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1.
M. Kangas J. Villegas N. Kumar T. Salmi D.Yu. Murzin F. Sandelin E. Harlin 《Catalysis Today》2005,100(3-4):363-366
An investigation of the effect of reaction conditions on product distribution in the skeletal isomerisation reaction of linear butenes has been carried out. The main reaction routes over ferrierite have been identified. Beside the main product isobutene, major by-product formation occurs. The unwanted reactions include dimerisation of butene to form octenes, hydrogen transfer yielding small amounts of saturated C3 and C4 hydrocarbons and disproportionation producing propene and pentenes. The most abundant by-products were pentene and propene, though these were not formed in equimolar amounts as could be expected. Oligomerisation experiments of propene over ferrierite produced large amounts of butene and pentene, revealing the presence of adsorbed nonene. The cracking of this surface species to hexene and propene is the most likely reaction route for the excess propene formation. This additional path to propene formation operates mainly at temperatures above 623 K. 相似文献
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Differential emotions theory (DET) proposes that infant facial expressions of emotions are differentiated. To test this hypothesis, the authors examined infant facial expressions longitudinally at 2, 4, and 6 mo of age during face-to-face play and a "still-face" interaction with their mothers. Infant expressions were coded using the Maximally Discriminative Facial Movement Coding System (Max). Consistent with DET, discrete positive expressions occurred more of the time and were of longer duration than blended expressions of positive affect. Contrary to DET, at no age did the proportions or durations of discrete and blended negative expressions differ, and they showed different patterns of developmental change. One is led to either reject or revise DET or else question the adequacy of the Max system. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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Given an array ofn input numbers, therange-maxima problem is that of preprocessing the data so that queries of the type what is the maximum value in subarray [i..j] can be answered quickly using one processor. We present a randomized preprocessing algorithm that runs inO(log*
n) time with high probability, using an optimal number of processors on a CRCW PRAM; each query can be processed in constant time by one processor. We also present a randomized algorithm for a parallel comparison model. Using an optimal number of processors, the preprocessing algorithm runs inO( (n)) time with high probability; each query can be processed inO ( (n)) time by one processor. (As is standard, (n) is the inverse of Ackermann function.) A constant time query can be achieved by some slowdown in the performance of the preprocessing stage. 相似文献
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We show how to support efficient back traversal in a unidirectional list, using small memory and with essentially no slowdown in forward steps. Using O(lgn) memory for a list of size n, the i’th back-step from the farthest point reached so far takes O(lgi) time in the worst case, while the overhead per forward step is at most ? for arbitrary small constant ?>0. An arbitrary sequence of forward and back steps is allowed. A full trade-off between memory usage and time per back-step is presented: k vs. kn1/k and vice versa. Our algorithms are based on a novel pebbling technique which moves pebbles on a virtual binary, or n1/k-ary, tree that can only be traversed in a pre-order fashion. 相似文献
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Xiaoyi Wang Scott Kangas Divyachapan Padur Lei Liu James A. Swanson Arthur J. Helmicki Victor J. Hunt 《Canadian Metallurgical Quarterly》2005,10(4):460-467
Condition assessment is a term that is used to describe the process of characterizing the physical condition of constructed systems. This paper summarizes a condition assessment (CA) procedure based on a complete system of field-testing, finite element (FE) modeling, and load rating. Experimental techniques, including both modal testing and truckload testing, are used to collect measurements of the constructed systems. The basic mechanism and procedure of the FE modeling and calibration are presented. Different physical parameters of FE models are adjusted during the calibration process using both static and dynamic responses as criteria to achieve convergence between experimental measurements and analytical results using carefully developed objective functions. Finally, a bridge load rating is completed on the basis of the calibrated model. These developments are described and illustrated using a representative bridge as an example. 相似文献
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Del Villar I. Matias I.R. Arregui F.J. Claus R.O. 《Nanotechnology, IEEE Transactions on》2005,4(2):187-193
A fiber-optic sensor sensitive to hydrogen peroxide has been designed based on the electrostatic layer-by-layer self-assembly method. Prussian blue has been deposited in a polymeric structure formed by Poly(allylamine hydrochloride) and poly(acrylic acid). The concentration that can be detected range between 10/sup -6/-10/sup -3/ M, and recovery of the sensor after immersion into a reductive agent was demonstrated. The response of the sensor is independent of the pH for values that range between 4-7.4. Some rules for estimation of the refractive index of the material deposited and the thickness of the bilayers are also presented. 相似文献