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Proceedings of the 32nd International Conference on Neural Information Processing Systems

作者： Aran Nayebi Daniel Bear Jonas Kubilius Kohitij Kar Surya Ganguli David Sussillo James J. DiCarlo Daniel L. K. Yamins Neurosciences PhD Program Stanford University Stanford CA Department of Psychology Stanford University Stanford CA McGovern Institute for Brain Research MIT Cambridge MA and Brain and Cognition KU Leuven Leuven Belgium McGovern Institute for Brain Research MIT Cambridge MA and Google Brain Google Inc. Mountain View CA Department of Applied Physics Stanford University Stanford CA Google Brain Google Inc. Mountain View CA McGovern Institute for Brain Research MIT Cambridge MA and Department of Brain and Cognitive Sciences MIT Cambridge MA Department of Psychology Stanford University Stanford CA and Department of Computer Science Stanford University Stanford CA and Wu Tsai Neurosciences Institute Stanford CA

Feed-forward convolutional neural networks (CNNs) are currently state-of-the-art for object classification tasks such as ImageNet. Further, they are quantitatively accurate models of temporally-averaged responses of neurons in the primate brain's visual system. However, biological visual systems have two ubiquitous architectural features not shared with typical CNNs: local recurrence within cortical areas, and long-range feedback from downstream areas to upstream areas. Here we explored the role of recurrence in improving classification performance. We found that standard forms of recurrence (vanilla RNNs and LSTMs) do not perform well within deep CNNs on the ImageNet task. In contrast, novel cells that incorporated two structural features, bypassing and gating, were able to boost task accuracy substantially. We extended these design principles in an automated search over thousands of model architectures, which identified novel local recurrent cells and long-range feedback connections useful for object recognition. Moreover, these task-optimized ConvRNNs matched the dynamics of neural activity in the primate visual system better than feedforward networks, suggesting a role for the brain's recurrent connections in performing difficult visual behaviors.

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Magnetoelectric memory function with optical readout

arXiv

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arXiv 2017年

作者： Kocsis, V. Penc, K. Rõõm, T. Nagel, U. Vít, J. Romhányi, J. Tokunaga, Y. Taguchi, Y. Tokura, Y. Kézsmárki, I. Bordács, S. Wako Saitama351-0198 Japan Department of Physics Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group Budapest1111 Hungary Institute for Solid State Physics and Optics Wigner Research Centre for Physics Hungarian Academy of Sciences P.O.B. 49 BudapestH-1525 Hungary National Institute of Chemical Physics and Biophysics Tallinn12618 Estonia Institute of Physics ASCR Na Slovance 2 Prague 8182 21 Eue Faculty of Nuclear Science and Physical Engineering Czech Technical University Břehová 7 Prague 1115 19 Eue Okinawa Institute of Science and Technology Graduate University Onna-sonOkinawa904-0395 Japan Department of Advanced Materials Science University of Tokyo Kashiwa277-8561 Japan Quantum-Phase Electronics Center Department of Applied Physics University of Tokyo Tokyo113-8656 Japan Department of Applied Physics University of Tokyo Hongo Tokyo113-8656 Japan Experimental Physics 5 Center for Electronic Correlations and Magnetism Institute of Physics University of Augsburg Augsburg86159 Germany Hungarian Academy of Sciences Premium Postdoctor Program Budapest1051 Hungary

The ultimate goal of multiferroic research is the development of new-generation non-volatile memory devices1, the so-called magnetoelectric (ME) memories, where magnetic bits are controlled via electric fields without the application of electrical currents subject to dissipation. This low-power operation exploits the entanglement of the magnetization and the electric polarization coexisting in multiferroic materials2,3. Here we demonstrate the optical readout of ME memory states in the antiferromagnetic (AFM) and antiferroelectric (AFE) LiCoPO4, based on the strong absorption difference of THz radiation between its two types of ME domains. This unusual contrast is attributed to the dynamic ME effect of the spin-wave excitations, as confirmed by our microscopic model, which also captures the characteristics of the observed static ME effect. Our proof-of-principle study, demonstrating the control and the optical readout of ME domains in LiCoPO4, lays down the foundation for future ME memory devices based on antiferroelectric-antiferromagnetic insulators. Copyright © 2017, The Authors. All rights reserved.

关键词： Digital storage

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Long-term Room Temperature Instability in Thermal Conductivity of InGaZnO Thin Films

Long-term Room Temperature Instability in Thermal Conductivi...

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作者： Cui, Boya Bruce Buchholz, D. Zeng, Li Bedzyk, Michael Chang, Robert P. H. Grayson, Matthew Applied Physics Program Northwestern University EvanstonIL60208 United States Electrical Engineering and Computer Science Northwestern University EvanstonIL60208 United States Material Science and Engineering Northwestern University EvanstonIL60208 United States

The cross-plane thermal conductivities of InGaZnO (IGZO) thin films in different morphologies were measured on three occasions within 19 months, using the 3ω method at room temperature 300 K. Amorphous (a-), semi-crystalline (semi-c-) and crystalline (c-) IGZO films were grown by pulsed laser deposition (PLD), followed by X-ray diffraction (XRD) for evaluation of film quality and crystallinity. Semi-c-IGZO shows the highest thermal conductivity, even higher than the most ordered crystal-like phase. After being stored in dry low-oxygen environment for months, a drastic decrease of semi-c-IGZO thermal conductivity was observed, while the thermal conductivity slightly reduced in c-IGZO and remained unchanged in a-IGZO. This change in thermal conductivity with storage time can be attributed to film structural relaxation and vacancy diffusion to grain boundaries. © 2016 Materials Research Society.

关键词： Thin films

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Hypostatic jammed packings of frictionless nonspherical particles

arXiv

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arXiv 2017年

作者： VanderWerf, Kyle Jin, Weiwei Shattuck, Mark D. O'Hern, Corey S. Department of Physics Yale University New HavenCT06520 United States Benjamin Levich Institute and Physics Department City College of New York New YorkNY10031 United States Department of Mechanics and Engineering Science Peking University Beijing100871 China Department of Mechanical Engineering & Materials Science Yale University New HavenCT06520 United States Department of Applied Physics Yale University New HavenCT06520 United States Graduate Program in Computational Biology and Bioinformatics Yale University New HavenCT06520 United States

We perform computational studies of static packings of a variety of nonspherical particles including circulo-lines, circulo-polygons, ellipses, asymmetric dimers, dumbbells, and others to determine which shapes form packings with fewer contacts than degrees of freedom (hypostatic packings) and which have equal numbers of contacts and degrees of freedom (isostatic packings), and to understand why hypostatic packings of nonspherical particles can be mechanically stable despite having fewer contacts than that predicted from naïve constraint counting. To generate highly accurate force- and torque-balanced packings of circulo-lines and -polygons, we developed an interparticle potential that gives continuous forces and torques as a function of the particle coordinates. We show that the packing fraction and coordination number at jamming onset obey a master-like form for all of the nonspherical particle packings we studied when plotted versus the particle asphericity A, which is proportional to the ratio of the squared perimeter to the area of the particle. Further, the eigenvalue spectra of the dynamical matrix for packings of different particle shapes collapse when plotted at the same A. For hypostatic packings of nonspherical particles, we verify that the number of "quartic" modes along which the potential energy increases as the fourth power of the perturbation amplitude matches the number of missing contacts relative to the isostatic value. We show that the fourth derivatives of the total potential energy in the directions of the quartic modes remain nonzero as the pressure of the packings is decreased to zero. In addition, we calculate the principal curvatures of the inequality constraints for each contact in circulo-line packings and identify specific types of contacts with inequality constraints that possess convex curvature. These contacts can constrain multiple degrees of freedom and allow hypostatic packings of nonspherical particles to be mechanically stable. C

关键词： Degrees of freedom (mechanics)

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Adaptive Materials: Light‐Driven Reversible Transformation between Self‐Organized Simple Cubic Lattice and Helical Superstructure Enabled by a Molecular Switch Functionalized Nanocage (Adv. Mater. 26/2018)

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Advanced Materials 2018年第26期30卷

作者： Kang Zhou Hari Krishna Bisoyi Jian‐Qiu Jin Cong‐Long Yuan Zhen Liu Dong Shen Yan‐Qing Lu Zhi‐Gang Zheng Weian Zhang Quan Li Department of Physics East China University of Science and Technology Shanghai 200237 China Liquid Crystal Institute and Chemical Physics Interdisciplinary Program Kent State University Kent OH 44242 USA Shanghai Key Laboratory of Functional Materials Chemistry East China University of Science and Technology Shanghai 200237 China National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced Microstructures and Colleague of Engineering and Applied Sciences Nanjing University Nanjing 210093 China

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Generation and reconstruction of time-bin entangled ququarts

Generation and reconstruction of time-bin entangled ququarts

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Frontiers in Optics, FiO 2016

作者： Nowierski, Samantha J. Oza, Neal N. Kumar, Prem Kanter, Gregory S. Northwestern University Applied Physics Program 2220 Campus Drive EvanstonIL60208 United States Northwestern University Center for Photonic Communication and Computing Department of Electrical Engineering and Computer Science 2145 Sheridan Road EvanstonIL60208 United States

We generate and reconstruct a maximally-entangled time-bin ququart using quantum state tomography and polarization-projective measurements. We measure a fidelity of 93.7±0.4% to a maximally-entangled ququart with... 详细信息

ISBN: (纸本)9781943580194

关键词： Fiber optic communications Four wave mixing Frequency combs Photons Single photon detectors Tomography

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Collapse and Nonlinear Instability of AdS Space with Angular Momentum

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Physical Review Letters 2017年第19期119卷 191104-191104页

作者： Matthew W. Choptuik Óscar J.C. Dias Jorge E. Santos Benson Way Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver British Columbia V6T 1W9 Canada CIFAR Cosmology and Gravity Program 180 Dundas Street W Suite 1400 Toronto Ontario M5G 1Z8 Canada STAG Research Centre and Mathematical Sciences University of Southampton Southampton SO17 1BJ United Kingdom Department of Applied Mathematics and Theoretical Physics University of Cambridge Wilberforce Road Cambridge CB3 0WA United Kingdom

We present a numerical study of rotational dynamics in AdS5 with equal angular momenta in the presence of a complex doublet scalar field. We determine that the endpoint of gravitational collapse is a Myers-Perry black hole for high energies and a hairy black hole for low energies. We investigate the time scale for collapse at low energies E, keeping the angular momenta J∝E in anti–de Sitter (AdS) length units. We find that the inclusion of angular momenta delays the collapse time, but retains a t∼1/E scaling. We perturb and evolve rotating boson stars, and find that boson stars near AdS space appear stable, but those sufficiently far from AdS space are unstable. We find that the dynamics of the boson star instability depend on the perturbation, resulting either in collapse to a Myers-Perry black hole, or development towards a stable oscillating solution.

关键词： Gauge-gravity dualities Gravity in dimensions other than four Numerical relativity

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Characteristic of molten fluoride salt system LiF-BeF2 (Flibe) and LiF-NaF-KF (Flinak) as coolant and fuel carrier in molten salt reactor (MSR)

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AIP Conference Proceedings 2017年第1期1799卷

作者： Che Nor Aniza Che Zainul Bahri Wadee’ah Mohd Al-Areqi Mohd ’Izzat Fahmi Mohd Ruf Amran Ab. Majid Nuclear Science Program School of Applied Physics Faculty of Science and Technology Universiti Kebangsaan Malaysia 43600 UKM Bangi Selangor Malaysia

Interest of fluoride salts have recently revived due to the high temperature application in nuclear reactors. Molten Salt Reactor (MSR) was designed to operate at high temperature in range 700 - 800°C and its fuel is dissolved in a circulating molten fluoride salt mixture. Molten fluoride salts are stable at high temperature, have good heat transfer properties and can dissolve high concentration of actinides and fission product. The aim of this paper was to discuss the physical properties (melting temperature, density and heat capacity) of two systems fluoride salt mixtures i.e; LiF-BeF2 (Flibe) and LiF-NaF-KF (Flinak) in terms of their application as coolant and fuel solvent in MSR. Both of these salts showed almost same physical properties but different applications in MSR. The advantages and the disadvantages of these fluoride salt systems will be discussed in this paper.

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Tunable Crystallinity and Charge Transfer in Two‐Dimensional G‐Quadruplex Organic Frameworks

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Angewandte Chemie 2018年第15期130卷

作者： Yi‐Lin Wu N. Scott Bobbitt Jenna L. Logsdon Natalia E. Powers‐Riggs Jordan N. Nelson Xiaolong Liu Timothy C. Wang Randall Q. Snurr Joseph T. Hupp Omar K. Farha Mark C. Hersam Michael R. Wasielewski Department of Chemistry Argonne-Northwestern Solar Energy Research (ANSER) Center and Institute for Sustainability and Energy at Northwestern Northwestern University Evanston IL USA Department of Chemical & Biological Engineering Northwestern University Evanston IL USA Applied Physics Graduate Program Northwestern University Evanston IL USA Department of Chemistry King Abdulaziz University Jeddah Saudi Arabia

DNA G‐quadruplex structures were recently discovered to provide reliable scaffolding for two‐dimensional organic frameworks due to the strong hydrogen‐bonding ability of guanine. Herein, 2,7‐diaryl pyrene building blocks with high HOMO energies and large optical gaps are incorporated into G‐quadruplex organic frameworks. The adjustable substitution on the aryl groups provides an opportunity to elucidate the framework formation mechanism; molecular non‐planarity is found to be beneficial for restricting interlayer slippage, and the framework crystallinity is highest when intermolecular interaction and non‐planarity strike a fine balance. When guanine‐functionalized pyrenes are co‐crystallized with naphthalene diimide, charge‐transfer (CT) complexes are obtained. The photophysical properties of the pyrene‐only and CT frameworks are characterized by UV/Vis and steady‐state and time‐resolved photoluminescence spectroscopies, and by EPR spectroscopy for the CT complex frameworks.

关键词： Charge-Transfer-Komplexe G-Quadruplexe Kristall-Engineering Organische Gerüststrukturen Selbstorganisation

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Thermal current-induced charge redistribution in wide CVD-grown graphene constriction

Thermal current-induced charge redistribution in wide CVD-gr...

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2016 Compound Semiconductor Week, CSW 2016

作者： Chuang, Chiashain Woo, Tak-Pong Liu, Fan-Hung Matsunaga, Masahiro Ochiai, Yuichi Liang, Chi-Te Aoki, Nubuyuki Graduate School of Advanced Integration Science Chiba University Chiba263-8522 Japan Department of Physics National Taiwan University Taipei106 Taiwan Germination Program Office Science and Technology Policy Research and Information Center NARLabs Taipei106 Taiwan Graduate Institute of Applied Physics National Taiwan University Taipei106 Taiwan

ISBN: (纸本)9781509019649

Chemical vapor deposition (CVD) graphene would find great applications in industrial graphene-based electronics recently. Most importantly, the one-dimensional constriction of CVD graphene due to its grain boundaries and merged domains revealing interesting interference effects, like Aharonov-Bohm effect. Such interesting interference transport behavior can be revealed by low-temperature scanning gate microscopy (LT-SGM) and be numerical simulated about the dynamic transport point of view by mean-field Gross-Pitaevskii equation. In order to realize graphene-based quantum transport device, our results suggested that the supplying additional thermal current could flood into the grain boundaries and merged domains in one-dimensional quantum confined CVD graphene so as to suppress the interference effect, a great discovery for graphene-based materials coherent electronic devices. © 2016 IEEE.

关键词： Graphene

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