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排序方式: 共有1884条查询结果,搜索用时 15 毫秒
21.
Atsushi Tanaka 《Carbon》2004,42(3):591-597
The present study confirmed that highly crystalline nanofibers with controlled structure may be prepared over Fe and Fe-Ni alloy catalysts. The degree of graphitization of various carbon nanofibers (CNFs) was analyzed by using C(0 0 2) peaks from the XRD profiles. The C(0 0 2) peaks of CNFs over Fe catalyst shifted to higher angle and became narrower as the preparation temperature increased from 560 to 620 °C. Tubular CNFs prepared at temperature higher than 630 °C showed lower 2θ angles compared to those of platelet fibers. CNFs prepared over Fe-Ni catalysts tended to resemble those prepared over Fe catalysts. The degree of graphitization of platelet CNFs resembled natural graphite, while d0 0 2 of the tubular CNFs showed values below the 3.39 Å reported as a theoretical minimum for a cylindrical alignment. Lc0 0 2 of platelet and tubular CNFs increased by heat treatment at 2000 and 2800 °C though d0 0 2 changed little. A transverse section of platelet and tubular CNFs had a hexagonal shape, not a round shape. The hexagonal column allows AB stacking of hexagonal planes that can give perfect hexagonal alignment. 相似文献
22.
Thin DLC films coated on polymer surfaces are attracting considerable attention due to their wide applications and their interesting surface properties. When DLC films were coated on polymers, the resulting DLC-polymer composites are highly functionalized materials, some of which presenting dramatically improved gas barrier properties.In this paper, we will introduce several commonly used polymers including polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) for semi-crystalline polymers, and polymethyl methacyrlate (PMMA) for an amorphous polymer. The polymers were coated with thin DLC films and the gas barrier properties of the resulting DLC-polymer composites were investigated. Some of the DLC-polymer composites dramatically improved their gas barrier properties while they presented horizontal crack lines and vertical micro-buckling lines on the DLC surface when stretched to a certain strain. The gas barrier properties of the DLC-polymer composites with fractured DLC surface were also studied. It was found that the gas barrier property of the polymer substrates with lower residual strains was less damaged, when the substrates were mechanically deformed, than that of the polymer substrates with higher residual strains. When the number of the cracks increases, the strain imposed on each crack decreases, since the overall deformation is almost equally distributed to each crack while the crack spacing of each crack becomes shorter. Thus, it was found that the degradation of the gas barrier property after mechanical deformation is dependent on the residual strain of the polymers and the number of cracks on DLC films. 相似文献
23.
Daiji Noda Makoto Tanaka Kazuma Shimada Wataru Yashiro Atsushi Momose Tadashi Hattori 《Microsystem Technologies》2008,14(9-11):1311-1315
X-ray imaging is a very important technology in the fields of medical, biological, inspection, material science, etc. However, it is not enough to get the clear X-ray imaging with low absorbance. We have produced a diffraction gratings for obtaining high resolution X-ray phase imaging, such as X-ray Talbot interferometer. In this X-ray Talbot interferometer, diffraction gratings were required to have a fine, high accuracy, high aspect ratio structure. Then, we succeeded to fabricate a high aspect ratio diffraction grating with a pitch of 8 μm and small area using a deep X-ray lithography technique. We discuss that the diffraction gratings having a narrow pitch and an large effective area to obtain imaging size of practical use in medical application. If the pitch of diffraction gratings were narrow, it is expected high resolution imaging for X-ray Talbot interferometer. We succeeded and fabricated the diffraction grating with pitch of 5.3 μm, Au height of 28 μm and an effective area of 60 × 60 mm2. 相似文献
24.
Hee-Byoung Choi Atsushi Konno Masaru Uchiyama 《International Journal of Control, Automation and Systems》2009,7(5):858-864
It is well known that the forward kinematics of parallel robots is a very difficult problem. Closed-form forward kinematics
solutions have been reported only to a few special classes of parallel robots. This paper presents closed-form forward kinematics
solutions of a 4-DOF parallel robot H4. A 16th order polynomial in a single variable is derived to solve the forward kinematics
of the H4. The 16 roots of the polynomial lead to at most 16 different forward kinematics solutions. A numerical verification
is also presented. 相似文献
25.
Atsushi Kawamoto 《Structural and Multidisciplinary Optimization》2009,37(4):429-433
This paper deals with the design of compliant mechanisms in a continuum-based finite-element representation. Because the displacements
of mechanisms are intrinsically large, the geometric nonlinearity is essential for designing such mechanisms. However, the
consideration of the geometric nonlinearity may cause some instability in topology optimization. The problem is in the analysis
part but not in the optimization part. To alleviate the analysis problem and eventually stabilize the optimization process,
this paper proposes to apply the Levenberg–Marquardt method to the nonlinear analysis of compliant mechanisms. 相似文献
26.
In the reinforcement learning system, the agent obtains a positive reward, such as 1, when it achieves its goal. Positive
rewards are propagated around the goal area, and the agent gradually succeeds in reaching its goal. If you want to avoid certain
situations, such as dangerous places or poison, you might want to give a negative reward to the agent. However, in conventional
Q-learning, negative rewards are not propagated in more than one state. In this article, we propose a new way to propagate
negative rewards. This is a very simple and efficient technique for Q-learning. Finally, we show the results of computer simulations
and the effectiveness of the proposed method. 相似文献
27.
28.
Atsushi Kameda Masahito Yamamoto Azuma Ohuchi Satsuki Yaegashi Masami Hagiya 《Natural computing》2008,7(2):287-298
DNA machines consisting of consecutive hairpins, which we have previously described, have various potential applications in
DNA computation. In the present study, a 288-base DNA machine containing four consecutive hairpins was successfully constructed
by ligation and PCR. PAGE and fluorescence spectroscopy experiments verified that all four hairpins were successfully opened
by four opener oligomers, and that hairpin opening was dependent on the proper openers added in the correct order. Quantitative
analysis of the final results by fluorescence spectroscopy indicated that all four hairpins were open in about 1/4 to 1/3
of the DNA machines. 相似文献
29.
Real robots should be able to adapt autonomously to various environments in order to go on executing their tasks without breaking
down. They achieve this by learning how to abstract only useful information from a huge amount of information in the environment
while executing their tasks. This paper proposes a new architecture which performs categorical learning and behavioral learning
in parallel with task execution. We call the architectureSituation Transition Network System (STNS). In categorical learning, it makes a flexible state representation and modifies it according to the results of behaviors.
Behavioral learning is reinforcement learning on the state representation. Simulation results have shown that this architecture
is able to learn efficiently and adapt to unexpected changes of the environment autonomously.
Atsushi Ueno, Ph.D.: He is a research associate in the Artificial Intelligence Laboratory at the Graduate School of Information Science at the
Nara Institute of Science and Technology (NAIST). He received the B.E., the M.E., and the Ph.D. degrees in aeronautics and
astronautics from the University of Tokyo in 1991, 1993, and 1997 respectively. His research interest is robot learning and
autonomous systems. He is a member of Japan Association for Artificial Intelligence (JSAI).
Hideaki Takeda, Ph.D.: He is an associate professor in the Artificial Intelligence Laboratory at the Graduate School of Information Science at the
Nara Institute of Science and Technology (NAIST). He received his Ph.D. in precision machinery engineering from the University
of Tokyo in 1991. He has conducted research on a theory of intelligent computer-aided design systems, in particular experimental
study and logical formalization of engineering design. He is also interested in multiagent architectures and ontologies for
knowledge base systems. 相似文献
30.
Japanese/English Cross-Language Information Retrieval: Exploration of Query Translation and Transliteration 总被引:1,自引:0,他引:1
Cross-language information retrieval (CLIR), where queriesand documents are in different languages, has of late become one ofthe major topics within the information retrieval community. Thispaper proposes a Japanese/English CLIR system, where we combine aquery translation and retrieval modules. We currently target theretrieval of technical documents, and therefore the performance of oursystem is highly dependent on the quality of the translation oftechnical terms. However, the technical term translation is stillproblematic in that technical terms are often compound words, and thusnew terms are progressively created by combining existing basewords. In addition, Japanese often represents loanwords based on itsspecial phonogram. Consequently, existing dictionaries find itdifficult to achieve sufficient coverage. To counter the firstproblem, we produce a Japanese/English dictionary for base words, andtranslate compound words on a word-by-word basis. We also use aprobabilistic method to resolve translation ambiguity. For the secondproblem, we use a transliteration method, which corresponds wordsunlisted in the base word dictionary to their phonetic equivalents inthe target language. We evaluate our system using a test collectionfor CLIR, and show that both the compound word translation andtransliteration methods improve the system performance. 相似文献