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141.
Lionel Mathelin Kévin Kasper Hisham Abou-Kandil 《Archives of Computational Methods in Engineering》2018,25(1):103-120
This paper introduces a method for efficiently inferring a high-dimensional distributed quantity from a few observations. The quantity of interest (QoI) is approximated in a basis (dictionary) learned from a training set. The coefficients associated with the approximation of the QoI in the basis are determined by minimizing the misfit with the observations. To obtain a probabilistic estimate of the quantity of interest, a Bayesian approach is employed. The QoI is treated as a random field endowed with a hierarchical prior distribution so that closed-form expressions can be obtained for the posterior distribution. The main contribution of the present work lies in the derivation of a representation basis consistent with the observation chain used to infer the associated coefficients. The resulting dictionary is then tailored to be both observable by the sensors and accurate in approximating the posterior mean. An algorithm for deriving such an observable dictionary is presented. The method is illustrated with the estimation of the velocity field of an open cavity flow from a handful of wall-mounted point sensors. Comparison with standard estimation approaches relying on Principal Component Analysis and K-SVD dictionaries is provided and illustrates the superior performance of the present approach. 相似文献
142.
Abdalla Hisham Xiong Hu Wahaballa Abubaker Ramadan Mohammed Qin Zhiguang 《Wireless Networks》2021,27(2):1063-1076
Wireless Networks - With the rapid popularity and wide adoption of cloud storage, providing privacy-preserving by protecting sensitive information becomes a matter of grave concern. The most... 相似文献
143.
144.
Stability of gravitationally unstable double diffusive transient boundary layers with variable viscosity in porous media 下载免费PDF全文
Nasser Sabet Hassan Hassanzadeh Jalal Abedi 《American Institute of Chemical Engineers》2017,63(6):2471-2482
We study the double diffusive convection (DDC) in porous media through linear stability analysis (LSA) and direct numerical simulations (DNS). Unlike the previous studies that assume static solutal or thermal fields, the developed model is able to capture the transient behavior of both fields. We show that under the assumption of static field, the role of Lewis number cannot be distinguished. Under transient fields, we conclude that higher Lewis numbers result in earlier instability of the boundary layers. Moreover, the effect of viscosity contrast is explained in terms of the mobility of the boundary layer. The DNS results confirm the validity of LSA predictions. We also obtain the critical Rayleigh number and show that in the presence of viscosity contrast, it can be much smaller than the conventional limit of 4π2. This study provides a better understanding of the transient nature of DDC in the presence of viscosity variations. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2471–2482, 2017 相似文献
145.
Nasser A.M. Barakat K.A. Khalil Faheem A. Sheikh A.M. Omran Babita Gaihre Soeb M. Khil Hak Yong Kim 《Materials science & engineering. C, Materials for biological applications》2008,28(8):1381-1387
In the present study, subcritical water and alkaline hydrolysis methods are proposed methodologies for extraction of natural hydroxyapatite bioceramic from bovine bone. In these processes, the bovine bones powder were treated by high pressure water at 250 °C for 1 h and 25% (wt) sodium hydroxide at 250 °C for 5 h, respectively. Also the conventional calcination methodology has been utilized as well (T = 850 °C for 1 h). The obtained apatites from the three treatment processes have been characterized by powder X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT IR), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), electron scanning microscopy (SEM), energy dispersive X-ray analysis (EDX) and field emission scanning electron microscopy (FE SEM). FT IR and XRD results affirmed that both the proposed methods and the traditional one can eliminate the collagen and other organic materials present in the bovine bones. The physiochemical characterizations for the obtained apatites have proved that the subcritical water and the alkaline hydrolysis relatively preserve the carbonate content present in the biological apatite, so they yield carbonated hydroxyapatite which is medically preferable. While, the thermal process produces almost hydroxyapatite carbonate-free. 相似文献
146.
Network reliability analysis has received considerable attention and is thus widely studied to predict and prevent any network failure. However, most of such works presume perfectly reliable nodes. Although a few studies have considered both link and node failures, none of these methods has utilized the minimal paths or cuts, which are considered as fundamental approaches in the network reliability evaluation. An efficient method for deducing the minimal cutsets of a system subject to both link and node failures from the minimal cutsets of the system, which assumes perfect node reliability, is presented. The proposed method does not require re-enumeration of minimal cutsets for the additional consideration of the node failures. For a simple extension of such a method, the proposed approach can be embedded in any exact or approximate algorithm to account for link failures as well as node failures. As a result, the application of this method would be more realistic and valuable in practice for the reliability evaluation of networks with unreliable nodes. 相似文献
147.
Mohammed A. Amin Mohamed M. Ibrahim Adil A. Gobouri Gaber A.M. Mersal Nasser Y. Mostafa Tariq Altalhi Salih Al-Juaid 《International Journal of Hydrogen Energy》2017,42(41):25980-25995
A new chlorobis(2-aminomethylbenzimidazole)zinc(II) perchlorate complex [Zn(AMB)2Cl](ClO4) 1 has been synthesized and characterized. Spectral and X-ray structural features led to the conclusion that the zinc(II) complex has a square-pyramidal environment around zinc(II) center with coordination chromophore ZnN4Cl. Different amounts of complex 1 were supported on glassy carbon (GC) electrode yielding three GC-supported complex 1 electrodes with different loading densities (0.2, 0.4, and 0.8 mg cm?2). These electrodes were tested as molecular electrocatalysts for the hydrogen evolution reaction (HER) in phosphate buffer aqueous solutions (pH 7), employing linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results showed that GC-complex 1 catalysts are highly active for the HER, and this catalytic activity enhances with the loading density. The one with the highest loading density (0.8 mg cm?2) exhibited high HER catalytic activity with low onset potential of ?140 mV vs. RHE and a high exchange current density of 0.22 mA cm?2. It required an overpotential of 240 mV to achieve a current density of 10 mA cm?2. It also recorded a turnover frequency (TOF) of 1722 mol of hydrogen per mole of catalyst per hour at overpotential 500 mV, which is comparable with the most active molecular electrocatalysts reported in the literature for H2 generation from aqueous neutral solutions. A catalytic cycle is proposed for the generation of hydrogen by complex 1 and the mechanism of the HER is discussed based on the measured Tafel slope (140 mV dec?1). 相似文献
148.
Somayeh S. Tarighat Fei Fei Eun Ji Joo Hisham Abdel-Azim Lu Yang Huimin Geng Khuchtumur Bum-Erdene I. Darren Grice Mark von Itzstein Helen Blanchard Nora Heisterkamp 《International journal of molecular sciences》2021,22(22)
Environmentally-mediated drug resistance in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) significantly contributes to relapse. Stromal cells in the bone marrow environment protect leukemia cells by secretion of chemokines as cues for BCP-ALL migration towards, and adhesion to, stroma. Stromal cells and BCP-ALL cells communicate through stromal galectin-3. Here, we investigated the significance of stromal galectin-3 to BCP-ALL cells. We used CRISPR/Cas9 genome editing to ablate galectin-3 in stromal cells and found that galectin-3 is dispensable for steady-state BCP-ALL proliferation and viability. However, efficient leukemia migration and adhesion to stromal cells are significantly dependent on stromal galectin-3. Importantly, the loss of stromal galectin-3 production sensitized BCP-ALL cells to conventional chemotherapy. We therefore tested novel carbohydrate-based small molecule compounds (Cpd14 and Cpd17) with high specificity for galectin-3. Consistent with results obtained using galectin-3-knockout stromal cells, treatment of stromal-BCP-ALL co-cultures inhibited BCP-ALL migration and adhesion. Moreover, these compounds induced anti-leukemic responses in BCP-ALL cells, including a dose-dependent reduction of viability and proliferation, the induction of apoptosis and, importantly, the inhibition of drug resistance. Collectively, these findings indicate galectin-3 regulates BCP-ALL cell responses to chemotherapy through the interactions between leukemia cells and the stroma, and show that a combination of galectin-3 inhibition with conventional drugs can sensitize the leukemia cells to chemotherapy. 相似文献
149.
Nasser A. Hassan Tahia K. Mohamed Omaima M. Abdel Hafez Martin Lutz Christoph C. Karl Wolfgang Wirschun Yaseen A. Al-Soud Johannes C. Jochims 《Advanced Synthesis \u0026amp; Catalysis》1998,340(2):151-159
The 1-aza-2-azoniaallene salt 8 prepared from 3-acetyl coumarin via the hydrazone 6 and the (chloroalkyl)azo derivative 7 reacts with nitriles to afford the 3-(3-chromenyl)-1,2,4-triazolium salts 11a–d . With diisopropylcarbodiimide the triazolium salt 13 and with norborene a tricyclic pyrazolium salt 14 are obtained. Concurrent to these cycloadditions the by-product 12 is formed by intramolecular cyclization of the cumulene 8 . Similarly, the intramolecular cyclization product 18 is isolated as the sole product when the 1-aza-2-azoniaallene salt 17a (prepared from the ethyl carbazone of camphor by chlorination and treatment of the product 16a with SbCl5) was treated with nitriles, carbodiimides or alkenes. In contrast, 1,2,4-triazolium salts 20a–c , 23c , respectively pyrazolium salts 20d–f , and 1,3,4-thiadiazolium salts 23a,b are obtained by reaction of the 1-aza-2-azoniaallene salt 17b with nitriles, respectively alkenes, alkynes, diisopropylcarbodiimide, and isothiocyanates. The constitutions of two of these products ( 20e, 23a ) were secured by X-ray structural analysis. 相似文献
150.