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Thermal transport at a nanoparticle-water interface: A molecular dynamics and continuum modeling study

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arXiv 2019年

作者： Rajabpour, Ali Seif, Roham Arabha, Saeed Heyhat, Mohammad Mahdi Merabia, Samy Hassanali, Ali Advanced Simulation and Computing Laboratory Imam Khomeini International University Qazvin Iran Dipartimento di Energia Politecnico di Milano Via Lambruschini 4 Milano20156 Italy Faculty of Mechanical Engineering Tarbiat Modares University Tehran*** Iran Institut Lumière Matière UMR 5306 CNRS Université Claude Bernard Lyon 1 Lyon France Trieste Italy

Heat transfer between a silver nanoparticle and surrounding water has been studied using molecular dynamics (MD) simulations. The thermal conductance (Kapitza conductance) at the interface between a nanoparticle and surrounding water has been calculated using four different approaches: transient with/without temperature gradient (internal thermal resistance) in the nanoparticle, steady-state non-equilibrium and finally equilibrium simulations. The results of steady-state non-equilibrium and equilibrium are in agreement but differ from the transient approach results. MD simulations results also reveal that in the quenching process of a hot silver nanoparticle, heat dissipates into the solvent over a length-scale of ~ 2nm and over a timescale of less than 5ps. By introducing a continuum solid-like model and considering a heat conduction mechanism in water, it is observed that the results of the temperature distribution for water shells around the nanoparticle agree well with MD results. It is also found that the local water thermal conductivity around the nanoparticle is greater by about 50 percent than that of bulk water. These results have important implications for understanding heat transfer mechanisms in nanofluids systems and also for cancer photothermal therapy, wherein an accurate local description of heat transfer in an aqueous environment is crucial. Copyright © 2019, The Authors. All rights reserved.

关键词： Molecular dynamics

Aggregating multiple types of complex data in stock market prediction: A model-independent framework

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arXiv 2018年

作者： Wang, Huiwen Lu, Shan Zhao, Jichang School of Economics and Management Beihang University Beijing Advanced Innovation Center for Big Data and Brain Computing Beijing Key Laboratory of Emergency Support Simulation Technologies for City Operations

The increasing richness in volume, and especially types of data in the financial domain provides unprecedented opportunities to understand the stock market more comprehensively and makes the price prediction more accurate than before. However, they also bring challenges to classic statistic approaches since those models might be constrained to a certain type of data. Aiming at aggregating differently sourced information and offering type-free capability to existing models, a framework for predicting stock market of scenarios with mixed data, including scalar data, compositional data (pie-like) and functional data (curve-like), is established. The presented framework is model-independent, as it serves like an interface to multiple types of data and can be combined with various prediction models. And it is proved to be effective through numerical simulations. Regarding to price prediction, we incorporate the trading volume (scalar data), intraday return series (functional data), and investors’ emotions from social media (compositional data) through the framework to competently forecast whether the market goes up or down at opening in the next day. The strong explanatory power of the framework is further demonstrated. Specifically, it is found that the intraday returns impact the following opening prices differently between bearish market and bullish market. And it is not at the beginning of the bearish market but the subsequent period in which the investors’ "fear" comes to be indicative. The framework would help extend existing prediction models easily to scenarios with multiple types of data and shed light on a more systemic understanding of the stock market. Copyright © 2018, The Authors. All rights reserved.

关键词： Forecasting

Toward a resolution of the NN controversy

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arXiv 2021年

作者： Nicholson, Amy Berkowitz, Evan Bulava, John Chang, Chia Cheng Clark, M.A. Hanlon, Andrew D. Hörz, Ben Howarth, Dean Körber, Christopher Lee, Wayne Tai Meyer, Aaron S. Monge-Camacho, Henry Morningstar, Colin Rinaldi, Enrico Vranas, Pavlos Walker-Loud, André Department of Physics and Astronomy University of North Carolina Chapel HillNC27516-3255 United States Intel Corporation Santa ClaraCA95054 United States Physics Division Lawrence Livermore National Laboratory LivermoreCA94550 United States Physics Department University of Michigan Ann ArborMI48109 United States Theoretical Quantum Physics Laboratory RIKEN 2-1 Hirosawa Wako Saitama351-0198 Japan Physics Department Brookhaven National Laboratory UptonNY11973 United States Institut für Theoretische Physik II Ruhr-Universität Bochum BochumD-44780 Germany Department of Physics University of California BerkeleyCA94720 United States Nuclear Science Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States CP3 -Origins Dept. of Mathematics and Computer Science University of Southern Denmark Campusvej 55 Odense M5230 Denmark NVIDIA Corporation Santa ClaraCA95050 United States Department of Statistics Columbia University New YorkNY10027 United States Department of Physics Carnegie Mellon University PittsburghPA15213 United States Institut für Kernphysik Institute for Advanced Simulation Forschungszentrum Jülich Jülich54245 Germany Escuela de Física Universidad de Costa Rica San Pedro San José11501 Costa Rica iTHEMS RIKEN 2-1 Hirosawa Wako Saitama351-0198 Japan Center for Quantum Computing RIKEN 2-1 Hirosawa Wako Saitama351-0198 Japan

Lattice QCD calculations of two-nucleon interactions have been underway for about a decade, but still haven’t reached the pion mass regime necessary for matching onto effective field theories and extrapolating to the physical point. Furthermore, results from different methods, including the use of the Lüscher formalism with different types of operators, as well as the HALQCD potential method, do not agree even qualitatively at very heavy pion mass. We investigate the role that different operators employed in the literature may play on the extraction of spectra for use within the Lüscher method. We first explore expectations from Effective Field Theory solved within a finite volume, for which the exact spectrum may be computed given different physical scenarios. We then present preliminary lattice QCD results for two-nucleon spectra calculated using different operators on a common lattice ensemble. Copyright © 2021, The Authors. All rights reserved.

关键词： Hadrons

Accurate ECG Data Generation with a Simple Generative Adversarial Network

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Journal of Physics: Conference Series 2020年第1期1631卷

作者： Haiyan Wang Zhaoyang Ge Zongmin Wang Collaborative Innovation Centre for Internet Healthcare Zhengzhou University 75 Daxue Road Zhengzhou 450052 China State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou 450003 China Simulation Experiment Centre Zhengzhou University of Aeronautics Zhengzhou 450046 China School of Information Engineering Zhengzhou University Zhengzhou 450001 China

Since ECG data is highly sensitive medical data, the acquisition of ECG data is highly restricted. However, with the increasing demand for ECG big data research, the improvement of computer computing capabilities, and the development of deep learning, the direction of ECG intelligent analysis is facing a serious lack of standard clinical data. In order to generate more precise ECG data, this paper proposes a GAN architecture for generating ECG heartbeat data. The network structure is simple and does not require any domain knowledge. In this paper, the MIT-BIH Arrhythmia database is selected, from which all left bundle branch block heartbeats are selected to form a training dataset. The training process shows that the proposed GAN structure is effective and accurate, and the generated results show that not only the generated simulated ECG heartbeat data is diverse, but also highly similar to the real data.

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Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

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Photonics Research 2018年第3期6卷 157-161页

作者： FAJUN XIAO WUYUN SHANG WEIREN ZHU LEI HAN MALIN PREMARATNE TING MEI JIANLIN ZHAO MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions and Shaanxi Key Laboratory of Optical Information TechnologySchool of ScienceNorthwestern Polytechnical UniversityXi'an 710129China Department of Electronic Engineering Shanghai Jiao Tong UniversityShanghai 200240China Advanced Computing and Simulation Laboratory(AχL) Department of Electrical and Computer Systems Monash UniversityClaytonVlC 3800Australia

We report a method to tune the second harmonic generation(SHG) frequency of a metallic octamer by employing cylindrical vector beams as the excitation. Our method exploits the ability to spatially match the polarization state of excitations with the fundamental target plasmonic modes, enabling flexible control of the SHG resonant *** is found that SHG of the octamer is enhanced over a broad band(400 nm) by changing the excitation from the linearly polarized Gaussian beam to radially and azimuthally polarized beams. More strikingly, when subjected to an azimuthally polarized beam, the SHG intensity of the octamer becomes 30 times stronger than that for the linearly polarized beam even in the presence of Fano resonance.

关键词： SHG Cylindrical vector beam-excited frequency-tunable second harmonic generation in a plasmonic octamer

Tape-time processing: Kinetics and mechanisms of native oxidation of transition metal dichalcogenides ZrSxSe2-x and MoS2

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arXiv 2020年

作者： Jo, Seong Soon Singh, Akshay Yang, Liqiu Tiwari, Subodh C. Hong, Sungwook Krishnamoorthy, Aravind Sales, Maria Gabriela Oliver, Sean M. Fox, Joshua Cavalero, Randal L. Snyder, David W. Vora, Patrick M. McDonnell, Stephen J. Vashishta, Priya Kalia, Rajiv K. Nakano, Aiichiro Jaramillo, Rafael Department of Materials Science and Engineering Massachusetts Institute of Technology CambridgeMA02139 United States Collaboratory for Advanced Computing and Simulation University of Southern California Los AngelesCA90089 United States Department of Physics and Engineering California State University BakersfieldCA93311 United States Department of Materials Science and Engineering University of Virginia CharlottesvilleVA22904 United States Electronic Materials and Devices Department Applied Research Laboratory and 2-Dimensional Crystal Consortium Materials Research Institute Pennsylvania State University University ParkPA16802 United States Department of Physics and Astronomy George Mason University FairfaxVA22030 United States Quantum Materials Center George Mason University FairfaxVA22030 United States

A thorough understanding of the processing and properties of native oxides is essential for designing semiconductor devices. This is no less true for nanomaterials than it is for legacy semiconductors such as silicon, for which control and understanding of the native oxide was a seminal achievement of 20th century materials science. Layered transition metal dichalcogenides nominally have inert, fully-passivated surfaces, but it is well-known that this is an oversimplification and that many TMDs oxidize readily. Here we report on experiments and simulations that reveal the rate and mechanism of oxidation of MoS2 and ZrSxSe2-x alloys in laboratory conditions. We find that MoS2 surfaces are indeed stable, with no oxidation for up to a year exposure. In contrast, ZrSxSe2-x alloys oxidize spontaneously and the oxide growth is not self-limited. Oxidation proceeds by Zr-O bond switching that collapses the van der Waals gaps, and is facilitated by progressive redox transitions of the chalcogen. In contrast, the MoS2 surface remains inert due to energetically-unfavorable oxygen adsorption. Our results provide quantitative and conceptual guidance for designing and processing semiconductor devices based on MoS2 and ZrSxSe2-x, and identify the atomistic-scale mechanisms of bonding and phase transformations in layered materials with competing anions. Copyright © 2020, The Authors. All rights reserved.

关键词： Transition metals

DeePMD-kit v2: A software package for Deep Potential models

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arXiv 2023年

作者： Zeng, Jinzhe Zhang, Duo Lu, Denghui Mo, Pinghui Li, Zeyu Chen, Yixiao Rynik, Marián Huang, Li'ang Li, Ziyao Shi, Shaochen Wang, Yingze Ye, Haotian Tuo, Ping Yang, Jiabin Ding, Ye Li, Yifan Tisi, Davide Zeng, Qiyu Bao, Han Xia, Yu Huang, Jiameng Muraoka, Koki Wang, Yibo Chang, Junhan Yuan, Fengbo Bore, Sigbjørn Løland Cai, Chun Lin, Yinnian Wang, Bo Xu, Jiayan Zhu, Jia-Xin Luo, Chenxing Zhang, Yuzhi Goodall, Rhys E.A. Liang, Wenshuo Singh, Anurag Kumar Yao, Sikai Zhang, Jingchao Wentzcovitch, Renata Han, Jiequn Liu, Jie Jia, Weile York, Darrin M. Weinan, E. Car, Roberto Zhang, Linfeng Wang, Han Laboratory for Biomolecular Simulation Research Institute for Quantitative Biomedicine Department of Chemistry and Chemical Biology Rutgers University PiscatawayNJ08854 United States AI for Science Institute Beijing100080 China DP Technology Beijing100080 China Academy for Advanced Interdisciplinary Studies Peking University Beijing100871 China HEDPS CAPT College of Engineering Peking University Beijing100871 China College of Electrical and Information Engineering Hunan University Changsha China Yuanpei College Peking University Beijing100871 China Program in Applied and Computational Mathematics Princeton University PrincetonNJ08540 United States Department of Experimental Physics Comenius University Mlynská Dolina F2 Bratislava842 48 Slovakia Center for Quantum Information Institute for Interdisciplinary Information Sciences Tsinghua University Beijing100084 China Center for Data Science Peking University Beijing100871 China ByteDance Research Zhonghang Plaza No. 43 North 3rd Ring West Road Haidian District Beijing China College of Chemistry and Molecular Engineering Peking University Beijing100871 China Baidu Inc. Beijing China Key Laboratory of Structural Biology of Zhejiang Province School of Life Sciences Westlake University Zhejiang Hangzhou China Westlake AI Therapeutics Lab Westlake Laboratory of Life Sciences and Biomedicine Zhejiang Hangzhou China Department of Chemistry Princeton University PrincetonNJ08544 United States SISSA Scuola Internazionale Superiore di Studi Avanzati Trieste34136 Italy Laboratory of Computational Science and Modeling Institute of Materials École Polytechnique Fédérale de Lausanne Lausanne1015 Switzerland Department of Physics National University of Defense Technology Hunan Changsha410073 China State Key Lab of Processors Institute of Computing Technology Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China School of Electronics Engineerin

DeePMD-kit is a powerful open-source software package that facilitates molecular dynamics simulations using machine learning potentials (MLP) known as Deep Potential (DP) models. This package, which was released in 2017, has been widely used in the fields of physics, chemistry, biology, and material science for studying atomistic systems. The current version of DeePMD-kit offers numerous advanced features such as DeepPot-SE, attention-based and hybrid descriptors, the ability to fit tensile properties, type embedding, model deviation, Deep Potential - Range Correction (DPRc), Deep Potential Long Range (DPLR), GPU support for customized operators, model compression, non-von Neumann molecular dynamics (NVNMD), and improved usability, including documentation, compiled binary packages, graphical user interfaces (GUI), and application programming interfaces (API). This article presents an overview of the current major version of the DeePMD-kit package, highlighting its features and technical details. Additionally, the article benchmarks the accuracy and efficiency of different models and discusses ongoing developments. © 2023, CC BY-NC-ND.

关键词： Molecular dynamics

The stochastic Feynman-Hellmann method 36

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The stochastic Feynman-Hellmann method

36th Annual International Symposium on Lattice Field Theory, LATTICE 2018

作者： Gambhir, Arjun Singh Brantley, David Vranas, Pavlos Berkowitz, Evan Chang, Chia Cheng Clark, M.A. Kurth, Thorsten Walker-Loud, André Monahan, Chris Nicholson, Amy Nuclear and Chemical Sciences Division Lawrence Livermore National Laboratory United States Institut fur Kernphysik Institute for Advanced Simulation Forschungszentrum Julich Germany RIKEN 2-1 Hirosawa Japan NVIDIA Corporation United States National Energy Research Scientific Computing Center Nuclear Science Division Lawrence Berkeley National Laboratory United States Institute for Nuclear Theory University of Washington United States Department of Physics and Astronomy University of North Carolina United States

The Feynman-Hellmann method, as implemented by Bouchard et al. [1612.06963], was recently employed successfully to determine the nucleon axial charge. A limitation of the method was the restriction to a single operator and a single momentum during the computation of each "Feynman-Hellmann" propagator. By using stochastic techniques to estimate the all-to-all propagator, we relax this constraint and demonstrate the successful implementation of this new method. We show reproduction of the axial charge on a test ensemble and non-zero momentum transfer points of the axial and vector form factors. © Copyright owned by the author(s) under the terms of the Creative Commons.

关键词： Stochastic systems

Generalized superradiant assembly for nanophotonic thermal emitters

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Physical Review B 2018年第12期97卷 125406-125406页

作者： Sudaraka Mallawaarachchi Sarath D. Gunapala Mark I. Stockman Malin Premaratne Advanced Computing and Simulation Laboratory (AχL) Department of Electrical and Computer Systems Engineering Monash University Clayton Victoria 3800 Australia Jet Propulsion Laboratory California Institute of Technology Pasadena California 91109 USA Department of Physics and Astronomy Georgia State University Atlanta Georgia 30303 USA

Superradiance explains the collective enhancement of emission, observed when nanophotonic emitters are arranged within subwavelength proximity and perfect symmetry. Thermal superradiant emitter assemblies with variable photon far-field coupling rates are known to be capable of outperforming their conventional, nonsuperradiant counterparts. However, due to the inability to account for assemblies comprising emitters with various materials and dimensional configurations, existing thermal superradiant models are inadequate and incongruent. In this paper, a generalized thermal superradiant assembly for nanophotonic emitters is developed from first principles. Spectral analysis shows that not only does the proposed model outperform existing models in power delivery, but also portrays unforeseen and startling characteristics during emission. These electromagnetically induced transparency like (EIT-like) and superscattering-like characteristics are reported here for a superradiant assembly, and the effects escalate as the emitters become increasingly disparate. The fact that the EIT-like characteristics are in close agreement with a recent experimental observation involving the superradiant decay of qubits strongly bolsters the validity of the proposed model.

关键词： Nanophotonics Superradiance & subradiance