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631.
Maher M. Hamed Rafie H. Abu-Eittah Zein Mobark Mohamed M. Abdou 《International journal of quantum chemistry》1992,44(3):379-392
The electronic absorption spectra of tryptamine, 5-methoxytryptamine, 6-fluorotryptamine, N-acetyl-5-hydroxytryptamine, gramine, and melatonin were investigated. The observed transitions were π–π*, and the values of band maxima and intensity reflected an extent of interaction between the indole ring and the alkylamine side chain. Molecular orbital calculations at the level of INDO /S –CI were performed on all the studied molecules. State functions and transition energies were calculated. The correspondence between the experimental and theoretical results was satisfactory. © 1992 John Wiley & Sons, Inc. 相似文献
632.
A speckle photography technique has been applied to measuring the velocity profiles of laminar and turbulent flow through pipes of circular cross-section. A single exposure photography technique has been used to visualize slow fluid flow. The fluids used were seeded with tracer particles whose size range from 20 to about 120 μm in diameter. A mathematical expression representing the recorded intensity is presented. A single exposure with a long exposure time was taken on a holographic film material. The recorded intensity was represented by the convolution product of the image formed and a rectangular function representing a one-dimensional continuous motion. The analysis shows that the intensity distribution of the Fourier spectrum of the diffracted image follows a sinc2 function on a noise background representing the scattered light of the tracer particles. 相似文献
633.
The autohesion (tack) and cohesion of a random styrene-butadiene elastomer have been examined as a function of test temperature and speed using a T-peel geometry. Both properties have been reduced to a single master curve by horizontally shifting the data with the same set of shift factors. The cohesive strength increases with increasing reduced test rate RaT and appears to approach a plateau at the highest rates. Tack also increases with RaT but decreases abruptly at a critical rate and peeling the occurs in a stick-slip fashion. Tack again increases at sufficiently high test rates. In the range of rates where tack is maximized, its value is essentially the same as its cohesive strength. Above or below this range, tack is substantially less than the elastomer's cohesive strength. Mechanisms are proposed to explain why relative tack (i.e., tack divided by cohesive strength) is not a simple measure of the extent of completion of a tack bond and may indeed be equal to one in spite of incomplete tack bond formation. 相似文献
634.
Nasrin ALIASGHARLOU Farzin ASGHARI SANA Saba KHOSHBAKHT Pezhman ZOLFAGHARI Hamed CHARKHIAN 《Turkish Journal of Chemistry》2020,44(6):1723
In this study, boric acid (BA) is employed as a crosslinking agent to improve the characteristics of two commonly used polymeric films, ethyl cellulose (EC) and polyvinyl alcohol (PVA), for topical drug delivery applications. The developed films are characterized by FTIR spectroscopy and SEM analysis. The results show that the surfaces of the prepared films are even and transparent, except for the BA-modified EC sample. The initial cumulative release for erythromycin (EM) is found to be 0.30 and 0.36 mg/mL for EC and PVA films, which drops to 0.25 and 0.20 mg/mL after BA crosslinking, respectively, after 1 h at 25 °C. Further, the developed formulations are stable for 75 days. Also, the antibacterial activity of the developed formulations is investigated against S. aureus (ATCC® 25923™ and ATCC® 29213™). The obtained data confirm that the application of BA as the crosslinking agent extends the release of EM from EC and PVA polymeric films. The findings of this study suggest that BA-crosslinked EC and PVA films are promising carriers for controlled topical drug delivery applications. 相似文献
635.
The colored neighborhood metric for sparse graphs was introduced by Bollobás and Riordan [BR11]. The corresponding convergence notion refines a convergence notion introduced by Benjamini and Schramm [BS01]. We prove that even in this refined sense, the limit of a convergent graph sequence (with uniformly bounded degree) can be represented by a graphing. We study various topics related to this convergence notion such as: Bernoulli graphings, factor of i.i.d. processes and hyperfiniteness. 相似文献
636.
Hamed Yarmand Julie S. Ivy Brian Denton Alun L. Lloyd 《European Journal of Operational Research》2014
In this article, we consider a decision process in which vaccination is performed in two phases to contain the outbreak of an infectious disease in a set of geographic regions. In the first phase, a limited number of vaccine doses are allocated to each region; in the second phase, additional doses may be allocated to regions in which the epidemic has not been contained. We develop a simulation model to capture the epidemic dynamics in each region for different vaccination levels. We formulate the vaccine allocation problem as a two-stage stochastic linear program (2-SLP) and use the special problem structure to reduce it to a linear program with a similar size to that of the first stage problem. We also present a Newsvendor model formulation of the problem which provides a closed form solution for the optimal allocation. We construct test cases motivated by vaccine planning for seasonal influenza in the state of North Carolina. Using the 2-SLP formulation, we estimate the value of the stochastic solution and the expected value of perfect information. We also propose and test an easy to implement heuristic for vaccine allocation. We show that our proposed two-phase vaccination policy potentially results in a lower attack rate and a considerable saving in vaccine production and administration cost. 相似文献
637.
Nowadays, due to some social, legal, and economical reasons, dealing with reverse supply chain is an unavoidable issue in many industries. Besides, regarding real-world volatile parameters, lead us to use stochastic optimization techniques. In location–allocation type of problems (such as the presented design and planning one), two-stage stochastic optimization techniques are the most appropriate and popular approaches. Nevertheless, traditional two-stage stochastic programming is risk neutral, which considers the expectation of random variables in its objective function. In this paper, a risk-averse two-stage stochastic programming approach is considered in order to design and planning a reverse supply chain network. We specify the conditional value at risk (CVaR) as a risk evaluator, which is a linear, convex, and mathematically well-behaved type of risk measure. We first consider return amounts and prices of second products as two stochastic parameters. Then, the optimum point is achieved in a two-stage stochastic structure regarding a mean-risk (mean-CVaR) objective function. Appropriate numerical examples are designed, and solved in order to compare the classical versus the proposed approach. We comprehensively discuss about the effectiveness of incorporating a risk measure in a two-stage stochastic model. The results prove the capabilities and acceptability of the developed risk-averse approach and the affects of risk parameters in the model behavior. 相似文献
638.
Hamed KhatamMarek-Jerzy Pindera 《International Journal of Plasticity》2011,27(10):1537-1559
Construction of mechanism-based plasticity theories for the homogenized response of heterogeneous materials requires identification of plastic deformation modes as a function of loading direction relative to the microstructural details. Herein, we employ an efficient homogenization theory to identify for the first time such deformation modes in plates under plane stress with hexagonal arrays of circular holes at small and intermmediate pore volume fractions, and establish their relation to the branches of initial and subsequent yield and limit surfaces. Newly introduced maps of the intrinsic geometric features of point-wise yield surfaces provide full-field picture of the investigated microstructures’ propensity for plastic strain initiation and localization. The identified characteristic plastic modes provide a rational explanation for the evolving geometric features of subsequent yield and limit surfaces whose branches represent different plastic flow mechanisms, as well as a basis for the construction of a mechanism-based homogenized plasticity theory for use in structural analysis algorithms. The results suggest the need for composite yield surfaces comprised of multiple branches in the construction of mechanism-based homogenized plasticity theory for the investigated class of porous materials. 相似文献
639.
Salari M Aboutalebi SH Konstantinov K Liu HK 《Physical chemistry chemical physics : PCCP》2011,13(11):5038-5041
We report the synthesis of self-organized titania nanotubes and nanocrystalline titania powders employing an alternative and novel approach. Integrating these nanostructures in a binder-free working electrode improved the capacitance up to 911 μF cm(-2), which is around one to two orders of magnitude higher than the conventional electric double layer capacitors. 相似文献
640.
Takai A Ataee-Esfahani H Doi Y Fuziwara M Yamauchi Y Kuroda K 《Chemical communications (Cambridge, England)》2011,47(27):7701-7703
A new type of platinum nanowire with a bumpy surface "Pt nanoworm" is electrochemically synthesized in mesochannels of mesoporous silica films with the assistance of a nonionic surfactant (C(16)EO(8)). 相似文献