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- [41] Two-point statistics of statistically self-similar cascadesComptes Rendus De L'Academie Des Sciences. Serie I, Mathematique, 326 (03):Vojak, R.论文数: 0 引用数: 0 h-index: 0
- [42] On the reconstruction of polycrystalline microstructures from two-point correlation statisticsJOURNAL OF COMPUTER-AIDED MATERIALS DESIGN, 2005, 10 (03): : 163 - 173Hansen, BL论文数: 0 引用数: 0 h-index: 0机构: Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USA Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USAAdams, BL论文数: 0 引用数: 0 h-index: 0机构: Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USA Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USALyon, ME论文数: 0 引用数: 0 h-index: 0机构: Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USA Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USAHenrie, A论文数: 0 引用数: 0 h-index: 0机构: Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USA Brigham Young Univ, Dept Mech Engn, Provo, UT 84602 USA
- [43] Two-point measurement energy statistics from particle scatteringPHYSICAL REVIEW RESEARCH, 2023, 5 (04):Jacob, Samuel L.论文数: 0 引用数: 0 h-index: 0机构: Trinity Coll Dublin, Dept Phys, Dublin, Ireland Trinity Coll Dublin, Dept Phys, Dublin, IrelandLandi, Gabriel T.论文数: 0 引用数: 0 h-index: 0机构: Univ Rochester, Dept Phys & Astron, Rochester, NY 14627 USA Trinity Coll Dublin, Dept Phys, Dublin, IrelandEsposito, Massimiliano论文数: 0 引用数: 0 h-index: 0机构: Univ Luxembourg, Phys & Mat Sci Res Unit, Complex Syst & Stat Mech, L-1511 Luxembourg, Luxembourg Trinity Coll Dublin, Dept Phys, Dublin, Ireland论文数: 引用数: h-index:机构:
- [44] Two-point statistics in non-homogeneous rotating turbulenceJOURNAL OF FLUID MECHANICS, 2024, 997Beaumard, P.论文数: 0 引用数: 0 h-index: 0机构: Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, France Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, FranceBragana, P.论文数: 0 引用数: 0 h-index: 0机构: Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, France Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, France论文数: 引用数: h-index:机构:Vassilicos, J. C.论文数: 0 引用数: 0 h-index: 0机构: Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, France Univ Lille, Arts & Metiers Inst Technol, CNRS, ONERA,Cent Lille,UMR 9014,LMFL Lab Mech Fluides L, F-59000 Lille, France
- [45] Two-point vorticity statistics in the inverse cascade of two-dimensional turbulencePHYSICS OF FLUIDS, 2012, 24 (12)Friedrich, R.论文数: 0 引用数: 0 h-index: 0机构: Univ Munster, Inst Theoret Phys, D-48149 Munster, Germany Univ Munster, Inst Theoret Phys, D-48149 Munster, GermanyVosskuhle, M.论文数: 0 引用数: 0 h-index: 0机构: ENS Lyon, Phys Lab, F-69007 Lyon, France Univ Munster, Inst Theoret Phys, D-48149 Munster, GermanyKamps, O.论文数: 0 引用数: 0 h-index: 0机构: Univ Munster, Ctr Nonlinear Sci, D-48149 Munster, Germany Univ Munster, Inst Theoret Phys, D-48149 Munster, GermanyWilczek, M.论文数: 0 引用数: 0 h-index: 0机构: Univ Munster, Inst Theoret Phys, D-48149 Munster, Germany Univ Munster, Inst Theoret Phys, D-48149 Munster, Germany
- [46] Persistent homology in cosmic shear II. A tomographic analysis of DES-Y1ASTRONOMY & ASTROPHYSICS, 2022, 667Heydenreich, Sven论文数: 0 引用数: 0 h-index: 0机构: Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany Argelander Inst Astron, Hugel 71, D-53121 Bonn, GermanyBruck, Benjamin论文数: 0 引用数: 0 h-index: 0机构: Swiss Fed Inst Technol, Dept Math Sci, Ramistr 101, CH-8092 Zurich, Switzerland Argelander Inst Astron, Hugel 71, D-53121 Bonn, GermanyBurger, Pierre论文数: 0 引用数: 0 h-index: 0机构: Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany论文数: 引用数: h-index:机构:Unruh, Sandra论文数: 0 引用数: 0 h-index: 0机构: Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany Ruhr Univ Bochum, Fac Phys & Astron, Astron Inst AIRUB, German Ctr Cosmol Lensing, D-44780 Bochum, Germany Argelander Inst Astron, Hugel 71, D-53121 Bonn, GermanyCastro, Tiago论文数: 0 引用数: 0 h-index: 0机构: Osserv Astron Trieste, Via Tiepolo 11, I-34131 Trieste, Italy Inst Fundamental Phys Universe, Via Beirut 2, I-34151 Trieste, Italy Ist Nazl Fis Nucl, Sez Trieste, I-34100 Trieste, Italy Argelander Inst Astron, Hugel 71, D-53121 Bonn, GermanyDolag, Klaus论文数: 0 引用数: 0 h-index: 0机构: Ludwig Maximilians Univ Munchen, Fak Phys, Univ Sternwarte, Scheinerstr 1, D-81679 Munich, Germany Max Planck Inst Astrophys, Karl Schwarzschild Str 1, D-85741 Garching, Germany Argelander Inst Astron, Hugel 71, D-53121 Bonn, GermanyMartinet, Nicolas论文数: 0 引用数: 0 h-index: 0机构: Aix Marseille Univ, LAM, CNES, CNRS, Marseille, France Argelander Inst Astron, Hugel 71, D-53121 Bonn, Germany
- [47] Hyper Suprime-Cam Year 3 results: Cosmology from cosmic shear two-point correlation functionsPHYSICAL REVIEW D, 2023, 108 (12)Li, Xiangchong论文数: 0 引用数: 0 h-index: 0机构: Univ Tokyo, Univ Tokyo Inst Adv Study UTIAS, Kavli Inst Phys & Math Universe WPI, Chiba 2778583, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAZhang, Tianqing论文数: 0 引用数: 0 h-index: 0机构: Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Dalal, Roohi论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Rau, Markus M.论文数: 0 引用数: 0 h-index: 0机构: Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA Argonne Natl Lab, Div High Energy Phys, Lemont, IL 60439 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Takada, Masahiro论文数: 0 引用数: 0 h-index: 0机构: Univ Tokyo, Univ Tokyo Inst Adv Study UTIAS, Kavli Inst Phys & Math Universe WPI, Chiba 2778583, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Strauss, Michael A.论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAMiyatake, Hironao论文数: 0 引用数: 0 h-index: 0机构: Univ Tokyo, Univ Tokyo Inst Adv Study UTIAS, Kavli Inst Phys & Math Universe WPI, Chiba 2778583, Japan Nagoya Univ, Kobayashi Maskawa Inst Origin Particles & Univers, Nagoya, Aichi 4648602, Japan Nagoya Univ, Inst Adv Res, Nagoya, Aichi 4648601, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAShirasaki, Masato论文数: 0 引用数: 0 h-index: 0机构: Natl Inst Nat Sci, Natl Astron Observ Japan, Mitaka, Tokyo 1818588, Japan Inst Stat Math, Tachikawa, Tokyo 1908562, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAHamana, Takashi论文数: 0 引用数: 0 h-index: 0机构: Natl Inst Nat Sci, Natl Astron Observ Japan, Mitaka, Tokyo 1818588, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Luo, Wentao论文数: 0 引用数: 0 h-index: 0机构: Univ Sci & Technol China, Sch Phys Sci, Hefei 230026, Anhui, Peoples R China Univ Sci & Technol China, Sch Astron & Space Sci, Dept Astron, CAS Key Lab Res Galaxies & Cosmol, Hefei 230026, Anhui, Peoples R China Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USANishizawa, Atsushi J.论文数: 0 引用数: 0 h-index: 0机构: Nagoya Univ, Kobayashi Maskawa Inst Origin Particles & Univers, Nagoya, Aichi 4648602, Japan Nagoya Univ, Inst Adv Res, Nagoya, Aichi 4648601, Japan Gifu Shotoku Gakuen Univ, Gifu 5016194, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USATakahashi, Ryuichi论文数: 0 引用数: 0 h-index: 0机构: Hirosaki Univ, Fac Sci & Technol, 3 Bunkyo Cho, Hirosaki, Aomori 0368561, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA论文数: 引用数: h-index:机构:Osato, Ken论文数: 0 引用数: 0 h-index: 0机构: Chiba Univ, Ctr Frontier Sci, 1-33 Yayoi Cho,Inage Ku, Chiba 2638522, Japan Chiba Univ, Grad Sch Sci, Dept Phys, 1-33 Yayoi Cho,Inage Ku, Chiba 2638522, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAKannawadi, Arun论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USASunayama, Tomomi论文数: 0 引用数: 0 h-index: 0机构: Nagoya Univ, Kobayashi Maskawa Inst Origin Particles & Univers, Nagoya, Aichi 4648602, Japan Univ Arizona, Dept Astron & Steward Observ, 933 North Cherry Ave, Tucson, AZ 85719 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAArmstrong, Robert论文数: 0 引用数: 0 h-index: 0机构: Lawrence Livermore Natl Lab, Livermore, CA 94551 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USABosch, James论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAKomiyama, Yutaka论文数: 0 引用数: 0 h-index: 0机构: Hosei Univ, Fac Sci & Engn, Dept Adv Sci, 3-7-2 Kajino Cho, Koganei, Tokyo 1848584, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USALupton, Robert H.论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USALust, Nate B.论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAMacArthur, Lauren A.论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAMiyazaki, Satoshi论文数: 0 引用数: 0 h-index: 0机构: Natl Astron Observ Japan, Subaru Telescope, 650 North Aohoku Pl, Hilo, HI 96720 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAMurayama, Hitoshi论文数: 0 引用数: 0 h-index: 0机构: Univ Tokyo, Univ Tokyo Inst Adv Study UTIAS, Kavli Inst Phys & Math Universe WPI, Chiba 2778583, Japan Univ Calif Berkeley, Berkeley Ctr Theoret Phys, Berkeley, CA 94720 USA Lawrence Berkeley Natl Lab, Theory Grp, Berkeley, CA 94720 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USANishimichi, Takahiro论文数: 0 引用数: 0 h-index: 0机构: Univ Tokyo, Univ Tokyo Inst Adv Study UTIAS, Kavli Inst Phys & Math Universe WPI, Chiba 2778583, Japan Kyoto Univ, Yukawa Inst Theoret Phys, Ctr Gravitat Phys & Quantum Informat, Kyoto 6068502, Japan Kyoto Sangyo Univ, Dept Astrophys & Atmospher Sci, Fac Sci, Kita Ku, Kyoto 6038555, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAOkura, Yuki论文数: 0 引用数: 0 h-index: 0机构: Natl Inst Nat Sci, Natl Astron Observ Japan, Mitaka, Tokyo 1818588, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAPrice, Paul A.论文数: 0 引用数: 0 h-index: 0机构: Princeton Univ, Dept Astrophys Sci, Princeton, NJ 08544 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USATait, Philip J.论文数: 0 引用数: 0 h-index: 0机构: Natl Astron Observ Japan, Subaru Telescope, 650 North Aohoku Pl, Hilo, HI 96720 USA Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USATanaka, Masayuki论文数: 0 引用数: 0 h-index: 0机构: Natl Inst Nat Sci, Natl Astron Observ Japan, Mitaka, Tokyo 1818588, Japan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USAWang, Shiang-Yu论文数: 0 引用数: 0 h-index: 0机构: Acad Sinica, Inst Astron & Astrophys, Taipei 10617, Taiwan Carnegie Mellon Univ, Dept Phys, McWilliams Ctr Cosmol, 5000 Forbes Ave, Pittsburgh, PA 15213 USA
- [48] ISOTROPY IN THE TWO-POINT ANGULAR CORRELATION FUNCTION OF THE COSMIC MICROWAVE BACKGROUNDASTROPHYSICAL JOURNAL LETTERS, 2012, 748 (02)Zhang, Sophie论文数: 0 引用数: 0 h-index: 0机构: Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA Univ Michigan, Dept Phys, Ann Arbor, MI 48109 USA
- [49] A comparison of multiple-point statistics and two-point statistics for spectral-spatial land cover classification2016 4RTH INTERNATIONAL WORKSHOP ON EARTH OBSERVATION AND REMOTE SENSING APPLICATIONS (EORSA), 2016,Shi, Zhongkui论文数: 0 引用数: 0 h-index: 0机构: Peking Univ, Inst Remote Sensing, Beijing 100871, Peoples R China Peking Univ, GIS, Sch Earth & Space Sci, Beijing 100871, Peoples R China Peking Univ, Inst Remote Sensing, Beijing 100871, Peoples R ChinaLi, Peijun论文数: 0 引用数: 0 h-index: 0机构: Peking Univ, Inst Remote Sensing, Beijing 100871, Peoples R China Peking Univ, GIS, Sch Earth & Space Sci, Beijing 100871, Peoples R China Peking Univ, Inst Remote Sensing, Beijing 100871, Peoples R China
- [50] One- and two-point source statistics from the LOFAR Two-metre Sky Survey first data releaseASTRONOMY & ASTROPHYSICS, 2020, 643论文数: 引用数: h-index:机构:Hale, C.论文数: 0 引用数: 0 h-index: 0机构: Univ Oxford, Astrophys, Denys Wilkinson Bldg,Keble Rd, Oxford OX1 3RH, England CSIRO Astron & Space Sci, POB 1130, Bentley, WA 6102, Australia Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyBhardwaj, N.论文数: 0 引用数: 0 h-index: 0机构: Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyBiermann, M.论文数: 0 引用数: 0 h-index: 0机构: Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyBacon, D. J.论文数: 0 引用数: 0 h-index: 0机构: Univ Portsmouth, Inst Cosmol & Gravitat, Dennis Sciama Bldg,Burnaby Rd, Portsmouth PO1 3FX, Hants, England Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany论文数: 引用数: h-index:机构:Rottgering, H. J. A.论文数: 0 引用数: 0 h-index: 0机构: Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanySchwarz, D. J.论文数: 0 引用数: 0 h-index: 0机构: Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyShimwell, T.论文数: 0 引用数: 0 h-index: 0机构: Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands Netherlands Inst Radio Astron, ASTRON, Postbus 2, NL-7990 AA Dwingeloo, Netherlands Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyBest, P. N.论文数: 0 引用数: 0 h-index: 0机构: Royal Observ, Inst Astron, SUPA, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyDuncan, K. J.论文数: 0 引用数: 0 h-index: 0机构: Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyHardcastle, M. J.论文数: 0 引用数: 0 h-index: 0机构: Univ Hertfordshire, Sch Phys Astron & Math, Ctr Astrophys Res, Coll Lane, Hatfield AL10 9AB, Herts, England Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanySabater, J.论文数: 0 引用数: 0 h-index: 0机构: Royal Observ, Inst Astron, SUPA, Blackford Hill, Edinburgh EH9 3HJ, Midlothian, Scotland Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyTasse, C.论文数: 0 引用数: 0 h-index: 0机构: Univ PSL, Observ Paris, CNRS, GEPI, 5 Pl Jules Janssen, F-92190 Meudon, France Univ PSL, Observ Paris, CNRS, USN, 5 Pl Jules Janssen, F-92190 Meudon, France Rhodes Univ, Dept Phys & Elect, POB 94, ZA-6140 Grahamstown, South Africa Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyWhite, G. J.论文数: 0 引用数: 0 h-index: 0机构: Rutherford Appleton Lab, RAL Space, Didcot OX11 0NL, Oxon, England Open Univ, Dept Phys Sci, Walton Hall, Milton Keynes MK7 6AA, Bucks, England Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, GermanyWilliams, W. L.论文数: 0 引用数: 0 h-index: 0机构: Leiden Univ, Leiden Observ, POB 9513, NL-2300 RA Leiden, Netherlands Univ Bielefeld, Fak Phys, Postfach 100131, D-33501 Bielefeld, Germany