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排序方式: 共有188条查询结果,搜索用时 11 毫秒
51.
Yair Margalit Sara Abramovich-Bar Yair Bamberger Shionto Levy Shmuel Zitrin 《Journal of Energetic Materials》2013,31(1-4):363-376
In order to evaluate the applicability of NMR to the analysis of explosives, the method was used to analyse explosives from actual cases. The results were then compared with results from other analytical methods, mainly TLC and GC/MS. For unexploded samples NMR was found to be a simple, fast and reliable method, often allowing the identification of mixtures without pre-separation. Some post-explosion samples were also successfully analysed by NMR. Although sensitivity problems still exist, NMR showed a surprisingly promising prospects for the difficult field of post-explosion analysis. 相似文献
52.
Mathieu Dutto Dominique Goeuriot Sébastien Saunier Sergio Sao-Joao Sylvain Marinel Nachum Frage Shmuel Hayun 《International Journal of Applied Ceramic Technology》2020,17(2):751-760
Reaction-bonded boron carbide composites were fabricated by both microwave (under Ar/10% H2) and conventional heating (under vacuum or Ar/10% H2). Silicon carbide (SiC) formation occurred in all cases and was slightly favored in the case of microwave heating under Ar/H2. The resulting microstructures were influenced by the heating process and atmosphere; the SiC existed in the form of needles with conventional heating under vacuum. SiC small polygonal grains were present after microwave heating under Ar/H2. Both the atmosphere and the electromagnetic field influence the SiC morphology. Despite this difference, the hardness and toughness of composites obtained by both heating techniques were similar. 相似文献
53.
Shmuel Zitrin 《Journal of Energetic Materials》2013,31(1-4):199-214
The Analysis of trace amounts of explosives from post-explosion debris–one of the most difficult problems in forensic chemistry-is still carried out in many laboratories by chromatographic methods only. In recent years several new methods have been applied to the analysis of explosives. These include mass spectrometric methods (GC/MS, LC/MS and MS/MS) and NMR methods. The possible application of these methods to post-explosion analysis is discussed and various aspects of the techniques are reviewed and compared. The choice of capillary column GC/MS as a routine method in the Israel Police laboratory is explained and examples from actual cases are given. 相似文献
54.
Gas chromatography/mass spectrometry (GC/MS) using a 15 m long capillary column has been employed in our laboratory for the analysis of explosives. The technique is suitable for most of the common military explosives. Nitroaromatic compounds like TNT were analysed easily and with high sensitivity and so were the volatile nitrate esters like glycerine trinitrate. Success was also achieved in the analysis of PETN and RDX, which had previously been reported to pose problems under GC conditions. Tetryl was shown to decompose during the analysis but its decomposition product was well defined and could serve as evidence to the presence of tetryl. The method was successfully applied to post-explosion debris from actual cases. 相似文献
55.
Many industries are exposed to weather risk. Weather derivatives can play a key role in hedging and diversifying such risk because the uncertainty in a company's profit function can be correlated to weather condition which affects diverse industry sectors differently. Unfortunately the weather derivatives market is a classical example of an incomplete market that is not amenable to standard methodologies used for derivative pricing in complete markets. In this paper, we develop an equilibrium pricing model for weather derivatives in a multi-commodity setting. The model is constructed in the context of a stylized economy where agents optimize their hedging portfolios which include weather derivatives that are issued in a fixed quantity by a financial underwriter. The supply and demand resulting from hedging activities and the supply by the underwriter are combined in an equilibrium pricing model under the assumption that all agents maximize some risk averse utility function. We analyze the gains due to the inclusion of weather derivatives in hedging portfolios and examine the components of that gain attributable to hedging and to risk sharing. 相似文献
56.
Ellis Shmuel; Ganzach Yoav; Castle Evan; Sekely Gal 《Canadian Metallurgical Quarterly》2010,95(1):122
In the current study, we compared the effect of personal and filmed after-event reviews (AERs) on performance, and the role that self-efficacy plays in moderating and mediating the effects of these 2 types of AER on performance. The setting was one in which 49 men and 63 women participated twice in a simulated business decision-making task. In between, participants received a personal AER, watched a filmed AER, or had a break. We found that individuals who participated in an AER, whether personal or filmed, improved their performance significantly more than those who did not participate in a review. Furthermore, there was no significant difference in performance improvement between the personal and the filmed AER, which suggests that the 2 are quite similar in their effect. We also found that the differences in performance improvement between the personal AER group and the control group were somewhat greater than those found in the filmed AER group. Self-efficacy mediated the effect of AER on performance improvement in both types of AER. In addition, the effect of AER on performance improvement was moderated by initial self-efficacy in the personal but not in the filmed AER: The personal AER was more effective, the higher the initial self-efficacy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Shmuel Malkin 《Israel journal of chemistry》1998,38(3):261-268
Charland et al. (Biochim. Biophys. Acta 1992 , 1098, 261–265) obtained photoacoustic data from sugar maple tree leaves, in which the photobaric part of the photoacoustic signal declined in time following a transition from high light to low light level, which they interpreted as indicating stromal and plasmal oxygen-consuming processes. Here, a simple mathematical model of oxygen diffusion, which includes a continuous distribution of oxygen-consuming sinks in the diffusion path from the photosynthetic membrane to the inner air phase, is presented. The model explains the main features of the dependence of the steady-state signal on the modulation frequency and the light intensity, although the numerical agreement between the data and the results of the model is only semi-quantitative, which is discussed. It turns out that at sufficiently high light intensity, or at a short time after a previous exposure to a high light level, the effect of oxygen consumption tends to zero because a high stromal oxygen concentration is built up which is saturating for the uptake process. Within this limitation, the merit of the photoacoustic signal as an indicator for photosynthetic oxygen evolution is preserved, answering recent doubts. 相似文献
58.
59.
Michele Flammini Gianpiero Monaco Luca Moscardelli Mordechai Shalom Shmuel Zaks 《Journal of Parallel and Distributed Computing》2008
We consider the problem of grooming paths in all-optical networks with tree topology so as to minimize the switching cost, measured by the total number of used ADMs. We first present efficient approximation algorithms with approximation factor of 2ln(δ⋅g)+o(ln(δ⋅g)) for any fixed node degree bound δ and grooming factor g, and 2lng+o(lng) in unbounded degree directed trees, respectively. In the attempt to extend our results to general undirected trees, we completely characterize the complexity of the problem in star networks by providing polynomial time optimal algorithms for g≤2 and proving the intractability of the problem for any fixed g>2. While for general topologies, the problem was known to be NP-hard g not constant, the complexity for fixed values of g was still an open question. 相似文献
60.
Rakesh Das Shmuel Gershon Benny Bar-On Maryam Tadayon Amir Ayali Bat-El Pinchasik 《Journal of the Royal Society Interface》2022,19(188)
The female locust has a unique mechanism for digging in order to deposit its eggs deep in the ground. It uses two pairs of sclerotized valves to displace the granular matter, while extending its abdomen as it propagates underground. This ensures optimal conditions for the eggs to incubate and provides them with protection from predators. Here, the direction-dependent biomechanics of the locust''s major, dorsal digging valves are quantified and analysed under forces in the physiological range and beyond, considering the hydration level as well as the females'' sexual maturation state. Our findings reveal that the responses of the valves to compression forces in the digging and propagation directions change upon sexual maturation to follow their function and depend on environmental conditions. In addition, mature females, which lay eggs, have stiffer valves, up to approximately 19 times the stiffness of the pre-mature locusts. The valves are stiffer in the major working direction, corresponding to soil shuffling and compression, compared with the direction of propagation. Hydration of the valves reduces their stiffness but increases their resilience against failure. These findings provide mechanical and materials guidelines for the design of novel non-drilling burrowing tools, including three-dimensionally printed anisotropic materials based on composites 相似文献