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10th South African Conference on computational and applied Mechanics, SACAM 2016

作者： Bogaers, A.E.J. Kok, S. Reddy, B.D. Franz, T. Advanced Mathematical Modelling Modelling and Digital Sciences CSIR South Africa Department of Mechanical and Aeronautical Engineering University of Pretoria South Africa Department of Mathematics and Applied Mathematics University of Cape Town South Africa Centre for Research in Computational and Applied Mechanics University of Cape Town South Africa Division of Biomedical Engineering Department of Human Biology University of Cape Town South Africa Research Office University of Cape Town South Africa

ISBN: (纸本)9781868226733

In this paper we outline the use of radial basis function interpolation (RBF) to transfer information across non-matching and nonconforming interface meshes, with particular focus to partitioned fluid-structure interactions (FSI). In general, transferring information across a non-matching interface presents itself as a nontrivial problem. RBF interpolation, which requires no global connectivity information, provides an elegant means by which to negate any geometric discrepancies along the interface. The aim is to investigate the feasibility of RBF interpolation, with a strong focus on a comparison between a conservative and consistent formulation.

关键词： Interpolation

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Glycemic Control Indices and Their Aggregation in the Prediction of Nocturnal Hypoglycemia from Intermittent Blood Glucose Measurements

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Journal of Diabetes Science and Technology 2016年第6期10卷 1245-1250页

作者： Sampath, Sivananthan Tkachenko, Pavlo Renard, Eric Pereverzev, Sergei V. Department of Mathematics Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India Johann Radon Institute for Computational and Applied Mathematics (RICAM) Austrian Academy of Sciences Linz Wien Austria Department of Endocrinology Diabetes Nutrition CIC INSERM 1411 Montpellier University Hospital Montpellier France Institute of Functional Genomics UMR CNRS 5203/INSERM U1191 University of Montpellier Montpellier France

Background: Despite the risk associated with nocturnal hypoglycemia (NH) there are only a few methods aiming at the prediction of such events based on intermittent blood glucose monitoring data. One of the first methods that potentially can be used for NH prediction is based on the low blood glucose index (LBGI) and suggested, for example, in Accu-Chek® Connect as a hypoglycemia risk indicator. On the other hand, nowadays there are other glucose control indices (GCI), which could be used for NH prediction in the same spirit as LBGI. In the present study we propose a general approach of combining NH predictors constructed from different GCI. Methods: The approach is based on a recently developed strategy for aggregating ranking algorithms in machine learning. NH predictors have been calibrated and tested on data extracted from clinical trials, performed in EU FP7-funded project DIAdvisor. Then, to show a portability of the method we have tested it on another dataset that was received from EU Horizon 2020-funded project AMMODIT. Results: We exemplify the proposed approach by aggregating NH predictors that have been constructed based on 4 GCI associated with hypoglycemia. Even though these predictors have been preliminary optimized to exhibit better performance on the considered dataset, our aggregation approach allows a further performance improvement. On the dataset, where a portability of the proposed approach has been demonstrated, the aggregating predictor has exhibited the following performance: sensitivity 77%, specificity 83.4%, positive predictive value 80.2%, negative predictive value 80.6%, which is higher than conventionally considered as acceptable. Conclusion: The proposed approach shows potential to be used in telemedicine systems for NH prediction. © Diabetes Technology Society.

关键词： aggregation prediction from glycemic control indices prediction of nocturnal hypoglycemia type 1 diabetes

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Transient growth in Poiseuille-Rayleigh-Bénard flows of binary fluids with Soret effect

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applied mathematics and Mechanics(English Edition) 2016年第9期37卷 1203-1218页

作者： Jun HU D.HENRY H.BENHADID Xieyuan YIN Institute of Applied Physics and Computational Mathematics Beijing 100088China Laboratoire de Mecanique des Fluides et d'Acoustique CNRS/Universitd de LyonEcole Centrale de Lyon/universite Lyon 1/INSA de LyonECL36 avenue Guy de Collongue69134 Ecully CedexFrance Department of Modern Mechanics University of Science and Technology of ChinaHefei 230027China

The transient growth due to non-normMity is investigated for the Poiseuille- Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = -0.1, it is found that a large transient growth can be obtained by the non-normal interaction of the two least-stable-modes, i.e., the upstream and downstream modes, which determine the linear critical boundary curves for small Reynolds numbers. The transient growth is so strong that the optimal energy amplification factor G（t） is up to 10^2 - 10^3. While for positive separation factors such as ψ = 0.1, the transient growth is weak with the order O（I） of the amplification factor, which can even be computed by the least-stable-mode. However, for both cases, the least-stable-mode can govern the long-term behavior of the amplification factor for large time. The results also show that large Reynolds numbers have stabilization effects for the maximum amplification within moderate wave number regions. Meanwhile, much small negative or large positive separation factors and large Rayleigh numbers can enlarge the maximum transient growth of the pure streamwise disturbance with the wavenumber α= 3.14. Moreover, the initial and evolutionary two-dimensional spatial patterns of the large transient growth for the pure streamwise disturbance are exhibited with a plot of the velocity vector, spanwise vorticity, temperature, and concentration field. The initial three-layer cell vorticity struc- ture is revealed. When the amplification factor reaches the maximum Gmax, it develops into one cell structure with large amplification for the vorticity strength.

关键词： binary fluid Soret effect transient growth Poiseuille-Rayleigh-Benard flow

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Alternate double single track proposals for low demand high-speed railway lines

Alternate double single track proposals for low demand high-...

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作者： Castillo, E. Grande, Z. Moraga, P. Nogal, M. O'Connor, A.J. Royal Academy of Engineering Spain Department of Applied Mathematics and Computational Sciences University of Cantabria Santander Spain Pontificia Universidad Católica de Valparaíso Chile Trinity College Dublin Ireland

Multiple track lines are the only satisfactory solution for high speed railway lines when demand is high. However, in several countries double track high speed lines are being built for low demand lines, which are very expensive and inadequate solutions. This paper presents alternate double-single-track (ADST) lines as an alternative to doubletrack lines. The idea consists of using single-track where the infrastructure is very expensive (tunnels and viaducts) and double-track where it is cheaper (smooth orography) combined with small changes in departure times so that trains may cross in the double-track segments with no reduction in travel times. The solution is shown to be very efficient for intermediate traffic demands and the construction and maintenance costs are substantially reduced (close to 40%). A linear programming program is given that (1) decides the optimal sequence of single and double-tracks to be constructed and (2) optimizes the timetables for a given demand. The method can also be applied to combine high speed tracks with conventional existing tracks, where the conventional ones are used mainly for train crossing and circulation of slow and freight trains. These solutions produce very important savings (close to 90%) with very reasonable travel times. The lines Palencia-Santander in Spain, the Santiago-Valparaíso-Viña del Mar in Chile and the Dublin-Belfast in Ireland are used to illustrate both proposals and to demonstrate that they are very interesting alternatives in some practical cases. © Civil-Comp Press, 2016.

关键词： Travel time

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computational study to determine redox potential of nitroxide radical and their derivatives compounds along with their analysis as redox-coupe in dye sensitized solar cell’s (DSSC)

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AIP Conference Proceedings 2018年第1期2049卷

作者： Zahra R. Puteri Yuly Kusumawati Athar L. Ivansyah Muhamad A. Martoprawiro 1Chemistry Department Faculty of Natural Sciences Institut Tehnologi Sepuluh Nopember (ITS) ITS Campus Sukolilo Surabaya East Java 60111 Indonesia 2Master Program in Computational Science Faculty of Mathematics and Natural Science Institut Tehnologi Bandung (ITB) Jl. Ganesha 10 Bandung West Java 401232 Indonesia 3Department Chemistry Faculty of Mathematics and Natural Science Institut Tehnologi Bandung Jl. Ganesha 10 Bandung West Java 401232 Indonesia

The determination of redox potential (E°) was performed by computational study with variation of correlation-function B3LYP, CAM-B3LYP and ωb97-XD for pipiridine, azaadamantane and azaphenalene of nitroxide radical compounds with DFT method. The basis set of 6-13G(d) was used for geometry optimization and frequency calculation. The results showed that the calculation of redox potential with CAM-B3LYP method has the smallest error that is 1.191%. 4-hydroxy TEMPO compound with E° of 0.754 V (vs NHE) is promising to be used as a redox couple on DSSC’s application due to Voc, ΔEregeneration and RCT value consideration.

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Comparative study of some numerical methods to solve a 3D advection-diffusion equation

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AIP Conference Proceedings 2017年第1期1863卷

作者： A. R. Appadu J. K. Djoko H. H. Gidey 1Department of Mathematics and Applied Mathematics University of Pretoria Pretoria 0002 South Africa 2Department of Computational Sciences Aksum University Aksum 1010 Tigray Ethiopia

In this work, three finite difference methods have been used to solve a three dimensional advection-diffusion equation with given initial and boundary conditions. The three methods are fourth order finite difference method, Crank-Nicolson and Implicit Chapeau Function. We compare the performance of the methods by computing L2 error, L∞ error and some performance indices such as mass distribution ratio (MDR), mass conservation ratio (MCR), total mass and R2 which is a measure of total variation in particle distribution.

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Extremely Large Magnetoresistance in a Topological Semimetal Candidate Pyrite PtBi2

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Physical Review Letters 2017年第25期118卷 256601-256601页

作者： Wenshuai Gao Ningning Hao Fa-Wei Zheng Wei Ning Min Wu Xiangde Zhu Guolin Zheng Jinglei Zhang Jianwei Lu Hongwei Zhang Chuanying Xi Jiyong Yang Haifeng Du Ping Zhang Yuheng Zhang Mingliang Tian Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field Laboratory Chinese Academy of Sciences Hefei 230031 Anhui People’s Republic of China. Department of Physics University of Science and Technology of China Hefei 230026 People’s Republic of China Institute of Applied Physics and Computational Mathematics Beijing 100088 People’s Republic of China Beijing Computational Science Research Center Beijing 100193 People’s Republic of China Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 People’s Republic of China

While pyrite-type PtBi2 with a face-centered cubic structure has been predicted to be a three-dimensional (3D) Dirac semimetal, experimental study of its physical properties remains absent. Here we report the angular-dependent magnetoresistance measurements of a PtBi2 single crystal under high magnetic fields. We observed extremely large unsaturated magnetoresistance (XMR) up to (11.2×106)% at T=1.8 K in a magnetic field of 33 T, which is comparable to the previously reported Dirac materials, such as WTe2, LaSb, and NbP. The crystals exhibit an ultrahigh mobility and significant Shubnikov–de Hass quantum oscillations with a nontrivial Berry phase. The analysis of Hall resistivity indicates that the XMR can be ascribed to the nearly compensated electron and hole. Our experimental results associated with the ab initio calculations suggest that pyrite PtBi2 is a topological semimetal candidate that might provide a platform for exploring topological materials with XMR in noble metal alloys.

关键词： Fermi surface Magnetotransport Semimetals Single crystal materials Topological materials Shubnikov-de Haas effect

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Corrigendum to “A stable and conservative interface treatment of arbitrary spatial accuracy” [J. Comput. Phys. 148 (1999) 341–365]

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Journal of computational Physics 2017年 351卷 534-534页

作者： Mark H. Carpenter Jan Nordström David Gottlieb Computational Aerosciences Branch NASA Langley Research Center Hampton VA 23681 USA Department of Mathematics Computational Mathematics Linköping University SE-581 83 Linköping Sweden Division of Applied Mathematics Brown University Providence RI 02912 USA

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Quantum interference in laser-induced nonsequential double ionization

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Physical Review A 2017年第3期96卷 032511-032511页

作者： Wei Quan XiaoLei Hao YanLan Wang YongJu Chen ShaoGang Yu SongPo Xu ZhiLei Xiao RenPing Sun XuanYang Lai ShiLin Hu MingQing Liu Zheng Shu XiaoDong Wang WeiDong Li Wilhelm Becker XiaoJun Liu Jing Chen State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics and Center for Cold Atom Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan 430071 China Institute of Theoretical Physics and Department of Physics Shanxi University 030006 Taiyuan China School of Physics University of Chinese Academy of Sciences Beijing 100080 China HEDPS Center for Applied Physics and Technology Beijing 100084 China Institute of Applied Physics and Computational Mathematics P.O. Box 8009 Beijing 100088 China College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China Max-Born-Institut Max-Born-Strasse 2a 12489 Berlin Germany National Research Nuclear University MEPhI Kashirskoe Shosse 31 115409 Moscow Russia

Quantum interference plays an important role in various intense-laser-driven atomic phenomena, e.g., above-threshold ionization and high-order-harmonic generation, and provides a useful tool in ultrafast imaging of atomic and molecular structure and dynamics. However, it has eluded observation in nonsequential double ionization (NSDI), which serves as an ideal prototype to study electron-electron correlation. Thus far, NSDI usually could be well understood from a semiclassical perspective, where all quantum aspects have been ignored after the first electron has tunneled. Here we perform coincidence measurements for NSDI of xenon subject to laser pulses at 2400 nm. It is found that the intensity dependence of the asymmetry parameter between the yields in the second and fourth quadrants and those in the first and third quadrants of the electron-momentum-correlation distributions exhibits a peculiar fast oscillatory structure, which is beyond the scope of the semiclassical picture. Our theoretical analysis indicates that this oscillation can be attributed to interference between the contributions of different excited states in the recollision-excitation-with-subsequent-ionization channel. Our work demonstrates the significant role of quantum interference in NSDI and may create an additional pathway towards manipulation and imaging of the ultrafast atomic and molecular dynamics in intense laser fields.

关键词： Multiphoton or tunneling ionization & excitation Atomic & molecular beams Atoms Femtosecond laser spectroscopy Semiclassical methods Strong-field approximation

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Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas

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Physical Review A 2017年第3期96卷 032707-032707页

作者： Jun Li Song Bin Zhang Bang Jiao Ye Jian Guo Wang R. K. Janev State Key Laboratory of Particle Detection and Electronics Department of Modern Physics University of Science and Technology of China 230026 Hefei People's Republic of China School of Physics and Information Technology Shaanxi Normal University 710119 Xi'an China Institute of Applied Physics and Computational Mathematics P.O. Box 8009 Beijing 100088 China Macedonian Academy of Sciences and Arts P.O. Box 428 1000 Skopje Macedonia

Low-energy electron elastic scattering and impact ionization with hydrogenlike helium in Debye plasmas have been investigated by employing the exterior complex scaling method. The interactions between charged particles in the plasmas have been represented by Debye-Hückel potentials. The 1s−1s elastic collision strengths below the n=2 excitation threshold of He+ dominated by resonance structures are calculated for different screening lengths. As the screening strength increases, the resonance peaks studied [2(1,0)2+1Se,3Po,1De, and 2(0,1)2+1Po] exhibit blueshifts and then redshifts with a further increase of the screening strength, which results in dramatic changes of the collision strengths. It is found that these dynamic variation features of the resonances are related to the changes of energy levels of He+ in the screened potential and geometric configurations of resonances. Triple-differential-ionization cross sections in coplanar geometries at 6-Ry incident electron energy are also reported, significant changes are observed with varying screening length.

关键词： Electron & positron scattering

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