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排序方式: 共有903条查询结果,搜索用时 15 毫秒
31.
The goal of our study is to develop a system for walking on a step using a wearable robot. Our system consists of (1) sensing of a step from the movement of the walker, (2) detection of the foot placement state related to the step, and (3) generation of gait patterns of climbing and stepping down for the step. In the generation of gait patterns for the step, toe trajectories are generated according to the height of the step to avoid collision of the swinging leg with the step. The hip trajectory is generated by an optimization technique that minimizes the sum of the joint angular jerk of the robot subject to constraints on the hip position and the velocity at toe liftoff. Each joint angle trajectory is calculated from the generated trajectories by means of inverse kinematic equations. We investigated the feasibility of the proposed sensor and control systems for two steps with different heights. 相似文献
32.
Takahiro Matsumoto Tetsuro Nose Yasuaki Nagata Katsuhiro Kawashima Tastuya Yamada Hidetoshi Nakano Satoshi Nagai 《Journal of the American Ceramic Society》2001,84(7):1521-1525
Young's modulus and Poisson's ratio of SiC ceramics at temperatures >1400°C were obtained using a laser ultrasonics method that included a Fabry-Pérot interferometer (LUFP). At temperatures <1000°C, Young's modulus and Poisson's ratio measured using the LUFP method agreed well with those measured using standard contact methods, such as the resonance method and the ultrasonic pulse method. These results showed that the LUFP method is a powerful tool for measuring high-temperature elastic properties of advanced ceramics in a noncontact manner. 相似文献
33.
Nino Rinaldi Usman Khalida Al-Dalama Takeshi Kubota Yasuaki Okamoto 《Applied Catalysis A: General》2009,360(2):130-136
The effect of citric acid (CA) addition was studied on the HDS of thiophene over Co–Mo/(B)/Al2O3 catalysts. The catalysts were characterized by means of LRS, Mo K-edge EXAFS, NO adsorption capacity measurements, and UV–vis spectra. The catalysts were subjected to a chemical vapor deposition (CVD) technique using Co(CO)3NO as a precursor of Co in order to get deeper insights into the effect of citric acid addition. It was shown that the HDS activity was enhanced by the citric acid addition up to the CA/Mo mole ratio of around 1 and leveled off with further addition. The amount of Co anchored by the CVD was increased by the addition of citric acid, suggesting an increase in the dispersion of MoS2 particles on the catalyst by the simultaneous presence of Co, Mo and citric acid, in conformity with the increase in the NO adsorption capacity. In contrast to Co–Mo catalysts, the edge dispersion of MoS2 particles in Mo/B/Al2O3 was not affected by the addition of citric acid. The LRS, UV–vis spectra and Mo K-edge EXAFS showed that Co–CA and Mo–CA surface complexes are formed by the addition of citric acid. The Co–CA surface complex is more preferentially formed on CoMo/Al than on CoMo/B/Al, in agreement with a greater promoting effect of citric acid at a lower CA/Mo mole ratio for CoMo/Al than for CoMo/B/Al. 相似文献
34.
统一强度理论的发展及其在土木水利等工程中的应用和经济意义 总被引:10,自引:5,他引:10
统一强度理论是在中国本土原创产生和发展起来的关于材料强度和结构强度的系统新理论。它从连续统力学最基本的单元体力学模型开始,到数学建模方法,理论公式的表述,以及一系列新的理论公式都不同于以往的各种理论。它将以往各种适合于某一类材料的单一强度理论推进为可以适合于多种材料的统一强度理论。经过40多年的发展,它不仅自己形成了系统的理论,而且将很多著名的理论包容其中,形成了范围更宽广、功能更强大的理论体系。由于它具有一个统一的力学模型,清晰的物理意义,简单的线性数学表述式,能反映材料的基本特性,即sD效应(不同的抗拉强度和抗压强度)、静水应力效应、正应力效应、中间主应力效应和中间主剪应力效应,以及结构强度分析的破坏准则效应,并且与现有的实验数据相吻合,能容易地适合许多新情况;此外,统一强度理论既容易用来取得解析解,也容易用于计算机程序取得数值解。统一强度理论已被推广应用于很多领域。在连续介质和工程应用的框架下对统一强度理论的发展及其在土木工程中的应用和经济意义进行较为系统的小结。 相似文献
35.
R.W. Callis J.L. Doane H.J. Grunloh K. Kajiwara A. Kasugai C.P. Moeller Y. Oda R.A. Olstad K. Sakamoto K. Takahashi 《Fusion Engineering and Design》2009,84(2-6):526-529
Initial testing on the Japan Atomic Energy Agency Gyrotron Test Stand of ITER-relevant TL components, has shown reasonable efficiencies, but identified that trapped modes between closely located miter bends, as well as mode conversion at miter bends can lead to excessive heating of the connecting waveguides. General Atomics has designed, built, and will test components to address this issue as well as ITER relevant components that have not been tested at the levels of 1 MW, 170 GHz, for extended pulse lengths. Some of the components that will be tested are ultra low loss miter bends, dc breaks, polarizers, power monitors, bellows, waveguide switches, waveguide cooling clamps, etc. Details of the components and test results will be presented. 相似文献
36.
Moriwaki H Takagi Y Tanaka M Tsuruho K Okitsu K Maeda Y 《Environmental science & technology》2005,39(9):3388-3392
Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are shown to be globally distributed, environmentally persistent, and bioaccumulative. Although the toxicities of these compounds were reported, the cleanup procedure from the environment is not developed because of their inertness. In this report the sonochemical degradations of PFOS and PFOA to the products through the fission of the perfluorocarbon chains were observed and the half-life times of the PFOS and PFOA degradations under an argon atmosphere determined to be 43 and 22 min, respectively. The shortening of perfluorocarbon chain of PFOS and PFOA leads to the lowering of the toxicity in view of the decrease of the persistence, and the technique would contribute to the remediation of the environmental pollution by these compounds. 相似文献
37.
The n-6/n-3 fatty acid (FA) ratio has increased in the Western-style diet to ~10–15:1 during the last century, which may have
contributed to the rise in cardiovascular disease (CVD). Prior studies have evaluated the effects on CVD risk factors of manipulating
the levels of n-6 and n-3 FA using food and supplements or investigated the metabolic fate of linoleic acid (LNA) and α-linolenic
acid (ALA) by varying the n-6/n-3 ratios. However, no previous studies have investigated the potential interaction between
diet ratios and supplementation with eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3). We used
a factorial design approach with adults (n = 24) in a controlled feeding trial to compare the accretion of EPA and DHA into red blood cell membranes (RBC) by adding
a direct source (algal oil supplement) of EPA and DHA in a diet with a 10:1 versus 2:1 ratio of n-6/n-3 FA. Subjects were
randomized into 8-week crossover diet sequences and each subject consumed three of four diets [10:1, 10:1 plus supplement
(10:1 + S), 2:1 and 2:1 + S]. LNA and ALA intakes were 9.4 and 7.7%, and 1.0 and 3.0% during the low and high ALA diets, respectively.
Compared to the Western-style 10:1 diet, the 2:1 diet increased EPA by 60% (P < 0.0001) in RBC membranes without the direct EPA source and a 34% increase (P = 0.027) was observed with the 10:1 + S diet; however, DHA levels increased in both diet ratios only with a direct DHA source.
Shifting towards a 2:1 diet is a valid alternative to taking EPA-containing supplements. 相似文献
38.
K. Kainosho M. Ohta M. Uchida M. Nakamura O. Oda 《Journal of Electronic Materials》1996,25(3):353-356
Recently, it was found that undoped semi-insulating InP can be obtained by highpressure annealing of high purity materials.
The reproducibility and the uniformity was, however, not satisfactory. In the present work, we found that not only Fe concentrations
but also Cr and Ni concentrations in annealed wafers were slightly increased during annealing. Since it seems that the origin
of the contamination was due to the vapor source of red phosphorus, conductive InP with a trace amount of Fe was annealed
under low phosphorus vapor pressure in order to reduce the contamination. By preventing the contamination of Cr and Ni, preparation
of semi-insulating InP became highly reproducible. The minimum Fe concentration for realizing semi-insulating InP was found
to be 1 x 1015cm−3. It was also found that the better resistivity uniformity can be obtained at higher annealing temperatures. 相似文献
39.
Kiyoharu Nakagawa Hirokazu Oda Akira Yamashita Masahiro Okamoto Yoichi Sato Hidenori Gamo Mikka Nishitani-Gamo Kazuyuki Ogawa Toshihiro Ando 《Journal of Materials Science》2009,44(1):221-226
We developed a novel spherical carbon material. The spherical carbon is composed of a high density of carbon nanotubes or
nanofilaments, and includes an oxidized diamond particle as a core. Syntheses of this carbon in high volume with high selectivity
may be possible. It is expected that this carbon will be useful as a catalyst material for fuel cells, electric double-layer
capacitors, etc. 相似文献