Дисертації з теми "State mode"
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1
Ånstrand, Melina. "State of mind." Thesis, Konstfack, Textil, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-3563.
Повний текст джерелаАнотація:
Den här uppsatsen är uppbygd så att den följer min konsnärliga och personliga utveckling under tiden på konstfack. Den första delen innehåller en teoridel som sedan följs upp av beskrivningar av mina arbeten. Parallellt med detta löper en berättande text om mitt liv och min relation till kläder som jag haft innan jag började på Konstfack.Textil formgivning / Master 2009 Textile in the Expanded Field
2
Ritsataki, Aliki. "A numerical model of Kerr-Lens mode-locking in solid-state lasers." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325064.
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3
Krist, Peter. "Diamagnetic mode of open gradient magnetic separation." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244846.
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4
Chesworth, Andrew Alexander. "Mode control in thin slab, diode pumped solid state lasers." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/649.
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5
Scharnhorst, Nils [Verfasser]. "Multi-mode ground state cooling of trapped ions / Nils Scharnhorst." Hannover : Technische Informationsbibliothek (TIB), 2018. http://d-nb.info/1166269965/34.
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6
Major, Arkady. "Diode-pumped passively mode-locked ultrashort pulse solid-state lasers." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273384.
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7
Mu, Jianqiu. "State feedback sliding mode control of complex systems with applications." Thesis, University of Kent, 2018. https://kar.kent.ac.uk/65793/.
Повний текст джерелаАнотація:
This thesis concerns the development of robust nonlinear control design for complex systems including nonholonomic systems and large-scale systems using sliding mode control (SMC) techniques under the assumption that all system state variables are accessible for design. The main developments in this thesis include: 1). The concept of generalised regular form and design of a novel sliding function. The mathematical definition of generalised regular form is proposed for the first time. It is an extension of the classical regular form, which makes SMC applicable to a wider class of nonlinear systems. A novel sliding function design, which is based on the global implicit function theorem, is proposed to guarantee unique sliding mode dynamics. 2). The development of decentralised SMC for large-scale interconnected systems. For systems with uncertain interconnections which possess the superposition property, a decentralised control scheme is presented to counteract the effect of the uncertainty by using bounds on uncertainties and interconnections. The bounds used in the design are nonlinear functions instead of constant, linear or polynomial functions. The design strategy has also been expanded to a fully nonlinear case for interconnected systems in the generalised regular form. 3). Robust decentralised SMC for a class of nonlinear systems with uncertainties in input distribution. A system with uncertainties in input distribution is full of challenges. A novel method is proposed to deal with such uncertainties for a class of nonlinear interconnected systems. The designed decentralised SMC enhances the robustness of the controlled systems. This thesis also provides case studies of three applications for the proposed approaches. The existence of the generalised regular form is verified in the trajectory tracking control of a wheeled mobile robot (WMR) system. Both simulations and experiments on the WMR are given to demonstrate the validity and effectiveness of the generalised regular form-based SMC design. A continuous stirred tank reactor (CSTR) system and a longitudinal vehicle-following system are used to test the proposed decentralised SMC schemes. An expanded vehicle-following system with both longitudinal and lateral controllers has been developed to demonstrate the robust control design for system with uncertainties in input distribution.
8
McConnell, Gail. "Nonlinear optical frequency conversion of mode-locked all-solid-state lasers." Thesis, University of Strathclyde, 2001. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=20367.
Повний текст джерелаАнотація:
The work contained in this thesis concerns the design, development and implementation of robust diode-pumped solid-state mode-locked lasers as a platform for nonlinear optical frequency conversion experiments. One objective is to create an ultrashort-pulsed source that is tunable between λ = 600nm and λ = 700nm, since currently no other laser gain media exists that covers this region of the electromagnetic spectrum. This novel source is intended for application to multiphoton imaging. The first demonstration of additive pulse mode-locking of a diode-pumped Nd³⁺: YVO₄ laser operating in the near-infrared is presented and the source characteristics compared to a similar system that is mode-locked using a saturable Bragg reflector. Although the additive-pulsed mode-locked laser demonstrates higher peak power, it is observed to be less robust due to vibrational intolerance. Therefore, the saturable Bragg reflector mode-locked laser is chosen as the basis for frequency conversion experiments. This source is used to develop an efficient picosecond-pulsed ultraviolet laser that is intended to pump an optical parametric oscillator to realise tunable visible radiation in the wavelength region of interest. Using a resonant enhancement method to generate the third harmonic of the near-infrared laser, an average power of 320mW at λ = 355nm is measured, with a peak power of approximately 68W. However, experiment and calculation proves this to be insufficient to reach the oscillation threshold of the proposed optical parametric oscillator to realise a visible tunable source. The near-infrared laser is also used to obtain mid-infrared radiation by use of a quasiphase-matched optical parametric oscillator. An average power of 1W tunable from λ =1460-1601nm is achieved. This is mixed with some fundamental radiation in a nonlinear medium to generate radiation that is tunable from λ = 610 to 650nm. This system is presented with emphasis on suitability for multi-photon imaging.
9
Hechenblaikner, Gerald. "Mode coupling and superfluidity of a Bose-Einstein condensed gas." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249397.
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10
Guerreiro, Paulo Tiago Ferraz de Meira 1967. "Solid-state laser mode-locking and ultrafast studies in quantum semiconductor structures." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282515.
Повний текст джерелаАнотація:
This dissertation describes the development of ultra-short pulse solid-state lasers and the investigation of ultra-short pulse propagation in a nonlinear waveguide. We present laser design considerations involving astigmatism compensation, spot-size estimation, stability, and dispersion compensation, and their application to chromium doped forsterite lasers. Making use of the Kerr nonlinearity of the Cr:forsterite crystal we demonstrate self-mode-locking in Cr:forsterite lasers, both in the hard-aperture and soft-aperture Kerr-lens mode-locking regimes. Sub-200-fs pulses tunable between 1240 and 1285 nm were obtained, with the shortest transform-limited pulses having 45 fs duration at 90 MHz repetition rate with 100 mW output power at 1265 nm. Using a semiconductor quantum-well saturable absorber integrated with a Bragg reflector we demonstrated self-starting passive continuous-wave mode-locked operation of a Cr:forsterite laser. Self-starting mode-locking was the only operational mode of the laser and could be achieved with and without intracavity dispersion compensation. We obtained 70 fs transformed-limited pulses using a prism pair for dispersion compensation, 4 ps pulses without prisms, and pulse energies of up to 2.3 nJ at 90 MHz repetition rate at 1260 nm. Using quantum-confined nanocrystals of lead sulfide in glass as intracavity saturable absorbers we obtained self-starting passive continuous-wave mode-locking in a Cr:forsterite laser. We obtained near transform-limited 4.6 ps laser pulses at 100 MHz repetition rate, and a wide tunability range of 1207 to 1307 nm. We studied femtosecond pulse propagation near a two-photon transition in CdS quantum-dot-doped waveguides produced by the solgel and ion-exchange methods. The observed two-photon absorption and asymmetric spectral modulation of the transmitted pulses were explained by the theoretical model, which incorporated a near-resonant two-photon transition.
11
Gu, Min. "Raman Mode-Selective Spectroscopic Imaging of Redox State in FMN and Flavoprotein." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1398866391.
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12
Ranjit, Narendran. "Multiagent Referral Systems: Maintaining and Applying Trust and Expertise Mode." NCSU, 2007. http://www.lib.ncsu.edu/theses/available/etd-05112007-143631/.
Повний текст джерелаАнотація:
This thesis addresses the challenge of assisting people to solve a problem by helping locate other people who might have the expertise required to solve that problem. To this end, the proposed system assigns an agent to each user. Further, it models a social network as a multiagent system based on the user's existing online identity. It provides heuristics by which an agent can estimate the expertise and trust to be placed in a user with whom the agent's user interactis. Our approach seeks to reduce the problem of finding an answer to a query to the problem of finding a path to a trustworthy expert who can answer the query. To accomplish this, our system uses referrals from one agent to another in the same fashion that word-of-mouth is used when people are looking for an expert. Our models of trust help establish the authenticity and veracity of the referrals and replies. This thesis describes the architecture and implementation of such a system.
13
Kay, Benjamin P. "Resting-State Functional Connectivity in Treatment-Resistant Idiopathic Generalized Epilepsy." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1380612937.
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14
Ho, Bo-shan, and 何寶山. "State policy and urban politics in Hong Kong: a mode of production analysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31976256.
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15
Ho, Bo-shan. "State policy and urban politics in Hong Kong : a mode of production analysis /." [Hong Kong : University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13008912.
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16
Prasankumar, Rohit Prativadi 1975. "Development and application of saturable absorbers to femtosecond solid-state laser mode-locking." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29620.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 209-228).
Semiconductor saturable absorbers have had a major impact on the field of ultrashort pulse generation by increasing the stability and reliability of ultrashort pulse lasers, making them more useful in many applications. These versatile devices can be grown both epitaxially with molecular beam epitaxy and non-epitaxially using RF sputtering. In this thesis, the development and application of both types of saturable absorbers to self-starting mode-locking in solid-state lasers was examined. The first part of this thesis describes the use of an epitaxially grown saturable Bragg reflector to mode-lock an extended cavity femtosecond Cr:LiSAF laser. Inexpensive single mode diodes were used as a pump source and a multi-pass cavity was used to lower the laser repetition rate. Pulses with durations of 39 fs and energies of 0.75 nJ were generated at an 8.6 MHz repetition rate. These pulse energies and durations are comparable to those produced from commercially available Ti:sapphire lasers that have a significantly higher cost. The second part of this thesis explored the further development and application of non-epitaxially grown semiconductor-doped silica films. A novel pump-probe system with independent pump and probe wavelength tunability from 700 to 1000 nm and a time resolution of 17 fs was developed for device characterization. The linear and nonlinear optical properties of InAs-doped silica films deposited by RF sputtering were characterized as a function of fabrication parameters, including nanocrystallite size, pump and probe wavelength relative to the absorption edge, and rapid thermal annealing temperature. Guidelines for the optimization of semiconductor-doped silica films for saturable absorber applications were extracted from the experimental data.
(cont.) Large nanocrystallites, high annealing temperatures, and an operating wavelength close to the absorption edge were found to optimize saturable absorber performance, with a low saturation fluence of 640 pJ/cm2 obtained at 1.54 grm. These saturable absorber devices were then designed to self-start mode-locking in a Cr:forsterite laser, obtaining self-starting 25 fs pulses with 91 nm bandwidth at 1.3 gm. These versatile devices can be designed for any solid-state laser system using the guidelines developed in this work and have the potential to replace epitaxially grown saturable absorbers in many applications.
by Rohit Prativadi Prasankumar.
Ph.D.
17
Reed, Mark W. (Mark Wilbert). "A steady-state L-mode tokamak fusion reactor : large scale and minimum scale." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58088.
Повний текст джерелаАнотація:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, June 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 69-70).
We perform extensive analysis on the physics of L-mode tokamak fusion reactors to identify (1) a favorable parameter space for a large scale steady-state reactor and (2) an operating point for a minimum scale steady-state reactor. The identification of the large scale parameter space is part of the 2008 MIT Nuclear Systems Design Project, which also includes sustainability and economic optimizations to identify a plausible operating point for a large scale (a 14 m major radius) hydrogen production reactor dubbed HYPERION. Due to the potentially prohibitive capital cost (a $50 billion) and exorbitant thermal power (a 35 GWth) of HYPERION, we identify a conservative estimate for the minimum scale of a similar steady-state L-mode reactor of approximately 7.5 meters, half the size of HYPERION and only 20% larger than ITER. This minimum scale reactor would require an on-coil magnetic field of a 16 T and a blanket power density of ~ 5 MW/m 2 . It would produce 7 GWth of power with a power gain of 30, and it would operate far from all stability and confinement limits. To confirm the viability of this operating point, we perform various 1-D calculations. The crucial advantage of a steady-state (or fully non-inductive) reactor is that it is not limited by flux swing and can operate continuously, recharging its solenoid during operation. The crucial advantages of L-mode are that it avoids instabilities associated with edge localized modes (ELMs) and that it allows volumetric heating in the mantle due to the absence of a pedestal. Steady-state L-mode tokamak reactors could be the future of controlled fusion research and even play an important role in meeting the world's clean energy needs.
by Mark Reed.
S.B.
18
Robinson, Karen E. (Karen Elizabeth) 1980. "Stabilization of passively mode locked solid-state lasers by use of electronic feedback." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87894.
Повний текст джерелаАнотація:
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 51-52).
by Karen E. Robinson.
M.Eng.
19
Majdabadi, Abbas. "Investigation and development of mode-locking techniques of diode pumped solid-state lasers." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/399138/.
Повний текст джерелаАнотація:
Development of diode laser pumped mode-locked sources for use as short pulse oscillators for chirped pulse amplification (CPA) experiments using the VULCAN Nd:glass laser has been investigated. To achieve subpicosecond pulses we studied the performance of a recently reported laser crystal, NdxLa1-xMgAl11O19 (Nd:LMA). Using an active mode-locking technique (frequency modulation, or FM mode-locking) bandwidth-limited pulses of 16 W peak power and 14 psec duration were obtained. The pump source was a 0.5 W single stripe diode-laser. In order to obtain sub-picosecond pulses it was necessary to pump the Nd:LMA crystal with higher pump powers and use the more powerful mode-locking technique of additive-pulse mode-locking (APM). A detailed discussion is given of the performance of the Nd:LMA laser pumped with high power diode-lasers and also the pumping and cavity configurations which lead to successful laser operation. In free running operation up to 560 mW and 1.1 W output power was achieved in single and multi mode operation respectively when the crystal was pumped with a 3 W and two 3 W diode-lasers. A brief study is also made of the aspects of the thermal effects, such as thermal lensing and thermally induced birefringence, which may affect the laser performance. Both the Fabry-Perot and Michelson additive-pulse mode-locking configurations were used, and are discussed in detail. With the Fabry-Perot set up, transform-limited pulses of 420 fsec duration were obtained. The average output power was 18 mW, corresponding to an energy per pulse of 0.19 nJ. In the Michelson arrangement the average output power was 120 mW with nearly the same pulse duration which corresponds to a pulse energy of 1.6 nJ. The use of the additive pulse mode-locked laser-diode-pumped Nd:LMA laser as a seed source for the VULCAN Nd:glass amplifier system at the Rutherford Appleton Laboratory is discussed. Use of this seed source allowed the achievement of extremely high peak power (30 TW) sub-picosecond (800 fsec) pulses from this amplifier system. We also present detailed measurements of the main characteristics of this laser.
20
Seger, Kai. "Compact solid-state lasers in the near-infrard and visible spectral range." Doctoral thesis, KTH, Laserfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121976.
Повний текст джерелаАнотація:
The subject of this thesis is the exploration of new concepts for compact solid-state lasers in the visible and near-infrared spectral range using new components such as volume Bragg gratings for wavelength stabilisation and wavelength tuning. Also single-walled carbon nanotubes for mode-locking and Q-switching of lasers have been studied.We have developed a new method for the tuning of solid-state lasers by replacing a dielectric mirror with a transversally chirped volume Bragg grating, which allows smooth wavelength tuning without additional elements inside the laser cavity. The result is a more compact laser, since the tuning mechanism and output coupler are incorporated in one component. Another benefit is an increased efficiency, since additional elements inside the cavity will always add to the total loss of the laser. This has been demonstrated for a broadband ytterbium laser around 1 µm and a single-longitudinal-mode Nd:YVO4 laser around 1.06 µm. A volume Bragg grating has also been used to construct an efficient, narrow-linewidth ytterbium fiber laser and the employment of a volume Bragg gratingas the pump mirror of a solid-state laser for frequency-doubling has been investigated. Both lasers represent a practical solution, eliminating the use of additional intracavity elements. Second-harmonic generation is an efficient way to access the visible spectral range using diode-pumped solid-state lasers. However, these lasers can suffer from large amplitude fluctuations, which has been analyzed in more detail for an optically-pumped semiconductor disk-laser and a volume Bragg grating locked ytterbiumlaser. The control of those amplitude fluctuations is very important, since many applications like fluorescence microscopy require a laser with a constant output power and as little noise as possible. In addition to this, we have demonstrated, that saturable absorbers based on quan-tum dots and carbon nanotubes can be used to mode-lock compact laser at a wavelength around 1.03 µm. Those lasers have many interesting applications incommunications, clock generation, metrology and life sciences.QC 20130507
21
Aitken, Victor C. (Victor Charles) Carleton University Dissertation Engineering Systems and Computer. "Sliding mode state estimation for nonlinear discrete-time systems; applications in image sequence analysis." Ottawa, 1995.
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22
Nguyen, Van Liem. "Modeling and control coordination of power systems with FACTS devices in steady-state operating mode." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0036.
Повний текст джерелаАнотація:
This thesis is devoted to the development of new models for a recently-implemented FACTS (flexible alternating current transmission system) device, the unified power flow controller (UPFC), and the control coordination of power systems with FACTS devices in steady-state operating mode. The key objectives of the research reported in the thesis are, through online control coordination based on the models of power systems having FACTS devices, those of maximising the network operational benefit and restoring system static security following a disturbance or contingency. Based on the novel concept of interpreting the updated voltage solutions at each iteration in the Newton-Raphson (NR) power-flow analysis as dynamic variables, the thesis first develops a procedure for representing the unified power flow controllers (UPFCs) in the steady-state evaluation. Both the shunt converter and series converter control systems of a UPFC are modeled in their dynamical form with the discrete time variable replaced by the NR iterative step in the power-flow analysis. The key advantage of the model developed is that of facilitating the process of UPFC constraint resolution during the NR solution sequence. Any relative priority in control functions pre-set in the UPFC controllers is automatically represented in the power-flow formulation. Although the developed UPFC model based on the dynamic simulation of series and shunt converter controllers is flexible and general, the number of NR iterations required for convergence can be large. Therefore, the model is suitable mainly for power system planning and design studies. For online control coordination, the thesis develops the second UPFC model based on nodal voltages. The model retains all of the flexibility and generality of the dynamic simulation-based approach while the number of iterations required for solution convergence is independent of the UPFC controller dynamic responses. Drawing on the constrained optimisation based on Newtons method together with the new UPFC model expressed in terms of nodal voltages, a systematic and general method for determining optimal reference inputs to UPFCs in steady-state operation is developed. The method is directly applicable to UPFCs operation with a high-level line optimisation control (LOC) for maximising the network operational benefit. By using a new continuation technique with adaptive parameter, the algorithm for solving the constrained optimisation problem extends substantially the region of convergence achieved with the conventional Newtons method. Having established the foundation provided by the comprehensive models developed for representing power systems with FACTS devices including the UPFC, the research, in the second part, focuses on real-time control coordination of power system controllers, with the main purpose of restoring power system static security following a disturbance or contingency. At present, as the cost of phasor measurement units (PMUs) and wide-area communication network is on the decrease, the research proposes and develops a new secondary voltage control where voltages at all of the load nodes are directly controlled, using measured voltages.
23
Birge, Jonathan R. (Jonathan Richards). "A preconditioned Newton-Krylov method for computing steady-state pulse solutions of mode-locked lasers." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42454.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2008.Includes bibliographical references (p. 47-48).
We solve the periodic boundary value problem for a mode-locked laser cavity using a specially preconditioned matrix-implicit Newton-Krylov solver. Solutions are obtained at least an order of magnitude faster than with dynamic simulation, the standard method. Our method is demonstrated experimentally on a one-dimensional temporal model of an eight femtosecond mode-locked laser operating in the dispersion-managed soliton regime. Our solver is applicable to finding the steady-state solution of any nonlinear optical cavity with moderate self phase modulation, such as those of solid state lasers, and requires only a model for the round-trip action of the cavity. We conclude by proposing avenues of future work to improve the method's convergence and expand its applicability to lasers with higher degrees of cavity nonlinearity. Our approach can be extended to spatio-temporal cavity models, potentially allowing for the first feasible simulation of the full dynamics of Kerr-lens mode locking.
by Jonathan R. Birge.
S.M.
24
Reed, Mark Wilbert. "A fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with natural uranium." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/76535.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 215-218).
The most prevalent criticism of fission-fusion hybrids is simply that they are too exotic - that they would exacerbate the challenges of both fission and fusion. This is not really true. Intriguingly, hybrids could actually be more viable than stand-alone fusion reactors while mitigating many challenges of fission. This work develops a conceptual design for a fission-fusion hybrid reactor in steady-state L-mode tokamak configuration with a subcritical natural or depleted uranium pebble bed blanket. A liquid lithiumlead alloy breeds enough tritium to replenish that consumed by the D-T fusion reaction. Subcritical operation could obviate the most challenging fuel cycle aspects of fission. The fission blanket augments the fusion power such that the fusion core itself need not have a high power gain, thus allowing for fully non-inductive (steady-state) low confinement mode (L-mode) operation at relatively small physical dimensions. A neutron transport Monte Carlo code models the natural uranium fission blanket. Maximizing the fission power while breeding sufficient tritium allows for the selection of an optimal set of blanket parameters, which yields a maximum prudent fission power gain of 7.7. A 0-D tokamak model suffices to analyze approximate tokamak operating conditions. If the definition of a "reactor" is a device with a total power gain of 40, then this fission blanket would allow the fusion component of a hybrid reactor with the same dimensions as ITER to operate in steady-state L-mode very comfortably with a fusion power gain of 6.7 and a thermal fusion power of 2.1 GW. Taking this further can determine the approximate minimum scale for a steady-state L-mode tokamak hybrid reactor, which is a major radius of 5.2 in and an aspect ratio of 2.8. This minimum scale device operates barely within the steady-state L-mode realm with a thermal fusion power of 1.7 GW. This hybrid, with its very fast neutron spectrum, could be superior to pure fission reactors in terms of breeding fissile fuel and transmuting deleterious fission products. It could operate either as a breeder, producing fuel for pure fission reactors from natural or depleted uranium, or as a deep burner, fissioning heavy metal and transmuting waste with a cycle time of decades. Despite a plethora of potential functions, its primary mission is deemed to be that of a deep burner producing baseload commercial power with a once-through fuel cycle. Although hybrids are often purported a priori to pose an elevated proliferation risk, this reactor breeds plutonium that could actually be more proliferation-resistant than that bred by fast reactors. Furthermore, a novel method (the "variable fixed source method") can maintain constant total hybrid power output as burnup proceeds by varying the neutron source strength. As for engineering feasibility, basic thermal hydraulic analysis demonstrates that pressurized helium could cool the pebble bed fission blanket with a flow rate below 10 m/s. The Brayton cycle thermal efficiency is 41%. This device is dubbed the Steady-State L-Mode Non-Enriched Uranium Tokamak Hybrid (SLEUTH). The purpose of this work is not any sort of elaborate design, but rather the exploration of an idea coupled with corroborating numerical analysis. At this point in the hybrid debate, viable conceptual designs are persuasive while intricate build-ready designs are superfluous. This work conceives such a conceptual design, demonstrates its viability, and will perhaps, incidentally, spur a profusion of pro-fusion sentiment!
by Mark Wilbert Reed.
S.M.
25
Eibna, Halim Md Zubaer. "Passively mode-locked picosecond Nd:KGW laser with low quantum defect diode pumping." Astro Ltd, 2016. http://hdl.handle.net/1993/31913.
Повний текст джерелаАнотація:
Solid-state lasers are capable of providing versatile output characteristics with greater flexibility compared to other popular laser systems. Lasing action has been achieved in many hundreds of solid-state media, but Nd-ion doped gain media are widely used to reach high power levels with short pulses.
In this work, commercially available Nd:KGW crystal served as a gain medium to achieve pulsed operation at 1067 nm. This laser crystal offers large stimulated emission crosssection and gain bandwidth which facilitates generation of high peak power pulses in the picosecond regime. The KGW crystal is monoclinic and biaxial in structure, and anisotropic in its optical and thermal properties. Due to poor thermal conductivity, this crystal can be operated within a limited power range before crystal fracture takes place. To reduce the amount of heat deposited in the gain media, we introduced a new pumping wavelength of 910 nm which reduces the quantum defect by more than 45%.
Continuous-wave laser operation was optimized to operate in mode-locked regime. In order to achieve short light pulses from the continuous-wave laser, one of the end mirrors was replaced by a semiconductor saturable absorber mirror (SESAM) to generate 2.4 ps pulses at a repetition rate of 83.8 MHz. An average output power of 87 mW was obtained at lasing wavelength of 1067 nm and the beam was nearly diffraction limited with M^2 < 1.18. The peak power of the generated pulses was 427 W and energy of each pulse was >1 nJ. Pumping the crystal at longer wavelength (910 nm) reduced the thermal lensing of the crystal by half when compared to conventional pumping at shorter wavelength (808 nm). To the best of our knowledge, this is the first time passive mode-locking of a Nd:KGW laser was explored using the pump wavelength at 910 nm.February 2017
26
Sholtis, Tadd. "One helluva roar : US Air Force public communication since 1942 /." Maxwell AFB, Ala. : School of Advanced Air and Space Studies, 2008. https://www.afresearch.org/skins/rims/display.aspx?moduleid=be0e99f3-fc56-4ccb-8dfe-670c0822a153&mode=user&action=downloadpaper&objectid=f6ea7bb1-2b97-4d90-8b90-1cf4474c5a7c&rs=PublishedSearch.
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Ablay, Gunyaz. "Sliding Mode Approaches for Robust Control, State Estimation, Secure Communication, and Fault Diagnosis in Nuclear Systems." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354551858.
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Brunzell, Martin. "Free-Space Dark Pulse Mode-Locked Laser." Thesis, KTH, Tillämpad fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296524.
Повний текст джерелаАнотація:
While the development of bright pulses produced in free space devices can be found in a large set of applications and research equipment all over the world. The production of dark pulses in a free-space device has not been shown prior to this work. In this work a method of producing free space mode-locked laser in a straight laser cavity using intra-cavity loss induced by periodic nonlinear interactions mediated by a mode-locked source. We are able to show the existence of a dark pulse propagating inside of the cavity. An extensive analysis of the generation of the dark pulse is made using a homemade cross correlator. A symmetric dark pulse with a 10 ps width is achieved with a 90% modulation depth. This work will be used in a continued project involving passive two-color pulse synchronization.Framtagningen av ljusa pulser i kristall baserade lasrar finns i en stor utsträckning av tillämpningar inom forskning och industri. Utvecklandet av mörkpulskällor i kristall baserade kaviteter har till vår kunskap inte tagits fram. I detta arbete presenteras en metod att utveckla en modlåst mörkpuls laser i en rak kavitet som utnyttjar intrakavitär förlust som periodiskt induceras av en ickelinjär interaktion som styrs av en ljus modlåst källa. Vi kan visa att en mörk puls propagerar inuti kaviteten. En utförlig analys och experiment med hjälp av en hemagjord korskorrelator belyser hur den mörka pulsen kan formas. En symmetrisk mörk puls formas med en 10 ps bredd och över 90 % modulations djup. Detta arbete kommer användas i ett framtida projekt inom passiv tvåfärgs puls synkronisation.
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Oh, Yunje. "Prediction of steady state response in dynamic mode atomic force microscopy and its applications in nano-metrology." Columbus, Ohio : Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1135222817.
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Senkel, Luise [Verfasser]. "Sliding Mode Techniques for Robust Control, State Estimation and Parameter Identification of Uncertain Dynamic Systems / Luise Senkel." Aachen : Shaker, 2018. http://d-nb.info/1159833230/34.
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Oh, Yunje. "Prediction of steady state response in dynamic mode atomic force microscopy and its applications in nano-metrology." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135222817.
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32
Ayachit, Agasthya. "Steady-State and Small-Signal Modeling of A-Source Converter." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1534187954423628.
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33
Zhao, Haitao. "Powerful diode-pumped ultrafast solid-state laser oscillators based on bulk Yb:KGd(WO4)2 crystals." IOP Publishing, 2010. http://hdl.handle.net/1993/30413.
Повний текст джерелаАнотація:
Yb-ion doped gain media have become the material of choice for reliable generation of ultrashort pulses at wavelength around 1 μm. At present, however, operation at high average power (>1 W) with sub-100 fs pulses still remains challenging. The efforts of developing an Yb-ion oscillator towards this goal, therefore, are the main focus of this thesis.
In this work, the Yb:KGd(WO4)2 (Yb:KGW) crystals were chosen to serve as the gain media. To achieve high power operation, two fundamental issues have been carefully considered: 1) a new pumping scheme was proposed to alleviate the thermal issues in the Yb:KGW crystals; 2) a new method was introduced to characterize intracavity losses in the broadband Yb-ion oscillators. As a side effect observed during the optimization of the CW operation, simultaneous two-wavelength emission was also discussed.
With the knowledge and experimental understanding of the fundamental issues in laser oscillators operated in the continuous-wave regime, the next step of this work demonstrated their operation in a pulsed regime. The dual action of the Kerr-lens and saturable absorber (KLAS) mode locking was proposed in this work and resulted in greatly enhanced laser performance. The laser delivered pulses with 67 fs duration at a repetition rate of 77 MHz. The average output power reached 3 W, which, to the best of our knowledge, is the highest average output power produced to date from the Yb-ion based bulk lasers with such a short pulse duration. The scalability of pulse energy and peak power was also demonstrated by reducing the repetition rate to either 36 MHz or 18 MHz. The cavity with the latter repetition rate produced 85 fs pulses with the pulse energy up to 83 nJ, which corresponds to a peak power as high as 1 MW.
As required by many biomedical applications, the wavelength of the generated pulses (~1 μm) can be tuned in the near-infrared region by coupling them into an optical parametric oscillator (OPO). The feasibility of this approach was demonstrated in the last part of this thesis, through a thorough theoretical analysis of two OPO materials suitable for excitation at 1.04 μm.
34
Wang, Yicheng [Verfasser]. "Passive mode-locking of 2-μm solid-state lasers : Towards sub-10 optical cycle pulse generation / Yicheng Wang". Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1147758271/34.
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35
Firdaus, Ahmad Riyad. "Design of sliding mode-based nonlinear control systems with nonlinear full-order state observers for underactuated coupled systems." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20897/.
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36
Piloyan, Torgom. "How does the ethnic kinship affect the mode of provided external support in an intra-state armed conflict?" Thesis, Uppsala universitet, Institutionen för freds- och konfliktforskning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-361641.
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37
Paleocrassas, Alexander Grant. "Feasibility Investigation of Laser Welding Aluminum Alloy 7075-T6 through the use of a 300 W, Single-Mode, Ytterbium Fiber Optic Laser." NCSU, 2005. http://www.lib.ncsu.edu/theses/available/etd-08062005-173047/.
Повний текст джерелаАнотація:
Aluminum alloys are important structural materials because of their high strength to weight ratio. Unfortunately, due to their high reflectivity and complexity in heat treatment, aluminum alloys are some of the hardest metals to be laser welded successfully and very high laser power is usually required. In this study, the feasibility of using a 300 W, Single-Mode, Ytterbium Fiber Optic Laser for aluminum welding is investigated. The objective is to explore an application area with low power and low welding speed. As the fiber laser offers much better beam quality (M2 less than 1.05), the results show that, with proper control of welding parameters, the success of aluminum welding can be achieved at considerably low laser power with minimal formation of typical welding defects (porosity, cracking etc.). However, the focusing becomes highly critical as exceeding a certain power density can lead to defects such as blowholes and porosity. The deepest penetration achieved was just over 1 mm at 300W and 2 mm/sec. Other welding processes achieve about three to four times as much penetration at the expense of seven times more power. Further development of this process can lead to a more efficient use of power.
38
Durmaz, Burak. "Sliding Mode Control Of Linearly Actuated Nonlinear Systems." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610666/index.pdf.
Повний текст джерелаАнотація:
This study covers the sliding mode control design for a class of nonlinear systems, where the control input affects the state of the system linearly as described by (d/dt)x=A(x)x+B(x)u+d(x). The main streamline of the study is the sliding surface design for the system. Since there is no systematic way of designing sliding surfaces for nonlinear systems, a moving sliding surface is designed such that its parameters are determined in an adaptive manner to cope with the nonlinearities of the system. This adaptive manner includes only the automatic adaptation of the sliding surface by determining its parameters by means of solving the State Dependent Riccati Equations (SDRE) online during the control process. The two methods developed in this study: SDRE combined sliding control and the pure SDRE with bias terms are applied to a longitudinal model of a generic hypersonic air vehicle to compare the results.
39
Gold, Carrie Elizabeth. "Exploring the Resting State Neural Activity of Monolinguals and Late and Early Bilinguals." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6671.
Повний текст джерелаАнотація:
Individuals who speak more than one language have been found to enjoy a number of benefits not directly associated with the use of the languages themselves. One of these benefits is that bilingual individuals appear to develop symptoms of dementia 4-5 years later than comparable individuals who speak just one language. Studies on this topic, however, do not consistently account for factors including if the individual learned their second language as a child or later in life, or their language proficiency. In an attempt to more carefully examine these variables, this study looks at structural and resting-state functional MRI scans of the default mode network, English and Spanish (where applicable) proficiency, language background, and demographics of young healthy adults who fall into one of three groups: early bilinguals, late bilinguals, and monolinguals. Of the three groups, late bilinguals were found to have a small but statistically significantly higher level of connectivity compared with early bilinguals in the region of the medial prefrontal cortex; patterns found examining number of languages and language proficiency in relation to functional connectivity and research group also supported this finding. These results indicate studying a language after adolescence could provide neuroprotective benefits of a nature that could potentially help delay symptoms of dementia. Age, gender, ethnicity, level of education, English language proficiency, and Spanish language use did not result in statistically significant findings, the latter of which challenges using frequency of language use to define bilingualism.
40
Rytty, R. (Riikka). "Resting-state functional MRI in behavioral variant of frontotemporal dementia." Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526211336.
Повний текст джерелаАнотація:
Abstract Frontotemporal lobar degeneration (FTLD) is the second most common neurodegenerative disease leading to early-onset dementia with an estimated worldwide prevalence of 10 to 30 cases per 100000 individuals in the age group of 46 to 65 years. Behavioral variant frontotemporal dementia (bvFTD) is the most common FTLD subtype. It is characterized by a progressive deterioration of behavior and personality as well as executive dysfunction. In Finland, almost 50 % of familial FTLD cases are attributable to the C9ORF72 mutation. bvFTD is associated with a characteristic pattern of brain atrophy detectable in structural MRI. However, these changes are typically not visible in the early stages of the disease. Resting-state functional MRI (RS-fMRI) is being increasingly used to evaluate changes in functional connectivity within neuronal networks in the brain but only a few RS-fMRI investigations of bvFTD patients have been published with inconsistent results. The object of this thesis was to investigate functional connectivity changes detected in the salience (SLN) and default mode networks (DMN) in bvFTD. Another aim was to clarify the role of other cognitive resting-state networks in this disease. A cohort of 26 bvFTD patients was studied, with 8 of these patients carrying the C9ORF72 expansion. Connectivity changes were detected in multiple clinically relevant cognitive networks. Decreased functional connectivity was observed in the SLN, which is associated with guiding of behavior. Increased activity was present in the DMN and the dorsal attention network (DAN). In C9ORF72 associated bvFTD, there was an abnormal linkage detected between the DMN and the thalamus. Currently, fMRI is generally used as a research tool and in a group setting. Different study methods have been used in the literature and also in the studies of this thesis, the analysis procedures differed to some extent. The variety of analysis methods may explain the heterogeneity in fMRI findings in bvFTD patients. There is a need for standardization of the fMRI methodology, larger study groups and also in the future the methodology should be improved so that single patient analysis would provide results to allow a confident diagnosis of this diseaseTiivistelmä Otsa-ohimolohkorappeuma (Frontotemporal lobar degeneration, FTLD) on toiseksi yleisin etenevä dementiaan johtava sairaus, joka ilmaantuu usein jo työikäisenä. Otsalohkodementia on otsa-ohimolohkorappeuman yleisin alamuoto, jonka oireisto painottuu persoonan ja käyttäytymisen muutoksiin sekä toiminnan ohjauksen ongelmiin. Suomessa C9ORF72-toistojaksomutaatio selittää lähes 50 % perinnöllisistä otsa-ohimolohkorappeumista. Aivojen rakenteellisella magneettikuvauksella (MK) voidaan havaita rakenteellisia muutoksia, jotka ilmaantuvat kuitenkin vasta taudin edettyä vaikeampaan vaiheeseen. Aivojen lepotilan toiminnallinen magneettikuvaus (TMK) mahdollistaa aivojen hermoverkkojen toiminnan eli konnektiviteetin kartoituksen. Aiemmin TMK:a on tutkittu esim. Alzheimerin taudissa. Otsalohkodementiassa TMK:sta on julkaistu ainoastaan yksittäisiä tutkimuksia ja tulokset ovat olleet osin ristiriitaisia. Väitöskirjatutkimuksen tarkoituksena on ollut selvittää valve-lepotilan hermoverkossa ja olennaisen tunnistavassa hermoverkossa tapahtuvia muutoksia otsalohkodementiaa sairastavilla potilailla. Toisena tavoitteena on ollut tutkia muissa kognitiivisissa hermoverkoissa tapahtuvia muutoksia. Otsalohkodementiaa sairastaville potilaille (n= 26) sekä ikä- ja sukupuolivakioiduille kontrolleille on tehty kliininen tutkimus ja rakenteellinen sekä toiminnallinen aivojen magneettikuvaus. Kahdeksalla potilaalla todettiin C9ORF72-toistojaksomutaatio. Useiden kognitiivisten hermoverkkojen toiminnassa havaittiin muutoksia, jotka korreloivat potilaiden kliinisiin oireisiin. Alentunutta konnektiviteettia todettiin olennaisen tunnistavassa hermoverkossa, joka osallistuu käyttäytymisen säätelyyn. Lisääntynyttä konnektiviteettia esiintyi valve-lepotilan hermoverkossa ja tarkkaavaisuus hermoverkossa. Potilailla, joilla on C9ORF72-mutaatio, havaittiin epänormaali yhteys valve-lepotilan hermoverkon ja talamuksen välillä. TMK:ta käytetään tällä hetkellä lähinnä tutkimustyökaluna. Analyysityökaluissa on ollut vaihtelevuutta eri julkaisuissa ja osin myös tämän väitöskirjan osatöissä. Julkaistut TMK-löydökset otsalohkodementiassa ovat osin ristiriitaisia ja se saattaa selittyä erilaisilla analyysimenetelmillä. Metodologiaa tulisi standardisoida ja lisäksi tarvitaan suurempia potilasryhmiä ja menetelmien kehittämistä, jotta TMK:n käyttö yksilötason kliinisessä diagnostiikassa olisi jatkossa mahdollista
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Thorette, Aurélien. "Synchronization dynamics of dual-mode solid-state and semiconductor DFB lasers under frequency-shifted feedback : applications to microwave photonics." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S059/document.
Повний текст джерелаАнотація:
Le contrôle de la différence de fréquence entre deux lasers est un défi transversal à de nombreux domaines de la photonique, que ce soit dans un but de génération hétérodyne d'un battement micro-onde de grande pureté, ou pour des expériences de métrologie ou de télécommunication. L'avancée des connaissances sur la dynamique de lasers soumis à divers couplages a permis le développement de méthodes de stabilisation basées sur l'injection optique. Nous étudions ici théoriquement et expérimentalement un mécanisme appelé réinjection décalée en fréquence (RDF), qui permet dans des situations variées de contrôler précisément la différence de fréquence entre deux lasers. Dans un premier temps, la méthode RDF est appliquée à un laser à état solide bi-polarisation bi-fréquence Nd:YAG afin de verrouiller en phase ses deux modes de polarisation orthogonaux. Le développement d'un modèle type «rate equations» en bonne adéquation avec les expériences a aussi permis de mettre en lumière un certain nombre de régimes de synchronisation partielle dits de phase bornée. De plus, nous montrons que cet état peut subsister en présence d'oscillations chaotiques de l'intensité et de la phase. Le comportement du laser sous RDF est étudié pour différentes valeurs du désaccord de fréquence, du taux d'injection, du retard éventuel, et du couplage inter-modes. Enfin, la nécessité d'inclure un couplage phase-amplitude (facteur de Henry non-nul) dans le modèle a mené au développement d'une méthode pour mesurer ce coefficient habituellement négligé dans les lasers solides. Le mécanisme de stabilisation par RDF est ensuite appliqué à un composant semiconducteur original contenant deux lasers DFB sur InP. Malgré une plus grand complexité du schéma de couplage, et la présence de retards effectifs importants, il reste possible de synchroniser en phase ces lasers. Des bandes d'accrochages liées au retard sont observées, et reproduites à l'aide d'un modèle numérique. Ce dernier permet aussi de déterminer les conditions de fonctionnement minimisant l'influence de paramètres expérimentaux non maîtrisés. Enfin, ce système, permettant de contrôler une phase micro-onde sur porteuse optique, peut être intégré dans une boucle résonante de type oscillateur opto-électronique (OEO) qui ne nécessite pas de référence externe. On réalise un oscillateur micro-onde sur porteuse optique auto-référencé, à bande latérale unique, ayant des performances encourageantes. Dans ce cadre, il semble que la plupart des techniques développées pour les OEO puissent être réinvestiesThe control of the frequency difference between two lasers is a cross-cutting challenge in many fields of photonics, either for the generation of high-purity heterodyne microwave beatnotes, or in metrology and telecommunication experiments. The advances of the comprehension of laser dynamics under various couplings has allowed to develop stabilization methods based on optical injection. We study here theoretically and experimentally a mechanism called frequency-shifted feedback (FSF), which allows to precisely control the frequency difference between two lasers in several situations.First, the FSF method is applied to a dual-frequency dual-polarization solid-state Nd:YAG laser, in order to lock the phases of its two orthogonal polarization modes. A model of rate equations is used to precisely describe the experiment, and allows to highlight partial "bounded phase" synchronization regimes. Furthermore, we show that in some cases this synchronization can subsist even with chaotic oscillations of the intensity and phase. The behavior of the laser under FSF is studied for varying values of the frequency detuning, injection rate, possible injection delay, and mode coupling in the active medium. Finally, we find that the inclusion of a phase-amplitude coupling (non-zero linewidth enhancement factor) is needed in the model to account for experimental observation. This leads to the development of an ad-hoc technique to measure the low value of this usually neglected factor in solid-laser lasers.The FSF stabilization mechanism is then applied to a custom semiconductor component embedding two DFB lasers overs InP. In spite of a more complex coupling scheme and the large effective delays into play, phase locking of the two lasers is possible. Due to the delay, locking bands appear when the detuning changes, and this behavior can be replicated using a numerical model. This model also permit to determine working conditions minimizing the influence of uncontrolled experimental optical feedback phases. Finally, as this system allows to control a microwave phase over an optical carrier, it can be integrated in a resonant loop not unlike an opto-electronic oscillator (OEO). We realized an oscillator generating a self-referenced, single sideband microwave signal over an optical carrier, with encouraging phase noise performances. In this case, it seems that most of the techniques that exist for standard OEO can be reused
42
Chwan-Horng, Goan, and 管傳鴻. "Complete State Integral Sliding Mode Control." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/87257380501949220404.
Повний текст джерелаАнотація:
碩士中原大學
電機工程學系
87
A complete state integral sliding mode control is proposed in this paper. The complete state means the whole process or response of the controlled state. The sliding mode that can occur from the very beginning is done through the combination of three steps, the proper choice of initial values in sliding functions, the linear state feedback, and the integral feedback of system dynamics. The proposed sliding mode can solve the robust problem of classical sliding mode control during the reaching mode in which the high gain feedback control is applied. Lyapunov’s method is used to ensure the existence of sliding surface and result in the design of relative control inputs. The stability analysis is perfectly improved through the redesign of control gains and the transform of the sliding functions. The proposed method is not only a simple control method, but also gives a generalized form in order to apply upon the systems that encounter uncertainties and need the reduction of perturbations and the assurance of stability from the very beginning. It can be applied either on linear or nonlinear systems. The simulations are performed for tracking control of a permanent magnetic synchronous motor drive system and a two-link manipulator. The results of simulations give illustrative examples that demonstrate expected satisfactory performances. The proposed method is not only of the lowest constraint of generalization, but also suitable to a wide scope of application areas including control in linear, nonlinear, single-input and multi-input systems. It can be utilized together with basic or conventional methodologies and gives choices of design methods for different control constraints or requirements. Integration of various control methods is just a good feature of that proposed.
43
Liu, Tzu-Ming. "High Repetition-rate Mode-locked Solid-state Lasers." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2007200415234900.
Повний текст джерела
44
Tian, Jining. "Forwarding state reduction for sparse mode multicast communication." Thesis, 1997. http://hdl.handle.net/2429/6595.
Повний текст джерелаАнотація:
Reducing forwarding state overhead of multicast routing protocols is an important
issue towards a scalable global multicast solution. In this paper, we propose
a new approach, Dynamic Tunnel Multicast, which utilizes dynamically established
tunnels on unbranched links of a multicast distribution tree to eliminate unnecessary
multicast forwarding states. Analysis and simulation results show promising
reduction in the state overhead of sparse mode multicast routing protocols.
45
Liu, Tzu-Ming, and 劉子銘. "High Repetition-rate Mode-locked Solid-state Lasers." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/57715888223062854001.
Повний текст джерелаАнотація:
博士國立臺灣大學
光電工程學研究所
92
High repetition rate (HRR) mode-locked solid-state lasers have increasing importance in many applications. In optical communications, it’s a potential source for the hybrid wavelength-division multiplexed (WDM) and optical time-division multiplexed (OTDM) systems. In frequency metrology, HRR lasers can increase the resolution and signal to noise ratio (SNR) of frequency measurement. In the domain of measuring applications, HRR lasers reduce the optical pulse energy while maintaining a high average power, which is important for achieving high SNR. Although HRR mode-locked lasers are advantageous to these applications, there are still some hindrances for better development. In WDM/OTDM hybrid communication system, it still lacks a high power HRR multi-channel source to exploit the spectral domain resources. In frequency metrology, there are still some spectral black holes corresponding to specific transition level of atoms or molecules. Besides, once a HRR mode-locked solid-state laser is built, the repetition rate can’t be easily multiplied without changing the cavity geometry. In this thesis, we circumvented these hindrances and made HRR mode-locked lasers more promising and more flexible in many HRR applications. Complete information of HRR pulses can be characterized with developed auxiliary technique. For the problem of spectral black holes, we employed frequency conversion such as second harmonic generation (SHG) to achieve HRR femtosecond lasers at red and blue wavelengths. Based on an 110-MHz Cr:forsterite laser, we first used intracavity frequency doubling to obtain HRR femtosecond pulses around 620-nm. Red pulses with 170-fs pulse width were obtained with 24-mW average power. For the frequency conversion of short cavity length, it’s better to employ external resonant cavity to enhance the conversion efficiency. As a consequence, based on a 2-GHz Ti:sapphire laser, we demonstrated a 2-GHz-repetition-rate high-power femtosecond blue sources for the first time. Pumped by the 2-GHz Ti:sapphire laser with 740-mW output power, 150-mW femtosecond pulses at 409nm can be efficiently generated from the resonant cavity. For the development of high power WDM/OTDM sources, we exploit the broadband nature of HRR femtosecond lasers and demonstrated first high power HRR multi-channel sources. By inserting an intracavity etalon into a HRR femtosecond Cr:forsterite laser, 12 phase-locked channels with 9–19-ps pulse width near 1230 nm could be generated. Average output power of 280-mW can be obtained from a single laser oscillator. By tuning the etalon bandwidth, we can shorten the pulse width in a specific channel to 1.8 ps. For the improvement of repetition rate flexibility, we invented an intracavity flat surface technique to multiply the repetition rate. We first built a compact self-started HRR Cr:forsterite laser at 100-MHz for the application of portable clinical use operating around 1230 nm. Instead of prism pairs, double-chirped mirrors were employed to compensate the group delay dispersion of the laser cavity. The laser mode-locking was self-started with the help of a semiconductor saturabe absorber mirror. By adopting an intracaity flat surface with low reflectivity and controlling the ratio of subcavity lengths, the repetition rate of this compact femtosecond Cr:forsterite laser can be multiplied from 100 MHz to 500 MHz in femtosecond regime. Repetition rate higher than 1GHz can also be achieved. Compared with the conventional coupled cavity method, this newly developed technique provides a flexible and phase insensitive way to increase the repetition rate of femtosecond solid-state lasers. For the diagnosis of ultrashort HRR pulses, we developed a new technique. By adding spectral information into triple-optical-autocorrelation measurements, we made the triple-autocorrelation method capable of providing complete knowledge of HRR laser pulses. With the measured temporal intensity of an optical pulse and its corresponding spectral intensity obtained with a spectrometer, exact intensity and phase variations in time can all be recovered with the Gerchberg-Saxton algorithm through an iterative calculation with an O(n) complexity.
46
Hsieh, Hung Dau, and 謝弘道. "Diode-Pumped Passive Mode-Locked Solid-State Laser：Semiconductor Saturable Absorber(SESAM) versus Nonlinear Mode-Locked." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/81286425317422796073.
Повний текст джерелаАнотація:
碩士國立交通大學
電子物理系
90
The study of Nd:YVO4 and Nd:GdVO4 lasers pumped by a continuous-wave diode laser has increased in recent years. Even though Nd:GdVO4 has superior crystal properties than Nd:YVO4,its efficiency on the diode-end-pumped cw mode-locked laser has never been investigated. In this paper we study and compare the two different gain mediums, Nd:YVO4 and Nd:GdVO4, on the cw mode-locked laser with both the nonlinear mirror (NLM) and semiconductor saturable absorber mirror (SESAM) mechanisms. These two mode-locked mechanisms as well as the ultra-short pulse generation theory will be investigated and presented with the theoretical simulations and experimental results. Physical criteria for the characteristics of both NLM and SESAM will also be developed in this paper. Taking into account the nonlinear effects of nonlinear crystal and SESAM, we intend to modify Dr. Stankov’s theory in NLM cw mode-locked lasers and present new parameters for generating short pulse in SESAM.
47
Yeh, Cheng-Hsuan, and 葉丞軒. "DESIGN OF ADAPTIVE FUZZY SLIDING MODE CONTROLLER WITH STATE OBSERVER." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/46594759813953754610.
Повний текст джерелаАнотація:
碩士大同大學
電機工程研究所
91
In this thesis, an observer-based adaptive fuzzy sliding mode controller for a certain class of unknown nonlinear dynamical system is presented. The total states of the nonlinear system are not to be available for measurement; hence a state observer will be designed to estimate the nonlinear system states. By using an observer-based output feedback control law and adaptive law, the parameters of the adaptive fuzzy sliding mode controller can be tuned based on the Lyapunov stability analyzes. Moreover, we provide a weighting factor, it will be adjusted by the plant knowledge or by the control information, namely, if the plant knowledge is more important and reliable than control information, we should choose a larger factor; otherwise, a smaller factor should be chosen. According to the weighting factor, we can find the control input for the nonlinear system. We apply the adaptive fuzzy sliding controller to control an inverted pendulum system and a Duffing forced oscillation system, the simulation results demonstrate the applicability of the proposed method.
48
Sheu, Chich-Chang, and 許智章. "Mode Degenerate Effects in an End-Pumped Solid State Laser." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/62205390018941650782.
Повний текст джерелаАнотація:
碩士國立交通大學
光電工程研究所
86
In this thesis, we study the mode degenerate effects on the output of a Nd: YVO4 laser end-pumped by a diode laser. When the cavity length is adjusted near the position of mode degeneracy we find an increase in total power, a decrease in the fundamental mode power and the instability in output power along with the emergence of multiple transverse modes. Besides, we also find lower threshold pump power taking place a around these positions. this study shows that the mode degenerate effect should be taken into account in the design of end-pumped solid state lasers.
49
Yu-Pin, Lan, and 藍宇彬. "Research on fundamental mode and high-order transverse modes in diode-pumped solid-state laser." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/74959309637602146423.
Повний текст джерелаАнотація:
博士國立交通大學
光電工程所
91
One issue of this dissertation is to study the influence of pump-to-mode overlap in the slope efficiency and output beam quality in diode end-pumped solid-state lasers. The space-dependent rate equations were employed to analyze the thermal effects in CW and Q-switched end-pumped solid-state lasers. Including the thermal effects into the cavity design, a 30W of TEM00 CW mode output power with good beam quality and near 1 mJ pulse energy in Q switched operation were developed. The other issue of this dissertation is to study the formation of high-order transverse modes in a microchip laser. Experimentally, a technology based on a doughnut pump profile was developed to generate pure Laguerre-Gaussian (LG) TEM*0,l modes. In addition, the dynamics of a solid-state laser sustaining the oscillation of the Laguerre-Gaussian TEM*0,l mode is investigated theoretically and experimentally. On the other hand, a new type of laser transverse modes was demonstrated in an isotropic microchip laser with a doughnut pump profile. The observed transverse modes include elliptic and hyperbolic wave patterns that are analogous to the quantum states of classical trajectories of a 2D harmonic oscillator. Finally, it was found that the transverse pattern of optical vortex lattices could be generated by controlling the transverse mode spacing, the mode size and pump profile.
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Ibrahim, Khaled Z. "Slipstream execution mode for CMP-based shared memory systems." 2003. http://www.lib.ncsu.edu/theses/available/etd-04252003-123737/unrestricted/etd.pdf.
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