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Frequency‐Driven Self‐Organized Helical Superstructures Loaded with Mesogen‐Grafted Silica Nanoparticles

Angewandte Chemie 2016年第42期128卷

作者： Karla G. Gutierrez‐Cuevas Ling Wang Zhi‐gang Zheng Hari K. Bisoyi Guoqiang Li Loon‐Seng Tan Richard A. Vaia Quan Li Liquid Crystal Institute and Chemical Physics Interdisciplinary Program Kent State University Kent OH 44242 USA Department of Ophthalmology and Visual Science and Department of Electrical and Computer Engineering Ohio State University Columbus OH 43212 USA Materials and Manufacturing Directorate Air Force Research Laboratory Wright-Patterson AFB OH 45433 USA

Adding colloidal nanoparticles into liquid‐crystal media has become a promising pathway either to enhance or to introduce novel properties for improved device performance. Here we designed and synthesized new colloidal hybrid silica nanoparticles passivated with a mesogenic monolayer on the surface to facilitate their organo‐solubility and compatibility in a liquid‐crystal host. The resulting nanoparticles were identified by 1 H NMR spectroscopy, TEM, TGA, and UV/Vis techniques, and the hybrid nanoparticles were doped into a dual‐frequency cholesteric liquid‐crystal host to appraise both their compatibility with the host and the effect of the doping concentration on their electro‐optical properties. Interestingly, the silica‐nanoparticle‐doped liquid‐crystalline nanocomposites were found to be able to dynamically self‐organize into a helical configuration and exhibit multi‐stability, that is, homeotropic (transparent), focal conic (opaque), and planar states (partially transparent), depending on the frequency applied at sustained low voltage. Significantly, a higher contrast ratio between the transparent state and scattering state was accomplished in the nanoparticle‐embedded liquid‐crystal systems.

关键词： Einstellbare Transparenz Frequenzabhängigkeit Helikale Überstrukturen Flüssigkristalle Silika-Nanopartikel

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Geometry-guided colloidal interactions and self-tiling of elastic dipoles formed by truncated pyramid particles in liquid crystals

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Physical Review E 2015年第4期91卷 040501(R)-040501(R)页

作者： Bohdan Senyuk Qingkun Liu Ephraim Bililign Philip D. Nystrom Ivan I. Smalyukh Department of Physics University of Colorado at Boulder Boulder Colorado 80309 USA Department of Electrical Computer and Energy Engineering University of Colorado at Boulder Boulder Colorado 80309 USA Liquid Crystals Materials Research Center and Materials Science and Engineering Program University of Colorado at Boulder Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado at Boulder Boulder Colorado 80309 USA

The progress of realizing colloidal structures mimicking natural forms of organization in condensed matter is inherently limited by the availability of suitable colloidal building blocks. To enable new forms of crystalline and quasicrystalline self-organization of colloids, we develop truncated pyramidal particles that form nematic elastic dipoles with long-range electrostaticlike and geometry-guided low-symmetry short-range interactions. Using a combination of nonlinear optical imaging, laser tweezers, and video microscopy, we characterize colloidal pair interactions and demonstrate unusual forms of self-tiling of these particles into crystalline, quasicrystalline, and other arrays. Our findings are explained using an electrostatics analogy along with liquid crystal elasticity and symmetry breaking considerations, potentially expanding photonic and electro-optic applications of colloids.

关键词： LIQUID crystals RESEARCH MOLECULAR interactions ELASTICITY QUASICRYSTALS BROKEN symmetry (Physics) COLLOIDAL crystals

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Assistive robotic manipulation through shared autonomy and a Body-Machine Interface

Assistive robotic manipulation through shared autonomy and a...

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IEEE International Conference on Rehabilitation Robotics (ICORR)

作者： Siddarth Jain Ali Farshchiansadegh Alexander Broad Farnaz Abdollahi Ferdinando Mussa-Ivaldi Brenna Argall Department of Electrical Engineering and Computer Science Northwestern University Evanston IL USA Sensory Motor and Performance Program Rehabilitation Institute of Chicago Chicago IL USA Department of Biomedical Engineering Northwestern University Evanston IL USA Department of Physiology Northwestern University Chicago IL USA Department of Physical Medicine and Rehabilitation Northwestern University Chicago IL USA

ISBN: (纸本)9781479918096

Assistive robotic manipulators have the potential to improve the lives of people with motor impairments. They can enable individuals to perform activities such as pick-and-place tasks, opening doors, pushing buttons, and can even provide assistance in personal hygiene and feeding. However, robotic arms often have more degrees of freedom (DoF) than the dimensionality of their control interface, making them challenging to use-especially for those with impaired motor abilities. Our research focuses on enabling the control of high-DoF manipulators to motor-impaired individuals for performing daily tasks. We make use of an individual's residual motion capabilities, captured through a Body-Machine Interface (BMI), to generate control signals for the robotic arm. These low-dimensional controls are then utilized in a shared-control framework that shares control between the human user and robot autonomy. We evaluated the system by conducting a user study in which 6 participants performed 144 trials of a manipulation task using the BMI interface and the proposed shared-control framework. The 100% success rate on task performance demonstrates the effectiveness of the proposed system for individuals with motor impairments to control assistive robotic manipulators.

关键词： Manipulators Trajectory Rehabilitation robotics Robot kinematics Aerospace electronics

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Distributed keyword vector representation for document categorization

Distributed keyword vector representation for document categ...

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International Conference on Technologies and Applications of Artificial Intelligence (TAAI)

作者： Yu-Lun Hsieh Shih-Hung Liu Yung-Chun Chang Wen-Lian Hsu Department of Computer Science National Chengchi University Taiwan Social Networks and Human-Centered Computing Program Academia Sinica Taiwan Institute of Information Science Academia Sinica Taiwan Graduate Institute of Electrical Engineering National Taiwan University Taiwan Departmem of Information Management National Taiwan University Taiwan

ISBN: (纸本)9781467396073

In the age of information explosion, efficiently categorizing the topic of a document can assist our organization and comprehension of the vast amount of text. In this paper, we propose a novel approach, named DKV, for document categorization using distributed real-valued vector representation of keywords learned from neural networks. Such a representation can project rich context information (or embedding) into the vector space, and subsequently be used to infer similarity measures among words, sentences, and even documents. Using a Chinese news corpus containing over 100,000 articles and five topics, we provide a comprehensive performance evaluation to demonstrate that by exploiting the keyword embeddings, DKV paired with support vector machines can effectively categorize a document into the predefined topics. Results demonstrate that our method can achieve the best performances compared to several other approaches.

关键词： Computational modeling Manuals

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Ferromagnetic Switching of Knotted Vector Fields in Liquid Crystal Colloids

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Physical Review Letters 2015年第9期115卷 097802-097802页

作者： Qiaoxuan Zhang Paul J. Ackerman Qingkun Liu Ivan I. Smalyukh Department of Physics University of Colorado Boulder Colorado 80309 USA Materials Science and Engineering Program University of Colorado Boulder Colorado 80309 USA Department of Electrical Computer and Energy Engineering University of Colorado Boulder Colorado 80309 USA Liquid Crystal Materials Research Center University of Colorado Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA

We experimentally realize polydomain and monodomain chiral ferromagnetic liquid crystal colloids that exhibit solitonic and knotted vector field configurations. Formed by dispersions of ferromagnetic nanoplatelets in chiral nematic liquid crystals, these colloidal ferromagnets exhibit spontaneous long-range alignment of magnetic dipole moments of individual platelets, giving rise to a continuum of the magnetization field M(r). Competing effects of surface confinement and chirality prompt spontaneous formation and enable the optical generation of localized twisted solitonic structures with double-twist tubes and torus knots of M(r), which exhibit a strong sensitivity to the direction of weak magnetic fields ∼1 mT. Numerical modeling, implemented through free energy minimization to arrive at a field-dependent three-dimensional M(r), shows a good agreement with experiments and provides insights into the torus knot topology of observed field configurations and the corresponding physical underpinnings.

关键词： Chirality Ferromagnetism Colloids Liquid crystals

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Droop control of distributed electric springs for stabilizing future power grid

Droop control of distributed electric springs for stabilizin...

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IEEE General Meeting Power& Energy Society

作者： Chee Kwan Lee Nilanjan Ray Chaudhuri Balarko Chaudhuri Ron Hui Singapore Institute for Neurotechnology Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore National University of Singapore Suzhou Research Institute Suzhou China Large Area Processing Program Singapore Institute of Manufacturing Technology Agency for Science Technology and Research Singapore

This paper describes the droop control method for parallel operation of distributed electric springs for stabilizing ac power grid. It provides a methodology that has the potential of allowing reactive power controllers to work in different locations of the distribution lines of an ac power supply and for these reactive power controllers to support and stabilize the ac mains voltage levels at their respective locations on the distribution lines. The control scheme allows these reactive power controllers to have automatically adjustable voltage references according to the mains voltage levels at the locations of the distribution network. The control method can be applied to reactive power controllers embedded in smart electric loads distributed across the power grid for stabilizing and supporting the ac power supply along the distribution network. The proposed distributed deployment of electric springs is envisaged to become an emerging technology potentially useful for stabilizing power grids with substantial penetration of distributed and intermittent renewable power sources or weakly regulated ac power grid.

关键词： Power grids Reactive power Springs Power supplies Automatic voltage control Electric potential

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Day ahead microgrid optimization: A comparison among different models 1

Day ahead microgrid optimization: A comparison among differe...

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1st International Conference on engineering and Applied sciences Optimization, OPT-i 2014

作者： Bonfiglio, A. Barillari, L. Bendato, I. Bracco, S. Brignone, M. Delfino, F. Pampararo, F. Procopio, R. Robba, M. Rossi, M. Dept of Electrical Naval and ICT Engineering University of Genoa Italy Department of Mechanical Energy Management and Transportation Engineering University of Genoa Italy Department of Computer Science Bioengineering Robotics and Systems Engineering University of Genoa Italy

ISBN: (纸本)9789609999465

The paper deals with a LV grid-connected microgrid located in the Savona Campus of Genoa University and called Smart Polygeneration Microgrid (SPM). Such microgrid is designed to produce electric and thermal energy by means of renewable generation units, cogenerative gas turbines, a storage unit and electric vehicle charging stations. The work focuses its attention on the issue of the microgrid day-ahead power production optimization. Such problem consists in finding the power production profiles for all the dispatchable units in order to optimize a well-defined goal (economical, environmental, etc). This requires to model all the components of the grid in order to define the set of constraints for the optimization procedure. In particular, the way of representing the electric power balance equations plays a crucial role since a trade-off between accuracy and computational efforts is required. Different approaches are presented and tested on the SPM, e.g. complete load flow, modified DC load flow and single bus-bar representation, in order to highlight the peculiarity of the different optimization models obtained and evaluate their impact on computational time, result accuracy and possibility of future experimental validation.

关键词： Electric load flow

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Using Bipartite Graphs for 3D Cardiac Model Retrieval

Using Bipartite Graphs for 3D Cardiac Model Retrieval

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Annual IEEE Symposium on computer-Based Medical Systems

作者： Leila C.C. Bergamasco Hellyan Oliveira Helton Bíscaro Harry Wechsler Fátima L.S. Nunes Polytechnic School - Graduate Program in Electrical Engineering University of Sao Paulo São Paulo SP Brasil Laboratory of Health Informatics Applications University of Sao Paulo São Paulo SP Brasil Department of Computer Science George Mason University Fairfax VA USA

Three-dimensional models have been used to aid medical diagnoses, using images generated by modalities like Magnetic Resonance Imaging. They can provide a more complete vision of objects since their depth is taken into account. Content-based Image Retrieval (CBIR) has also been used to aid the diagnosis. One important step in Three-dimensional CBIR (Model Retrieva) systems is the comparison between two models by using a set of features extracted and stored in a database. In this paper we present a novel method to compare two models, using the Bipartite graphs technique, with the aim to improve the retrieval precision. This technique retrieves 3D medical models of the left ventricle in order to aid the diagnosis of Congestive Heart Failure. Results showed that the novel method improved the precision by 10% when compared to the Similarity Function of Euclidean and Manhattan distance. These results confirmed that bipartite graph techniques can be used to improve the accuracy of Model Retrieval systems.

关键词： Solid modeling Three-dimensional displays Computational modeling Medical diagnostic imaging Feature extraction Bipartite graph

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Economic comparison of deloaded-wind and wind-battery systems

Economic comparison of deloaded-wind and wind-battery system...

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2014 6th Annual IEEE Green Technologies Conference, GREENTECH 2014

作者： Singarao, Venkatesh Yadav Nimmagadda, Sandeep Rao, Vittal Multi-Disciplinary Wind Science and Engineering PhD Program Texas Tech University Lubbock United States Electrical and Computer Engineering Texas Tech University Lubbock United States Department of Electrical and Computer Engineering Texas Tech University Lubbock United States

ISBN: (纸本)9781479939336

With the increasing grid penetration levels of wind power, there is a large need for the energy reserves for grid support during under-frequency conditions. Such energy reserves are created by operating the wind farm at non-optimum/deloaded operating points, as well as through storage of excess energy in Batteries. This paper provides technical and economic analysis of the above strategies and thus provides a case comparison of deloaded wind farm to that of wind-Battery system. A simplified Excel-based Proforma financial model has been developed to perform sensitivity analysis, as well as to obtain the impact of these strategies on the cost of energy. © 2014 IEEE.

关键词： Electric batteries

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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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