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排序方式: 共有1848条查询结果,搜索用时 15 毫秒
41.
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
42.
High-temperature oxidation of Al-deposited stainless-steel foils 总被引:2,自引:0,他引:2
The oxidation resistance of Al-deposited Fe–Cr–Al foils containing small amounts of La and Ce was assessed by a cyclic oxidation test with temperature varying between room temperature and 1323 K to 1423 K in static air. (1) The Al content of Fe–Cr–Al–La, Ce foils can be increased by depositing an Al layer from the vapor phase. The deposition of a 1-m-thick Al layer on both sides of the 50-m-thick foil is equivalent to a 1.5 mass% increase in the Al content. The deposited Al diffuses into the foil during heat treatment. The uniform distribution of Al is obtained by heating at 1273 K for 18 ks. (2) After the initial transition stage the oxidation follows the parabolic law until breakaway sets in. The scale consists mainly of -Al2O3 during the parabolic period. (3) The increase in the Al content by more than 5 mass% by the Al-deposition remarkably improves high-temperature oxidation resistance (smaller parabolic rate constant and longer protection time). (4) The Al-deposited foils have better oxidation resistance than the conventional foils with the same contents of Al and rare-earth elements. This is attributable to the different nature of the initially formed oxide on the Al-deposited foil. (5) The so-called rare-earth element effect was also observed for the Al-deposited foils. Predominant diffusion of oxygen through the Al2O3 scale and vacancy-sink mechanism are applicable to the present results. 相似文献
43.
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
44.
45.
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
46.
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
47.
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
48.
Ryo Minegishi Atsushi Takashima Daisuke Kurabayashi Ryohei Kanzaki 《Robotics and Autonomous Systems》2012,60(5):692-699
Insects perform adaptive behavior according to changing environmental conditions using comparatively small brains. Because adaptability is generated through the relationship among brain, body and environment, it is necessary to examine how a brain works under these conditions. In this study, to understand neural processing involved in adaptive behavior, we constructed a brain–machine hybrid system using motor signals related to the steering behavior of the male silkworm moth for controlling a two-wheeled mobile robot. We developed this hybrid system according to the following steps. (1) We selected steering signals corresponding to walking direction that were activated during neck swinging induced by optic flow and pheromone stimuli. (2) To control a robot by neural activity, we implemented a spike-behavior conversion rule such that frequency of the left and right neck motor neurons’ spikes was linearly converted into rotation of the wheels. (3) For electrophysiological multi-unit recordings on a robot, we developed small amplifiers. Using this hybrid system, we could observe the programmed behavioral pattern and orientation toward a pheromone source. Moreover, we compared the orientation behavior of moths and that of the hybrid system at different pheromone stimulus frequencies. From these experiments, we concluded that we could reconstruct silkworm moth behavior on the hybrid system. 相似文献
49.
Humans and animals seek appropriate solutions to novel problems through trial-and-error (TE) actions and observation of their outcomes. Once an individual has obtained the knowledge (rule) to solve a problem, knowledge-based (KB) actions may be applied in a stereotypical manner. Solutions can thus be based on TE or KB actions. To characterize this learning process at the behavioral level, we developed a new cognitive task for a laboratory monkey (Macaca fuscata) to perform. In this task, a search array consisting of six elements of different colors was presented, one of which was the behaviorally relevant target. The target color was changed unpredictably with no instruction or signal, requiring the monkey to use a TE search strategy to find the target color. We found that once the monkey identified the relevant color by chance after a color change, correct performance increased in a step-like manner and at the same time, other response properties (reaction time and color-choice tendency) also changed discontinuously. These step-like alternations in behavioral performance may be attributed to the subject’s switching between TE and KB search strategies in the two phases. The present study has therefore provided behavioral evidence for the timing and manner of switching between search strategies during the process of updating knowledge. 相似文献
50.
Effect of heparin on high glucose induced proliferation and expression of matrix metalloproteinases in normal human mesangial cells 总被引:1,自引:0,他引:1
Zhou Qiao-ling Yasumoto Yuichiro Tsukamoto Masatoshi Nozaki Tsuyoshi Sogabe Atsushi Harada Kouji Zhang Yi-xiang Lin Xiao-yan Zhang Yang-de Arima Terukatsu 《中南工业大学学报(英文版)》2005,12(1):359-364
Background The pathogenesis of diabetic nephropathy (DN) is a complex pathophysiological process. Its precise mechanism is not fully
known. In recent years it has been recognized that synthesis of various extracelluar matrix (ECM) components may increase,
and that degradation of ECM may decrease in DN. It was reported heparin could inhibit mesangial cells proliferation in vitro.
The main aim of this study is to explore whether heparin inhibits proliferation of mesangial cells grown in high glucose concentration
and to measure the effect of heparin on matrix metalloproteinases (MMPs) expression in mesangial cells. Methods The medium contained either low glucose (5 mmol/L) or high glucose (25 mmol/L). The concentrations of heparin in the culture
medium were 0, 25, 50, 100, 200 or 400 μg/mL. A metabolic (WST-1) assay was used to measure mesangial cell proliferation and
Western blot analysis was used to measure MMPs expression of mesangial cells. Results Normal human mesangial cell (NHMC) proliferation was higher in high glucose (HG) medium than in low glucose (LG) medium.
They showed a 1.93 fold expansion after 72 h in high glucose in contrast to a 1.63 fold expansion in low glucose. In the presence
of heparin, mesangial cells proliferation was inhibited, which was more obvious at high glucose concentrations than at low
glucose concentrations. In high glucose, with heparin concentration of 50, 100, 200 and 400 μg/mL, the mesangial cells showed
a 0.61 fold, 0.52 fold, 0.52 fold and 0.41 fold reductions in cell number compared to cells grown without heparin. In low
glucose, only concentrations of 200 μg/mL and 400 μg/mL showed reduction in cell number, namely 0.54 fold and 0.45 fold, when
compared to cells grown without heparin. In Western blot analysis, MMP1, MMP2, MMP3 and MMP9 was expressed by mesangial cells expressed in both high and low glucose concentrations, which was more prominent in high
glucose medium. Incubation of heparin further increased expression of MMP1, MMP2, MMP3 and MMP9. Conclusions This study suggests that glucose can accelerate mesangial cell proliferation while heparin can reduce proliferation, being
more obvious at high glucose concentrations. Higher glucose concentrations led to increased MMP expression, which may take
part in the regulation of mesangial matrix synthesis and degradation. Addition of heparin resulted in a corresponding increase
in MMP expression, most notably at high glucose concentrations, indicating a potentially renoprotective role in DN.
Foundation item: Project (30370663) supported by the National Natural Science Foundation of China 相似文献