Dissertations / Theses on the topic 'Cascade'
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Taboada, Martín O. "Automated target cascade." [S.l.] : [s.n.], 2006. http://opus.kobv.de/tuberlin/volltexte/2006/1435.
Full textPatterson, Steven Gregory. "Bipolar cascade lasers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8805.
Full textIncludes bibliographical references.
This thesis addresses issues of the design and modeling of the Bipolar Cascade Laser (BCL), a new type of quantum well laser. BCLs consist of multiple single stage lasers electrically coupled via tunnel junctions. The BCL ideally operates by having each injected electron participate in a recombination event in the topmost active region, then tunnel from the valence band of the first active region into the conduction band of the next active region, participate in another recombination event, and so on through each stage of the cascade. As each electron may produce more than one photon the quantum efficiency of the device can, in theory, exceed 100%. This work resulted in the first room temperature, continuous-wave operation of a BCL, with a record 99.3% differential slope efficiency. The device was fully characterized and modeled to include light output and voltage versus current bias, modulation response and thermal properties. A new singlemode bipolar cascade laser, the bipolar cascade antiresonant reflecting optical waveguide laser, was proposed and modeled.
by Steven G. Patterson.
Ph.D.
Baumann, Morgaine Lillian. "Cascade & Run." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/5121.
Full textYamazaki, Yasuhiro H. "The cyclogenetic energy cascade." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ49977.pdf.
Full textHanson, Timothy B. "Cascade adaptive array structures." Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1173207031.
Full textMain, A. D. J. "Annular turbine cascade aerodynamics." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239350.
Full textWinning, Leonard H. "New Radical Cascade Chemistry." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494312.
Full textWilliams, Benjamin S. (Benjamin Stanford) 1974. "Terahertz quantum cascade lasers." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17012.
Full textIncludes bibliographical references (p. 297-310).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
The development of the terahertz frequency range has long been impeded by the relative dearth of compact, coherent radiation sources of reasonable power. This thesis details the development of quantum cascade lasers (QCLs) that operate in the terahertz with photon energies below the semiconductor Reststrahlen band. Photons are emitted via electronic intersubband transitions that take place entirely within the conduction band, where the wavelength is chosen by engineering the well and barrier widths in multiple-quantum-well heterostructures. Fabrication of such long wavelength lasers has traditionally been challenging, since it is difficult to obtain a population inversion between such closely spaced energy levels, and because traditional dielectric waveguides become extremely lossy due to free carrier absorption. This thesis reports the development of terahertz QCLs in which the lower radiative state is depopulated via resonant longitudinal-optical phonon scattering. This mechanism is efficient and temperature insensitive, and provides protection from thermal backfilling due to the large energy separation between the lower radiative state and the injector. Both properties are important in allowing higher temperature operation at longer wavelengths. Lasers using a surface plasmon based waveguide grown on a semi-insulating (SI) GaAs substrate were demonstrated at 3.4 THz in pulsed mode up to 87 K, with peak collected powers of 14 mW at 5 K, and 4 mW at 77 K.
Additionally, the first terahertz QCLs have been demonstrated that use metalmetal waveguides, where the mode is confined between metal layers placed immediately above and below the active region. These devices have confinement factors close to unity, and are expected to be advantageous over SI-surface-plasmon waveguides, especially at long wavelengths. Such a waveguide was used to obtain lasing at 3.8 THz in pulsed mode up to a record high temperature of 137 K, whereas similar devices fabricated in SI-surface-plasmon waveguides had lower maximum lasing temperatures due to the higher losses and lower confinement factors. This thesis describes the theory, design, fabrication, and testing of terahertz quantum cascade laser devices. A summary of theory relevant to design is presented, including intersubband radiative transitions and gain, intersubband scattering, and coherent resonant tunneling transport using a tight-binding density matrix model. Analysis of the effects of the complex heterostructure phonon spectra on terahertz QCL design are considered. Calculations of the properties of various terahertz waveguides are presented and compared with experimental results. Various fabrication methods have been developed, including a robust metallic wafer bonding technique used to fabricate metal-metal waveguides. A wide variety of quantum cascade structures, both lasing and non-lasing, have been experimentally characterized, which yield valuable information about the transport and optical properties of terahertz devices. Finally, prospects for higher temperature operation of terahertz QCLs are considered.
by Benjamin S. Williams.
Ph.D.
Pack, Camille Marian. "Cascade Lake: A Novel." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/365.
Full textMizuta, Atsushi. "Universality of Kolmogorov's Cascade Picture in Inverse Energy Cascade Range of Two-dimensional turbulence." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189339.
Full textSenalp, Erdem Turker. "Cascade Modeling Of Nonlinear Systems." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608578/index.pdf.
Full text2) Introduction of B-Spline curve nonlinearity representations instead of polynomials in cascade modeling. As a result, local control in nonlinear system modeling is achieved. Thus, unexpected variations of the output can be modeled more closely. As an important demonstration case, a model is developed and named as Middle East Technical University Neural Networks and Cascade Model (METU-NN-C). Application examples are chosen by considering the Near-Earth space processes, which are important for navigation, telecommunication and many other technical applications. It is demonstrated that the models developed based on the contributions of this work are especially more accurate under disturbed conditions, which are quantified by considering Space Weather parameters. Examples include forecasting of Total Electron Content (TEC), and mapping
estimation of joint angle of simple forced pendulum
estimation of joint angles of spring loaded inverted double pendulum with forced table
identification of Van der Pol oscillator
and identification of speakers. The operation performance results of the International Reference Ionosphere (IRI-2001), METU Neural Networks (METU-NN) and METU-NN-C models are compared qualitatively and quantitatively. As a numerical example, in forecasting the TEC by using the METU-NN-C having Bezier curves in nonlinearity representation, the average absolute error is 1.11 TECu. The new cascade models are shown to be promising for system designers and operators.
Rochat, Michel. "Far-infrared quantum cascade lasers." Online version, 2002. http://bibpurl.oclc.org/web/24095.
Full textDhirhe, Devnath. "Monolithic tuneable quantum cascade lasers." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4604/.
Full textbin, Hashim Hasnul Hidayat. "Travelling-wave series cascade lasers." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493548.
Full textDumrongchai, Nuethip. "Palladium Catalyzed Multicomponent Cascade Reactions." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487516.
Full textCommin, James Paul. "Short wavelength quantum cascade lasers." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.575411.
Full textFreeman, J. R. "Heterogeneous terahertz quantum cascade lasers." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599209.
Full textCooper, Ian Ronald. "Palladium-indium bimetallic cascade processes." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401087.
Full textMarchbank, John David. "Palladium-catalysed cascade ring syntheses." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405708.
Full textHasan, Mohammad Mubashyeer. "Catalytic cascade chemistry for glycobiology." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441265.
Full textSundberg, Patrik P. (Patrik Per) 1980. "Pose estimation using cascade trees." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17985.
Full textIncludes bibliographical references (p. 57-58).
In this thesis, I implemented and extended a face detector, based on cascades of boosted features, for use in real time systems. The extensions are twofold. First, I designed a way of combining several cascades into a cascade tree, and showed how such a tree provides a powerful mechanism for combining detector efficiency and accuracy. When the training data has large variations, the cascade tree yields a faster detector, and when the data has only small variations, there is a distinct detection rate improvement. As a second extension, I designed a system for pose estimation based on an array of cascades. I performed an evaluation of this system and compared to normalized cross-correlation.
by Patrik Sundberg.
M.Eng.
Zakaria, Gaguk. "Cascade RLS with Subsection Adaptation." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26295.
Full textPh. D.
Carstens, Charl. "Major Incident Communication Cascade Evaluation." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/2858.
Full textKischkat, Jan-Ferenc. "External Cavity Quantum Cascade Lasers." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17303.
Full textThis thesis thoroughly investigates theoretically and experimentally the effects many physical parameters have on the performance of Tunable External-Cavity Quantum-Cascade Lasers (EC-QCLs). These include, among others, the anti-reflection coating, the type of optics, and the geometrical as well as mechanical and structural properties of the EC setup. This was done by assembling three very different EC setups and comparing and discussing their performance, as well as advantages and disadvantages for different purposes using mainly QCLs from the same original wafer for better comparability. For the last part of this thesis, a new type of EC-QCL configuration was developed with properties so promising that we believe it has the potential to replace the Littrow Cavity in the long term. This is an alignment-stabilized and interference filter-tuned design using a retroreflector as the external reflector. For the demonstration of this concept, development of the tuning element in the form of an angle-tunable high-Q mid-infrared bandpass filter was necessary. For the design of the filter, materials with very strict tolerances on the physical and optical properties were selected from theoretical considerations and a fabrication method with highly optimized process parameters was developed. The first filters on the basis of yttrium fluoride/yttrium oxide/germanium/silicon have a transmission bandwidth of 0.14% of the central wavelength and a peak transmission of approximately 60%. The EC configuration resulted in a sensitivity reduction to mechanical perturbations of the reflector by two orders of magnitude, with a calculated potential for three orders of magnitude using optimized optics. This design lifts the fundamental constraint on miniaturization imposed on the Littrow design that requires large beam diameters to ensure a small bandwidth of the Littrow grating.
Flores, Yuri Victorovich. "Mid-infrared quantum cascade lasers." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17224.
Full textTwo decades after their invention in 1994, quantum-cascade lasers (QCLs) become increasingly important in the global infrared optoelectronics market. Photoacoustic spectroscopy, environment monitoring, hot object simulation, and free-space communication systems are selected examples of the current and potential applications of QCLs. Record optical powers as large as 14 W and power-conversion efficiencies ranging between 15-35 % have been reported for MIR QCLs for temperatures 80-300 K. Further improvement of these characteristics depends not only of aspects as heat management and chip-packaging, but also on improving the active-region design to reduce several leakage channels of charge carriers. However, mechanisms through which leakage of charge carriers affects QCLs performance have not been thoroughly researched. A better understanding of the several (non-radiative) scattering mechanisms involved in carrier transport in QCLs is needed to design new structures and optimize their performance. This work provides a realistic description of charge carriers transport in QCLs. We discuss in particular carrier leakage from QCL quantum-well confined states into higher and lower states. The two main mechanisms for non-radiative intersubband scattering in MIR QCLs are electron-longitudinal-optical-phonon scattering and interface roughness-induced scattering. We present methods for the experimental determination of the leakage current in QCLs at and above laser threshold, which allowed us to estimate the sheet distributions of conduction band states and better understand the impact of temperature activated leakage on QCLs characteristics. We found that even at temperatures low enough to neglect ELO scattering, carriers leakage due to IFR becomes significant for devices operating at high electron temperatures. Altogether, this approach offers a straightforward method to analyze and troubleshoot new QCL active region designs and optimize their performance.
Topczewski, Joseph John. "Cascade cyclizations & the schweinfurthins." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2780.
Full textMamouridis, Valeria. "Trophic cascade modelling in bathyal ecosystems." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/403955.
Full textDiferentes aspectos del ecosistema batial han sido tratados con el objetivo final de investigar mecanismos de cascada trófica impulsados por la pesca, un fenómeno que en estos sistemas nunca ha sido estudiado. Esto fue ejemplificado con el estudio del talud continental de fondo suave frente Cataluña (Mediterráneo noroccidental), donde se lleva a cabo la pesquería de la gamba roja Aristeus antennatus. En la Parte I se ha estudiado la composición de la infauna dentro del cañón y en el talud adyacente, y se ha relacionado con variables ambientales, que se pueden reconducir a tres causas principales (la producción primaria, el flujo desde ríos y a la aparición de las Aguas Intermedias de Levante). El cañón fue más influenciado por las estaciones y la provisión terrígena, contrariamente, el talud abierto resultó ser más estable y relacionado con la producciónn primaria. El cañón mostró variabilidad en las biomasas, en la composición taxonómica y en los principales hábitos tróficos, mientras que el talud adyacente estaba dominado por detritívoros de detríto refractario y en febrero por carnivoros que se alimenta de foraminiferos. Este estudio fue obligatorio para desarrollar los modelos en la Parte III. La Parte II se refiere a un estudio de los desembarques por unidad de esfuerzo (LPUE) de A. antennatus realizado a través de análisis de regresión frecuentistas y bayesianas. La variabilidad explicada por un total de seis predictores capturó el 43% de la variabilidad total del LPUE. Las variables relacionadas con la pesca (los viajes diarios realizados por los barquos el tonelaje de registro bruto y los barcos mismos como factor) fueron la fuente más importante, con una devianza explicada (DE) de 20.58%, seguido de variables temporales (DE=13.12%) y económicas (el precio de la gamba, DE=9.30%). Los datos derivados de la pesca, así como lo datos independientes de ella, devuelven índices similares para esta especie. También encontramos que puede ser apropiado reducir el límite de la cantidad de viajes al mes a un umbral definido por el modelo para una gestión razonable del recurso. Por último, se demostró que los modelos de efectos mixtos permiten evitar dificultades en la estimación cuando los datos temporales estan correlados y que si los barcos son de efecto aleatorio, no son útiles para fines de normalización. La parte III cubre el enfoque ecosistémico de esta tesis. Un total de 40 flujos de carbono entre 7 compartimentos internos y 6 externos, fueron reconstruidos utilizando modelación lineal inversa (LIM). El flujo total de C a la comunidad fue 2.62 mmol C m-2 d-1, entrando como materia orgánica vertical (5.2E-03 mmol C m-2 d-1) o por trasporte advectivo (2.6 mmol C m-2 d-1). Después, ese flujo se repartió entre la deposición (87.05%) y el alimentación por suspención (12.95%), sobre todo por parte del macrobentos (95.74%). El destino del C depositado fue en parte la ingestión por los metazoos (36.34%). El resto fue utilizado por los procariotas (y nemátodos) (69.28%) o atrapado en el sedimento (32.19%). La respiración total fue de 1.89 mmol C m-2 d-1, por la mayoría debido a procariotas y meiofauna (83.75%). La simulación dinámica se basa en un sistema de ecuaciones diferenciales ordinarias para predecir las tendencias de biomasa durante 5 años después de las perturbaciones inducidas por la pesca de la gamba (proceso top-down) y por las limitaciones de alimento primario (proceso bottom-up). Sólo encontramos efectos muy efímeros inducidas por la pesca, que persisten menos de 10 días, y que no se consideraron suficientes para demostrar la ocurrencia de cascadas tróficas. Por el contrario hemos encontrado efectos impulsado por la fuente de energía. Explicamos estos resultados con la importante función del detrito de orígen allóctono, y hipotetizamos que el detrito es el componente que controla la dinámica de la red trófica batial, un mecanismo conocido como control de los donantes.
Clarke, Daniel William. "The pathogenic cascade of Acanthamoeba Keratitis." Access to abstract only; dissertation is embargoed until after 5/15/2007, 2006. http://www4.utsouthwestern.edu/library/ETD/etdDetails.cfm?etdID=153.
Full textPocock, Ian. "Novel cascade aryne-capture/rearrangement reactions." Thesis, University of Huddersfield, 2014. http://eprints.hud.ac.uk/id/eprint/23743/.
Full textKarrakchou, Meryem. "Authentification et cascade: Définitions, mécanismes, recommandations." Doctoral thesis, Universite Libre de Bruxelles, 1993. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212858.
Full textBolton, Alan Graham. "Digital filters and cascade control compensators /." Title page, contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phb694.pdf.
Full textSaucier, Antoine. "Cascade processes and fully developed turbulence." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74674.
Full textGallego, Juan. "Fragmentation in the cascade - Vlasov approach." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61869.
Full textMartinez-Botas, R. F. "Annular cascade aerodynamics and heat transfer." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336114.
Full textPovey, ji Thomas. "On advances in annular cascade techniques." Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289124.
Full textHay, Kenneth Gillespie. "Gas sensing using quantum cascade lasers." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12766.
Full textHoughton, M. "Gain in terahertz quantum cascade lasers." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604257.
Full textHinsley, Joanne. "Novel palladium catalysts and cascade processes." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400177.
Full textMcCaffrey, Shaun. "Enantioselective Pd/In bimetallic cascade processes." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432336.
Full textDemircan, Aydin. "Cascade reactions involving a furan core." Thesis, University of Sussex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297561.
Full textKumar, Sushil Ph D. Massachusetts Institute of Technology. "Development of terahertz quantum-cascade lasers." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40501.
Full textIncludes bibliographical references (p. 321-340).
The terahertz or the far-infrared frequency range of the electromagnetic spectrum ( ... ) has historically been technologically underdeveloped despite having many potential applications, primarily due to lack of suitable sources of coherent radiation. Following on the remarkable development of mid-infrared ( ... ) quantum-cascade lasers (QCLs) in the past decade, this thesis describes the development of electrically-pumped terahertz quantum-cascade lasers in GaAs/AlsGal_.As heterostructures that span a spectral range of 1.59 - 5.0 THz ( ... ). A quantum-cascade laser (QCL) emits photons due to electronic intersubband transitions in the quantum-wells of a semiconductor heterostructure. The operation of terahertz QCLs at frequencies below the Reststrahlen band in the semiconductor ( ... ), is significantly more challenging as compared to that of the mid-infrared QCLs. Firstly, due to small energy separation between the laser levels various intersubband scattering mechanisms are activated, which make it difficult to selectively depopulate the lower laser level. Additionally, as electrons gain enough kinetic energy in the upper laser level thermally activated longitudinal-optical (LO) phonon scattering reduces the level lifetime and makes it difficult to sustain population inversion at higher temperatures.
(cont.) Secondly, waveguide design for terahertz mode confinement is also more challenging due to higher free-carrier losses in the semiconducting doped regions at the terahertz frequencies. For successful designs reported in this work, the lower radiative state depopulation is achieved by a combination of resonant-tunneling and fast LO phonon scattering, which allow robust operation even at relatively high temperatures. An equally important enabling mechanism for these lasers is the development of metal-metal waveguides, which provide low waveguides losses, and strong mode confinement due to subwavelength mode localization in the vertical dimension. With these techniques some record performances for terahertz QCLs are demonstrated including the highest pulsed operating temperature of 169 K, the highest continuous-wave (cw) operating temperature of 117 K, and the highest optical power output (248 mW in pulsed and 138 mW in cw at 5 K) for any terahertz QCL. Towards the bigger goal of realizing a 1-THz solid-state laser to ultimately bridge the gap between electronic and optical sources of electromagnetic radiation, QCLs with a unique one-well injection scheme, which minimizes intersubband absorption losses that occur at longer wavelengths, are developed.
(cont.) Based on this scheme a QCL operating at 1.59 THz (A - 189 ym) is realized, which is amongst the lowest frequency solid-state lasers that operate without the assistance of a magnetic field. This thesis also reports on the development of distributed-feedback lasers in metal-metal waveguides to obtain single-mode operation, with greater output power and better beam quality. The subwavelength vertical dimension in these waveguides leads to a strongly coupled DFB action and a large reflection from the end-facets, and thus conventional coupled-mode theory is not directly applicable to the DFB design. A design technique with precise control of phase of reflection at the end-facets is developed with the aid of finite-element analysis, and with some additional unique design and fabrication methods, robust DFB operation has been obtained. Single-mode surface-emitting terahertz QCLs operating up to - 150 K are demonstrated, with different grating devices spanning a range of approximately 0.35 THz around v - 3 THz using the same gain medium. A single-lobed far-field radiation pattern, higher output power due to surface-emission, and a relatively small degradation in temperature performance compared to the Fabry-Perot ridge lasers makes these DFB lasers well suited for practical applications that are being targeted by the terahertz quantum-cascade lasers.
by Sushil Kumar.
Ph.D.
Han, Ningren. "Electrically tunable terahertz quantum cascade lasers." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84723.
Full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 113-118).
In this thesis, microelectromechanical systems (MEMS) assisted electrically tunable terahertz quantum cascade lasers (THz QCLs) are designed and demonstrated. Two MEMS tuner devices are proposed to achieve electrically tunable THz QCLs. One is the electrostatic comb drive actuated tuner design and the other one is a two-stage flexure design that is actuated by an external piezo nano-positioning actuator. The MEMS tuner devices are all fabricated using standard foundry process SOIMUMPs from MEMSCAP Inc. with some additional in-house post-processings. First order distributed-feedback (DFB) THz wire QCLs with robust mode selectors are designed and fabricated at the MIT Microsystems Technology Laboratories (MTL) using processes developed at our group. By integrating the MEMS tuner chips with the THz QCL chips, broadband electrically tunable THz QCLs are successfully demonstrated. This thesis work provides an important step towards realizing turn-key tunable THz coherent sources for a variety of applications such as THz spectroscopy and THz coherent tomography.
by Ningren Han.
S.M.
Worrall, Christopher Henry. "Long wavelength Terahertz quantum cascade lasers." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612926.
Full textDongmo, Guy Blaise. "Rank matrix cascade algorithm, hermite interpolation." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/853.
Full textENGLISH ABSTRACT: (Math symbols have changed) Wavelet and subdivision techniques have developed, over the last two decades, into powerful mathematical tools, for example in signal analysis and geometric modelling. Both wavelet and subdivision analysis are based on the concept of a matrix–refinable function, i.e. a finitely supported matrix function which is self-replicating in the sense that it can be expressed as a linear combination of the integer shifts of its own dilation with factor 2: F = TAF = å k∈Z F(2 ・ −k)Ak. The coefficients Ak, k ∈ Z of d × d matrices, of this linear combination constitute the so-called matrix- mask sequence. Wavelets are in fact constructed as a specific linear combination of the integer shifts of the 2-dilation of a matrix- refinable function cf. [2; 9], whereas the convergence of the associated matrix- subdivision scheme c0 = c, cr+1 = SAcr, r ∈ Z+, SA : c = (ck : k ∈ Z) 7→ SAc = å ℓ∈Z Ak−2ℓ cℓ : k ∈ Z ! , subject to the necessary condition that rank := dim \ ǫ∈{0,1} n y ∈ Rd : Qǫy = y o > 0, Qǫ := å j∈Z Aǫ+2j, ǫ ∈ {0, 1}, ( cf. [26]) , implies the existence of a finitely supported matrix- function which is refinable with respect to the mask coefficients defining the refinement equation and the subdivision scheme. Throughout this thesis, we investigate in time–domain for a given matrix mask sequence, the related issues of the existence of a matrix–refinable function and the convergence of the corresponding matrix– cascade algorithm, and finally we apply some results to the particular research area of Hermite interpolatory subdivision schemes. The dissertation is organized as follows: In order to provide a certain flexibility or freedom over the project, we established in Chapter 1 the equivalence relation between the matrix cascade algorithm and the matrix subdivision scheme, subject to a well defined class of initial iterates. Despite the general noncommutativity of matrices, we make use in the full rank case Qǫ = I, ǫ ∈ {0, 1}, of a symbol factorization, to develop in Chapter 2 some useful tools, yielding a convergence result which comes as close to the scalar case as possible: we obtained a concrete sufficient condition on the mask sequence based on the matrix version of the generating function introduced in [3, page 22] for existence and convergence. Whilst the conjecture on nonnegative masks was confirmed in 2005 by Zhou [29], our result on scalar case provided a progress for general mask sequences. We then applied to obtain a new one-parameter family of refinable functions which includes the cardinal splines as a special case, as well as corresponding convergent subdivision schemes. With the view to broaden the class of convergent matrix-masks, we replaced in chapter 3 the full rank condition by the rank one condition Qǫu = u, ǫ ∈ {0, 1}, u := (1, . . . , 1)T, then improved the paper by Dubuc and Merrien [13] by using the theory of rank subdivision schemes by Micchelli and Sauer [25; 26], and end up this improvement with a generalization of [13, Theorem 13, p.8] in to the context of rank subdivision schemes. In Chapter 4, we translated the concrete convergence criteria of the general theory from Theorem 3.2, based on the r-norming factor introduced in [13, Definition 6, p.6], into the context of rank, factorization and spectral radius (cf. [26]), and presented a careful analysis of the relationship between the two concepts. We then proceed with generalizations and improvements: we classified the matrix cascade algorithms in term of rank = 1, 2, . . . , d, and provided a complete characterization of each class with the use of a more general r−norming factor namely τ(r)-norming factor. On the other hand, we presented numerical methods to determine, if possible, the convergence of each class of matrix cascade algorithms. In both the scalar and matrix cases above, we also obtained explicitly the geometric constant appearing in the estimate for the geometric convergence of thematrix-cascade algorithm iterates to the matrix- refinable function. This same geometric convergence rate therefore also holds true for the corresponding matrix–cascade algorithm. Finally, in Chapter 5, we apply the theory and algorithms developed in Chapter 4 to the particular research area of Hermite interpolatory subdivision schemes: we provided a new convergence criterium, and end up with new convergence ranges of the parameters’ values of the famous Hermite interpolatory subdivision scheme with two parameters, due to Merrien [23].
AFRIKAANSE OPSOMMING :(Wiskundige simbole het verander) Golfie en subdivisietegnieke het oor die afgelope twee dekades ontwikkel in kragtige wiskundige gereedskap, byvoorbeeld in seinanalise en geometriesemodellering. Beide golfie en subdivisie analise is gebaseer op die konsep van ’n matriks-verfynbare funksie; oftewel ’n eindig-ondersteunde matriksfunksie F wat selfreproduserend is in die sin dat dit uitgedruk kan word as ’n lineêre kombinasie van die heelgetalskuiwe van F se eie dilasie met faktor 2: F = Σ F(2 · −α)A(α), met A(α), α ∈ Z, wat aandui die sogenaamde matriks-masker ry. Golfies kan dan gekonstrueer word as ’n spesifieke lineêre kombinasie van die funksie ry {F(2 · −α) : α ∈ Z} (sien [2; 9]), terwyl die konvergensie van die ooreenstemmende matriks-subdivisie skema cº = c, cr+1 =(Σ β∈Z A(α − 2β) cr(β) : α ∈ Z ! , r ∈ Z+, onderhewig aan die nodige voorwaarde dat rank := dim \ ǫ∈{0,1} n y ∈ Rd : Qǫy = y o > 0, Qǫ := å α∈Z A(ǫ + 2α), ǫ ∈ {0, 1}, (sien [27]) die bestaan impliseer van ’n eindig-ondersteunde matriksfunksie F wat verfynbaar ismet betrekking tot diemaskerko¨effisi¨entewat die subdivisieskema definieer, en in terme waarvan die limietfunksie F van die subdivisieskema uitgedruk kan word as F = å α∈Z F(· − α)c(α). Ons hoofdoel hier is om , in die tydgebied, en vir ’n gegewematriks-masker ry, die verwante kwessies van die bestaan van ’nmatriks-verfynbare funksie en die konvergensie van die ooreenstemmende matriks-kaskade algoritme, en matriks-subdivisieskema, te ondersoek, en om uiteindelik sommige van ons resultate toe te pas op die spesifieke kwessie van die konvergensie van Hermite interpolerende subdivisieskemas. Summary v Eerstens, in Hoofstuk 1, ondersoek ons die verwantskap tussen matriks-kaskade algoritmes en matriks-subdivisie skemas, met verwysing na ’n goedgedefinieerde klas van begin-iterate. Vervolgens beskou ons die volle rang geval Qǫ = I, ǫ ∈ {0, 1}, om, in Hoofstuk 2, nuttige gereedskap te ontwikkel, en wat daarby ’n konvergensie resultaat met ’n sterk konneksie ten opsigte van die skalaar-geval oplewer. Met die doelstelling om ons klas van konvergente matriks-maskers te verbreed, vervang ons, in Hoofstuk 3, die volle rang voorwaarde met die rang een voorwaarde Qǫu = u, ǫ ∈ {0, 1}, u := (1, . . . , 1)T, en verkry ons dan ’n verbetering op ’n konvergensieresultaat in die artikel [14] deur Dubuc en Merrien, deur gebruik te maak van die teorie van rang subdivisieskemas van Micchelli en Sauer [26; 27], waarna ons die resultaat [14, Stelling 13, page 8] na die konteks van rang subdivisieskemas veralgemeen. InHoofstuk 4 herlei ons die konkrete konvergensie kriteria van Stelling 3.2, soos gebaseer op die r-normerende faktor gedefinieer in [14, Definisie 6, page 6] , na die konteks van rang, faktorisering en spektraalradius (sien [27]), en gee ons ’n streng analise van die verwantskap tussen die twee konsepte. Verder stel ons dan bekend ’n nuwe klassifikasie van matriks-kaskade algoritmes ten opsigte van rang, en verskaf ons ’n volledige karakterisering van elke klasmet behulp van ’nmeer algemene r-normerende faktor, nl. die τ(r)-normerende faktor. Daarby gee ons doeltreffende numeriesemetodes vir die implementering van ons teoretiese resultate. Ons verkry ook eksplisiet die geometriese konstante wat voorkom in die afskatting van die geometriese konvergensie van die matriks-kaskade algoritme iterate na die matriks-verfynbare funksie. Ten slotte, in Hoofstuk 5, pas ons die teorie en algoritmes ontwikkel in Hoofstuk 4 toe om die konvergensie van Hermite-interpolerende subdivisieskemas te analiseer. Spesifiek lei ons ’n nuwe konvergensie kriterium af, wat ons dan toepas om nuwe konvergensie gebiede vir die parameter waardes te verkry vir die beroemde Hermite interpolerende subdivisieskema met twee parameters, soos toegeskryf aan Merrien [24].
Wallace, Stephen. "A cascade approach towards the gephyrotoxins." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:1f7b55ec-0346-498c-be03-81f3b9fde2f5.
Full textLingard, Hannah. "Cascade approaches to decahydroquinoline ring systems." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:e0ff1123-eae7-47aa-b377-1a12346d2538.
Full textGambari, Johannes. "Nonlinear effects in quantum cascade lasers." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7824.
Full textNackley, Brittany B. "Temporal Dynamics of the Defense Cascade." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99987.
Full textM.S.
The more we understand about how people’s bodies and their energies act when they feel threatened, the better we can find help for folks who struggle with anxiety, trauma or other challenging conditions. This research uses a theoretical model called the defense cascade to explore how people respond mentally and physically to threatening situations. Nineteen undergraduates went through a virtual reality (VR) experience that was designed to feel threatening while their body and its energy systems were measured. A scale was introduced called the Subjective Units of Distress Scale (SUDS) and was used to help the researchers understand how distressed people felt while they were in the VR experience. Averaged SUDS reports suggested that the VR stimulus was experienced as threatening for most participants, but their body response patterns did not fit those predicted by the defense cascade. Participants whose questionnaire responses suggested they were not anxiety-prone or traumatized, tended to show bodily activation that uncoupled their two autonomic bodily systems during a baseline period before the threatening stimulus. However, their autonomic responses during the stimulus period varied. Nearly all participants showed either both autonomic systems acting together or only one system acting in a mutually exclusive way to the other system during the stimulus period. This was the case for most participants except those reporting the most trauma involving dissociative experiences. This latter group mostly showed uncoupled autonomic bodily patterns.
Vieira, Emanuel Sousa. "Cascade processes in directed complex networks." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/23482.
Full textIn this thesis we study analytically and numerically the bootstrap percolation process in random uncorrelated directed complex networks. We formulate and analyze the bootstrap percolation process on both unweighted and weighted networks and also study a probability based percolation process. The considered percolation process has an associated activation threshold k where a node only gets active if it has at least k active neighboring nodes. We compare our results with analytical and numerical results obtained for undirected complex networks. We also analyze how topological properties of the directed network components, such as the giant strongly connected component and the periphery, influence on the bootstrap percolation process. We apply our theoretical approach for studying the bootstrap percolation on real complex networks. We show that our theoretical approach developed for the case of random uncorrelated directed networks is in a good agreement with numerical simulations of the bootstrap percolation process on real complex networks which actually are correlated and clustered.
Nesta tese estudamos analiticamente e numericamente o processo de bootstrap percolation em redes complexas direcionadas. Formulamos e analisamos o processo de bootstrap percolation em ambas redes com pesos e sem pesos e também estudamos um processo de bootstrap percolation baseado em probabilidades. O processo de bootstrap percolation considerado tem um parâmetro de ativação associado k onde um nó é ativado se tiver pelo menos k nó vizinhos ativos. Comparamos os nossos resultados com resultados analíticos e numéricos obtidos para redes complexas não direcionadas. Analisamos também como as propriedades topológicas dos componentes das redes complexas direcionadas, como o giant strongly connected component e a periferia, influenciam o processo de bootstrap percolation. Aplicamos a nossa teoria no estudo do processo de bootstrap percolation em redes complexas reais. Mostramos que a nossa teoria desenvolvida para redes complexas aleatórias e não correlacionadas está em bom acordo com simulações numéricas do processo de bootstrap percolation em redes complexas reais que são correlacionas e agrupadas.
Birch, Peter. "Synthetic cascade sequences initiated by organoboranes." Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/2798/.
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