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Search Results: 1 - 10 of 81071 matches for " Minghui Liu "
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Exact duality in semidefinite programming based on elementary reformulations
Minghui Liu,Gabor Pataki
Mathematics , 2014,
Abstract: In semidefinite programming (SDP), unlike in linear programming, Farkas' lemma may fail to prove infeasibility. Here we obtain an exact, short certificate of infeasibility in SDP by an elementary approach: we reformulate any semidefinite system of the form Ai*X = bi (i=1,...,m) (P) X >= 0 using only elementary row operations, and rotations. When (P) is infeasible, the reformulated system is trivially infeasible. When (P) is feasible, the reformulated system has strong duality with its Lagrange dual for all objective functions. As a corollary, we obtain algorithms to generate the constraints of {\em all} infeasible SDPs and the constraints of {\em all} feasible SDPs with a fixed rank maximal solution.
Exact duals and short certificates of infeasibility and weak infeasibility in conic linear programming
Minghui Liu,Gabor Pataki
Mathematics , 2015,
Abstract: We describe simple and exact duals, and certificates of infeasibility and weak infeasibility in conic linear programming which do not rely on any constraint qualification and retain most of the simplicity of the Lagrange dual. Some of our infeasibility certificates generalize the row echelon form of a linear system of equations, and the "easy" proofs -- as sufficiency of a certificate to prove infeasibility -- are elementary. We derive some fundamental geometric corollaries: 1) an exact characterization of when the linear image of a closed convex cone is closed, 2) an exact characterization of nice cones, and 3) bounds on the number of constraints that can be dropped from, or added to a (weakly) infeasible conic LP while keeping it (weakly) infeasible. Using our infeasibility certificates we generate a public domain library of infeasible and weakly infeasible SDPs. The status of our instances is easy to verify by inspection in exact arithmetic, but they turn out to be challenging for commercial and research codes.
Quality Improvement Algorithm for Tetrahedral Mesh Based on Optimal Delaunay Triangulation  [PDF]
Shuli Sun, Haoran Bao, Minghui Liu, Yuan Yuan
Intelligent Information Management (IIM) , 2013, DOI: 10.4236/iim.2013.56021
Abstract:

The concept of optimal Delaunay triangulation (ODT) and the corresponding error-based quality metric are first introduced. Then one kind of mesh smoothing algorithm for tetrahedral mesh based on the concept of ODT is examined. With regard to its problem of possible producing illegal elements, this paper proposes a modified smoothing scheme with a constrained optimization model for tetrahedral mesh quality improvement. The constrained optimization model is converted to an unconstrained one and then solved by integrating chaos search and BFGS (Broyden-Fletcher-Goldfarb-Shanno) algorithm efficiently. Quality improvement for tetrahedral mesh is finally achieved by alternately applying the presented smoothing scheme and re-triangulation. Some testing examples are given to demonstrate the effectiveness of the proposed approach.

Stability of Analytic and Numerical Solutions for Differential Equations with Piecewise Continuous Arguments
Minghui Song,M. Z. Liu
Abstract and Applied Analysis , 2012, DOI: 10.1155/2012/258329
Abstract: In this paper, the asymptotic stability of the analytic and numerical solutions for differential equations with piecewise continuous arguments is investigated by using Lyapunov methods. In particular, the linear equations with variable coefficients are considered. The stability conditions of the analytic solutions of those equations and the numerical solutions of the -methods are obtained. Some examples are illustrated.
Simulation for Sludge Flocculation I: Brownian Dynamic Simulation for Perikinetic Flocculation of Charged Particle
Linshuang Liu,Guolu Yang,Minghui Yu
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/527384
Abstract: To investigate sludge drying process, a numerical simulation based on Brownian dynamic for the floc with uncharged and charged particles was conducted. The Langevin equation is used as dynamical equation for tracking each particle in a floc. An initial condition and periodic boundary condition which well conformed to reality is used for calculating the floc growth process. Each cell consists of 1000 primary particles with diameter 0.1 ~ 4 μm. Floc growth is related to the thermal force and the electrostatic force. The electrostatic force on a particle in the simulation cell is considered as the sum of electrostatic forces from other particles in the original cell and its replicate cells. It is assumed that flocs are charged with precharged primary particles in dispersion system by ionization. By the analysis of the simulation figures, on one hand, the effects of initial particle size and sludge density on floc smashing time, floc radius of gyration, and fractal dimension were discussed. On the other hand, the effects of ionization on floc smashing time and floc structure were presented. This study has important practical value in the high-turbidity water treatment, especially for sludge drying.
Synthesis and Evaluation of 2-Amino-4H-Pyran-3-Carbonitrile Derivatives as Antitubercular Agents  [PDF]
Chunxia Chen, Minghui Lu, Zhihui Liu, Junting Wan, Zhengchao Tu, Tianyu Zhang, Ming Yan
Open Journal of Medicinal Chemistry (OJMC) , 2013, DOI: 10.4236/ojmc.2013.34015
Abstract: A series of 2-amino-4H-pyran-3-carbonitrile derivatives were designed and synthesized. Their antitubercular activities
were evaluated against autoluminescent M. tuberculosis H37Ra and standard strain M. tuberculosis H37Rv. No obvious
antitubercular activities could be observed (MIC > 10 ug/mL). The results are in sharp contrast with the previously reported
data.
The Research of Urban Rail Transit Sectional Passenger Flow Prediction Method  [PDF]
Qian Li, Yong Qin, Ziyang Wang, Minghui Zhan, Yu Liu, Zhongxin Zhao, Zhiguo Li
Journal of Intelligent Learning Systems and Applications (JILSA) , 2013, DOI: 10.4236/jilsa.2013.54026
Abstract: This paper studies the short-term prediction methods of sectional passenger flow, and selects BP neural network combined with the characteristics of sectional passenger flow itself. With a case study, we design three different schemes. We use Matlab to realize the prediction of the sectional passenger flow of the Beijing subway Line 2 and make comparative analysis. The empirical research shows that combining data characteristics of sectional passenger flow with the BP neural network have good prediction accuracy.
Effects of Tumor Necrosis Factor-β (TNF-β) 252A>G Polymorphism on the Development of Migraine: A Meta-Analysis
Ruozhuo Liu, Minghui Ma, Mingyu Cui, Zhao Dong, Xiaolin Wang, Wei Zhang, Minghui Yang, Shengyuan Yu
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0100189
Abstract: Background and Objective Genetic factors including TNF-β have been considered as important components in the aetiology of migraine. Many studies have investigated the association between TNF-β 252A>G polymorphism and migraine risk, with debatable results. This study was designed to examine whether the TNF-β 252A>G polymorphism confers genetic susceptibility to migraine in diverse populations. Method Studies eligible for this meta-analysis were searched in the PubMed, Embase, and CNKI by using the keywords “tumor necrosis factor”, “TNF”, “252A>G”, “rs909253”, “polymorphism”, “polymorphisms”, “variant”, “SNP”, combined with “migraine” or “migraine with aura (MA)” or “migraine without aura (MO)”. Pooled ORs and 95% CI were appropriately calculated using the fixed-effect model. Results We finally included a total of seven studies, providing 5 557 migraineurs and 20 543 unrelated healthy controls. Meta-analysis results showed no statistical evidence of a significant association between TNF-β 252A>G polymorphism and overall migraine risk. Stratified analyses by type of migraine and gender revealed similar results. Interestingly, an OR with 95% CI representing an increased migraine risk was indicated in Asians under the recessive model (GG vs. AG + AA: OR, 1.38; 95%CI, 1.04–1.84; P for heterogeneity, 0.665). Conclusions Our findings appear to support the hypothesis that genetic variability of 252A>G polymorphism in TNF region may modulate risk of migraine in the population of Asian ancestry.
Aspects of formation and degradation of polychlorinated dibenzo-p-dioxins and dibenzofurans
Minghui Zheng,Pengyan Liu,Zhicheng Bao,Xiaobai Xu
Chinese Science Bulletin , 1999, DOI: 10.1007/BF02885839
Abstract: The research progress on the mechanisms of formation and degradation of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) is reviewed. The primary sources of PCDD/Fs are chemical, thermal, photochemical and enzymatic reactions. Most of the thermal sources result in emissions into air. The studies on the photodegradation and biodegradation offer promise for destruction of PCDD/Fs in environment.
Distribution of polycyclic aromatic hydrocarbons in sediments from Yellow River Estuary and Yangtze River Estuary, China

HUI Yamei,ZHENG Minghui,LIU Zhengtao,GAO Lirong,

环境科学学报(英文版) , 2009,
Abstract: Surface sediment samples collected from twenty-one sites of Yellow River Estuary and Yangtze River Estuary were determined for sixteen priority polycyclic aromatic hydrocarbons (PAHs) by isotope dilution GC-MS method. The total PAH contents varied from 10.8 to 252 ng/g in Yellow River Estuary sediment, and from 84.6 to 620 ng/g in Yangtze River Estuary sediment. The mean total PAH content of Yangtze River Estuary was approximately twofold higher than that of Yellow River Estuary. The main reasons for the di erence may be the rapid industrial development and high population along Yangtze River and high silt content of Yellow River Estuary. The evaluation of PAH sources suggested that PAHs in two estuaries sediments estuaries were derived primarily from combustion sources, but minor amounts of PAHs were derived from petroleum source in Yellow River Estuary. PAHs may be primary introduced to Yellow River Estuary via dry/wet deposition, wastewater e uents, and accidental oil spills, and Yangtze River Estuary is more prone to be a ected by wastewater discharge.
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