Effect of cell structure on oil absorption of highly oil absorptive polyurethane foam for on-site use

This article reports the effect of cell structure on oil absorption of highly oil-absorptive polyurethane foam (ON-PUR), which is suitable for on-site foaming. We have developed ON-PUR as an oil absorbing polyurethane foam using a very reactive recipe. ON-PUR was synthesized by mixing polyol, water, additives, and polymeric diphenylmethane diisocyanate (P-MDI) using a high-pressure foaming machine. Density, airflow, oil absorption of this foam, and cell structure by microscopy were measured. From these results, it was found that the airflow of this foam increased by crushing, and the oil absorption of this foam increased sharply in a narrow airflow range (from 0.1 to 0.8 scfm). This increase is estimated to be due to the decrease of closed cell structures by crushing treatment. Furthermore, we constituted on-site foaming system in bench scale, which was expected to be applicable to on-site preparation of ON-PUR. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 179–186, 1997     

重离子辐照模拟的实验验证(英文)

采用正电子湮没寿命技术研究了等效剂量的5.28×1016cm-2 85 MeV氟离子和3×1020cm-2En≥1 MeV中子辐照的α-Al2O3中产生的辐射损伤及其细致的热退火行为。实验结果表明重离子辐照的α-Al2O3中的正电子湮没寿命及其强度与中子辐照的α-Al2O3中的完全符合,从实验上验证了重离子辐照可以很好地模拟中子(质子)的辐照。     

A linear-time algorithm for finding a sparsek-connected spanning subgraph of ak-connected graph

We show that anyk-connected graphG = (V, E) has a sparsek-connected spanning subgraphG′ = (V, E′) with ¦E′¦ =O(k¦V¦) by presenting anO(¦E¦)-time algorithm to find one such subgraph, where connectivity stands for either edge-connectivity or node-connectivity. By using this algorithm as preprocessing, the time complexities of some graph problems related to connectivity can be improved. For example, the current best time boundO(max{k ²¦V¦^1/2,k¦V¦}¦E¦) to determine whether node-connectivityK(G) of a graphG = (V, E) is larger than a given integerk or not can be reduced toO(max{k ³¦V¦^3/2,k ²¦V¦²}).     

具有万向机构的蛇形机器人运动控制

设计了一种能够使蛇形机器人运动更灵巧、奇异点更少和运动能力更强的机构．对具有三个自由度的新型蛇形机器人单元进行了改进，在单元上增加被动轮机构，使其具有万向机构的特点。该单元不仅能够用被动轮驱动机器人运动．而且增加了类似于主动轮的驱动机构．克服了被动轮驱动能力弱的缺点，增强了机器人的运动能力。在分析非完整约束的基础上，对蛇形机器人的运动学和冗余度进行分析，提出了控制该类蛇形机器人运动的分解矩阵方法和分组交替运动法。     

单向纤维复合材料的偏轴实验方法开发与评价(英文)

This study presents an integrated method suitable for off-axis tension and compression testing in unidirectional composites,and its application to the testing of in-plane shear characterization.A new rotating-grip test fixture,incorporating the attractive features of the existing pinned-end fixture and hydraulic wedge grips,has been developed.The proposed gripping system consists of two sets of jaw faces,each with a pair of self-aligning bearings that allows for loading in the axial and radial directions.Fi...     

Surface Structure of Converter Slag Stabilized by Heating

Converter slag contains free lime (CaO) and unstable iron oxides (FeO, FeOOH) that may lead to expansive self-destruction. A typical industry practice for converter slag has been stabilization by steam curing and autoclaving; however, the stabilization can only reach the surface, and not the inside, of slag particles. A new method is proposed in this study to stabilize the converter slag by heating at a low temperature. After magnetic separation, specimens of converter slag were subjected to heating for 2 h at a temperature of 500°C, resulting in a decrease of free lime content irrespective of the particle size. This effect was attributed to the formation of Ca₂Fe₉O₁₃ and complicated apatite groups owing to the heating. The iron oxides in the converter slag were analyzed by X-ray photoelectron spectra. It was found that after heating, the unstable FeO (wustite) content decreased and an oxidized α-Fe₂O₃ (hematite) increased. This led to the prevention of the iron-induced expansion. The rate of heat liberation by the free lime in converter slag was smaller than that of the reagent CaO. This suggests that the presumed free lime is in a different form based on the Ca bond energy in the surface of slag particles.     

Translation among CNFs, characteristic models and ordered binary decision diagrams

We consider translation among conjunctive normal forms (CNFs), characteristic models, and ordered binary decision diagrams (OBDDs) of Boolean functions. It is shown in this paper that Horn OBDDs can be translated into their Horn CNFs in polynomial time. As for the opposite direction, the problem can be solved in polynomial time if the ordering of variables in the resulting OBDD is specified as an input. In case that such ordering is not specified and the resulting OBDD must be of minimum size, its decision version becomes NP-complete. Similar results are also obtained for the translation in both directions between characteristic models and OBDDs. We emphasize here that the above results hold on any class of functions having a basis of polynomial size.     

Electro-optical properties of poly(ε-carbobenzosy-l-lysine) in organic solvents

The electric birefringence of poly(ε-carbobenzoxy-l-lysine) (PCBL) in various helicogenic organic solvents and solvent mixtures has been measured over a wide range of field strengths by application of rectangular pulses. The apparent permanent dipole moment and the optical anisotropy factor were separately determined from the field strength dependence of the steady-state birefringence. The apparent dipole moment per residue for a PCBL sample with molecular weight close to 1 × 10⁵ fell in the range of 4.7 to 5.9 D in spite of the large variation of the solvent dielectric constant. The optical anisotropy factor was appreciably small and changed its sign depending upon the solvent. The intrinsic birefringence of PCBL was found to be negative in sign on the basis of the Peterlin-Stuart theory. This was interpreted in terms of the orientation of the side chains with respect to the helical backbone. The apparent dipole moment per residue for high molecular weight PCBL samples was much smaller, indicating a considerable flexibility of the helix.     

High-strain-rate superplasticity in oxide ceramics:a trial of microstructural design based on creep-cavitation mechanisms

From existing knowledge about high-temperature cavitation mechanisms,necessary conditions were discussed for the suppression of cavitation failure during superplastic deformation in ceramic materials.The discussion,where special attention was placed on the relaxation of stress concentrations during grain-boundary sliding and cavity nucleation and growth,leaded to a conclusion that cavitation failure could be retarded by the simultaneous controlling of the initial grain size,the number of residual defects,diffusivity,dynamic grain growth and the homogeneity of microstructure.On the basis of this conclusion,high-strain-rate superplasticity (defined as superplasticity at a strain rate higher than 0.01 s-1) could be intentionally attained in some oxide ceramic materials.This was shown in tetragonal zirconia and composites consisting of zirconia,α-alumina and a spinel phase.     

Cyclic-Oxidation Behavior of Multilayered Pt/Ru-Modified Aluminide Coating

Multilayered Pt/Ru modified aluminide coating for thermal barrier coating(TBC) systems has been investigated.2 μm Pt+2 μm Ru+2 μm Pt was first deposited on nickel-base superalloy DZ125 by electrodeposition,and then the coating was treated by annealing and a conventional pack-cementation aluminizing process.The cyclic oxidation tests were carried out at 1423 K in air.It was found that the thermal cyclic oxidation resistance of Pt/Ru-modified aluminide coating was comparable to that of Pt-modified aluminide coating,which was much better than simply aluminized DZ125.The addition of Ru to Pt-modified aluminide coating increased the resistance to rumpling.The microstructures and phase constitutions of the coating before and after oxidation were investigated.