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1
Tas, Murat. "Dielectric Formulation Of The One Dimensional Electron Gas." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604981/index.pdf.
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The charge and spin density correlations in a one dimensional electron gas (1DEG) confined in a semiconductor quantum wire structure at zero temperature are studied. The dielectric formulation of the many--body problem is employed and the longitudinal dielectric function, local-field correction, static structure factor, pair correlation function, ground state energy, compressibility, spin-dependent effective interaction potentials, paramagnon dispersion and static spin response function of the 1DEG are computed within the self-consistent field approximations of Singwi et al., known as the STLS and SSTL. The results are compared with those of other groups,
and those obtained for two-dimensional electron gas systems whenever it is possible.
It is observed that the SSTL satisfies the compressibility sum rule better than the STLS. Calculating the ground state energy of the 1DEG in unpolarized and fully polarized states, it is shown that both STLS and SSTL predict a Bloch transition for 1DEG systems at low electron densities.
Finally, the coupled plasmon-phonon modes in semiconductor quantum wires are calculated within the Fermi and Luttinger liquid theories. The coupling of electrons to bulk longitudinal optical phonons without dispersion and to acoustic phonons via deformation potential with a linear dispersion are considered. Using the dielectric formalism, a unified picture of the collective coupled plasmon-phonon modes is presented. Considerable differences between the predictions of the Fermi and Luttinger liquid approaches at large wave vector values,
which may be observed experimentally, are found.
2
Rodriguez, Carlos G. "One-Dimensional, Finite-Rate Model for Gas-Turbine Combustors." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30672.
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An unsteady, finite-rate, one-dimensional model has been developed for the analysis for gas-turbine combustors. The basis of the model is the one-dimensional, integral form of the conservation equations for multi-species, non-equilibrium, reacting mixtures. Special procedures were devised for the flow-division of the inlet flow into primary- and annular-flows, for both straight- and reverse-flow combustors. This allows the model to handle complete combustor configurations, which at present are beyond the reach of more sophisticated CFD tools. The model was validated with a steady-state analytical solution for a basic problem, and with steady-state results from a production code applied to a production combustor. Additional calculations show the ability of the code to predict blow-out due to rich and lean mixtures, and to predict the response of a combustor to perturbations in operating and boundary conditions.<br>Ph. D.
3
Caley, Thomas. "Numerical Modeling of Gas Turbine Combustor Utilizing One-Dimensional Acoustics." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491562189178949.
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Gudyma, Andrii. "Non-equilibrium dynamics of a trapped one-dimensional Bose gas." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS064/document.
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Une étude des modes d'oscillations d'une gaz de Bose unidimensionnel dans la piège est présentée. Les oscillations sont initiées par une changement instantanée de la fréquence de piégeage. Dans la thèse il est considéré d'un gaz de Bose quantique 1D dans un piège parabolique à la température nulle, et il est expliqué, analytiquement et numériquement, comment la fréquence d'oscillation dépend du nombre de particules, leur interaction répulsive, et les paramètres de piège. Nous sommes concentres sur la description spectrale, en utilisant les règles de somme. La fréquence d'oscillation est identifiée comme la différence d'énergie entre l'état fondamental et un état excité donne. L'existence de trois régimes est démontrée, à savoir le régime de Tonks, le régime de Thomas-Fermi et le régime de Gauss. La transition entre les régime de Tonks et de Thomas-Fermi est décrite dans l'approximation de la densité locale (LDA). Pour la transition entre le régime de Thomas-Fermi et le régime de Gauss l'approximation de Hartree est utilisée. Dans les deux cas, nous avons calculé les paramètres pour quelles les transitions se produisent. Les simulations extensif de Monte Carlo de diffusion pour un gaz contenant jusqu'à N = 25 particules ont été effectuées. Lorsque le nombre de particules augmente, les prédictions des simulations convergent vers celles d'Hartree et LDA dans ces régimes. Cela rend les résultats des modes d'oscillation applicables pour des valeurs arbitraires du nombre de particule et de l'interaction. L'analyse est complétée par les résultats perturbatifs dans les cas limites avec N finis. La théorie prédit le comportement réentrant de la fréquence de mode d'oscillation lors de la transition du régime de Tonks au régime de Gauss et explique bien les données de l'expérience récente du groupe d'Innsbruck<br>A study of breathing oscillations of a one-dimensional trapped interacting Bose gas is presented. Oscillations are initiated by an instantaneous change of the trapping frequency. In the thesis a 1D quantum Bose gas in a parabolic trap at zero temperature is considered, and it is explained, analytically and numerically, how the oscillation frequency depends on the number of particles, their repulsive interaction, and the trap parameters. We have focused on the many-body spectral description, using the sum rules approximation. The oscillation frequency is identified as the energy difference between the ground state and a particular excited state. The existence of three regimes is demonstrated, namely the Tonks regime, the Thomas-Fermi regime and the Gaussian regime. The transition from the Tonks to the Thomas-Fermi regime is described in the terms of the local density approximation (LDA). For the description of the transition from the Thomas-Fermi to the Gaussian regime the Hartree approximation is used. In both cases the parameters where the transitions happen are found. The extensive diffusion Monte Carlo simulations for a gas containing up to N = 25 particles is performed. As the number of particles increases, predictions from the simulations converge to the ones from the Hartree and LDA in the corresponding regimes. This makes the results for the breathing mode frequency applicable for arbitrary values of the particle number and interaction. The analysis is completed with the finite N perturbative results in the limiting cases. The theory predicts the reentrant behavior of the breathing mode frequency when moving from the Tonks to the Gaussian regime and fully explains the recent experiment of the Innsbruck group
5
Latt, Kyaw Zin. "Interactions of Two Dimensional Surface State Electron Gas with Zero, One and Two Dimensional Structures." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1383242271.
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Parthangal, Prahalad Madhavan. "Synthesis and integration of one-dimensional nanostructures for chemical gas sensing applications." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6881.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
7
Tang, Zifan. "One-dimensional mechanistic modelling of gas-liquid two phase flow in pipes." Thesis, Imperial College London, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284815.
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Mukherjee, Tamal. "One Dimensional Air System Modeling of Advanced Technology Compressed Natural Gas Engines." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397776678.
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De, Rosi Giulia. "Collective oscillations of a trapped atomic gas in low dimensions and thermodynamics of one-dimensional Bose gas." Doctoral thesis, Università degli studi di Trento, 2017. https://hdl.handle.net/11572/368019.
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Ultracold atoms are exceptional tools to explore the physics of quantum matter. In fact, the high degree of tunability of ultracold Bose and Fermi gases makes them ideal systems for quantum simulation and for investigating macroscopic manifestations of quantum effects, such as superfluidity.
In ultracold gas research, a central role is played by collective oscillations. They can be used to study different dynamical regimes, such as superfluid, collisional, or collisionless limits or to test the equation of state of the system. In this thesis, we present a unified description of collective oscillations in low dimensions covering both Bose and Fermi statistics, different trap geometries and zero as well as finite temperature, based on the formalism of hydrodynamics and sum rules. We discuss the different behaviour exhibited by the second excited breathing mode in
the collisional regime at low temperature and in the collisionless limit at high temperature in a 1D trapped Bose gas with repulsive contact interaction. We show how this mode exhibits a single-valued excitation spectrum in the collisional regime and two different frequencies in the collisionless limit. Our predictions could be important for future research related to the thermalization and damping phenomena in this low-dimensional system. We show that 1D uniform Bose gases exhibit a non-monotonic temperature dependence of the chemical potential characterized by an increasing-with-temperature behaviour at low temperature. This is due to the thermal excitation of phonons and reveals an interesting analogy with the behaviour of superfluids.
Finally, we investigate a gas with a finite number N
of atoms in a ring geometry at T = 0. We discuss explicitly the deviations of the thermodynamic behaviour in the ring
from the one in the large N limit.
10
De, Rosi Giulia. "Collective oscillations of a trapped atomic gas in low dimensions and thermodynamics of one-dimensional Bose gas." Doctoral thesis, University of Trento, 2017. http://eprints-phd.biblio.unitn.it/2066/1/PhD_DeRosi.pdf.
Full textAbstract:
Ultracold atoms are exceptional tools to explore the physics of quantum matter. In fact, the high degree of tunability of ultracold Bose and Fermi gases makes them ideal systems for quantum simulation and for investigating macroscopic manifestations of quantum effects, such as superfluidity.
In ultracold gas research, a central role is played by collective oscillations. They can be used to study different dynamical regimes, such as superfluid, collisional, or collisionless limits or to test the equation of state of the system. In this thesis, we present a unified description of collective oscillations in low dimensions covering both Bose and Fermi statistics, different trap geometries and zero as well as finite temperature, based on the formalism of hydrodynamics and sum rules. We discuss the different behaviour exhibited by the second excited breathing mode in
the collisional regime at low temperature and in the collisionless limit at high temperature in a 1D trapped Bose gas with repulsive contact interaction. We show how this mode exhibits a single-valued excitation spectrum in the collisional regime and two different frequencies in the collisionless limit. Our predictions could be important for future research related to the thermalization and damping phenomena in this low-dimensional system. We show that 1D uniform Bose gases exhibit a non-monotonic temperature dependence of the chemical potential characterized by an increasing-with-temperature behaviour at low temperature. This is due to the thermal excitation of phonons and reveals an interesting analogy with the behaviour of superfluids.
Finally, we investigate a gas with a finite number N
of atoms in a ring geometry at T = 0. We discuss explicitly the deviations of the thermodynamic behaviour in the ring
from the one in the large N limit.
11
Lilly, Jonathan Patrick. "One-dimensional computer modeling of electrical conductivity through methane and synthesis gas flames." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4898.
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Thesis (M.S.)--West Virginia University, 2006.<br>Title from document title page. Document formatted into pages; contains xvi, 291 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 289-291).
12
Ha, Meesoon. "Scaling and phase transitions in one-dimensional nonequilibrium driven systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9758.
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Cheng, Chi-Yuan. "Gas adsorption, diffusion, and exchange in one-dimensional nanotube systems by hyperpolarized Xe-129 NMR." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0022786.
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Kirkpatrick, Samuel John. "An evaluation of one-dimensional simulation techniques for predicting unsteady gas flow in engine ducting." Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.482057.
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Baradaran, Amir R. "Development and Implementation of a Preconditioner for a Five-Moment One-Dimensional Moment Closure." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32225.
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This study is concerned with the development and implementation of a preconditioner for a set of hyperbolic partial differential equations resulting from a new 5-moment closure for the prediction of gas flows both in and out of local equilibrium. This new 5-moment closure offers a robust and efficient system of first-order hyperbolic partial differential equations that has proven to provide an accurate treatment of one-dimensional gases, both in and for significant departures from local thermodynamic equilibrium. However, numerical computations using this model have proven to be difficult as a result of a singularity in the closing flux of the system. This also causes infinitely large wavespeeds in the system. The main goal of this work is to mitigate these numerical issues. Since the solution of a hyperbolic system is characterized by the waves of the system, one could suggest to scale these wavespeeds to remove the arbitrarily large speeds without altering the solution of the system. To accomplish this, this work starts with a detailed study of the behaviour of the system’s wavespeeds, given by the eigenvalues of the flux Jacobian of the system. Since, it is not possible to solve for these eigenvalues explicitly, it is suggested to approximate them by interpolation between the few states at which these waves can be solved for explicitly. With an estimate for the wavespeeds, the nature of the singularity in the system can be analyzed mathematically. The results of this mathematical analysis are used to develop a preconditioner matrix to remove the singularity from the model. To implement
the proposed preconditioned model numerically, a centred-difference scheme with artificial dissipation is proposed. A dual-time-stepping strategy is developed and implemented with implicit Euler time marching for both physical and pseudo time iteration. This dual-time treatment allows the preconditioned system to remain applicable to time-accurate problems and is found to greatly increase the robustness of the solution of the steady-state problems. Solutions to several canonical problems for both continuum and non-equilibrium flow are computed and comparisons are made to classical models.
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Abbaspour, Mohammad. "Simulation and optimization of non-isothermal, one-dimensional single/two-phase flow in natural gas pipeline /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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McMackin, Martin. "A one-dimensional model of the unsteady gas dynamics and surface relations within an automotive catalyst." Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486531.
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The motivation behind this investigation was the need to further the understanding of the gas dynamic behaviour of automotive catalysts under pulsating flow conditions, with a view to improving the ease and accuracy of simulating engine-catalyst systems. A VIRTUAL 4-STROKE model representative of a current-generation engine-catalyst system was developed and simulated over a range of operating conditions. The capability . of this model to simulate a current-generation engine-catalyst system model was evaluated against measured results obtained during dynamometer experiments. A separate simulation program based on the catalyst model incorporated in VIRTUAL 4STROKE was also developed so that tests in which catalyst substrates were subjected to individual blowdown pulses could be simulated, thus allowing the fundamental elements of this catalyst model to be assessed in relative isolation from the complex superposition effects encountered on a running engine. Results from this simulation program was compared against measured results obtained during experiments on the QUB Single Shot Rig. In this way, the merits and demerits of the catalyst element of the VIRTUAL 4STROKE model were assessed at a fundamental level, as well as in the context of a running engine. While measured-simulated correlations were good, some possible improvements to both the model and the experimental procedure were identified.
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Gabrielyan, Nare. "Low temperature fabrication of one-dimensional nanostructures and their potential application in gas sensors and biosensors." Thesis, De Montfort University, 2013. http://hdl.handle.net/2086/9607.
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Nanomaterials are the heart of nanoscience and nanotechnology. Research into nanostructures has been vastly expanding worldwide and their application spreading into numerous branches of science and technology. The incorporation of these materials in commercial products is revolutionising the current technological market. Nanomaterials have gained such enormous universal attention due to their unusual properties, arising from their size in comparison to their bulk counterparts. These nanosized structures have found applications in major devices currently under development including fuel cells, computer chips, memory devices, solar cells and sensors. Due to their aforementioned importance nanostructures of various materials and structures are being actively produced and investigated by numerous research groups around the world. In order to meet the market needs the commercialisation of nanomaterials requires nanomaterial fabrication mechanisms that will employ cheap, easy and low temperature fabrication methods combined with environmentally friendly technologies. This thesis investigates low temperature growth of various one-dimensional nanostructures for their potential application in chemical sensors. It proposes and demonstrates novel materials that can be applied as catalysts for nanomaterial growth. In the present work, zinc oxide (ZnO) and silicon (Si) based nanostructures have been fabricated using low temperature growth methods including hydrothermal growth for ZnO nanowires and plasma-enhanced chemical vapour deposition (PECVD) technique for Si nanostructures. The structural, optical and electrical properties of these materials have been investigated using various characterisation techniques. After optimising the growth of these nanostructures, gas and biosensors have been fabricated based on Si and ZnO nanostructures respectively in order to demonstrate their potential in chemical sensors. For the first time, in this thesis, a new group of materials have been investigated for the catalytic growth of Si nanostructures. Interesting growth observations have been made and theory of the growth mechanism proposed. The lowest growth temperature in the published literature is also demonstrated for the fabrication of Si nanowires via the PECVD technique. Systematic studies were carried out in order to optimise the growth conditions of ZnO and Si nanostructures for the production of uniformly shaped nanostructures with consistent distribution across the substrate. v The surface structure and distribution of the variously shaped nanostructures has been analysed via scanning electron microscopy. In addition, the crystallinity of these materials has been investigating using Raman and X-ray diffraction spectroscopies and transmission electron microscopy. In addition to the fabrication of these one-dimensional nanomaterials, their potential application in the chemical sensors has been tested via production of a glucose biosensor and an isopropyl alcohol vapour gas sensor based on ZnO and Si nanostructures respectively. The operation of the devices as sensors has been demonstrated and the mechanisms explored.
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Gallucci, Donatello. "Ab initio modelling of quasi-one-dimensional Bose gas experiments via the stochastic Gross-Pitaevskii equation." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/1858.
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In this thesis we use the stochastic Gross-Pitaevskii equation (SGPE), a finite temperature model for weakly interacting ultracold Bose gases which fully incorporates density and phase fluctuations, to demonstrate ab initio quantitative agreementwith a number of quasi-one-dimensional experiments. To achieve this, we propose and numerically solve a quasi-one-dimensional form of the SGPE, supported by a self-consistent treatment of radially-excited thermal modes. The quasi-one-dimensional stochastic Gross-Pitaevskii equation provides an accurate finite temperature description of the dynamical equilibrium of the lowenergy axial modes of a Bose gas, assumed to be highly populated and thus treated within the ‘classical field’ approximation. This treatment allows to selfconsistently account for transverse, quasi-one-dimensional effects, which makes it a valid model in the regime where the chemical potential, μ, is approximately equal to a few times the transverse excitation energy, ~!?. In the regime where the thermal energy, kBT, is also comparable to or larger than ~!?, the transverse excited states play an increasingly important role, and are treated here as onedimensional independent Bose gases at static equilibrium. Firstly, we demonstrate that this is an excellentmodel for ab initio investigation of equilibrium properties, such as density profiles and density fluctuations. This is shown by accurately reproducing the in situ density profiles recently obtained in the experiments of Trebbia et al. [Phys. Rev. Lett. 97, 250403 (2006)] and van Amerongen et al. [Phys. Rev. Lett. 100, 090402 (2008)], and the density fluctuation data reported by Armijo et al. [Phys. Rev. Lett. 105, 230402 (2010)]. Moreover, we perform an ab initio analysis of the temperature dependence of the phase coherence of finite temperature, quasi-one-dimensional Bose gases measured in the experiments of Richard et al. [Phys. Rev. Lett. 91, 010405 (2003)] and Hugbart et al. [Eur. Phys. J. D 35, 155 (2005)]. We find very good agreement across the entire observed temperature range in both experiments, and improve upon previous theoretical modelling of the latter.
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Kratschun, Filipp, Jens Köhne, Peter Kloft, Heiko Baum, and Katharina Schmitz. "One dimensional unsteady model of a hydropneumatic piston accumulator based on finite volume method." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71089.
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Hydraulic piston accumulators play a major role especially within the field of stationary hydraulics. The calculation of the amount of hydraulic energy which can be stored in such an accumulator is crucial when it comes to a precise system design. The knowledge of the temperature and pressure within the accumulator is required in order to calculate the amount of energy to be stored. The state of the art solution to estimate the state of change of such an accumulator is the implementation of a costly measurement system within the accumulator which tracks the position of the piston. The goal of this paper is to develop and to analyse a time efficient simulation approach for the gaseous phase within a piston accumulator depending on the accumulator’s load cycle. Temperature, pressure, density and velocity profiles inside of the gaseous phase are calculated transiently in order to achieve that goal. The simulation model is derived in one dimensional environment to save computational effort. Having derived a valid model of the gaseous phase it will be possible in future works to replace the expensive position measurement system by pressure and temperature transducers and then use the model to calculate the position of the piston and therefore estimate the state of change.
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Priščák, Juraj. "Charakterizace senzitivních nanomateriálů pro MOX senzory plynů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442521.
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This thesis deals with one-dimensional (1D) and two-dimensional nanomaterials (2D) in terms of their utilization for new types of gas sensors. Thesis focuses on study of sensing elements for gas sensors based on semiconductor metal oxide materials (MOX) and their manufacturing technology. The objective of the thesis is the design and implementation of a sensing elements formed by selected nanomaterials based on the structure of interdigital electrodes. The result of the practical part of the thesis is the characterization and comparison of materials in terms of their detection parameters in the presence of selected test gases. The first part of thesis hierarchically defines chemoresistive gas sensor, characterizes and explains its operation principle. Second part studies 1D and 2D nanomaterials of sensing elements for MOX chemoresistive gas sensors, contains a research of their properties and describes their methods of manufacturing and implementation. The last part deals with the implementation of the sensitive layer of the sensor with selected nanomaterials, characterizes and compares their detection properties.
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Isaksson, Frida. "Pressure loss characterization for cooling and secondary air system components in gas turbines." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-64528.
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There is a constant struggle to increase the efficiency in gas turbines, where one method is to have a higher inlet temperature to the turbine. Often, this results in temperatures higher than the critical temperature of the materials, which makes cooling of the components an important part of the turbine. The cooling air is tapped from the compressor, and has hence required work while being compressed, but since it is removed from the thermodynamic cycle it will not provide any work in the turbine stages. Therefore, it is important to understand the losses in the cooling system to be able to use the smallest amount of cooling air possible, while still cool sufficiently to not decrease the turbine’s lifetime. The pressure losses in the cooling and secondary air systems are due to either friction or minor losses; contractions, expansions and bends. The losses can be described by a discharge coefficient, ; a rate of how close the actual mass flow is to the ideal mass flow, or a pressure loss coefficient, ; a rate of the pressure drop. In the cooling and secondary air systems there are orifices and cooling geometries. These can have different geometrical properties depending on application, and thereby have different heat transfer performances and causing a higher or lower pressure drop. At Siemens Industrial Turbomachinery AB, SIT AB, a one-dimensional in-house program named C3D is used for thermal calculations and calculations of flow properties of internal cooling flow networks. The program uses hydraulic networks consisting of nodes and branches to simulate the flow inside the components. Correlations used for describing pressure losses have been collected and divided depending on their valid ranges, with the aim to make pressure loss calculations easier. A MATLAB code have been developed, which, depending on input parameters, separates the correlations and returns a plot with the correlations that can be used. In order to make the code as useful as possible, a few assumptions were made; curve fitting of correlations which were only available as plots and interpolation to get larger valid ranges for some cases. These assumptions will influence the results, but the code will still be able to give an indication of which correlation to use, and hence, the objective is fulfilled. Simulations in one dimension are commonly used, since it is less time consuming than three-dimensional modelling. Therefore, with focus on the pressure losses, a one-dimensional model of a blade in the in-house program C3D has been evaluated using a three-dimensional model in the CFD program Ansys CFX. Also, two new models were created in C3D; both with geometrical properties and pressure loss coefficients adjusted to the CFX model, but the first model is using the same hydraulic network as in the evaluated, reference, model while the second is using a new network, built according to the streamlines in CFX. The resulting mass flows in the C3D models were compared to the mass flows in the CFX model, which ended in the conclusion that it is hard for the one-dimensional models to understand the complex, three-dimensional flow situations, even when adjusting them to the CFX model. Anyhow, the adjustments made the model somewhat closer to the three-dimensional case, and hence CFX should be used in an earlier stage when developing C3D models.
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Young, Alexander L., and Alexander L. Young. "Three Essays on Complex Systems: Self-Sorting in a One-Dimensional Gas, Collective Motion in a Two-Dimensional Ensemble of Disks, and Environment-Driven Seasonality of Mosquito Abundance." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/624567.
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Complex systems offer broad, unique research challenges due to their inability to be understood through a classic reductionist perspective, as they exhibit emergent phenomena that arise through the interactions of their components. In this thesis, we briefly review some characteristics of complex systems and the interplay of mathematical and computational methods to study them. We then discuss these approaches, how they are implemented, and how they support one another in three settings. First, we present a study that connects weather data to seasonal population-abundance of mosquitoes, using a microscopic model. Secondly, we consider the collective motions that arise in ensembles of disks interacting through non-elastic collisions and investigate how such behaviors affect macroscopic transport properties. Finally, we consider a 'self-sorting' one-dimensional collection of point-particles. In all of these cases, agent-based models and simulations are used to guide analysis, and in the final example, we explain how the simulations led to new theorems. Articles and molecular dynamics computer codes are provided as appendices.
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Händestam, Jacob, and Eric Jacobson. "Investigation and Validation of Cooling Loss Models for Axial Gas Turbines." Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-211696.
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Detta arbete behandlar undersökningen och valideringen av kylförlustmodellen i det nyligen framtagna programmet för endimensionell turbindesign, Mean Line Tool (MLT), skapat av Siemens Industrial Turbomachinery AB (SIT). Huvudsyftet är att undersöka med vilken noggrannhet MLT kan prediktera de extra aerodynamiska förluster som uppstår vid injektion av kylluft i en turbinpassage. För att validera kylförlustmodellen i MLT, har tidigare resultat från en testrigg på KTH används, där de extra förlusterna på grund av kylinjektion har mätts för ett flertal kylpositioner på en turbinledskena. Lokala flödes- och geometriska parametrar från testriggen ansattes i MLT för att möjliggöra en korrekt jämförelse. Ytterligare validering utfördes mot en testbaserad Siemens-korrelation, som är en sammanställning av ett flertal test från olika turbinkomponenter av SIT. I denna korrelation undersöktes kylning på en ledskenas bladprofil och plattform, samt på skovelns bladprofil, där en ökning av kylmassflöde relaterades till en förändring i stegverkningsgrad. Resultaten, från jämförelsen mellan data från testriggen på KTH samt beräkningar i MLT, visade att MLT predikterar extraförlusterna på grund av kylning på bladprofilen av en ledskena med bra noggrannhet. Däremot visar jämförelsen att MLT beräknar en lägre förlust för bakkantskylning. Således har en modifierad förlustkorrelation för bakkantskylning presenterats, som ger mer överensstämmande resultat mot testriggen. Jämförelsen mellan MLT beräkningar och den testbaserade Siemens-korrelationen visar att MLT inte predikterar förändringen i stegverkningsgrad, på grund av extra kylmassflöde, med bra noggrannhet. På grund av ett flertal osäkerheter har denna jämförelse endast användas för att kvalitativt belysa brister i kylförlustmodellen av MLT. Med detta i åtanke har det fastställts att plattformskylning vid främre delen av en turbinpassage skulle kunna vara mycket överpredikterad av MLT. Den övergripande slutsatsen är att MLT predikterar förändringen i gitterverkningsgrad på grund av kylning på en ledskenas bladprofil med bra noggrannhet, förutom bakkantskylning. Ytterligare jämförelser visar att MLT inte kan prediktera förändringen i stegverkningsgrad, på grund av extra kylmassflöde, med bra noggrannhet för olika kylda komponenter från gasturbinsportfolion av SIT. Således behövs vidare validering av MLT innan programmet kan implementeras i turbindesignsystemet av SIT.<br>This thesis concerns the investigation and validation of the cooling loss model in newly developed one-dimensional turbine design tool, Mean Line Tool (MLT), of Siemens Industrial Turbomachinery AB (SIT). The main objective is to investigate how accurately MLT can predict the additional aerodynamic losses due to cooling ejection in a turbine blade passage. To validate the cooling loss model of MLT, existing results from an annular sector cascade rig at KTH were used, where the additional losses due to cooling ejection were presented for several cooling locations on a stator vane profile. Local flow- and geometrical parameters from the cascade rig were set in MLT to enable a fair comparison. Moreover, a Siemens test based correlation was used, which is a data collection based on tests using various cooled components of SIT. Cooling ejection on a stator vane profile, stator vane platform and rotor blade profile was investigated, where an increase in coolant mass-flow was related to a change in stage efficiency. The results, when comparing data from the KTH cascade rig against calculations of MLT, show that MLT is able to accurately predict the additional loss due to cooling ejection on a stator vane profile. However, the comparison presents that the calculated loss for trailing edge cooling by MLT is lower than the results from the cascade rig. Therefore, a modified trailing edge cooling correlation is presented, which predicts the results from the cascade rig with better accuracy. Furthermore, comparisons between MLT calculations and the Siemens correlation present that MLT cannot predict the change in stage efficiency, due to added coolant mass-flow, accurately. However, due to several uncertainties, these results are qualitatively used to understand sources of prediction error in the cooling loss model of MLT. Having this in mind, it is established that hub platform cooling at the front part of a blade passage might be greatly overpredicted by MLT. The general conclusion is that MLT predicts the change in cascade efficiency due to coolant ejection with good accuracy for a stator vane profile, except for cooling at the trailing edge. However, MLT is not able to predict the change in stage efficiency, due to added coolant mass-flow, with good accuracy for various cooled components from the SIT gas turbine product portfolio. Thus, MLT needs further validation before it can be implemented into the SIT design system.
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Almstetter, Martin F. [Verfasser], and Frank-Michael [Akademischer Betreuer] Matysik. "Tools and applications for one- and two-dimensional gas chromatography – time-of-flight mass spectrometry-based metabolomics / Martin F. Almstetter. Betreuer: Frank-Michael Matysik." Regensburg : Universitätsbibliothek Regensburg, 2012. http://d-nb.info/1023312379/34.
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Pentland, Ian Alisdair. "A phonon emission study of quasi-1D electron gases." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325695.
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Håkansson, David. "Aerothermal and Kinetic Modelling of a Gas Turbine Dry Low Emission Combustion System." Thesis, KTH, Strömningsmekanik och Teknisk Akustik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-298477.
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Growing environmental concerns are causing a large transformation within the energy industry. Within the gas turbine industry, there is a large drive to develop improved modern dry-low emission combustion systems. The aim is to enable gas turbines to run on green fuels like hydrogen, while still keeping emission as NOx down. To design these systems, a thorough understanding of the aerothermal and kinetic processes within the combustion system of a gas turbine is essential. The goal of the thesis was to develop a one-dimensional general network model of the combustion system of Siemens Energy SGT-700, which accurately could predict pressure losses, mass flows, key temperatures, and emissions. Three models were evaluated and a code that emulated some aspects of the control system was developed. The models and the code were evaluated and compared to each other and to test data from earlier test campaigns performed on SGT-700 and SGT-600. Simulations were also carried out with hydrogen as the fuel. In the end, a model of the SGT-700 combustion chamber was developed and delivered to Siemens Energy. The model had been verified against test data and predictions made by other Siemens Energy thermodynamic calculation software, for a range of load conditions. The preforms of the model, when hydrogen was introduced into the fuel mixture, were also tested and compared to test data<br>En växande medvetenhet kring klimatfrågan, har medfört stora förändringar i energibranschen. I och med detta behöver även gasturbinindustrin förbättra de nuvarande dry-low emissions systemen och göra det möjligt för gasturbiner att förbränna gröna bränslen som väte. Samtidigt måste också utsläppen av NOx hållas nere. För att kunna utforma dessa system behövs en fullständig förståelse för de aerotermiska och kinetiska processerna i en gasturbins förbränningskammare. Målet med detta examensarbete var att utveckla en endimensionell generell nätverksmodell för förbränningssystemet i Siemens Energys SGT-700. Modellen skulle noggrant kunna förutsäga tryckförluster, massflöden, viktiga temperaturer samt utsläpp. Tre modeller utvärderades och en kod som emulerade vissa aspekter av styrsystemet utvecklades också. Modellerna och koden utvärderades och jämfördes mot varandra och även mot testdata från tidigare testserier som utfördes på SGT-700 och SGT-600. Simuleringar utfördes också med väte som bränsle. Slutligen levererades en modell av SGT-700 förbränningskammaren till Siemens Energy. Modellen har verifierats för en rad olika lastfall, mot testdata och data som genererats av andra termodynamisk beräkningsprogram som utvecklats av Siemens Energy. Hur modellen uppförde sig när väte var introducerat in i olika lastfall jämfördes också mot testdata
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Ballu, Manon. "Production d’un gaz de Bose unidimensionnel, résonances de Feshbach micro-onde et dynamique hors équilibre." Electronic Thesis or Diss., Paris 13, 2024. http://www.theses.fr/2024PA131033.
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Dans cette thèse, nous présentons une expérience produisant des condensats de Bose-Einstein de sodium. L'utilisation d'une puce à atomes, qui donne accès à des pièges magnétiques très allongés, permet de produire des gaz quantiques unidimensionnels dans le régime de quasi-condensat. Nous avons optimisé le refroidissement par évaporation et le transfert des atomes vers le piège magnétique de la puce à atomes. Nous nous sommes ensuite intéressés aux résonances de Feshbach micro-onde, dans le but de contrôler les interactions entre atomes, ce qui nécessite de fortes puissances micro-onde. Pour cela, nous utilisons un guide d'ondes coplanaire intégré à la puce à atomes. Des mesures d'oscillations de Rabi entre les deux niveaux hyperfins de l'état fondamental du sodium f=1 et f=2 montrent que nous pouvons atteindre des amplitudes magnétiques de plusieurs gauss pour le champ oscillant. Nous avons effectué la spectroscopie micro-onde des états moléculaires de la branche [f1=1, f2=2] les plus proches de la limite de dissociation. Les pertes d'atomes rapides observées au voisinage des résonances moléculaires semblent limiter leur intérêt comme outil de contrôle des interactions. Dans une deuxième partie nous avons étudié numériquement la dynamique hors équilibre d'un gaz de Bose unidimensionnel dans une boîte, en résolvant l'équation de Gross-Pitaevskii 1D. Le système est conduit hors d'équilibre à l'aide d'un potentiel extérieur oscillant. Nous nous sommes notamment intéressés aux profils de densité, aux énergies et à la distribution en impulsion. Les méthodes de transformée de diffusion inverse, avec le calcul du spectre de Lax, permettent d'étudier les solitons du système<br>In this thesis, we present an experiment producing sodium Bose-Einstein condensates. The use of an atom chip, giving access to highly elongated magnetic traps, allows to produce one-dimensional quantum gases in the quasi-condensate regime. We optimized evaporative cooling and atom transfer in the magnetic trap of the atom chip. We then turned to microwave Feshbach resonances, with the aim of controlling the interactions between atoms, which requires high microwave power. To achieve this, the atom chip encompasses a coplanar waveguide. Rabi oscillations measurements between the two hyperfine levels of the sodium ground state f=1 and f=2 show that we can achieve magnetic amplitudes of several gauss for the oscillating field. We have performed microwave spectroscopy of the molecular states in the [f1=1, f2=2] branch closest to the dissociation limit. The rapid loss of atoms observed close to the molecular resonances seems to limit their use as a tool for interaction control.In a second part, we numerically study the non-equilibrium dynamics of a one-dimensional Bose gas in a box, by solving the 1D Gross-Pitaevskii equation. The system is driven out of equilibrium using an oscillating external potential. We focused on density profiles, energies and momentum distributions. Inverse scattering transform methods, with the calculation of the Lax spectrum, are used to study the solitons of the system
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BAKHTIARI, MOHAMMAD REZA. "Quantum gases in quasi-one dimensional arrays." Doctoral thesis, Scuola Normale Superiore, 2007. http://hdl.handle.net/11384/85849.
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Perez, Florent. "Plasmons dans un potentiel unidimensionnelEtude par spectroscopie Raman de fils quantiques gravés." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1998. http://tel.archives-ouvertes.fr/tel-00285443.
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Nous avons étudiés des fils quantiques dopés de semi-conducteurs gravés par spectroscopie de diffusion Raman. Nous avons observés les excitations du gaz d'électrons. Celles-ci présentent des règles de sélection différentes de celles établies pour les systèmes bi-dimensionnels. Nous avons montré théoriquement qu'elles proviennent de la modification de la structure du champ électromagnétique local provoquée par la géométrie particulière des fils gravés. Pour cela nous avons dû calculer le champ local et l'introduire dans la section efficace de diffusion Raman pour en déduire les règles de sélection de toutes les excitations. Cela a permis de déterminer sans équivoque la nature des excitations qui sont des plasmons. Aucune excitations à une particule ni fluctuations de densité de spin n'a été observées. Nous avons étudié l'évolution continue des dispersions de ces plasmons lorsque la largeur du fil est réduite de 1 micromètre à 30 nm. Jusqu'à 60 nm, celles-ci sont en très bon accord avec les résultats d'un modèle hydrodynamique. Au dessous de 60 nm, la comparaison avec un modèle RPA s'impose. Le plasmon intra-bande dispersif est observé jusqu'à 45 nm, largeur en dessous de laquelle les spectres Raman sont dominés par des excitations localisées qui nécessitent une analyse ultérieure pour en déterminer clairement leur nature. Nous montrons à l'aide du modèle RPA que nous avons atteint la limite quantique pour un fil de largeur 55 nm. Une gamme étroite de fils dont les largeurs sont comprises entre 55 nm à 45 nm permet donc l'étude de gaz strictement unidimensionnel.<br />Nous avons cherché à déterminer la contribution de la forte illumination dans les conclusions précédentes. Nous avons utilisé pour cela la spectroscopie de magnéto-transmission infra-rouge qui ne modifie pas les conditions d'équilibre du gaz d'électrons. Une largeur critique de 130 nm a été extraite, en dessous de laquelle nous n'avons plus aucun signe de la présence d'électrons libres. La comparaison des mesures Raman et infra-rouge a permis l'établissement et la validation d'un modèle microscopique du potentiel de confinement présent dans les fils. Enfin nous avons fabriqués des échantillons de géométries plus complexes. L'observation et l'analyse par diffusion Raman des plasmons dans ces fils a montré que nous pouvions contrôler la géométrie du potentiel confinant les électrons et a mis en évidence des effets nouveaux tels que le repliement et le confinement de plasmons unidimensionnels.
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Klochan, Oleh V. Physics Faculty of Science UNSW. "Ballistic transport in one-dimensional p-type GaAs devices." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/35186.
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In this thesis we study GaAs one dimensional hole systems with strong spin-orbit interaction effects. The primary focus is the Zeeman splitting of 1D subbands in the two orthogonal in-plane magnetic field directions. We study two types of 1D hole systems based on different (311)A grown heterostructures: a modulation doped GaAs/AlGaAs square quantum well and an undoped induced GaAs/AlGaAs triangular quantum well. The results from the modulation doped 1D wire show enhanced anisotropy of the effective Lande g-factor for the two in-plane field directions (parallel and perpendicular to the wire), compared to that in 2D hole systems. This enhancement is explained by the confinement induced reorientation of the total angular momentum ^ J from perpendicular to the 2D plane to in-plane and parallel to the wire. We use the intrinsic anisotropy of the in-plane g-factors to probe the 0:7 structure and the zero bias anomaly in 1D hole wires. We find that the behaviour of the 0:7 structure and the ZBA are correlated and depend strongly on the orientation of the in-plane field. This result proves the connection between the 0:7 and the ZBA and their relation to spin. We fabricate the first induced hole 1D wire with extremely stable gate characteristics and characterize this device. We also fabricate devices with two orthogonal induced hole wires on one chip, to study the interplay between the confinement, crystallographic anisotropy and spin-orbit coupling and their effect on the Zeeman splitting. We find that the ratios of the g-factors in the two orthogonal field directions for the two wires show opposite behaviour. We compare absolute values of the g-factors relative to the magnetic field direction. For B || [011] the g-factor is large for the wire along [011] and small for the wire along [233]. Whereas for B || [233], the g-factors are large irrespective of the wire direction. The former result can be explained by reorientation of ^ J along the wire, and the latter by an additional off-diagonal Zeeman term, which leads to the out-of-plane component of ^ J when B || [233], and as a result, to enhanced g-factors via increased exchange interactions.
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Gao, Jian. "Fluorescence Enhancement using One-dimensional Photonic Band Gap Multilayer Structure." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1343753064.
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Massaro, Loredana Maria. "Multimodal one-dimensional photonic crystal cavities." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP035.
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La recherche en photonique intégrée concentre ses efforts sur le développement de dispositifs miniaturisés et efficaces pour des applications dans les domaines de l'information quantique, de la métrologie et de la médecine. Dans ce contexte,les cavités à cristaux photoniques occupent une position importante dans l'intégration de structures photoniques ayant taille réduite et propriétés spectrales adaptables. Ces dernières années, une attention particulière a été accordée aux cavités à cristaux photoniques constituées de matériaux semiconducteurs III-V,car leurs propriétés non linéaires sont un atout pour le développement d'états cohérents de la lumière par interactions non linéaires dans les circuits complexes.Dans cette thèse, nous présentons la conception, la fabrication et la caractérisation expérimentale de cavités à cristaux photoniques unidimensionnelles intégrées ensilicium-sur-isolant (SOI en anglais). Tout d'abord, nous détaillons la conception de nos cavités qui est basée sur le confinement doux (gentle confinement) du champ.Nous montrons que notre technique de conception permet de concevoir des cavités à cristaux photoniques multimodales et monomodales fonctionnant à la fenêtre telecom. La technique de conception introduite est polyvalente et facilement adaptable pour concevoir des cavités de différents matériaux, comme l'InGaP, le Siou l'InP. Ensuite, nous détaillons la fabrication de structures photoniques III-V intégrées de manière hétérogène sur SOI. Depuis le collage des deux niveaux jusqu'au dispositif final, le processus de fabrication est décrit et les principaux défis rencontrés sont commentés. La fabrication de cavités en silicium est également décrite.La caractérisation expérimentale des cavités est réalisée en mesurant la transmission des échantillons. Nous présentons comment adapter les propriétés spectrales des cavités par une variation nanométrique de leurs paramètres géométriques, et commentons certaines particularités du couplage multimodal<br>Integrated photonics research focuses its efforts in developing miniaturised and efficient devices for applications in quantum information, metrology and medicine. In this context, photonic crystal cavities occupy a leading position in the integration of photonic structures owning small footprint and tailorable spectral properties. Special attention in recent years is given to photonic crystal cavities consisting of III-V semiconductor materials, as their nonlinear properties are an asset for further development in complex circuitry of coherent states of light through nonlinear interactions. In this thesis, we present the design, fabrication and experimental characterisation of high-Q one-dimensional photonic crystal cavities integrated on silicon on insulator. First, we detail the design of our cavities which is based on the gentle confinement of the field. We show that our design technique allows the devising of multimodal as well as single-mode photonic crystal cavities working at telecom window. The introduced design technique is versatile and easily tailorable to devise cavities of different materials, as InGaP, Si, or InP. Then, we detail the fabrication of III-V photonic structures heterogeneously integrated on silicon on insulator. From the adhesive bonding of the two levels to the final integrated device, fabrication process flow is reported and main challenges encountered commented. Fabrication of silicon-based cavities is also reported. Experimental characterisation of the cavities is conducted by measuring the transmission of the samples. We present how to tailor the spectral properties of the cavities through nanometric variation of their geometrical parameters, and comment on some peculiarities of multimodal coupling
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Patel, Nalin Kumar. "Observations of confinement in quasi-one- and -zero-dimensional GaAs/AlGaAs structures." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386352.
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Khodami, Maryam. "Dispersion Characteristics of One-dimensional Photonic Band Gap Structures Composed of Metallic Inclusions." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23179.
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An innovative approach for characterization of one dimensional Photonic Band Gap structures comprised of metallic inclusions (i.e. subwavelength dipole elements or resonant ring elements) is presented. Through an efficient S- to T-parameters conversion technique, a detailed analysis has been performed to investigate the variation of the dispersion characteristics of 1-D PBG structures as a function of the cell element configuration. Also, for the first time, the angular sensitivity of the structure has been studied in order to obtain the projected band diagrams for both TE and TM polarizations. Polarization sensitivity of the subwavelength cell element is exploited to propose a novel combination of elements which allows achieving PBGs with simultaneous frequency and polarization selectivity. The proposed approach demonstrates that the dispersion characteristic of each orthogonal polarization can be independently adjusted with dipole elements parallel to that same polarization. Generally, the structure has potential applications in orthomode transducer, and generally whenever the polarization of the incoming signal is to be used as a means of separating it from another signal in the same frequency band that is of orthogonal polarization. The current distribution and the resonance behavior of the ring element is studied and the effect of resonance on dispersion characteristics of 1-D PBGs composed of rings is investigated for the first time, for both individual and coupled rings. Interestingly, it is observed that 1-D PBG composed of resonant elements consistently has a bandgap around the resonant frequency of the single layer structure.
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Barnwell, Ellis. "One and two-dimensional propagation of waves in periodic heterogeneous media : transient effects and band gap tuning." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/one-and-twodimensional-propagation-of-waves-in-periodic-heterogeneous-media-transient-effects-and-band-gap-tuning(9a5bd9d7-09da-46a8-ae57-b63d9d815f10).html.
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In this thesis, the propagation of transient waves in heterogeneous media and the tuning of periodic elastic materials are studied. The behaviour of time harmonic waves in complex media is a well understood phenomenon. The primary aim of this text is to gain a deeper understanding into the propagation of transient waves in periodic media. The secondary aim is to explore the time harmonic behaviour of two dimensional pre-stressed elastic media and investigate the plausibility of band gap tuning. We begin this text by investigating the reflection of pulses from a semi-infinite set of point masses (we call 'beads') on a string. The reflected pulse is formulated using Fourier transforms which involve the harmonic reflection coefficient. We find that the reflected amplitude of a harmonic wave depends on its frequency. We then ask whether it is possible to find an effective reflection coefficient by assuming the beaded portion of the string is given by some effective homogeneous medium. An effective reflection coefficient is found by assuming the homogeneous medium has the wavenumber given by the infinite beaded string. This effective reflection coefficient is compared to the exact reflection coefficient found using the Wiener-Hopf technique. The results from studying the reflection problem gave inspiration to chapter 4, which focuses on the time dependent forcing of an infinite beaded string that is initially at rest. We again use the Fourier transform to find a time dependent solution. The z-transform is then used, after sampling the solution at the bead positions. We impose a sinusoidal loading which is switched on at a specified time. In doing this we are able to explore how the system behaves differently when excited in a stop band, a pass band and at a frequency on the edge between the two. An exact solution for the infinite beaded string is found at any point in time by expanding the branch points of the solution as a series of poles. We compare this exact solution to the long time asymptotics. The energy input into the system is studied with the results from the exact solution and long time approximation showing agreement. Interesting behaviour is discovered on the two edges between stop and pass bands. In chapter 5 the effect of a nonlinear elastic pre-stress on the wave band structure of a two dimensional phononic crystal is investigated. In this chapter we restrict ourselves to incompressible materials with the strain energy functions used being the neo-Hookean, Mooney-Rivlin and Fung. The method of small-on-large is used to derive the equation for incremental elastic waves and then the plane wave expansion method is used to find the band structure. Finally, chapter 6 focuses on the same geometry with a compressible elastic material. The strain energy function used is the one suggested by Levinson and Burgess. We use the theory of small-on-large to derive the incremental equations for coupled small amplitude pressure and shear waves in this material. In both compressible and incompressible materials we show how it is possible to control the stop bands in a material by applying a large elastic pre-stress.
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Tuenter, Hans J. H. "Worst-case bounds for bin-packing heuristics with applications to the duality gap of the one-dimensional cutting stock problem." Thesis, University of Birmingham, 1997. http://etheses.bham.ac.uk//id/eprint/266/.
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The thesis considers the one-dimensional cutting stock problem, the bin-packing problem, and their relationship. The duality gap of the former is investigated and a characterisation of a class of cutting stock problems with the next round-up property is given. It is shown that worst-case bounds for bin-packing heuristics can be and are best expressed in terms of the linear programming relaxation of the corresponding cutting stock problem. The concept of recurrency is introduced for a bin-packing heuristic, which allows a more natural derivation of a measure for the worst-case behaviour. The ideas are tested on some well known bin-packing heuristics and (slightly) tighter bounds for these are derived. These new bounds (in terms of the linear programming relaxation) are then used to make inferences about the duality gap of the cutting stock problem. In particular; these bounds allow à priori, problem-specific bounds. The thesis ends with conclusions and a number of suggestions to extend the analysis to higher dimensional problems.
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Tanner, Matthew Wilder. "Multidimensional Modeling of Solid Propellant Burning Rates and Aluminum Agglomeration and One-Dimensional Modeling of RDX/GAP and AP/HTPB." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2706.pdf.
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BHANDARI, CHURNA B. "FIRST-PRINCIPLES STUDY OF ELECTRONIC AND VIBRATIONAL PROPERTIES OF BULK AND MONOLAYER V2O5." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1459296089.
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Shulenburger, Luke Nathan. "Correlation in the one dimensional electron gas /." 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337923.
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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008.<br>Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6872. Adviser: Richard M. Martin. Includes bibliographical references (leaves 104-109) Available on microfilm from Pro Quest Information and Learning.
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Cheng, Hsien-Lung, and 鄭憲隆. "One-dimensional silicon nanostructure for hydrogen gas sensor." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/82604143772786903888.
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碩士<br>國立臺灣科技大學<br>電子工程系<br>100<br>There are many technologies to fabricate one-dimensional silicon nanostructure.
The silicon nanostructures were used for many applications. For example, the silicon nanostructures have high reflection property in solar cell. In the electron field emission, the silicon nanostructures possess the higher aspect ratio and numerous emission sites. For sensor researching, it has higher surface area to volume ratio that can improve the sensitivity.
We fabricated the one dimension silicon nanostructure for hydrogen sensor. In this research, we synthesized different morphology of silicon nanostructure using wet electroless etching technique. The field emission scanning electron microscopy (FE-SEM) was used to observe the surface morphology of silicon nanostructure. The micro-Raman and Fourier transform infrared (FT-IR) was used to investigate the bonding of silicon nanostructure. Finally, we carried out the electrical analyze of gas sensor system with hydrogen sensing.
In this study, we use the two-step wet electroless etching technique to form the straw-like silicon nanowire. It can be observed that some different layers in SEM photographs. The top layer was straw-like silicon nanowire, and the middle layer was straight aligned silicon nanowire, and the bottom layer was silicon base which is the bulk silicon. The straw-like silicon nanowire was found the the bonding of Si-O-Si about 1173cm-1 in FT-IR spectrum. And it also observed some red shift in Raman spectrum. Because of the higher surface area to volume ratio and Si-O-Si bonding, the performance of this straw-like structure hydrogen sensor was improved. Moreover, this hydrogen gas sensor was also modified with Pt nanoparticles, which can enhance the ratio of hydrogen gas dissolve into the metal-semiconductor interface.
Finally we tried to make the porous structure with high density and high aspect ratio also by wet electroless etching technique. This porous possessed the high surface area which had the superior sensitivity.
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Yeh, Li-Ko, and 葉禮閣. "One-Dimensional and Two-Dimensional Materials for Solar Cells and Gas Sensors." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ab8rfy.
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博士<br>國立臺灣大學<br>電子工程學研究所<br>105<br>Particular physical and chemical properties of nanomaterials have promised and exhibited great applications in manufacturing various nanodevices such as electron field emitters, sensors, photovoltaics and other electronic components. In this thesis, I will experimentally explore three topics which realize the improvement of solar cells and gas sensors. The first topic is that ZnO nanostructure as an anti-reflectance coating for commercial GaInP/GaAs/Ge triple-junction solar cells. Covered by the unique tapered nanoneedles, the efficiency of the tandem solar cell coated with the ZnO nanoneedles is effectively improved 45.8 % higher than that with bare surface. The excellent omnidirectionality and heat sustainability demonstrated here bring promising potential for multi-junction concentrator solar cells. The second topic is a simple and low cost hydrothermal process was adopted to synthesize corals-like ZnO for gas sensors applications. Toluene was detected with the photoactivated gas detector by 2μW/cm2 ultraviolet (UV) illumination. Giant sensitivity enhancement of the detector is due to the high surface area/volume ratio morphology of corals-like ZnO nanorod arrays (NRAs) and photoinduced oxygen ions increasing by UV illumination. The corresponding sensitivity (ΔR/R0) of ZnO corals-like NRAs based detector was approximately enhanced 1022 % than ZnO thin film sensors. The third topic is about two-dimensional (2D) nanomaterials atomic MoS2 gas sensors. A highly sensitive gas sensor based on the chemical vapor deposition synthesized MoS2 was developed. The target gas was methanol. We demonstrated the highly enhanced performance of atomic trilayer MoS2 gas sensor by oxygen plasma treatment. During the plasma treatment 40s, the response of MoS2 gas sensor is more 500 % higher than original MoS2 (from 5% to 27.2%) and increase the limit of detection from 2000 ppm to 100 ppm. Photoluminescence (PL) clearly reveals the number of defects which contribute the ability of gas adsorption. This result can improve the device performance which has the same mechanism of 2D nanomaterials.
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Wenger, Trevor. "Experiments on a one-dimensional Bose gas Thomas Fermi to Tonks-Girardeau /." 2007. http://www.etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1758/index.html.
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Chang, Tsu-Ming, and 張祖明. "One-Dimensional Bose Gas with Delta Function Interactions in an Infinite Well." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/66068703691602136222.
Full textAbstract:
碩士<br>國立清華大學<br>物理研究所<br>84<br>One-dimensional bosons with a delta function interaction in an
infinite well is analyzed. Its wave function, energy spectrum,
and other thermodynamic properties are obtained. First, for
comparison, we deal with the problem that iti- nerant particles
interact with a point defect via a delta function interaction
in an infinite well in chapter 2, and we find perturbation
results to be a good approximation. Secondly, we suppose that
the bose gas interact with a delta function interaction in an
infinite well, and then we analyze the wavefunction and
spectrum. In chapter 3 we deal with two bosons case, and in
chapter 4 we generalize the re- sults to many bosons. When we
take the thermodynamic limit, we get the results which are the
same as those employed by the periodic boundary condition.
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Chen, Hsin-Li, and 陳新立. "Electrical measurement of one-dimensional composite nanowires and its application for gas sensor." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/44562460085124743491.
Full textAbstract:
碩士<br>國立雲林科技大學<br>電子與資訊工程研究所<br>93<br>In the this work, one-dimensional composite materials of the gold nanopartical embedded in an amorphous silicon nanowire was synthesized by microwave plasma enhance chemical vapor deposition (MWPECVD) system on the SiNx thin film with coating a gold film. Growth of the one-dimensional composite nanowires is not easy, because the plasma environment in the chamber with a little variation, the silica nanowires will be synthesized instead of the composite nanowires. We used the silica nanowires of the different conditions to detect nitrogen and oxygen respectively, and High Resolution Scanning Electron Microscopy (HRSEM), Electron Beam Lithography (EBL) were used for fabrication electrode and electrical measurement of one-dimensional composite nanowires and silica nanowire.
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Chen, Li-Chun, and 陳立鈞. "The preparation of gas diffusion electrodes using one-dimensional carbon substrate and Pt sols." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/40974120787323380194.
Full textAbstract:
碩士<br>元智大學<br>化學工程與材料科學學系<br>96<br>In this research, a carbon membrane with well-aligned pore structure is synthesized by template method. This carbon membrane is used together with Pt sols for improving performance of PEMFCs.
Epoxy solution is deposited into pore of a commercially available AAO (anodic aluminum oxide) membrane. After carbonization under N2 environment at elevated temperature, the carbon-AAO composite is subjected to a 2-step AAO removal procedure. By controlling the extent of AAO removal in the first step, and the use of a second carbon-filling-and-carbonization procedure, we achieve a continuous carbon membrane with pore structure replicating that of AAO template.
In this study, we use different solvents and additivies (involved Nafion and Carbon) over Pt sols to compare the ink stability. We use Contact angle, precipitation, Particle size distribution and Zata potential to analyze the stability of ink. The result shows that the addition of IPA and MeOH over Pt sols forces quick precipitation. We prepared thinner electrode made of Pt sols, but its performance decreases quickly from 35 to 70oC.However, the trend is reverse compared to Pt/C. The preparation of the electrode in combination with Pt sols and One-dimensional carbon material improves mass transport limitation.
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Mehta, Abhijit C. "Zigzag Phase Transition in Quantum Wires and Localization in the Inhomogeneous One-Dimensional Electron Gas." Diss., 2013. http://hdl.handle.net/10161/7191.
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<p>In this work, we study two important themes in the physics of the interacting one-dimensional (1D) electron gas: the transition from one-dimensional to higher dimensional behavior, and the role of inhomogeneity. The interplay between interactions, reduced dimensionality, and inhomogeneity drives a rich variety of phenomena in mesoscopic physics. In 1D, interactions fundamentally alter the nature of the electron gas, and the homogeneous 1D electron gas is described by Luttinger Liquid theory. We use Quantum Monte Carlo methods to study two situations that are beyond Luttinger Liquid theory --- the quantum phase transition from a linear 1D electron system to a quasi-1D zigzag arrangement, and electron localization in quantum point contacts. </p><p>Since the interacting electron gas has fundamentally different behavior in one dimension than in higher dimensions, the transition from 1D to higher dimensional behavior is of both practical and theoretical interest. We study the first stage in such a transition; the quantum phase transition from a 1D linear arrangement of electrons in a quantum wire to a quasi-1D zigzag configuration, and then to a liquid-like phase at higher densities. As the density increases from its lowest values, first, the electrons form a linear Wigner crystal; then, the symmetry about the axis of the wire is broken as the electrons order in a quasi-1D zigzag phase; and, finally, the electrons form a disordered liquid-like phase. We show that the linear to zigzag phase transition occurs even in narrow wires with strong quantum fluctuations, and that it has characteristics which are qualitatively different from the classical transition.</p><p>Experiments in quantum point contacts (QPC's) show an unexplained feature in the conductance known as the ``0.7 Effect''. The presence of the 0.7 effect is an indication of the rich physics present in inhomogeneous systems, and we study electron localization in quantum point contacts to evaluate several different proposed mechanisms for the 0.7 effect. We show that electrons form a Wigner crystal in a 1D constriction; for sharp constriction potentials the localized electrons are separated from the leads by a gap in the density, while for smoother potentials, the Wigner crystal is smoothly connected to the leads. Isolated bound states can also form in smooth constrictions if they are sufficiently long. We thus show that localization can occur in QPC's for a variety of potential shapes and at a variety of electron densities. These results are consistent with the idea that the 0.7 effect and bound states observed in quantum point contacts are two distinct phenomena.</p><br>Dissertation
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Dong, Yao-Jhong, and 董耀中. "Growth mechanism of CuO one-dimensional nanostructures by thermal oxidation process and their CO gas sensing properties." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/95176930067603502799.
Full textAbstract:
碩士<br>國立中興大學<br>材料科學與工程學系所<br>98<br>We have successfully synthesized one-dimensional CuO nanowires by thermal oxidation and observed their growth mechanism. The CuO nanowires were adopted to fabricate a simple gas sensor which can be used for detecting low concentration CO. In the atmosphere at temperatures between 300℃ to 600℃, CuO nanowires could be grown. Once the annealing temperature was higher than 700℃or lower than 200℃, no CuO nanowires could be formed. The varieties of synthesis temperature would affect the diameters of CuO nanowires, and the lengths of nanowires would increase with increasing synthesis time. The diameters of CuO nanowires synthesized at 450℃for 6 hours were approximately 130 nm, and the lengths could be up to 15μm or longer. It was found that the number of nanowires synthesized by thermal oxidation would decrease when the substrate was annealed for longer time, which suggests that the CuO nanowires might be grown by the anisotropic atomic diffusion mechanism. The as-synthesized CuO nanowires were indentified as a monoclinic crystal structure and cumulated along with (110) by XRD and TEM analysis. The gas sensor device fabricated by CuO nanowires exhibited good response capacity for detecting low CO concentration at an operating temperature of 300℃. The sensitivity of the gas sensor could be up to 181% at CO concentration of 50ppm, and could still reach 138% even if the CO concentration was as low as 5ppm. At low CO concentration, the response and recovery times for the gas sensor device were on average about 180 seconds and 220 seconds, respectively. Therefore, CuO nanowires have great potential for low- concentration CO gas sensor device.
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Gouws, Johannes Jacobus. "Combining a one-dimensional empirical and network solver with computational fluid dynamics to investigate possible modifications to a commercial gas turbine combustor." Diss., 2007. http://upetd.up.ac.za/thesis/available/etd-04212008-074344/.
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Ko, Rong-Ming, and 柯榮明. "Study on the Growth Mechanisms of One-Dimensional Tungsten Oxide Nanostructures and Their Applications in Gas Sensors and Field Emitters." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/82952078034745784202.
Full textAbstract:
博士<br>國立成功大學<br>微電子工程研究所碩博士班<br>97<br>In this thesis, study on the growth mechanisms of the evolution of one-dimensional
tungsten oxide (TO) nanostructures from nanowires to nanosheets and their applications in
gas sensors and field emitters were proposed and investigated. Nanowires and nanobelts
were self-synthesized on sputter-deposited tungsten-based thin film by a simple thermal
annealing process in N2 ambient. Techniques of various analysis including FESEM,
HRTEM, SAED, XRD and XPS were employed to characterize the growing conditions and
properties of nanostructures. In addition, a measurement system consists of Agilent
34970A, E3646A and HP 4284A LCR meter, was used for gas sensing measurement. In
addition, Keitheley 237 was also used to measure the field-emission characteristics, which
was carried out at room temperature in a vacuum chamber with a pressure of 5×10-6 torr.
The dependences of the field enhancement factor (β), driving current, and turn-on voltage
were extracted by current-voltage characteristic based on Fowler-Nordheim equation.
First, a possible mechanism for the transformation of nanomorphology from wires
to sheet is reported. In experiments, a simple thermal annealing process was employed to
self-synthesize TOs nanostructures on sputtering-deposited tungsten films in N2 ambient
with thermal budgets of 750°C for 0.5~3 h and 650~900°C for 0.5 h, respectively. Based
on experimental results, the lower limit of temperature for the self-synthesis of tungsten
oxide nanowires (TONWs) from sputtering-deposited W films might lie in the range of
500~600°C, which could be related to the temperature necessary to provide enough
activation energy for the formation of WOx nanocrystallites and W18O49 nucleation sites.
For samples annealed at 750°C for 0.5 and 1 h, dense and uniformly distributed TONWs
with typical diameters of 15~25 nm, typical lengths of 0.15~0.30 μm, and typical densities
of 250~300 μm-2 were obtained. The self-synthesis of TONWs can be related to the
formation of WOx nanocrystallites caused by chemical reaction of tungsten and oxygen
contained in the film and then commenced from the nucleus sites of W18O49 crystallites at
the grain boundaries of WOx nanocrystallites on the surface of samples during thermal
annealing. Oxygen might be from impurities in the tungsten target and/or the exposure of
tungsten films to air. Further increases the thermal budgets, which samples annealed at
750°C for >2 h or >850°C for 0.5 h, a drastic change in surface morphologies of the
annealed samples with both the density and size of the nanosheets are seen increasing
accompanied with the decrease in the wire density is observed. Both the self-synthesis of
the TO nanowires and nanobelts have been identified that comprise the major
crystallization phase of monoclinic W18O49 (JCPDS No. 36-0101) with a growth direction
of [010].
In addition, based on experimental results that show the formation and
re-crystallization of an amorphous interface layer between two neighboring nanowires
which were linked together by their (502) planes, a possible mechanism for the
transformation of nanomorphology from wires to sheet was proposed. First, neighboring
nanowires might connect to each other with misalignments along their [010] direction
because the nanowires are dense (250~300 μm-2) and random in orientation. Then, a twist
and/or rotation misalignment ent between their (502) planes might be presented. However,
the boundary is not stable, which should give it a higher surface energy. Accordingly, the
divergence of the crystallography was tailored during thermal annealing and led to the
formation of an amorphous interface. Once the thermal budget was high enough, the
amorphous interface re-crystallized to further reduce the surface energy of the two
amorphous/ (502) interfaces. Finally, all interfaces or boundaries disappeared and
nanosheets with the same crystallography of W18O49 was formed. The same evolution
process is also applicable to the formation of nanobundles from more than two neighboring
nanowires, which were also found in samples annealed at a high thermal budget.
Essentially, the use of TONWs as gas sensing materials is very attractive because
they exhibit physical and chemical properties that are very different from those of their
bulk or film counterparts. In addition, the sensitivity of TONW sensors to gases can be
substantially improved and the working temperature can also be reduced because of the
large surface to volume ratio (SVR) as well as the enormous number of surface atoms
and/or dimensional confinement of electrons. Therefore, a three-layer structure
TONW-based gas sensor was fabricated and its sensing performance for NO2 of different
concentrations at different working temperatures was also investigated.
During the fabrication processes of the proposed TONW-based gas sensor. N-type
Si wafers and WCx (W:C=70:30 wt%) target were used. RF sputtering and
plasma-enhanced chemical vapor deposition (PECVD) were employed for the deposition
of WCx (W:C=70:30 wt%) electrodes and the SiO2 layer, respectively. The thicknesses of
the bottom electrodes, middle SiO2 layer and top electrodes were 60, 300 and 120 nm,
respectively. Then, the devices were patterned by reactive ion etching (RIE)and subjected
to buffer oxide wet etching for 90 s to remove the SiO2 layer from the periphery. Finally,
thermal annealing at 750°C in N2 (60 sccm) ambient for 30 min was conducted for the
self-growth of TONWs in the window area created by the side etching of the SiO2 layer.
Experimental results showed that self-growth TONWs have main phase of
W18O49(010) and typical lengths and diameters of 0.15~0.4 μm and 17~25 nm, respectively.
The present sandwich structure allows TONWs to firmly link the top and bottom electrodes
without the use of submicron photolithography. The monoclinic W18O49 behaves as an
n-type semiconductor with oxygen vacancies. Essentially, a single TONW has SVRs of
around (1.6~2.35)×106 cm-1, which was found to be about 7.5~11.6 times higher than those
of the film WO3 sensors prepared at a firing temperature of 700°C. Because of the presence
of oxide vacancies and large SVR of TONWs for gas absorption, good sensor performance
with a sensitivity as high as 9.3, a short response time (about 9 s), and a detectability of 2
ppm of NO2 was achieved using eight sensors in a series connection. It is expected that the
sensitivity of gas sensors can be further increased by increasing the number of TONWs in
each cell in series-connected sensors.
In addition, the self-synthesis of TONWs with a high aspect ratio had been obtained
from our previous studies, which exhibit good electron field emission characteristics with a
typical turn-on field of about 1.7 V/μm were comparable with CNTs. In order to expand its
application into low voltage vacuum operable microelectronics, use of current fusing
method for the fabrication of lateral W18O49 nanowires in a tip-to-tip configuration with a
nanogap is proposed for the first time.
The key fabrication processes of the proposed lateral-type field emission device is
divided into two main stages. Firstly, n-type 0.01 Ω-cm <100> silicon wafers were used
and the 500-nm-thick wet SiO2 layer was grown at 1050°C for 1 h. In this stage,
silicon-on-insulator (SOI) substrates were obtained. Secondary, 50-nm-thick patterned W
films with tunnel length of 20 μm and width of 5 μm were sputter-deposited on the SOI
substrate by photolithography and dc sputtering method. Then, current densities ranging
from 220 to 280 mA/μm2 were applied to the W films on SOI for current fusing in
atmospheric air. It was found that, for 50-nm-thick patterned W films, the critical current
density for the generation of nanogap is about 220 mA/μm2. The nanogaps were observed
widening as the current density was further increased. When the density was driven over
280 mA/μm2, it might cause an instant over-heating and destroy the W thin film on the
edge of the nanogaps. Based on our experimental results, under an optimized current
density of 240 mA/μm2 for 10 s, nanogap in the range of 0.2~0.4 μm could be obtained.
Finally, all fused samples were subjected to thermal annealing from 750 to 850°C
temperature in N2 ambient for 30 min. It was found that the sample annealed at 800°C
exhibited uniform morphology of TONWs on the edges of the nanogap. The typical length,
diameter, and aspect ratio of TONWs grown on the sample annealed at 800°C were
125~220 nm, 17~25 nm, and 5~13, respectively, while the effective nanogap of the lateral
TONWs in tip-to-tip configuration were further reduced to be of about 0.18 μm. A
comparison for the 750°C and 850°C samples, it reveals that the turn-on voltage is quite
high (about 16.5 and 12 V, respectively) at 1 μA and the field enhancement factor is very
low (about 56 and 340 μm-1 respectively). However, the 800°C-annealed sample exhibited
a fairly good field emission characteristics with a low turn-on voltage of 2.7 V at 1 μA and
a high electric field enhancement factor of ~ 660 μm-1. Stable and profound
Fowler-Nordheim characteristics were observed at around 81.8 V with the FE current in
excess of 8 mA. The relatively low turn-on voltage might be attributed to the high aspect
ratio of TONWs and the realization of the nanogap of the lateral TONWs in tip-to-tip
configuration.