Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99


Any time

2019 ( 111 )

2018 ( 872 )

2017 ( 810 )

2016 ( 782 )

Custom range...

Search Results: 1 - 10 of 60489 matches for " YE Yi-dong "
All listed articles are free for downloading (OA Articles)
Page 1 /60489
Display every page Item
The Pattern of Cooperative Groups Combined with Farmers--The choice of organization mode in the process of the Chinese country institutional change

CHAI Xiao-wu,YE Yi-dong,

浙江大学学报(人文社会科学版) , 2006,
Abstract: 立足于中国农村经营制度变迁过程,以家庭经营的"规模有效性"和"有限理性、追求效用最大化"为前提,对目前盛行的"龙头企业+农户"的组织模式给予效率比较,以"声誉机制"或专用性投资来产生商品契约的稳定性,会导致龙头企业对农民的强力支配和非合作状态,抢夺"合作剩余",剥夺农户利益.对此,农户迫切需要成立自己的经济利益体--合作社,以寻求市场力量均衡,改变弱势地位,实现和保障自己的利益.在肯定强制性变迁的同时,应强调农民"自己作主",而"农业合作社+农户"会提高群体的社会谈判能力,解决农村制度创新的瓶颈.
A Coherent Physics Picture of Topological Insulators at Single-Particle Level
Yi-Dong Wu
Physics , 2011,
Abstract: The study of topological property of band insulators is an interesting branch of condensed matter physics. Two types of topologically nontrivial insulators have been extensively studied. The first type is characterized by a nonzero TKNN invariant or Chern number[1] which is directly related to the quantization of Hall conductance in the integer quantum Hall effect. Haledane propose a model with this type of band structure even in the absence of a macroscopic magnetic field[2]. We refer to such materials "Chern insulator". The second type called "Z2 topological insulators" is proposed recently[3, 4]. Quantum spin Hall effect has been predicted and observed in such systems.[5, 6]. Despite the recent intensively study there are still some fundamental problems that aren't quite clear about Z2 insulators even at the single-particle level. For example, it's claimed that Z2 insulators will return to its origin state after two cycles, thus coupling to the reservoirs is important for the Z2 insulators to continuously pump spin[7]. Theoretical and experimental results show quantum spin Hall effect is an edge state transport property of the materials and coupling to the reservoir seems not play an important role. So the Z2 picture is not satisfactory in explaining these phenomena. We study the relationship of the ground states of Z2 insulators and that of Chern insulator. Combined with the results of recent researches on polarization of Chern insulators[8] and topology of edge states[9] we propose a coherent physics picture of topological insulators.
On the single-electron theory of quantum spin Hall effect in two dimensional topological insulators
Yi-Dong Wu
Physics , 2013,
Abstract: Recently we wrote a paper on the theory of the quantum spin Hall effect(QSHE) in two dimensional(2D) topological insulators(TIs)1 which have been considered as do not add much new insight to the exhaustively studied topic of TI within a single-electron picture by the referees. In this paper we review the papers on the mechanism of the QSHE which have significant influence on understanding of the subject. By illustrating the failures of the previous works we show our paper do contribute a different point of view to this topic, which we believe is not only a new but also the correct way to approach the problem at the single-electron level.
Band Topology or Geometry?
Yi-Dong Wu
Physics , 2011,
Abstract: The study of topology of energy bands in solid has always been interesting and fruitful. Historically, Thouless et al proposed the TKNN number or Chern number of the energy bands to explain the quantization of Hall conductance in the integer quantum Hall effect. Recently, Z2 topological insulators have been intensively studied and similarly topological crystalline insulators are proposed.These materials exhibit nontrivial charge or spin transport properties that is due to the existence of metallic edge states. The edge states are protect by the topology of the energy bands of the bulk material and the band topology are described by some invariants similar to the TKNN number. However, these invariants are crude and strongly dependent on the symmetry. Here we give an unified picture of the relationship of the edge states and the geometry of the energy bands. We show the band geometry determines not only the topological but also the geometrical properties of the edge states and the picture is applicable when the symmetries are broken.
Chern pump: a bridge between integer quantum Hall effect and quantum spin Hall effect
Yi-Dong Wu
Physics , 2012,
Abstract: We propose a electron-pumping mechanism called Chern pump to explain the integer quantum Hall effect(IQHE) in the Chern insulator. By using the parallel transport gauge in the hybrid Wannier representation we establish the bulk and edge states correspondence in the Chern insulator. The same correspondence can also be established in two dimensional(2D) topological insulator(TI). So we can consider 2D TI as two time reversal(TR) related CIs put together. The quantum spin Hall effect(QSHE) can be viewed as two TR related Chern pumps pumping electrons to opposite directions. Compared with the Z2 spin pump, the two Chern pumps explanation of QSHE is inherently 2D and predict that the QSHE can be detected in isolated device, thus make the QSHE directly measurable.
Comment on "Time reversal polarization and a Z2 adiabatic spin pump"
Yi-Dong Wu
Physics , 2013,
Abstract: In Ref 1[Phy. Rev. B 74, 195312(2006)] Fu and Kane propose a spin pump for onedimensional (1D) insulating Hamiltonians. They claim that this spin pump is a Z2 pump because For an isolated system, a single closed cycle of the pump changes the expectation value of the spin at each end even when spin-orbit interactions violate the conservation of spin. A second cycle, however, returns the system to its original state. A Z2 topological invariant is proposed to characterize the Z2 pump. In this comment we show their discussion on the spin pump is inaccurate. Their reason why the isolated system return to its original state after second cycle is unjustified and several claims contradict to this return of the system are made in Ref 1. Detailed calculations and concrete examples show the degeneracy of the first excited state at t = 0, T; is not split by the electron-electron interaction in the way described in Ref 1 and there is level crossing at t = T. In fact, despite of a detailed search, not a single system behave as described in Fig. 1(d) in Ref 1 has been found. Thus we conclude the isolated system won't return to its original state after two cycles and the spin pump is not a Z2 pump in general.
Termination Analysis of General Logic Programs for Moded Queries: A Dynamic Approach
Yi-Dong Shen,Danny De Schreye
Computer Science , 2005,
Abstract: The termination problem of a logic program can be addressed in either a static or a dynamic way. A static approach performs termination analysis at compile time, while a dynamic approach characterizes and tests termination of a logic program by applying a loop checking technique. In this paper, we present a novel dynamic approach to termination analysis for general logic programs with moded queries. We address several interesting questions, including how to formulate an SLDNF-derivation for a moded query, how to characterize an infinite SLDNF-derivation with a moded query, and how to apply a loop checking mechanism to cut infinite SLDNF-derivations for the purpose of termination analysis. The proposed approach is very powerful and useful. It can be used (1) to test if a logic program terminates for a given concrete or moded query, (2) to test if a logic program terminates for all concrete or moded queries, and (3) to find all (most general) concrete/moded queries that are most likely terminating (or non-terminating).
Unsupervised Feature Selection with Adaptive Structure Learning
Liang Du,Yi-Dong Shen
Computer Science , 2015,
Abstract: The problem of feature selection has raised considerable interests in the past decade. Traditional unsupervised methods select the features which can faithfully preserve the intrinsic structures of data, where the intrinsic structures are estimated using all the input features of data. However, the estimated intrinsic structures are unreliable/inaccurate when the redundant and noisy features are not removed. Therefore, we face a dilemma here: one need the true structures of data to identify the informative features, and one need the informative features to accurately estimate the true structures of data. To address this, we propose a unified learning framework which performs structure learning and feature selection simultaneously. The structures are adaptively learned from the results of feature selection, and the informative features are reselected to preserve the refined structures of data. By leveraging the interactions between these two essential tasks, we are able to capture accurate structures and select more informative features. Experimental results on many benchmark data sets demonstrate that the proposed method outperforms many state of the art unsupervised feature selection methods.
Linear Tabling Strategies and Optimizations
Neng-Fa Zhou,Taisuke Sato,Yi-Dong Shen
Computer Science , 2007,
Abstract: Recently, the iterative approach named linear tabling has received considerable attention because of its simplicity, ease of implementation, and good space efficiency. Linear tabling is a framework from which different methods can be derived based on the strategies used in handling looping subgoals. One decision concerns when answers are consumed and returned. This paper describes two strategies, namely, {\it lazy} and {\it eager} strategies, and compares them both qualitatively and quantitatively. The results indicate that, while the lazy strategy has good locality and is well suited for finding all solutions, the eager strategy is comparable in speed with the lazy strategy and is well suited for programs with cuts. Linear tabling relies on depth-first iterative deepening rather than suspension to compute fixpoints. Each cluster of inter-dependent subgoals as represented by a top-most looping subgoal is iteratively evaluated until no subgoal in it can produce any new answers. Naive re-evaluation of all looping subgoals, albeit simple, may be computationally unacceptable. In this paper, we also introduce semi-naive optimization, an effective technique employed in bottom-up evaluation of logic programs to avoid redundant joins of answers, into linear tabling. We give the conditions for the technique to be safe (i.e. sound and complete) and propose an optimization technique called {\it early answer promotion} to enhance its effectiveness. Benchmarking in B-Prolog demonstrates that with this optimization linear tabling compares favorably well in speed with the state-of-the-art implementation of SLG.
Termination Prediction for General Logic Programs
Yi-Dong Shen,Danny De Schreye,Dean Voets
Computer Science , 2009,
Abstract: We present a heuristic framework for attacking the undecidable termination problem of logic programs, as an alternative to current termination/non-termination proof approaches. We introduce an idea of termination prediction, which predicts termination of a logic program in case that neither a termination nor a non-termination proof is applicable. We establish a necessary and sufficient characterization of infinite (generalized) SLDNF-derivations with arbitrary (concrete or moded) queries, and develop an algorithm that predicts termination of general logic programs with arbitrary non-floundering queries. We have implemented a termination prediction tool and obtained quite satisfactory experimental results. Except for five programs which break the experiment time limit, our prediction is 100% correct for all 296 benchmark programs of the Termination Competition 2007, of which eighteen programs cannot be proved by any of the existing state-of-the-art analyzers like AProVE07, NTI, Polytool and TALP.
Page 1 /60489
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.