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NUMERICAL STUDIES OF A CLASS OF COMPOSITE PRECONDITIONERS

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Journal of Computational Mathematics 2014年第2期32卷 136-151页

作者： qiang Niu Michael ng Mathematics and Physics Centre Xi'an Jiaotong-Liverpool University Suzhou 215123 China Department of Mathematics Hong Kong Baptist University Kowloon Tong Hong Kong

In this paper, we study a composite preconditioner that combines the modified tangential frequency filtering decomposition with the ILU（O） factorization. Spectral property of the composite preconditioner is examined by the approach of Fourier analysis. We illustrate that condition number of the preconditioned matrix by the composite preconditioner is asymptotically bounded by O（hp -2/3） on a standard model problem. Performance of the composite preconditioner is compared with other preconditioners on several problems arising from the discretization of PDEs with discontinuous coefficients. Numerical results show that performance of the proposed composite preconditioner is superior to other relative preconditioners.

关键词： Preconditioner ILU Tangential frequency filtering decomposition GMRES.

Locating Malleable Bulk Metallic Glasses in Zr-Ti-Cu-Al Alloys with Calorimetric Glass Transition Temperature as an Indicator

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Journal of Materials Science & Technology 2012年第12期28卷 1109-1122页

作者： qiang he Jian Xu jianxu@*** Chinese Acad Sci Shenyang Natl Lab Mat Sci Inst Met Res Shenyang 110016 Peoples R China

We defined the plastic deformability under constrained loading conditions as malleability for bulk metallic glass （BMG） materials. Quaternary Zr-Ti-Cu-Al alloys in the Zr-rich composition range are selected to investigate the compositional dependence of malleability assessed by bending testing and glass transition temperature （Tg ）. As indicated, increasing the Al or Cu concentration in the alloys leads to the rise of T g . The Zr（61）Ti2Cu（25）Al（12）（ZT1） and Zr（61.6）Ti（4.4）Cu（24）Al（10）（ZT3） alloys exhibit an optimal combination of lower T g and higher glass-forming ability. The malleable BMGs such as ZT1 manifests two characters during deformation, the stable propagation of a single shear band indicated by large shear offsets and easy proliferation of shear bands. With increasing the T g of BMG, the yield strength σy,young＇s modulus and shear modulus simultaneously increase as well, while the Poisson s ratio decreases. The σy of ZT1 BMG is about 1680 MPa in compression and 1600 MPa in tension. In tensile loading, no any visible plasticity appears even when the strain rate increases up to the order of magnitude of 10（-1）s（-1）. In consistent with the T g , malleability of Zr-Ti-Cu-Al BMGs manifests significant compositional dependence. The malleable BMG is associated with lower Tg , as well as lower shear modulus or higher Poisson s ratio, which can be understood on the basis of the correlation of Tg with shear energy barrier in metallic glass. Thus, the calorimetric Tg can be used as an indicator to screen malleable BMG-forming composition, with advantage of experimental accessibility.

关键词： Metallic glass Glass transition Malleability Bending Elastic constants

Low-rank matrix recovery with total generalized variation for defending adversarial examples

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Frontiers of Information Technology & Electronic Engineering 2024年第3期25卷 432-445页

作者： Wen LI hengyou WAng Lianzhi HUO qiang he Linlin CheN Zhiquan he Wing W.y.ng School of Science Beijing University of Civil Engineering and ArchitectureBeijing 100044China School of Computer Science and Engineering South China University of TechnologyGuangzhou 510006China Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China Guangdong Key Laboratory of Intelligent Information Processing Shenzhen 518060China Institute of Big Data Modeling and Technology Beijing University of Civil Engineering and ArchitectureBeijing 100044China

Low-rank matrix decomposition with first-order total variation(TV)regularization exhibits excellent performance in exploration of image *** advantage of its excellent performance in image denoising,we apply it to improve the robustness of deep neural ***,although TV regularization can improve the robustness of the model,it reduces the accuracy of normal samples due to its *** our work,we develop a new low-rank matrix recovery model,called LRTGV,which incorporates total generalized variation(TGV)regularization into the reweighted low-rank matrix recovery *** the proposed model,TGV is used to better reconstruct texture information without *** reweighted nuclear norm and Li-norm can enhance the global structure ***,the proposed LRTGV can destroy the structure of adversarial noise while re-enhancing the global structure and local texture of the *** solve the challenging optimal model issue,we propose an algorithm based on the alternating direction method of *** results show that the proposed algorithm has a certain defense capability against black-box attacks,and outperforms state-of-the-art low-rank matrix recovery methods in image restoration.

关键词： Total generalized variation Low-rank matrix Alternating direction method of multipliers Adversarial example

Distributing pairs of vertices on Hamiltonian cycles

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Science China Mathematics 2018年第5期61卷 955-972页

作者： Weihua he Hao Li qiang Sun Department of Applied Mathematics Guangdong University of Technology Laboratoire de Recherche en Informatique CNRS-Université Paris-Sud Institute for Interdisciplinary Research Jianghan University School of Mathematical Science Yangzhou University

Let G be a graph of order n with minimum degree δ(G)≥n/2+1. Faudree and Li(2012) conjectured that for any pair of vertices x and y in G and any integer 2≤k≤n/2, there exists a Hamiltonian cycle C such that the distance between x and y on C is k. In this paper, we prove that this conjecture is true for graphs of sufficiently large order. The main tools of our proof are the regularity lemma of Szemer′edi and the blow-up lemma of Koml′os et al.(1997).

关键词： Hamiltonian cycle Faudree-Li conjecture regularity lemma blow-up lemma

A novel molecular mechanism for nitrated α-synuclein-induced cell death

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Journal of Molecular Cell Biology 2011年第4期3卷 239-249页

作者： yany.ng Liu Min qiang yan Wei Rongqiao he State Key Laboratory of Brain and Cognitive Sciences Institute of BiophysicsChinese Academy of Sciences15 Datun RoadChaoyang DistrictBeijing 100101China Key Laboratory of Mental health Institute of PsychologyChinese Academy of Sciences15 Datun RoadChaoyang DistrictBeijing 100101China

Although previous studies have demonstrated the involvement of nitrated a-synuclein in neurodegenerative disorders(synucleinopathies),the effects of nitrated α-synuclein and the molecular mechanisms underly.ng its toxicity are still *** the present study,nitrated α-synuclein with four 3-nitrotyrosines(Tyr^(39),Tyr^(125),Tyr^(133),and Tyr^(136))was obtained non-enzymatically by incubation with *** nitrated protein existed as a mixture of monomers,dimers,and polymers in *** nitrated a-synuclein could induce cell death in a time-and concentration-dependent manner when SH-Sy5y cells(a human neuroblastoma cell line)were incubated with the dimers and *** with anti-integrin α5β1 antibody partially rescued the SH-Sy5y cells from the cell *** blotting and immunoprecipitation revealed that the nitrated protein bound to integrin on the cell *** of nitric oxide(NO)and calcium-independent inducible NO synthase(iNOS)activity increased during the initial stages of the *** expression of phosphorylated focal adhesion kinase(FAK)decreased in the ***,an increase in caspase 3 activity was observed in SH-Sy5y *** results demonstrate that activation of iNOS and inhibition of FAK may both be responsible for the cell death induced by nitrated α-*** data suggest that the cytotoxicity of nitrated a-synuclein is mediated via an integrin-iNOS/-FAK signaling pathway,and that the nitration of α-synuclein plays a role in neuronal degeneration.

关键词： nitric oxide nitration neuronal death toxicity focal adhesion kinase calcium-independent inducible nitric oxide synthase

Analysis of a landfill cover without geomembrane using varied particle sizes of recycled concrete

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第5期15卷 1263-1273页

作者： Charles Wang Wai ng Cheuk Lam ng Junjun Ni Haowen Guo Qi Zhang qiang Xue Rui Chen Department of Civil and Environmental Engineering Hong Kong University of Science and TechnologyHong KongChina School of Transportation Southeast UniversityNanjingChina State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Department of Civil and Environmental Engineering Shenzhen Graduate SchoolHarbin Institute of TechnologyShenzhenChina

Previous studies have demonstrated the effectiveness of a novel three-layer landfill cover system constructed with recycled concrete aggregates(RCAs)without geomembrane in both laboratory and ***,no systematic investigation has been carried out to optimize the combination of the particle sizes for fine-grained RCAs(FRC)and coarse-grained RCAs(CRC)that can be used for the three-layer landfill cover *** aim of this paper is to assist engineers in designing the three-layer landfill cover system under a rainfall of 100-year return period in humid climate conditions using an easily controlled soil parameter D10 of *** numerical study reveals that when D10 of FRC increases from 0.05 mm to 0.16 mm,its saturated permeability increases by 10 *** a result,a larger amount of rainwater infiltrates into the cover system,causing a higher lateral diversion in both the top FRC and middle CRC *** further changes in the lateral diversion are observed when the D10 value of FRC is larger than 0.16 *** the particle sizes of FRC and CRC layers are shown to have a minor influence on the percolation under the extreme rainfall *** implies that the selection of particle sizes for the FRC and CRC layers can be based on the availability of *** it is well known that the bottom layer of the cover system should be constructed with very fine-grained soils if possible,this study provides an upper limit to the particle size that can be used in the bottom layer(D10 not larger than 0.02 mm).With this limit,the three-layer system can still minimize the water percolation to meet the design criterion(30 mm/yr)even under a 100-year return period of rainfall in humid climates.

关键词： Capillary barrier Landfill cover Particle size Recycled concrete

Mapping the Risk of Water Erosion in the Watershed of the Ningxia-Inner Mongolia Reach of the yellow River, China

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Journal of Mountain Science 2015年第1期12卷 70-84页

作者： DU he-qiang XUE Xian WAng Tao Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

Mapping and assessing soil-erosion risk can address the likelihood of occurrence of erosion as well as its consequences. This in turn provides precautionary and relevant suggestions to assist in disaster reduction. Because soil erosion by water in the watershed of the Ningxia-Inner Mongolia reach of the yellow River is closely related to silting of the upper reaches of the yellow River, it is necessary to assess erosion risk in this watershed. This study aims to identify the soil-erosion risk caused by water in the watershed of the Ningxia-Inner Mongolia reach of the yellow River from 2ool to aOlO. Empirical models called Chinese Soil Loss Equation （CSLE） and Modified Universal Soil Loss Equation （MUSLE） were used to predict the erosion modulus in slope surfaces and gullies. Then the soil erosion risk in this watershed was assessed according to the classification criteria of soil erosion intensities （SL19o-2oo7）. The study results showed that the range of values of the erosion modulus in this watershed was o-44,733 t/km2/a. More than 20% of the total watershed area was found to present an erosion risk, with the regions at risk mainly located in channels and their upper reaches, and in mountainous areas. To determine the regression coefficients of the erosion factors with respect to erosion modulus, a GWR （geographically weighted regression） was carried out using the ArcGIS software. It was found that the topographic factor has the highest contribution rate to the soil erosion modulus, while the highest contribution rate of the erosion factors to the erosion modulus and the largest values of the factors were not located in the same places. Based on this result, the authors propose that slope management is the most important task in preventing soil loss in this watershed, and the soil- conservation projects should be built according to the eontribution rate of the erosion factors.

关键词： Chinese Soil Loss Equation (CSLE) Erosion risk Geographically weighted regression(GWR) yellow River

CPFD simulation on particle behaviour in an entrained-flow gasifier

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Clean Energy 2020年第1期4卷 75-84页

作者： y.ngshi Liang Cliff y.Guo Xianglong Zhao qiang Qin yi Cheng Lixin he National Institute of Clean-and-low-carbon Energy Beijing 102211China Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

A computational particle fluid dynamics simulation model for entrained-flow gasification was established in this *** simulation results agree with the experimental *** detailed particle information and residence-time distribution were obtained by injecting particle tracers in the *** results show that the particles in the gasifier can be classified into three flowing zones,i.e.a fast-flowing zone,a recirculation zone and a spreading *** criterion for this classification was also *** rapid gas expansion caused by the fast reactions plays a significant role in forming the particle stream into these three *** accelerates the particles in the centre of the gasifier while pushing the particles near the expansion edge into the gas ***,the concentrated oxygen distribution in the gasifier results in the formation of high-and low-temperature *** particles in the fast-flowing zone flow directly through the high-temperature region and most of these particles in this zone were fully reacted with a short residence *** particles in the recirculation zone are in a relatively low-temperature region,most of these particles are not fully gasified,although with a long residence *** rest of particles in the spreading zone show moderate properties between the above two zones.

关键词： CPFD simulation entrained-flow gasifier particle behaviour gasification process

Development of stable, cold-adapted, temperature-sensitive/conditional lethal chimeric enterovirus A71 and coxsackievirus A16

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Virologica Sinica 2022年第5期37卷 769-773页

作者： Kaw Bing Chua Qimei ng Tao Meng qiang Jia Temasek Life Sciences Laboratory 1 Research LinkNational University of Singapore117604Singapore

Dear Editor,Coxsackievirus A16(CA16)and enterovirus A71(EV-A71)are the main causative agents of hand foot and mouth disease(HFMD)(Alexander et al.,1994).Besides HFMD,EV-A71 infection in young children can lead to a spectrum of other clinical diseases and associated neurological complications and mortality(Melnick JL.,1996).In recent decades,EV-A71 infections have become a major public health concern throughout the world,following the frequent occurrence of epidemics and outbreaks of HFMD associated with neurological complications and high mortality in young children(Ishimaru et al.,1980;Tagaya et al.,1981;Chomnaitree et al.,1982;Samuda et al.,1987;Gilbert et al.,1988;Hayward et al.,1989;Lum et al.,1998;Chang et al.,1998;Liu et al.,2000;y.ng et al.,2011;Zeng et al.,2012).

关键词： mortality enterovirus