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Experimental realization of crossover in shape and director field of nematic tactoids

Physical Review E 2015年第4期91卷 042507-042507页

作者： Vida Jamali Natnael Behabtu Bohdan Senyuk J. Alex Lee Ivan I. Smalyukh Paul van der Schoot Matteo Pasquali Department of Chemical and Biomolecular Engineering Rice University Houston Texas 77005 USA Department of Physics University of Colorado at Boulder Boulder Colorado 80309 USA Department of Electrical Computer and Energy Engineering and Materials Science and Engineering Program and Liquid Crystals Materials Research Center University of Colorado at Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA Polymer Physics Group for Theory of Polymers and Soft Matter Group Department of Applied Physics Eindhoven University of Technology P.O. Box 513 5600 MB Eindhoven The Netherlands Institute for Theoretical Physics Utrecht University Leuvenlaan 4 3584 CE Utrecht The Netherlands Department of Chemistry Department of Materials Science and NanoEngineering The Smalley Institute for Nanoscale Science and Technology Rice University Houston Texas 77005 USA

Spindle-shaped nematic droplets (tactoids) form in solutions of rod-like molecules at the onset of the liquid crystalline phase. Their unique shape and internal structure result from the interplay of the elastic deformation of the nematic and anisotropic surface forces. The balance of these forces dictates that tactoids must display a continuous variation in aspect ratio and director-field configuration. Yet, such continuous transition has eluded observation for decades: tactoids have displayed either a bipolar configuration with particles aligned parallel to the droplet interface or a homogeneous configuration with particles aligned parallel to the long axis of the tactoid. Here, we report the first observation of the continuous transition in shape and director-field configuration of tactoids in true solutions of carbon nanotubes in chlorosulfonic acid. This observation is possible because the exceptional length of carbon nanotubes shifts the transition to a size range that can be visualized by optical microscopy. Polarization micrographs yield the interfacial and elastic properties of the system. Absorbance anisotropy measurements provide the highest nematic order parameter (S=0.79) measured to date for a nematic phase of carbon nanotubes at coexistence with its isotropic phase.

关键词： NEMATIC liquid crystals RESEARCH CARBON nanotubes ABSORBANCE (Light) CHLOROSULFONIC acid OPTICAL microscopes ELASTICITY

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Design and numerical analysis of surface plasmon-enhanced fin Ge-Si light-emitting diode

Design and numerical analysis of surface plasmon-enhanced fi...

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作者： Jeong, Intae Kwon, Jooseong Kim, Changsoon Park, Young June Program in Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Seoul 151-742 Korea Republic of Department of Electrical and Computer Engineering School of Engineering Seoul National University Seoul 151-747 Korea Republic of Advanced Institutes of Convergence Technology Suwon Gyeonggi 443-270 Korea Republic of

Heavily-doped strained germanium (Ge) can emit light efficiently thanks to its pseudo direct band gap characteristic. This makes Ge a good candidate for on-chip monolithic light sources in silicon (Si) photonics systems. We propose fin-shaped Ge-Si heterojunction lightemitting diode (LED) with metal gates, which can enhance light emission by coupling with surface plasmon resonant modes and modulate light emission from the LED. We verify these two aspects through numerical analysis and device simulations. We develop the method to find the optimal device structure and specific device dimensions to maximize the spontaneous emission rate enhancement. Also we find that the LED can be modulated by a gate voltage bias. © 2014 Optical Society of America.

关键词： Surface plasmons

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Multi-scale bio-inspired place recognition

Multi-scale bio-inspired place recognition

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Zetao Chen Adam Jacobson Uğur M. Erdem Michael E. Hasselmo Michael Milford School of Electrical Engineering Computer Science at the Queensland University of Technology Center for Memory and Brain and Graduate Program for Neuroscience at Boston University

This paper presents a novel place recognition algorithm inspired by the recent discovery of overlapping and multi-scale spatial maps in the rodent brain. We mimic this hierarchical framework by training arrays of Support Vector Machines to recognize places at multiple spatial scales. Place match hypotheses are then cross-validated across all spatial scales, a process which combines the spatial specificity of the finest spatial map with the consensus provided by broader mapping scales. Experiments on three real-world datasets including a large robotics benchmark demonstrate that mapping over multiple scales uniformly improves place recognition performance over a single scale approach without sacrificing localization accuracy. We present analysis that illustrates how matching over multiple scales leads to better place recognition performance and discuss several promising areas for future investigation.

关键词： Training Support vector machines Feature extraction Rodents Image segmentation Robot sensing systems

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Calibrationless parallel imaging reconstruction based on structured low-rank matrix completion

Calibrationless parallel imaging reconstruction based on str...

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作者： Shin, Peter J. Larson, Peder E. Z. Ohliger, Michael A. Elad, Michael Pauly, John M. Vigneron, Daniel B. Lustig, Michael Department of Radiology and Biomedical Imaging University of California at San Francisco San FranciscoCA United States UC Berkeley-UCSF Graduate Program in Bioengineering CA United States Department of Electrical Engineering and Computer Science University of California at Berkeley BerkeleyCA United States Department of Computer Science Technion'Israel Institute of Technology Haifa Israel Magnetic Resonance Systems Research Laboratory Department of Electrical Engineering Stanford University StanfordCA United States

Purpose: A calibrationless parallel imaging reconstruction method, termed simultaneous autocalibrating and k-space estimation (SAKE), is presented. It is a data-driven, coil-by-coil reconstruction method that does not require a separate calibration step for estimating coil sensitivity information. Methods: In SAKE, an undersampled, multichannel dataset is structured into a single data matrix. The reconstruction is then formulated as a structured low-rank matrix completion problem. An iterative solution that implements a projection-ontosets algorithm with singular value thresholding is described. Results: Reconstruction results are demonstrated for retrospectively and prospectively undersampled, multichannel Cartesian data having no calibration signals. Additionally, non-Cartesian data reconstruction is presented. Finally, improved image quality is demonstrated by combining SAKE with wavelet-based compressed sensing. Conclusion: Because estimation of coil sensitivity information is not needed, the proposed method could potentially benefit MR applications where acquiring accurate calibration data is limiting or not possible at all. © 2013 Wiley Periodicals, Inc.

关键词： Compressed sensing

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THE SIMONS OBSERVATORY: science GOALS AND FORECASTS

arXiv

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arXiv 2018年

作者： Ade, Peter Aguirre, James Ahmed, Zeeshan Aiola, Simone Ali, Aamir Alonso, David Alvarez, Marcelo A. Arnold, Kam Ashton, Peter Austermann, Jason Awan, Humna Baccigalupi, Carlo Baildon, Taylor Barron, Darcy Battaglia, Nick Battye, Richard Baxter, Eric Bazarko, Andrew Beall, James A. Bean, Rachel Beck, Dominic Beckman, Shawn Beringue, Benjamin Bianchini, Federico Boada, Steven Boettger, David Bond, J. Richard Borrill, Julian Brown, Michael L. Bruno, Sarah Marie Bryan, Sean Calabrese, Erminia Calafut, Victoria Calisse, Paolo Carron, Julien Challinor, Anthony Chesmore, Grace Chinone, Yuji Chluba, Jens Cho, Hsiao-Mei Sherry Choi, Steve Coppi, Gabriele Cothard, Nicholas F. Coughlin, Kevin Crichton, Devin Crowley, Kevin D. Crowley, Kevin T. Cukierman, Ari D’Ewart, John M. Dünner, Rolando de Haan, Tijmen Devlin, Mark Dicker, Simon Didier, Joy Dobbs, Matt Dober, Bradley Duell, Cody J. Duff, Shannon Duivenvoorden, Adri Dunkley, Jo Dusatko, John Errard, Josquin Fabbian, Giulio Feeney, Stephen Ferraro, Simone Fluxà, Pedro Freese, Katherine Frisch, Josef C. Frolov, Andrei Fuller, George Fuzia, Brittany Galitzki, Nicholas Gallardo, Patricio A. Ghersi, Jose Tomas Galvez Gao, Jiansong Gawiser, Eric Gerbino, Martina Gluscevic, Vera Goeckner-Wald, Neil Golec, Joseph Gordon, Sam Gralla, Megan Green, Daniel Grigorian, Arpi Groh, John Groppi, Chris Guan, Yilun Gudmundsson, Jon E. Han, Dongwon Hargrave, Peter Hasegawa, Masaya Hasselfield, Matthew Hattori, Makoto Haynes, Victor Hazumi, Masashi He, Yizhou Healy, Erin Henderson, Shawn W. Hervias-Caimapo, Carlos Hill, Charles A. Hill, J. Colin Hilton, Gene Hilton, Matt Hincks, Adam D. Hinshaw, Gary Hložek, Renée Ho, Shirley Ho, Shuay-Pwu Patty Howe, Logan Huang, Zhiqi Hubmayr, Johannes Huffenberger, Kevin Hughes, John P. Ijjas, Anna Ikape, Margaret Irwin, Kent Jaffe, Andrew H. Jain, Bhuvnesh Jeong, Oliver Kaneko, Daisuke Karpel, Ethan D. Katayama, Nobuhiko Keating, Brian Kernasovskiy, Sarah S. Keskitalo, Reijo Kisner, Theodore Kiuchi, Kenji Klein, Jeff Knowles, Kenda Koopman, Brian Kosowsk School of Physics and Astronomy Cardiff University The Parade CardiffCF24 3AA United Kingdom Department of Physics and Astronomy University of Pennsylvania 209 South 33rd Street PhiladelphiaPA19104 United States Kavli Institute for Particle Astrophysics and Cosmology Menlo ParkCA94025 United States SLAC National Accelerator Laboratory Menlo ParkCA94025 United States Joseph Henry Laboratories of Physics Jadwin Hall Princeton University PrincetonNJ08544 United States Center for Computational Astrophysics Flatiron Institute 162 5th Avenue New YorkNY10010 United States Department of Physics University of California BerkeleyCA94720 United States University of Oxford Denys Wilkinson Building Keble Road OxfordOX1 3RH United Kingdom Computational Cosmology Center Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Physics University of California San Diego CA92093 United States Physics Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States University of Tokyo Kashiwa277- 8583 Japan NIST Quantum Sensors Group 325 Broadway Mailcode 687.08 BoulderCO80305 United States Department of Physics and Astronomy Rutgers State University of New Jersey PiscatawayNJ08854-8019 United States Via Bonomea 265 Trieste34136 Italy INFN Sezione di Trieste Padriciano 99 Trieste34149 Italy Department of Physics University of Michigan Ann Arbor48103 United States Department of Physics and Astronomy University of New Mexico AlbuquerqueNM87131 United States Department of Astronomy Cornell University IthacaNY14853 United States Jodrell Bank Centre for Astrophysics School of Physics and Astronomy University of Manchester Manchester United Kingdom AstroParticule et Cosmologie Univ Paris Diderot CNRS/IN2P3 CEA/Irfu Obs de Paris Sorbonne Paris Cité France DAMTP Centre for Mathematical Sciences University of Cambridge Wilberforce Road CambridgeCB3 OWA United Kingdom School of Physics Universi

The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial configuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping ≈ 10% of the sky to a white noise level of 2 µK-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of σ(r) = 0.003. The large aperture telescope will map ≈ 40% of the sky at arcminute angular resolution to an expected white noise level of 6 µK-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev–Zel’dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sou

关键词： Tensors

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Accurate radio distance estimation by phase measurements with multiple frequencies

Accurate radio distance estimation by phase measurements wit...

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International Conference on Indoor Positioning and Indoor Navigation (IPIN)

作者： Mathias Pelka Christian Bollmeyer Horst Hellbrück Department of Electrical Engineering and Computer Science Luebeck University of Applied Sciences (LUAS) Germany University of Luebeck Graduate School for Computing in Medicine and Life Sciences Germany

Indoor localization is important for logistics, industrial applications and for several consumer applications. In the area of logistics, e.g. warehouses, localization accuracy within a few meters is desired. Available radio based systems within that accuracy are neither cost effective nor easy to deploy. Distance estimation together with triangulation are one of the standard solutions for localization. In this work, we propose phase measurements between two wireless sensor nodes for distance estimation. We introduce a mathematical model to estimate distances from phase measurements with multiple frequencies and provide a systematic analysis of possible sources of errors. Additionally, we derive requirements, e.g. resolution for a phase measurement unit to achieve a given accuracy. We present measurements for evaluation to confirm our theoretical results. Our implementation comprises a low cost IEEE 802.15.4 hardware with a built-in phase measurement unit. We implement the developed algorithm for distance estimation in our wireless sensor networks and use two wireless sensor nodes to perform a phase measurement. The contributions of the paper comprise a new model for phase measurements to estimate distances and a preliminary evaluation with our hardware.

关键词： Phase measurement Accuracy Estimation Frequency measurement Receivers Wireless sensor networks Indoor navigation

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Highly efficient (11.1%) small molecule multi-junction organic photovoltaic cells

Highly efficient (11.1%) small molecule multi-junction organ...

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2014 IEEE 40th Photovoltaic Specialist Conference (PVSC)

作者： Xiaozhou Che Xin Xiao Stephen R. Forrest Applied Physics Program University of Michigan Ann Arbor MI USA Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

We present multi-junction small molecule organic photovoltaic (OPV) cells with efficiencies over 11%. The devices consist of two or three, vacuum thermally evaporated planar-mixed heterojunction sub-cells with minimal absorption overlap between the cells. By introducing a transparent interconnecting layer, a dual element (tandem) cell achieves a power conversion efficiency of 10.0 ± 0.5%. We further improve the cell performance by adding an additional (3 rd ) sub-cell that absorbs at the second order optical interference maximum within the stack. The triple-junction cell significantly improves the quantum efficiency at shorter wavelengths, achieving a power conversion efficiency of 11.1 ± 0.5%, which to our knowledge, is the highest reported for a multi-junction OPV cell in the scientific literature.

关键词： Absorption Photovoltaic cells Interference Adaptive optics Cathodes Current measurement Optical filters

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Efficient real-time detection of terahertz pulse radiation by "listening to" photoacoustic generation

Efficient real-time detection of terahertz pulse radiation b...

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Laser science, LS 2014

作者： Chen, Sung-Liang Zhang, Cheng Chang, You-Chia Ok, Jong G. Ling, Tao Mihnev, Momchil T. Norris, Theodore B. Jay Guo, L. Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States Applied Physics Program University of Michigan Ann ArborMI48109 United States Department of Mechanical Engineering University of Michigan Ann ArborMI48109 United States University of Michigan Shanghai Jiao Tong University Joint Institute Shanghai200240 China

We demonstrate real time terahertz detection based on its absorption by carbon nanotubes composite and detection of the generated photoacoustic signal. This method has advantages of real time response, compact size an... 详细信息

ISBN: (纸本)1557522863

关键词： Yarn

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A study on self-configuration in the differential evolution algorithm

A study on self-configuration in the differential evolution ...

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IEEE Symposium on Differential Evolution (SDE)

作者： Rodrigo C. P. Silva Rodolfo A. Lopes Alan R. R. Freitas Frederico G. Guimaraes Department of Electrical and Computer Engineering McGill University Montreal Canada Graduate Program in Electrical Engineering Federal University of Minas Gerais (UFMG) Brazil Department of Computer Science Federal University-of Ouro Preto (UFOP) Brazil Guimarães Department of Electrical Engineering Federal University of Minas Gerais (UFMG) Brazil

ISBN: (纸本)9781479944606

The great development in the area of evolutionary algorithms in recent decades has increased the range of applications of these tools and improved its performance in different fronts. In particular, the Differential Evolution (DE) algorithm has proven to be a simple and efficient optimizer in several contexts. Despite of its success, its performance is closely related to the choice of variation operators and the parameters which control these operators. To increase the robustness of the method and the ease of use for the average user, the pursuit for methods of self-configuration has been increasing as well. There are several methods in the literature for setting parameters and operators. In order to understand the effects of these approaches on the performance of DE, this paper presents a thorough experimental analysis of the main existing paradigms. The results show that simple approaches are able to bring significant improvements to the performance of DE.

关键词： Sociology Statistics Vectors Equations Indexes Educational institutions Electronic mail

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Scattering assisted launch of SPR modes in Au films

Scattering assisted launch of SPR modes in Au films

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Optical Sensors, 2014

作者： Canning, J. Karim, A. Tzoumis, N. Tan, Y. Patyk, R. Trimby, P. Interdisciplinary Photonics Laboratories School of Chemistry The University of Sydney 222 Madsen Building F09 Sydney2006 Australia Institute of Photonics Technology Jinan University Guangzhou510632 China Graduate School of Electrical Engineering and Applied Computer Science Federal University of Technology-Paraná Curitiba PR80230-901 Brazil The University of Sydney Sydney2006 Australia

ISBN: (纸本)9781557528209

We report the excitation of a surface plasmon resonance (SPR) close to the orthogonal axis of a gold (Au) film on borosilicate glass. The need for prisms is removed simplifying the practical requirements for photonic devices and sensors. Spectroscopic measurement of SPR spectral shifts ~5o incidence within a reflection spectrophotometer for two liquids are taken. © 2014 OSA.

关键词： Surface plasmon resonance

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