The second largest Lyapunov exponent and transition to chaos of natural convection in a rectangular cavity

In this study we have proposed an accurate and simple method to evaluate the Lyapunov spectrum. The method is suitable for any discretization method that finally expresses a governing equation system in the form of an ordinary differential equation system. The method was applied to evaluate up to the second largest Lyapunov exponents for natural convection in a rectangular cavity with heated and cooled side walls. The main results are as follows: (1) the largest and second largest Lyapunov exponents can be evaluated without any parameters that affects the exponents. (2) The second largest Lyapunov exponent makes it possible to classify quantitatively thermal convection fields into five regimes against the Rayleigh number and to clarify the transition route from steady state to chaos by identifying the first and second Hopf bifurcations. (3) The fluctuation in thermal convection fields just over the critical Rayleigh number at which Hopf bifurcation occurs can be quantitatively explained by using normalized Lyapunov vectors, associated with the computation of the Lyapunov exponents, just under the critical point.     

Mechanical properties of injection molded Fe-6% Ni-0.4% C steels with varying Mo contents of 0.5 to 2%

In our previous studies, sintered and heat-treated alloy steels (Fe−6Ni−0.5Mo−0.4C (mass%)) produced by a MIM process showed excellent mechanical properties of 2000 MPa tensile strength and 5% elongation. This was attributed to the solid solution strengthening and the mezzo-heterogenous microstruture, which consisted of martensite or retained austenite (Ni and Mo rich phases) surrounded by a network of tempered martensite. This study has been performed to clarify the effect of Mo on the mezzo-heterogeneous microstructure and the mechanical properties of MIM processed and sintered alloy steels (Fe−6Ni−0.4C) with varying Mo content (0.5–2 mass%). The tensile properties of the heat-treated steels with added 2 mass% Mo were lower than those of the steels with added 0.5 mass% Mo. The reduction in the tensile properties, particularly the appearance of large pores formed at the original location of Mo power through the transient liquid phase formation and the low hardness of the matrix, was due to the low sintered density. By using mechanically milled fine Ni and Mo powders, the heat-treated steel (Fe−6Ni−2Mo−0.4C) showed excellent properties, including tensile strength of 1800 MPa and ductility of 2.2% elongation. This article is based on a presentation made in the symposium “The 3rd KIM-JIM Joint Symposium on Advanced Powder Materials”, held at Korea University, Seoul, Korea, October 26–27, 2001 under auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

High Performance Ferrous MIM Components Through Carbon and Microstructural Control

This study on metal injection molding considers the combined influences of the type of powder, subsequent debinding and sintering conditions on the carbon control and microstructure for high performance ferrous materials. Carbon retention and sintered microstructure vary significantly with the powder type. Although carbon retention is sensitive to the debinding and sintering atmospheres and conditions, the carbon content can be successfully controlled by adjusting the weight loss after deb'inding. Mechanical properties are also investigated and compared with that of conventional P/M and wrought materials, some factors affecting the properties are discussed taking the microstructure into account. Finally, high performance properties depend on two types of microstructure, one is the fine homogeneous microstructure in the case of high alloy steels and the other is the fine heterogeneous microstructure in the case of low alloy steels.     

Decomposition of NO on Na+-modified MgO evidenced by ESR and temperature programmed desorption (TPD)

The decomposition of NO to N₂O is accompanied by the formation of O^– over a Na⁺-modified MgO surface at moderated temperatures. The importance of the interaction of (Na⁺) _n (n2) clusters and MgO surface is highlighted.     

Biological activities of the intestinal microflora in mice treated with antibiotics or untreated and the effects of the microflora on absorption and metabolic activation of orally administered glutathione conjugates of K-region epoxides of 1-nitropyrene

We introduce an assay to measure complexed alpha 1-antichymotrypsin in human plasma. The assay works on the principle that the target proteinase cathepsin G has a very high affinity to the surface of microtiter plates, even if these surfaces are blocked with albumin and Tween 20. alpha 1-Antichymotrypsin, when complexed to cathepsin G, is thus immobilized and can be detected with specific antibodies. The mean (SD) concentration of alpha 1-antichymotrypsin in 50 healthy individuals was 1.73 (0.58) nmol/L. The detection limit was 0.84 nmol/L. The results of the assay are linear to at least 14 nmol/L. We propose to use this assay for diseases in which increased turnover of alpha 1-antichymotrypsin or cathepsin G can be expected to clarify further the function of this enzyme-inhibitor system.     

Structure and reactivity of MoO3-MgO catalysts

Surface of OH groups on reduced MoO₂-MgO catalysts such as $$ - - Mg - - O - - \begin{array}{*{20}c} {||} \\ {Mo} \\ | \\ \end{array} - - OH$$ may act as an active site for hydrogenation of propene. The surface hexa-coordinated Mo⁵⁺ ion (MO _6c ⁵⁺ ) was reduced to a lower number of cation such as Mo⁴⁺ or Mo³⁺ which act as an active site for metathesis of propene.     

Effect of SO42− on catalytic activity of Fe2O3 for hydrocracking of coal

The catalytic activity of Fe₂O₃for the hydrocracking of a bituminous coal at 673K increases when a small amount of SO₄^2? is included in the catalyst. The effect of SO₄^2? is marked in the formation of resins, stronger polar compounds and asphaltenes.     

Shape selective catalytic behaviors of nickel ion-exchanged layered potassium niobate

The alcohol decomposition and olefin hydrogenation on the hydrogen-treated Ni ion-exchanged (exchange degree, 30%) potassium niobate (Ni-K₄Nb₆O₁₇) were performed. Formation of propene from i-propanol on Ni-K₄Nb₆O₁₇ was much smaller than that observed on bulk Nb₂O₅, while the olefin yields from ethanol and n-propanol were almost the same on both catalysts. The 1- butene hydrogenation did not proceed on Ni-K₄Nb₆O₁₇, whereas propene hydrogenation took place rapidly on the same catalyst at 80°C.

The formation of the acid sites and Ni metallic sites by hydrogen treatment at 300 °C was proposed by using temperature-programmed reduction (TPR) and extended X-ray absorption fine structure (EXAFS). These results suggest that Hg₂-treated Ni-K₄Nb₆O₁₇ acts as a shape selective acid- and metal-catalyst at suitable reaction temperatures.     

Graph construction with the maximum number of trees by continuous edge addition

A simple computational algorithm is presented to construct a graph with the maximum number of trees by adding edges one by one. The number of trees of a graph would become an index to estimate the overall reliability of probabilistic communication networks with the same link probabilities. Our procedure, Max-trees, selects one edge that gives the maximum number of trees among edges not included in the original graph. This process is continuously repeated at each step of adding an edge, when we get the sequence of new edges to be added. As examples of the execution results, the edge sequence and the maximum number of trees are shown for two types of starting graph, which are a tree of series edges and a star-shaped tree for nodes n = 7 and 8. To see how many trees these graphs have, the minimum numbers of trees for graphs with the same number of nodes and edges are similarly calculated by the minimum-version algorithm Min-trees. An edge sequence of Max-trees makes long cycles, and that of Min-trees makes cycles of three for as long as possible. The ratio of the maximum number of trees to the minimum number of trees is about 1 to 6 for these examples. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

雄胜高温岩体地热开发的数值计算进展

主要介绍日本电力中央研究所为秋田县雄胜高温岩体地热开发试验项目——近年开发的热-水流动藕合数值计算源程序GEOTH3D的原理、特点、应用现状和尚待改善的一些问题，并结合国际上其他相关软件的进展情况，对下一步可能的工作倾向进行了探讨。