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  • 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.
1

Controlling electric fields by graded metamaterials. / 利用梯度超材料控制電場 / Controlling electric fields by graded metamaterials. / Li yong ti du chao cai liao kong zhi dian chang

January 2008 (has links)
Fung, Tai Hang = 利用梯度超材料控制電場 / 馮泰恆. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (p. 56-58). / Abstracts in English and Chinese. / Fung, Tai Hang = Li yong ti du chao cai liao kong zhi dian chang / Feng Taiheng. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What are metamaterials? --- p.1 / Chapter 1.2 --- Negative refraction --- p.1 / Chapter 1.3 --- Transformation media --- p.2 / Chapter 1.4 --- Objectives of the thesis --- p.3 / Chapter 2 --- Mathematical formalism --- p.6 / Chapter 2.1 --- Boundary value problem of anisotropic media in spherical coordinates --- p.6 / Chapter 2.2 --- Boundary value problem of anisotropic media in cylindrical coordinates --- p.9 / Chapter 2.3 --- Anisotropic differential effective multipole moment theory --- p.11 / Chapter 2.4 --- Numerical solution of the radial equation for arbitrary profiles --- p.12 / Chapter 3 --- Perfect cloaking --- p.14 / Chapter 3.1 --- A review on Pendry´ةs cloaking model --- p.14 / Chapter 3.2 --- Perfect spherical cloak --- p.16 / Chapter 3.2.1 --- Perfect spherical cloak in uniform E-field --- p.16 / Chapter 3.2.2 --- Perfect spherical cloak and a point charge --- p.19 / Chapter 3.3 --- Perfect cylindrical cloak --- p.21 / Chapter 3.3.1 --- Perfect cylindrical cloak in uniform E-field --- p.22 / Chapter 3.3.2 --- Perfect cylindrical cloak and an infinite line charge --- p.24 / Chapter 3.4 --- ADEMMT analysis on perfect cloaking model --- p.27 / Chapter 3.4.1 --- Multipole factors of a perfect spherical cloak --- p.27 / Chapter 3.4.2 --- Equivalent dielectric constants of a perfect spherical cloak --- p.28 / Chapter 3.5 --- Remark --- p.29 / Chapter 4 --- Imperfect cloaking --- p.30 / Chapter 4.1 --- Designing cloaking materials via spectral representation theory --- p.31 / Chapter 4.2 --- Electric field distribution of an imperfect cloak --- p.32 / Chapter 4.3 --- ADEMMT analysis on imperfect cloaking model --- p.35 / Chapter 5 --- Confining electric fields spatially by graded metamaterials --- p.37 / Chapter 5.1 --- Graded solid cylinder --- p.38 / Chapter 5.1.1 --- Formalism --- p.38 / Chapter 5.1.2 --- Electric field distribution in graded cylinder --- p.40 / Chapter 5.1.3 --- Discussion --- p.43 / Chapter 5.2 --- Graded cylindrical shell --- p.44 / Chapter 5.3 --- Conclusion --- p.47 / Chapter 6 --- Future problems --- p.48 / Chapter A --- General coordinate transformation --- p.50 / Chapter A.1 --- The invariance of Maxwell´ةs equations --- p.50 / Chapter A.2 --- Scaling of ε and μ --- p.51 / Chapter B --- Designing cloaking model via spectral representation theory --- p.53 / Bibliography --- p.56
2

EFFECTS OF PULSED ELECTRIC FIELDS ON MAMMALIAN CELL MEMBRANES

Smith, Guy K. 01 January 1982 (has links)
The effect of pulsed electric fields on cell membranes were studied to investigate the effects of an electric field, per se, on biological systems, without the densometric and other technical problems associated with other forms of nonionizing radiation. Exposure of mouse splenocytes to a high voltage pulse resulted in an increase in membrane permeability to K+ that was dependent on both the electric field strength and the pulse duration. Exposure to a 2 μsec, 3.0 kV/cm pulse elicited a 50% loss of intracellular K+ indicating that the critical transmembrane potential (Vm) at breakdown was 1.26 volts for the membrane of mouse spleen cells. These results agreed with previous studies on erythrocytes and micro-organisms. Effects of a pulsed electric field on a cell's functional integrity were assessed by measuring 3H-thymidine incorporation by lymphocytes cultured in the presence and absence of various mitogens following exposure to an electrical pulse. No statistically significant effects on the response of mouse spleen lymphocytes to Con-A, PHA, or LPS were observed following exposure to a 2 usec electric pulse. Exposure to 10 μsec pulses ≥ 2.4 kV/cm produced a statistically significant reduction in the response of lymphocytes to LPS stimulation. While not statistically significant, results from both 2 and 10 usec experiments consistently indicated that exposure to pulses at sublethal electric field strengths may have a stimulatory effect on mouse spleen lymphocytes. This result is discussed and an experiment to resolve this issue is presented. Exposure of Ehrlich ascites tumor cells to 2 μsec electrical pulses produced no statistically significant alterations in the tumorigenicity of these cells. K+ release data indicated these cells are unusually resistant to the effects of pulsed electric fields having a high breakdown potential, Vm = 2.37 volts.
3

Analysis of electric fields in power cables /

Cheng, Fai-chut. January 1989 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1990.
4

Breakdown characteristics of nonuniform electric fields in crossflows /

Hanby, David William, January 1993 (has links)
Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 92-94). Also available via the Internet.
5

Actin nanokinematics under the influence of DC electric fields

Chilakamarri, Raghu. January 2005 (has links)
Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains viii, 97 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 87-88).
6

Experimental and analytical study of time varying electrical fields and their effect on convective boiling heat transfer /

North, Travis. January 2004 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-112). Also available on the Internet.
7

Measurement of cathode fields by the Stark effect

Galginaitis, Simeon Vitis, January 1947 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1947. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 27).
8

Experimental and analytical study of time varying electrical fields and their effect on convective boiling heat transfer

North, Travis. January 2004 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 111-112). Also available on the Internet.
9

THE SUBMICROSECOND STRUCTURE OF LIGHTNING RADIATION FIELDS.

WEIDMAN, CHARLES DAVID. January 1982 (has links)
Lightning electric field (E) and electric field derivative (dE/dt) signals have been recorded using sensors with 40 ns and 10 ns response times, respectively. Field propagation between the source and the recording antennas was entirely over salt water, so that distortions due to ground wave propagation were minimal below about 20 MHz. The fast-varying, initial portions of return stroke E fields have 10% to 90% risetimes which average 90 ± 40 ns. Peak dE/dt values range from 7 to 71 V/m/μs, with a mean and standard deviation of 33 ± 14 V/m/μs, when normalized to 100 km using an inverse distance dependence. The shapes of first and subsequent stroke fields are similar, but peak subsequent stroke dE/dts are larger than peak first stroke dE/dts in some flashes. The temporal structure of the fast varying fields produced by leader steps near the ground are very similar to return stroke fields. The mean maximum leader dE/dt, at 100 km, is 27 ± 9 V/m/μs. Large amplitude radiation fields produced by cloud discharge processes tend to be bipolar, with either positive or negative initial polarity and usually have several, fast, unipolar pulses superimposed on the initial half cycle. Cloud discharge fields with positive initial polarity usually precede cloud-to-ground flashes and produce a mean maximum dE/dt of 16 ± 8 V/m/μs. The field derivatives for all processes tend to be large when the amplitude of the associated fast field change is large. Estimates of lightning current derivatives, made using range normalized dE/dt measurements, average 155 ± 70 kA/μs, 135 ± 45 kA/μs, and 80 ± 40 kA/μs, for return strokes, leader steps, and cloud discharges, respectively, and a current wavefront velocity of 1 x 10⁸ m/s. These values are about 10 times larger than the maximum dI/dt recorded in strikes to instrumented towers. Lightning field amplitude spectra have been derived by Fourier analyzing dE/dt waveforms, and the spectral amplitudes decrease as 1/f² or faster with increasing frequency in the interval from about 6 to 20 MHz.
10

Analysis of atomic and molecular negative ions in a constant electric field using a resolvent method

Jung, Jin-Wook, 1973- 09 October 2012 (has links)
We use a resolvent method to study atomic and molecular negative ions in a constant electric field potential which is linear. When a linear potential is applied, it makes the shape of the original potential of the system slanted into one side and thus changes the time evolution of the system. In particular, a bound state can be changed into a state, so called 'quasibound' state, which is not bound anymore and decays into the continuum due to the presence of the linear potential. For an atomic system, we use an attractive delta function fixed at the origin for the interaction potential and solve the single particle Schrodinger equation. For an actual system, we choose the Hydrogen negative ion, and determine the strength of the delta function so that the bound state energy can simulate the electron affinity of the Hydrogen. We find the resolvent of the system and the poles of the resolvent in the analytically continued region. From the patterns of the location of the poles, we can view the one delta function system as a combination of three simple systems. Though they are not exactly the same, this view gives some insight on the system. From the residue at each pole, complex eigenstates are constructed and used for the calculation of the survival probability of an initial state. For the same initial state, we calculate the photodetachment rate when a time-periodic potential is applied. The plot for the photodetachment rate shows peaks at certain incident photon energies. These are compared with an experimental data and give a good agreement although our model is just one dimensional. For a molecular system, two delta function model is suggested by us as an extension of the one delta function model. We find the resolvent of the system and the pole structure from the resolvent. The complex eigenstates are constructed from the residue of the resolvent at each pole. We try to model Oxygen molecular negative ion and determine the strength of the delta function and the distance between the delta functions so that they are consistent with the electron affinity and the internuclear distance of the Oxygen molecule. We also calculate the survival probability and the photodetachment rate of an initial state and find that the plot of the photodetachment rate has similar shape to that of the one delta function model. / text

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