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1.
Wai Kuan Foong Angus R. Simpson Holger R. Maier Stephen Stolp 《Annals of Operations Research》2008,159(1):433-450
A number of algorithms have been developed for the optimization of power plant maintenance schedules. However, the true test
of such algorithms occurs when they are applied to real systems. In this paper, the application of an Ant Colony Optimization
formulation to a hydropower system is presented. The formulation is found to be effective in handling various constraints
commonly encountered in practice. Overall, the results obtained using the ACO formulation are better than those given by traditional
methods using engineering judgment, which indicates the potential of ACO in solving realistic power plant maintenance scheduling
problems. 相似文献
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Laboratory Investigation of LNAPL Migration in Double-Porosity Soil Under Fractured Condition Using Digital Image Analysis 总被引:1,自引:0,他引:1
Norhan Abd. Rahman Loke Kok Foong Roland W. Lewis Ramli Nazir 《Transport in Porous Media》2018,122(3):521-526
Gas production from shale gas reservoirs plays a significant role in satisfying increasing energy demands. Compared with conventional sandstone and carbonate reservoirs, shale gas reservoirs are characterized by extremely low porosity, ultra-low permeability and high clay content. Slip flow, diffusion, adsorption and desorption are the primary gas transport processes in shale matrix, while Darcy flow is restricted to fractures. Understanding methane diffusion and adsorption, and gas flow and equilibrium in the low-permeability matrix of shale is crucial for shale formation evaluation and for predicting gas production. Modeling of diffusion in low-permeability shale rocks requires use of the Dusty gas model (DGM) rather than Fick’s law. The DGM is incorporated in the TOUGH2 module EOS7C-ECBM, a modified version of EOS7C that simulates multicomponent gas mixture transport in porous media. Also included in EOS7C-ECBM is the extended Langmuir model for adsorption and desorption of gases. In this study, a column shale model was constructed to simulate methane diffusion and adsorption through shale rocks. The process of binary \(\hbox {CH}_{4}{-}\hbox {N}_{2}\) diffusion and adsorption was analyzed. A sensitivity study was performed to investigate the effects of pressure, temperature and permeability on diffusion and adsorption in shale rocks. The results show that methane gas diffusion and adsorption in shale is a slow process of dynamic equilibrium, which can be illustrated by the slope of a curve in \(\hbox {CH}_{4}\) mass variation. The amount of adsorption increases with the pressure increase at the low pressure, and the mass change by gas diffusion will decrease due to the decrease in the compressibility factor of the gas. With the elevated temperature, the gas molecules move faster and then the greater gas diffusion rates make the process duration shorter. The gas diffusion rate decreases with the permeability decrease, and there is a limit of gas diffusion if the permeability is less than \(1.0\,\times \,10^{-15}\, \hbox { m}^{2}\). The results can provide insights for a better understanding of methane diffusion and adsorption in the shale rocks so as to optimize gas production performance of shale gas reservoirs. 相似文献
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Moy FM 《Journal of photochemistry and photobiology. B, Biology》2011,104(3):444-448
Vitamin D status is influenced by sun exposure, geographic latitude, daily outdoor activities, body surface exposed to sunlight and dietary intakes. Malaysia, is sunny all year round. However, the vitamin D status of this population especially among the healthy and free living adults is not known. Therefore a study of vitamin D status and associated factors was initiated among an existing Malay cohort in Kuala Lumpur. A total of 380 subjects were sampled to have their vitamin D status assessed using 25-hydroxyvitamin D (25(OH)D). A short questionnaire enquiring socio-demographic characteristics, exposure to sunlight and clothing style was administered. Their mean age was 48.5±5.2years and the mean 25(OH)D for males and females were 56.2±18.9nmol/L and 36.2±13.4nmol/L respectively. There were significant positive correlation for sun exposure score (r=0.27, p<0.001) and negative correlation for sun protection score (r=-0.41, p<0.001) with 25(OH)D levels. In the logistic regression model, females (OR=2.93; 95% CI: 1.17, 7.31), BMI (1.1; 1.03, 1.20) and sun exposure score (0.998; 0.996, 0.999) were significantly associated with vitamin D status as represented by 25(OH)D levels. Our findings show that obesity, lifestyle behaviours and clothing style are directly associated with our participants especially females' low vitamin D status. 相似文献
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P. Dai Jiandi Zhang H.A. Mook F. Foong S.-H. Liou P.A. Dowben E.W. Plummer 《Solid State Communications》1996,100(12):865-869
The structural and magnetic behavior of the perovskite insulator La0.9Ca0.1MnO3 were studied as a function of temperature from 15 to 300 K by neutron powder diffraction. Although this compound shows an anomalous response of the lattice parameters around Tc (150 K), the behavior of the oxygen/manganese Debye-Waller factors is in clear contrast to its “colossal magnetoresistance” (CMR) counterpart La0.65Ca0.35MnO3. We speculate that the difference is intimately associated with the metal-insulator transition in the latter compound. 相似文献
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Way Foong Lim Zainovia Lockman Kuan Yew Cheong 《Applied Physics A: Materials Science & Processing》2012,107(2):459-467
Metal-organic decomposed lanthanum cerium oxide (La
x
Ce
y
O
z
) film had been spin-coated on n-type Si substrate. Effects of post-deposition annealing temperature and time on the metal-oxide-semiconductor
(MOS) properties of the film were studied. As temperature increased from 400 to 1000°C for 15 minutes dwell time, La
x
Ce
y
O
z
demonstrated a decrease in interface trap density (D
it) and total interface trap density (D
total), which were related to the formation of SiO
x
/silicates interfacial layer (IL). The lowest leakage current density and highest dielectric breakdown voltage (V
B) was obtained in 1000°C-annealed sample. When longer annealing times (30–120 minutes) were studied on the 1000°C-annealed
sample, the sample annealed at 1000°C for 120 min showed the best MOS characteristics with V
B of 30 V. Reasons contributing to such observation were discussed. 相似文献
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A novel experimental rig capable of generating a versatile dynamic loading has been designed and tested to overcome the shortcomings of conventional fatigue testing machines such as the difficulty in providing zero crossing aperiodic loading. The main principle of this new design is based on two, single degree of freedom based excited oscillators, where inertial forces act on a specially designed specimen. By changing the natural frequency of the oscillator, the extent of the preloads and pattern of the excitation signal on the shaker, the rig provides a new and robust means of fatigue testing, particularly for aperiodic loading. 相似文献