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81.
The flow points of atactic poly(vinyl alcohol) (a-PVA) gels with H2O/dimethyl sulfoxide (DMSO) = 90/10 (v/v) chilled at 20 to ?78°C for 24 h depended on the chilling temperature and were 0–30°C for gels with the initial polymer concentrations (Ci) of 2–5 g/dL, whereas those for H2O/DMSO = 50/50 chilled at 0 to ?78°C were independent of the chilling temperature and were 70–75°C. Syneresis occurred after eight cycles of freezing (?24°C) and thawing (20°C) for a-PVA hydrogels at concentrations above Ci = 4 g/dL and two such cycles for syndiotacticity-rich PVA (s-PVA) hydrogels at concentrations above Ci = 1 g/dL. The extent of syneresis per one cycle for s-PVA hydrogels was higher than that for a-PVA hydrogels at the initial cycles. In the a-PVA hydrogels with an initial polymer concentration of ca. 30 g/dL, syneresis was expected not to occur even after 20 cycles. If all the free water in the gels is assumed to have transuded by syneresis after 20 cycles, the residual water is bound water and is estimated to be six water molecules per one vinyl alcohol monomer unit. © 1994 John Wiley & Sons, Inc. 相似文献
82.
It has been reported that the major cause of earthquake damage to embankments on level ground surfaces is liquefaction of foundation soil. A few case histories, however, suggest that river levees resting on non-liquefiable foundation soil have been severely damaged if the foundation soil is highly compressible, such as thick soft clay and peat deposits. A large number of such river levees were severely damaged by the 2011 off the Pacific coast of Tohoku earthquake. A detailed inspection of the dissected damaged levees revealed that the base of the levees subsided in a bowl shape due to foundation consolidation. The liquefaction of a saturated zone, formed at the embankment base, is considered the prime cause of the damage. The deformation of the levees, due to the foundation consolidation which may have resulted in a reduction in stress and the degradation of soil density, is surmised to have contributed as an underlying mechanism. In this study, a series of centrifuge tests is conducted to experimentally verify the effects of the thickness of the saturated zone in embankments and of the foundation consolidation on the seismic damage to embankments. It is found that the thickness of the saturated zone in embankments and the drainage boundary conditions of the zone have a significant effect on the deformation of the embankments during shaking. For an embankment on a soft clay deposit, horizontal tensile strain as high as 6% was observed at the zone above the embankment base and horizontal stress was approximately half that of the embankment on stiff foundation soil. Crest settlement and the deformation of the embankment during shaking were larger for the embankment subjected to deformation due to foundation consolidation. 相似文献
83.
Kyosuke Yoshimi Shuji Hanada 《JOM Journal of the Minerals, Metals and Materials Society》1997,49(8):46-49
For the development of Fe−Al alloys as structural materials, a deep understanding of slip and deformation properties is necessary.
In particular, since mechanical properties of the iron aluminides are affected by excess vacancy strengthening as well as
the positive-temperature dependence of yield stress, controlling these strength features is essential. In this article, the
strength properties of iron aluminides are reviewed.
Author’s Note: All compositions are provided in mole percent.
Kyosuke Yoshimi earned his Ph.D. in materials science and engineering at Tohoku University in 1997. He is currently a research associate
at Tohoku University.
Shuji Hanada earned his Ph.D. in materials science and engineering at Tohoku University. He is currently a professor at Tohoku University.
Dr. Hanada is also a member of TMS. 相似文献
84.
Shuji Fukahori Hideaki Ichiura Takuya Kitaoka Hiroo Tanaka Hiroyuki Wariishi 《Journal of Materials Science》2007,42(15):6087-6092
Titanium dioxide (TiO2) powder-containing sheet composites, called TiO2 sheet, were prepared by a papermaking technique, and their photocatalytic efficiency was investigated. The TiO2 powders were homogeneously scattered over the fiber-mix networks tailored within the catalyst sheet. Under UV irradiation,
the TiO2 paper could decompose p-hydroxyacetophenone (p-HAP), although the degradation efficiency by the TiO2 sheet was lower than that by the TiO2 powder. Scanning electron microscopy revealed that coverage of the TiO2 particles inside the sheet by alumina binder which was used to improve the sheet strength caused the deterioration of the
photocatalytic performance. Internal addition of alumina binder made the TiO2 sheet porous and such a TiO2 sheet exhibited high photocatalytic performance equivalent to that of TiO2 powder. The porous structure of TiO2 sheet might contribute to effective transport of p-HAP to the surface of TiO2 particles inside the sheet, resulting in high degradation performance. In addition, TiO2 sheet prepared using TiO2 sol showed higher photocatalytic efficiency than TiO2 powder and it was indicated that the porous sheet structure might provide suitable conditions for TiO2 catalysis for photodecomposition. 相似文献
85.
Naoya Masahashi Yoshiteru Mizukoshi Satoshi Semboshi Kazuyo Ohmura Shuji Hanada 《Thin solid films》2012,520(15):4956-4964
Photocatalytic activity and wettability of the anodic oxide layer on Ti6Al4V prepared by anodization in a sulfuric acid electrolyte are explored. The oxide is composed mainly of TiO2 with V2O5, VO2 and Al2O3. The crystal structure of the TiO2 varies from anatase to rutile with the sulfuric acid concentration in the electrolyte. Anatase exhibits better photocatalytic activity compared with rutile, which is different from those on Ti and Ti-Nb-Sn alloy. Contact angles of the oxides decrease with ultraviolet light illumination, and hydrophilicity is observed in the rutile oxide. Both photocatalytic activity and hydrophilicity are inferior to the corresponding Ti and Ti-Nb-Sn alloy, which is explained by the presence of Al2O3 in the anodic oxide. 相似文献
86.
Yoshimoto S Murata Y Kubo K Tomita K Motoyoshi K Kimura T Okino H Hobara R Matsuda I Honda S Katayama M Hasegawa S 《Nano letters》2007,7(4):956-959
We performed four-terminal conductivity measurements on a CoSi2 nanowire (NW) at room temperature by using PtIr-coated carbon nanotube (CNT) tips in a four-tip scanning tunneling microscope. The physical stability and high aspect ratio of the CNT tips made it possible to reduce the probe spacing down to ca. 30 nm. The probe-spacing dependence of resistance showed diffusive transport even at 30 nm and no current leakage to the Si substrate. 相似文献
87.
合成了一种新颖的乙炔衍生物,2-甲基-8-(9,9-二丁基芴)-3,5,7-三炔-2-辛醇(6a),并利用红外光谱(IR),紫外光谱(Uv),核磁(NMR),质谱(MS)等对其结构进行了表征。利用红外光谱(IR)和紫外光谱(Uv)对其拓扑固相聚合性质进行了研究。实验结果表明,这些化合物在加热和紫外光照射条件下都能够发生固相聚合,但得到的是结构复杂的聚合物。 相似文献
88.
为了不使用任何还原剂而获得聚合物固载高分散零价双金属加氢催化剂,利用金属蒸气法制备了3种不同Pd/Cu质量比的聚合物固载双金属原子簇。透射电镜(TEM)和X衍射(XRD)测定表明,Pd-Cu原子簇粒度很小,平均直径小于3.0nm。X射线光电子能谱(XPS)表明,Pd和Cu均为零价态。Pd-Cu原子簇在异丙叉加氢反应中具有很高的活性和选择性。这些结果提供了令人信服的证据,即金属蒸气法可用于在聚合物孔穴内直接而温和地置入小的零价金属原子簇,而且这样制备的聚合物固载金属原子簇很适合于催化应用。 相似文献
89.
Masahiro Kaneko Kazuhiko Ishihara Shuji Nakanishi 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(34)
Microbial electrochemical systems in which metabolic electrons in living microbes have been extracted to or injected from an extracellular electrical circuit have attracted considerable attention as environmentally‐friendly energy conversion systems. Since general microbes cannot exchange electrons with extracellular solids, electron mediators are needed to connect living cells to an extracellular electrode. Although hydrophobic small molecules that can penetrate cell membranes are commonly used as electron mediators, they cannot be dissolved at high concentrations in aqueous media. The use of hydrophobic mediators in combination with small hydrophilic redox molecules can substantially increase the efficiency of the extracellular electron transfer process, but this method has side effects, in some cases, such as cytotoxicity and environmental pollution. In this Review, recently‐developed redox‐active polymers are highlighted as a new type of electron mediator that has less cytotoxicity than many conventional electron mediators. Owing to the design flexibility of polymer structures, important parameters that affect electron transport properties, such as redox potential, the balance of hydrophobicity and hydrophilicity, and electron conductivity, can be systematically regulated. 相似文献
90.
采用OM和SEM分析方法研究了帘线钢空气气氛下连续氧化行为以及高线精轧、吐丝温度对热轧盘条表面氧化铁皮厚度和相组成的影响,同时采用热模拟方法分析了FeO层发生先共析、共析转变生成Fe3O4的条件.实验结果表明,945℃是帘线钢快速氧化起点温度,随着温度升高,氧化速率急剧增加;而当温度降低到700℃时,氧化过程极其缓慢.控制700~945℃范围内的冷速是控制氧化铁皮厚度及相组成的关键工艺.高线生产控制精轧和吐丝温度在900~940℃,氧化铁皮厚度7~20μm,FeO质量分数为65%~80%,具有最佳除鳞性能.热模拟分析表明,400~500℃是FeO层发生共析转变的"鼻尖"温度,孕育期最短.提高400~500℃区间冷速可抑制FeO层发生共析转变,使机械除鳞率提高3%左右. 相似文献