Дисертації з теми "Pulse operation"
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1
Werner, Steven P. "Initiator diffraction limits for pulse detonation engine operation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02Dec%5FWerner.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2002.Thesis advisor(s): Christopher M. Brophy, Jose O. Sinibaldi. Includes bibliographical references (p. 45-47). Also available online.
2
Casper, Lars Christian. "On the operation of a long-pulse KrCl excimer laser." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57863.
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3
Vanapalli, Srinivas. "High-frequency operation and miniaturization aspects of pulse-tube cryocoolers." Enschede : University of Twente [Host], 2008. http://doc.utwente.nl/58862.
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4
Tang, Jing-Min. "An experimental investigation of the operation of a Helmholz pulse combustor." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/12008.
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5
Rasmeni, Sibusiso Wiseman. "Simulation of the switched reluctance machine under single pulse mode operation." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53590.
Повний текст джерелаАнотація:
Thesis (MScEng)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: Two distinct simulation methods have been developed to simulate the single and the multi-phase excited current waveforms of the switched reluctance machine (SRM) under single pulse mode operation. These simulation methods are explained and evaluated in this thesis. A non-commercial finite element package that takes the SRM's nonlinear magnetic property into account is used in this regard. The simulation program uses the finite element solution directly during the simulation. Both simulation methods have been investigated in terms of result and total simulation time. In this investigation it is shown how feasible the simulation methods will be with the next generation of fast computers. The factors affecting the simulated current waveforms of the SRM under single pulse mode operation are investigated in detail in this thesis. With these factors taken into account, the measured and simulated multi-phase current waveforms are compared with each other and discussed.
AFRIKAANSE OPSOMMING: Twee verskillende simulasie metodes is ontwikkel om die enkel- en multi-fase stroomgolfvorms van die geskakelde reluktansiemasjien (GRM) onder enkelpulsmodus-werking te simuleer. In hierdie tesis word hierdie simulasie metodes verduidelik en geëvalueer. 'n Nie-kommersiële eindige element pakket wat die nielinieêre magnetiese eienskap van die GRM in ag neem is in hierdie verband gebruik. Die simulasie program gebruik die eindige-element oplossing direk gedurende die simulasie. Beide simulasie metodes is ondersoek in terme van resultaat en simulasietyd. In hierdie ondersoek word getoon hoe uitvoerbaar hierdie tipe simulasie metodes gaan wees met die volgende hoë spoed generasie rekenaars. Die faktore wat die gesimuleerde stroomgolfvorms van die GRM onder enkelpulsmodus-werking beïnvloed word deeglik in hierdie tesis ondersoek. Met hierdie faktore in ag geneem word die gemete en gesimuleerde multi-fase stroomgolfvorms met mekaar vergelyk en bespreek.
6
Matos, Antonio P. "Characterization and application of four-layer semiconductor structures in pulse mode operation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FMatos.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Physics)--Naval Postgraduate School, September 2006.Thesis Advisor(s): Gamani Karunasiri, James H. Luscombe. "September 2006." Includes bibliographical references (p. 69-70). Also available in print.
7
Cirineo, Tony. "Doppler Video Signal Conditioning, Theory of Operation." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/611417.
Повний текст джерелаАнотація:
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThis paper describes some of the signal conditioning and processing circuits that were developed to reconstruct the doppler video signal from a radar receiver under test. The reconstructed doppler video signal is then digitized and put into a telemetry frame for transmission to a ground receiving station.
8
Lin, Jiunn-Yuan. "Optimisation of multi-pulse pumping for collisional excitation X-ray lasers." Thesis, University of Essex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265028.
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9
Atkinson, Terry. "Modeling of magnetic optic for the short pulse mode operation of Energy Recovery Linac based light sources." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17300.
Повний текст джерелаАнотація:
Das Forschungsfeld der Synchrotronstrahlungsquellen hat sich in den letzen Jahren entscheidend weiterentwickelt. Alle Zukunftsideen, unabhängig von ihrer Komplexität, haben dennoch eines gemeinsam: die Erzeugung kurzer Pulse. Die Naturwissenschaften haben die Spitzenbrillanz, die mit Hilfe kürzester Pulse produziert werden kann, als neues Schlüsselwerkzeug entdeckt. Die Nutzergemeinschaft verlangt nicht mehr nur ein statisches Bild, sondern vielmehr eine Reihe von bewegten Aufnahmen atomarer Substrukturen und den dazugehöringen Prozessen. Existierende dritte Generation Synchrotronstrahlungsquellen werden an die neuen Herausforderungen angepasst: Verbesserungen an der Magnet-Optik sowie der Einbau modernster Beschleunigertechnologie ermöglichen die Erzeugung kürzester Pulse mit höchster Brillanz für zeitaufgelöste Experimente. Ein möglicher Kandidat für die Lichtquelle der nächsten Generation ist ein Linear-Beschleuniger mit Energierückgewinnung. Durch die Verwendung langer Beschleunigungsstrukturen kann es, selbst bei hohen Energien, nicht zur Ausbildung des Emittanzgleichgewichts wie in Speicherringen kommen. Durch die Verwendung Impulsabhängiger-Umlaufbahnen und der Rückgewinnung der Strahlenergie ist es mit `Energy Recovery Linac'' (ERL)-basierten Quellen energieeffizient möglich, hochenergetische Elektronen-Pulse im Femtosekundenbereich zu erzeugen. Die longitudinale Elekronstrahldynamik solcher ERLs ist eines der Hauptthemen dieser Arbeit. Umfangreiche Simulationen über die gesamte Maschine wurden im Rahmen der `Femto-Science Factory'' Lichtquellen Studie durchgeführt. Die Begrenzungen des Kurzpulsmodus Betriebes wurden untersucht und mit den Erwartungen verglichen. Besondere Aufmerksamkeit lag dabei auf den 6D Elektronenstrahleigenschaften, insbesondere auf der Vermeidung von Strahlaufweitungen, die mit der Erzeugung von Ultra-Kurzpulsen einhergehen können.Synchrotron light sources are entering a new era. No matter how elaborate, all the next generation proposals share a common necessity; the production of ultra-short electron bunches. There is an evolution in the field of science under investigation using the high peak brilliance generated from such bunches. The user community is demanding not just pictures but videos of atomic substructures and the processes that define them. Existing 3rd generation facilities are modifying their magnetic lattices and upgrading the acceleration schemes in order to keep up with this trend of generating short pulses with ultimate brilliance for time resolved experiments. A possible candidate for the next generation light source is one based on ERL technology. Using long linacs to accelerate to high energies overcomes the present limitation of emittance equilibrium in storage rings. By implementing independent arcs for acceleration and deceleration while recuperating the beams energy, ERL based sources are theoretically capable of efficiently producing high energy femtosecond long bunch lengths. The study of the longitudinal motion of the beam through single pass magnetic optic in combination with linacs is the main topic of this thesis. Dedicated start-to-end simulations in the framework of the Femto-Science Factory large scale light source are undertaken. The expectations and restrictions on the short pulse mode (SPM) operation are comprehensively examined in this work. Particular attention is given to the 6D electron beam properties and with it the beam degradation caused by the production of ultra-short bunches.
10
Sims, Robert. "Development of Thulium Fiber Lasers for High Average Power and High Peak Power Operation." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5706.
Повний текст джерелаАнотація:
High power thulium fiber lasers are useful for a number of applications in both continuous-wave and pulsed operating regimes. The use of thulium as a dopant has recently gained interest due to its large bandwidth, possibility of high efficiency, possibility of high power and long wavelength ~1.8 – 2.1 [micro]m. The longer emission wavelength of Tm-doped fiber lasers compared to Yb- and/or Er-doped fiber lasers creates the possibility for higher peak power operation due to the larger nonlinear thresholds and reduced nonlinear phase accumulation. One primary interest in Tm-doped fiber lasers has been to scale to high average powers; however, the thermal and mechanical constraints of the fiber limit the average power out of a single-fiber aperture. One method to overcome the constraints of a single laser aperture is to spectrally combine the output from multiple lasers operating with different wavelengths into a single beam. In this thesis, results will be presented on the development of three polarized 100 W level laser systems that were wavelength stabilized for SBC. In addition to the development of the laser channels, the beams were combined using bandpass filters to achieve a single near diffraction-limited output. Concurrently, with the development of high average power systems there is an increasing interest in femotosecond pulse generation and amplification using Tm- doped fiber lasers. High peak power sources operating near 2 [micro]m have the potential to be efficient pump sources to generate mid-infrared light through supercontinuum generation or optical parametric oscillators. This thesis focuses on the development of a laser system utilizing chirped pulse amplification (CPA) to achieve record level energies and peak powers for ultrashort pulses in Tm-doped fiber. A mode-locked oscillator was built to generate femtosecond pulses operating with pJ energy. Pulses generated in the mode-locked oscillator were limited to low energies and contained spectral modulation due to the mode-locking mechanism, therefore, a Raman-soliton self-frequency shift (Raman-SSFS) amplifier was built to amplify pulses, decrease the pulse duration, and spectrally clean pulses. These pulses were amplified using chirped pulse amplification (CPA) in which, limiting factors for amplification were examined and a high peak power system was built. The primary limiting factors of CPA in fibers include the nonlinear phase accumulation, primarily through self-phase modulation (SPM), and gain narrowing. Gain narrowing was examined by temporally stretching pulses in a highly nonlinear fiber that both stretched the pulse duration and broadened the spectrum. A high peak power CPA system amplified pulses to 1 [micro]J energy with 300 fs compressed pulses, corresponding to a peak power >3 MW. High peak power pulses were coupled into highly nonlinear fibers to generate supercontinuum.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics
11
Steiniger, Klaus. "High-Yield Optical Undulators Scalable to Optical Free-Electron Laser Operation by Traveling-Wave Thomson-Scattering." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-234847.
Повний текст джерелаАнотація:
All across physics research, incoherent and coherent light sources are extensively utilized. Especially highly brilliant X-ray sources such as third generation synchrotrons or free-electron lasers have become an invaluable tool enabling experimental techniques that are unique to these kinds of light sources. But these sources have developed to large scale facilities and a demand in compact laboratory scale sources providing radiation of similar quality arises nowadays. This thesis focuses on Traveling-Wave Thomson-Scattering (TWTS) which allows for the realization of ultra-compact, inherently synchronized and highly brilliant light sources. The TWTS geometry provides optical undulators, through which electrons pass and thereby emit radiation, with hundreds to thousands of undulator periods by utilizing pulse-front tilted lasers pulses from high peak-power laser systems. TWTS can realize incoherent radiation sources with orders of magnitude higher photon yield than established head-on Thomson sources. Moreover, optical free-electron lasers (OFELs) can be realized with TWTS if state-of-the-art technology in electron accelerators and laser systems is utilized. Tilting the laser pulse front with respect to the wavefront by half of this interaction angle optimizes electron and laser pulse overlap by compensating the spatial offset between electrons and the laser pulse-front at the beginning of the interaction when the electrons are far from the laser pulse axis. The laser pulse-front tilt ensures continuous overlap between electrons and laser pulse while the electrons cross the laser pulse cross-sectional area. Thus the interaction distance can be controlled in TWTS by the laser pulse width rather than laser pulse duration. Utilizing wide, petawatt class laser pulses allows realizing thousands of optical undulator periods. This thesis will show that TWTS OFELs emitting ultraviolet radiation are realizable today with existing technology for electron accelerators and laser systems. The requirements on electron bunch and laser pulse quality of these ultraviolet TWTS OFELs are discussed in detail as well as the corresponding requirements of TWTS OFELs emitting in the soft and hard X-ray range. These requirements are derived from scaling laws which stem from a self-consistent analytic description of the electron bunch and radiation field dynamics in TWTS OFELs presented within this thesis. It is shown that these dynamics in TWTS OFELs are qualitatively equivalent to the electron bunch and radiation field dynamics of standard free-electron lasers which analytically proves the applicability of TWTS for the realization of an optical free-electron laser. Furthermore, experimental setup strategies to generate the pulse-front tilted TWTS laser pulses are presented and designs of experimental setups for the above examples are discussed. The presented setup strategies provide dispersion compensation, required due to angular dispersion of the laser pulse, which is especially relevant when building compact, high-yield hard X-ray TWTS sources in large interaction angle setups. An example of such an enhanced Thomson source by TWTS, which provides orders of magnitude higher spectral photon density than a comparable head-on interaction geometry, is presented, tooInkohärente und kohärente Lichtquellen werden in allen Feldern der physikalischen Forschung intensiv eingesetzt. Im Besonderen ermöglichen hoch-brilliante Röntgenquellen, wie Synchrotrone der dritten Generation und Freie-Elektronen Laser, einzigartige Experimentiertechniken wodurch diese zu unverzichtbaren Werkzeugen wurden. Sie sind allerdings auch im Umfang zu Großforschungseinrichtungen herangewachsen. Um den hohen Bedarf an hoch-brillianten Lichtquellen zu decken, besteht daher die Notwendigkeit neuartige und kompakte Quellen zu entwickeln welche auf dem Maßstab eines Labors realisierbar sind. Diese Dissertation widmet sich der Traveling-Wave Thomsonstreuung (TWTS) welche die Realisierung ultra-kompakter, intrinsisch synchronisierbarer und hoch-brillianter Röntgenquellen ermöglicht. TWTS ist eine Methode der Streuung von Laserpulsen an relativistischen Elektronen. Dabei durchquert ein Elektronenpuls mit nahezu Lichtgeschwindigkeit einen Laserpuls. Während der Durchquerung beginnen die Elektronen im Feld des Laserpulses zu oszillieren wobei sie Strahlung emittieren. Die ausgesandte Strahlung besitzt eine deutlich kürzere Wellenlänge als das Laserfeld aufgrund der hohen Elektronengeschwindigkeit und der damit verbundenen großen Dopplerverschiebung. Das besondere an TWTS ist, dass Elektronen- und Laserpropagationsrichtung einen Winkel einschließen sowie pulsfrontverkippte Hochleistungslaserpulse eingesetzt werden. Dadurch können um Größenordnungen längere Interaktionsdistanzen als in herkömmlichen frontalen Thomsonstreuungsanordnungen erreicht werden. TWTS ermöglicht dadurch die Realisierung optischer Freie-Elektronen Laser (OFEL) und inkohärenter Strahlungsquellen mit einer um Größenordnungen erhöhten Photonenausbeute gegenüber Thomsonstreuungsquellen in frontalen Interaktionsanordungen. Werden modernste Elektronenbeschleuniger und Lasersysteme genutzt, dann ist der Betrieb optischer Freie-Elektronen Laser bereits heute mit TWTS möglich. Das wird in der Dissertation am Beispiel eines Vakuumultraviolettstrahlung emittierenden TWTS OFEL gezeigt. Dessen Anforderungen an die Qualität der Elektronen- und Laserpulse werden im Detail in der Arbeit besprochen sowie weitere Beispiele weicher und harter Röntgenstrahlung emittierender TWTS OFEL präsentiert. Diese Anforderungen werden anhand von Skalierungsvorschriften ermittelt welche aus einer selbstkonsistenten, 1.5 dimensionalen Theorie zur Wechselwirkung zwischen Elektronen und Laserfeld in TWTS abgeleitet sind. Sowohl die Theorie zur Wechselwirkung als auch die Ableitung der Skalierungsvorschriften sind Teile dieser Dissertation. Eine wichtige Erkenntnis der Theorie ist die qualitative Äquivalenz von Elektronen- und Strahlungsfeldbewegungsgleichungen in TWTS zu denen herkömmlicher Freie-Elektronen Laser. Das beweist analytisch die Möglichkeit zur Realisierung eines OFEL mit TWTS. Einen weiteren wichtigen Teil dieser Dissertation bildet die Arbeit zur Generierung der Laserpulse mit verkippter Pulsfront. Optische Aufbauten zur Verkippung der Laserpulsfront werden vorgestellt und für einige der präsentierten TWTS OFEL ausführlich dargelegt. Die Aufbauten verkippen nicht nur die Laserpulsfront sondern gewähren gleichzeitig Kontrolle über die Laserpulsdispersionen. Dadurch kann während der gesamten Interaktionen eine ausreichend hohe Qualität des Laserfeldes sichergestellt werden, was für TWTS OFEL und inkohärente TWTS Lichtquellen mit großem Interaktionswinkel unbedingt notwendig ist. Ein Beispiel einer inkohärenten TWTS Lichtquelle wird ebenfalls präsentiert. Diese emittiert Strahlung mit einer um Größenordnungen höheren spektrale Photonendichte als eine herkömmliche Thomsonquelle in einer frontalen Streuanordnung mit vergleichbaren Laser- und Elektronenpulsen
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Klein-Heßling, Annegret Verfasser], Doncker Rik W. [Akademischer Betreuer] [De, and Volker [Akademischer Betreuer] Pickert. "Active DC-power filters for switched reluctance drives during single-pulse operation / Annegret Klein-Heßling ; Rik Wivina Anna de Doncker, Volker Pickert." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1187346535/34.
Повний текст джерела
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Klein-Heßling, Annegret [Verfasser], Doncker Rik W. [Akademischer Betreuer] De, and Volker [Akademischer Betreuer] Pickert. "Active DC-power filters for switched reluctance drives during single-pulse operation / Annegret Klein-Heßling ; Rik Wivina Anna de Doncker, Volker Pickert." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1187346535/34.
Повний текст джерела
14
Atkinson, Terry [Verfasser], Alexander [Akademischer Betreuer] Matveenko, Eberhard [Akademischer Betreuer] Jaeschke, and Kurt [Akademischer Betreuer] Aulenbacher. "Modeling of magnetic optic for theshort pulse mode operation of Energy Recovery Linac based light sources / Terry Atkinson. Gutachter: Alexander Matveenko ; Eberhard Jaeschke ; Kurt Aulenbacher." Berlin : Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://d-nb.info/1077244320/34.
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15
Chang, Wing Chien Christopher. "Operational characteristics of an SCR-based pulse generating circuit." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44535.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedA commercial off-the-shelf silicon controlled rectifier (SCR) was connected in series with a parallel RC load under DC bias to produce self-terminating voltage pulses. The physics underlying the switching mechanism of the SCR in such a circuit was investigated and the values of load resistance and capacitance varied to ascertain their role on the pulse-generating capability of the circuit. When pulsing was successfully achieved, a reverse recovery current was always present to return the SCR from its on state to its off state. In addition, the regenerative process responsible for turning the SCR is through the avalanche multiplication of charge carriers within the device. This appeared to be independent of the mode of triggering, either by increasing the DC bias or using a current at the gate. Significantly, pulsing was discovered to be sustainable for a specific range of RC values that depends on the SCR’s intrinsic turn-off time. Specifically, it was found that without making modifications to the SCR itself, the minimum dead time achievable between pulses was essentially the turn-off time of the SCR. The findings of the research will help to design optimum SCR-based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.
16
Frei, Bruno. "Diode laser-pumped neodymium lasers in pulsed and continuous wave operation /." [S.l : s.n.], 1993. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Zabihi, Sasan. "Flexible high voltage pulsed power supply for plasma applications." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48137/1/Sasan_Zabihi_Sheykhrajeh_Thesis.pdf.
Повний текст джерелаАнотація:
Demands for delivering high instantaneous power in a compressed form (pulse shape) have widely increased during recent decades. The flexible shapes with variable pulse specifications offered by pulsed power have made it a practical and effective supply method for an extensive range of applications. In particular, the release of basic subatomic particles (i.e. electron, proton and neutron) in an atom (ionization process) and the synthesizing of molecules to form ions or other molecules are among those reactions that necessitate large amount of instantaneous power. In addition to the decomposition process, there have recently been requests for pulsed power in other areas such as in the combination of molecules (i.e. fusion, material joining), gessoes radiations (i.e. electron beams, laser, and radar), explosions (i.e. concrete recycling), wastewater, exhausted gas, and material surface treatments. These pulses are widely employed in the silent discharge process in all types of materials (including gas, fluid and solid); in some cases, to form the plasma and consequently accelerate the associated process.
Due to this fast growing demand for pulsed power in industrial and environmental applications, the exigency of having more efficient and flexible pulse modulators is now receiving greater consideration. Sensitive applications, such as plasma fusion and laser guns also require more precisely produced repetitive pulses with a higher quality. Many research studies are being conducted in different areas that need a flexible pulse modulator to vary pulse features to investigate the influence of these variations on the application. In addition, there is the need to prevent the waste of a considerable amount of energy caused by the arc phenomena that frequently occur after the plasma process. The control over power flow during the supply process is a critical skill that enables the pulse supply to halt the supply process at any stage.
Different pulse modulators which utilise different accumulation techniques including Marx Generators (MG), Magnetic Pulse Compressors (MPC), Pulse Forming Networks (PFN) and Multistage Blumlein Lines (MBL) are currently employed to supply a wide range of applications. Gas/Magnetic switching technologies (such as spark gap and hydrogen thyratron) have conventionally been used as switching devices in pulse modulator structures because of their high voltage ratings and considerably low rising times. However, they also suffer from serious drawbacks such as, their low efficiency, reliability and repetition rate, and also their short life span. Being bulky, heavy and expensive are the other disadvantages associated with these devices. Recently developed solid-state switching technology is an appropriate substitution for these switching devices due to the benefits they bring to the pulse supplies. Besides being compact, efficient, reasonable and reliable, and having a long life span, their high frequency switching skill allows repetitive operation of pulsed power supply. The main concerns in using solid-state transistors are the voltage rating and the rising time of available switches that, in some cases, cannot satisfy the application’s requirements. However, there are several power electronics configurations and techniques that make solid-state utilisation feasible for high voltage pulse generation. Therefore, the design and development of novel methods and topologies with higher efficiency and flexibility for pulsed power generators have been considered as the main scope of this research work. This aim is pursued through several innovative proposals that can be classified under the following two principal objectives.
• To innovate and develop novel solid-state based topologies for pulsed power generation
• To improve available technologies that have the potential to accommodate solid-state technology by revising, reconfiguring and adjusting their structure and control algorithms.
The quest to distinguish novel topologies for a proper pulsed power production was begun with a deep and through review of conventional pulse generators and useful power electronics topologies. As a result of this study, it appears that efficiency and flexibility are the most significant demands of plasma applications that have not been met by state-of-the-art methods. Many solid-state based configurations were considered and simulated in order to evaluate their potential to be utilised in the pulsed power area. Parts of this literature review are documented in Chapter 1 of this thesis.
Current source topologies demonstrate valuable advantages in supplying the loads with capacitive characteristics such as plasma applications. To investigate the influence of switching transients associated with solid-state devices on rise time of pulses, simulation based studies have been undertaken. A variable current source is considered to pump different current levels to a capacitive load, and it was evident that dissimilar dv/dts are produced at the output. Thereby, transient effects on pulse rising time are denied regarding the evidence acquired from this examination. A detailed report of this study is given in Chapter 6 of this thesis.
This study inspired the design of a solid-state based topology that take advantage of both current and voltage sources. A series of switch-resistor-capacitor units at the output splits the produced voltage to lower levels, so it can be shared by the switches. A smart but complicated switching strategy is also designed to discharge the residual energy after each supply cycle. To prevent reverse power flow and to reduce the complexity of the control algorithm in this system, the resistors in common paths of units are substituted with diode rectifiers (switch-diode-capacitor). This modification not only gives the feasibility of stopping the load supply process to the supplier at any stage (and consequently saving energy), but also enables the converter to operate in a two-stroke mode with asymmetrical capacitors. The components’ determination and exchanging energy calculations are accomplished with respect to application specifications and demands. Both topologies were simply modelled and simulation studies have been carried out with the simplified models. Experimental assessments were also executed on implemented hardware and the approaches verified the initial analysis. Reports on details of both converters are thoroughly discussed in Chapters 2 and 3 of the thesis.
Conventional MGs have been recently modified to use solid-state transistors (i.e. Insulated gate bipolar transistors) instead of magnetic/gas switching devices. Resistive insulators previously used in their structures are substituted by diode rectifiers to adjust MGs for a proper voltage sharing. However, despite utilizing solid-state technology in MGs configurations, further design and control amendments can still be made to achieve an improved performance with fewer components. Considering a number of charging techniques, resonant phenomenon is adopted in a proposal to charge the capacitors. In addition to charging the capacitors at twice the input voltage, triggering switches at the moment at which the conducted current through switches is zero significantly reduces the switching losses. Another configuration is also introduced in this research for Marx topology based on commutation circuits that use a current source to charge the capacitors. According to this design, diode-capacitor units, each including two Marx stages, are connected in cascade through solid-state devices and aggregate the voltages across the capacitors to produce a high voltage pulse. The polarity of voltage across one capacitor in each unit is reversed in an intermediate mode by connecting the commutation circuit to the capacitor. The insulation of input side from load side is provided in this topology by disconnecting the load from the current source during the supply process. Furthermore, the number of required fast switching devices in both designs is reduced to half of the number used in a conventional MG; they are replaced with slower switches (such as Thyristors) that need simpler driving modules. In addition, the contributing switches in discharging paths are decreased to half; this decrease leads to a reduction in conduction losses. Associated models are simulated, and hardware tests are performed to verify the validity of proposed topologies. Chapters 4, 5 and 7 of the thesis present all relevant analysis and approaches according to these topologies.
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Melhem, Wissam. "Contribution à l'étude des onduleurs de tension à commutation douce destinés à le forte puissance." Cachan, Ecole normale supérieure, 1995. http://www.theses.fr/1995DENS0018.
Повний текст джерелаАнотація:
Le travail entrepris dans cette thèse permet d'analyser les possibilités de l'introduction de la commutation douce dans les onduleurs de tension a mli destines a la forte puissance. Une étude bibliographique conduit dans un premier temps à établir une classification des différentes structures proposées. L'analyse des avantages et inconvénients associes au fonctionnement de ces structures (contraintes, critères de fonctionnement en mli) nous amène à poursuivre notre étude sur deux structures de concepts différents: la première est qualifiée de structure a commutation mixte. Dans ce cas, l'instauration de la commutation douce est réalisée au niveau de chaque interrupteur élémentaire. Une étude approfondie de son fonctionnement a conduit a la mise en place d'une maquette expérimentale de forte puissance (1 kv, 1ka, 10 khz) qui a permis de justifier le recours a la commutation douce a travers des mesures comparatives avec la structure fonctionnant en commutation dure. La deuxième est qualifiée de structure à large ondulation. Dans ce cas, l'instauration de la commutation douce est assurée d'une façon commune à tous les bras de l'onduleur. Une modification du schéma de base de cette structure mène a optimiser ses conditions de fonctionnement. Une maquette expérimentale de moyenne puissance (500 v, 50 a, 20 khz) valide l'étude théorique. Un bilan des potentialités de cette technique de commutation clos notre rapport
19
Mohamed, Ahmed A. "Hybrid Power System Intelligent Operation and Protection Involving Distributed Architectures and Pulsed Loads." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/866.
Повний текст джерелаАнотація:
Efficient and reliable techniques for power delivery and utilization are needed to account for the increased penetration of renewable energy sources in electric power systems. Such methods are also required for current and future demands of plug-in electric vehicles and high-power electronic loads. Distributed control and optimal power network architectures will lead to viable solutions to the energy management issue with high level of reliability and security. This dissertation is aimed at developing and verifying new techniques for distributed control by deploying DC microgrids, involving distributed renewable generation and energy storage, through the operating AC power system.
To achieve the findings of this dissertation, an energy system architecture was developed involving AC and DC networks, both with distributed generations and demands. The various components of the DC microgrid were designed and built including DC-DC converters, voltage source inverters (VSI) and AC-DC rectifiers featuring novel designs developed by the candidate. New control techniques were developed and implemented to maximize the operating range of the power conditioning units used for integrating renewable energy into the DC bus. The control and operation of the DC microgrids in the hybrid AC/DC system involve intelligent energy management. Real-time energy management algorithms were developed and experimentally verified. These algorithms are based on intelligent decision-making elements along with an optimization process. This was aimed at enhancing the overall performance of the power system and mitigating the effect of heavy non-linear loads with variable intensity and duration. The developed algorithms were also used for managing the charging/discharging process of plug-in electric vehicle emulators.
The protection of the proposed hybrid AC/DC power system was studied. Fault analysis and protection scheme and coordination, in addition to ideas on how to retrofit currently available protection concepts and devices for AC systems in a DC network, were presented. A study was also conducted on the effect of changing the distribution architecture and distributing the storage assets on the various zones of the network on the system’s dynamic security and stability. A practical shipboard power system was studied as an example of a hybrid AC/DC power system involving pulsed loads. Generally, the proposed hybrid AC/DC power system, besides most of the ideas, controls and algorithms presented in this dissertation, were experimentally verified at the Smart Grid Testbed, Energy Systems Research Laboratory. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.
20
Ebrazeh, Ali. "An Energy-Efficient Impulse Radio Ultra Wideband (IR-UWB) Transceiver for High-Rate Biotelemetry." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1432226195.
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21
Chau, Sam. "Investigation of silicon PIN-detector for laser pulse detection." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-325.
Повний текст джерелаАнотація:
This report has been written at SAAB Bofors Dynamics (SBD) AB in Gothenburg at the department of optronic systems.
In military observation operations, a target to hit is chosen by illumination of a laser designator. From the targetpoint laser radiation is reflected on a detector that helps identify the target. The detector is a semiconductor PIN-type that has been investigated in a laboratory environment together with a specially designed laser source. The detector is a photodiode and using purchased components, circuits for both the photodiode and the laserdiode has been designed and fabricated. The bandwidth of the op-amp should be about 30 MHz, in the experiments a bandwidth of 42 MHz was used. Initially the feedback network, which consists of a 5.6 pF capacitor in parallel with a 1-kohm resistor determined the bandwidth. To avoid the op-amp saturate under strong illuminated laser radiation the feedback network will use a 56-pF capacitor and a 100-ohm resistor respectively.
The laser should be pulsed with 10-20 ns width, 10 Hz repetition frequency, about 800 nm wavelength and a maximum output power of 80 mW. To avoid electrical reflection signals at measurement equipment connections, the laser circuit includes a resistor of about 50 ohm, that together with the resistance in the laserdiode forms the right termination that eliminate the reflection signals. The wire-wound type of resistor shall be avoided in this application and instead a surface mounted type was beneficial with much lower inductance. The detector showed a linear behaviour up to 40-mW optical power. Further investigation was hindered by the breakdown of the laserdiodes. The function generator limits the tests to achieve 80 mW in light power. In different experiments the responsivity of the photodiode is different from the nominal value, however it would have required more time to investigate the causes.
22
Orchard, D. A. "Pulsed metal vapour lasers operating in blue-violet spectral region." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315810.
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McCarthy, Larry K. "Steady Flow and Pulsed Performance Trends of High Concentration DMFCs." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10434.
Повний текст джерелаАнотація:
Direct Methanol Fuel Cells (DMFCs) are a promising source of energy due to their potentially high energy density, facilitated fuel delivery and storage, and precluded fuel processing. However, DMFCs have several challenges which need to be resolved before they can replace existing energy sources. Some of the challenges include lower power density, relatively high cost, and uncertain reliability. These issues are all promoted, at least in part, by the methanol crossover phenomenon, wherein membrane permeability allows the undesirable species transport of methanol from anode to cathode. This phenomenon also causes the requirement of dilute fuel mixtures, which is undesirable from an energy density viewpoint.
Steady flow polarization curves were first analyzed at various concentrations. An optimal concentration range was found wherein both methanol crossover and concentration losses were effectively minimized. During the study of transient phenomena, the fuel was first temporarily discontinued. It was found that a significant cell potential enhancement occurred due to anodic fuel concentration reduction and thus depleting the reactant crossover. The percentage voltage increase was considerably greater at higher concentrations. Based on the fuel discontinuation, a hydraulic pulsing operation was developed and tested. During some of these continuous pulsing schemes, fuel discontinuation did not result in an instantaneous cell potential enhancement mainly due to the internal inertia of the membrane. Nonetheless, a significant cell potential and fuel efficiency enhancement was observed. In addition, the pulse of both fuel and current density resulted in a significant power density increase.
24
Dibra, Donald [Verfasser]. "Single Pulse Safe Operating Area of Trench Power MOSFETs in Automotive Power Integrated Circuits / Donald Dibra." München : Verlag Dr. Hut, 2011. http://d-nb.info/1018982922/34.
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25
McKenna, Jarlath. "Probing atomic and molecular dynamics with intense femtosecond laser pulses : design, operation and proposals 1999-2006." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437478.
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26
Yagci, Mahmut Emre. "Development Of A Picosecond Pulsed Mode-locked Fiber Laser." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615773/index.pdf.
Повний текст джерелаАнотація:
Fiber lasers represent the state-of-the-art in laser technology and hold great promise for a
wide range of applications because they have a minimum of exposed optical interfaces,
very high efficiency, and are capable of exceptional beam quality. In the near future, the
most important markets such as micromachining, automotive, biomedical and military
applications will begin to use this technology. The scope of this thesis is to design and
develop a short picosecond pulsed fiber laser using rare-earth doped fiber as a gain
medium. The proposed master oscillator power amplifier (MOPA) will be used to generate
pulses with high repetition rates.
In this study, first we explain the basic theoretical background of nonlinear optics and fiber
laser. Then, the numerical simulation will be introduced to explain how the laser system
design and optimization. The simulation is based on nonlinear Schrödinger equation with the method of split-step evaluation. The brief theoretical background and simulation results of the laser system will be shown. Finally, the experimental study of the developmental fiber laser system that comprises an oscillator, preamplifier and power amplifier will be discussed.
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Dulgergil, Ebru. "Development Of A Pulsed Fiber Laser For Ladar System." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614635/index.pdf.
Повний текст джерелаАнотація:
In recent years laser technology has increasingly developed with the use of
fiber lasers and this has provided the possibility to implement different techniques in
the defense industry. LADAR is at the forefront of these techniques. Fiber lasers
constitute a perfect source for LADAR systems due to their excellent robustness,
compact size and high-power generation capability. In this study we will explore the
development of a pulsed fiber laser source for a LADAR system that can obtain high
resolution 3D images in eye-safe region.
A high power, all fiber integrated erbium system with strictly single mode
operation in eye-safe region based on MOPA (master oscillator power amplifier)
configuration with seed source and amplifier part was developed. Both the use of an
actively mode locked laser with erbium doped fiber and fiber coupled modulated
distributed feedback diode laser were investigated as seed sources for the amplifier
part. Both erbium doped single clad fiber and erbium-ytterbium doped double clad
gain fiber were used in this amplifier system. After amplification of the actively
mode locked laser, 12 W of average optical power was obtained through single
mode fiber with 1ns pulse duration at 10 MHz which corresponds to 1.2 kW peak
power. For the fiber coupled DFB diode laser, 9.5W average power was obtained
with around 8 ns duration pulses at 100 kHz and about 9.2 W average power was
also obtained with around 700 ps duration pulses at 1 MHz through strictly single
mode fiber at the output of the same amplifier system as was used in the actively
mode locked seed source. In both cases calculated peak power was around 10 kW
v
which is estimated as the highest peak power for an all fiber integrated system with
single mode operation.
The development of such a fiber system with high power capability, compact
size and free of misalignment is expected to be useful for LADAR application as
well as other areas such as eye surgery, 3D silicon processing or any other material
processing applications.
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Curry, Randy D. "Design and operation of a 45 μs repetitively pulsed 12 mw electron beam for a CO₂ laser". Thesis, University of St Andrews, 1992. http://hdl.handle.net/10023/10972.
Повний текст джерелаАнотація:
The parameter space over which electron beams operate for pumping CO₂ lasers significantly extended. A repetitive pulsed power/electron beam system for the generation of 45 µs, 220 keV, electron beams for CO₂ lasers has been designed and implemented which can operate over a 6:1 impedance range. The system consists of a 150 kV – 250 kV modulator and a large area, (2.500 cm²) 5-20 mλ /cm² hot-cathode electron-beam gun. The system is designed and fabricated to be used in conjunction with an electron beam sustained laser and is capable of operating continuously at up to 10 pps. The following thesis examines, in detail, the experimental and theoretical investigation of the modulator/electron beam subsystems which comprise the electron beam system. Parameters of the CO₂ laser which determine the electron beam parameter space, and thus the modulator characteristics, are reviewed. Both cold-cathode and hot-cathode pulsed current parameters are reviewed, and the cathode characteristics upon which the hot-cathode was selected are discussed. The 132 thoriated tungsten filament, grid-controlled, hot-cathode gun used to generate the required 5-20 mλ/cm², 250 cm length source of electron beam with a spatial flatness of ± 10% is shown. Based on the hot-cathode electron beam gun design, the theoretical and practical design characteristics of the hollow-cathode, thyratron switched, 1800 J, 10 pps, 250 kV modulator are shown. Design equations which allow selection of the modulator operation range, and selection of the modulator matching resistors used to match the fixed impedance modulator to the 6:1 electron beam impedance range with a pulse droop of less then 0.7% and a pulse flatness of ± 10% are derived. Moreover, a detailed discussion of the circuit simulations used to both tune and optimize the modulator's impedance tapered, Transformer-coupled Type E PFN to the four electron beam operating ranges are shown. Practical layout and design and the grounding and shielding principles employed in the system. Component spacings required to insure reliable modulator operation at 250kV are also considered. The design and implementation of the 45 µs, SCR switched, transformer-coupled PFN based grid-pulser are discussed. The grid pulser characteristics including the 105-650 V, 28-166 A, pulse required to control the 5-20 mλ / cm²,hot-cathode current density are examined. Theoretical design equations are derived to allow, the Miller capacitance, and thus the time varying impedance of the grid-cathode region to be predicted. Circuit simulations showing the grid-pulser circuit interaction with the constant perveance, Miller capacitance dominated, grid-cathode load are discussed. Final layout of the SCR-switched, grid-pulser including design of the spiral inductors used for the PFN is reported. Specific layout details are shown which allow the grid pulser to operate reliably while floating at the 220 kV electron beam acceleration pulse. A discussion of the subsystem experimental integration phase conducted at Pulse Sciences, Inc. is also presented in the following thesis. Test results of the modulator and grid-pulser into their respective electron beam loads are compared with the circuit simulations. Relevant vacuum flashover physics issues found during the experimental integration of the modulator, grid-pulser, and electron-beam gun are considered. Specific discussions of the vacuum, gap and vacuum insulator physics which effect the operation of the large area electron beam gun are reported. Included in this discussion is the experimental cold- cathode conditioning procedure used to condition the electron-beam gun to 250 kV. In-situ, hot-cathode filament carburization and activation procedures developed during the integration phase of the program are also presented, with a short discussion of the background mass spectra measured during the experiments. Finally, the experimental characterization. of the spatial uniformity of the electron beam is reported along with a short summary of the investigation results.
29
Saha, Aparna Saha. "CONTROL OF MULTILEVEL CONVERTERS FOR VOLTAGE BALANCING AND FAULT-TOLERANT OPERATIONS." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512661551448008.
Повний текст джерела
30
Liyanage, Chinthaka. "Specific property analysis of thin-film semiconductors for effective optical logical operations." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1217089206.
Повний текст джерела
31
Elsayed, Ahmed T. "Optimum Distribution System Architectures for Efficient Operation of Hybrid AC/DC Power Systems Involving Energy Storage and Pulsed Loads." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3005.
Повний текст джерелаАнотація:
After more than a century of the ultimate dominance of AC in distribution systems, DC distribution is being re-considered. However, the advantages of AC systems cannot be omitted. This is mainly due to the cheap and efficient means of generation provided by the synchronous AC machines and voltage stepping up/down allowed by the AC transformers. As an intermediate solution, hybrid AC/DC distribution systems or microgrids are proposed. This hybridization of distribution systems, incorporation of heterogeneous mix of energy sources, and introducing Pulsed Power Loads (PPL) together add more complications and challenges to the design problem of distribution systems. In this dissertation, a comprehensive multi-objective optimization approach is presented to determine the optimal design of the AC/DC distribution system architecture. The mathematical formulation of a multi-objective optimal power flow problem based on the sequential power flow method and the Pareto concept is developed and discussed. The outcome of this approach is to answer the following questions: 1) the optimal size and location of energy storage (ES) in the AC/DC distribution system, 2) optimal location of the PPLs, 3) optimal point of common coupling (PCC) between the AC and DC sides of the network, and 4) optimal network connectivity. These parameters are to be optimized to design a distribution architecture that supplies the PPLs, while fulfilling the safe operation constraints and the related standard limitations. The optimization problem is NP-hard, mixed integer and combinatorial with nonlinear constraints. Four objectives are involved in the problem: minimizing the voltage deviation (ΔV), minimizing frequency deviation (Δf), minimizing the active power losses in the distribution system and minimizing the energy storage weight. The last objective is considered in the context of ship power systems, where the equipment’s weight and size are restricted.
The utilization of Hybrid Energy Storage Systems (HESS) in PPL applications is investigated. The design, hardware implementation and performance evaluation of an advanced – low cost Modular Energy Storage regulator (MESR) to efficiently integrate ES to the DC bus are depicted. MESR provides a set of unique features: 1) It is capable of controlling each individual unit within a series/parallel array (i.e. each single unit can be treated, controlled and monitored separately from the others), 2) It is able to charge some units within an ES array while other units continue to serve the load, 3) Balance the SoC without the need for power electronic converters, and 4) It is able to electrically disconnect a unit and allow the operator to perform the required maintenance or replacement without affecting the performance of the whole array.
A low speed flywheel Energy Storage System (FESS) is designed and implemented to be used as an energy reservoir in PPL applications. The system was based on a separately excited DC machine and a bi-directional Buck-Boost converter as the driver to control the charging/discharging of the flywheel. Stable control loops were designed to charge the FESS off the pulse and discharge on the pulse. All the developments in this dissertation were experimentally verified at the Smart Grid Testbed.
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Globisch, Björn [Verfasser], and Martin [Akademischer Betreuer] Koch. "Photoconductive Terahertz Emitters and Detectors for the Operation with 1550 nm Pulsed Fiber Lasers / Björn Globisch ; Betreuer: Martin Koch." Marburg : Philipps-Universität Marburg, 2017. http://d-nb.info/1136077995/34.
Повний текст джерела
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Тугай, Сергій Борисович. "Імпульсні режими роботи технологічних електронно-променевих гармат високовольтного тліючого розряду". Doctoral thesis, Київ, 2013. https://ela.kpi.ua/handle/123456789/6373.
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34
Steele, Alasdair. "Investigating the quasiparticle dynamics operating in the electrodes of superconducting tunnel junctions using nanosecond phonon pulses." Thesis, Lancaster University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369498.
Повний текст джерела
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Cochain, Jérémy. "Numerical and experimental study of misaligned and wavy mechanical face seals operating under pressure pulses and pressure inversions." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2271/document.
Повний текст джерелаАнотація:
Les garnitures mécaniques sont utilisées dans de multiples applications pour réaliser l'étanchéité autour d'arbres en rotation. Ces composants peuvent fonctionner efficacement pendant plusieurs années en conditions stables, mais leur durée de vie est significativement réduite lorsque les conditions varient. L'objectif de ce travail de recherche est de développer et d’utiliser un banc d'essais et code de calcul pour étudier l'impact de pulsations de pression, d’inversions de pression et du chargement dynamique résultant sur les performances de garnitures mécaniques ayant des faces mésalignées et présentant des défauts de planéité.Le solveur fluide d'un modèle numérique de garnitures mécaniques a été étendu aux conditions transitoires. Un module résolvant la dynamique des forces et des moments a été ajouté afin de prédire le déplacement axial et les déplacements angulaires de la face montée de manière flexible. Afin de caractériser les performances de garnitures, un banc d'essais générant des pulses de pression a été instrumenté et des méthodes de mesure de perte de volume d'huile et d'entrée d'eau mises en place.Des garnitures mécaniques à faces parallèles puis mésalignées, fonctionnant sous pulsations et inversions de pression, ont été testées expérimentalement et simulées. Seules de très faibles augmentations d'eau dans l'huile ont été observées, sans augmentation au cours du temps, et sans fuite d'huile mesurable. Les faibles valeurs d'entrées d'eau sont dues à la faible épaisseur de film et à la courte durée des inversions de pression. Une garniture mécanique expérimentale à fort défaut de planéité a aussi été testée. Contrairement aux autres paramètres, le défaut de planéité semble augmenter significativement la fuite et promouvoir les entrées d'eau et pourrait ainsi être à l'origine de certaines défaillancesFace seals are mechanical devices used to seal rotating shafts in numerous applications. While they can operate efficiently under steady conditions for years, they tend to fail prematurely when operating in severe, or rapidly varying conditions. The focus of this research work is the development and use of an experimental and a numerical method to investigate the impact of pressure pulses, pressure inversions and induced dynamic loading on the performance of mechanical face seals exhibiting face misalignment and waviness.The fluid solver of a state-of-the art face seal numerical model was extended to transient conditions and a module solving the dynamics for the axial and angular degrees of freedom of the flexibly-mounted stator added. A system-level experimental setup generating pressure pulses was instrumented and methods to characterise face seal performance in terms of oil volume loss and ingression of water outer-fluid selected and implemented.Face seals, with flat and misaligned faces, operating under pressure pulses and pressure inversions were experimentally tested and simulated. They show only slight increase of water in the oil, no increase over time, and no measurable oil leakage. The low water ingression is due to low film thickness combined with the short duration of pressure inversions. An exploratory face seal of high waviness was also experimentally tested. Contrary to the other parameters, the waviness appears to significantly increase the leakage and promote water ingression and could thus be at the origin of some seal failures
36
Elam, Charles R. IV. "Predicting Arterial Oxygen Desaturation Events Via Patient Journal and Pulse Oximetry Data in Postoperative Ambulatory Surgery Patients." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5649.
Повний текст джерелаАнотація:
Associations between patient and procedural factors on the nature and quality of the immediate in-home recovery from anesthesia following ambulatory orthopedic surgery are unknown. Further, there is a paucity of outcomes research quantitatively categorizing in-home
patient recovery and safety following discharge from same-day orthopedic procedures. Tools are available, however, to shed light on outcomes in this population, and integration of such available measures is critical.
Ambulatory orthopedic surgery is a burgeoning specialty, with growth expected over the foreseeable future. The expected increased patient caseload subsequent to implementation of the Affordable Care Act and aging Baby Boom generation suggests greater morbidity and mortality is on the horizon unless aggressive measures are taken at mitigating risk. Similarly, as the obesity epidemic expands, obesity-related comorbid conditions including obstructive sleep apnea (OSA) are likely to grow.
The purpose of this research was to explore the relationship between ambulatory orthopedic patient-reported activities (quality of life metrics) and diagnostic factors (physical and perioperative care data) in the immediate postoperative period that are predictive of arterial oxygen desaturation. Data was obtained using a novel patient journal exploring sleep, pain, nausea, tobacco use, alcohol use, and appetite in conjunction with a valid and reliable portable, wrist-worn pulse oximeter. Additional assessment data was taken from the preanesthetic assessment. All participants were scored according to the STOP-Bang questionnaire, an accepted survey of OSA risk.
Patients were recruited from a busy metropolitan ambulatory surgery center in Richmond, Virginia that sees approximately 500 cases monthly, and a 309-bed tertiary care hospital in West Burlington, Iowa. The target sample included 52 individual patients with data collected over the first two post-operative nights following discharge. Two patients were excluded.
Negative binomial regression, log10 transformation, and least-squares regression examined the relationships the STOP-Bang questionnaire, quality of life data, and physical perioperative data had on postoperative desaturation events. Results suggested the STOP-Bang score predicted desaturation events and that age and BMI were significant individual predictors. Opiate pain medication treatment, a happy mood, and home CPAP use were associated with decreased events.
This study provided a unique perspective in patient safety research, relating human behaviors and experiences with postoperative oxygen desaturation. Future research projects aligned with postoperative monitoring, pulse oximetry, patient safety, and obstructive sleep apnea are potential following the findings of this study.
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Jones, Jason Patrick. "Electro-thermo-mechanical characterization of stress development in AlGaN/GaN HEMTs under RF operating conditions." Thesis, Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53528.
Повний текст джерелаАнотація:
Gallium nitride (GaN) based high electron mobility transistors (HEMTs) offer numerous benefits for both direct current (DC) and radio frequency (RF) power technology due to their combination of large band gap, high electrical breakdown field, high peak and saturation carrier velocity, and good stability at high temperatures. In particular, AlGaN/GaN heterostructures are of great interest because of the unique conduction channel that develops as a result of the spontaneous and piezoelectric polarization that occurs in these layers. This channel is a vertically confined plane of free carriers that is often called a 2 dimensional electron gas (or 2DEG). Although these devices have shown an improvement in performance over previous heterostructures, reliability issues are a concern because of the high temperatures and electric fields that develop during operation. Therefore, characterizing electrical and thermal profiles within AlGaN/GaN HEMTs is critical for understanding the various factors that contribute to device failures. Little research has been performed to model and characterize these devices under RF bias conditions, and is therefore of great interest. Under pulsed conditions, a single cycle consists of an “on-state” period where power is supplied to the device and self-heating occurs, followed by an “off-state” period where no power is supplied to the device and the device cools. The percentage of a single cycle in which the device is powered is called the duty cycle.
In this work, we present a coupled electro-thermo-mechanical finite-element model for describing the development of temperature, stress, and strain profiles within AlGaN/GaN HEMTs under DC and AC power conditions for various duty cycles. It is found that bias conditions including source-to-drain voltage, source-to-gate voltage, and pulsing frequency directly contribute to the electro-thermo-mechanical response of the device, which is known to effect device performance and reliability. The model is validated by comparing numerical simulations to experimental electrical curves (Ids-Vds) and experimental strain measurements performed using scanning joule expansion microscopy (SJEM). In addition, we show how the operating conditions (bias applied and AC duty cycle) impact the thermal profiles of the device and outline how the stress in the device changes through a pulsed cycle due to the changing thermal and electrical profiles. Qualitatively, the numerical model has good agreement across a broad range of bias conditions, further validating the model as a tool to better understand device performance and reliability.
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Jarošová, Veronika. "Návrh kardiostimulátoru typu "On Demand" řízeného mikropočítačem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220856.
Повний текст джерелаАнотація:
The aim of this diploma work is the suggestion and realization of a cardiostimulator of „On Demand“ type operated by microcontroller. The work is structured on four thematic parts. For the correct suggestion of the whole system, firstly is necessary to understand correctly the cell’s electrophysiology and heart’s anatomy, inclusive the cardiology arrhytmia, which are adherent to cardiostimulators. The cardiostimulator is inhibited by the R-wave and is adaptive on a pulse rate of a source signal. The whole system is supplied by batteries and this supplying is taken into consideration. The network’s functionality is realized on the ECG simulator. There are suggested the suitable enhancements in discussion.
39
Fusari, Flavio. "Continuous wave and modelocked femtosecond novel bulk glass lasers operating around 2000 nm." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1694.
Повний текст джерелаАнотація:
This thesis reports on the development of glass-based femtosecond laser sources around 2 µm wavelength. In order to be able to produce 2 µm radiation the dopants used were trivalent Thulium (Tm³⁺) and trivalent Holmium (Ho³⁺) that could be optically pumped with Ti:Sapphire radiation at 0.8 µm and semiconductor disk lasers (SDL) at 1.2 µm. The samples were produced at Leeds University and polished in-house in bulk form and deployed in free space laser cavities. Tellurite compounds doped with Tm³⁺ produced stable continuous wave 1.94 µm radiation when pumped at 800 nm with a maximum efficiency of 28.4% with respect to the absorbed power and maximum output power around 120 mW when pumped using a Ti:Sapphire operating around 0.8 µm. The radiation was broadly tunable across 130 nm. Tm³⁺-Ho³⁺ doubly doped tellurite samples lased around 2.02 µm with maximum efficiency of 25.9% and with P[subscript(OUT)]=75 mW and a smooth tunability of 125 nm. The fluorogermanate glass doped with Tm³⁺ gave an absorbed to output power efficiency of 50%. The maximum continuous wave output powers obtained were around 190 mW and limited by the available pump power at 0.8 µm. These results together with a very low threshold of 60 mW of incident power were comparable to the crystalline counterparts to this gain medium. The Tm3+ tellurite and the Tm³⁺-Ho³⁺ tellurite compounds were also pumped by an SDL operating at 1215 nm to obtain an indication of the viability of such a pump scheme. The results were a maximum internal slope efficiency of 22.4% with a highest output power of 60 mW. The comparison demonstrated that 1.2 µm pumping was competitive with using 0.8 µm wavelength. The use of semiconductor saturable absorbing mirror (SESAM) technology was used for the modelocking of these lasers. The SESAM was produced in Canada and implanted with As⁺ ions in order to reduce the relaxation time. Trains of transform-limited laser pulses at 222 MHz as short as 410 fs centred at 1.99 µm were produced for the first time with a bulk Tm³⁺:Fluorogermanate glass. The maximum average output power obtained was of 84 mW. The same SESAM deployed on the Tm³⁺-Ho³⁺ Tellurite compounds gave trains of transform-limited pulses as short as 630 fs at 2.01 µm with a repetition rate of 143 MHz and a maximum averaged output power of 43 mW. The regime of propagation obtained was soliton-like and the modelocking was self-starting. The results obtained with bulk glass were very promising and open interesting research pathways within the realm of amorphous bulk gain media.
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Tambara, Rodrigo Varella. "Desenvolvimento de uma fonte de potência CA para geração de formas de onda de até 2kHz." Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/8482.
Повний текст джерелаАнотація:
Conselho Nacional de Desenvolvimento Científico e TecnológicoThis work presents the development of an alternating current power source with a single-phase full bridge voltage inverter, based on electronic switches. The source is designed to drive electromechanical and electric plants. The prototype is designed with 1kVA nominal power and is able to generate sinusoidal waveforms up to 2kHz. The inverter operates at the switching frequency of 50kHz. A robust model reference adaptive controller is designed and implemented to adjust the output voltage of the source. Additionally, the elements of the source and the system for measuring the electrical parameters are presented. A digital signal controller is used to control and generate signals with pulse width modulation. The discretization of the control system is performed using the delta operator. Finally, experimental results and analysis of the closed loop system are presented. Based on these results, the experimental performance of the designed source and the proposed control system are examined.
Este trabalho apresenta o desenvolvimento de uma fonte de potência de corrente alternada com um inversor de tensão em ponte completa monofásico, composto por interruptores eletrônicos. Esta fonte é concebida para o acionamento de plantas elétricas e eletromecânicas. O protótipo projetado tem uma potência nominal de 1kVA e é capaz de gerar formas de onda senoidais de até 2kHz. O inversor opera em uma frequência de comutação de 50kHz. Um controlador adaptativo robusto por modelo de referência é projetado e implementado para ajuste da tensão de saída da fonte. Adicionalmente, são apresentados os elementos da fonte e o sistema de medição das variáveis elétricas. Um processador digital de sinais é utilizado para controle e geração de sinais com modulação por largura de pulso. A discretização do sistema de controle é realizada por meio do operador delta. Por fim, são apresentados resultados experimentais e análise do sistema em malha fechada. A partir destes resultados, averiguou-se o desempenho experimental da fonte projetada e do sistema de controle proposto.
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Pascal, Jean-Pierre. "Etude de circuits d'aide à la commutation de thyristors GTO montés en série pour des applications à la traction ferroviaire." Paris 6, 1986. http://www.theses.fr/1986PA066273.
Повний текст джерелаАнотація:
Revue des propriétés des thyristors interrupteurs. Aptitude à l'utilisation en grande traction. Etude du rétablissement de la tension aux bornes. Soufflage et mise en série des thyristors interrupteurs. Caractérisation des GTO de grande puissance.
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Kifle, Esrom Aschenaki. "Fabrication and characterization of waveguide lasers operating in the infrared spectral range." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/668351.
Повний текст джерелаАнотація:
Aquest treball de tesi ha tractat la fabricació i la caracterització de làsers de guia d’ona compactes i eficients que funcionen en règims d’ona contínua i Q-commutat de forma passiva al voltant dels 2 micròmetres en l’espectre electromagnètic. Per aconseguir-los, es van utilitzar materials cristal•lins basats en tungstats dobles d’estructura monoclínica dopats amb erbi (Er3+), tuli (Tm3+) o holmi (Ho3+). Aquests materials làser es van escollir per les seves propietats òptiques d’emissió i absorció que els fan aptes per aconseguir dispositius compactes. Per a la fabricació i l'estructuració de les guies d'ona, es va utilitzar la combinació dels següents mètodes: creixement cristal•lí en solució a alta temperatura, creixement d’epitàxies en fase líquida, tall amb serra micromètrica de diamant i escriptura directa per làser de femtosegons. A més, es van implementar diferents tècniques de caracterització com la microscòpia confocal, μ-Raman i μ-luminescència per avaluar la qualitat i la idoneïtat de les guies d'ones. En el règim d’ona Q-commutat de forma passiva, es va estudiar la idoneïtat de diferents absorbidors saturables, com ara cristalls de ZnSe o ZnS dopats amb Cr2+, MoS2 i nanoestructures de carboni (grafè i els nanotubs de carboni) dipositats sobre un substrat transparent o directament a la superfície de la mostra que contenia les guies d'ones. La fabricació d’una guia d’ona acanalada superficial mitjançant creixement epitaxial va donar com a resultat una eficiència làser rècord gairebé aproximada al límit teòric. Es van fabricar i estudiar guies d'ones soterrades (canals) fabricades mitjançant un làser de femtosegon. Igualment, es van fabricar i estudiar guies d'ona acanalades en superfície (forma d'anell) i separadors en forma de Y. Finalment, es van demostrar làsers de guia d’ona capaços d’oferir una potència de sortida de nivell de watts, així com làsers de guia d’ona en règim Q-commutat de forma passiva molt estable.Este trabajo de tesis ha tratado la fabricación y caracterización de láseres de guía de onda compactos y eficientes que funcionan en los regímenes de onda continua y Q-conmutado de forma pasiva alrededor de los 2 micrómetros en el espectro electromagnético. Para lograrlos, se emplearon materiales cristalinos basados en tungstatos dobles de estructura monoclínica dopados con erbio (Er3+), tulio (Tm3+) u holmio (Ho3+). Los medios de ganancia fueron elegidos debido a sus propiedades ópticas de emisión y absorción que los hacen adecuados para lograr dispositivos compactos. Para la fabricación y estructuración de las guías de onda se utilizó una combinación de los métodos: crecimiento cristalino en solución a alta temperatura, crecimiento epitaxial en fase líquida, corte con sierra micrométrica de diamante y escritura directa por láser de femtosegundo. Además, se implementaron diferentes técnicas de caracterización, como la microscopía confocal, μ-Raman y μ-luminiscencia para evaluar la calidad y la idoneidad de las guías de onda. En el régimen de operación Q-conmutado pasivo, se estudió la idoneidad de diferentes absorbentes saturables, como los cristales de ZnSe o ZnS dopados con Cr:2+, el MoS2 y las nanoestructuras de carbono (grafeno y los nanotubos de carbono) depositados sobre un sustrato transparente o directamente sobre la superficie de la muestra que contiene las guías de onda. La fabricación de una guía de onda acanalada superficial mediante crecimiento epitaxial resultó en una eficiencia láser récord muy próximo al límite teórico. Se fabricaron y estudiaron guías de onda enterradas fabricadas mediante escritura con láser de femtosegundo. Se fabricaron y estudiaron guías de onda acanaladas en superficie (revestimiento en forma de anillo) y divisores en forma de Y. Finalmente, se demostraron láseres de guía de onda capaces de generar una potencia de salida de vatios, así como láseres de guía de onda en régimen Q-conmutado pasivamente muy estable.
This thesis work has dealt with the fabrication and the characterization of compact and efficient waveguide lasers operating in the continuous wave and passively Q-switched operation regimes around 2 μm in the spectral range. To achieve those, erbium (Er3+), thulium (Tm3+) or holmium (Ho3+) doped monoclinic double tungstate crystalline materials were employed. The gain media were chosen due to their ability to generate polarized laser emission and their large gain cross-sections which make them suitable for achieving compact devices. The combination of the top-seeded solution growth, liquid phase epitaxy, diamond saw dicing and femtosecond direct laser writing methods were employed for fabricating and structuring the waveguides. Furthermore, different characterization techniques such as confocal microscopy, μ-Raman, and μ-luminescence mapping were implemented to assess the quality and suitability of the fabricated waveguides for lasing application. In the passively Q-switched operation regime, the suitability of different saturable absorbers such as transition-metal-doped chalcogenide crystals (Cr2+:ZnSe or ZnS), few-layer transition metal dichalcogenide (MoS2) and carbon nanostructures such as graphene and single-walled carbon nanotubes deposited on a transparent substrate or directly onto the surface of the sample containing the waveguides were tested. The fabrication of an epitaxially grown surface channel waveguide resulted in a record slope efficiency almost approaching the theoretical limit. Femtosecond laser written buried channel waveguides (with circular and hexagonal optical-lattice-like cladding), surface channel waveguides (with half-ring-shaped cladding) and Y-branch splitters were fabricated and studied. Waveguide lasers capable of delivering a watt-level output power as well as those with a stable passive Q-switching operation were demonstrated.
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Sanches, Fabricio Marqui [UNESP]. "Sistema de geração e armazenamento de energia elétrica utilizando transdutor piezelétrico na forma pulsada." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/132420.
Повний текст джерелаАнотація:
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho é investigada a viabilidade energética do emprego de buzzers piezelétricos, circuito retificador de onda completa e conversor DC-DC elevador em um sistemas de power harvesting submetido a esforços mecânicos causados pelo tráfego de veículos e/ou caminhar de pedestres, demonstrando a possibilidade de reutilização dessa energia no carregamento de baterias para alimentação de circuitos autônomos de monitoramento, indicação, iluminação, etc., em locais remotos, eliminando ou estendendo os intervalos necessário entre as recargas desses dispositivos. O gerador piezelétrico é analisado mediante a excitação realizada por um cilindro pneumático simulador de impactos controlado eletronicamente com frequência de 0,5 Hz e 1 Hz, contendo diferentes quantidades de PZTs (2, 4 e 8) e configuração de ligação (série ou paralelo). Os resultados extraídos são referentes à tensão elétrica, corrente, potência e energia armazenada em função do tempo, sendo ainda feitas relações dessas grandezas com diferentes números de PZTs, área que ocupam, força e pressão aplicada sobre os mesmos. Ao final pode-se concluir a viabilidade da utilização de dispositivos simples em sistemas de power harvesting para geração de energia através de excitações na forma pulsada e em baixas frequências, sendo os maiores valores na saída do circuito em termos de potência e corrente para tensão de 5 volts, 108 µW e 21,5 µA (0,53 Kg e 0,83 N/cm2), bem como 118,8 µW e 23,6 µA para (2,13 Kg e 3,33 N/cm2), obtidos com 8 PZTs, conectados em paralelo e excitados a 1 Hz.
This paper investigated the energy viability of the use of piezoelectric buzzers, rectifier circuit full-wave and DC-DC-converter in a power harvesting systems subjected to mechanical stress caused by the traffic of vehicles and / or walk for pedestrians, demonstrating the possibility of re-use of energy in charging batteries to power autonomous monitoring circuits, display, illumination, etc., in remote locations, eliminating or extending the intervals needed between charges these devices. The piezoelectric generator is analyzed through excitation carried out by a pneumatic cylinder simulator electronically controlled impacts with a frequency of 0.5 Hz and 1 Hz, containing different amounts of PZTs (2, 4, 8) and connection configuration (parallel or serial) . The extracted results are related to the voltage, current, power and energy stored in function of time, still being made relations of these quantities for the number of PZTs, area they occupy, force and pressure applied on them. At the end we can conclude the feasibility of using simple devices in power harvesting systems to generate energy through excitations in pulsed manner and at low frequencies, with higher values in the circuit output in terms of power and current to voltage 5 volts, 108 µW and 21,5 µA (0,53 Kg and 0,83 N/cm2), just like 118,8 µW and 23,6 µA to (2,13 Kg e 3,33 N/cm2), obtained with 8 PZTs, connected in parallel and excited to 1 Hz.
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Lee, Darryl Liang Wee. "Development of a PP-MOCVD System and its Design and Operational Parameters for Uniform Industrial Coatings on 3D Objects." Thesis, University of Canterbury. Dept. of Mechanical Engineering, 2014. http://hdl.handle.net/10092/9644.
Повний текст джерелаАнотація:
Increase in demand for uniform ceramic coatings on larger industrial components have led to a need for a PP-MOCVD coating system scale up. The objective of this thesis is to develop a fully functional coating system operating in the PP-MOCVD regime that is able to deposit thin film ceramic coatings on commercial or industrial components with complex 3D geometries.
This can be achieved by applying engineering and vacuum science theories, coupled with the established fundamentals of PP-MOCVD. A larger system was designed and assembled around the boundaries set by the dimensions and geometry of a stainless steel water pump impellor acting as the base substrate. Most of the components were sourced off the shelf from vacuum and fluid specialists. Components which were unavailable for various reasons were designed, and machined in-house by the departmental workshop.
Initial test depositions were conducted using small stainless steel disk substrates, heated using a resistive heater similar to the one utilised on the research scale system. The test depositions were performed with the heater and substrate combination placed in strategic locations. This is to test the overall uniformity of precursor flux in the chamber volume. The resulting coating uniformity on the disk surfaces were fair but problems such as the large collection of unreacted precursor on the chamber viewport and valve timing issues had to be addressed.
Before making any improvements to the system, each of the process areas leading to a successful deposition needed to be understood. Five process areas were developed: ‘Liquid Delivery’, ‘Atomization’, ‘Evaporation’, ‘Transport and Reactor Geometry’, and ‘Droplet Management’. Each of the process areas were analysed individually and changes were made to push for a maximum evaporation efficiency.
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The improved system provided opportunities to perform depositions that were once not possible for PP-MOCVD. Two sets of deposition tests were designed and conducted. Firstly, the improvements were justified with a series of depositions using flat stainless steel plates with dimensions 65x65x5mm. The other set of 3D case study depositions involve observing the effects of the operational parameters of PP-MOCVD on the uniformity and penetration depths of the coatings into different sized macro blind trenches.
Five geometric setup conditions were used to justify the improvements made to the system. These are: ‘Substrate positioned in the direct line of spray’, ‘Use of an unheated receptor’, ‘Use of a heated receptor’, ‘Use of an unheated receptor with a non-axial substrate setup’, and “Choked Flow’. As expected, the uniformity of the coatings on both sides of the plate varied significantly when the substrate is placed over the line of sight of the precursor spray. Similarly, the coating produced under the induced choked flow condition resulted in low conformality. The introduction of an unheated receptor plate resulted in an increase in uniformity on both sides of the plate. Further prove that PP-MOCVD is geometry independent is provided by the deposition made with the non-axial substrate placement resulting in a coating of similar result to the unheated receptor. The use of a heated receptor provided a source for a secondary evaporation of the larger precursor droplets collected resulting in an increase in coating thickness while maintaining good conformality.
The effects of temperature, pressure, injection volume, and concentration were explored in the final case study. With maximum depths of 50mm, the macro blind trenches has an aspect ratio of 1:1 and cross-sectional areas of 3x3mm, 9x9mm, and 15x15mm. The final results show that as the temperature rises, the depth penetrated into the trench decreases. This could be due to the change in rate limiting steps as homogeneous reactions begin to increase at higher temperatures. Similar trends were observed with increasing pressure. As the pressure difference between the volume of the trenches and the rest of the chamber decreases, the push needed to
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force the precursor down the trench also decreases, resulting in less depth penetration. The effects of injection volume and concentration observed, can be explained by how much precursor molecules are present during one pulse cycle. The more that is available at any given time, the more likely a reaction will occur and deeper the penetration will get. Of course a ceiling or a limit exists where the molecules in the chamber will get evacuated without being reacted.
The future work made possible as a result of the scaled up system are proposed. These include a scale up of the operational parameters to suit any given substrate geometry, improvements to the heating source to achieve greater thermal uniformity, further improvements to the overall system accessibility, and performing other depositions using different substrate materials and precursor types.
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Saroya, Harlin Kaur. "Innovative Non-Thermal Food Processing Technologies Used By The Food Industry In The United States." TopSCHOLAR®, 2017. https://digitalcommons.wku.edu/theses/2028.
Повний текст джерелаАнотація:
This thesis discussed the non-thermal food processing technologies being used within the United States of America. The technologies discussed in this thesis are High- Pressure Processing (HHP), Pulsed Electric Field, Pulsed Light, Irradiation, Ultra Sound, Oscillating Magnetic Fields, and Cold Atmospheric Plasma. A survey was designed and conducted to study the major reasons behind a preference for a particular technology by the organization, and the limitations for not implementing specific technologies. The survey participants were management level, food scientists and, food technologists employed by food processing companies. The questionnaire consisted of ten questions related to demographics, current technology, barriers from other technologies, and research and development of new technologies.
There were a total 223 respondents from various regions of the United States. The respondents had a wide array of industry experience. Of the respondents, 91% of the respondents had either a Bachelor’s Degree, Master’s Degree or Ph D. Thirty-six percent of the participants chose high pressure processing and 20 % chose pulsed electric as the most commonly used non-thermal food processing technologies. Rapidly increasing technologies included cold atmospheric plasma and oscillating magnetic fields. Seventyone percent mentioned the main driver for them to choose non-thermal food processing was better nutrient and sensory properties. As per the results, 41% of respondents believed the major limitations in implementing non-thermal food processing technologies was high investment. The results indicated the main drivers for innovation were equipment manufacturers and research. These researches were either academic or government funded.
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Baumann, Gunther [Verfasser], Wilhelm [Akademischer Betreuer] Dominik, Jan [Akademischer Betreuer] Henninges, Frank [Akademischer Betreuer] Börner, and Michael [Akademischer Betreuer] Kühn. "Determination of displacement and evaporation/precipitation processes via Pulsed Neutron-Gamma (PNG) monitoring for CO2 storage operations / Gunther Baumann. Gutachter: Wilhelm Dominik ; Frank Börner ; Michael Kühn ; Jan Henninges. Betreuer: Wilhelm Dominik ; Jan Henninges." Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1065665113/34.
Повний текст джерела
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Zia, Muneeb. "SRAM system design for memory based computing." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47636.
Повний текст джерелаАнотація:
The objective of the research was to design and test an SRAM system which can meet the performance criteria for Memory Based Computing (MBC). This form of computing consists of a Look-Up Table (LUT) which is basically memory array mapped with a function; the computations thereafter consist of essentially read operations. An MBC framework requires very fast and low power read operations. Moreover, the cells need to be read stable as major part of the computation is done by reading the LUTs mapped in the SRAM array.
Design and measurement of a prototype MBC test-chip with SRAM system optimized for read-heavy applications is presented in this thesis. For this purpose, a prototype MBC system was designed and taped out. Essential study of the write-ability of the core LUT is also presented. The core memory array for function table mapping was characterized for leakage, write-ability and power saving associated with pulsed read mode.
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Johnson, Bruce. "Telemetry Receive/Record & Re-Radiation Pod." International Foundation for Telemetering, 2014. http://hdl.handle.net/10150/577391.
Повний текст джерелаАнотація:
ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CAThis paper discusses the mission needs, design/development, and testing of the (L, S & C Band) Telemetry Receive/Record & Re-Radiation pod.
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Aboelhassan, Mustafa Osman Elrayah. "Robustní řízení synchronního stroje s permanentními magnety a spínaným tokem." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-233605.
Повний текст джерелаАнотація:
Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.
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Liao, Hsiang-chien, and 廖祥鑑. "Effects of Laser Pulse Shape on Operation of the Phase-Stable Proton Accelerator." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/60776764257004473272.
Повний текст джерелаАнотація:
碩士國立中央大學
物理研究所
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Generation of high energy ion beam by laser irradiation on a solid thin foil target is an area of great interest in the research of laser plasma interaction. Several acceleration schemes have been considered in recent years. According to particle simulation studies, the most promising one is the so called phase-stable acceleration (PSA) scheme which proposes to use a circularly-polarized laser pulse interaction with an ultrathin target. The light pressure pushes the electrons forward, leaving the ions behind, until it is balanced out by the space charge electrostatic field generated in the process. For an optimal target thickness the electron sheath formed at the rear surface of the target can trap the ions and synchronously accelerated by the laser pulse leading to a monoenergetic ion beam production. Most parametric studies of the PSA scheme have been using the square laser pulse. From these studies, the operational regime of the PSA can be characterized by a linear relation between the normalized laser amplitude and the product of the plasma density and the target thickness. However, a recent study in our research group found that in addition to the existing PSA operation criterion, the target density must be larger than a threshold density for a given laser intensity in order to generate a monoenergetic ion beam. This thesis focuses on the effects of laser pulse profile on the operation of PSA scheme. The laser pulse of a trapezoidal profile (linear growth-plateau-linear decrease) in time, which somewhat simulates the laser pulse used in experiments is considered. In the parameter regime which satisfies the PSA criterion, our simulation results show an improvement in the ion beam quality with an increasing laser rising time. At the same time, the PSA operational regime can also be expanded using the shaped laser pulse to the cases that the plasma density is below the threshold density recently found.