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排序方式: 共有173条查询结果,搜索用时 15 毫秒
41.
I. Nurhuda N.T.K. Lam E.F. Gad I. Calderone 《International Journal of Solids and Structures》2010,47(18-19):2591-2599
A new model of the Log-Normal form for predicting the cumulative probabilistic distribution of strength in annealed glass panels is presented in this paper. The proposed model, which is supported by experimental evidences, shares certain features that are common with predictions by the Weibull’s model. However, as the dimension of the panel is above a certain limit, the strength of glass as predicted by the new model is much less sensitive to any further increase in the panel dimension than strength predicted by the Weibull’s model. This has important implications to the engineering design and risk assessments of glass facades in the future. The proposed alternative model was derived from results obtained from Monte Carlo simulations of non-interacting Griffith flaws based on principles of fracture mechanics. As interactions between flaws have been neglected in the analyses presented in the paper, the proposed model is intended to be applicable to glazing panels which contain widely spaced flaws. Results from physical experimentation in support of the simulation model have been presented in the paper. 相似文献
42.
El-Sayed Hassan A. Moustafa Ahmed H. Farargy Ahmed F. El Mohammed Samar M. Saudy Esraa Gad Emad M. 《Russian Journal of General Chemistry》2022,92(4):709-717
Russian Journal of General Chemistry - The present study is devoted to functionalization of ethyl 2-{[3-cyano-6-(4-cyanophenyl)-4-(2,4-dichlorophenyl)pyridin-2-yl]oxy}acetate (1) by triazole-,... 相似文献
43.
The dynamics and thermodynamics of small Ar(n) (+) clusters, n=3, 6, and 9, are investigated using molecular dynamics (MD) and exchange Monte Carlo (MC) simulations. A diatomic-in-molecule Hamiltonian provides an accurate model for the electronic ground state potential energy surface. The microcanonical caloric curves calculated from MD and MC methods are shown to agree with each other, provided that the rigorous conservation of angular momentum is accounted for in the phase space density of the MC simulations. The previously proposed projective partition of the kinetic energy is used to assist MD simulations in interpreting the cluster dynamics in terms of inertial, internal, and external modes. The thermal behavior is correlated with the nature of the charged core in the cluster by computing a dedicated charge localization order parameter. We also perform systematic quenches to establish a connection with the various isomers. We find that the Ar(3) (+) cluster is very stable in its linear ground state geometry up to about 300 K, and then isomerizes to a T-shaped isomer in which a quasineutral atom lies around a charged dimer. In Ar(6) (+) and Ar(9) (+), the covalent trimer core is solvated by neutral atoms, and the weakly bound solvent shell melts at much lower energies, occasionally leading to a tetramer or pentamer core with weakly charged extremities. At high energies the core itself becomes metastable and the cluster transforms into Ar(2) (+) solvated by a fluid of neutral argon atoms. 相似文献
44.
Intensity perturbations in forbidden radiative transitions due to cubic anharmonic mixing involving the inducing mode and a totally symmetric progression-forming mode are discussed. It is shown that such mixing will lead to deviations from mirror symmetry of the absorption and fluorescence structure because the destructive-constructive interference pattern which prevails in absorption is different to that in emission. This analysis is applied to intensities in the 2600 Å system of benzene. Moderate cubic coupling energies (ca. 10 cm-1) have marked effects on intensity distributions even when the interacting levels are 200 cm-1 apart. The splitting of the progressions 10 n 61 2 and 1 n 062 1 into two sub-progressions (l=0, 2) is linearly dependent on the extent of vibronic excitation in the a 1g mode v 1. These effects are amenable to experimental detection. 相似文献
45.
Summary The MHD stability of a liquid jet (radiusR
0 and density ϱ) under the influence of self-gravitating force has traditionally been studied using a normal-mode type of analysis.
The dispersion relation is obtained and studied analytically and numerically. The axial magnetic fields inside and outside
the jet have always stabilizing effects. The transverse magnetic field has a destabilizing effect. It is found that the largest
doman of instability is fastly shrinking (as α> ?) with increasingH
0 /H
G
values,H
G
4(4πGϱ2
R
2
0 μ)1/2, whereG is the gravitational constant. Some reported works are recovered as limiting cases from the present work. 相似文献
46.
Results are given for the mechanical, thermal and flammability properties of polyisocyanurate resins obtained from hexamethylene diisocyanate by bis-(tributyltin)-oxide catalysis. It is shown that the mechanical properties of the isocyanurate resins and of their glass fibre-reinforced composites are comparable with those of commercial epoxy and polyester resins. The thermal stability and the flame retardance of the isocyanurate resins are far better than of epoxies or polyesters. 相似文献
47.
Rana Ahmed Youness Reem Amr Assal Shahira Mohamed Ezzat Mohamed Zakaria Gad Amira Abdel Motaal 《Natural product research》2020,34(10):1475-1480
AbstractThis study focused on studying the impact of flavonoids isolated from Cleome droserifolia on HCC cell lines and to further unveil their possible impact on TP53 and its downstream tumor suppressor miRNAs. Three flavonol glycosides were isolated from C. droserifolia namely, Isorhamnetin-3-O-β-D-glucoside (1), Quercetin-3`-methoxy-3-O-(4``-acetylrhamnoside)-7-O-α-rhamnoside (2), and Kaempferol-4`-methoxy-3,7-O-dirhamnoside (3). They showed a concentration and time dependent reduction in cellular viability and anchorage-independent growth of HCC cells. Moreover, they exhibited a decrease in the migrating capacity of HepG2 cells in a pattern similar to positive control cells. (2) Showed the most potent effects in halting HCC tumorigenic activity (IC50=36?±?1.70?µM) and a repression of the cellular proliferation rate of HepG2 cells. Restoration of TP53 and its downstream tumor suppressor miRNAs; miR-15a, miR-16, miR-34a by (2) was observed. Moreover, attenuation of (2) mediated actions was shown upon using anti-miR-15a and anti-miR-16. To conclude, this study crystallizes a novel role of C. droserifolia in harnessing HCC progression in-vitro with a possible contribution of TP53/miR-15a/miR-16. 相似文献
48.
Gad Fischer 《Chemical physics》1974,4(1):62-79
The 3000 Å, (1B2 ← 1A1), absorption system of phenanthrene in durene crystals at 4°K illustrates an electronic transition, which is subject to near-resonance vibronic perturbations whose effect is intermediate to both the small (sparse intermediate) and large molecule (statistical) limits. Both broad (300 cm?1) and narrow (10 cm?1) lines are evident. A model is proposed which incorporates both these features by fast allowing for a consideration of the interaction between a small number of discrete levels, those associated with the largest coupling, followed by a treatment of the broadening of these levels through interaction with the remaining near continuum of states of the lower electronic state. Thus, one and the same electronic state provides both a sparse and dense manifold of levels. An important result of the model is that in terms of absorption intensities all the lines emerge with the same heights but differ in widths. When the intensities are summed with respect to energies this aspect is obscured. This approach has been shown to satisfactorily reproduce many of the features of the 1B2 absorption spectra of phenanthrene and phenanthrene-d10. The 1B2 absorption systems have also been measured in the vapour phase and fine structure attributable to vibronic coupling and sequence band development are discussed. 相似文献
49.
Amihood Amir Yonatan Aumann Gad M. Landau Moshe Lewenstein Noa Lewenstein 《Journal of Algorithms in Cognition, Informatics and Logic》2000,37(2):247
Let a text string T of n symbols and a pattern string P of m symbols from alphabet Σ be given. A swapped version T′ of T is a length n string derived from T by a series of local swaps (i.e., t′ℓ ← tℓ + 1 and t′ℓ + 1 ← tℓ), where each element can participate in no more than one swap. The pattern matching with swaps problem is that of finding all locations i for which there exists a swapped version T′ of T with an exact matching of P in location i of T′. It has been an open problem whether swapped matching can be done in less than O(nm) time. In this paper we show the first algorithm that solves the pattern matching with swaps problem in time o(nm). We present an algorithm whose time complexity is O(nm1/3 log m log σ) for a general alphabet Σ, where σ = min(m,Σ). 相似文献
50.
A.D. Jordan Gad Fischer Katharina Rokos I.G. Ross 《Journal of Molecular Spectroscopy》1973,45(2):173-198
The following spectra have been measured at 4 K, in three polarizations: absorption of quinoxaline in durene, durene-d14, naphthalene and naphthalene-d10, and of quinoxaline-d6 in durene and naphthalene. The polarized phosphorescence of quinoxaline-d6 in durene is also recorded.The analyses permit unusually extensive assignments of excited state vibrational frequencies. Also noted are various crystal effects: isotope shifts, modification of molecular frequencies, prominence of Herzberg-Teller origins, site splittings, effects of perdeuterated hosts, and polarization ratios. An unusual line-splitting seen in durene is analyzed as a resonance between coincident a1 and b1 vibrations of the quinoxaline molecule, coupled through the exciton bands of the host. 相似文献