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21.
The polymorphism of Ca3SiO5 has been studied microscopically by following changes in optic properties and modes of twinning of the crystal as a function of temperature. Besides the six modifications already established, a hitherto-unidentified monoclinic phase M3, which can be characterized only by microscopy at present, has been found to exist just below the rhombohedral phase (R). The transitions that give clear thermal effects on the DTA curve show no corresponding change under the microscope. 相似文献
22.
Pavel Krömer Jan Platoš Václav Snášel 《International journal of parallel programming》2014,42(5):681-709
Graphic processing units (GPUs) emerged recently as an exciting new hardware environment for a truly parallel implementation and execution of Nature and Bio-inspired Algorithms with excellent price-to-power ratio. In contrast to common multicore CPUs that contain up to tens of independent cores, the GPUs represent a massively parallel single-instruction multiple-data devices that can nowadays reach peak performance of hundreds and thousands of giga floating-point operations per second. Nature and Bio-inspired Algorithms implement parallel optimization strategies in which a single candidate solution, a group of candidate solutions (population), or multiple populations seek for optimal solution or set of solutions of given problem. Genetic algorithms (GA) constitute a family of traditional and very well-known nature-inspired populational meta-heuristic algorithms that have proved its usefulness on a plethora of tasks through the years. Differential evolution (DE) is another efficient populational meta-heuristic algorithm for real-parameter optimization. Particle swarm optimization (PSO) can be seen as nature-inspired multiagent method in which the interaction of simple independent agents yields intelligent collective behavior. Simulated annealing (SA) is global optimization algorithm which combines statistical mechanics and combinatorial optimization with inspiration in metallurgy. This survey provides a brief overview of the latest state-of-the-art research on the design, implementation, and applications of parallel GA, DE, PSO, and SA-based methods on the GPUs. 相似文献
23.
The capacity of the electric double layer at the interfaces Hg/molten NaAlCl4 and Pt/molten NaAlCl4 was determined and the influence of the surface-active substances tetramethylammonium chloride and urea was investigated. The dependence of the capacity on the electrode potential was found to agree with a model proposed by Parsons. 相似文献
24.
Zdena Tvarůžková Magda Tupá Pavel Jírů Alfonso Nastro Giorgio Giordano Ferruccio Trifiró 《Catalysis Letters》1989,2(6):369-374
The small pore zeolite HLZ 132 exhibits, in comparison with other zeolites, an increased selectivity for the transformation of methanol to ethylene in the reaction temperature range 350–500 °C: the weight ratio of C2H4 to C3H6 in the products ranges between 1 and 4 at WHSV=2 h–1. Besides the effect of the reactant shape selectivity this fact may be interpreted by the participation of the asymmetrical methoxy groups in the surface as well as by proton-donor centres of lower acidity which do not catalyze the oligomerization of ethylene but which do the more basic molecule of propylene, thereby generating polyene-type coke. 相似文献
25.
Summary The dynamic mechanical behaviour of 4% aqueous solutions and networks of poly (N, N-diethylacrylamide) and copolymers of diethylacrylamide
with sodium methacrylate (MNa) (molar ratio xMNA=0–0.05) swollen in water was measured in the temperature range 20–80 °C. With increasing temperature, at Tc polymer chains collapse from random coil to more compact globular conformations. While in the region of coil conformations
(T > Tc) the mechanical behaviour of solutions has a liquid-like character (the loss modulus G″ is higher than the storage modulus
G′ for a constant frequency ω=1 Hz), in the region of globular conformations (T > Tc) a heterogeneous physical network is built in solutions, and the mechanical behaviour has a solid-like character (G′ > G″).
In networks the collapse is reflected in an increase of storage modulus G′; the magnitude of this increase decreases with
ionization. The dependence of the loss modulus G″ on the temperature of solutions and networks allows us to conclude that
the magnitude of losses in the collapsed state is affected rather by xMNa (the modulus G″ increases with increasing ionization) than by the heterogeneous structure of the samples. 相似文献
26.
Ccile Donze Pavel Korovchenko Pierre Gallezot Michle Besson 《Applied catalysis. B, Environmental》2007,70(1-4):621-629
The synthesis of substituted benzaldehydes, benzoic acids, heterocyclic aromatic aldehydes and acids has been studied via the oxidation of the aromatic alcohols with air under mild pressure (<20 bar) at 100 °C, in the presence of a 1.95 wt.% Pt/C catalyst. The solvent was found to play the most important role in determining the selectivity of the oxidation products. Changing the solvent enabled tuning the reaction either to the aldehyde (pure dioxane), or the carboxylic acid (dioxane/aqueous solution without or with addition of sodium hydroxide). This oxidation method allowed to effectively oxidize many substituted benzylalcohols with various electron-releasing or -attracting groups (NO2, Me, OMe, Cl, Br, OH, phenyl, …) and heterocyclic alcohols including nitrogen and sulphur atoms (2-thiophenemethanol, 2- and 4-pyridine methanol compounds). 相似文献
27.
Miloslav Bohdanecký 《Polymer Bulletin》1993,31(1):117-122
Summary Critical values of the polymer volume fraction 2,c and the interaction parameter c have been computed for the case that the equation for the chemical potential of solvent contains terms c
2
3
and c
2
4
in addition to
2
2
. For 0 c 1/3, the limits for infinite chain length are
2,c
= 0 and
c
= 0.5. Quite different results are obtained for c > 1/3,
2,c
being finite and
c
lower than 1/2. Conclusions for the estimation of the temperature and the entropy-of-dilution parameter are discussed. 相似文献
28.
John Case Sanjay Jain Yuh Shin Ong Pavel Semukhin Frank Stephan 《Journal of Computer and System Sciences》2014
Automatic classes are classes of languages for which a finite automaton can decide whether a given element is in a set given by its index. The present work studies the learnability of automatic families by automatic learners which, in each round, output a hypothesis and update a long-term memory, depending on the input datum, via an automatic function. Many variants of automatic learners are investigated: where the long-term memory is restricted to be the current hypothesis whenever this exists, cannot be of length larger than the length of the longest datum seen, or has to consist of a constant number of examples seen so far. Learnability is also studied with respect to queries which reveal information about past data or past computation history; the number of queries per round is bounded by a constant. 相似文献
29.
Pavel Martyugin 《Theory of Computing Systems》2014,54(2):293-304
We show that the problem of checking careful synchronizability of partial finite automata is PSPACE-complete. Also the problems of checking D 1-, D 2-, and D 3-directability of nondeterministic finite automata are PSPACE-complete; moreover, the restrictions of all these problems to automata with two input letters remain PSPACE-complete. 相似文献
30.
Organic compounds dissolved in water can be decomposed on a layer of n-TiO2 particles irradiated by u.v. light, which generates holes and electrons in the TiO2 material. Dissolved oxygen was used as electron scavenger and holes reacted with water to give OH radicals. The rate of degradation of the dissolved organic compounds by OH radicals is limited by the transfer of either oxygen or of theorganic compounds to the surface of n-TiO2 particles. The consequence of these limits is that, in the batch mode reactor with recirculation of the liquid, the dependence of the concentration of an organic compound on time has either a linear or an exponential form. Experiments with decomposition of oxalic acid in aqueous solutions using a plate reactor (60 cm × 120 cm) confirmed the analysis. Equations for evaluation of the mass transfer coefficient of the dissolved species to the surface of the plate reactor with a moving liquid fil m were developed for the case of the thickness of the Nernst diffusion layer being thinner than the thickness of the liquid. The experimentally obtained decomposition rate of oxalic acid was about 60 to 80% of the theoretical decomposition rate limited by oxygen flux through the film of a moving liquid. The present theory neglects the diffusion of oxygen into the porous layer of n-TiO2. 相似文献