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排序方式: 共有3449条查询结果,搜索用时 43 毫秒
41.
Andrey V. Kikhtenko Vladimir B. Goncharov Kirill I. Zamaraev 《Catalysis Letters》1993,21(3-4):353-360
Gas phase reactions of Mo+ and W+ ions with the molecules of various oxidants (NO, O2, N2O, CH2O, C2H4O) were studied using ion cyclotron resonance. In oxidation with N2O the mono-, di- and trioxide metal cations are formed consecutively. The trioxide MO3
+ ions of both metals react with CO to form CO2 and MO2
+ ions. In this way, catalytic reaction N2O + CO N2 + CO2 occurs in the gas phase with MoO3
+ /MoO2
+ and WO3
+/WO2
+ couples as catalysts. The rate constants have been measured for both stages of the catalytic cycle as well as for the stages of the catalyst preparation. Metal-oxygen bond energies were estimated for MoOx
+ and WOx
+ species with various x. The mechanism of CO oxidation with MoOx
+ and WOx
+ cations as catalysts in the gas phase is discussed in comparison with that for the oxidation over classical solid oxide catalysts. 相似文献
42.
The concept of games with incompetence has been introduced to better represent games where players may not be capable of executing strategies that they select. In particular this paper introduces incompetence into bimatrix games and investigates the properties of such games. The results obtained describe both the general dependence of “extreme Nash equilibrium payoffs” on incompetence and special behaviour arising in particular cases. The dependence of the payoffs can be complex and include non-linearities and transition points. Transition points occur when kernels change and may result in the number of “extreme Nash equilibria” changing. Understanding these changes allows the determination of the benefits of regimes that seek to decrease a player’s incompetence. While the games we consider are normally static, in our context there is a hidden dynamics resulting from the fact that players will strive to improve their equilibrium payoffs by changing their incompetence levels. This might require training, in the case of games like tennis, or it might require the purchase of new equipment costing billions of dollars, in the case of military applications. 相似文献
43.
Igor Goldfarb Vladimir Gol’dshtein J. Barry. Greenberg Ann Zinoviev 《Journal of Engineering Mathematics》2006,56(2):129-142
Recent experimental evidence has uncovered the peculiar behavior of certain gel droplets which, under appropriate ambient
thermal conditions, evaporate and burn in an oscillatory fashion. In this work a preliminary foray is made into the theoretical
analysis of the nature of the evolution of a hot gas mixture containing organic gel fuel droplets with oscillatory evaporation
within the context of thermal-explosion theory. The problem is modeled as a system of highly nonlinear singularly perturbed
ordinary differential equations. Non-dimensionalization of the equations enables identification of the parameters that play
a major role in determining the dynamical regimes of the system of equations. The method of integral manifolds is exploited
for the analysis and it is found, that for certain parametric regions, the system exhibits new dynamical behavior that is
quite different from that found for conventional liquid droplets. 相似文献
44.
A new meshless method for computing the dynamic stress intensity factors (SIFs) in continuously non-homogeneous solids under a transient dynamic load is presented. The method is based on the local boundary integral equation (LBIE) formulation and the moving least squares (MLS) approximation. The analyzed domain is divided into small subdomains, in which a weak solution is assumed to exist. Nodal points are randomly spread in the analyzed domain and each one is surrounded by a circle centered at the collocation point. The boundary-domain integral formulation with elastostatic fundamental solutions for homogeneous solids in Laplace-transformed domain is used to obtain the weak solution for subdomains. On the boundary of the subdomains, both the displacement and the traction vectors are unknown generally. If modified elastostatic fundamental solutions vanishing on the boundary of the subdomain are employed, the traction vector is eliminated from the local boundary integral equations for all interior nodal points. The spatial variation of the displacements is approximated by the MLS scheme. 相似文献
45.
46.
47.
Velocity Distribution in the Roughness Layer of Rough-Bed Flows 总被引:1,自引:0,他引:1
Vladimir Nikora Katinka Koll Ian McEwan Stephen McLean Andreas Dittrich 《Canadian Metallurgical Quarterly》2004,130(10):1036-1042
Several models for the vertical distribution of the double-averaged (in time and in the plane parallel to the mean bed) longitudinal velocity in the flow region between roughness troughs and roughness tops are suggested. We found that the same model for velocity distribution may be applicable to a range of flow conditions and roughness types, which share some common features. The suggested models for velocity distribution in the near-bed region are: (1) Constant velocity; (2) exponential velocity distribution; and (3) linear velocity distribution. The measured velocity distributions may be approximated by a single model or by a combination of models depending on roughness geometry and flow conditions. The validity of these models for velocity distribution is supported by laboratory data. 相似文献
48.
Laszlo Szathmary Petko Valtchev Amedeo Napoli Robert Godin Alix Boc Vladimir Makarenkov 《Annals of Mathematics and Artificial Intelligence》2014,70(1-2):81-105
In pattern mining and association rule mining, there is a variety of algorithms for mining frequent closed itemsets (FCIs) and frequent generators (FGs), whereas a smaller part further involves the precedence relation between FCIs. The interplay of these three constructs and their joint computation have been studied within the formal concept analysis (FCA) field yet none of the proposed algorithms is scalable. In frequent pattern mining, at least one suite of efficient algorithms has been designed that exploits basically the same ideas and follows the same overall computational schema. Based on an in-depth analysis of the aforementioned interplay that is rooted in a fundamental duality from hypergraph theory, we propose a new schema that should enable for a more parsimonious computation. We exemplify the new schema in the design of Snow-Touch, a concrete FCI/FG/precedence miner that reuses an existing algorithm, Charm, for mining FCIs, and completes it with two original methods for mining FGs and precedence, respectively. The performance of Snow-Touch and of its closest competitor, Charm-L, were experimentally compared using a large variety of datasets. The outcome of the experimental study suggests that our method outperforms Charm-L on dense data while on sparse one the trend is reversed. Furthermore, we demonstrate the usefulness of our method and the new schema through an application to the analysis of a genome dataset. The initial results reported here confirm the capacity of the method to focus on significant associations. 相似文献
49.
Olga Porembskaya Vsevolod Zinserling Vladimir Tomson Yana Toropova Eleonora A. Starikova Vitaliy V. Maslei Nika I. Bulavinova Olga V. Kirik Marina A. Syrtsova Leonid Laberko Maxim I. Galchenko Vyacheslav Kravchuk Sergey Saiganov Alexander Brill 《International journal of molecular sciences》2022,23(10)
Pulmonary embolism is a life-threatening condition, which can result in respiratory insufficiency and death. Blood clots occluding branches of the pulmonary artery (PA) are traditionally considered to originate from thrombi in deep veins (usually in legs). However, growing evidence suggests that occlusion of the vessels in the lungs can develop without preceding deep vein thrombosis (DVT). In this work, we used an inferior vena cava (IVC) complete ligation model of DVT in Wistar rats to explore the possibility and mechanisms of PA thrombosis under the conditions where all routes of thrombotic mass migration from peripheral veins are blocked. We demonstrate that rats both with normal and reduced neutrophil counts developed thrombi in the IVC, although, neutropenia caused a substantial decrease in thrombus size and a shift from fresh fibrin toward mature fibrin and connective tissue inside the thrombus. Massive fibrin deposition was found in the PA branches in the majority of DVT rats with normal neutrophil counts, but in none of the neutropenic animals. Neutrophil ablation also abolished macroscopic signs of lung damage. Altogether, the results demonstrate that thrombi in the lung vasculature can form in situ by mechanisms that require local neutrophil recruitment taking place in the DVT setting. 相似文献
50.