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排序方式: 共有184条查询结果,搜索用时 78 毫秒
51.
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
52.
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
53.
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
54.
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
55.
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
56.
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
57.
58.
How to Implement a Safe Real-Time System:The OBSERV Implementation of the Production Cell Case Study
The Production Cell example was chosen by FZI (the Computer Science Research Center), in Karlsruhe. to examine the benefits of formal methods for industrial applications. This example was implemented in more than 30 formalisms. This paper describes the implementation of the Production Cell in OBSERV. The OBSERV methodology for software development is based on rapid construction of an executable specification, or prototype, of a system, which may be examined and modified repeatedly to achieve the desired functionality. The objectives of OBSERV also include facilitating a smooth transition to a target system, and providing means for reusing specification, design, and code of systems, particularly real-time reactive systems. In this paper we show how the methods used in the OBSERV implementation address the requirements imposed by reactive systems. We describe the OBSERV implementation of the Production cell, explain design decisions, with special emphasis on reusability and safety issues. We demonstrate how to take care of safety and liveness properties required for this example. These properties are checked by means of simulation and formally proved with a model checker. 相似文献
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.
Universal compression algorithms can detect recurring patterns in any type of temporal data—including financial data—for the
purpose of compression. The universal algorithms actually find a model of the data that can be used for either compression
or prediction. We present a universal Variable Order Markov (VOM) model and use it to test the weak form of the Efficient
Market Hypothesis (EMH). The EMH is tested for 12 pairs of international intra-day currency exchange rates for one year series
of 1, 5, 10, 15, 20, 25 and 30 min. Statistically significant compression is detected in all the time-series and the high
frequency series are also predictable above random. However, the predictability of the model is not sufficient to generate
a profitable trading strategy, thus, Forex market turns out to be efficient, at least most of the time.
相似文献