• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2751
  • 828
  • 337
  • 301
  • 290
  • 166
  • 91
  • 84
  • 64
  • 51
  • 36
  • 33
  • 18
  • 17
  • 16
  • Tagged with
  • 6076
  • 641
  • 594
  • 541
  • 464
  • 429
  • 422
  • 336
  • 290
  • 281
  • 270
  • 264
  • 226
  • 214
  • 214
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Shape from shading with non-parallel light source.

January 1999 (has links)
by Siu-Yuk Yeung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 96-102). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.5 / Chapter 1.1 --- Shape recovery techniques --- p.5 / Chapter 1.2 --- Shape from Shading algorithms --- p.8 / Chapter 1.2.1 --- Some developments on surface reflection --- p.9 / Chapter 1.2.2 --- Some developments on computing methods --- p.11 / Chapter 1.2.3 --- Some developments on light source model --- p.12 / Chapter 1.3 --- Proposed algorithms in this thesis --- p.13 / Chapter 1.4 --- Thesis outline --- p.14 / Chapter 2 --- Camera and surface reflectance models for SFS --- p.15 / Chapter 2.1 --- Camera models for SFS --- p.16 / Chapter 2.1.1 --- Pinhole camera model and perspective projection --- p.17 / Chapter 2.1.2 --- Approximations of perspective projection --- p.20 / Chapter 2.2 --- Surface reflectance models for SFS --- p.22 / Chapter 2.2.1 --- Lambertian surface model --- p.23 / Chapter 2.2.2 --- Bidirectional Reflectance Distribuction Function --- p.23 / Chapter 2.3 --- Summary --- p.25 / Chapter 3 --- Review of some related SFS algorithms --- p.26 / Chapter 3.1 --- The SFS algorithm proposed by Bichsel and Pentland --- p.27 / Chapter 3.1.1 --- Determine surface height with a minimum downhill principle --- p.28 / Chapter 3.1.2 --- Implementation on a discrete grid --- p.30 / Chapter 3.2 --- The SFS algorithm proposed by Kimmel and Bruckstein --- p.31 / Chapter 3.2.1 --- Level set propagation --- p.32 / Chapter 3.2.2 --- Problem formulation --- p.33 / Chapter 3.2.3 --- Equal height contour propagation using level set method --- p.35 / Chapter 3.3 --- Summary --- p.36 / Chapter 4 --- Multiple extended light source models for SFS --- p.38 / Chapter 4.1 --- Three extended light source models for SFS --- p.40 / Chapter 4.1.1 --- Rectangular light source model --- p.40 / Chapter 4.1.2 --- Spherical light source model --- p.43 / Chapter 4.1.3 --- Cylindrical light source model --- p.48 / Chapter 4.2 --- SFS for an extended light source --- p.53 / Chapter 4.3 --- Multiple extended light source model --- p.53 / Chapter 4.4 --- Simulation and experiment result --- p.54 / Chapter 4.5 --- Error Analysis --- p.55 / Chapter 4.5.1 --- Descriptions of the error --- p.55 / Chapter 4.5.2 --- Errors for different light models --- p.55 / Chapter 4.6 --- Summary --- p.57 / Chapter 5 --- Global SFS for an endoscope image --- p.70 / Chapter 5.1 --- Introduction --- p.71 / Chapter 5.2 --- Local SFS algorithm for endoscope image --- p.73 / Chapter 5.2.1 --- Imaging system and brightness formulation --- p.74 / Chapter 5.2.2 --- Equal distance contour propagation and shape reconstruc- tion --- p.75 / Chapter 5.3 --- Global SFS algorithm for endoscope image --- p.76 / Chapter 5.3.1 --- A global shape from shading algorithm for a parallel light --- p.77 / Chapter 5.3.2 --- The relationship between depth map and distance map --- p.78 / Chapter 5.3.3 --- A global shape from shading algorithm for endoscope image --- p.78 / Chapter 5.4 --- Simulations and experiments results --- p.83 / Chapter 5.5 --- Summary --- p.86 / Chapter 6 --- Summary and conclusion --- p.87 / Chapter 6.1 --- Problems tackled in this thesis --- p.87 / Chapter 6.2 --- Discussion on future developments --- p.88
92

Development and Application of an Area Recorded Generalized Optical Scattering Technique

Algarni, Saad A 18 December 2014 (has links)
"A novel approach to a light scattering experiment that employs a lounge image capture assay has been developed for both static and dynamic measurement on a wide variety of samples. In this work, the 'Development and Application of an Area Recorded Generalized Optical Scattering Technique', abbreviate as ARGOS, an approach is based on the placement of a translucent screen where the scattered light, now converted to a diffuse light, is imaged as a function of time. The placement and size of the screen determines the range of scattering wave-vectors, while the time between images determines the fastest dynamic resolvable . The overall experimental stability determines the slowest dynamic resolvable and so can be made arbitrarily long. The scattering intensity is measured by a camera whose dynamic range (number of bits per pixel), resolution, and speed determines the sensitivity and accuracy of intensity of the scattered light. The system allows for an extremely well-defined scattering experiment geometry, where images may be manipulated to extract structure (i.e. average I(q)over t) and dynamics (average I(q,t) over q) for a wide range of samples(liquids and solids). A number of innovation were developed. Instead of a beam stop to block the high intensity thru-beam, a thru-beam attenuator was developed such that the exact center of the scattering geometry is determined for each image acquired. A variety of image processing algorithms were also developed to correct for dead pixels, camera response, and intensity normalization. Of particular use was the development of the root-mean-square difference(RSD) image to probe dynamic. Here, the first image is taken as the time-zero reference image and subtracted from all succeeding images where averaged over a speci ed q and plotted as a function of time revealing the build up image changes due to dynamics. The technique was validated for both static and dynamic measurements with a set ofdilute suspended latex spheres in water (sizes ranging from 0.01 to 2micro m). The static light scattering result in terms of particle radius and dimension closely matched the expected values. The dynamic light scattering results could only several the end of the dynamics of these suspended latex spheres due to Brownian motion because of the speed limitation of the camera. However, sedimentation dynamics that are much slower, were early observed. The ARGOS technique was then applied to two biological systems, the evolution of a dilute suspension of E. Coli bacteria through the life-cycle and the evolution of the same suspended bacteria but infected with the MS2 bacteria-phage virus. High temporal resolution data were obtained of the bacteria life-cycle which werecorrelated with size, structure, and dynamics that revealed potentially new insights on behavior not well understood in the literature . The MS2 infected bacteria revealed the effect of the bacteria-phage on every character of the E. Coli life-cycle. The successful development and implementation of ARGOS here has also revealed avenues to greatly improve the performance."
93

Effects of early light environment on the photic response of the circadian system

Hurley, Elisabeth January 2012 (has links)
Early light environment has been shown to alter locomotor activity behaviour in adult rats and mice when exposed to constant light (LL), constant darkness (DD) or 12:12 hour light-dark cycles (LD). In particular, exposure to LL during lactation results in an increased ability to cope with exposure to LL as adults, implying that the ability to interpret light information is altered depending on early light environment. Therefore, the aim of this project was to explore how early light environment affects the photic response of the circadian system. The retina forms the first component of the photic response of the circadian system. We wanted to know whether being raised in DD, LD or LL would alter retinal function or structure in adult CD1 (albino) and C57BL/6J (pigmented) mice. We found that in CD1 mice, being raised in LL caused significant retinal damage and a significant reduction in retinal function. In C57BL/6J mice, we saw no such changes, implying that any changes that we see in behaviour would be due to alterations further downstream, such as the suprachiasmatic nucleus (SCN), site of the master circadian clock in the mammalian brain. We next exposed C57BL/6J mice to LL and found that mice raised in DD had significantly longer taus than mice raised in LL, implying that mice raised in DD are more sensitive to light than mice raised in LL.Previous work has shown that early light environment alters neuropeptide and astrocyte expression in the SCN of C57BL/6J mice. Furthermore, early light environment produces opposite behavioural responses in CD1 and C57BL/6J mice when exposed to LD as adults. We therefore examined how neuropeptide and astrocyte expression would be affected by early light environment in CD1 mice and whether this would reflect the differential behavioural response. We found that neuropeptide and astrocyte expression in the SCN seemed to be affected by the level of retinal damage and/or the type and intensity of the light source used. This sensitivity to lighting environment makes CD1 mice unsuitable for further studies on the photic response of the circadian system. Pigmented mice were used for the remainder of this project. The photic response of the circadian system can be quantified using a phase response curve (PRC) which measures behavioural responses to light pulses administered at different times of day. We measured the effect of a light pulse on the delay and advance portion of the PRC and found no differences due to early light environment, implying that the phasic effect of light is not altered by early light environment. Light pulses administered during the subjective night result in the upregulation of SCN intracellular photic signalling pathways. After a light pulse given during the early subjective night, we found no differences in the upregulation of different components of the photic signalling pathway due to early light environment indicating early light environment does not seem to affect the initial photic signalling pathway in the SCN.Finally, recent advances in molecular biology allow for real-time monitoring of clock gene expression in vitro. Using mPer2::luc mice, we monitored in vitro PER2::LUC expression to determine the effects of early light environment on clock gene expression. In the SCN, we found that the amplitude of PER2::LUC expression was significantly reduced in mice raised in DD compared to mice raised in LD and LL. These results suggest that early light environment affects the coupling strength between SCN neurons and this may be the mechanism mediating the changes in behaviour we have measured. In peripheral tissue, we found altered PER2::LUC expression due to early light environment in the heart, lung and spleen, implying that early light environment not only alters behaviour but may also affect heart and lung function and the immune system.
94

A fibre-based single-photon source

Riley-Watson, Andrew G. January 2013 (has links)
The controlled emission and absorption of single photons is an important enabling technology in the fields of quantum communication, cryptography and computing. We have realised a novel single photon source, based on a miniature ‘endcap' ion trap with integrated optical fibres. To minimise distortion of the trapping field the fibres are tightly integrated and recessed within the two hollow cylindrical rf electrodes of the trap. This allows us to bring the fibres to within approximately 300 μm of the trapped ion. With the fibres in place we are able to collect the ion's fluorescence using no further optics. In this thesis the ion trap is fully characterised, and the quantum nature of the light demonstrated in the results of a variant on the Hanbury Brown-Twiss photon-correlation experiment. The scheme will ultimately be extended to implement a coherent ion-photon interface through strong coupling cavity-QED. Towards this end, an ultra-high-finesse cavity has been designed and fabricated by laser-machining and coating surfaces with a range of radii of curvature on the end facets of the fibres. To improve the stability and precision manipulation of the cavity in-vacuum, an entirely new trap has been designed and built. Finally, the current status of the fibre cavity and the outlook for the experiment are presented.
95

On the interpretation of the extinction paradox in light scattering. / 光學中消光截面佯謬之解釋 / On the interpretation of the extinction paradox in light scattering. / Guang xue zhong xiao guang jie mian yang miu zhi jie shi

January 2003 (has links)
Wong Wan Yan = 光學中消光截面佯謬之解釋 / 黃蘊殷. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 58-60). / Text in English; abstracts in English and Chinese. / Wong Wan Yan = Guang xue zhong xiao guang jie mian yang miu zhi jie shi / Huang Yunyin. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Scattering of a Plane Wave by an Infinitely Long Cylinder --- p.4 / Chapter 2.1 --- Dielectric cylinder (with no absorption) --- p.8 / Chapter 2.2 --- Perfectly conducting cylinder --- p.10 / Chapter 3 --- Scattering of a Gaussian Beam by a Dielectric Cylinder (Non- Resonance) --- p.13 / Chapter 3.1 --- Configuration and equations used --- p.13 / Chapter 3.2 --- Numerical result and discussion --- p.17 / Chapter 3.2.1 --- a <w --- p.19 / Chapter 3.2.2 --- a>w --- p.21 / Chapter 4 --- Scattering of a Gaussian Beam by a Dielectric Cylinder (Res- onance) --- p.24 / Chapter 4.1 --- Algorithm --- p.26 / Chapter 4.2 --- Numerical result and discussion --- p.28 / Chapter 5 --- Scattering of a Plane Wave by a Conducting Strip --- p.33 / Chapter 5.1 --- Configaration and equations used --- p.34 / Chapter 5.2 --- Numerical calculation --- p.39 / Chapter 5.3 --- Numerical results and discussion --- p.42 / Chapter 6 --- Actual Scattering Cross Section --- p.49 / Chapter 6.1 --- Configaration and Equations used --- p.49 / Chapter 6.2 --- Numerical result and disscusions --- p.51 / Chapter 7 --- Conclusions --- p.56 / Bibliography --- p.58 / Chapter A --- Bessel functions --- p.61 / Chapter B --- A plane wave incident on a single-layered medium --- p.63
96

Iridium-based organometallic electrophosphors for organic light-emitting devices

Lam, Ching Shan 01 January 2009 (has links)
No description available.
97

Slowing light in plasmonic chains. / 在等離子體鏈中使光變慢 / Slowing light in plasmonic chains. / Zai deng li zi ti lian zhong shi guang bian man

January 2010 (has links)
Ling, Chi Wai = 在等離子體鏈中使光變慢 / 凌志偉. / "September 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (p. 73-76). / Abstracts in English and Chinese. / Ling, Chi Wai = Zai deng li zi ti lian zhong shi guang bian man / Ling Zhiwei. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Slowing down of light --- p.1 / Chapter 1.2 --- Objectives of the thesis --- p.4 / Chapter 2 --- Review on Bergman-Milton Theory of Green Function --- p.5 / Chapter 2.1 --- Green function for Laplace operator --- p.5 / Chapter 2.2 --- Integral equation for two-component systems --- p.6 / Chapter 2.3 --- Symbolic solution for two-component systems --- p.10 / Chapter 2.4 --- An isolated dielectric sphere --- p.11 / Chapter 2.5 --- Extension to a collection of multi-interacting spheres --- p.13 / Chapter 3 --- Slowing Light by Multipolar Effect in Metal Nanoparticle Chains --- p.16 / Chapter 3.1 --- Evaluating the dispersion relations --- p.17 / Chapter 3.2 --- Results and discussions on multipolar effects --- p.20 / Chapter 4 --- Level Repulsion Phenomenon --- p.23 / Chapter 4.1 --- Two coupled oscillators --- p.24 / Chapter 4.1.1 --- Normal mode method --- p.24 / Chapter 4.1.2 --- Forccd oscillator method --- p.25 / Chapter 4.2 --- Metallic nanoshells --- p.25 / Chapter 4.3 --- Two coupled metal nanoparticles --- p.27 / Chapter 4.4 --- Diatomic spring-mass chain --- p.28 / Chapter 4.4.1 --- Dispersion relation --- p.29 / Chapter 4.4.2 --- Forced oscillator method --- p.30 / Chapter 5 --- Slowing Light by Hybridization of Bands in Plasmonic Chains --- p.34 / Chapter 5.1 --- Coupled dipole equation of plasmonic Chains --- p.34 / Chapter 5.2 --- Monatomic metal nanoparticle chains --- p.36 / Chapter 5.3 --- Diatomic chains formed by unshcllcd metal nanoparticles and shelled metal nanoparticles --- p.39 / Chapter 5.3.1 --- Formalism for evaluating dispersion relation --- p.39 / Chapter 5.3.2 --- Hybridization of bands --- p.42 / Chapter 5.3.3 --- Stopping light using photon-phonon assisted proccss --- p.45 / Chapter 5.3.4 --- Discussions --- p.47 / Chapter 5.4 --- Monatomic chains formed by nanoshells --- p.49 / Chapter 5.4.1 --- Formalism --- p.50 / Chapter 5.4.2 --- Numerical results and discussions --- p.54 / Chapter 5.4.3 --- Conclusions --- p.57 / Chapter 5.5 --- Diatomic chains formed by two types of dielectric shelled nano- particles --- p.60 / Chapter 5.5.1 --- Formalism for evaluating dispersion relation --- p.60 / Chapter 5.5.2 --- Results and discussions --- p.63 / Chapter 5.6 --- Yin-yang plasmonic chain --- p.68 / Chapter 6 --- Summary --- p.71 / Bibliography --- p.73 / Chapter A --- Properties of operator Γ --- p.77 / Chapter A.1 --- Hermitian Property of operator Γ --- p.77 / Chapter A.2 --- Eigenfunctions and eigenvalues of operator Γ for isolated spheres --- p.78 / Chapter B --- Drude Model and Polarizabilities of Spheres --- p.82 / Chapter B.1 --- Drude Model --- p.82 / Chapter B.2 --- Polarizabilities of spheres --- p.83 / Chapter C --- Dyadic Green's Function --- p.85
98

Numerical and experimental studies on elastic light scattering from spherical droplets, including high-order rainbows, glare points, and morphology dependent resonances. / 球狀液滴的彈性光散射,包括高階彩虹、炫光點及形態相關共振的數值計算與實驗研究 / Numerical and experimental studies on elastic light scattering from spherical droplets, including high-order rainbows, glare points, and morphology dependent resonances. / Qiu zhuang ye di de tan xing guang san she, bao kuo gao jie cai hong, xuan guang dian ji xing tai xiang guan gong zhen de shu zhi ji suan yu shi yan yan jiu

January 2008 (has links)
Ng, Kin Sang = 球狀液滴的彈性光散射,包括高階彩虹、炫光點及形態相關共振的數值計算與實驗研究 / 吳健生. / Thesis submitted in: October 2007. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 101-104). / Text in English; abstracts in English and Chinese. / Ng, Kin Sang = Qiu zhuang ye di de tan xing guang san she, bao kuo gao jie cai hong, xuan guang dian ji xing tai xiang guan gong zhen de shu zhi ji suan yu shi yan yan jiu / Wu Jiansheng. / Acknowledgements --- p.i / Abstract --- p.ii / Table of Contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Brief history --- p.1 / Chapter 1.2 --- The theory of rainbow --- p.4 / Chapter 1.2.1 --- Rainbow position --- p.4 / Chapter 1.2.2 --- Airy theory --- p.6 / Chapter 1.3 --- Glare points --- p.9 / Chapter 1.4 --- Mie scattering theory and Debye series --- p.11 / Chapter Chapter 2 --- Interference of the nth- and higher-order rainbows --- p.16 / Chapter 2.1 --- Introduction --- p.16 / Chapter 2.2 --- Interference of overlapping rainbows --- p.18 / Chapter 2.3 --- Results and discussion --- p.20 / Chapter 2.3.1 --- Glare point intensity of group G(ll) --- p.20 / Chapter 2.3.2 --- "Glare point intensities of groups G(8), G(9), and G(10)" --- p.24 / Chapter 2.3.3 --- Effects of varying acceptance angle --- p.27 / Chapter 2.3.4 --- Comparison with results of Lock and Woodruff --- p.29 / Chapter Chapter 3 --- Glare points of high-order rainbows --- p.30 / Chapter 3.1 --- Introduction --- p.30 / Chapter 3.2 --- Results and discussion --- p.32 / Chapter 3.2.1 --- Glare points formed by rainbows of a particular order --- p.32 / Chapter 3.2.2 --- Glare points obtained by plane wave calculation --- p.42 / Chapter Chapter 4 --- Elastic light scattering from droplets embedded in gelatin --- p.45 / Chapter 4.1 --- Introduction --- p.45 / Chapter 4.2 --- Motivation --- p.48 / Chapter 4.3 --- Experimental Preparations --- p.51 / Chapter 4.3.1 --- Sample preparation --- p.51 / Chapter 4.3.2 --- Measurement of refractive index of gelatin --- p.53 / Chapter 4.4 --- Observation of morphology-dependent resonances by varying wavelength of incident laser light --- p.56 / Chapter 4.4.1 --- Experimental setup --- p.56 / Chapter 4.4.2 --- Results and discussion --- p.58 / Chapter 4.5 --- Observation of morphology-dependent resonances by varying temperature of droplet --- p.70 / Chapter 4.5.1 --- Experiment --- p.70 / Chapter 4.5.2 --- Results and discussion --- p.73 / Chapter 4.6 --- Scattered light intensity as a function of scattering angle --- p.77 / Chapter 4.6.1 --- Experiment --- p.77 / Chapter 4.6.2 --- Results and discussion --- p.79 / Chapter Chapter 5 --- Conclusion and future outlook --- p.89 / Appendix Program dave.for Listing --- p.92 / References --- p.101
99

Light as surface and intensity

Edmonds, Anne, University of Western Sydney, College of Arts, Education and Social Sciences, School of Contemporary Arts January 2003 (has links)
Light Intensity and Surface is the title of this PhD art exhibition where I explore through paintings, the world of my own encounter with the radiant light of the Linear Accelerator used in treatment of women with breast cancer. This engagement with the world of light technology encompasses oncologists, physicists and women who extended their personal experience to inform my artwork and contribute to the theoretical connections made in this thesis. The contribution of this thesis lies in how the lecture The Origin of the Work of Art by philosopher Martin Heidegger can be applied to a reading of great artworks that are separated in time, space and culture but connected in their subject: Light. It was his philosophy that helped shape the connections between where art originates and what springs from the artwork itself. The concept of light in the title of this thesis refers to Heidegger’s notion of the clearing seins Lichtung-the lighting centre- the medium that holds one being to another from where the idea for an artwork springs in the artist. Surface relates to the attunement of artists throughout history to the new particularly in the science of controlling light which influences the way artists achieve the material appearance of their artwork. Intensity refers to the level of openness to the mystery of light in both physicists and artists to create and control some thing that stabilises a community and remains a source of wonder. This thesis demonstrated how artists have responded to the new light technology with a way of seeing that created a depth dimension that bridges cultural worlds to unearth the breath of something often most effectively communicated by being silent / Doctor of Philosophy(PhD)
100

Designing a very light jet

Nyblom, Per January 2009 (has links)
<p>Introduction</p><p><p>Very light jet is a hot subject growing stronger and stronger. The new type of air craft is an air plane that weighs less than 10000 pounds and uses a jet engine.</p><p>Problem</p><p>The student was proposed to designing a conceptual very light jet that could be used for inspiration and accepted the challenge.</p><p>Method</p><p>In this thesis the reader can follow the project progress in detail, the proposed methods and the results. The student divided the project into four activities analysis, creation, development and documentation.</p><p>Result</p><p>The project ended with a concept very light jet with simple specifications. Illustrations for inspirational usage and a simulation testing for verification of the proposed concept specifications.</p></p>

Page generated in 0.0375 seconds