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 78 for “"group velocity"”.
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Group Velocity Of Acoustic Waves In Plates Of Electronic Materials
… waves through the plates is measured and the group velocities of the so and a o modes are then computed and plotted against the frequency and the thickness of the plate. These results compare well with the theoretical results obtained from published work. Group velocities of PAW in all of them …
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Study on dynamic behavior of ring-cavity quantum-cascade lasers with group velocity dispersion
… nonlinearities, unique gain and dispersions. Group velocity dispersion (GVD) plays an important role in the study of QCLs because of its effects on pulse spectrum in both unsaturation and saturation regime. To investigate the effect of group velocity dispersion in QCLs, both instability …
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A global study on phase velocity, group velocity and attenuation of Rayleigh waves in the period range 20 to 100 seconds
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1987.
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Three dimensional (3D) optical information processing
… proposed waveguide structures suffer from large group velocity dispersion (GVD) and exhibit relatively small guiding bandwidth because of the distributed Bragg reflection (DBR) along the guiding direction. As optical communications and optical computing progress, more challenging demands have …
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Dispersion, controlled dispersion, and three applications
… gain. However, over the past 15 years several groups have demonstrated that it is possible to have media that are both strongly dispersive and roughly transparent for some finite bandwidth. In these media, group and phase velocities may differ from each other by many orders of magnitude and …
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A boundary element method with surface conductive absorbers for 3-D analysis of nanophotonics
… waveguide system is excited with a large group-velocity mode may fail when excited with a smaller group-velocity mode, and give an asymptotic relation between the surface absorber length, transition reflections and group velocity. Numerical results are given to validate the asymptotic …
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Investigation of High-Nonlinearity Glass Fibers for Potential Applications in Ultrafast Nonlinear Fiber Devices
… have high nonlinearities, they also have high group-velocity dispersion and high losses deteriorating the performance of nonlinear fiber devices seriously. The aim of this work is to investigate how these high-nonlinearity glasses affect the performance of nonlinear fiber devices, taking into …
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Modeling of sequences of Silicon micro-Resonators for On-Chip Optical Routing and Switching
… multiple cascading and/or multiple coupling (low group velocity) periodicity effects. We will describe some technical aspects necessary for the design and fabrication of some passive circuitry, and usually neglected in purely theoretical approaches, including optical routers based on racetrack …
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Anomalous phenomena and spectral tailoring in photonic crystals
… the photonic states that exist around a zero-group velocity point. Motivated by negative refraction, a measure of the effective wavevector is constructed that distinguishes various types of zerogroup velocity modes. Around one type of zero-group velocity mode, an anomalous region of backward …
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Intensyvių femtosekundinių šviesos bangų paketų sklidimo Kero terpėse laikinis ir erdvinis charakterizavimas /
… it was shown that in the medium with normal group velocity dispersion the far-field angular spectrum of the wave packet takes a characteristic X shape, whereas in anomalous group velocity dispersion regime – a characteristic O shape. In both cases the localization of the wave packet is …
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Low Frequency Edge Waves and Their Role In Coastal Dynamics
… dispersion characteristics revealed that the group velocity of the HKEW can be very low or even zero over a wide, gently sloping continental shelf. Numerical modeling experiments indicate that when the semidiurnal HKEW traveling over a narrowing shelf encounters such a shelf width that causes …
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Description and Dynamics of 50-Day Oscillations in the Western Tropical Region of the CME Model
… oscillations seen in the meridional component of velocity between 35° and 55°W and between 5° and 11°N. Validation studies showed that the model reproduced the surface circulation in this area with a reasonable degree of accuracy, in particular, the characteristic seasonal variability. From June …
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Emission of whistler waves from an ionospheric tether
… different wave propagation ways by analyzing the group velocity and k surface of the wave. There are intense radiation directions. We discuss the nature of these intense radiation directions and compare the characteristics with the past works. There are spatial oscillations of wave fields and wave …
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A few-cycle Cr⁴⁺:YAG laser and optical studies of photonic crystals
… nm with a bandwidth of 190 nm FWHM. Intracavity group velocity dispersion was compensated with double-chirped mirrors. Pulse spectrum was observable from 1140 to >1700 nm. Broadband saturable Bragg reflectors were designed and used to ensure self-starting of 35 fs pulses in the ultrafast Cr4+:YAG …
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The anelastic structure and deep geology of the Derbyshire Dome from high frequency Rayleigh waves.
… of which are marked by sudden changes in group velocity and co-incide with geological surface features. Similar provinces are not found in the adjacent Millstone Grit district. Approximate estimates of group velocity are higher over the limestone than over the Millstone Grit district. …
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The Effectiveness of a Physical Therapy Intervention for Children with Hypotonia and Flatfeet
… in this study. <strong>Methods:</strong> Three groups (control, orthotic, and orthotic-exercise) were studied. The orthotic- exercise group practiced bilateral heel lifts besides wearing the orthoses. An arch index was used to assess the width of the medial longitudinal arch (MLA) pre/post …
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A circuit model BOSS simulation of nonlinear effects in long distance fiber optic systems
The combined effect of group velocity dispersion (GVD) and nonlinearity limits the transmission distance of fiber optic communication systems. By designing a circuit that can model this effect and simulating it using the Block Oriented Systems Simulator (BOSS), we can study the pulse distortion and …
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Interference and Transmission of locally forced internal waves in non-uniform stratifications
… indication of this physical effect. Based on the group velocity and angle of propagation of the internal waves, a practical criteria that assesses when the transmission peaks or troughs are evident, is obtained. It is found that there is a significant difference in the predicted energy transfer …
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The charge migration in biomolecules
… 10 to the -15 sec for most cases. And the r.m.s. velocity of spreading is approximately equal to the group velocity in the band conduction, it is estimated that vrms = 10 to the 6th ~10 to the 7th cm/sec. The probability of finding the access charge at n unit cells away from the initial place is …
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Slow and Fast Light Using Quantum-Dot and Quantum-Well Semiconductor Optical Amplifiers
Controlling the group velocity of light has great potential applications in future optical communication, photonic computing, and microwave signal processing. These applications have recently triggered immense experimental and theoretical interest in the research community. Numerous studies report …
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