检索结果-内蒙古大学图书馆

Liquid crystal Skyrmions can swim

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Ackerman, Paul J. Boyle, Timothy Smalyukh, Ivan I. Department of Physics University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Soft Materials Research Center and Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

Topologically nontrivial field configurations called "baby skyrmions" behave like particles and give origins to the field of skyrmionics that promises racetrack memory and other technological applications. Unraveling the non-equilibrium behavior of such topological solitons is a challenge. We realize baby skyrmions in a chiral liquid crystal and, using numerical modeling and polarized video microscopy, demonstrate electrically driven squirming motion. We reveal the intricate details of non-equilibrium topology-preserving textural changes driving this behavior. Direction of the skyrmion’s motion is robustly controlled in a plane orthogonal to the applied field and can be reversed by varying frequency. Our findings may spur a new paradigm of soliton dynamics in soft matter, with a rich interplay between topology, chirality, and orientational viscoelasticity. Copyright © 2017, The Authors. All rights reserved.

关键词： Topology

Collective behavior of active topological solitons, knotted streamlines, and transport of cargo in liquid crystals

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Sohn, Hayley R.O. Ackerman, Paul J. Boyle, Timothy J. Sheetah, Ghadah H. Fornberg, Bengt Smalyukh, Ivan I. Soft Materials Research Center and Materials Science and Engineering Program University of Colorado BoulderCO80309 United States Department of Physics Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Department of Applied Mathematics University of Colorado BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

Active colloids and liquid crystals are capable of locally converting the macroscopically-supplied energy into directional motion and promise a host of new applications, ranging from drug delivery to cargo transport at the mesoscale. Here we uncover how topological solitons in liquid crystals can locally transform electric energy to translational motion and allow for the transport of cargo along directions dependent on frequency of the applied electric field. By combining polarized optical video microscopy and numerical modeling that reproduces both the equilibrium structures of solitons and their temporal evolution in applied fields, we uncover the physical underpinnings behind this reconfigurable motion and study how it depends on the structure and topology of solitons. We show that, unexpectedly, the directional motion of solitons with and without the cargo arises mainly from the asymmetry in rotational dynamics of molecular ordering in liquid crystal rather than from the asymmetry of fluid flows, as in conventional active soft matter systems. Copyright © 2017, The Authors. All rights reserved.

关键词： Solitons

Potential Fluctuations at Low Temperatures in Mesoscopic-Scale SmTiO3/SrTiO3/SmTiO3 Quantum Well Structures

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Hardy, Will J. Isaac, Brandon Marshall, Patrick Mikheev, Evgeny Zhou, Panpan Stemmer, Susanne Natelson, Douglas Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX United States Materials Department University of California Santa BarbaraCA United States Department of Physics and Astronomy Rice University HoustonTX United States Department of Electrical and Computer Engineering Rice University HoustonTX United States Department of Materials Science and Nanoengineering Rice University HoustonTX United States

Heterointerfaces of SrTiO3 with other transition metal oxides make up an intriguing family of systems with a bounty of coexisting and competing physical orders. Some examples, such as LaAlO3/SrTiO3, support a high carrier density electron gas at the interface whose electronic properties are determined by a combination of lattice distortions, spin-orbit coupling, defects, and various regimes of magnetic and charge ordering. Here, we study electronic transport in mesoscale devices made with heterostructures of SrTiO3 sandwiched between layers of SmTiO3, in which the transport properties can be tuned from a regime of Fermi-liquid like resistivity (ρ ∝ T2) to a non-Fermi liquid (ρ ∝ T5/3) by controlling the SrTiO3 thickness. In mesoscale devices at low temperatures, we find unexpected voltage fluctuations that grow in magnitude as T is decreased below 20 K, are suppressed with increasing contact electrode size, and are independent of the drive current and contact spacing distance. Magnetoresistance fluctuations are also observed, which are reminiscent of universal conductance fluctuations but not entirely consistent with their conventional properties. Candidate explanations are considered, and a mechanism is suggested based on mesoscopic temporal fluctuations of the Seebeck coefficient. An improved understanding of charge transport in these model systems, especially their quantum coherent properties, may lead to insights into the nature of transport in strongly correlated materials that deviate from Fermi liquid theory. Copyright © 2017, The Authors. All rights reserved.

关键词： Rare earths

Minimizing thin film thickness in TiN coatings using genetic algorithms

学校读者我要写书评

暂无评论

AIP Conference Proceedings 2018年第1期2016卷

作者： M. I. Jarrah A. S. M. Jaya M. A. Azam M. R. Muhamad H. Akbar 1Faculty of Information and Communication Technology Universiti Teknikal Malaysia Melaka (UTeM) Hang Tuah Jaya 76100 Durian Tunggal Melaka Malaysia 2Faculty of Manufacturing Engineering Universiti Teknikal Malaysia Melaka (UTeM) Hang Tuah Jaya 76100 Durian Tunggal Melaka Malaysia 3Computer Science Department BINUS Graduate Program-Master of Computer Science Bina Nusantara University Jakarta Indonesia 11480

Optimization of coating parameters is important in the machining process, as an optimized coating layer enhances efficient machining result by providing high wear resistance, saving time and effort, reducing cost, increasing productivity and leading to extend tool life for better surface finish. In terms of tool wear resistance, tools with suitable film coating are forty times better than uncoated tools. Cutting tools are usually coated by Titanium Nitride (TiN), since it has properties such as resistance to wear and hardness resulting in increased cutting performance. Genetic algorithms (GAs) belong to the powerful artificial intelligence optimization family of evolutionary algorithm-based metaheuristic techniques. Since their inception, they have been successfully applied in numerous areas of industrial sectors as material design, tools coating and cutting, alloy design, and so on. In this research work, predicting thin film coating thickness of titanium nitride (TiN) on tungsten carbide (WC) inserts is presented. First, (WC) inserts were coated by TiN in different conditions using Physical Vapor Deposition (PVD), and the surface profilometer was used to measure thickness of the WC coated specimens. Second, Response Surface Methodology (RSM) was used to generate the objective function which represents the process parameters and coating thickness. Third, using a fitness function model, GAs were established to optimize the thickness value of TiN layer with respect to changes in three process parameters, namely Nitrogen gas pressure (N2), Argon gas pressure (Ar), and Turntable Speed (TT). Finally, for performance measurement, three real experimental tests were carried out in terms of Prediction Interval (PI) and Residual Error (e) to validate the RSM model. The actual coating thickness of validation data fell within the 95% (PI) and the (e) values percentage were very low. In terms of optimization, GAs is capable optimizing thickness better than the average experimen

关键词：

A case study in effective education-to-workforce pipelining: An advanced manufacturing and innovation academy 123

学校读者我要写书评

暂无评论

A case study in effective education-to-workforce pipelining:...

123rd ASEE Annual Conference and Exposition

作者： Agarwala, Ranjeet McClung, William Juhling Mohammed, Tijjani White, David M. Mehta, Merwan B. Linn, Jimmy Bill Omar, Tamer East Carolina University Department of Technology Systems GreenvilleNC United States Pitt County Robotics AuroraNC United States East Carolina University College of Engineering and Technology United States East Carolina University College of Technology and Computer Science United States

An advanced manufacturing and innovation academy (AMIA) had been implemented to engage talented young people in the community and connect them with regional advanced manufacturing careers and related entrepreneurial activities. College professors and administrators used collaborative educational approaches to integrate advanced manufacturing pedagogy with robotics, digital manufacturing, and 3D printing with the community students. A tour to a local advanced manufacturing facility was conducted to broaden participants' understanding of advanced manufacturing through direct examples of the themes of the academy. This paper covers the first year of AMIA (a work in progress) and details the background and motivation of the academy. Goals, educational components, community partners and process implemented in year one of the AMIA is discussed. Interim assessment results, success, and lessons learned based on feedback of the participants is covered. Conclusions and next steps for AMIA year 2016 are discussed. This is work in progress paper and authors plan to follow up with detailed assessment results in year two of this academy. © American Society for engineering Education, 2016.

关键词：

Machine vision system for 3D plant phenotyping

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Chaudhury, Ayan Ward, Christopher Talasaz, Ali Ivanov, Alexander G. Brophy, Mark Grodzinski, Bernard Hüner, Norman P.A. Patel, Rajni V. Barron, John L. Department of Computer Science University of Western Ontario Canada Canadian Surgical Technologies & Advanced Robotics University of Western Ontario Canada Stryker Mako Surgical Corporation 2555 Davie Rd Fort LauderdaleFL33317 United States Institute of Biophysics & Biomedical Engineering Bulgarian Academy of Sciences Sofia Bulgaria Department of Biology Biotron Centre for Experimental Climate Change Research University of Western Ontario Canada Department of Plant Agriculture University of Guelph Canada

Machine vision for plant phenotyping is an emerging research area for producing high throughput in agriculture and crop science applications. Since 2D based approaches have their inherent limitations, 3D plant analysis is becoming state of the art for current phenotyping technologies. We present an automated system for analyzing plant growth in indoor conditions. A gantry robot system is used to perform scanning tasks in an automated manner throughout the lifetime of the plant. A 3D laser scanner mounted as the robot's payload captures the surface point cloud data of the plant from multiple views. The plant is monitored from the vegetative to reproductive stages in light/dark cycles inside a controllable growth chamber. An efficient 3D reconstruction algorithm is used, by which multiple scans are aligned together to obtain a 3D mesh of the plant, followed by surface area and volume computations. The whole system, including the programmable growth chamber, robot, scanner, data transfer and analysis is fully automated in such a way that a naive user can, in theory, start the system with a mouse click and get back the growth analysis results at the end of the lifetime of the plant with no intermediate intervention. As evidence of its functionality, we show and analyze quantitative results of the rhythmic growth patterns of the dicot Arabidopsis thaliana(L.), and the monocot barley (Hordeum vulgare L.) plants under their diurnal light/dark cycles. Copyright © 2017, The Authors. All rights reserved.

关键词： Scanning

Diversity of knot solitons in liquid crystals manifested by linking of preimages in torons and hopfions

学校读者我要写书评

暂无评论

arXiv 2017年

作者： Ackerman, P.J. Smalyukh, I.I. Department of Physics University of Colorado BoulderCO80309 United States Department of Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States University of Colorado Liquid Crystal Materials Research Center and Materials Science and Engineering Program BoulderCO80309 United States Renewable and Sustainable Energy Institute National Renewable Energy Laboratory University of Colorado BoulderCO80309 United States

Topological solitons are knots in continuous physical fields classified by non-zero Hopf index values. Despite arising in theories that span many branches of physics, from elementary particles to condensed matter and cosmology, they remain experimentally elusive and poorly understood. We introduce a method of experimental and numerical analysis of such localized structures in liquid crystals that, similar to the mathematical Hopf maps, relates all points of the medium’s order parameter space to their closed-loop preimages within the three-dimensional solitons. We uncover a surprisingly large diversity of naturally occurring and laser-generated topologically nontrivial solitons with differently knotted nematic fields, which previously have not been realized in theories and experiments alike. We discuss the implications of the liquid crystal’s non-polar nature on the knot soliton topology and how the medium’s chirality, confinement and elastic anisotropy help to overcome the constrains of the Hobart-Derrick theorem, yielding static three-dimensional solitons without or with additional defects. Our findings will establish chiral nematics as a model system for experimental exploration of topological solitons and may impinge on understanding of such nonsingular field configurations in other branches of physics, as well as may lead to technological applications Copyright © 2017, The Authors. All rights reserved.

关键词： Solitons

Flocking of Mobile Robots by Bounded Feedback

学校读者我要写书评

暂无评论

Flocking of Mobile Robots by Bounded Feedback

IEEE International Conference on Automation science and engineering

作者： Thanh-Trung Han Hung Manh La Bach Hoang Dinh Faculty of Electrical and Electronics Engineering Ton Duc Thang University Advanced Robotics and Automation (ARA) Lab Department of Computer Science and Engineering University of Nevada

ISBN: (纸本)9781509024100

This paper addresses the problem of flocking of mobile robots by bounded feedback. A control problem is formulated with the multiple goals: velocity consensus, collision avoidance, and cohesion maintenance. The flocking protocol is then obtained by means of control design. Particularly, a Lyapunov-like function is presented, the velocity control is designed to achieve coordination and linear speed consensus, and the steering control is designed for consensus on orientation. The convergence is verified via Barbalat's lemma. Simulation results with a group of mobile robots are presented to show the effectiveness of the proposed flocking control.

关键词： FLOCKING Mobile robots Velocity control steering control Bounded Feedback

Cochlear tuning… of mice and men

学校读者我要写书评

暂无评论

AIP Conference Proceedings 2018年第1期1965卷

作者： Shirin Farrahi Roozbeh Ghaffari Jonathan B. Sellon Hideko H. Nakajima Dennis M. Freeman 1Research Laboratory of Electronics MIT Cambridge Massachusetts USA 2Department of Electrical Engineering and Computer Science MIT Cambridge Massachusetts USA 3Harvard-MIT Program in Health Sciences and Technology Cambridge Massachusetts USA 4Department of Otolaryngology Harvard Medical School and Massachusetts Eye and Ear Boston Massachusetts USA

It has been suggested that humans discriminate different frequency sounds with greater selectivity than other mammals. However, mechanisms that could underlie higher frequency selectivity in humans are unclear. Recent studies show that the tectorial membrane (TM) supports longitudinally propagating waves, and the spread of excitation of these TM waves has been implicated in controlling the tuning properties in a mutant mouse model of hearing. Here we compare TM morphology and waves in humans and mice and show that despite some differences in morphology, the spread of excitation of TM waves is similar in spatial extent. However, the cochlear maps of humans and mice differ significantly, with similar cochlear distances mapping to a narrower range of best frequencies in humans than in mice. By coupling different frequency ranges, TM waves could contribute to differences in frequency tuning in mammals, with the smaller human range of frequencies corresponding to sharper frequency tuning.

关键词：