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IEEE Symposium on Nuclear Science (NSS/MIC)

作者： Soo Mee Kim Jae Sung Lee Hee Seo Jin-Hyung Park Chan Hyeong Kim Chun Sik Lee Myung Chul Lee Dong Soo Lee Soo-Jin Lee Department of Nuclear Medicine and Interdisciplinary Program in Radiation Applied Life Science Major Seoul National University Seoul South Korea Department of Nuclear Engineering Hanyang University Seoul South Korea Department of Physics Chung-Ang University Seoul South Korea Department of Electronic Engineering Pai Chai University Daejeon South Korea

A Compton camera is an imaging system for three-dimensional (3D) distribution of gamma emitting sources based on Compton scattering interaction. The measurement error on energies and positions directly leads to uncertainties on the formation of cones and degrades the spatial resolution of the reconstructed images. Mostly the limited energy resolution, Doppler broadening and position segmentation of detectors cause angular and positional uncertainties on measurements. Since the conical surfaces are delocalized by angular and positional uncertainties into image space, degradation of spatial resolution may be severe depending on the distance (or depth) from the Compton camera. In order to enhance the deteriorated spatial resolution due to angular and positional uncertainties, this study investigates 3D Gaussian point spread function (PSF) incorporable into listmode ordered subset expectation maximization (LMOSEM) as a part of system matrix. Especially the depth-dependent PSF is applied as resolution recovery (RR) technique by image-space convolution operation. We investigated two different RR approaches: one (denoted by LMOSEM-RR-F) is when the convolution is performed in forward projection step only, and the other (denoted by LMOSEM-RR-FB) is when it is performed in both forward and backward projection steps. Using Monte Carlo data for 7 point sources at different depth from the Compton camera, the fitted axial and radial FWHM functions were obtained as FWHM axial (i)=0.2442i+1.054 and FWHM radial (i)=0.2369i-1.005, respectively. The simulation results showed that both RR approaches with depth dependent PSF gave an improvement on spatial resolution comparing to LMOSEM without RR techniques. Although LMOSEM-RR-F provided better resolution than LMOSEM-RR-FB, LMOSEM-RR-FB could still be useful for low counting statistics in measurement.

关键词： Cameras Spatial resolution Image reconstruction Three dimensional displays Uncertainty

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Design and fabrication of nanoscale antireflection structures with linearly graded refractive index

Design and fabrication of nanoscale antireflection structure...

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2010 10th IEEE Conference on Nanotechnology, NANO 2010

作者： Song, Young Min Jang, Sung Jun Choi, Hee Ju Yu, Jae Su Lee, Yong Tak Department of Information and Communications Gwangju Institute of Science and Technology 1 Oryong-dong Buk-gu Gwangju 500-712 Korea Republic of Graduate Program of Photonics and Applied Physics Gwangju Institute of Science and Technology 1 Oryong-dong Buk-gu Gwangju 500-712 Korea Republic of Department of Electronic Engineering Kyung Hee University 1 Seocheon-dong Giheung-gu Yongin-si Gyeonggi-do 446-701 Korea Republic of Department of Nanobio Materials and Electronics Gwangju Institute of Science and Technology 1 Oryong-dong Buk-gu Gwangju 500-712 Korea Republic of

ISBN: (纸本)9781424470334

We demonstrate nanoscale antireflection structures on GaAs substrate with linearly graded effective refractive index using a lenslike shape transfer for broadband light-absorbing device application. From reflectance calculation of cone- and parabola-shaped subwavelength grating (SWG) structures, it is found that the parabola shaped structures has lower mean reflectance compared to that of the cone shaped structures over a wide wavelength range. The fabricated SWG structures with parabola shape show the reflectance of below 5 % in a 300-1200 nm wavelength range. ©2010 IEEE.

关键词： Reflection

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Exact constructions of a family of dense periodic packings of tetrahedra

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Physical Review E 2010年第4期81卷 041310-041310页

作者： S. Torquato Y. Jiao Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544 USA

The determination of the densest packings of regular tetrahedra (one of the five Platonic solids) is attracting great attention as evidenced by the rapid pace at which packing records are being broken and the fascinating packing structures that have emerged. Here we provide the most general analytical formulation to date to construct dense periodic packings of tetrahedra with four particles per fundamental cell. This analysis results in six-parameter family of dense tetrahedron packings that includes as special cases recently discovered “dimer” packings of tetrahedra, including the densest known packings with density ϕ=40004671=0.856347…. This study strongly suggests that the latter set of packings are the densest among all packings with a four-particle basis. Whether they are the densest packings of tetrahedra among all packings is an open question, but we offer remarks about this issue. Moreover, we describe a procedure that provides estimates of upper bounds on the maximal density of tetrahedron packings, which could aid in assessing the packing efficiency of candidate dense packings.

关键词： constructions family tetrahedra tetrahedrons family Dense Platonic solid

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Fifteen Years of U.S.—China Cooperative Research in Underwater Acoustics: 1995–2010

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AIP Conference Proceedings 2010年第1期1272卷

作者： Ellen Livingston Jeffrey Simmen Ocean Acoustics Program Office of Naval Research Arlington VA 22203 USA Applied Physics Laboratory University of Washington Seattle WA 98105 USA

The Office of Naval Research and the Chinese Academy of Sciences established and continue to encourage an unprecedented collaboration between the United States and China in the basic research field of ocean acoustics. This paper describes the progression of events in the scientific relationship. This cooperative research effort, primarily focused on shallow‐water acoustics, has varied over fifteen years. It has involved numerous researchers and institutions from the U.S., China, and other countries, and it has resulted in productive workshops, conferences, field experiments, research collaborations, and scientific publications.

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T-shaped plasmonic array as a narrow-band thermal emitter or biosensor

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Optics Express 2009年第16期17卷 13526-13531页

作者： Wang, Chih-Ming Chang, Yia-Chung Abbas, Mohammed Nadhim Shih, Ming-Hsiung Tsai, Din Ping Research Center for Applied Sciences Academia Sinica Taipei 11529 Taiwan Institute of Physics and Nano Science and Technology Program Taiwan International Graduate Program Academia Sinica Taipei 115 Taiwan Department of Engineering and System Science NTHU Hsinchu 300 Taiwan Department of Physics National Taiwan University Taipei 106 Taiwan

A T-shaped plasmonic array is proposed for application as an effective thermal emitter or biosensor. The reflection and thermal radiation properties of a T-shaped array are investigated theoretically. The angular dependent reflectance spectrum shows a clear resonant dip at 0.36eV for full polar angles. No other significant localized resonant mode is found in the investigated spectral range from 0.12eV to 0.64eV. According to the Kirchhoff s law, the thermal radiation of the proposed structure can lead to a sharp peak at 3.5 νm with low sideband emission. We have also found that the T-shaped structure filled with organic material such as PMMA with different thicknesses (10 nm -50 nm) can lead to significant shift of the resonance wavelength. Thus, the T-shaped structure can also be used as a good sensor for organic materials. © 2009 Optical Society of America.

关键词： Heat radiation

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Chakrabarty et al. Reply:

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Physical Review Letters 2010年第11期104卷 119602-119602页

作者： Rajan K. Chakrabarty Hans Moosmüller W. Patrick Arnott Mark A. Garro Guoxun Tian Jay G. Slowik Eben S. Cross Jeong-Ho Han Paul Davidovits Timothy B. Onasch Douglas R. Worsnop Desert Research Institute Nevada System of Higher Education Reno Nevada 89512 USA Chemical Physics Program University of Nevada Reno Nevada 89557 USA Department of Physics University of Nevada Reno Nevada 89557 USA Division of Engineering and Applied Sciences Harvard University Cambridge Massachusetts 02138 USA Department of Chemistry University of Toronto Toronto Ontario M5S 3H6 Canada Department of Chemistry Boston College Chestnut Hill Massachusetts 02467 USA Aerodyne Research Inc. Billerica Massachusetts 01821 USA

A Reply to the Comment by Markus Sander et al..

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Phase behavior of colloidal superballs: Shape interpolation from spheres to cubes

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Physical Review E 2010年第6期81卷 061105-061105页

作者： Robert D. Batten Frank H. Stillinger Salvatore Torquato Department of Chemical Engineering Princeton University Princeton New Jersey 08544 USA Department of Chemistry Princeton University Princeton New Jersey 08544 USA Department of Physics Princeton University Princeton New Jersey 08544 USA Princeton Center for Theoretical Science Princeton University Princeton New Jersey 08544 USA Princeton Institute for the Science and Technology of Materials Princeton University Princeton New Jersey 08544 USA Program in Applied and Computational Mathematics Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08544 USA

The phase behavior of hard superballs is examined using molecular dynamics within a deformable periodic simulation box. A superball’s interior is defined by the inequality |x|2q+|y|2q+|z|2q≤1, which provides a versatile family of convex particles (q≥0.5) with cubelike and octahedronlike shapes as well as concave particles (q<0.5) with octahedronlike shapes. Here, we consider the convex case with a deformation parameter q between the sphere point (q=1) and the cube (q=∞). We find that the asphericity plays a significant role in the extent of cubatic ordering of both the liquid and crystal phases. Calculation of the first few virial coefficients shows that superballs that are visually similar to cubes can have low-density equations of state closer to spheres than to cubes. Dense liquids of superballs display cubatic orientational order that extends over several particle lengths only for large q. Along the ordered, high-density equation of state, superballs with 1

关键词： Spheres

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Dislocation climb strengthening in systems with immobile obstacles: Three-dimensional level-set simulation study

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Physical Review B 2010年第5期81卷 054104-054104页

作者： Zi Chen Kevin T. Chu David J. Srolovitz Jeffrey M. Rickman Mikko P. Haataja Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08540 USA Princeton Institute for the Science and Technology of Materials (PRISM) Princeton University Princeton New Jersey 08540 USA Vitamin D Inc. Menlo Park California 94025 USA Institute of High Performance Computing Singapore Singapore Department of Materials Science and Engineering Lehigh University Bethlehem Pennsylvania 18015 USA Department of Physics Lehigh University Bethlehem Pennsylvania 18015 USA Program in Applied and Computational Mathematics (PACM) Princeton University Princeton New Jersey 08540 USA

We employ a parallel, three-dimensional level-set code to simulate the dynamics of isolated dislocation lines and loops in an obstacle-rich environment. This system serves as a convenient prototype of those in which extended, one-dimensional objects interact with obstacles and the out-of-plane motion of these objects is key to understanding their pinning-depinning behavior. In contrast to earlier models of dislocation motion, we incorporate long-ranged interactions among dislocation segments and obstacles to study the effect of climb on dislocation dynamics in the presence of misfitting penetrable obstacles/solutes, as embodied in an effective climb mobility. Our main observations are as follows. First, increasing climb mobility leads to more effective pinning by the obstacles, implying increased strengthening. Second, decreasing the range of interactions significantly reduces the effect of climb. The dependence of the critical stress on obstacle concentration and misfit strength is also explored and compared with existing models. In particular, our results are shown to be in reasonable agreement with the Friedel-Suzuki theory. Finally, the limitations inherent in the simplified model employed here, including the neglect of some lattice effects and the use of a coarse-grained climb mobility, are discussed.

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Generalized models reveal stabilizing factors in food webs (vol 325, pg 747, 2009)

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SCIENCE 2009年第5946期325卷 1341-1341页

作者： Gross, T. Max Planck Institute for Physics of Complex Systems N&#246 thnitzer Stra&#223 e 38 01187 Dresden Germany. Evolution and Ecology Program International Institute for Applied Systems Analysis Schlossplatz 1 2361 Laxenburg Austria.

Insights into what stabilizes natural food webs have alwaysbeen limited by a fundamental dilemma: Studies either need tomake unwarranted simplifying assumptions, which undermines theirrelevance, or only examine few replicates of small food webs,which hampers the robustness of findings. We used generalizedmodeling to study several billion replicates of food webs withnonlinear interactions and up to 50 species. In this way, firstwe show that higher variability in link strengths stabilizesfood webs only when webs are relatively small, whereas largerwebs are instead destabilized. Second, we reveal a new powerlaw describing how food-web stability scales with the numberof species and their connectance. Third, we report two universalrules: Food-web stability is enhanced when (i) species at ahigh trophic level feed on multiple prey species and (ii) speciesat an intermediate trophic level are fed upon by multiple predatorspecies.

关键词： Animals Biodiversity Biodiversity Ecosystem Ecosystem Food Chain Food Chain Models, Biological Nonlinear Dynamics Population Dynamics Predatory Behavior

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ERRATUM: 'MULTI-WAVELENGTH OBSERVATIONS OF THE FLARING GAMMA-RAY BLAZAR 3C 66A IN 2008 OCTOBER' (2011, ApJ, 726, 43)

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The Astrophysical Journal 2011年第1期731卷

作者： A. A. Abdo M. Ackermann M. Ajello L. Baldini J. Ballet G. Barbiellini D. Bastieri K. Bechtol R. Bellazzini B. Berenji R. D. Blandford E. Bonamente A. W. Borgland A. Bouvier J. Bregeon A. Brez M. Brigida P. Bruel R. Buehler S. Buson G. A. Caliandro R. A. Cameron P. A. Caraveo S. Carrigan J. M. Casandjian E. Cavazzuti C. Cecchi Ö. Çelik E. Charles A. Chekhtman C. C. Cheung J. Chiang S. Ciprini R. Claus J. Cohen-Tanugi J. Conrad L. Costamante S. Cutini D. S. Davis C.D. Dermer F. de Palma S. W. Digel E. do Couto e Silva P. S. Drell R. Dubois D. Dumora C. Favuzzi S. J. Fegan P. Fortin M. Frailis L. Fuhrmann Y. Fukazawa S. Funk P. Fusco F. Gargano D. Gasparrini N. Gehrels S. Germani N. Giglietto P. Giommi F. Giordano M. Giroletti T. Glanzman G. Godfrey I. A. Grenier J. E. Grove L. Guillemot S. Guiriec D. Hadasch M. Hayashida E. Hays D. Horan R. E. Hughes R. Itoh G. Jóhannesson A. S. Johnson T. J. Johnson W.N. Johnson T. Kamae H. Katagiri J. Kataoka J. Knödlseder M. Kuss J. Lande L. Latronico S.-H. Lee F. Longo F. Loparco B. Lott M. N. Lovellette P. Lubrano A. Makeev M. N. Mazziotta J.E. McEnery J. Mehault P. F. Michelson T. Mizuno A. A. Moiseev C. Monte M. E. Monzani A. Morselli I. V. Moskalenko S. Murgia T. Nakamori M. Naumann-Godo I. Nestoras P. L. Nolan J.P. Norris E. Nuss T. Ohsugi A. Okumura N. Omodei E. Orlando J. F. Ormes M. Ozaki D. Paneque J.H. Panetta D. Parent V. Pelassa M. Pepe M. Pesce-Rollins F. Piron T. A. Porter S. Rainò R. Rando M. Razzano A. Reimer O. Reimer L. C. Reyes J. Ripken S. Ritz R. W. Romani M. Roth H. F.-W. Sadrozinski D. Sanchez A. Sander J. D. Scargle C. Sgrò M. S. Shaw P. D. Smith G. Spandre P. Spinelli M. S. Strickman D.J. Suson H. Takahashi T. Tanaka J. B. Thayer J. G. Thayer D. J. Thompson L. Tibaldo D. F. Torres G. Tosti A. Tramacere T. L. Usher J. Vandenbroucke V. Vasileiou N. Vilchez V. Vitale A. P. Waite P. Wang B. L. Winer K. S. Wood Z. Yang T. Ylinen M. Ziegler ((The Fermi-LAT Collaboration)) V. A. Acciari E. Aliu T. Arlen T. Aune M. Beilicke W. Benbow M. Böttcher D. Boltuch S.M. Space Science Division Naval Research Laboratory Washington DC 20375 USA National Research Council Research Associate National Academy of Sciences Washington DC 20001 USA W. W. Hansen Experimental Physics Laboratory Kavli Institute for Particle Astrophysics and Cosmology Department of Physics and SLAC National Accelerator Laboratory Stanford University Stanford CA 94305 USA Istituto Nazionale di Fisica Nucleare Sezione di Pisa I-56127 Pisa Italy Laboratoire AIM CEA-IRFU/CNRS/Université Paris Diderot Service d'Astrophysique CEA Saclay 91191 Gif sur Yvette France Istituto Nazionale di Fisica Nucleare Sezione di Trieste I-34127 Trieste Italy Dipartimento di Fisica Università di Trieste I-34127 Trieste Italy Istituto Nazionale di Fisica Nucleare Sezione di Padova I-35131 Padova Italy Dipartimento di Fisica 'G. Galilei ' Università di Padova I-35131 Padova Italy Istituto Nazionale di Fisica Nucleare Sezione di Perugia I-06123 Perugia Italy Dipartimento di Fisica Università degli Studi di Perugia I-06123 Perugia Italy Dipartimento di Fisica 'M. Merlin' dell'Università e del Politecnico di Bari I-70126 Bari Italy Istituto Nazionale di Fisica Nucleare Sezione di Bari 70126 Bari Italy Laboratoire Leprince-Ringuet École polytechnique CNRS/IN2P3 Palaiseau France Institut de Ciencies de l'Espai (IEEC-CSIC) Campus UAB 08193 Barcelona Spain INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica I-20133 Milano Italy Agenzia Spaziale Italiana (ASI) Science Data Center I-00044 Frascati (Roma) Italy NASA Goddard Space Flight Center Greenbelt MD 20771 USA Center for Research and Exploration in Space Science and Technology (CRESST) and NASA Goddard Space Flight Center Greenbelt MD 20771 USA Department of Physics and Center for Space Sciences and Technology University of Maryland Baltimore County Baltimore MD 21250 USA George Mason University Fairfax VA 22030 USA Laboratoire de Physique Théorique et Astroparticules Université Montpellier 2 CNRS/IN2P3 Montpellier

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