1,904 research outputs found
Filtration properties of water based drilling fluids
This thesis reports an experimental and theoretical study on filtration properties of
water based drilling fluids under dynamic and static conditions. The tested muds cover
Freshwater/Gypsum/Lignosulphonate mud and SeawaterlKCLlPolymer mud, bariteweighted
and unweighted. The effects of the solid concentration, pressure and shear rate
on the filter cake characteristics and the erodability were investigated. For static filtration
experiments, all tests were conducted for two hours and the spurt loss, the filter cake
thickness, the ratio of wet to dry cake mass and the cumulative filtrate volume against
time were measured. For dynamic filtration experiments, however, only the spurt loss
and the cumulative filtrate volume against time were measured and all tests were
conducted for at least 8 hours. A general filtration equation was developed based on the
cake filtration theory prevailing in the chemical engineering industry and it was utilised to
obtain the modified classic static filtration equation and the dynamic filtration equation.
The modified classic static filtration equation was then employed to fit the static filtration
experimental data and the average specific static cake resistance and the effective filter
medium resistance were calculated. The dynamic filtration equation showed a substantial
agreement with the dynamic filtration experimental data. Using the static filter cake
properties such as the ratio of wet to dry cake mass (m), the average specific dynamic
cake resistance, the effective filter medium resistance and the dynamic filter cake
erodability were calculated. In the study of the relationship between the static filtration
data and the dynamic filtration data, an attempt of predicting the dynamic filtration data
from the static filtration experimental data was conducted. Also, an attempt was carried
out to predict the static filtration data and the dynamic filtration data in a sequential
process. The experimental data suggests that a substantial difference exists between the specific resistances of static and dynamic filter cakes. No apparent distinction was found, however, between spurt loss and effective filter medium resistance. The reodability of dynamically deposited mud cake for Seawater/KCL/Polymer mud was found to be three fold for Freshwater/Gypsum/Lignosulphonate
A Research on the Influential Factors of Listing Sales Based on Online Information in Short Rental Markets
Recent years,sharing economy as a new business model has developed very well in the whole world and the online marketplace for peer-to-peer accommodation rental services such as XiaoZhu change people’s life a lot.With the development of social media and information technology,consumers can not only pubulish text comments but also can share the photos taken by them on the paltform as a supplement.In order to study the impact of online information on the sales volume of houses under the background of sharing-economy, we collect data from XiaoZhu and use the correlation analysis and regression analysis. This research provides a new perspective for the sharing research and foucuses on China’s online short-term rental market. The result shows that the total number of online reviews, the number of picture comments and the price have significant effects on home sales
Pre-merger electromagnetic counterparts of binary compact stars
We investigate emission signatures of binary compact star gravitational wave
sources consisting of strongly magnetized neutron stars (NSs) and/or white
dwarfs (WDs) in their late-time inspiral phase. Because of electromagnetic
interactions between the magnetospheres of the two compact stars, a substantial
amount of energy will be extracted, and the resultant power is expected to be
erg/s in the last few seconds before the two stars
merge, when the binary system contains a NS with a surface magnetic field
G. The induced electric field in the process can accelerate charged
particles up to the EeV energy range. Synchrotron radiation is emitted from
energetic electrons, with radiative energies reaching the GeV energy for binary
NSs and the MeV energy for NS - WD or double WD binaries. In addition, a
blackbody component is also presented and it peaks at several to hundreds keV
for binary NSs and at several keV for NS - WD or double WD binaries. The strong
angular dependence of the synchrotron radiation and the isotropic nature of the
blackbody radiation lead to distinguishable modulation patterns between the two
emission components. If coherent curvature radiation is presented, fast radio
bursts could be produced. These components provide unique simultaneous
electromagnetic signatures as precursors of gravitational wave events
associated with magnetized compact star mergers and short gamma ray bursts
(e.g., GRB 100717).Comment: 16 pages, 8 figures, 1 table. Minor corrections to match the version
on Ap
Extremal Kerr black hole/CFT correspondence in the five-dimensional Gödel universe
AbstractWe extend the method of Kerr/CFT correspondence recently proposed in arXiv:0809.4266 [hep-th] to the extremal (charged) Kerr black hole embedded in the five-dimensional Gödel universe. With the aid of the central charges in the Virasoro algebra and the Frolov–Thorne temperatures, together with the use of the Cardy formula, we have obtained the microscopic entropies that precisely agree with the ones macroscopically calculated by Bekenstein–Hawking area law
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