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排序方式: 共有368条查询结果,搜索用时 15 毫秒
31.
Alaa El-Din Abdin Mostafa A. M. Abdeen 《Journal of Mechanical Science and Technology》2005,19(8):1582-1596
Groundwater flow and behavior have to be investigated based on heterogeneous subsurface formation since the homogeneity assumption
of this formation is not valid. Over the past twenty years, stochastic approach and Monte Carlo technique have been utilized
very efficiently to understand the groundwater flow behavior. However, these techniques require lots of computational and
numerical efforts according to the various researchers’ comments. Therefore, utilizing new techniques with much less computational
efforts such as Artificial Neural Network (ANN) in the prediction of the stochastic behavior for the groundwater based on
heterogeneous subsurface formation is highly appreciated. The current paper introduces the ANN technique to investigate and
predict the stochastic behavior of a well draw down in a confined aquifer based on subsurface heterogeneous hydraulic conductivity.
Several ANN models are developed in this research to predict the unsteady two dimensional well draw down and its stochastic
characteristics in a confined aquifer. The results of this study showed that ANN method with less computational efforts was
very efficiently capable of simulating and predicting the stochastic behavior of the well draw down resulted from the continuous
constant pumping in the middle of a confined aquifer with subsurface heterogeneous hydraulic conductivity. 相似文献
32.
Alaa Farag Abd El-Rehim 《Journal of Materials Science》2008,43(4):1444-1450
The effect of grain size as well as creep temperature on the primary and secondary creep parameters of Sn–3 wt.% Bi alloy
has been studied. It was found that the creep parameters α, β, and έ
s were decreased with increasing grain size. This was explained in view of the dislocation interaction with the defects and
different inclusions in the matrix. For both the primary and secondary creep, the activation energies estimated indicate that
the rate-controlling mechanism is the grain boundary-sliding mechanism. 相似文献
33.
Coupled reliability model of biodeterioration, chloride ingress and cracking for reinforced concrete structures 总被引:1,自引:0,他引:1
Emilio Bastidas-Arteaga Mauricio Snchez-Silva Alaa Chateauneuf Moema Ribas Silva 《Structural Safety》2008,30(2):110-129
Maintaining and operating civil infrastructure systems has been recognized as a critical issue worldwide. Among all possible causes of safety reduction during the structural lifetime, deterioration is particularly important. Structural deterioration is usually a slow time-dependent process controlled by safety and operation threshold specifications. This paper presents a model of RC deterioration by coupling biodeterioration (i.e., chemical, physical and mechanical action of live organisms), steel corrosion, and concrete cracking. The final purpose of the model is to compute the reduction of the concrete section and the area of steel reinforcement in order to assess the change of structural capacity with time. Given the uncertainties in both the parameters and the model, the probabilistic nature of loads, the material properties and the diffusion process are taken into account to evaluate structural reliability. The model is illustrated with an example where the inelastic behavior of a pile subject to random loading is considered. The results of the analysis have shown that the effect of biodeterioration on the structural performance is significant and can cause an important reduction of its lifetime. On the whole, the paper states that modeling the effects of biodeterioration in RC structures should be included as part of infrastructure planning and design, especially, when they are located in aggressive environments. 相似文献
34.
Machine Learning - The coronavirus disease 2019 (COVID-19) global pandemic poses the threat of overwhelming healthcare systems with unprecedented demands for intensive care resources. Managing... 相似文献
35.
Silicon - Controlling pore structure, e.g. pore diameter, size and distribution of porous silicon (PS) is highly needed for technological applications such as microfluidic operation and filtration... 相似文献
36.
Lohala Saurav Alsadoon Abeer Prasad P. W. C. Ali Rasha S. Altaay Alaa Jabbar 《Multimedia Tools and Applications》2021,80(17):25453-25476
Multimedia Tools and Applications - Accurate food image classification is often critical to accurately monitor the dietary assessment to reduce the risk of different heart-related diseases,... 相似文献
37.
38.
Alaa El‐Din H. Sayed Usama M. Mahmoud Fatma Essa 《Microscopy research and technique》2019,82(4):443-451
The microstructure of the oral cavity and alimentary canal of herbivorous fish Siganus rivulatus collected from the Red Sea were investigated by using scanning electron microscope (SEM). The results showed that S. rivulatus has three types of teeth, tri‐cusped, bi‐cusped, and papilliform. A taste bud (Type I) was recorded in the oropharyngeal cavity. Characteristic styles of microridges on the cell's surface inside the buccal cavity were recorded. Also, the distribution of the mucous cells in the lining of the mouth cavity, alimentary canal was observed. Mucosal folds along the distinct parts of alimentary canal, showed characteristic pattern which was complex in the intestinal mucosa. The results concluded that there are characteristic microstructures according to feeding habitat compared with other bony fishes. 相似文献
39.
This work is concerning with the study of the thermoelastic damping of a nanobeam resonator in the context of the two-temperature generalized thermoelasticity theory. An explicit formula of thermoelastic damping has been derived when Young’s modulus is a function of the reference temperature. Influences of the beam height and Young’s modulus have been studied with some comparisons between the Biot model and the Lord–Shulman model (L–S) for one- and two-temperature types. Numerical results show that the values of the thermal relaxation parameter and the two-temperature parameter have a strong influence on thermoelastic damping at nanoscales. 相似文献
40.
Hussain A. Badran Khietam Abd. AL-Aladil Haidar G. Lazim Alaa Y. Al-Ahmad 《Journal of Materials Science: Materials in Electronics》2016,27(3):2212-2220
The CdO NPs was synthesized using the sol–gel method and the nanoparticles were characterized using an UV–Vis spectrophotometer, with shape and size were examined by SEM and XRD. The XRD analysis respects the Bragg’s law and confirmed the crystalline nature of CdO nanoparticles. From the XRD, the average size of CdO NPs was found to be around 41 nm. The photoluminescence spectra of the CdO NPs, as recorded at room temperature, were excited at 300 nm wavelength. The broad emission peaks were between 600 and 650 nm (orange emission). The optical limiting performance of the nanocomposite was described in the sol–gel state. Also, this study has observed and studied the diffraction rings generated in CdO NPs using the same CW laser. The number of rings increases almost exponentially with an increasing volume fraction of SiO2 in the nanocomposites. The refractive index change, Δn, and effective nonlinear refractive index, n 2, were found to be 10?4 and 10?8 cm2/W, respectively. The effective nonlinear refractive index, n 2, was determined based on the observed number of rings. The threshold values of the CdO, CdO–2SiO2 and CdO–5SiO2 nanocomposites are 7.1, 6.55 and 6.34 mW, respectively. This large nonlinearity is attributed to the thermal effect. The present studies suggest that the nanocomposite is a potential candidate for optical device applications such as the optical limiters. The thermal blooming technique was applied to evaluate the thermo-optic coefficient and thermal diffusivity of the CdO NPs. In the thermal blooming experimental setup a transistor–transistor logic modulated CW laser of wavelength 532 nm was used as the excitation source. 相似文献