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ON THE QUASI-RANDOM CHOICE METHOD FOR THE LIOUVILLE EQUATION OF GEOMETRICAL OPTICS WITH DISCONTINUOUS WAVE SPEED

Journal of Computational Mathematics 2013年第6期31卷 573-591页

作者： Jingwei Hu Shi Jin Institute for Computational Engineering and Sciences (ICES) The University of Texas at Austin 201 East 24th St Stop C0200 Austin TX 78712 USA Department of Mathematics University of Wisconsin-Madison 480 Lincoln Drive Madison WI 53706 USA Department of Mathematics Institute of Natural Sciences and MOE Key Lab in Scientific and Engineering Computing Shanghai Jiao Tong University Shanghai 200240 China

We study the quasi-random choice method （QRCM） for the Liouville equation of ge- ometrical optics with discontinuous locM wave speed. This equation arises in the phase space computation of high frequency waves through interfaces, where waves undergo partial transmissions and reflections. The numerical challenges include interface, contact discon- tinuities, and measure-valued solutions. The so-called QRCM is a random choice method based on quasi-random sampling （a deterministic alternative to random sampling）. The method not only is viscosity-free but also provides faster convergence rate. Therefore, it is appealing for the prob!em under study which is indeed a Hamiltonian flow. Our analy- sis and computational results show that the QRCM 1） is almost first-order accurate even with the aforementioned discontinuities; 2） gives sharp resolutions for all discontinuities encountered in the problem; and 3） for measure-valued solutions, does not need the level set decomposition for finite difference/volume methods with numerical viscosities.

关键词： Liouville equation High frequency wave Interface Measure-valued solution,Random choice method Quasi-random sequence.

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A proof system in PADS

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10th International Colloquium on Theoretical Aspects of computing, ICTAC 2013

作者： Yao, Xinghua Zhang, Min Chen, Yixiang MoE Engineering Research Center for Software/Hardware Co-design Technology and Application East China Normal University Shanghai China Shanghai Key Laboratory of Trustworthy Computing East China Normal University Shanghai China

ISBN: (纸本)9783642397172

The PADS (Process Algebra for Demand and Supply) framework is an approach to model resource demand and supply for the formal analysis of hierarchical scheduling. Inspired by the demand relation in PADS, we propose a weak demand relation covering several cases which can not be described by a demand relation. And we explore some properties of weak demand relation which are similar to properties of demand relation. Especially, if two tasks are in a weak demand relation then their schedulabilities are closely related. Furthermore, we present a proof system for the weak demand relation in a decomposing-composing way, which helps to compare two tasks' schedulabilities. Finally, we prove that the proof system is sound and complete with respect to the semantic definition of weak demand relation. © 2013 Springer-Verlag Berlin Heidelberg.

关键词： Semantics

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A Subspace Version of the Powell–Yuan Trust-Region Algorithm for Equality Constrained Optimization

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Journal of the Operations Research Society of China 2013年第4期1卷 425-451页

作者： Geovani Nunes Grapiglia Jinyun Yuan Ya-xiang Yuan Departamento de Matemática Universidade Federal do ParanáCentro PolitécnicoCx.postal 19.08181531-980CuritibaParanáBrazil The Capes Foundation Ministry of Education of BrazilCx.postal 25070.040-020BrasíliaDistrito FederalBrazil State Key Laboratory of Scientific/Engineering Computing Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of SciencesZhongguancundonglu 55Beijing 100190P.R.China

This paper studied subspace properties of the Celis–Dennis–Tapia(CDT)subproblem that arises in some trust-region algorithms for equality constrained opti*** analysis is an extension of that presented by Wang and Yuan(***.104:241–269,2006)for the standard trust-region *** suitable conditions,it is shown that the trial step obtained from the CDT subproblem is in the subspace spanned by all the gradient vectors of the objective function and of the constraints computed until the current *** on this observation,a subspace version of the Powell–Yuan trust-region algorithm is proposed for equality constrained optimization problems where the number of constraints is much lower than the number of variables. The convergence analysis is given and numerical results arealso reported.

关键词： Constrained optimization Trust-region methods Subspace methods

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Electrostatic interaction in the presence of dielectric interfaces and polarization-induced like-charge attraction

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Physical Review E 2013年第1期87卷 013307-013307页

作者： Zhenli Xu []Department of Mathematics Institute of Natural Sciences and Ministry of Education Key Laboratory in Scientific and Engineering Computing Shanghai Jiao Tong University Shanghai 200240 China

Electrostatic polarization is important in many nano- and micro-scale physical systems such as colloidal suspensions, biopolymers, and nanomaterials assembly. The calculation of polarization potential requires an efficient algorithm for solving 3D Poisson's equation. We have developed a useful image charge method to rapid evaluation of the Green's function of the Poisson's equation in the presence of spherical dielectric discontinuities. This paper presents an extensive study of this method by giving a convergence analysis and developing a coarse-graining algorithm. The use of the coarse graining could reduce the number of image charges to around a dozen, by 1–2 orders of magnitude. We use the algorithm to investigate the interaction force between likely charged spheres in different dielectric environments. We find the size and charge asymmetry leads to an attraction between like charges, in agreement with existing results. Furthermore, we study three-body interactions and find, in the presence of an external interface, that the interaction force depends on the curvature of the interface and performs a nonmonotonic electrostatic force.

关键词： ELECTROSTATICS INTERFACES (Physical sciences) POLARIZATION (Electricity) POISSON'S equation NONMONOTONIC logic GREEN'S functions

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Improving function word alignment with frequency and syntactic information

Improving function word alignment with frequency and syntact...

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23rd International Joint Conference on Artificial Intelligence, IJCAI 2013

作者： Zhang, Jingyi Zhao, Hai MOE-Microsoft Key Laboratory of Intelligent Computing and Intelligent System Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China Department of Computer Science and Engineering Shanghai Jiao Tong University 800 Dongchuan Road Shanghai 200240 China

ISBN: (纸本)9781577356332

In statistical word alignment for machine translation, function words usually cause poor aligning performance because they do not have clear correspondence between different languages. This paper proposes a novel approach to improve word alignment by pruning alignments of function words from an existing alignment model with high precision and recall. Based on monolingual and bilingual frequency characteristics, a language-independent function word recognition algorithm is first proposed. Then a group of carefully defined syntactic structures combined with content word alignments are used for further function word alignment pruning. The experimental results show that the proposed approach improves both the quality of word alignment and the performance of statistical machine translation on Chinese-to-English, Germanto- English and French-to-English language pairs.

关键词： Alignment

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Recent Development in Symmetries and Integrability of Difference Equations

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Frontiers of Mathematics in China 2013年第5期8卷 999-1000页

作者： Xingbiao HU Qingping LIU Senyue LOU Changzheng QU Youjin ZHANG Institute of Computational Mathematics and Scientific Engineering Computing Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China Department of Mathematics China University of Mining and Technology~Beijing i00083 China Shanghai Key Laboratory of Trustworthy Computing East China Normal University Shanghai 200062 China Faculty of Sciences Ningbo University Ningbo 315211 China Center for Nonlinear Studies Ningbo University Ningbo 315211 China Department of Mathematical Sciences Tsinghua University Beijing 100084 China

Difference equations or discrete systems are mathematical models of various fields such as physics, chemistry, biology, and economics and have been subjects of extensive study of both pure mathematicians and applied mathematicians. Through its interaction with modern integrable systems, the theory of difference equations is enriched greatly and has been undergoing a rapid development. SIDE-10, the tenth of a series of biennial conferences devoted to Symmetries and Integrability of Difference Equations and related topics, was held during 10-16 June, 2012 at Ningbo, China. It was sponsored and supported by the National Natural Science Foundation of China, Ningbo Association of Science and Technology, Ningbo University, Academy of Mathematics and Systems Science of Chinese Academy of Sciences, China University of Mining and Technology （Beijing）, Tsinghua University, and Shanghai University. The conference attracted over 100 participants from more than a dozen of countries. During the conference, 44 contributed talks were arranged and the topics covered by the meeting include

关键词： DIFFERENCE algebra INTEGRABLE functions DIFFERENTIAL geometry

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Existence theory for Rosseland equation and its homogenized equation

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Applied Mathematics and Mechanics(English Edition) 2012年第12期33卷 1595-1612页

作者：张乔夫崔俊芝 State Key Laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific/Engineering ComputingAcademy of Mathematics and Systems ScienceChinese Academy of Sciences

The global boundness and existence are presented for the kind of the Rosseland equation with a general growth condition. A linearized map in a closed convex set is defined. The image set is precompact, and thus a fixed point exists. A multi-scale expansion method is used to obtain the homogenized equation. This equation satisfies a similar growth condition.

关键词： nonlinear elliptic equations fixed points mixed boundary conditions growthconditions maximal regularitys homogenized equation

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Converting continuous-space language models into N-gram language models for statistical machine translation

Converting continuous-space language models into N-gram lang...

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2013 Conference on Empirical Methods in Natural Language Processing, EMNLP 2013

作者： Wang, Rui Utiyama, Masao Goto, Isao Sumita, Eiichro Zhao, Hai Lu, Bao-Liang Center for Brain-Like Computing and Machine Intelligence Department of Computer Science and Engineering Shanghai Jiao Tong Unviersity Shanghai200240 China Multilingual Translation Laboratory MASTAR Project National Institute of Information and Communications Technology 3-5 Hikaridai Keihanna Science City Kyoto619-0289 Japan MOE-Microsoft Key Lab. for Intelligent Computing and Intelligent Systems Shanghai Jiao Tong Unviersity Shanghai200240 China

ISBN: (纸本)9781937284978

Neural network language models, or continuous-space language models (CSLMs), have been shown to improve the performance of statistical machine translation (SMT) when they are used for reranking n-best translations. However, CSLMs have not been used in the first pass decoding of SMT, because using CSLMs in decoding takes a lot of time. In contrast, we propose a method for converting CSLMs into back-off n-gram language models (BNLMs) so that we can use converted CSLMs in decoding. We show that they outperform the original BNLMs and are comparable with the traditional use of CSLMs in reranking. © 2013 Association for Computational Linguistics.

关键词： Decoding

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NEURAL SUBSTRATES OF MOTOR IMAGERY BASED BRAIN-COMPUTER INTERFACE TRAINING FOR STROKE PATIENTS WITH SEVERE UPPER LIMB PARALYSIS

NEURAL SUBSTRATES OF MOTOR IMAGERY BASED BRAIN-COMPUTER INTE...

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第七届国际物理医学与康复医学学术大会(7th World Congress of the international society of Physical and Rehabilitation Medicine(ISPRM2013)

作者： Mingfen Li Jie Jia Ye Liu Department of Rehabilitation Huashan Hospital Fudan University MOE-Microsoft Key Laboratory for Intelligent Computing and Intelligent Systems Department of Computer Science and Engineering Shanghai Jiao Tong University China

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An empirical study on word segmentation for Chinese machine translation

An empirical study on word segmentation for Chinese machine ...

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14th Annual Conference on Intelligent Text Processing and Computational Linguistics, CICLing 2013

作者： Zhao, Hai Utiyama, Masao Sumita, Eiichiro Lu, Bao-Liang MOE-Microsoft Key Laboratory of Intelligent Computing and Intelligent System Shanghai Jiao Tong University #800 Dongchuan Road Shanghai 200240 China Department of Computer Science and Engineering Shanghai Jiao Tong University #800 Dongchuan Road Shanghai 200240 China Multilingual Translation Laboratory MASTAR Project National Institute of Information and Communications Technology 3-5 Hikaridai Keihanna Science City Kyoto 619-0289 Japan

ISBN: (纸本)9783642372551

Word segmentation has been shown helpful for Chinese-to-English machine translation (MT), yet the way different segmentation strategies affect MT is poorly understood. In this paper, we focus on comparing different segmentation strategies in terms of machine translation quality. Our empirical study covers both English-to-Chinese and Chinese-to-English translation for the first time. Our results show the necessity of word segmentation depends on the translation direction. After comparing two types of segmentation strategies with associated linguistic resources, we demonstrate that optimizing segmentation itself does not guarantee better MT performance, and segmentation strategy choice is not the key to improve MT. Instead, we discover that linguistical resources such as segmented corpora or the dictionaries that segmentation tools rely on actually determine how word segmentation affects machine translation. Based on these findings, we propose an empirical approach that directly optimize dictionary with respect to the MT task for word segmenter, providing a BLEU score improvement of 1.30. © 2013 Springer-Verlag.

关键词： Machine translation

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