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排序方式: 共有2403条查询结果,搜索用时 0 毫秒
41.
Hanxiong Chen Jianquan Liu Kazutaka Furuse Jeffrey Xu Yu Nobuo Ohbo 《Knowledge and Information Systems》2011,27(2):165-192
Similarity search is important in information retrieval applications where objects are usually represented as vectors of high
dimensionality. This leads to the increasing need for supporting the indexing of high-dimensional data. On the other hand,
indexing structures based on space partitioning are powerless because of the well-known “curse of dimensionality”. Linear
scan of the data with approximation is more efficient in the high-dimensional similarity search. However, approaches so far
have concentrated on reducing I/O, and ignored the computation cost. For an expensive distance function such as L
p
norm with fractional p, the computation cost becomes the bottleneck. We propose a new technique to address expensive distance functions by “indexing
the function” by pre-computing some key values of the function once. Then, the values are used to develop the upper/lower
bounds of the distance between a data vector and the query vector. The technique is extremely efficient since it avoids most
of the distance function computations; moreover, it does not involve any extra secondary storage because no index is constructed
and stored. The efficiency is confirmed by cost analysis, as well as experiments on synthetic and real data. 相似文献
42.
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
43.
Summary Dehalogenation polycondensations of 2,7-dibromo-9,10-dihydrophenanthrene with isolated zero-valent nickel complex and electrochemically generated zero-valent nickel complex afford -conjugated poly(9,10-dihydrophenanthrene-2,7-diyl). The electrochemically synthesized polymer is obtained as a thin film on electrode, and shows a reversible electrochemically doping-undoping cycle in an oxidation region. The polymer has essentially the same -conjugation system as that of poly(p-phenylene). 相似文献
44.
Atsushi Ikeda Tatsuya Suzuki Masao Aida Yasuhiko Fujii Toshiaki Mitsugashira Mitsuo Hara Masaki Ozawa 《Progress in Nuclear Energy》2005,47(1-4):454-461
A novel chromatographic separation technique using a tertiary pyridine type resin has been applied to the partitioning of the trivalent actinides (An) and lanthanides (Ln) and several successful results have been shown. In an alcoholic hydrochloric acid system, the trivalent An were clearly separated from the Ln, while no such group separation was achieved in an alcoholic nitric acid system. On the other hand, the nitric acid system was more effective for the intragroup (i.e. individual) separation of the trivalent An and the Ln than the hydrochloric acid system. On the basis of these results, a novel concept for the partitioning of the trivalent An and Ln using the present separation technique and its flowchart have been proposed with its advantages and disadvantages. 相似文献
45.
Nobuo Takeda Yoji Okabe Junichiro Kuwahara Seiji Kojima Toshimichi Ogisu 《Composites Science and Technology》2005,65(15-16):2575
The authors and Hitachi Cable, Ltd. have recently developed small-diameter optical fiber and its fiber Bragg grating (FBG) sensor for embedment inside a lamina of composite laminates without strength reduction. The outside diameters of the cladding and polyimide coating are 40 and 52 μm, respectively. First, a brief summary is presented for applications of small-diameter FBG sensors to damage monitoring in composite structures. Then, we propose a new damage detection system for quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing. In this system, a piezo-ceramic actuator generates Lamb waves in a CFRP laminate. After the waves propagate in the laminate, transmitted waves are received by an FBG sensor attached on or embedded in the laminate using a newly developed high-speed optical wavelength interrogation system. This system was applied to detect interlaminar delamination in CFRP cross-ply laminates. When the Lamb waves passed through the delamination, the amplitude decreased and a new wave mode appeared. These phenomena could be well simulated using a finite element analysis. From the changes in the amplitude ratio and the arrival time of the new mode depending on the delamination length, it was found that this system could evaluate the delamination length quantitatively. Furthermore, small-diameter FBG sensors were embedded in a double-lap type coupon specimen, and the debonding progress could be evaluated using the wavelet transform. 相似文献
46.
SCARA型机械手的鲁棒防振控制 总被引:1,自引:0,他引:1
对SCARA型机械手的防振控制进行研究,提出了两自由度鲁棒控制法,应用μ控制理论设计鲁棒反馈控制器,保证了系统的鲁棒稳定性及鲁棒性能指标;基于模型匹配法设计前馈控制器,组成两自由度控制系统,进一步改善了闭环系统的跟踪特性。仿真研究表明,与传统的PD控制相比,该控制系统能对机械手前端的残留振支进行有效的抑制,取得较好的轨迹跟踪特性。 相似文献
47.
In order to investigate the effect of atomic oxygen exposure of an aluminum alloy on bubble formation during welding, electron beam welding was performed on the samples exposed to atomic oxygen produced by the oxygen plasma method. The change in the aluminum surface due to the exposure was analyzed by auger electron spectroscopy. Due to the exposure of atomic oxygen, the thickness of the aluminum oxide film increases on the surface, and pores are formed during welding. The pores can be formed by the formation of the Al2O gas through the reaction between the aluminum oxide and aluminum in a high vacuum. 相似文献
48.
Y. Sato K. Fujii N. Mitani A. Matsuura T. Kakigi F. Muto J. Li A. Oshima M. Washio 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,265(1):213-216
The performance of polymer electrolyte fuel cell (PEFC) is affected by an interfacial property between a proton exchange membrane (PEM) and electrodes. Thus, to develop a well-laminated membrane electrode assembly (MEA), a hybrid PEM (FN) was fabricated by mixing a radiation grafted membrane (sulfonated FEP) with ionomer (Nafion® dispersion) which is applied to coat the interface of the PEM and electrodes.The obtained FN, sulfonated FEP and Nafion®112 were characterized in terms of water uptake, ion exchange capacity (IEC), polarization performance and electrochemical impedance. FN showed high IEC and water uptake, which would induce the highest ionic conductivity (IC) among tested PEMs. In terms of FN, the interface between the PEM and electrodes should have been improved because FN showed the lowest charge transfer resistance than other tested PEMs. The high IC and improved interface between the PEM and electrodes resulted in the best cell performance of FN in tested PEMs. 相似文献
49.
Tomoyuki Fujii Keiichiro Tohgo Masafumi Fujioka Muhamad Safwan Bin Muhamad Azmi Kodai Kikushima Yoshinobu Shimamura 《Fatigue & Fracture of Engineering Materials & Structures》2020,43(9):1917-1927
This paper proposes an alternating bending technique for evaluating fatigue life in the low‐to‐high cycle fatigue regime. A method was developed for estimating the stress, elastic strain, and plastic strain ranges of a plastically deformed specimen subjected to alternating bending with consideration of stress and strain distributions. To evaluate its effectiveness, fatigue testing was conducted using a specimen made of a steel used for pressure vessels. The stress, elastic strain, and plastic strain ranges could be obtained during cyclic bending. The elastic strain amplitude life and plastic strain amplitude life curves were linear in a log–log plot in the low‐to‐high cycle fatigue regime. Hence, the fatigue life under alternating bending could be evaluated using the proposed strain‐based approach. However, these curves could not be predicted using equations with parameters obtained from tensile testing, such as the universal slope method, due to the strain gradient in the specimen. 相似文献
50.
A lateral current injection (LCI) multiquantum-well (MQW) laser having planar structure is proposed and its advantages compared with conventional vertical structure lasers. A LCI-MQW laser has been fabricated by using Si- and Zn-induced disordering of an MQW active layer. It is shown that a threshold current of 27 mA is achieved under pulsed current driven at room temperature and a very low stray capacitance of 0.27 pF is obtained at zero bias voltage 相似文献