Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 72 for “"short pulse"”.
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High power ultra-short pulse Quantum-dot lasers
… and broad tunability. Moreover, broad pulse repetition rate tuning using an external cavity configuration is presented. A high peak power of 17.7 W was generated from the quantum-dot laser as a result of the tapered geometry of the gain section of the laser has led to successful …
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Incoherent short pulse scattering from penetrable geophysical media
A new model for incoherent short pulse scattering from penetrable geophysical media is developed. The model is obtained by assuming that the surface and volume scattered components of the total scattered waveform only minimally interact. A well-known form is used for the surface scattered component …
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Short pulse generation from semiconductor lasers: characterization, modeling and applications
… been carried out on the generation of optical pulses, with duration of tens of picoseconds, from semiconductor lasers. The work is focused on 1550 nm Vertical Cavity Surface Emitting Lasers (VCSEL), which are promising optical transmitters due to their advantageous characteristics in the …
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Improved temporal coherence and short pulse generation in free electron lasers
… may generate fully transformlimited FEL pulses in the hard X-ray at 0.15 nm. In the second part of the thesis it is shown how the magnetic chicanes may be used to synthesise the effect of an optical cavity with an axial mode structure, and how these axial modes may be phase locked, using …
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Numerical Analysis of Helical and Log-periodic Antennas for Short Pulse Applications
… Radar, satellite communication, GPS, and other short-pulse applications. High far-field gain is essential to many applications, but a tradeoff between gain, and time-domain dispersion exists if the input of the helical antenna is to consist of short-pulses. To quantify the level of dispersion, …
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Asymptotic description of the formation of black holes from short-pulse data
… Einstein vacuum equations from Christodoulou's short-pulse ansatz. We identify natural scaling in a putative solution metric and use the technique of real blowup to propose a desingularized manifold and an associated rescaled tangent bundle (which we call the "short-pulse tangent bundle") on …
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Fast start of oscillations in a short-pulse relativistic magnetron driven by a transparent cathode.
… techniques require high peak power (GW) and short microwave pulses (few ns). To serve as a microwave source for short-pulse applications it is imperative that the magnetron needs to have both fast start and fast rate of build-up of oscillations. Both of these factors are contingent on the …
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Design and Implementation of a Swept Time Delay Short Pulse (SSTDSP) Wireless Channel Sounder for LMDS
… system, called a Sampling Swept Time Delay Short Pulse (SSTDSP) wireless channel sounder, capable of real time in field performance characterization of high speed fixed wireless links. The SSTDSP sounder has been designed to provide vital performance metrics for fixed point high data rate …
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An historical, theoretical and experimental study of the broadband antenna problem with application to short pulse probing radars
… the overall performance is evaluated using both pulse and monocycle waveforms. The results of preliminary tests, involving the location of dielectric interfaces in lossy media, are given and those aspects of the UHF short pulse radar requiring further refinement are indicated.
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Characterization of short-pulse laser-produced fast electrons by 3D hybrid particle-in-cell modeling of angularly resolved bremsstrahlung
The interaction of an intense short-pulse laser with a solid target efficiently generates energetic (fast) electrons above the energy of 1 Mega-electronvolt (MeV). Characterization of such high-energy electrons is critical for numerous applications, such as the generation of secondary particle …
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Increased Proton Energies - Above the ~ 60 MeV Empirical Barrier, from High-Contrast High-Intensity Short-Pulse Laser-Interactions with Micro-Cone Targets
… entering the cone before the main high-intensity pulse, called laser "prepulse". Combining and correlating Cu Ka 2-D imaging with proton acceleration was one of my main goals for this dissertation. At an intrinsic 10^-8 laser contrast, unlike in the 20 J (and ~ 10^19 W/cm^2) case, at 80 J (and ~ …
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Design of bio-inspired texturing treatments, via high power ultra-short pulse lasers, of ferritic stainless steel surfaces that inhibit the formation of bacterial biofouling on tools for hospital use and in the food industry
… of the laser. To generate the LIPSS, the average pulse fluence and the scanning speed were first studied to determine the optimal parameters for creating these nanostructures without damaging the surface (1D analysis). Following this study, in pursuit of generating LIPSS across the entire surface, …
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Pulsed field separation of biomolecules in a nanofluidic filter array
In this work, pulsed electric fields are introduced as a means to enhance separation efficiency of biomolecules in a nanofluidic filter array channel. Separation under pulsed fields was tested using PBR322 DNA, Lambda Hind III DNA, and a sample containing three SDS denatured proteins. Pulsed fields …
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Going Deeper into Laser Damage: Experiments and Methods for Characterizing Materials in High Power Laser Systems
… of high-power laser systems. This is true for short-pulse systems as well as long-pulse and continuous-wave (CW) systems. Unlike short-pulse laser damage, CW laser damage has been much less studied. This work comprises a background of laser damage and laser heating theory, a CW laser damage …
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Feasibility study of micro-laser induced breakdown spectroscopy applied to lead identification in metal alloys and environmental matrices
… of the Microchip Laser, (i.e., high peak power, short pulse width, miniaturization), make it a practical excitation source for chemical analysis. Its high pulse rate yields inherent spectra averaging. It's short pulse width and small focal size leads to a rapidly quenched µLIB plasma, which does …
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Turbulent Methane Oxygen CFD Thermal Effects on Rotating Detonation Engine
… management supporting subsystems under 1 second short pulse runs. Computer fluid dynamic simulations, using methane Lower Heating Value, show the current radially injected mixing design and copper & stainless-steel material choice to provide enough thermal management benefits. The transient and …
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Controlled optical soliton propagation using theoretical tunable dispersion fibers
… control is applied so as to produce Gaussian pulses that overcome current fiber limitations by balancing dispersion and nonlinearity. The pulses will experience no dispersion on average and thus allow ultra-short pulse widths to be propagated. Simulated results suggest that this solution may …
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Ultra-wideband phased array radar for short-range imaging applications
… and simplest-to-generate UWB waveform is the impulse or short pulse. The pulse width of these impulses is usually sub-nanosecond, which enable a range resolution of 15 cm or less, when it is being transmitted in free space.
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Fully Soft-Switching Modulation Methods for SRC-Unfolding Inverter
… pseudo-dc-link inverters are based on pulse-width-modulated converters, which suffer from hard switching, the need for auxiliary components, and/or high current stresses. Meanwhile, the series resonant converter has been prevalent in past decades due to its simplicity and high …
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