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Detection of CMB-Cluster Lensing using Polarization Data from SPTpol

Physical Review Letters 2019年第18期123卷 181301-181301页

作者： S. Raghunathan S. Patil E. Baxter B. A. Benson L. E. Bleem T. M. Crawford G. P. Holder T. McClintock C. L. Reichardt T. N. Varga N. Whitehorn P. A. R. Ade S. Allam A. J. Anderson J. E. Austermann S. Avila J. S. Avva D. Bacon J. A. Beall A. N. Bender F. Bianchini S. Bocquet D. Brooks D. L. Burke J. E. Carlstrom J. Carretero F. J. Castander C. L. Chang H. C. Chiang R. Citron M. Costanzi A. T. Crites L. N. da Costa S. Desai H. T. Diehl J. P. Dietrich M. A. Dobbs P. Doel S. Everett A. E. Evrard C. Feng B. Flaugher P. Fosalba J. Frieman J. Gallicchio J. García-Bellido E. Gaztanaga E. M. George T. Giannantonio A. Gilbert R. A. Gruendl J. Gschwend N. Gupta G. Gutierrez T. de Haan N. W. Halverson N. Harrington J. W. Henning G. C. Hilton D. L. Hollowood W. L. Holzapfel K. Honscheid J. D. Hrubes N. Huang J. Hubmayr K. D. Irwin T. Jeltema M. Carrasco Kind L. Knox N. Kuropatkin O. Lahav A. T. Lee D. Li M. Lima A. Lowitz M. A. G. Maia J. L. Marshall J. J. McMahon P. Melchior F. Menanteau S. S. Meyer R. Miquel L. M. Mocanu J. J. Mohr J. Montgomery C. Corbett Moran A. Nadolski T. Natoli J. P. Nibarger G. Noble V. Novosad R. L. C. Ogando S. Padin A. A. Plazas C. Pryke D. Rapetti A. K. Romer A. Roodman A. Carnero Rosell E. Rozo J. E. Ruhl E. S. Rykoff B. R. Saliwanchik E. Sanchez J. T. Sayre V. Scarpine K. K. Schaffer M. Schubnell S. Serrano I. Sevilla-Noarbe C. Sievers G. Smecher M. Smith M. Soares-Santos A. A. Stark K. T. Story E. Suchyta M. E. C. Swanson G. Tarle C. Tucker K. Vanderlinde T. Veach J. De Vicente J. D. Vieira V. Vikram G. Wang W. L. K. Wu V. Yefremenko Y. Zhang Department of Physics and Astronomy University of California Los Angeles California 90095 USA School of Physics University of Melbourne Parkville VIC 3010 Australia Department of Physics and Astronomy University of Pennsylvania Philadelphia Pennsylvania 19104 USA Fermi National Accelerator Laboratory MS209 P.O. Box 500 Batavia Illinois 60510 USA Kavli Institute for Cosmological Physics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA Department of Astronomy and Astrophysics University of Chicago 5640 South Ellis Avenue Chicago Illinois 60637 USA High Energy Physics Division Argonne National Laboratory 9700 S. Cass Avenue Argonne Illinois 60439 USA Astronomy Department University of Illinois at Urbana-Champaign 1002 W. Green Street Urbana Illinois 61801 USA Department of Physics University of Illinois Urbana-Champaign 1110 W. Green Street Urbana Illinois 61801 USA Canadian Institute for Advanced Research CIFAR Program in Gravity and the Extreme Universe Toronto Ontario M5G 1Z8 Canada Department of Physics University of Arizona Tucson Arizona 85721 USA Max Planck Institute for Extraterrestrial Physics Giessenbachstrasse Garching 85748 Germany Universitäts-Sternwarte Fakultät für Physik LudwigMaximilians Universität München Scheinerstr. 1 München 81679 Germany Cardiff University Cardiff CF10 3XQ United Kingdom Fermi National Accelerator Laboratory P. O. Box 500 Batavia Illinois 60510 USA NIST Quantum Devices Group 325 Broadway Mailcode 817.03 Boulder Colorado 80305 USA Instituto de Fisica Teorica UAM/CSIC Universidad Autonoma de Madrid 28049 Madrid Spain Department of Physics University of California Berkeley California 94720 USA Institute of Cosmology & Gravitation University of Portsmouth Dennis Sciama Building Burnaby Road Portsmouth PO1 3FX United Kingdom Faculty of Physics Ludwig-Maximilians-Universität Scheinerstr. 1 Munich 81679 Germany Department of Physics & Astronomy University College London Gower

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg2 survey at the locations of roughly 18 000 clusters with richness λ≥10 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8σ. The mean stacked mass of the selected sample is found to be (1.43±0.40)×1014M⊙ which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements.

关键词： Cosmic microwave background Gravitational lenses Galaxy clusters

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Effect of Medium of Instruction on programming Ability Acquired through Screencast

Effect of Medium of Instruction on Programming Ability Acqui...

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Learning and Teaching in Computing and Engineering (LaTiCE)

作者： Yogendra Pal Sridhar Iyer Inter-Disciplinary Program in Educational Technology Indian Institute of Technology Bombay Mumbai India Department of Computer Science and Engineering Indian Institute of Technology Bombay Mumbai India

Students who have studied in their native language face difficulty in acquiring programming skills through English medium instruction. One solution for this is to create screen casts of live coding along with instructor explanations in the native language. In this paper we examine the impact of screen cast based self-paced learning for Hindi medium (native language) students. Our study had three groups - One group had Hindi as the medium of prior instruction, and learned programming through screen casts in Hindi. Another group, also had Hindi as the medium of prior instruction, but learned through screen casts in English. The third group had English as the medium of prior instruction, and learned through screen casts in English. We compared the performance of the three groups using a post-test having items of fact, concept and process content types. We found that Hindi medium students who studied from Hindi screen casts performed as well as English medium students who studied from English screen casts. Both groups performed better than Hindi medium students who studied from English screen casts. The effect of medium of instruction was significant for the content types of fact, process and concept.

关键词： Education programming profession computers Standards Analysis of variance Encoding

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Secure amplify-and-forward untrusted relaying networks using cooperative jamming and zero-forcing cancelation

Secure amplify-and-forward untrusted relaying networks using...

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IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)

作者： Ki-Hong Park Mohamed-Slim Alouini Electrical Engineering Program Computer King Abdullah University of Science and Technology (KAUST) Thuwal Makkah Province Kingdom of Saudi Arabia

In this paper, we investigate secure transmission in untrusted amplify-and-forward half-duplex relaying networks with the help of cooperative jamming at the destination (CJD). Under the assumption of full channel state information (CSI), conventional CJD using self-interference cancellation at the destination is efficient when the untrusted relay has no capability to suppress the jamming signal. However, if the source and destination are equipped with a single antenna and the only untrusted relay is equipped with N multiple antennas, it can remove the jamming signal from the received signal by linear filters and the full multiplexing gain of relaying cannot be achievable with the conventional CJD due to the saturation of the secrecy rate at the high transmit power regime. We propose in this paper new CJD scheme where neither destination nor relay can acquire CSI of relay-destination link. Our proposed scheme utilizes zero-forcing cancelation based on known jamming signals instead of self-interference subtraction, while the untrusted relay cannot suppress the jamming signals due to the lack of CSI. We show that the secrecy rate of the proposed scheme can enjoy a half of multiplexing gain in half-duplex relaying while that of conventional CJD is saturated at high transmit power for N ≥2. The impact of channel estimation error at the destination is also investigated to show the robustness of the proposed scheme against strong estimation errors.

关键词： Jamming Relays Antennas Security Signal to noise ratio Receivers Multiplexing

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A demonstration of improved constraints on primordial gravitational waves with delensing

arXiv

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arXiv 2020年

作者： Ade, P.A.R. Ahmed, Z. Amiri, M. Anderson, A.J. Austermann, J.E. Avva, J.S. Barkats, D. Thakur, R. Basu Beall, J.A. Bender, A.N. Benson, B.A. Bianchini, F. Bischoff, C.A. Bleem, L.E. Bock, J.J. Boenish, H. Bullock, E. Buza, V. Carlstrom, J.E. Chang, C.L. Cheshire, J.R. Chiang, H.C. Chou, T.-L. Citron, R. Connors, J. Moran, C. Corbett Cornelison, J. Crawford, T.M. Crites, A.T. Crumrine, M. Cukierman, A. de Haan, T. Dierickx, M. Dobbs, M.A. Duband, L. Everett, W. Fatigoni, S. Filippini, J.P. Fliescher, S. Gallicchio, J. George, E.M. Germaine, T.St. Goeckner-Wald, N. Goldfinger, D.C. Grayson, J. Gupta, N. Hall, G. Halpern, M. Halverson, N.W. Harrison, S. Henderson, S. Henning, J.W. Hildebrandt, S.R. Hilton, G.C. Holder, G.P. Holzapfel, W.L. Hrubes, J.D. Huang, N. Hubmayr, J. Hui, H. Irwin, K.D. Kang, J. Karkare, K.S. Karpel, E. Kefeli, S. Kernasovskiy, S.A. Knox, L. Kovac, J.M. Kuo, C.L. Lau, K. Lee, A.T. Leitch, E.M. Li, D. Lowitz, A. Manzotti, A. McMahon, J.J. Megerian, K.G. Meyer, S.S. Millea, M. Mocanu, L.M. Moncelsi, L. Montgomery, J. Nadolski, A. Namikawa, T. Natoli, T. Netterfield, C.B. Nguyen, H.T. Nibarger, J.P. Noble, G. Novosad, V. O’Brient, R. Ogburn, R.W. Omori, Y. Padin, S. Palladino, S. Patil, S. Prouve, T. Pryke, C. Racine, B. Reichardt, C.L. Reintsema, C.D. Richter, S. Ruhl, J.E. Saliwanchik, B.R. Schaffer, K.K. Schillaci, A. Schmitt, B.L. Schwarz, R. Sheehy, C.D. Sievers, C. Smecher, G. Soliman, A. Stark, A.A. Steinbach, B. Sudiwala, R.V. Teply, G.P. Thompson, K.L. Tolan, J.E. Tucker, C. Turner, A.D. Umiltà, C. Veach, T. Vieira, J.D. Vieregg, A.G. Wandui, A. Wang, G. Weber, A.C. Whitehorn, N. Wiebe, D.V. Willmert, J. Wong, C.L. Wu, W.L. Kimmy Yang, H. Yefremenko, V. Yoon, K.W. Young, E. Yu, C. Zeng, L. Zhang, C. Cardiff University CardiffCF10 3XQ United Kingdom SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo ParkCA94025 United States Kavli Institute for Particle Astrophysics and Cosmology Stanford University 452 Lomita Mall StanfordCA94305 United States Department of Physics and Astronomy University of British Columbia VancouverBCV6T 1Z1 Canada Fermi National Accelerator Laboratory MS209 P.O. Box 500 BataviaIL60510 United States NIST Quantum Devices Group 325 Broadway Mailcode 817.03 BoulderCO80305 United States Department of Physics University of Colorado BoulderCO80309 United States Department of Physics University of California BerkeleyCA94720 United States Harvard-Smithsonian Center for Astrophysics 60 Garden Street CambridgeMA02138 United States California Institute of Technology MS 249-17 1216 E. California Blvd. PasadenaCA91125 United States High Energy Physics Division Argonne National Laboratory 9700 S. Cass Avenue ArgonneIL60439 United States Kavli Institute for Cosmological Physics University of Chicago 5640 South Ellis Avenue ChicagoIL60637 United States Department of Astronomy and Astrophysics University of Chicago 5640 South Ellis Avenue ChicagoIL60637 United States School of Physics University of Melbourne ParkvilleVIC3010 Australia Department of Physics University of Cincinnati CincinnatiOH45221 United States Jet Propulsion Laboratory PasadenaCA91109 United States Department of Physics Harvard University CambridgeMA02138 United States Minnesota Institute for Astrophysics University of Minnesota MinneapolisMN55455 United States Department of Physics University of Chicago 5640 South Ellis Avenue ChicagoIL60637 United States Enrico Fermi Institute University of Chicago 5640 South Ellis Avenue ChicagoIL60637 United States Department of Physics McGill University 3600 Rue University MontrealQCH3A 2T8 Canada School of Mathematics Statistics & Computer Science University of KwaZulu-Natal

We present a constraint on the tensor-to-scalar ratio, r, derived from measurements of cosmic microwave background (CMB) polarization B-modes with "delensing," whereby the uncertainty on r contributed by the sample variance of the gravitational lensing B-modes is reduced by cross-correlating against a lensing B-mode template. This template is constructed by combining an estimate of the polarized CMB with a tracer of the projected large-scale structure. The large-scale-structure tracer used is a map of the cosmic infrared background derived from Planck satellite data, while the polarized CMB map comes from a combination of South Pole Telescope, Bicep/Keck, and Planck data. We expand the Bicep/Keck likelihood analysis framework to accept a lensing template and apply it to the Bicep/Keck data set collected through 2014 using the same parametric foreground modelling as in the previous analysis. From simulations, we find that the uncertainty on r is reduced by ∼ 10%, from σ(r)= 0.024 to 0.022, which can be compared with a ∼ 26% reduction obtained when using a perfect lensing template or if there were zero lensing B-modes. Applying the technique to the real data, the constraint on r is improved from r0.05 Copyright © 2020, The Authors. All rights reserved.

关键词： Cosmology

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Elephant Herding Optimization

Elephant Herding Optimization

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International Symposium on Computational and Business Intelligence (ISCBI)

作者： Gai-Ge Wang Suash Deb Leandro dos S. Coelho School of Computer Science and Technology Jiangsu Normal University Xuzhou China Dept. of Computer Science & Engineering Cambridge Institute of Technology Ranchi INDIA Industrial and Systems Engineering Graduate Program Pontifical Catholic University of Parana Curitiba Brazil

In this paper, a new kind of swarm-based metaheuristic search method, called Elephant Herding Optimization (EHO), is proposed for solving optimization tasks. The EHO method is inspired by the herding behavior of elephant group. In nature, the elephants belonging to different clans live together under the leadership of a matriarch, and the male elephants will leave their family group when they grow up. These two behaviors can be modelled into two following operators: clan updating operator and separating operator. In EHO, the elephants in each clan are updated by its current position and matriarch through clan updating operator. It is followed by the implementation of the separating operator which can enhance the population diversity at the later search phase. To demonstrate its effectiveness, EHO is benchmarked by fifteen test cases comparing with BBO, DE and GA. The results show that EHO can find the better values on most benchmark problems than those three metaheuristic algorithms.

关键词： Optimization Benchmark testing Sociology Statistics Particle swarm optimization Electronic mail Search methods

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25th Annual Computational Neuroscience Meeting CNS-2016, Seogwipo City, South Korea, July 2-7, 2016 Abstracts

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BMC NEUROscience 2016年第1期17卷 1-112页

作者： [Anonymous] Computational Neurobiology Laboratory The Salk Institute for Biological Studies San Diego USA UNIC CNRS Gif sur Yvette France The European Institute for Theoretical Neuroscience (EITN) Paris France ATR Computational Neuroscience Laboratories Kyoto Japan Krembil Research Institute University Health Network Toronto Canada Department of Physiology University of Toronto Toronto Canada Department of Medicine (Neurology) University of Toronto Toronto Canada Department of Physics University of New Hampshire Durham USA Department of Neurophysiology Nencki Institute of Experimental Biology Warsaw Poland Department of Theory Wigner Research Centre for Physics of the Hungarian Academy of Sciences Budapest Hungary Department of Mathematical Sciences KAIST Daejoen Republic of Korea Department of Mathematics University of Houston Houston USA Department of Biochemistry & Cell Biology and Institute of Biosciences and Bioengineering Rice University Houston USA Department of Biology and Biochemistry University of Houston Houston USA Grupo de Neurocomputación Biológica Dpto. de Ingeniería Informática Escuela Politécnica Superior Universidad Autónoma de Madrid Madrid Spain Department of Biological Sciences University of Southern California Los Angeles USA Center for Neuroscience Korea Institute of Science and Technology Seoul South Korea Department of Neurology Albert Einstein College of Medicine Bronx USA Center for Neuroscience KIST Seoul South Korea Department of Neuroscience University of Science and Technology Daejon South Korea Systems Neuroscience Group QIMR Berghofer Medical Research Institute Herston Australia Department of Psychology Yonsei University Seoul South Korea Department of Psychiatry Kyung Hee University Hospital at Gangdong Seoul South Korea Department of Psychiatry Veterans Administration Boston Healthcare System and Harvard Medical School Brockton USA Department of Electrical and Electronic Engineering The University of Melbourne Parkvil

A1 Functional advantages of cell-type heterogeneity in neural circuits Tatyana O. Sharpee A2 Mesoscopic modeling of propagating waves in visual cortex Alain Destexhe A3 Dynamics and biomarkers of mental disorders Mitsuo Kawato F1 Precise recruitment of spiking output at theta frequencies requires dendritic h-channels in multi-compartment models of oriens-lacunosum/moleculare hippocampal interneurons Vladislav Sekulić, Frances K. Skinner F2 Kernel methods in reconstruction of current sources from extracellular potentials for single cells and the whole brains Daniel K. Wójcik, Chaitanya Chintaluri, Dorottya Cserpán, Zoltán Somogyvári F3 The synchronized periods depend on intracellular transcriptional repression mechanisms in circadian clocks. Jae Kyoung Kim, Zachary P. Kilpatrick, Matthew R. Bennett, Kresimir Josić O1 Assessing irregularity and coordination of spiking-bursting rhythms in central pattern generators Irene Elices, David Arroyo, Rafael Levi, Francisco B. Rodriguez, Pablo Varona O2 Regulation of top-down processing by cortically-projecting parvalbumin positive neurons in basal forebrain Eunjin Hwang, Bowon Kim, Hio-Been Han, Tae Kim, James T. McKenna, Ritchie E. Brown, Robert W. McCarley, Jee Hyun Choi O3 Modeling auditory stream segregation, build-up and bistability James Rankin, Pamela Osborn Popp, John Rinzel O4 Strong competition between tonotopic neural ensembles explains pitch-related dynamics of auditory cortex evoked fields Alejandro Tabas, André Rupp, Emili Balaguer-Ballester O5 A simple model of retinal response to multi-electrode stimulation Matias I. Maturana, David B. Grayden, Shaun L. Cloherty, Tatiana Kameneva, Michael R. Ibbotson, Hamish Meffin O6 Noise correlations in V4 area correlate with behavioral performance in visual discrimination task Veronika Koren, Timm Lochmann, Valentin Dragoi, Klaus Obermayer O7 Input-location dependent gain modulation in cerebellar nucleus neurons Maria Psarrou, Maria Schilstra, Neil Davey, Benjamin Torben-Ni

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26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 Antwerp, Belgium. 15-20 July 2017 Abstracts

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BMC NEUROscience 2017年第SUPPL 1期18卷 95-176页

作者： [Anonymous] Department of Neuroscience Yale University New Haven CT 06520 USA Department Physiology & Pharmacology SUNY Downstate Brooklyn NY 11203 USA NYU School of Engineering 6 MetroTech Center Brooklyn NY 11201 USA Departament de Matemàtica Aplicada Universitat Politècnica de Catalunya Barcelona 08028 Spain Institut de Neurobiologie de la Méditerrannée (INMED) INSERM UMR901 Aix-Marseille Univ Marseille France Center of Neural Science New York University New York NY USA Aix-Marseille Univ INSERM INS Inst Neurosci Syst Marseille France Laboratoire de Physique Théorique et Modélisation CNRS UMR 8089 Université de Cergy-Pontoise 95300 Cergy-Pontoise Cedex France Department of Mathematics and Computer Science ENSAT Abdelmalek Essaadi’s University Tangier Morocco Laboratory of Natural Computation Department of Information and Electrical Engineering and Applied Mathematics University of Salerno 84084 Fisciano SA Italy Department of Medicine University of Salerno 84083 Lancusi SA Italy Dipartimento di Fisica Università degli Studi Aldo Moro Bari and INFN Sezione Di Bari Italy Data Analysis Department Ghent University Ghent Belgium Coma Science Group University of Liège Liège Belgium Cruces Hospital and Ikerbasque Research Center Bilbao Spain BIOtech Department of Industrial Engineering University of Trento and IRCS-PAT FBK 38010 Trento Italy Department of Data Analysis Ghent University Ghent 9000 Belgium The Wellcome Trust Centre for Neuroimaging University College London London WC1N 3BG UK Department of Electronic Engineering NED University of Engineering and Technology Karachi Pakistan Blue Brain Project École Polytechnique Fédérale de Lausanne Lausanne Switzerland Departement of Mathematics Swansea University Swansea Wales UK Laboratory for Topology and Neuroscience at the Brain Mind Institute École polytechnique fédérale de Lausanne Lausanne Switzerland Institute of Mathematics University of Aberdeen Aberdeen Scotland UK Department of Integrativ

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Predictive efficacy of a new association football league format in Polish Ekstraklasa 2

Predictive efficacy of a new association football league for...

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2nd Workshop on Machine Learning and Data Mining for Sports Analytics, MLSA 2015

作者： Lasek, Jan Gagolewski, Marek Interdisciplinary PhD Studies Program Institute of Computer Science Polish Academy of Sciences Jana Kazimierza 5 Warsaw01-248 Poland Systems Research Institute Polish Academy of Sciences Newelska 6 Warsaw01-447 Poland Faculty of Mathematics and Information Science Warsaw University of Technology Koszykowa 75 Warsaw00-662 Poland

In this study we investigate the recently introduced competition format for the top association football division in Poland (similar to one used in, e.g., Belgium and Kazakhstan). We compare it to the double round-robin tournament which is the most prevalent league for-mat among European leagues. In a simulation study we show that the new league format has better ability to determine the strongest competitor as the winner of a league as well as it yields higher correlation with theoretical latent teams' strength parameters in the model.

关键词： Routers

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Production and education of the modular robot made by 3D printer

Production and education of the modular robot made by 3D pri...

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Asian Control Conference

作者： Kaoru Mitsuhashi Yasuhiro Ohyama Hiroshi Hashimoto Shintaro Ishijima School of Computer Science Tokyo University of Technology Hachioji Tokyo Japan Master Program of Innovation for Design and Engineering Advanced Institute of Industrial Technology Shinagawa Tokyo Japan

The modular robot is constructed by the same shape and function module. It is able to transform and exchange, because it is multiple constitution. However, a mass quantity production of the module is difficult. Then, we focus on 3D printer. It is able to produce on a large scale easily and reasonably, but researchers and engineers need to operate 3D CAD and 3D printer. In this paper, we hold the 3D-CAD and 3D printers' workshop, and the effect is investigated. Afterwards, we evaluate the mechanical function of the simple module made by 3D printer. In addition, we suggest the modular robot of many modules.

关键词： Three-dimensional displays Printers Joints Robots Design automation Wheels Shape

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Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

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Physical Review B 2016年第10期93卷 104424-104424页

作者： N. Naghibolashrafi S. Keshavarz Vinay I. Hegde A. Gupta W. H. Butler J. Romero K. Munira P. LeClair D. Mazumdar J. Ma A. W. Ghosh C. Wolverton Tri-campus materials science program The University of Alabama Tuscaloosa Alabama 35487 USA Center for Materials for Information Technology The University of Alabama Tuscaloosa Alabama 35487 USA Department of Physics and Astronomy The University of Alabama Tuscaloosa Alabama 35487 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA Department of Chemistry The University of Alabama Tuscaloosa Alabama 35487 USA Department of Chemical and Biological Engineering The University of Alabama Tuscaloosa Alabama 35487 USA Department of Physics Southern Illinois University Carbondale Illinois 62901 USA Department of Electrical and Computer Engineering University of Virginia Charlottesville Virginia 22904 USA

Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. Fe2TiSb, expected to be a full Heusler compound crystallizing in the L21 structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition Fe1.5TiSb with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into Fe1.5TiSb grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant Fe1.5TiSb phase appears to crystallize in a defective L21-like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the L21 structure was performed. Using the cluster expansion, we computationally scanned >103 configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group R3m, with composition Fe1.5TiSb, i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of L21 phase Fe2TiSb and C1b phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the R3m structure is the ground state.

关键词： Heusler alloy First-principles calculations Machine learning X-ray imaging

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