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Condition-based maintenance policy for gamma deteriorating systems

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Journal of Systems Engineering and Electronics 2010年第1期21卷 57-61页

作者： Lin tan zhijun Cheng Bo Guo Shiyu Gong School of Information System and Management National University of Defense Technology Changsha 410073 E R. China

A condition-based maintenance model for gamma deteriorating system under continuous inspection is studied. This methodology uses a gamma distribution to model the material degradation, and the impact of imperfect maintenance actions on the system reliability is investigated. The state of a degrading system immediately after the imperfect maintenance action is assumed as a random variable and the maintenance time follows a geometric process. Furthermore, the explicit expressions for the long-run average cost and availability per unit time of the system are evaluated, an optimal policy （ε^＊） could be determined numeri- cally or analytically according to the optimization model. At last, a numerical example for a degrading system modeled by a gamma process is presented to demonstrate the use of this policy in practical applications.

关键词： condition-based maintenance gamma process imperfect maintenance deteriorating system geometrical process.

Hydrodynamic Interaction of Elastic Capsules in Bounded Shear Flow

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Communications in Computational Physics 2014年第9期16卷 1031-1055页

作者： D.V.Le zhijun tan Institute of High Performance Computing Agency for ScienceTechnology and Research1 Fusionopolis Way#16-16 ConnexisSingapore 138632 School of Mathematics and Computational Science Sun Yat-sen UniversityGuangzhou 510275China Province Key Laboratory of Computational Science Sun Yat-sen UniversityGuangzhou 510275China.

This paper presents a modified Loop’s subdivision algorithm for studying the deformation of a single capsule,the hydrodynamic interaction between two capsules and the hydrodynamic diffusion of a suspension of capsules in bounded shear flow.A subdivision thin-shell model is employed to compute the forces generated on the surface of the elastic capsule during *** capsule surface is approximated using the modified Loop’s subdivision scheme which guarantees bounded curvature and C1 continuity everywhere on the limit *** present numerical technique has been validated by studying the deformation of a spherical capsule in shear *** are also performed for a biconcave capsule over a wide range of shear rates and viscosity ratios to investigate its *** addition,the hydrodynamic interaction between two elastic capsules in bounded shear flow is *** on the wall separation distance,the trajectory-bifurcation points that separate reversing and crossing motions for both spherical and biconcave capsules can be *** to the spherical capsules,the biconcave capsules exhibit additional types of interaction such as rotation and head-on *** head-on collision results in a large trajectory shift which contribute to the hydrodynamic diffusion of a suspension.A suspension of a large number of biconcave capsules in shear flow is also simulated to show the ability of the modified scheme in running a large-scale simulation over a long period of time.

关键词： Thin shell elastic capsules red-blood cells subdivision surfaces immersed boundary method Navier-Stokes equations.

First observation of domoic acid and its isomers in shellfish samples from Shandong Province,China

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Journal of Oceanology and Limnology 2022年第6期40卷 2231-2241页

作者： Guanchao ZHENG Haiyan WU Mengmeng GUO Jixing PENG Yuxiu ZHAI zhijun tan Key Laboratory of Testing and Evaluation for Aquatic Product Safety and Quality Ministry of Agriculture and Rural Aff airsYellow Sea Fisheries Research InstituteChinese Academy of Fishery SciencesQingdao 266071China Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao 266237China Collaborative Innovation Center of Seafood Deep Processing Dalian Polytechnic UniversityDalian 116034China

A total of 133 shellfish samples were collected in seven cities of Shandong Province,China,from May to October,*** domoic acid(DA)concentrations were determined by liquid chromatographytandem mass spectrometry(LC-MS/MS),and their distribution characteristics were *** concentration was detected high in over 1/3(36.1%)of the samples of four kinds of shellfish in all three seasons in range from 0 to 102μg/*** highest DA concentrations were 102,101,36.7,and 10.2μg/kg in Crassostrea gigas,Chlamys farreri,Mactra veneriformis,and Mytilus edulis,***,Yantai(22.0μg/kg)and Weihai(16.9μg/kg)showed relatively high concentrations of DA,whereas Rizhao and Dongying presented only 0.85-and 1.76-μg/kg DA,*** concentrations in the shellfish samples were strongly related to seasonal changes,being significantly higher in autumn and summer than that in *** DA risk exposure assessments indicate that dietary seafood consumption did not pose a health threat to general human *** addition,three isomers(isoA,isoD,isoE)and 5′-epimer DA were detected in 3.00%-15.80%of the shellfish *** study is the first to observe DA and its isomers in shellfish samples of Shandong *** results demonstrate that DA contamination is very common and should be continuously monitored.

关键词： domoic acid shellfi sh liquid chromatography-tandem mass spectrometry(LC-MS/MS) Shandong Province

Thermal processing induced release and degradation of paralytic shellfish toxin from mussels Mytilus edulis

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Journal of Oceanology and Limnology 2022年第6期40卷 2267-2276页

作者： Chenfan DONG Haiyan WU Jixing PENG Mengmeng GUO Yuxiu ZHAI zhijun tan College of Food Science and Technology Shanghai Ocean UniversityShanghai 201306China Key Laboratory of Testing and Evaluation for Aquatic Product Safety and Quality Ministry of AgricultureYellow Sea Fisheries Research InstituteChinese Academy of Fishery SciencesQingdao 266071China Pilot National Laboratory for Marine Science and Technology(Qingdao) Qingdao 266237China Collaborative Innovation Center of Seafood Deep Processing Dalian Polytechnic UniversityDalian 116034China

Understanding the risk factors associated with shellfish consumption is a relevant public health concern because of the potential adverse ef fects of paralytic shellfish toxins(PSTs).This work aims to study the effects of the five most common heating treatments(steaming,boiling,frying,water-bath heating,and microwaving),for different processing times and temperature/power settings,on the content of PSTs in mussels(Mytilus edulis)collected in Qinhuangdao,*** toxin concentration,removal percentages,and toxin distribution in the cooking liquor and meat were *** five processing modes effectively accelerated toxin release into the cooking *** average percentage removal was 73.53%±16.50%from *** led to the most significant toxin degradation among the methods *** findings should facilitate risk assessment of PSTs in mussels.

关键词： processing mode mussels removal percentage toxin distribution

液相色谱-串联质谱法在双壳贝类麻痹性贝毒检测中的应用及影响因素研究进展

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食品科学 2025年第1期46卷 218-226页

作者：邓宇翔吴海燕徐希震赵辉辉谭志军郑关超中国水产科学研究院黄海水产研究所农业农村部水产品质量安全检测与评价重点实验室山东青岛266071 上海海洋大学食品学院上海201306 中国水产科学研究院黄海水产研究所海水养殖生物育种与可持续产出全国重点实验室山东青岛266071

麻痹性贝毒(paralytic shellfish poison,PSP)是危害最大、分布最广的海洋生物毒素,给人类健康、渔业经济及海洋环境带来巨大威胁。双壳贝类是消费者摄入PSP的主要来源,随着PSP中毒事件频发,全球对双壳贝类中PSP检测技术的要求越来越高... 详细信息

麻痹性贝毒(paralytic shellfish poison,PSP)是危害最大、分布最广的海洋生物毒素,给人类健康、渔业经济及海洋环境带来巨大威胁。双壳贝类是消费者摄入PSP的主要来源,随着PSP中毒事件频发,全球对双壳贝类中PSP检测技术的要求越来越高。本文首先介绍PSP理化性质,其次从前处理提取净化、仪器条件、基质效应、方法验证方面对液相色谱-串联质谱(liquid chromatography-tandem mass spectrometry,LC-MS/MS)法在双壳贝类中PSP检测中的优劣势进行总结,经对比分析发现,目前1%乙酸已成为LC-MS/MS检测技术中最常用的PSP提取试剂,石墨化炭黑填料和亲水相互作用液相色谱分别更适用于净化、分离双壳贝类中PSP提取物,影响基质效应的因素主要为内源性干扰如磷脂、蛋白质等,外源性干扰如检测方法中有机物和聚合物残留等杂质。本文重点分析LC-MS/MS研究发展趋势,以期为双壳贝类中PSP的检测提供参考,也为贝类养殖产业绿色发展及政府监管提供技术支持。

关键词：麻痹性贝毒双壳贝类液相色谱-串联质谱法影响因素

AnAdaptive Moving Mesh Method for Two-Dimensional Incompressible Viscous Flows

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Communications in Computational Physics 2008年第3期3卷 679-703页

作者： zhijun tan K.M.Lim B.C.Khoo Singapore-MIT Alliance 4 Engineering Drive 3National University of SingaporeSingapore 117576Singapore Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore.

In this paper, we present an adaptive moving mesh technique for solvingthe incompressible viscous flows using the vorticity stream-function formulation. Themoving mesh strategy is based on the approach proposed by Li et al. [J. Comput. Phys.,170 (2001), pp. 562–588] to separate the mesh-moving and evolving PDE at each timestep. The Navier-Stokes equations are solved in the vorticity stream-function form bya finite-volume method in space, and the mesh-moving part is realized by solving theEuler-Lagrange equations to minimize a certain variation in conjunction with a moresophisticated monitor function. A conservative interpolation is used to redistributethe numerical solutions on the new meshes. This paper discusses the implementationof the periodic boundary conditions, where the physical domain is allowed to deformwith time while the computational domain remains fixed and regular throughout. Numericalresults demonstrate the accuracy and effectiveness of the proposed algorithm.

关键词： Moving mesh method finite volume method Navier-Stokes equations vorticity stream-function incompressible flow.

An Implementation ofMAC Grid-Based IIM-Stokes Solver for Incompressible Two-Phase Flows

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Communications in Computational Physics 2011年第10期10卷 1333-1362页

作者： zhijun tan K.M.Lim B.C.Khoo Guangdong Province Key Laboratory of Computational Science and School of Mathematics and Computational Science Sun Yat-sen UniversityGuangzhou 510275China Singapore-MIT Alliance 4 Engineering Drive 3National University of SingaporeSingapore 117576Singapore Department ofMechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore

*** this paper,a novel implementation of immersed interface method combined with Stokes solver on a MAC staggered grid for solving the steady two-fluid Stokes equations with *** velocity components along the interface are introduced as two augmented variables and the resulting augmented equation is then solved by the GMRES *** augmented variables and/or the forces are related to the jumps in pressure and the jumps in the derivatives of both pressure and velocity,and are interpolated using cubic splines and are then applied to the fluid through the jump *** Stokes equations are discretized on a staggered Cartesian grid via a second order finite difference method and solved by the conjugate gradient *** numerical results show that the overall scheme is second order *** major advantages of the present IIM-Stokes solver are the efficiency and flexibility in terms of types of fluid flow and different boundary *** proposed method avoids solution of the pressure Poisson equation,and comparisons are made to show the advantages of time savings by the present *** generalized two-phase Stokes solver with correction terms has also been applied to incompressible two-phase Navier-Stokes flow.

关键词： Incompressible two-phase Stokes equations two-phaseNavier-Stokes equations discontinuous viscosity singular force immersed interface method Uzawa method front tracking method.

Toxic Dinoflagellate Alexandrium tamarense Induces Oxidative Stress and Apoptosis in Hepatopancreas of Shrimp(Fenneropenaeus chinensis)

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Journal of Ocean University of China 2014年第6期13卷 1005-1011页

作者： LIANG Zhongxiu LI Jian LI Jitao tan zhijun REN Hai ZHAO Fazhen College of Fisheries and Life Science Shanghai Ocean University Key Laboratory of Sustainable Development of Marine Fisheries of Ministry of Agriculture Yellow Sea Fisheries Research Institute Chinese Academy of Fishery Sciences

This study investigated the inductive effect ofAlexandrium tamarense, a toxic dinoflagellate producing paralytic shell- fish poison, on oxidative stress and apoptosis in hepatopancreas of Chinese shrimp, Fenneropenaeus chinensis. The individuals of E chinensis were exposed to 200 and 1000 cells mL-1 of A. tamarense with their superoxide dismutase （SOD）, glutathione S-transferase （GST） activities, malonyldialdehyde （MDA） concentration, and caspase gene （FcCasp） expression in hepatopancreas determined at 12, 24, 48, 72 and 96 h. In addition, apoptosis in hepatopancreas of E chinensis at 96 h after exposure was determined through terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling （TUNEL） assay. The hepatopancreatic SOD and GST activities of F. chinensis exposed to 1000 cells mL-1 ofA. tamarense showed a bell-shaped response to exposure time. The hepatopancreatic MDA concentration ofF. chinensis exposed to 1000 cellsmL-1 ofA. tamarense increased gradually from 48 to 96h, and such a trend corresponded to the decrease of GST activity. The hepatopancreatic FcCasp transcript abundance of F. chinensis exposed to 1000 cells mL-1 ofA. tamarense was positively and linearly correlated to MDA concentration. Results of TUNEL assay showed that exposure to 1000 cells mL-1 of A. tamarense induced apoptosis in the hepatopancreas of E chinensis. Our study revealed that A. tamarense exposure influenced the antioxidative status ofF. chinensis and caused lipid peroxidation and apoptosis in the hepatopancreas of shrimp.

关键词： Alexandrium tamarense oxidative stress apoptosis Fenneropenaeus chinensis

An Indirect-Forcing Immersed Boundary Method for Incompressible Viscous Flows with Interfaces on Irregular Domains

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Communications in Computational Physics 2009年第10期6卷 997-1021页

作者： zhijun tan K.M.Lim B.C.Khoo Desheng Wang Singapore-MIT Alliance 4 Engineering Drive 3National University of SingaporeSingapore 117576Singapore Department of Mechanical Engineering National University of Singapore10 Kent Ridge CrescentSingapore 119260Singapore Division of Mathematical Sciences School of Physical and Mathematical SciencesNanyang Technological UniversitySingapore 637371Singapore

An indirect-forcing immersed boundary method for solving the incompressible Navier-Stokes equations involving the interfaces and irregular domains is *** rigid boundaries and interfaces are represented by a number of Lagrangian control *** rigid boundaries are embedded in the Cartesian grid and singular forces at the rigid boundaries are applied to impose the prescribed velocity *** singular forces at the interfaces and the rigid boundaries are then distributed to the nearby Cartesian grid points using the immersed boundary *** the present work,the singular forces at the rigid boundaries are computed implicitly by solving a small system of equations at each time step to ensure that the prescribed velocity condition at the rigid boundary is satisfied *** deformable interfaces,the forces that the interface exerts on the fluid are computed from the configuration of the elastic interface and are applied to the *** Navier-Stokes equations are discretized using finite difference method on a staggered uniform Cartesian grid by a second order accurate projection *** ability of the method to simulate viscous flows with interfaces on irregular domains is demonstrated by applying to the rotational flow problem,the relaxation of an elastic membrane and flow in a constriction with an immersed elastic membrane.

关键词： Incompressible Navier-Stokes equation fast Poisson solvers immersed boundary method projection method Cartesian grid irregular domain finite difference methods