are effective in other fields, to solve problems in photonics. We use finite difference time domain (FDTD), to study transmission properties of sub-wavelength slits in a metallic film. By doing simulations on periodic and single slits, we confirm that the TE mode has a cutoff while a TM mode always has a propagating mode in the small apertures. Then we find that the transmittance is minimum when the array period is equal to the wavelength of surface plasmon polariton (SPP) at normal incidence. In fact, the SPP-like waves exist in both periodic and isolated slits, and they help the transmittance of small apertures. In order to establish the role of SPP in the transmission mechanism, it is necessary to single out each mode from the total fields. We developed Bloch mode method (BMM) to calculate the amplitudes of the lowest N orders, and the amplitudes tell us which one is dominant (not including the guided mode) at high and low transmission. BMM converges very fast and it is more accurate than FDTD since it does not suffer from numerical dispersion. Both methods can resolve the Wood anomaly and SPP anomaly; however, FDTD converges very slowly at the SPP resonance and oscillates around the value obtained through BMM at the Wood anomaly. BMM is not sensitive to material types, incident angles, and anomalies; it will be a useful tool to investigate similar problems.
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Rosenthal, Tobias. "Transmission electron microscopy and properties of thermoelectric chalcogenides and luminescent oxonitridosilicates." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-174902.
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Shemuly, Dana. "Design and measurements of novel electromagnetic properties in spiral transmission fibers." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76118.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 92-96).
One dimensional photonic band gap fibers have proven to be fascinating and versatile devices, as demonstrated by many applications. The ability to control and design these fibers to achieve specific functionalities will enable us to advance the research done with these fibers and to gain new applications. In this work we explore our ability to control different fabrication parameters to design a fiber according to certain requirements. We use these capabilities to design and fabricate a near IR fiber for high peak power laser transmission. Since a multimode fiber supports many modes one can gain further control over fiber properties by controlling modal content in the fiber. We developed two techniques for controlled coupling and demonstrated them using one dimensional photonic band gap fibers. Using a spatial light modulator, one can dynamically control the modal content in the fiber, including superposition of more than one mode. We experimentally demonstrate this capability by coupling to one of two modes and superposition of the two. Using a static technique, we experimentally demonstrate a single-mode transmission of the azimuthally polarized mode (TEoi) in a highly multimode cylindrical photonic band gap fiber. Theoretical calculations verify the validity of this technique and accurately predict the coupling efficiency. Single-mode propagation in a large hollow core fiber can enable numerous applications, especially in control of particles along the entire length of the fiber. Finally, we examined the effects of the spiral cross-section of the fiber on its optical properties. The fiber's chiral symmetry combined with its infinite translational symmetry creates a truly planar chiral structure, similar to many artificial chiral structures recently studied. The low-symmetry geometry of the fiber, which lacks any rotational and mirror symmetries, exclusively supports modes with angular momentum greater than zero and shows in-principle directional optical activity and asymmetric propagation. We use general symmetry arguments to provide qualitative analysis of the waveguide's modes and numerically corroborate this using finite element simulation. We also demonstrated these properties experimentally using spiral fibers.
by Dana Shemuly.
Ph.D.
16
van, Doremalen Neeltje. "Receptor binding properties, cell tropism and transmission of influenza A virus." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/10738.
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The first influenza pandemic of the 21st century was caused by the influenza A (H1N1) 2009 virus (A(H1N1)pdm09) that emerged from a swine-origin source. Although human infections with swine-origin influenza have been reported intermittently in the past decade, none went on to cause a pandemic or sustained human-to-human transmission. In previous pandemics, specific residues in the receptor binding site of the haemagglutinin (HA) protein of influenza have been associated with the ability of the virus to transmit between humans. In this thesis the effect of mutations at residue 227 in HA on cell tropism and transmission of A(H1N1)pdm09 is described. In A(H1N1)pdm09 and previous seasonal H1N1 viruses this residue is glutamic acid (E), whereas in swine influenza it is alanine (A). Using human airway epithelium, a differential cell tropism of A(H1N1)pdm09 compared to A(H1N1)pdm09 E227A and swine influenza was shown suggesting this residue may alter the sialic acid conformer binding preference of the HA. Furthermore, multi-cycle viral growth of both A(H1N1)pdm09 E227A and swine influenza was found to be attenuated in comparison to A(H1N1)pdm09 in human airway epithelium. However this altered tropism and viral growth in human airway epithelium did not abrogate respiratory droplet transmission of A(H1N1)pdm09 E227A in ferrets. This suggests that acquisition of 227E was not solely responsible for the ability of A(H1N1)pdm09 to transmit between humans. Because the work with the E227A mutant showed that small differences in cell tropism that may affect influenza virus transmissibility could be detected in human airway cells, a receptor binding assay was developed for laboratory surveillance using commercial human airway epithelium cultures, to screen for zoonotic influenza strains of particular concern for human health. To further investigate adaptations by influenza virus for infection of the human host, the cell tropism determined by the HA protein of an avian H7N7 and human H7N3 isolate was compared. Binding to non-ciliated human airway cells was increased for the human isolate. This human case of H7N3 infection yielded two isolates from different sites (eye and throat) from the same patient on the same day. A whole genome sequencing assay was designed for H7 isolates and both eye and throat isolate were fully sequenced. One synonymous nucleotide change was found in the NS gene segment and one synonymous and two non-synonymous nucleotide changes were found in the PB2 gene segment. Comparison of the non-synonymous changes in the protein sequence of PB2 to available avian and human virus PB2 sequences revealed that the substitutions in the eye isolate were comparatively uncommon. Interestingly, these changes resulted in an increased viral growth in human airway epithelial cells at 32ºC when compared to the throat isolate, a phenomenon which was not observed at 37ºC. Finally, the use of a lung model maintained by the ex-vivo lung perfusion (EVLP) technique for study of virus infection was tested. This technique allows the use of both human and porcine lungs up to 24 hours after abstraction and is a potential model for respiratory pathogens and novel treatments. Porcine lungs were infected with A(H1N1)pdm09. Physiological and virological parameters were measured in two separate experiments and infection was demonstrated by increased viral loads in samples obtained at late time points after infection.
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Wilkinson, Sonja Renae. "A study of the optical transmission properties of the polymer HPG /." Full-text version available from OU Domain via ProQuest Digital Dissertations, 2000.
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Stanislavov, A. S., L. B. Sukhodub, V. N. Kuznetsov, Леонід Федорович Суходуб, Леонид Федорович Суходуб, and Leonid Fedorovych Sukhodub. "Magnetite-polymer Nanoparticles: Structure and Properties." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42573.
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The paper describes synthesis of magnetite-alginate composites. The main feature of such biomaterials is the simultaneous formation of magnetite nanoparticles inside the alginate matrix. Obtained samples were characterized by X-ray diffraction and transmission electron microscopy. In several samples the secondary phase of ammonium chloride was observed. The average crystallite sizes of magnetite phase are about 13 nm. The addition of alginate leads to the decrease of microstrains in [h k 0] direction.
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Hu, Boxi David, and Martens Dan Von. "Transmission Properties of an Electron in One Dimensional Crystals with Periodic Potentials." Thesis, KTH, Teoretisk fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103463.
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In 2010, R. Olsen and G. Vignale, published a paper presenting a recursive method for calculating electron transmission probability for one dimensional periodic potentials. Based on their method, this thesis studies electron transmission in a one dimensional lattice of periodic potential barriers both using a classical and quantum mechanical description. The transmission is measured by the transmission probability of the system. The transmission probabilities are computed with regards to two separate variables, namely the number of potential barriers, i.e. the length of the lattice, and the wave number of the incident electron. These computations are made using rectangular and Dirac delta potential barriers respectively. Lastly, the paper expands on the area of disordered systems of periodic potentials by introducing irregularities in potential size and separation.
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Kennedy, Christopher. "Properties of High Energy Laser Light Transmission through Large Core Optical Cables." Master's thesis, University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5797.
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Laser induced damage is of interest in studying the transmission of large amounts of optical energy through step-index, large core multimode fibers. Optical fibers often have to be routed around objects when laser light is being transmitted between two locations which require the fiber to bend into a curve. Depending on how tight the bend is, this can result in transmission losses or even catastrophic damage when the energy density of the laser pulse exceeds the damage threshold of silica glass. Waveguide theory predicts that light traveling through a bend will form whispering-gallery modes that propagate through total internal reflection bounces along the inside of the outer edge of the bend. This is critical since in these locations the energy density of the light will increase significantly, raising the potential of laser damage, nonlinear effects, and transmission losses. This loss is especially problematic when two 90[degree] bends going in opposite directions are in close proximity to each other, forming an 'S-bend'. Light that is grouped along the outer edge going through the first bend will enter the second bend at a sharper angle which causes much high transmission losses and raises the possibility of failure. Models using R-Soft BeamProp and Zemax were developed to study transmission losses, investigate light interactions at critical areas, and predict under which conditions laser damage would occur. BeamProp presents a clearer view of the modal distribution of light within the core of the fiber and is used to analyze how a plane wave with a Gaussian intensity distribution excites the fiber modes. Zemax provides a tool to perform non-sequential ray tracing through the fiber cable and stray light analysis within the core and once the light exits the fiber. Intensity distributions of the cross sectional area of the fiber shows the whispering gallery modes forming as the light propagates around bends and disburses as it propagates afterwards. It was discovered using R-Soft that if the separation distance between bends in an S-bend is approximately 3 mm there exists a condition where maximum transmission occurs. For 365 μm diameter core fiber it was calculated that the difference in output power could be as high as 150%. This was initially completely unexpected; however ray tracing using Zemax was able to verify that this distance allows the light to transition so that it enters the 2nd bend at the optimal angle to enter the whispering gallery mode. Experiments were performed that validated the models' predictions and images were captured clearly showing the spatial distribution shift of the light within the core of the fiber. Experiments were performed to verify light grouping together to form whispering gallery modes as predicted by Zemax. Microscope images were taken as a function of distance from various bends to observe the periodic nature in which the laser light fills up the fiber. Additionally, a configuration was setup to examine stimulated Brillioun scattering and determine the onset of laser damage in the fiber. Fibers were tested as a function of bend radius and number of shots and recommendations for future systems were made. Lastly, mechanical failure tests were performed to determine the relationship between stress placed on the fiber through bending and fiber lifetime in a static environment. This allowed a minimum safe bend radius to be calculated for a 30 year lifetime that agreed with previous calculated values.M.S.
Masters
Optics and Photonics
Optics and Photonics
Optics
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Galand, Quentin. "Experimental investigation of the diffusive properties of ternary liquid systems." Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209626.
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A fundamental step in the further developments of comprehensive modelling of the diffusive processes in liquids requires the possibility of obtaining reliable and accurate experimental data of the diffusion and thermodiffusion coefficients of multicomponent liquid systems. In the present work, we perform an experimental investigation of the diffusive properties of binary and ternary liquid systems. Two experimental techniques, the ‘Open Ended Capillary’ technique and the ‘Transient Interferometric Technique’ have been developed. Those techniques have been used for the experimental characterization of several systems composed of 1,2, 3,4-Tetrahydrnaphtalene, Isobutylbenzene and Dodecane at ambient temperature. Those particular species were selected as a simplified multicomponent system modelling the fluids contained in natural crude oils reservoirs. For each of these techniques, experimental set-ups were designed, implemented and calibrated. The procedures for identifying the ternary diffusion coefficients from the measured compositions fields were studied in details.
The Open Ended Capillary Technique was applied under gravity condition to study isothermal diffusion binary and ternary systems. Difficulties related to a new procedure for interpreting the data collected at short times of the experiments are highlighted and its implication in the generalization of the technique for the study of multicomponent systems is discussed.
The Transient Interferometric Technique was used to perform an experimental study of three binary systems under gravity conditions. It was also applied for the investigation of ternary systems under microgravity condition in the frame of the DSC on SODI experiment, which took place aboard the International Space Station in 2011. The experimental results are reported and the analysis of the accuracy of the technique is presented. The TIT is the first technique ever providing accurate experimental measurements of the complete set of diffusion and thermodiffusion coefficients for ternary liquid systems.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Fan, Jing, and 范菁. "Heat transport in nanofluids and biological tissues." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47752853.
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The present work contains two parts: nanofluids and bioheat transport, both involving
multiscales and sharing some common features. The former centers on addressing the
three key issues of nanofluids research: (i) what is the macroscale manifestation of
microscale physics, (ii) how to optimize microscale physics for the optimal system
performance, and (iii) how to effectively manipulate at microscale. The latter
develops an analytical theory of bioheat transport that includes: (i) identification and
contrast of the two approaches for developing macroscale bioheat models: the
mixture-theory (scaling-down) and porous-media (scaling-up) approaches, (ii)
rigorous development of first-principle bioheat model with the porous-media
approach, (iii) solution-structure theorems of dual-phase-lagging (DPL) bioheat
equations, (iv) practical case studies of bioheat transport in skin tissues and during
magnetic hyperthermia, and (v) rich effects of interfacial convective heat transfer,
blood velocity, blood perfusion and metabolic reaction on blood and tissue macroscale
temperature fields.
Nanofluids, fluid suspensions of nanostructures, find applications in various
fields due to their unique thermal, electronic, magnetic, wetting and optical properties
that can be obtained via engineering nanostructures. The present numerical simulation
of structure-property correlation for fourteen types of two/three-dimensional
nanofluids signifies the importance of nanostructure’s morphology in determining
nanofluids’ thermal conductivity. The success of developing high-conductive
nanofluids thus depends very much on our understanding and manipulation of the
morphology. Nanofluids with conductivity of upper Hashin-Shtrikman bounds can be
obtained by manipulating structures into an interconnected configuration that
disperses the base fluid and thus significantly enhancing the particle-fluid interfacial
energy transport. The numerical simulation also identifies the particle’s radius of
gyration and non-dimensional particle-fluid interfacial area as two characteristic
parameters for the effect of particles’ geometrical structures on the effective thermal
conductivity. Predictive models are developed as well for the thermal conductivity of
typical nanofluids.
A constructal approach is developed to find the constructal microscopic physics
of nanofluids for the optimal system performance. The approach is applied to design
nanofluids with any branching level of tree-shaped microstructures for cooling a
circular disc with uniform heat generation and central heat sink. The constructal
configuration and system thermal resistance have some elegant universal features for
both cases of specified aspect ratio of the periphery sectors and given the total number
of slabs in the periphery sectors.
The numerical simulation on the bubble formation in T-junction microchannels
shows: (i) the mixing enhancement inside liquid slugs between microfluidic bubbles,
(ii) the preference of T-junctions with small channel width ratio for either producing
smaller microfluidic bubbles at a faster speed or enhancing mixing within the liquid
phase, and (iii) the existence of a critical value of nondimensional gas pressure for
bubble generation. Such a precise understanding of two-phase flow in microchannels
is necessary and useful for delivering the promise of microfluidic technology in
producing high-quality and microstructure-controllable nanofluids.
Both blood and tissue macroscale temperatures satisfy the DPL bioheat equation
with an elegant solution structure. Effectiveness and features of the developed
solution structure theorems are demonstrated via examining bioheat transport in skin
tissues and during magnetic hyperthermia.published_or_final_version
Mechanical Engineering
Doctoral
Doctor of Philosophy
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Brooks, Evan Monticino Michael G. "Determining properties of synaptic structure in a neural network through spike train analysis." [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3702.
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Chen, Xiaohong, and 陳曉宏. "Theoretical and numerical studies of left-handed materials: transmission properties, beam propagationand localization." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43278474.
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Cullen, T. J. "Transmission properties of single-mode Y-junction and bend structures for integrated optics." Thesis, University of Glasgow, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356560.
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Gillies, Murray Fulton. "An investigation of the magnetic properties of spin-valves using transmission electron microscopy." Thesis, University of Glasgow, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294195.
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Singer, Joshua H. "Postnatal development of glycinergic synaptic transmission and biophysical properties of glycine receptor-channels /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/10535.
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Chan, Ho Ka. "Impact of synaptic properties, background activities and conductance effects on neural computation of correlated inputs." HKBU Institutional Repository, 2015. https://repository.hkbu.edu.hk/etd_oa/176.
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Neurons transmit information through spikes in neural network through synaptic couplings. Given the prevalence of correlation among neural spike trains experimentally observed in different brain areas, it is of interest to study how neurons compute correlated input. Yet how it depends on the synaptic properties and conductance kinetics in neuronal interaction is very little known. Through simulation of leaky integrate-and-fire (LIF) neurons, we have studied the effects of excitatory and inhibitory synaptic decay times, level of background activities and higher-order conductance effects on the output correlation of different time scales for neurons receiving correlated excitatory input, and provided important understanding on the mechanism of how these factors influence neural computation of such correlated input. We showed that when the conductance effects are totally ignored, increasing excitatory synaptic decay time jitters output spike time and shapes the output correlation of short to medium time scale, while the output correlation of very long time scale is determined by the membrane time constant. When conductance effects are considered, this is no longer the case as the effective membrane time constant becomes comparable to the excitatory decay time. We found that the ratio of long-term correlation to short-term correlation (synchrony) increases with excitatory synaptic decay time and decreases with the level of input activities due to the combined effects of jittered spike time, which can be predicted from the time window and magnitude of the effects of a single input spike on membrane potential, and burst firing. In particular, it is possible for neurons with small excitatory synaptic decay time in high conductance state to respond to correlated input by solely giving extra precisely timed synchronous spikes without exhibiting correlation of longer time scale. In addition, we found that inhibitory synaptic decay time shapes correlation by controlling the relative contribution of excitatory and inhibitory input to output firing. As a result, both output correlation and synchrony increase with it. These results are qualitatively true for a wide range of input correlation and synaptic efficacies. Finally, we showed that fluctuations of conductance and membrane potential reduce output correlation, which can be explained by the reduced prevalence of burst firing. These results suggest that spike initiation dynamics of neurons can be well characterized by their synaptic decay times and the level of input activities. These properties are therefore expected to influence neurons’ ability to code temporal information. These results also hint that correlation, in particular that of long time scale, would be lower if more realistic biophysical features like neural adaptations and network circuitry with feed-forward or recurrent inhibition are considered. It suggests that studies using single LIF neurons tend to overestimate output correlation and underestimate the ability of neurons in producing precisely timed output.
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Roth, Eric. "Nucleation and Heat Transfer in Liquid Nitrogen." PDXScholar, 1993. https://pdxscholar.library.pdx.edu/open_access_etds/1370.
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With the advent of the new" high Tc superconductors as well as the increasing use of cryo-cooled conventional electronics, liquid nitrogen will be one of the preferred cryogens used to cool these materials. Consequently, a more thorough understanding of the heat transfer characteristics of liquid nitrogen is required. In these investigations the transient heating characteristics of liquid nitrogen to states of nucleate and film boiling under different liquid flow conditions are examined. Using a metal hot wire/plate technique, it is verified that there is a premature transition to film boiling in the transient case at power levels as much as 30 percent lower than under steady state nucleate boiling conditions. It is also shown that the premature transition can be reduced or eliminated depending on the flow velocity The second part of this research analyses the nucleation (boiling) process from a dynamical systems point of view. By observing how the boiling system variables evolve and fluctuate over time, it is hoped that physical insight and predictive information can be gained. One goal is to discover some indicator or signature in the data that anticipates the transition from nucleate boiling to film/boiling. Some of the important variables that make up the boiling system are the temperature of the heater and the heat flux through the heater surface into the liquid nitrogen. Results, gained by plotting the system’s trajectory in the heat flux-temperature plane, are that on average the system follows a counterclockwise trajectory. A physical model is constructed that explains this behavior. Also, as the applied heater power approaches levels at which the transition to film is known to occur, the area per unit time swept out in the heat flux-temperature plane is seen to reach a maximum. This could be of practical interest as the threshold to film boiling can be anticipated and possibly prevented.
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McNett, Gabriel Dion. "Noise and signal transmission properties as agents of selection in the vibrational communication environment." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4677.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on February 25, 2008) Vita. Includes bibliographical references.
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Zhang, Rong. "Preparation, electroactive properties and field controlled microwave transmission of polythiophene based conducting polymer composites." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398610.
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Sims, Robert. "On the transmission properties of synapses made between granule cells and cerebellar Purkinje cells." Thesis, Aston University, 2003. http://publications.aston.ac.uk/11071/.
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In the cerebellar cortex, forms of both long-term depression (LTD) and long-term potentiation (LTP) can be observed at parallel fibre (PF) - Purkinje cell (PC) synapses. A presynaptic variant of cerebellar LTP can be evoked in PCs by raised frequency stimulation (RFS) of parallel fibre at 4-16Hz for 15s. This form of LTP is dependent on protein kinase A (PKA) and nitric oxide (NO), and can spread to distant synapses. Application of an extracellular NO scavenger, cPTIO, was found to prevent the spread of LTP to distant PF synapses in rat cerebellar slices. G-substrate may be an important mediator of the NO-dependent pathway for LTD. 8-16Hz RFS of PFs without a high concentration of calcium chelator in the postsynaptic cell evokes LTD. In cerebellar slices from wild-type and transgenic, G-substrate knockout mice, 8Hz RFS was applied to PFs, with a low concentration of postsynaptic calcium chelator. In PCs from wild-type mice, LTD predominated, whereas in those from transgenic mice LTP predominated. The ascending axon (AA) segment of the granule cell axon forms synapses with PCs as well as the PF segment. PPF and fluctuation analysis of EPSCs in rat PCs confirmed that the release sites of AA synapses have a greater probability of transmitter release than PF synapses. Furthermore, AA release sites have greater mean quantal amplitude than PF synapses, which is not due to a different type of postsynaptic receptor. AA synapses were found to have limited capacity to undergo the presynaptic variant of LTP, and were potentiated less than PF synapses in the presence of the PKA activator, forskolin. AA synapses also did not undergo the postsynaptic form of LTP, nor LTD induced by conjunctive stimulation of climbing fibre and PF.
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Chen, Xiaohong. "Theoretical and numerical studies of left-handed materials transmission properties, beam propagation and localization /." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43278474.
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Pandey, Amit Nath. "Fault detection of multivariable system using its directional properties." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3354.
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A novel algorithm for making the combination of outputs in the output zero direction of
the plant always equal to zero was formulated. Using this algorithm and the result of
MacFarlane and Karcanias, a fault detection scheme was proposed which utilizes the
directional property of the multivariable linear system. The fault detection scheme is
applicable to linear multivariable systems. Results were obtained for both continuous and
discrete linear multivariable systems. A quadruple tank system was used to illustrate the
results. The results were further verified by the steady state analysis of the plant.
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AMEEN, HASHIM FARHAN, Eid Jamal Al, and Abdulkhaliq Al-Salem. "Comparing of Real-Time Properties in Networks Based On IPv6 and IPv4." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-21535.
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Real time applications over IP network became widely used in different fields; social video conference, online educational lectures, industrial, military, and online robotic medical surgery. Online medical surgery over IP network has experienced rapid growth in the last few years primarily due to advances in technology (e.g., increased bandwidth; new cameras, monitors, and coder/decoders (CODECs)) and changes in the medical care environment (e.g., increased outpatient care, remote surgeries). The purpose of this study was to examine and analyze the impact of IP networks parameters; delay, jitter, throughput, and drop packet on the performance of real-time medical surgery videos sent across different IP networks; native IPv6, native IPv4, 6to4 and 6in4 tunneling transition mechanisms and compare the behavior of video packets over IP networks. The impact of each parameter over IP networks is examined by using different video codecs MPEG-1, MPEG-2, and MPEG-4. This study has been carried out with two main parts; theoretical and practical part, the theoretical part of this study focused on the calculations of various delays in IP networks such as transmission, processing, propagation, and queuing delays for video packet, while the practical part includes; examining of video codecs throughput over IP networks by using jperf tool and examining delay, jitter, and packet drops for different packet sizes by using IDT-G tool and how these parameters can affect quality of received video. The obtained theoretical and practical results were presented in different tables and plotted into different graphs to show the performance of real time video over IP networks. These results confirmed that video codecs MPEG-1, MPEG-2, and MPEG-4 were highly impacted by encapsulation and de-capsulation process except MPEG-4 codec, MPEG-4 was the least impacted by IPv4, IPv6, and IP transition mechanisms concerning throughput and wastage bandwidth. It also indicated that using IPv6-to-4 and IPv6-in-4 tunneling mechanisms caused more bandwidth wastage, high delay, jitter, and packet drop than IPv4 and IPv6.
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Li, Fang. "Microstructural properties of semiconductor nanostructures." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:396024e1-a646-40ca-8212-cad925b18311.
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Semiconductor nanostructures have attracted great interest owing to their unique physical properties and potential applications in nanoscale functional devices. The enhancement of the physical properties of semiconductor nanostructures and their performance in devices requires a deeper understanding of their fundamental microstructural properties. Thus this thesis is focused on the experimental and theoretical studies of the microstructural properties of two important semiconductor nanostructures: axial heterostructured silicon nanowires with varying doping and indium nitride colloidal nanoparticles. In this thesis, axial heterostructured silicon nanowires with varying doping were synthesized on an oxide-removed Si{111} substrate using a vapour-liquid-solid approach. Their fundamental microstructural properties, including the crystalline structure, wire growth direction and morphologies, were studied using various characterization techniques. It is found that a very small fraction of the silicon nanowires crystallize in a hexagonal (wurtzite) phase, which is thermodynamically unstable in bulk silicon under ambient conditions, while a large majority of the synthesized silicon nanowires exhibit the expected diamond cubic crystalline structure. About 75% of the diamond cubic silicon nanowires synthesized grow in a single <111> direction, while the rest contain growth-related kinks, where the nanowire switches to another direction during the growth. The ~109° silicon nanowire kinks are the most commonly observed, and the growth direction before and after such ~109° kink are both <111>. The sidewalls of silicon nanowires do not change abruptly at the ~109° kink, but exhibit an elbow-shaped structure. It is also found that the nanowire sidewalls exhibit periodic nanofaceting, which is strongly doping-dependent. The nanofaceting is found to occur during the enhanced sidewall growth that arises when the diborane dopant gas is introduced. A thermodynamic model predicting the dependence of nanofacet period on the wire diameter is developed. Another semiconductor nanostructure studied in this thesis is indium nitride colloidal nanoparticles, which were grown using a solution-phase chemical method. The formation of such indium nitride colloidal nanoparticles is confirmed by studying their compositions, crystalline structures and shape using various electron microscopy techniques. The size of the indium nitride colloidal nanoparticles was controlled by varying the time of solution-phase reactions. The most probable size of the colloidal nanoparticles increases and the size distribution broadens with the increase of reaction time. The crystalline structures of the indium nitride colloidal nanoparticles are found to be particle size dependent. The observed dependence of the band gap blueshift of the indium nitride colloidal nanoparticles on the reaction time (hence the particle size) is explained by the quantum-size effect.
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Thanawala, Monica Shishir. "Control of Neurotransmitter Release Properties by Presynaptic Calcium." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11529.
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Presynaptic terminals of neurons are optimized for neurotransmitter release, which is tightly controlled by presynaptic calcium. Here, we evaluate the role of calcium influx through voltage-gated calcium channels (VGCCs) in regulating the initial vesicular release probability (p) and the number of vesicles available for release by action potentials (effective RRP) at the calyx of Held synapse in mice. Two established methods of estimating effective RRP size and p reveal that both are calcium dependent. Reducing calcium influx by blocking R-type (VGCCs) or P/Q-type VGCCs also reduces EPSC amplitude via p and effective RRP size. Furthermore, activation of gamma-aminobutryic acid class B (GABAB) receptors, which reduces presynaptic calcium by regulating VGCCs without other significant effects on release, also reduces the effective RRP size and p. These findings suggest that the calcium dependence of RRP size may influence the manner in which certain neuromodulators affect neurotransmitter release.
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Esteky, Hossein. "Functional Properties and Organization of Primary Somatosensory Cortex." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc278197/.
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The physiological characteristics and organization of cat primary somatosensory cortex (SI) were studied in electrophysiological and anatomical experiments. In single cell recording experiments, quantitatively controlled mechanical stimuli were used to examine the responses of SI cortical neurons to the velocity component of skin or hair displacement. The firing frequency of most rapidly adapting neurons increased as stimulus velocity was increased. Rapidly adapting neurons were classified based on their response patterns to constant-velocity ramp stimuli. Neurons in these classes differed significantly in sensitivity to stimulus velocity and amplitude, adaptation rate, and spontaneous firing rate. The results suggest that frequency coding of stimulus displacement velocity could be performed by individual SI rapidly adapting neurons, and that the classes of rapidly adapting neurons may play different roles in sensation of tactile stimuli. Tract-tracing experiments were used to investigate the ipsilateral corticocortical connections of areas 3b and 2 in SI. Different patterns of connections were found for these areas: area 2 projects to areas 3b, 1, 3a, 5a, 4 and second somatosensory cortex (SII), and area 3b projects to areas 2, 1, 3a and SII. To further compare the organization of these areas, the thalamic input to the forepaw representation within each area was studied. The forepaw region in area 3b receives thalamic input exclusively from ventroposteriopr lateral nucleus (VPL), while area 2 receives input from VPL, medial division of the posterior complex (PoM), and lateral posterior nucleus (LP). These results suggest that area 2 lies at a higher position in the hierarchy of somatosensory information flow.
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Jalilikashtiban, Reza. "Structural and compositional properties of semiconductor quantum dots and nanocrystals." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/structural-and-compositional-properties-of-semiconductor-quantum-dots-and-nanocrystals(ceb22d89-7ed7-4c54-9d4c-612a9331404d).html.
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The research carried out here employed analytical and imaging transmission electron microscopy and scanning transmission electron microscopy to gain a good understanding of local structure and composition of semiconductor nanocrystals and quantum dots for electronics and optoelectronics applications. One of the world's most advanced analytical scanning transmission electron microscopes in the field, the Daresbury SuperSTEM, was used to scrutinise the structure and composition of the samples. Three nanostructure systems are investigated in this thesis: 1. Structures consisting of Ge-nanocrystals (NCs) in alumina. Here HRTEM suggests relaxed and twinned smaller NCs grown annealed at lower temperature compared to elongated non-faulty bigger NCs annealed at higher temperature. HRTEM also suggests a polycrystalline structure of the matrix. 2. With regards to the InAs/GaAs quantum dots (QD) the study aims in particular at elucidating QD formation by investigating samples grown with and without growth interrupt (GI). Diffraction contrast TEM shows formation of buried dots in the sample prepared with GI whereas for the sample without GI the immediate growth of GaAs after InAs inhibits diffusion and segregation of In adotoms, and no footprint of buried dots has been observed. HRTEM and HAADF show coherent QDs in the sample with GI and abrupt InAs/GaAs interfaces in the sample without GI. In executing energy electron loss spectroscopy (EELS) and geometric phase analysis (GPA) the distribution of In in InGaAs/GaAs QDs has been obtained in samples grown in the critical thickness regime for quantum dot formation. The highest In percentage achieved in the dots grown with a nominal fraction of 100% was ~70%. EELS shows variations in the In concentration within the QD structure and wetting layer 3. In the case of Er-doped Si-NCs in silica this research tries to provide an understanding of structure, composition and position of excess Si and Er in the silica matrix of materials prepared under different growth conditions and to correlate this information with the PL emission, all with the aim to find preparation routes for optimum optical efficiency for applications of this materials system in silicon photonics. High spatial correlation between Si-NCs, Er and O in the Er and Si co-implanted sample with strong indication of an Er-oxide/Si core-shell structure had been found. The lack of an Er-oxide plasmon indicates, however, that the shell structure and its interface with the SiNCs is highly defective and a likely cause for non-radiative recombination. The sample with similar excess Er and Si concentrations but prepared in a two-stage implantation and annealing process shows a 10 times improvement in the optical emission. Here no spatial correlation between Er and Si-NCs was found in core loss EELS. EELS and HAADF evidenced more highly, near-atomically dispersed Er in the matrix with no formation of a core-shell structure as compared to the co-implanted sample. No footprint of Er-silicide plasmon was observed by low loss valence band EELS investigation in the co-implanted sample.
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Hernandez, Francis Georg. "The development of a method for predicting the thermal performanceof partially buried walls." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/22364.
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Wandkowsky, Nancy [Verfasser], and G. [Akademischer Betreuer] Drexlin. "Study of background and transmission properties of the KATRIN spectrometers / Nancy Wandkowsky. Betreuer: G. Drexlin." Karlsruhe : KIT-Bibliothek, 2013. http://d-nb.info/1044956070/34.
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Phromphen, Phannaphat. "The permeation and moisture transmission properties of a thermosensitive membrane barrier for chemical protective clothing." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/12002/.
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The liquid chemical permeation properties and water vapour transmission properties of temperature sensitive poly(vinylidene fluoride) (PVDF) grafted N-isopropylacrylamide (NIPAAM) (NIPAAM-g-PVDF) copolymer membranes as a smart barrier layer in chemical protective clothing are studied in this research. Both modified thermally induced method and modified plasma induced method are employed to oxidise PVDF polymer for its copolymerisation with NIPAAM monomers. In the thermal induced method, NIPAAM-g-PVDF polymer materials are synthesised via the copolymerisation of ozone activated PVDF polymer with NIPAAM monomers below a lower critical solution temperature of NIPAAM (30°C). An effective supercritical carbon dioxide drying method is used as an alternative drying method to remove the solvent from the ozone activated PVDF polymer in conventionally copolymerisation is successfully applied and a new direct copolymerisation route by adding NIPAAM polymer into ozone activated PVDF in solutions without the drying process of the activated PVDF polymers. The NIPAAM-g-PVDF made by the new copolymerisation process is much simpler than the conventional method and the processing time needed is much shorter. In the oxygen plasma induced copolymerisation method, the porous PVDF membranes produced from the phase inversion method are treated oxygen plasma before they were copolymerised with NIPAAM monomer in N,N-dimethylformamide (DMF) solvent aqueous solution below the lower critical solution temperature of NIPAAM (30°C). The structural characteristics of heat-pressed NIPAAM-g-PVDF nanoporous membranes produced from the above two methods are investigated. The influence of the microstructure of the nanoporous copolymer membranes on both their water vapour transfer properties and dynamic permeation rate has been studied. The mechanisms of liquid/vapour permeation through the thermal sensitive copolymer nanoporous membranes are analysed and investigated. In this study, it is found that the breakthrough time and permeation rate of nanoporous NIPAAM-g-PVDF membranes are influenced by the proportion of NIPAAM components, the membrane thickness, the crystallinity and the porous structure of the NIPAAM-g-PVDF membranes. It is also found that the water vapour permeability of the heat-pressed NIPAAM-g-PVDF membranes at both 20°C and 40°C are influenced by the membrane thickness, the total pore volume and the porosity of the membranes. The water vapour permeability coefficient of the NIPAAM-g-PVDF nanoporous membranes is determined by both the proportion of thermal sensitive NIPAAM components and associated porous structure of the copolymer membranes.
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Cardoch, Sebastian. "Studying Atomic Vibrations by Transmission Electron Microscopy." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305370.
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We employ the empirical potential function Airebo to computationally model free-standing Carbon-12 graphene in a classical setting. Our objective is to measure the mean square displacement (MSD) of atoms in the system for different average temperatures and Carbon-13 isotope concentrations. From results of the MSD we aim to develop a technique that employs Transmission Electron Microscopy (TEM), using high-angle annular dark filed (HAADF) detection, to obtain atomic-resolution images. From the thermally diffusive images, produced by the vibrations of atoms, we intent to resolve isotopes types in graphene. For this, we establish a relationship between the full width half maximum (FWHM) of real-space intensity images and MSD for temperature and isotope concentration changes. For the case of changes in the temperature of the system, simulation results show a linear relationship between the MSD as a function of increased temperature in the system, with a slope of 7.858×10-6 Å2/K. We also note a power dependency for the MSD in units of [Å2] with respect to the FWHM in units of [Å] given by FWHM(MSD)=0.20MSD0.53+0.67. For the case of increasing isotope concentration, no statistically significant changes to the MSD of 12C and 13C are noted for graphene systems with 2,000 atoms or more. We note that for the experimental replication of results, noticeable differences in the MSD for systems with approximately 320,000 atoms must be observable. For this, we conclude that isotopes in free-standing graphene cannot be distinguished using TEM.
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Acosta, Guillermo Antonio. "Scandium Oxide Thin Films and Their Optical Properties in the Extreme Ultraviolet." BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1285.
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This study reports on the physical and optical characterization of scandium oxide thin films. Thin films of scandium oxide, 20-40 nm thick, were deposited on silicon wafers, quartz slides, and silicon photodiodes by reactively sputtering scandium in an oxygen environment. These samples were characterized using ellipsometry, high-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis. A 28.46 nm thick scandium oxide thin film was measured in the Extreme Ultraviolet (EUV) from 2.7 to 50 nm (459.3 to 24.8 eV) using synchrotron radiation at the Advanced Light Source Beamline 6.3.2 at the Lawrence Berkeley National Laboratory. In these measurements, a new method for data collection was used, in which the reflection and transmission data were collected simultaneously. Analysis of the EUV reflection and transmission data was performed using a front-side reflection, matrix-multiplication technique, which is novel among EUV analytical practice. During data analysis, a new weighting scheme was used, named "adaptive weighting". This analysis provides the first experimentally determined optical constants n and k for scandium oxide thin films from 4.5-30 nm. Also, the positions of the L2 and L3 electronic transitions of scandium oxide have been measured, at 3.069 and 3.101 nm (404.0 and 399.9 eV), respectively, while the measurements near the M transition suggest it to be at approximately 31.5 nm (39.4 eV). Comparing the electronic transition positions of scandium oxide to those of scandium show that the oxidation of scandium shifts the positions to lower energies. For L2 the shift is about 1.8 eV, for L3 the shift is about 1.4 eV, and for M the shift is about 1.9 eV. The binding energies of scandium oxide are greater than those of scandium, as is expected for an oxide compared to its parent metal. This trend in the shift of the transition positions is unexpected, and warrants further investigation.
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Rosenthal, Tobias [Verfasser], and Oliver [Akademischer Betreuer] Oeckler. "Transmission electron microscopy and properties of thermoelectric chalcogenides and luminescent oxonitridosilicates / Tobias Rosenthal. Betreuer: Oliver Oeckler." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2014. http://d-nb.info/1060632292/34.
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Iglesias, Miguel Olmedo. "Investigation of the chirp properties of DFB-EAM’s for high speed baseband and RoF transmission links." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-100735.
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The ever increasing bandwidth demands driven by an explosion in the mobile device market calls for more and more optical and wireless convergence due to the ability of optical communication systems to transport larger amounts of information to longer distances. Optical modulators are in charge of performing the electrical-to-optical domain conversion, which place them as one of the critical components in optical communication systems. One of the fastest optical modulators is the so called Electro-Absorption Modulator (EAM), which oers very attractive advantages such as the integration with Distributed Feedback (DFB) lasers and its capability of modifying the chirp properties (represented as the parameter) via reverse bias voltage. While a lot of eort has been put in trying to reduce the α parameter as close to 0 as possible, not much work has addressed the performance of integrated Distributed Feedback laser - Electro-Absorption Modulators (DFB-EAMs) handling advanced modulation formats in high speed baseband and Radio over Fiber (RoF) transmission links. This thesis focus on how the chirp aects the transmission of such schemes relevant for optical interconnects and metro-access networks by performing a series of simulations and experiments. The experimental results indicate promising performance including a Bit Error Rate (BER) of 10-4 after 92 km of Standard Single Mode Fiber (SSMF) real time transmission of a 12.5 Gbps On OKeying - Non Return to Zero (OOK-NRZ) signal in real time and no Digital Signal Processing (DSP) and a BER of 10-3 with a 17.4 Gbps four level Pulse Amplitude Modulation (PAM) after 44 km SSMF.
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Bishop, Matthew T. "Role of PRNP codon 129 genotype in defining strain transmission properties of human transmissible spongiform encephalopathy." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4236.
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The human prion protein (PrP) gene (PRNP) codon 129 (M/V) polymorphism is a susceptibility factor for variant Creutzfeldt-Jakob Disease (vCJD) and a major determinant of clinico-pathological phenotype in sporadic CJD. The role of codon 129 in defining susceptibility and strain transmission properties has been investigated in three lines of transgenic mice that express human PrP. The human PRNP gene has directly replaced the murine version, by gene targeting, and variation at codon 129 has given the three genotype lines (HuMM, HuMV, and HuVV). The genetics of these three mouse lines are otherwise identical, and therefore differences in transmission properties can be directly attributable to the codon 129 genotype. vCJD inoculation has shown that all three codon 129 genotype mice are susceptible with a ranking of transmission efficiency of HuMM>HuMV>HuVV. HuMM mice develop the most widespread neuropathology with features similar to human vCJD. Subclinical infection was noted in each mouse line. These data suggest that the vCJD strain is transmissible to humans of each of the three codon 129 genotypes, implying that non-MM cases of human infection with bovine spongiform encephalopathy (BSE) may exist but with long subclinical incubation periods. Inoculation of material from blood transfusion associated vCJD showed no change in transmission properties suggesting that the threat of a future epidemic of human-to-human vCJD infection has not been increased by adaptation of the vCJD strain. However the route of infection, for example via blood transfusion or surgery, may be more efficient that the original oral route of BSE infection. sCJD is classified into six subgroups according to clinico-pathological features, and defined by codon 129 genotype and electrophoretic mobility type (1 or 2) of disease associated PrPSc (MM1, MM2, MV1, MV2, VV1, VV2). Typical cases from each subgroup have shown specific transmission properties suggesting that the subgrouping is defining separate disease strains. The commonest subgroup (MM1) was the most transmissible and the HuVV mouse line the most susceptible host. These data outline the transmission risk from all sCJD types to recipients of each codon 129 genotype should an infection event occur, and show the significant role of recipient codon 129 genotype in defining the clinical or subclinical state and the success or failure of transmission. This is important for determining individual risk following known exposure, and for modelling the potential of iatrogenic infection from sCJD patients.
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Schneider, Johannes Matthias Peter [Verfasser]. "Assessment of cortical bone properties at the tibia using axial transmission ultrasound / Johannes Matthias Peter Schneider." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1202042228/34.
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Al-Aridhee, Tahseen. "Numerical study of optical properties of single and periodic nanostructures : from nanoantennas to enhanced transmission metamaterials." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2004/document.
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L ’intérêt des nano-particules pour le domaine de l ’optique visible a été suscité lors du premier rapport rédigé par Faraday en 1857 et qui a initié les bases de la production de nanoparticules métalliques en vue de leur propriété optiques inattendues (coloration des solutions). Plus récemment, le contrôle et le guidage de la lumière basés sur l’excitation de résonance plasmon dans les nanostructures a permis beaucoup d’applications liées à la vie quotidienne et impliquant la lumière. La résonance plasmonique de structures métalliques estun phénomène essentiel qui conduit à des propriétés optiques uniques à travers l’interaction de la lumière avecles électrons libres du métal. L’excitation de la résonance plasmon localisé (LSPR) permet d’exalter localement l’énergie électromagnétique comme dans le cas des nano-antennes mais aussi d’acheminer la lumière à travers des canaux de dimensions sub-l sur de grandes distances distances grâce à l’excitation du Plasmonde Surface Propagatif (PSP). Au cours de cette thèse, nous avons étendu un algorithme existant afin de calculer la réponse optique (sections efficaces de diffusion et d’absorption) de NPs ayant une forme géométrie quelconque. Ce type de NP anisotrope (vis-à-vis de la polarisation incidente) peut présenter à la résonance plasmonique une section efficace de diffusion 25 fois supérieure à celle géométrique. De plus, une étude systématique importante a été effectuée afin d’optimiser la géométrie de tels Nps.En ce qui concerne la PSP qui est impliqué dans la transmission exaltée à travers les matrices d’ouvertures annulaires AAA, nous avons entrepris une étude systématique des propriétés de l’excitation du mode particul particulier sans coupure de ces nano - guides. Il s’agit du mode Transverse Electrique et Magnétique (TEM). Une étude numérique complète est alors effectuée pour correctement concevoir la structure avant qu’elle ne soit expérimentalement fabriquée et caractérisée. Pour palier certaines contraintes expérimentale, une structure inclinée est proposée et étudiée dans le cas d’un métal parfaitement conducteur. Nous avons démontrée numériquement et analytiquement certaines propriétés intrinsèques de la structure montrant un coefficient de d’au moins 50% d’un faisceau incident non polarisé indépendamment des conditions d’éclairage (polarisation,angle et plan d’incidence). Lorsque le mode TEM est excité, le flux laminaire de l’énergie à travers la structure présente une déviation géante sur de très petites distances inférieures à la longueur d’onde. Les résultats présentés dans cette thèse pourraient être considérés comme une contribution importante à la compréhension du phénomène de transmission exaltée basé sur l’excitation de ce type de mode guidéThe release of the rst report by Faraday in 1857 set the foundation of the production of metal nanoparticlesand their unexpected optical properties (coloring). More recently, controlling and guiding light via plasmonicresonance in nanostructures enable a lot of applications affecting everyday life that involves light. Plasmonresonance of metallic structures is a key phenomenon that allows unique optical properties through the interactionof light with the free electrons of the metal. The excitation of Localized Surface Plasmon Resonance(LSPR) leads to turn-on large local enhancements of electromagnetic energy as within antennas or to routelight as waveguide to desired region with high transmission through the excitation of Propagating SurfacePlasmon (PSP). During this thesis, we have developed an existing algorithm in order to calculate the opticalresponse of NPs of any shape. We have especially determined the localized energy enhancement factor interm of optical response of nano-antenna. This anisotropic (polarization dependent) NPs type can feature, atplasmon resonance, scattering efciency factor higher than 25. Moreover, an important systematic study hasbeen performed in order to optimize design of such NPs.Concerning the PSP that are involved in the enhanced transmission through Annular Aperture Arrays (AAAs),we systematically study the properties of the excitation of the peculiar Transverse ElectroMagnetic (TEM) guidedmode inside such nano-apertures. A complete numerical study is performed to correctly design the structurebefore it is experimentally characterized. For reasons associated to fabrication constraints and efciency,a slanted AAA made in perfectly conducting metal is proposed and studied. We numerically and analyticallydemonstrate some intrinsic properties of the structure showing a transmission coefcient of at least 50%ofan un-polarized incident beam independently of the illumination configuration (polarization, angle, and planeof incidence). At the TEM peak transmission, the laminar flow of the energy through the structure can exhibitgiant deviation over very small distances ( ). The results presented in this thesis could be considered as animportant contribution to the understanding of the enhanced transmission phenomenon based on the excitationof guided modes
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Beemat, Jaspreet S. "Processing and Properties of Hybrid Silane-Epoxy Nanocomposite Coatings." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1352992819.
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