基于改进弧长法的层压复合壳后屈曲反应分析

研究了层压复合壳在横向均匀外压作用下的后屈曲反应.应用全拉格朗日公式描述和9结点退化三维壳单元.提出了一种渐进破坏的模式,并且引入改进的弧长法用于非线性有限元分析.重点研究了不同铺设顺序及方向的层压复合壳后屈曲变形形态和破坏过程.数值计算结果的精度和稳定性得以证实.     

REACTION MECHANISM OF PYROPHOSPHATE-DEPENDENT PHOSPHOFRUCTOKINASE FROM PINEAPPLE LEAVES

Data obtained from initial velocity, product inhibition and dead-end inhibition patterns indicate that the pyrophosphate-dependent phosphofructokinase from pineapple leaves has a rapid equilibrium random mechanism with E:F6P:MgPP_i and E:MgPP_i:FBP dead-end complexes. The pH dependence of enzyme-reactant dissociation constants suggests that phosphates of F6P (fructose 6-phosphate), FBP (fructose 1,6-bisphosphate), P_i and PP_i must be completely ionized and the lysine is present in the vicinity of the 1- and 6-phosphates of the sugar phosphate and bisphosphate. The pH dependence of kinetic parameters suggests that the enzyme catalyzes the reaction via general acid-base catalysis with the use of a proton shuttle. The base is required to be unprotonated in both reaction directions.     

Effect of Acylation Upon Extractability of Nitrogen, Phytic Acid and Minerals in Rapeseed Flour Protein Concentrates

Rapeseed flour (RF) and protein concentrates (RPC) were acylated with various levels of succinic or acetic anhydride. Compared with the unmodified control, 63% succinylation or 87% acetylation resulted in up to 45% increase in nitrogen and 95% decrease in phytic acid extractabilities in the first RF extract. At 21% succinylation or 55% acetylation, the extractability of phytic acid was more than double that of the unmodified control whereas the extractability of nitrogen was increased by 22%. A second extraction of the residual acylated RF with deionized water increased the extractability of phytic acid. For both first and second extracts, the extractability pattern of the major minerals followed that of phytic acid. Acylation of heat treated protein concentrate was not effective in increasing the nitrogen and decreasing the phytic acid extractabilities.     

Analytical Phase Diagram Calculation of the System MnO-NiO from Experimental Activity Data

Venezuelan Institute of Scientific Research and School of Metallurgical Engineering and Materials Science, Central University of Venezuela (UCV), Apartado 51717, Caracas 1050-A, Venezuela The complete phase diagram of the binary system MnO-NiO was analytically calculated using the pseudosimpler thermo-dynamic solution model based on the available experimental activity data. The system exhibits a symmetrical subsolidus miscibility gap with its critical temperature at Tc=386.8°C. The possible spinodal curve is also calculated. The solidus and liquidus reveal complete mutual solubilities between the end components at high temperature. The solidus is a continuously sloping monotonic curve but the liquidus is skewed and concave upward near the MnO end. An explanation of the effect of the cationic size differences on the characteristics of phase relations of similar binary systems formed between the NaCl-type divalent monoxides is proposed.     

Chemical Composition and Functional Properties of Acylated Low Phytate Rapeseed Protein Isolate

Protein isolates were prepared by isoelectric precipitation or dialysis of the first and second aqueous extracts of rapeseed flour which was unmodified or acylated by succinic or acetic anhydride. Acylation of the flour lowered the protein and phytic acid contents without significantly altering the amino acid composition of the isoelectrically precipitated protein isolates from the two extracts. The acylated protein isolates from the isoelectrically precipitated extracts had high nitrogen solubility, emulsifying and fat absorption properties. Isoelectrically precipitated and dialyzed acylated proteins did not differ in nitrogen solubility, but dialyzed unmodified protein isolates had nitrogen solubility which was considerably greater than that of isoelectrically precipitated proteins.     

Automatically Determining Semantics for World Wide Web Multimedia Information Retrieval

Search engines are useful because they allow the user to find information of interest from the World Wide Web (WWW). However, most of the popular search engines today are textual; they do not allow the user to find images from the web. For effective retrieval, determining the semantics of the images is essential. In this paper, we describe the problems in determining the semantics of images on the WWW and the approach of AMORE, a WWW search engine that we have developed. AMORE's techniques can be extended to other media like audio and video. We explain how we assign keywords to the images based on HTML pages and the method to determine similar images based on the assigned text. We also discuss some statistics showing the effectiveness of our technique. Finally, we present the visual interface of AMORE with the help of several retrieval scenarios.     

Electrical Properties of Sputter-deposited ZrO2-based Pt/ZrO2/Si Capacitors

Pt/ZrO2/Si sandwich structures where ZrO2 is deposited by radio frequency （r.f.） magnetron sputtering using a Zr target in an atmosphere of O2/Ar gas mixture, were fabricated and the effects of the O2/Ar flow ratio in the reactive sputtering process, the annealing temperature, the ZrO2 film thickness on the structure, the surface roughness of ZrO2 films and the electric properties of Pt/ZrO2/Si metal-oxide-semiconductor （MOS） capacitors were investigated. The optimum process parameters of the Pt/ZrO2/Si capacitor based on reactively sputtered-ZrO2 determined in such a way as the capacitance is maximized and the leakage current, the oxide charge, and the interface trap density are minimized that is the O2/Ar flow ratio of 1.5, the annealing temperature of 800℃, and the film thickness of 10 nm. Also the conduction mechanism in the Pt/ZrO2/Si capacitor has been discussed.