Dissertations / Theses on the topic 'Spacing sizes'

The reserve growth potential of existing conventional oil reservoirs is huge. This research, through numerical simulation, aims to evaluate pattern size reduction as a strategy for improving waterflood recovery in undersaturated oil reservoirs. A plethora of studies have reported improvements in waterflood recovery resulting from pattern size reduction in heterogeneous reservoirs. The dependence of waterflood recovery on pattern size was attributed to factors such as areal reservoir discontinuity, preferential flooding directions, “wedge-edge” oil recovery, irregular pattern geometry, communication with water-bearing zones, vertical reservoir discontinuity, and project economics (Driscoll, 1974). Though many of these publications relied on decline curve analysis in estimating ultimate oil recovery, simulations completed in this thesis support their findings, specifically for compartmentalized reservoirs, fractured reservoirs, and layered reservoirs. Geostatistically-generated permeability fields were employed in the creation of various types of reservoir models. These models were populated with vertical production and injection wells. Sensitivity analysis was then performed on three development scenarios: 160, 40, and 10 acre five-spots. Based on assigned production and injection constraints, the quantity of oil recovered at simulation termination was used to calculate ultimate recovery efficiency. In homogeneous reservoir models, simulation results suggest that waterflood recovery was independent of pattern size. Similar results were also obtained from models with highly-variable non-zero permeabilities. On the other hand, pattern size reduction was found to enhance oil recovery from reservoir models with a high degree of permeability anisotropy. In such reservoirs, recovery was found to be highly dependent on bottom-hole injection pressures. The higher the injection pressure the larger the quantity of oil bypassed by widely spaced patterns. Likewise, high infill potential exists for reservoir models exhibiting areal discontinuity. In these types of models, the improvement in waterflood recovery resulting from pattern size reduction was directly related to the percentage of imbedded zero-permeability grid blocks. Ultimate oil recovery depended on the percolation of permeable grid blocks between production and injection wells. Increasing well density also enhanced waterflood recovery in vertically discontinuous reservoir models. In such layered reservoirs, the amount oil unswept with large patterns was considerably diminished because of the improved injection profiles associated with tighter patterns.<br>text

博士<br>國立交通大學<br>電子物理系所<br>95<br>The asymmetric potentials can provide ways to control the motion of particles in devices. The dc rectification of an ac-driven particle is known as the ratchet effect. For superconductor, we can take advantage of anisotropic pinning in the pinning sites to control the vortex motion. The rectified vortex motion in superconductor is induced by an ac applied force in an asymmetric pinning potential. In this thesis asymmetrically modulated spatial distribution of symmetric pinning sites were studied. The pinning centers are prepared by electron beam lithography with spacing-graded arrays of submicrometer-scaled holes in Nb superconducting thin films. Two different gradient of the hole have been fabricated. The lattice-constant variation results in the change of the pinning site’s density. The gradient structure breaks the symmetry of the vortex pinning potential. For small gradient, at least four matching fields are found in Magnetoresistance (MR) curves. For large gradient, it is found that the commensuration effects were eliminated by introducing graded concentration of hole distributions. MR curves show a kink around the first matching field and no higher-order matching field is observed. The transport properties are carried out using an ac current through the Nb superconducting film along the x-axis with magnetic field perpendicular to the film plane. The dc voltage drop Vdc is recorded along the x-axis by a dc nanovoltmeter. The measurements revealed pronounced rectified voltage which is mainly characterized by vortex-vortex interaction. The asymmetric pinning potentials are crucial to produce the ratchet behavior. Vortex-vortex interaction changes the effective pinning landscape of vortices and asymmetric potential is formed. Vortices depin easily from high concentration to low concentration of pinning sites. For small gradient sample, the rectified voltage is larger at matching fields than that at intermediate fields. Another remarkable situation is that vortices start to repin near the matching fields. Thus the rectified voltage varies periodically with the number of vortex per pinning center. For large gradient sample, the effects of the vortex-vortex interaction are enhanced. The rectified voltage can be found in every selected magnetic fields and the rectified voltage is about 10 times larger than the small gradient sample. In addition, a drastic change of the rectified voltages appear for magnetic field above/below the first matching field. The interstitial vortices are formed in the film above the first matching field. A reversible vortex motion is induced by the interstitial vortices for the field above the first matching field. These results demonstrated that the rectification can be characterized by the spacing-graded of pinning sites.

碩士<br>聖約翰科技大學<br>電子工程系碩士班<br>100<br>This study is mainly to investigate the issues of electromagnetic interference (EMI) and signal integrity (SI) when a signal is in high speed transmission. It considers the implementation of Via in the Guard Traces to improve the current feedback path and consequently to suppress the far-end and near-end crosstalk. In the measurement test it exploits 0.8mm think printed circuit board; the transmission Guard Trace is built from three equal length and equal width 50 Ω transmission lines, it follows the traditional rule of thumb with three times of the line width as the guard separation between the Aggression line and the Victim line. It measures the crosstalk with 1/2λ、1/4λ and 3/8λ as the Via spacing in the Guard Trace. It shows from measurement results that it has 10 dB improvement in the interference suppression than the traditional Guard Trace with 1/4λ and 3/8λ Via spacing. We also perform the measurements with 1/4λand 3/8λ Via spacing in the field wall environment it shows that it does not have any significant interference suppression in the near end crosstalk, however, it does have 3dB improvement in the far end crosstalk suppression and the signal integrity also improves when it passes through the channel.

碩士<br>國立臺灣海洋大學<br>海洋環境資訊學系<br>95<br>The high long-term monthly average of TOMS (Total Ozone Mapping Spectrometer) AI (Aerosol Index) in Northeast Asia in spring is influenced by the dust storm or the biomass burning transported from Southeast. In summer, the high AI value on the ocean is mainly caused by inputs of sea salt on the sea surface or industrial pollution. Angstrom value increases with the size of particle decreasing. This paper used the GACP Angstrom value to observe aerosol size distribution. From the long-term 3oX3o regional monthly mean, the distribution of Angstrom seems to have same temporal and special variation with TOMS AI. For example: Dust storm can raise the finer size dust aerosol particle and transport to far away from the source that cause high Angstrom value appear the southern、southeast and eastern of the high AI value in spring and winter when dust storm mainly happen. The high Angstrom and high AI on sea surface in spring are caused by fine size particle which generated by biomass burning. The monthly mean of Angstrom decrease progressively from the land to the sea during the dust storm season. It is corresponding to the dust storm particle precipitating with dust storm transmitting. Keywords: Aerosol index，TOMS，Angstrom