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arXiv 2017年

作者： Zhang, Linfeng Wang, Han Weinan, E. Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Institute of Applied Physics and Computational Mathematics Fenghao East Road 2 Beijing100094 China CAEP Software Center for High Performance Numerical Simulation Huayuan Road 6 Beijing100088 China Department of Mathematics and Program in Applied and Computational Mathematics Princeton University PrincetonNJ08544 United States Beijing Institute of Big Data Research Beijing100871 China

A new approach for efficiently exploring the configuration space and computing the free energy of large atomic and molecular systems is proposed, motivated by an analogy with reinforcement learning. There are two major components in this new approach. Like metadynamics, it allows for an efficient exploration of the configuration space by adding an adaptively computed biasing potential to the original dynamics. Like deep reinforcement learning, this biasing potential is trained on the fly using deep neural networks, with data collected judiciously from the exploration and an uncertainty indicator from the neural network model playing the role of the reward function. Parameterization using neural networks makes it feasible to handle cases with a large set of collective variables. This has the potential advantage that selecting precisely the right set of collective variables has now become less critical for capturing the structural transformations of the system. The method is illustrated by studying the full-atom, explicit solvent models of alanine dipeptide and tripeptide, as well as the system of a polyalanine-10 molecule with 20 collective variables. Copyright © 2017, The Authors. All rights reserved.

关键词： Wave functions

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ALBEDOS, EQUILIBRIUM TEMPERATURES, AND SURFACE TEMPERATURES OF HABITABLE PLANETS

arXiv

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arXiv 2018年

作者： Del Genio, Anthony D. Kiang, Nancy Y. Way, Michael J. Amundsen, David S. Sohl, Linda E. Fujii, Yuka Chandler, Mark Aleinov, Igor Colose, Christopher M. Guzewich, Scott D. Kelley, Maxwell NASA Goddard Institute for Space Studies 2880 Broadway New YorkNY10025 United States Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10027 United States Center for Climate Systems Research Columbia University New YorkNY10027 United States Earth-Life Science Institute Tokyo Institute of Technology Ookayama Meguro Tokyo152-8550 Japan NASA Postdoctoral Program Goddard Institute for Space Studies New YorkNY10025 United States NASA Goddard Space Flight Center GreenbeltMD20771 United States SciSpace LLC 2880 Broadway New YorkNY10025 United States

The potential habitability of known exoplanets is often categorized by a nominal equilibrium temperature assuming a Bond albedo of either ~0.3, similar to Earth, or 0. As an indicator of habitability, this leaves much to be desired, because albedos of other planets can be very different, and because surface temperature exceeds equilibrium temperature due to the atmospheric greenhouse effect. We use an ensemble of 3-dimensional general circulation model simulations to show that for a range of habitable planets, much of the variability of Bond albedo, equilibrium temperature, and even surface temperature can be predicted with useful accuracy from incident stellar flux and stellar temperature, two known external parameters for every confirmed exoplanet. Earth’s Bond albedo is near the minimum possible for habitable planets orbiting G stars, because of increasing contributions from clouds and sea ice/snow at higher and lower instellations, respectively. For habitable M star planets, Bond albedo is usually lower than Earth’s because of near-IR H2O absorption, except at high instellation where clouds are important. We apply the relationships derived from this behavior to several known exoplanets to derive zeroth-order estimates of their potential habitability. More expansive multivariate statistical models that include currently non-observable parameters suggest that greenhouse gas variations could account for significant variance in albedo and surface temperature, while orbital and surface features can have significant but not clearly consistent effects. We discuss how emerging information from global climate models might resolve some degeneracies and help focus scarce observing resources on the most promising planets. Copyright © 2018, The Authors. All rights reserved.

关键词： Surface properties

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Study on Penetration of 4-MeV Electron Beam in Natural Rubber Latex

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Journal of physics: Conference Series 2018年第1期1144卷

作者： K Kosaentor P Apiwattanakul S Rimjaem Plasma and Beam Physics Research Facility Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai 50200 Thailand Master Degree Program in Applied Physics Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai 50200 Thailand Thailand Center of Excellence in Physics Commission on Higher Education Bangkok 10400 Thailand Research Center in Physics and Astronomy Chiang Mai University Chiang Mai 50200 Thailand

Vulcanization with electron beam irradiation provides unique and high efficient processing for natural rubber latex. It is one of very interesting and effective industrial applications of particle accelerators. A radio-frequency (RF) linear accelerator (linac) and electron beam irradiation system have been developed for natural rubber vulcanization at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam physics (PBP) Research Facility, Chiang Mai University (CMU). This accelerator will be able to produce electron beams with maximum energy up to about 4 MeV. In this research, we used a Monte Carlo simulation program called GEANT4 to study transportation of 4-MeV electron beam with Gaussian transverse distribution through a vacuum window, an air gap and natural rubber latex. The vacuum window is made of 50-micron titanium foil and the natural rubber was placed 18 cm downstream the foil exit. Simulations of electron depth dose and transverse distribution in these media were conducted. In addition, calculation on the irradiation throughput was performed. The study results revealed that for the electron beam with Gaussian transverse distribution and an average energy of 4.06 MeV, the irradiation area should be 2.8 mm×2.8 mm with the depth of 8 mm. With this condition, the irradiation time of 0.02 second will provide the dose of at least 50 kGy per irradiated point, which is enough for the rubber vulcanization process. The overall irradiation throughput rate is 6.865 kg/hr.

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Simulations and measurements of the dipole magnet using in the 4-MeV electron spectrometer

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Journal of physics: Conference Series 2018年第1期1144卷

作者： E Kongmon P Wongkummoon S Rimjaem Plasma and Beam Physics Research Facility Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai 50200 Thailand Master Degree Program in Applied Physics Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai 50200 Thailand Thailand Center of Excellence in Physics Commission on Higher Education Bangkok 10400 Thailand Research Center in Physics and Astronomy Chiang Mai University Chiang Mai 50200 Thailand

A dipole magnet is one of important components in particle accelerators. It can be used to transport a charged particle beam with desired deflecting angle and direction. Moreover, it is often utilized as a part of an energy spectrometer. This research focuses on simulations and measurements of the dipole magnet, which will be used to measure the electron beam energy produced from the 4-MeV radio-frequency (RF) linear accelerator (linac) for natural rubber vulcanization at the PBP-CMU Electron Linac Laboratory of the Plasma and Beam physics (PBP) Research Facility in Chiang Mai University (CMU). The research activities are divided into three main parts. The first part focuses on three-dimensional (3D) simulation of the dipole magnet by using the RADIA program. The 3D field map of the magnetic field can be derived from the RADIA model. The second past is the magnetic field measurements of the magnet after the construction. The maximum magnetic field of 248.6 mT can be obtained with an excitation current of 3 A. The last part focuses on the electron beam dynamic study by using the program called ASTRA to track the particles though the 3D magnetic field distribution. The simulation data provides six-dimensional coordinates of the particles at the considered position downstream the dipole magnet. The optimal bending angle of the 4-MeV electron beam in the magnetic field of 0.22 T is 50° with an energy spread of 0.827 MeV.

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Seasonal Variation of the Monthly Efficiencies of Thin Film PV Modules

Seasonal Variation of the Monthly Efficiencies of Thin Film ...

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International Renewable and Sustainable Energy Conference (IRSEC)

作者： Talat Özden Raşit Turan Bülent Gültekin Akmoğlu Department of Electrical and Electronics Engineering Gümüşhane University Günüşhane Turkey Department of Physics METU Ankara Turkey Earth System Science Program Graduate School of Natural and Applied Sciences Ankara Turkey

Outdoor testing of solar photovoltaic (PV) modules must be carried out at different climates as PV power plants nowadays are installed and continues to be installed in many countries. Present study is outdoor testing results and analyses of 5 thin film modules in Ankara, Turkey. The analyses are carried out using monthly efficiencies of the modules that are derived using the energy yield and input. The average efficiencies of the CIS, CIGS and μc-Si/a-Si thin film modules are. We present the monthly and average efficiencies and discuss their variations with the parameter: input, ambient temperature and relative humidity. We also carried out seasonal analyses using Pearson's correlation coefficient and find out that the efficiencies are differently dependent on the above mentioned parameters. This arose a new open question on differentiation of the strength of the effect of each parameter on the monthly efficiencies.

关键词： Testing Correlation coefficient Correlation Meteorology Springs Solar energy

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Electrical tuning of the polarization state of light using graphene-integrated anisotropic metasurfaces

Electrical tuning of the polarization state of light using g...

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作者： Dutta-Gupta, Shourya Dabidian, Nima Kholmanov, Iskandar Belkin, Mikhail A. Shvets, Gennady Department of Physics Center for Nano and Molecular Science and Technology University of Texas at Austin AustinTX78712 United States Department of Mechanical Engineering Materials Science Program University of Texas at Austin AustinTX78712 United States Department of Electrical and Computer Engineering Microelectronics Research Center University of Texas at Austin 10100 Burnet Road AustinTX78758 United States CNR-INO Sensor Lab University of Brescia via Branze 45 Brescia25123 Italy School of Applied and Engineering Physics Cornell University IthacaNY14853 United States

Plasmonic metasurfaces have been employed for moulding the flow of transmitted and reflected light, thereby enabling numerous applications that benefit from their ultra-thin sub-wavelength format. Their appeal is further enhanced by the incorporation of active electro-optic elements, paving the way for dynamic control of light's properties. In this paper, we realize a dynamic polarization state generator using a graphene-integrated anisotropic metasurface (GIAM) that converts the linear polarization of the incident light into an elliptical one. This is accomplished by using an anisotropic metasurface with two principal polarization axes, one of which possesses a Fano-type resonance. A gate-controlled single-layer graphene integrated with the metasurface was employed as an electro-optic element controlling the phase and intensity of light polarized along the resonant axis of the GIAM. When the incident light is polarized at an angle to the resonant axis of the metasurface, the ellipticity of the reflected light can be dynamically controlled by the application of a gate voltage. Thus accomplished dynamic polarization control is experimentally demonstrated and characterized bymeasuring the Stokes polarization parameters. Large changes of the ellipticity and the tilt angle of the polarization ellipse are observed. Our measurements show that the tilt angle can be changed from positive values through zero to negative values while keeping the ellipticity constant, potentially paving the way to rapid ellipsometry and other characterization techniques requiring fast polarization shifting. This article is part of the themed issue 'New horizons for nanophotonics'. © 2017 The Author(s) Published by the Royal Society. All rights reserved.

关键词： Graphene

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On the Yearly Performance of a Bifacial PV Module in Central Anatolia - Turkey

On the Yearly Performance of a Bifacial PV Module in Central...

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International Renewable and Sustainable Energy Conference (IRSEC)

作者： Talat Özden Raşit Turan Bülent Gültekin Aklnoğlu Department of Electrical and Electronics Engineering Gumüshane University Gumushane Turkey Department of Physics Middle East Technical University METU Ankara Turkey Earth System Science Program Graduate School of Natural and Applied Sciences Ankara Turkey

With the tremendous increase in the photovoltaic (PV) power plants world-wide remarkable decreases in their installation prices per watt are attained mainly due to economic scale effect. This brings questioning to increase their energy yields by considering any possible way like fabricating bifacial solar modules. Present study is on the performance analysis of a bifacial PV module using one-year outdoor testing results in Ankara-Turkey. The module performed very well and reached a specific yield value of 1750 kWh/kWp. This value for Central Anatolia region is well above the values predicted (and suggested) by the local authorities. The efficiency and performance ratio variation with respect to ambient and module temperature are obtained. The calculated dependence of efficiency on the module temperature is found to be η = -0.073T mod +18.05, and the maximum measured module temperature is about 70 °C. The results show that the bifacial modules have the potential to replace the mono facial modules that are now dominating the PV market.

关键词： Testing Temperature measurement Temperature dependence MONOS devices Meteorology Solar energy

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Genetic and neuroanatomical support for functional brain network dynamics in epilepsy

arXiv

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arXiv 2018年

作者： Reddy, Pranav G. Betzel, Richard F. Khambhati, Ankit N. Shah, Preya Kini, Lohith Litt, Brian Lucas, Timothy H. Davis, Kathryn A. Bassett, Danielle S. Department of Bioengineering School of Engineering and Applied Sciences University of Pennsylvania PhiladelphiaPA19104 United States Department of Psychological & Brain Sciences Indiana University BloomingtonIN47405 United States Cognitive Science Program Indiana University BloomingtonIN47405 United States Department of Neurological Surgery University of California San FranciscoCA94122 United States Department of Neurology Perelman School of Medicine University of Pennsylvania PhiladelphiaPA19104 United States Department of Neurosurgery Perelman School of Medicine University of Pennsylvania PhiladelphiaPA19104 United States Department of Electrical & Systems Engineering School of Engineering and Applied Sciences University of Pennsylvania PhiladelphiaPA19104 United States Department of Physics & Astronomy School of Arts & Sciences University of Pennsylvania PhiladelphiaPA19104 United States

Focal epilepsy is a devastating neurological disorder that affects an overwhelming number of patients worldwide, many of whom prove resistant to medication. The efficacy of current innovative technologies for the treatment of these patients has been stalled by the lack of accurate and effective methods to fuse multimodal neuroimaging data to map anatomical targets driving seizure dynamics. Here we propose a parsimonious model that explains how large-scale anatomical networks and shared genetic constraints shape inter-regional communication in focal epilepsy. In extensive ECoG recordings acquired from a group of patients with medically refractory focal-onset epilepsy, we find that ictal and preictal functional brain network dynamics can be accurately predicted from features of brain anatomy and geometry, patterns of white matter connectivity, and constraints complicit in patterns of gene coexpression, all of which are conserved across healthy adult populations. Moreover, we uncover evidence that markers of non-conserved architecture, potentially driven by idiosyncratic pathology of single subjects, are most prevalent in high frequency ictal dynamics and low frequency preictal dynamics. Finally, we find that ictal dynamics are better predicted by white matter features and more poorly predicted by geometry and genetic constraints than preictal dynamics, suggesting that the functional brain network dynamics manifest in seizures rely on - and may directly propagate along - underlying white matter structure that is largely conserved across humans. Broadly, our work offers insights into the generic architectural principles of the human brain that impact seizure dynamics, and could be extended to further our understanding, models, and predictions of subject-level pathology and response to intervention. Copyright © 2018, The Authors. All rights reserved.

关键词： Neurology

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Corrigendum to "Multiband rabi antenna using nest microstrip add-drop filter (NMADF) for relativistic sensing applications" [Heliyon 9(2) (February 2023) e13611]

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Heliyon 2023年第7期9卷 e16846页

作者： Somchat Sonasang M Jamsai M A Jalil N T Pham K Ray Niwat Angkawisittpan Preecha Yupapin Sarawoot Boonkirdram Martha Alicia Palomino-Ovando Miller Toledo-Solano Khashayar Misaghian J E Lugo Electronic Technology Faculty of Industrial Technology Nakon Phanom University Nakon Phanom 48000 Thailand. Department of Electrical Engineering Faculty of Industry and Technology Rajamagala University of Technology Isan Sakon Nakhon Campus Sakon Nakhon 47160 Thailand. Department of Physics Universiti Teknologi Malaysia 81310 Skuda Johor Malaysia. Institute for Computational Science Ton Duc Thang University Ho Chi Minh City Viet Nam. Amity School of Applied Sciences Amity University Rajasthan Jaipur India. Facultad de CienciasFisico-Matematicas Benemérita Universidad Autónoma de Puebla Av. San Claudio y AV. 18 sur Col. San Manuel Ciudad Universitaria Pueble Pue 72570 Mexico. Faubert Lab Ecole d'optométrie Université de Montréal Montréal QC H3T1P1 Canada. Research Unit for Computational Electromagnetics and Optical Systems Faculty of Engineering Mahasarakham University Maha Sarakham 44150 Thailand. Department of Electrical Technology School of Industrial Technology Sakonnakhon Technical College Institute of Vocational Education Northeastern 2 Sakonnakhon 47000 Thailand. Program of Electrical and Electronics Faculty of Industrial Technology Sakon Nakhon Rajabhat University 680 Nittayo Mueang Sakon Nakhon 47000 Thailand. CONACYT-Facultad de CienciasFisico-Matematicas Benemérita Universidad Autónoma de Pueble Av. San Claudio y Av. 18 sur Col. San Manuel Ciudad Universitaria Puebla Pue 72570 Mexico. Faubert Lab School of Optometry Université de Montréal Montréal QC H3T1P1 Canada. Sage-Sentinel Smart Solutions 1919-1 Tancha Onna-son Kunigamigun Okinawa 904-0495 Japan.

[This corrects the article DOI: 10.1016/***.2023.e13611.].

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Structural and electronic properties of MgGe x Sn(1-x)N2 semiconductors: The density functional theory investigation

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Journal of physics: Conference Series 2018年第1期1144卷

作者： K Kanchiang T Cheiwchanchamnangij Y Laosiritaworn S Pramchu A P Jaroenjittichai Program in Applied Physics Faculty of Science Maejo University Chiang Mai 50290 Thailand Department of Physics Faculty of Science Mahidol University Bangkok 10400 Thailand Department of Physics and Materials Science Faculty of Science Chiang Mai University Chiang Mai 50200 Thailand Center of Excellence in Materials Science and Technology Chiang Mai University Chiang Mai 50200 Thailand

In this work, we studied the lattice dynamics and electronic structures of nitride semiconductors MgGe x Sn(1-x)N2, where x = 0, 0.25, 0.5, 0.75 and 1, using density functional theory (DFT) calculations. The core electronic states were represented via ultrasoft pseudo-potentials. From the results, lattice constants of MgGe x Sn(1-x)N2 compounds decrease with increasing Ge concentrations according to the Vegard's law, where the lattice bowing coefficients p a , p b and p c are 0.043, –0.019 and 0.087 Å respectively. For the electronic band structure, the N-p dominated valence band was found to shift down and IV-s dominated conduction band moves up with increasing the Ge concentrations. In addition, the energy gap bowing coefficients p e is 0.916 eV.

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