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Search Results: 1 - 10 of 3239 matches for " Wenjia Niu "
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Guest Editorial
Wenjia Niu,Gang Li
Journal of Networks , 2012, DOI: 10.4304/jnw.7.6.893-894
Abstract: This special issue mainly focuses on the timely topic of “Data and Security in Web Service”. More specially, from the perspective of service construction, the future Web service should address issues such as how to construct an intelligent service which can e ectively perceive the individual behavior, identify and satisfy individual requirements. On the other hand, from the perspective of service utilization, in the dynamic environment, Web services should address issues such as how to utilizing security-related techniques. In this JNW special issue, we select and edit 6 most relevant papers with higher reviewer scores from 16 submissions, which give e ective discussion about Web service management methodologies from di erent perspective.
Cross-Modal Similarity Learning : A Low Rank Bilinear Formulation
Cuicui Kang,Shengcai Liao,Yonghao He,Jian Wang,Wenjia Niu,Shiming Xiang,Chunhong Pan
Computer Science , 2014,
Abstract: The cross-media retrieval problem has received much attention in recent years due to the rapid increasing of multimedia data on the Internet. A new approach to the problem has been raised which intends to match features of different modalities directly. In this research, there are two critical issues: how to get rid of the heterogeneity between different modalities and how to match the cross-modal features of different dimensions. Recently metric learning methods show a good capability in learning a distance metric to explore the relationship between data points. However, the traditional metric learning algorithms only focus on single-modal features, which suffer difficulties in addressing the cross-modal features of different dimensions. In this paper, we propose a cross-modal similarity learning algorithm for the cross-modal feature matching. The proposed method takes a bilinear formulation, and with the nuclear-norm penalization, it achieves low-rank representation. Accordingly, the accelerated proximal gradient algorithm is successfully imported to find the optimal solution with a fast convergence rate O(1/t^2). Experiments on three well known image-text cross-media retrieval databases show that the proposed method achieves the best performance compared to the state-of-the-art algorithms.
Limiting distribution of elliptic homogenization error with periodic diffusion and random potential
Wenjia Jing
Mathematics , 2015,
Abstract: We study the limiting probability distribution of the homogenization error for second order elliptic equations in divergence form with highly oscillatory periodic conductivity coefficients and highly oscillatory stochastic potential. The effective conductivity coefficients are the same as those of the standard periodic homogenization, and the effective potential is given by the mean. We show that in the short range correlation setting, the limiting distribution of the random part of the homogenization error, as random elements in proper Hilbert spaces, is Gaussian and can be characterized by the homogenized Green's function, the homogenized solution and the statistics of the random potential. Similar results hold for random potentials that are functions of long range correlated Gaussian random fields. These results generalize previous ones in the setting with slowly varying diffusion coefficients, and the current setting with fast oscillations in the differential operator requires new methods to prove compactness of the probability distributions of the random fluctuation.
Homogenization of Randomly Deformed Conductivity Resistant Membranes
Wenjia Jing
Mathematics , 2014,
Abstract: We study the homogenization of a stationary conductivity problem in a random heterogeneous medium with highly oscillating conductivity coefficients and an ensemble of simply closed conductivity resistant membranes. This medium is randomly deformed and then rescaled from a periodic one with periodic membranes, in a manner similar to the random medium proposed by Blanc, Le Bris and Lions \cite{BLBL06}. Across the membranes, the flux is continuous but the potential field itself undergoes a jump of Robin type. We prove that, for almost all realizations of the random deformation, as the small scale of variations of the medium goes to zero, the random conductivity problem is well approximated by that on an effective medium which has deterministic and constant coefficients and contains no membrane. The effective coefficients are explicitly represented. One of our main contributions is to provide a solution to the associated auxiliary problem that is posed on the whole domain with infinitely many interfaces, in a setting that is neither periodic nor stationary ergodic in the usual sense.
Corrector theory for MsFEM and HMM in random media
Guillaume Bal,Wenjia Jing
Mathematics , 2010, DOI: 10.1137/100815918
Abstract: We analyze the random fluctuations of several multi-scale algorithms such as the multi-scale finite element method (MsFEM) and the finite element heterogeneous multiscale method (HMM), that have been developed to solve partial differential equations with highly heterogeneous coefficients. Such multi-scale algorithms are often shown to correctly capture the homogenization limit when the highly oscillatory random medium is stationary and ergodic. This paper is concerned with the random fluctuations of the solution about the deterministic homogenization limit. We consider the simplified setting of the one dimensional elliptic equation, where the theory of random fluctuations is well understood. We develop a fluctuation theory for the multi-scale algorithms in the presence of random environments with short-range and long-range correlations. What we find is that the computationally more expensive method MsFEM captures the random fluctuations both for short-range and long-range oscillations in the medium. The less expensive method HMM correctly captures the fluctuations for long-range oscillations and strongly amplifies their size in media with short-range oscillations. We present a modified scheme with an intermediate computational cost that captures the random fluctuations in all cases.
Corrector Analysis of a Heterogeneous Multi-scale Scheme for Elliptic Equations with Random Potential
Guillaume Bal,Wenjia Jing
Mathematics , 2012,
Abstract: This paper analyzes the random fluctuations obtained by a heterogeneous multi-scale first-order finite element method applied to solve elliptic equations with a random potential. We show that the random fluctuations of such solutions are correctly estimated by the heterogeneous multi-scale algorithm when appropriate fine-scale problems are solved on subsets that cover the whole computational domain. However, when the fine-scale problems are solved over patches that do not cover the entire domain, the random fluctuations may or may not be estimated accurately. In the case of random potentials with short-range interactions, the variance of the random fluctuations is amplified as the inverse of the fraction of the medium covered by the patches. In the case of random potentials with long-range interactions, however, such an amplification does not occur and random fluctuations are correctly captured independent of the (macroscopic) size of the patches. These results are consistent with those obtained by the authors for more general equations in the one-dimensional setting and provide indications on the loss in accuracy that results from using coarser, and hence less computationally intensive, algorithms.
Fluctuations in the Homogenization of Semilinear Equations with Random Potentials
Guillaume Bal,Wenjia Jing
Mathematics , 2015,
Abstract: We study the stochastic homogenization and obtain a random fluctuation theory for semilinear elliptic equations with a rapidly varying random potential. To first order, the effective potential is the average potential and the nonlinearity is not affected by the randomness. We then study the limiting distribution of the properly scaled homogenization error (random fluctuations) in the space of square integrable functions, and prove that the limit is a Gaussian distribution characterized by the homogenized solution, the Green's function of the linearized equation around the homogenized solution, and by the integral of the correlation function of the random potential. These results enlarge the scope of the framework that we have developed for linear equations to the class of semilinear equations.
Study on a Comprehensive Energy-Saving Sail by CFD Method  [PDF]
Yanna Zheng, Dexing Liu, Hongwei An, Wenjia Sun, Tiaojian Xu
Open Journal of Fluid Dynamics (OJFD) , 2016, DOI: 10.4236/ojfd.2016.63012
Abstract: A comprehensive energy-saving sail (CES) has been proposed in order to promote energy saving and emission reduction from shipping. Wind energy is harvested for propulsion and electrical generator at the same time by a unique structure of CES. A CFD (Computational Fluid Dynamics) code is verified by a case of arc wind sail, and it is used to simulate the pressure and velocity around the CES. The results show that the outlet velocity of air tunnel Vo and wind velocity Vi serve as an equation Vo ≈ 1.31Vi, which means the CES can effectively improve the conversion efficiency. In addition, it is found that Vo increases with the tunnel diameter to some extend over which it will keep almost constant.
Effect of Fine-Grained Lexical Rating on L2 Learners’ Lexical Learning Gain  [PDF]
Ruiying Niu
Open Journal of Modern Linguistics (OJML) , 2015, DOI: 10.4236/ojml.2015.55038
Abstract: In assessing L2 lexical learning, especially initial learning, researchers always face the problem of whether partial word learning should be counted. Existing studies have either counted partial word learning (i.e. counted both partial and complete word learning) or have only counted complete word learning. However, it is not clear whether counting partial word learning makes a difference in capturing task-based and intra-learner lexical learning gain. Few studies have investigated this potential difference and even fewer if both productive and receptive lexical learning are considered. The present study employed differently fine-grained word rating methods to assess three Chinese EFL learner groups’ performances on four vocabulary posttests after receiving three treatment tasks: a written output task, an oral output task, and a reading task. Data analyses revealed that the use of differently fine-grained scoring methods did not necessarily affect learners’ cross-task lexical learning effects significantly, but it did make a significant difference in measuring individual learners’ lexical learning gain. The findings are discussed with reference to whether and how a less or more fine-grained scoring method should be adopted in rating lexical learning.
An Analysis of E-Commerce Enterprises Sustainable Development and Financing Structure  [PDF]
Yucao Niu
Theoretical Economics Letters (TEL) , 2016, DOI: 10.4236/tel.2016.65106
Abstract: O2O (Online to Offline) is a kind of new e-commerce mode and has brought new development opportunities for e-commerce enterprises. Through investing and financing, some e-commerce enterprises improved their performance rapidly in the short term. But some face serious operational risk, even bankruptcy. It’s still a question whether the e-commerce enterprises have achieved sustainable development or not. The relationship between financing structure and sustainable development needs to be studied. Based on the sustainable development theory and Higgins sustainable growth model, this paper uses SPSS to analyze the financial statement data of 98 listed e-commerce companies. The empirical results reveal that actual growth rates don’t match the sustainable growth rates, which means that E-commerce enterprises don’t achieve sustainable growth. And the sustainable growth rate is correlated with the financing structure. Lastly, this paper puts forward constructive suggestions about financing structure adjustment.
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