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角质层渗透性质的三维数值模拟

航天医学与医学工程 2004年第4期17卷 251-255页

作者：刘宇红 dirk feuchter Gabriel Wittum 张恩平曾衍钧北京工业大学生物力学与医学信息研究所北京100022 Technical Simulation Group of the Interdisciplinary Cen-ter for Scientific Computing of University Heidelberg

目的从数值模拟的角度研究药物渗透皮肤角质层的过程,为实际的药物工作者提供理论上的指导和帮助。方法用有限元方法离散偏微分方程的差分格式,将角质层的角蛋白细胞近似为物理学上经典的由6个四边形和8个六边形围成的三维十四面体结构... 详细信息

目的从数值模拟的角度研究药物渗透皮肤角质层的过程,为实际的药物工作者提供理论上的指导和帮助。方法用有限元方法离散偏微分方程的差分格式,将角质层的角蛋白细胞近似为物理学上经典的由6个四边形和8个六边形围成的三维十四面体结构,同时将角蛋白细胞间的脂质体视为十四面体结构的一部分,离散其相应的单元网格。结果得到了药物渗透皮肤角质层的三维数值模拟,并给出了模拟过程中浓度和速度变化的可视化效果示意图。结论本文所采用的几何模型与实际的生理结构模型非常接近,数值模拟结果证明这一方法对实际工作有参考意义。

关键词：角质层渗透十四面体数值模拟三维模型

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一种多层三维几何结构的网格拆分方法

北京工业大学学报 2006年第4期32卷 370-374页

作者：刘宇红 dirk feuchter Gabriel Wittum 曾衍钧北京工业大学生命科学与生物工程学院北京100022 Technical Simulation Group of the Interdisciplinary Center for Scientific Computing of University Heidelberg HeidelbergGermany

为了采用偏微分方程求解流体的多层复杂几何结构的渗透性质,本文提出了一种多层三维复杂几何结构的网格拆分方法,尤其对多层结构中的核心——1个由6个四边形和8个六边形围成的十四面体(即物理学上经典的Tetrakaidecahedron体)的空间拓... 详细信息

为了采用偏微分方程求解流体的多层复杂几何结构的渗透性质,本文提出了一种多层三维复杂几何结构的网格拆分方法,尤其对多层结构中的核心——1个由6个四边形和8个六边形围成的十四面体(即物理学上经典的Tetrakaidecahedron体)的空间拓扑几何结构进行了详细的分析．在完成单元体向整体结构拼接的过程中,采用一种将单元体视为内外两层的思路,既有效地存贮了网格点的信息,又大大减少计算量．并讨论了影响十四面体几何性质的参数对所生成的网格性质的影响．

关键词：十四面体网格拆分线性格点模型

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角质层渗透性质的有限元数值模拟计算

中国生物医学工程学报 2006年第2期25卷 219-223页

作者：刘宇红 dirk feuchter Gabriel Wittum 张恩平曾衍钧北京工业大学生物力学与医学信息研究所 Technical Simulation Group of the Interdisciplinary Center for Scientific Computing of University Heidelberg Imneuen HeimerFeld36869120HeidelbergGermany

角质层是皮肤屏障作用的最主要部分,它决定可外界物质对皮肤的渗透情况。本研究在假设角质层细胞为一种三维的十四面体(物理学经典的Tetrakaidecahedron体)下,进行对角质层渗透性质的数值模拟工作。为此,首先完成了对角质层空间结构的... 详细信息

角质层是皮肤屏障作用的最主要部分,它决定可外界物质对皮肤的渗透情况。本研究在假设角质层细胞为一种三维的十四面体(物理学经典的Tetrakaidecahedron体)下,进行对角质层渗透性质的数值模拟工作。为此,首先完成了对角质层空间结构的网格拆分,拆分过程分两步进行:首先对角蛋白细胞的网格拆分;然后对角蛋白细胞周围的网状脂质体的网格拆分。在数值模拟过程中,则用有限元法得到方程的离散格式,用多重网格算法降低高频误差,提高计算精度。最后,给出了数值模拟结果的可视化效果图。

关键词：角质层 Tetrakaidecahedron 网格拆分有限元方法

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角质层渗透性质的有限元数值模拟计算

应用数学和力学 2006年第4期27卷 417-423页

作者：刘宇红乔爱科 D.弗西特 G.维图姆曾衍钧北京工业大学生物力学与医学信息研究所北京100022 海德堡大学综合性学科计算中心

角质层是皮肤屏障作用的最主要部分,它决定了外界物质对皮肤的渗透情况.在假设角质层细胞为一种三维的十四面体(物理学经典的tetrakaidecahedron体)的情况下,利用有限元法对角质层渗透性质进行了数值模拟研究.为此,首先完成了对角质层... 详细信息

角质层是皮肤屏障作用的最主要部分,它决定了外界物质对皮肤的渗透情况.在假设角质层细胞为一种三维的十四面体(物理学经典的tetrakaidecahedron体)的情况下,利用有限元法对角质层渗透性质进行了数值模拟研究.为此,首先完成了对角质层空间结构的网格拆分,拆分过程分两步进行:1.对角蛋白细胞的网格拆分;2.对角蛋白细胞周围的网状脂质体的网格拆分.在数值模拟过程中,则用有限元法得到方程离散的格式,用多重网格算法降低高频误差,提高计算精度.最后,给出了数值模拟结果的可视化效果图.

关键词：角质层 tetrakaidecahedron 网格拆分有限元法多重网格算法

Multi-scale simulations of apatite-collagen composites： from molecules to materials

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Frontiers of Materials Science 2017年第1期11卷 1-12页

作者： dirk ZAHN Lehrstuhl for Theoretische Chemie/Computer Chemie Centrum Friedrich-Alexander Universitat Erlangen-Numberg Nagelsbachstraβe25 91052 Erlangen Germany

We review scale-bridging simulation studies for the exploration of atomic- to-meso scale processes that account for the unique structure and mechanic properties of apatite-protein composites. As the atomic structure and composition of such complex biocomposites only partially is known, the first part （i） of our modelling studies is dedicated to realistic crystal nucleation scenarios of inorganic-organic composites. Starting from the association of single ions, recent insights range from the mechanisms of motif formation, ripening reactions and the self-organization of nanocrystals, including their interplay with growth-controlling molecular moieties. On this basis, （ii） reliable building rules for unprejudiced scale-up models can be derived to model bulk materials. This is exemplified for （enamel-like） apatite-protein composites, encompassing up to 106 atom models to provide a realistic account of the 10 nm length scale, whilst model coarsening is used to reach pm length scales. On this basis, a series of deformation and fracture simulation studies were performed and helped to rationalize biocomposite hardness, plasticity, toughness, self-healing and fracture mechanisms. Complementing experimental work, these modelling studies provide particularly detailed insights into the relation of hierarchical composite structure and favorable mechanical properties.

关键词： biocomposites deformation fracture molecular simulation

Structural pavement assessment in Germany

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Frontiers of Structural and Civil Engineering 2018年第2期12卷 183-191页

作者： Lutz PINKOFSKY dirk JANSEN Bundesanstalt fur Straflenwesen (Federal Highway Research Institute) BASt Bruederstrasse 53 51427 Bergisch Gladbach Germany

The aging structure as well as the considerable increase of heavy-traffic load on Germany＇s motorways and trunk roads encourages the use of innovative, sound and reliable methods for the structural assessment on network level as well as on project level. Essential elements for this are data, which allow a reliable assessment. For a holistic approach to structural pavement assessment performance orientated measurements will be necessary. In combination with functional parameters as well as write-down models, strategically motivated decision making processes will be useful combined with technically motivated decision processes. For the application at the network level, the available methods for performance orientated measurements are still challenging, as they are based either on testing drill-cores or on non- traffic speed methods. In recent years significant innovation steps have been made to bring traffic speed bearing capacity measurements and methods for evaluating pavement structures on the road. The paper summarizes the actual assessment procedures in Germany as well as the ongoing work on the development and implementation of new methods and techniques.

关键词： pavement assessment Germany structure system

The role of phosphorus in the metabolism of arsenate by a freshwater green alga, Chlorella vulgaris

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Journal of Environmental Sciences 2016年第11期28卷 169-178页

作者： Josh Baker dirk Wallschlager Trent University Environmental and Life Sciences Graduate Program 1600 West Bank Dr Peterborough ON K9L 0G2 Canada School of the Environment Department of Chemistry and Water Quality Centre Trent University 1600 West Bank Dr Peterborough ONK9L 0G2 Canada

A freshwater microalga, Chlorella vulgaris, was grown in the presence of varying phosphate concentrations（〈 10–500 μg/L P） and environmentally realistic concentrations of arsenate（As（Ⅴ））（5–50 μg/L As）. Arsenic speciation in the culture medium and total cellular arsenic were measured using AEC-ICP-MS and ICP-DRC-MS, respectively, to determine arsenic biotransformation and uptake in the various phosphorus scenarios. At high phosphate concentration in the culture medium, 〉 100 μg/L P, the uptake and biotransformation of As（Ⅴ） was minimal and dimethylarsonate（DMAs（Ⅴ）） was the dominant metabolite excreted by C. vulgaris, albeit at relatively low concentrations. At common environmental P concentrations, 0–50 μg/L P, the uptake and biotransformation of As（Ⅴ） increased. At these higher As-uptake levels, arsenite（As（Ⅲ）） was the predominant metabolite excreted from the cell. The concentrations of As（Ⅲ） in these low P conditions were much higher than the concentrations of methylated arsenicals observed at the various P concentrations studied. The switchover threshold between the（small） methylation and（large） reduction of As（Ⅴ） occurred around a cellular As concentration of 1 fg/cell. The observed nearly quantitative conversion of As（Ⅴ） to As（Ⅲ） under low phosphate conditions indicates the importance of As（Ⅴ） bio-reduction at common freshwater P concentrations. These findings on the influence of phosphorus on arsenic uptake, accumulation and excretion are discussed in relation to previously published research. The impact that the two scenarios of As（Ⅴ） metabolism, As（Ⅲ） excretion at high As（Ⅴ）-uptake and methylarsenical excretion at low As（Ⅴ）-uptake, have on freshwater arsenic speciation is discussed.

关键词： Arsenic Speciation Phosphorus Freshwater algae Toxicity Biotransformation

Numerical modelling of a turbulent bluff-body flow with Reynolds stress turbulent models

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Progress in Natural Science:Materials International 2005年第5期15卷 458-462页

作者： dirk ROEKAERTS CJ2628 Delft Delft University of Technology Department of Applied Physics The Netherlands

Numerical modelling of a turbulent bluff-body flow has been performed using differential Reynolds stress models (DRSMs). To clarify the applicability of the existing DRSMs in this complex flow, several typical DRSMs, including LRR-IP model, JM model, SSG model, as well as a modified LRR-IP model, have been validated and evaluated. The performance difference between various DRSMs is quite significant. Most of the above mentioned DRSMs cannot provide overall satisfactory predictions for this challenging test case. Motivated by the deficiency of the existing approaches, a new modification of LRR-IP model has been proposed. A very significant improvement of the prediction of flow field is obtained.

关键词： bluff-body flow differential Reynolds stress models turbulent model.

Phosphorus release from vivianite and hydroxyapatite by organic and inorganic compounds

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Pedosphere 2020年第2期30卷 190-200页

作者： Stella GYPSER dirk FREESE Brandenburg University of Technology Cottbus-Senftenberg Faculty of EnvironmentProcess EngineeringBiotechnology and ChemistryDepartment of Soil Protection and RecultivationKonrad-Wachsmann-Allee 6Cottbus 03046Germany

Based on recent mining rates and the exhaustion of global phosphorus(P)reserves,there is a need to mobilize P already stored in soils,and its recovery from secondary resources such as Ca-and Fe-phosphates is *** Ca-phosphate hydroxyapatite forms a good fertilizer source,while vivianite is formed in waterlogged soils and *** sludge treatment,the formation of vivianite has been identified,being mainly ***-term P release from both hydroxyapatite and vivianite was studied using different inorganic(CaCl2 and CaSO4)and organic(citric and humic acid)reagents during batch *** CaCl2 and CaSO4 represent the soil solution,while citric and humic acids as organic constituents affect P availability in the rhizosphere and during the process of ***,the flow-through reactor(FTR)technique with an infinite sink was used to study the long-term P release *** cumulative P release was higher by organic acids than by inorganic *** cumulative P release rates were higher in the FTR with CaCl2 as compared to the batch *** infinite sink application caused a continuously high concentration gradient between the solid and liquid phases,leading to higher desorption rates as compared to the batch *** predominant amount of the total P released over time was available for a short *** inorganic anion exchange occurred at easily available binding sites,organic acids affected the more heavily available binding sites,which could be embedded within the mineral *** results showed that organic compounds,especially citric acid,play a superior role as compared to the inorganic constituents of the soil solution during the recovery of already stored P from the tertiary phosphates vivianite and hydroxyapatite.

关键词： anion exchange batch technique citric acid flow-through reactor humic acid ligand exchange phosphate phosphorus recovery