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The investigation of OH radicals produced in a DC glow discharge by laser-induced fluorescence spectrometry

Plasma science and technology 2021年第6期23卷 12-20页

作者： Feng LIU Yue ZHUANG Haijing CHU Zhi FANG Wenchun WANG College of Electrical Engineering and Control Science Nanjing Tech UniversityNanjing 211816People's Republic of China Key Lab of Materials Modification Dalian University of TechnologyMinistry of EducationDalian 116024People's Republic of China School of Physics and Optoelectronic Technology Dalian University of TechnologyDalian 116024People's Republic of China

In this paper the OH radicals produced by a needle-plate negative DC discharge in water vapor,N_(2)+H_(2)O mixture gas and He+H_(2)O mixture gas are investigated by a laser-induced fluorescence(LIF)*** a ballast resistor in the circuit,the discharge current is limited and the discharges remain in *** OH rotation temperature is obtained from fluorescence rotational branch fitting,and is about 350 K in pure water *** effects of the discharge current and gas pressure on the production and quenching processes of OH radicals are *** results show that in water vapor and He+H_(2)O mixture gas the fluorescence intensity of OH stays nearly constant with increasing discharge current,and in N_(2)+H_(2)O mixture gas the fluorescence intensity of OH increases with increasing discharge *** water vapor and N_(2)+H_(2)O mixture gas the fluorescence intensity of OH decreases with increasing gas pressure in the studied pressure range,and in He+H_(2)O mixture gas the fluorescence intensity of OH shows a maximum value within the studied gas pressure *** physicochemical reactions between electrons,radicals,ground and metastable molecules are *** results in this work contribute to the optimization of plasma reactivity and the establishment of a molecule reaction dynamics model.

关键词： laser-induced fluorescence OH radicals rotational temperature water vapor

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Thermodynamic Geometry of Nonequilibrium Fluctuations in Cyclically Driven Transport

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Physical Review Letters 2024年第20期132卷 207101-207101页

作者： Zi Wang (王子) Jie Ren (任捷) Center for Phononics and Thermal Energy Science China-EU Joint Lab on Nanophononics Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and Engineering Tongji University Shanghai 200092 China.

Nonequilibrium thermal machines under cyclic driving generally outperform steady-state counterparts. However, there is still lack of coherent understanding of versatile transport and fluctuation features under time modulations. Here, we formulate a theoretical framework of thermodynamic geometry in terms of full counting statistics of nonequilibrium driven transports. We find that, besides the conventional dynamic and adiabatic geometric curvature contributions, the generating function is also divided into an additional nonadiabatic contribution, manifested as the metric term of full counting statistics. This nonadiabatic metric generalizes recent results of thermodynamic geometry in near-equilibrium entropy production to far-from-equilibrium fluctuations of general currents. Furthermore, the framework proves geometric thermodynamic uncertainty relations of near-adiabatic thermal devices, constraining fluctuations in terms of statistical metric quantities and thermodynamic length. We exemplify the theory in experimentally accessible driving-induced quantum chiral transport and Brownian heat pump.

关键词： Nonequilibrium & irreversible thermodynamics Nonequilibrium statistical mechanics Fokker–Planck equation Full counting statistics Master equation

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Sensitivity Enhancement of Platinum Diselenide Based SPR Sensor Using Titanium Dioxide as Adhesion Layer 4th

Sensitivity Enhancement of Platinum Diselenide Based SPR Sen...

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4th International Conference on VLSI, Communication and Signal processing, VCAS 2021

作者： Tiwari, Rashmi Singh, Sachin Lohia, Pooja Dwivedi, D.K. Department of Physics and Material Science Amorphous Semiconductor Research Lab Madan Mohan Malaviya University of Technology Gorakhpur273010 India Department of Electronics and Communication Engineering Madan Mohan Malaviya University of Technology Gorakhpur273010 India

ISBN: (纸本)9789811926303

This paper reports a theoretical representation of SPR biosensor consisting of a two-dimensional transition dichalcogenides material, gold as a plasmonic metal, calcium difluoride (CaF2) glass prism and an adhesive material titanium dioxide (TiO2). The performance of proposed biosensor is assessed in terms of its performance parameters;sensitivity (S), Figure of merit (FOM), Limit of detection (LOD), FWHM (full width half maximum) and DA (detection accuracy). The highest sensitivity noted in this work is 2180RIU−1 which is 4.80% greater than the sensitivity noted for SPR biosensor without adhesive material i.e., without TiO2. The sensitivity of proposed structure without titanium dioxide is 2080RIU−1. Figure of merit, FWHM, limit of detection and detection accuracy of the proposed structure is 53.322 RIU−1, 4.0870, 4.587 × 10–6 and 0.2446 deg−1 respectively. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

关键词： Titanium dioxide

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Essentially degenerate hidden nodal lines in two-dimensional magnetic layer groups

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Physical Review B 2024年第23期110卷 235163-235163页

作者： Xiao-Ping Li Chaoxi Cui Lei Wang Weikang Wu Zeying Zhang Zhi-Ming Yu Yugui Yao School of Physical Science and Technology Inner Mongolia University Hohhot 010021 China Centre for Quantum Physics Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE) School of Physics Beijing Institute of Technology Beijing 100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing 100081 China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials Ministry of Education Shandong University Jinan 250061 China College of Mathematics and Physics Beijing University of Chemical Technology Beijing 100029 China

According to the theory of group representations, the types of band degeneracy can be divided into accidental degeneracy and essential degeneracy. The essentially degenerate nodal lines (NLs) are typically resided on the high-symmetry lines of the Brillouin zone. Here, we propose a type of NL in two dimensions that is essentially degenerate but is hidden within the high-symmetry planes, making it less observable, dubbed a hidden-essential nodal line (HENL). The existence of HENL is guaranteed as long as the system hosts a horizontal glide-mirror symmetry, hence such NLs can be widely found in both nonmagnetic and magnetic systems. We perform an exhaustive search over all 528 magnetic layer groups (MLGs) for HENL that can be enforced by glide-mirror symmetry with both spinless and spinfull systems. We find that 122 candidate MLGs host spinless HENL, while 63 candidate MLGs demonstrate spinful HENL. In addition, we reveal that horizontal mirror and time-reversal symmetry in type-II and type-IV MLGs with spin-orbital coupling can enforce HENL formed. The 15 corresponding candidate MLGs have also been presented. Furthermore, we derive a few typical lattice models to characterize the existence for the HENL. For specific electronic fillings in real materials, namely 4N+2 in spinless systems (and 2N+1 in spinful systems), the presence of the HENLs in candidate MLGs is required regardless of the details of the systems. Using ab initio calculations, we further identify possible material candidates that realize spinless and spinful HENL. Moreover, spinful HENLs exhibit a persistent spin texture with the characteristic of momentum-independent spin configuration. Our findings uncover a type of topological semimetal state and offer an ideal platform to study the related physics of HENLs.

关键词： Mirrors

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Anomalous shift in Andreev reflection from side incidence

arXiv

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arXiv 2024年

作者： Li, Runze Cui, Chaoxi Liu, Ying Yu, Zhi-Ming Yang, Shengyuan A. School of Physics Beijing Institute of Technology Beijing100081 China Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems School of Physics Beijing Institute of Technology Beijing100081 China School of Materials Science and Engineering Hebei University of Technology Tianjin300130 China Research Laboratory for Quantum Materials IAPME Faculty of Science and Technology University of Macau China

Andreev reflection at a normal-superconductor interface may be accompanied with an anomalous spatial shift. The studies so far are limited to the top incidence configuration. Here, we investigate this effect in the side incidence configuration, with the interface parallel to the principal axis of superconductor. We find that the shift exhibits rich behaviors reflecting the character of pair potential. It has two contributions: one from the k-dependent phase of pair potential, and the other from the evanescent mode. For chiral p-wave pairing, the pairing phase contribution is proportional to the chirality of pairing and is independent of excitation energy, whereas the evanescent mode contribution is independent of chirality and is nonzero only for excitation energy below the gap. The two contributions also have opposite parity with respect to the incident angle. For dx2-y2-wave pairing, only the evanescent mode contribution exists, and the shift exhibits suppressed zones in incident angles, manifesting the superconducting nodes. The dependence of the shift on other factors, such as the angle of incident plane and Fermi surface anisotropy, are discussed. Copyright © 2024, The Authors. All rights reserved.

关键词： Chirality

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Effect of Spectral Resolution and Snr of Vis-Nir Spectrometer on the Estimation of Soil Organic Matter

SSRN

引用

SSRN 2023年

作者： Yu, Bo Yuan, Jing Yan, Changxiang Xu, Jiawei Ma, Chaoran Dai, Hu Changchun Institute of Optics Fine Mechanics and Physics Chinese Academy of Sciences Changchun130033 China University of Chinese Academy of Sciences Beijing100049 China Center of Materials Science and Optoelectrics Engineering University of Chinese Academy of Science Beijing100049 China National Key Laboratory of Science and Technology on Vacuum Technology and Physics Lanzhou Institute of Physics Lanzhou730000 China

In the last few decades, Visible and near-infrared (Vis-NIR) spectroscopy has emerged as a quick tool for estimating soil properties. Currently, most studies address that different pretreatments and modeling approaches affect the prediction accuracy of soil properties. However, the parameters of the spectroscopic instrument also determine the prediction performance. The focus of this study is to evaluate the impacts of the two core parameters (spectral resolution, and SNR) of spectrometers on the prediction performance of soil organic matter (SOM). To this aim, the initial soil spectral dataset (which was measured by an ASD spectrometer) was converted to construct two independent simulated soil spectral datasets that can be individually varied in terms of spectral resolution and SNR level. To verify the consistency and generality of our results, we adopted ridge regression (RR), partial least squares regression (PLSR), support vector machine regression, (SVMR), and back propagation neural network (BPNN) to develop multivariate calibration models. Finally, the ANOVA technique was performed on the RMSE and [[EQUATION]] obtained through the independent validation set to identify the factors that significantly affect the predictive performance of SOM and to determine the lowest spectral resolution and SNR level was identified without significantly affecting the prediction accuracy. Our results showed that i) the significant effects on the predictive performance of SOM in descending order of magnitude is SNR levels > spectral resolution > prediction models, ii) there is no significant difference in the predictive performance when the spectral resolution is within 100 nm and iii) when the SNR level is higher than 15%SNR, the different SNR levels do not give significant differences in the predictive performance of the SOM. In conclusion, only knowing the impact of these instrument parameters on the estimation of SOM can assist us in decision-making on the development of a

关键词： Least squares approximations

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Optical spin-symmetry breaking for high-efficiency directional helicity-multiplexed metaholograms

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Microsystems & Nanoengineering 2021年第2期7卷 71-79页

作者： Muhammad Ashar Naveed Muhammad Afnan Ansari Inki Kim Trevon Badloe Joohoon Kim Dong Kyo Oh Kashif Riaz Tauseef Tauqeer Usman Younis Murtaza Saleem Muhammad Sabieh Anwar Muhammad Zubair Muhammad Qasim Mehmood Junsuk Rho NanoTech Lab Department of Electrical EngineeringInformation Technology University(ITU)of the PunjabFerozepur RoadLahore54600Pakistan Department of Mechanical Engineering Pohang University of Science and Technology(POSTECH)Pohang37673Republic of Korea Department of Physics Lahore University of Management Sciences(LUMS)Lahore54792Pakistan Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang37673Republic of Korea National Institute of Nanomaterials and Technology(NINT) Pohang37673Republic of Korea

Helicity-multiplexed metasurfaces based on symmetric spin–orbit interactions (SOIs) have practical limits because they cannot provide central-symmetric holographic imaging. Asymmetric SOIs can effectively address such limitations, with several exciting applications in various fields ranging from asymmetric data inscription in communications to dual side displays in smart mobile devices. Low-loss dielectric materials provide an excellent platform for realizing such exotic phenomena efficiently. In this paper, we demonstrate an asymmetric SOI-dependent transmission-type metasurface in the visible domain using hydrogenated amorphous silicon (a-Si:H) nanoresonators. The proposed design approach is equipped with an additional degree of freedom in designing bi-directional helicity-multiplexed metasurfaces by breaking the conventional limit imposed by the symmetric SOI in half employment of metasurfaces for one circular handedness. Two on-axis, distinct wavefronts are produced with high transmission efficiencies, demonstrating the concept of asymmetric wavefront generation in two antiparallel directions. Additionally, the CMOS compatibility of a-Si:H makes it a cost-effective alternative to gallium nitride (GaN) and titanium dioxide (TiO2) for visible light. The cost-effective fabrication and simplicity of the proposed design technique provide an excellent candidate for high-efficiency, multifunctional, and chip-integrated demonstration of various phenomena.

关键词： directional breaking visible

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Machine learning approach for the prediction and optimization of thermal transport properties

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Frontiers of physics 2021年第4期16卷 75-90页

作者： Yulou Ouyang Cuiqian Yu Gang Yan Jie Chen Center for Phononics and Thermal Energy Science China–EU Joint Lab for NanophononicsSchool of Physics Science and EngineeringTongji UniversityShanghai 200092China Shanghai Institute of Intelligent Science and Technology Tongji UniversityShanghai 200092China

Traditional simulation methods have made prominent progress in aiding experiments for understanding thermal transport properties of materials,and in predicting thermal conductivity of novel ***,huge challenges are also encountered when exploring complex material systems,such as formidable computational *** a rising computational method,machine learning has a lot to offer in this regard,not only in speeding up the searching and optimization process,but also in providing novel *** this work,we review the state-of-the-art studies on material’s thermal properties based on machine learning ***,the basic principles of machine learning method are *** then review applications of machine learning technique in the prediction and optimization of material’s thermal properties,including thermal conductivity and interfacial thermal ***,an outlook is provided for the future studies.

关键词： machine learning thermal transport optimization prediction

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Towards an Understanding of Stepwise Inference in Transformers: A Synthetic Graph Navigation Model 41

Towards an Understanding of Stepwise Inference in Transforme...

引用

41st International Conference on Machine Learning, ICML 2024

作者： Khona, Mikail Okawa, Maya Hula, Jan Ramesh, Rahul Nishi, Kento Dick, Robert Lubana, Ekdeep Singh Tanaka, Hidenori Massachusetts Institute of Technology United States NTT Physics and Informatics Lab United States Czech Technical University in Prague The University of Ostrava Czech Republic University of Pennsylvania United States Center for Brain Science Harvard University United States University of Michigan United States

Stepwise inference protocols, such as scratchpads and chain-of-thought, help language models solve complex problems by decomposing them into a sequence of simpler subproblems. To unravel the underlying mechanisms of stepwise inference we propose to study autoregressive Transformer models on a synthetic task that embodies the multi-step nature of problems where stepwise inference is generally most useful. Specifically, we define a graph navigation problem wherein a model is tasked with traversing a path from a start to a goal node on the graph. We find we can empirically reproduce and analyze several phenomena observed at scale: (i) the stepwise inference reasoning gap, the cause of which we find in the structure of the training data;(ii) a diversity-accuracy tradeoff in model generations as sampling temperature varies;(iii) a simplicity bias in the model's output;and (iv) compositional generalization and a primacy bias with in-context exemplars. Overall, our work introduces a grounded, synthetic framework for studying stepwise inference and offers mechanistic hypotheses that can lay the foundation for a deeper understanding of this phenomenon. Copyright 2024 by the author(s)

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Revealing the electron-spin fluctuation coupling by photoemission in CaKFe4As4

arXiv

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arXiv 2025年

作者： Li, Peng Wang, Yuzhe Liu, Yabin Yao, Jianghao Zhao, Zhisheng Liu, Zhengtai Shen, Dawei Luo, Huiqian Cao, Guanghan Jiang, Juan Feng, Donglai School of Emerging Technology University of Science and Technology of China Hefei230026 China Shenzhen518045 China Hefei National Laboratory University of Science and Technology of China Hefei230088 China Department of Physics State Key Lab of Silicon Materials Zhejiang University Hangzhou310027 China Chinese Academy of Sciences Shanghai200050 China National Synchrotron Radiation Laboratory School of Nuclear Science and Technology New Cornerstone Science Laboratory University of Science and Technology of China Hefei230026 China Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing100190 China

Electron-boson coupling in unconventional superconductors is one of the key parameters in understanding the superconducting pairing symmetry. Here, we report definitive photoemission evidence of electron-spin exciton coupling in the iron-based superconductor CaKFe4As4, obtained via high-resolution ARPES. Our study identifies a distinct kink structure on the α band, observable only in the superconducting phase and closely linked with the superconductivity, indicative of strong electron-boson interactions. Notably, this kink structure corresponds to two distinct bosonic modes at 11 meV and 13 meV, aligning with spin resonance modes previously observed in inelastic neutron scattering experiments. This alignment underscores the significant role of antiferromagnetic fluctuations in the pairing mechanism of this superconductor. Furthermore, the unique momentum-dependent and orbital-selective properties of the coupling revealed by ARPES provide profound insights into the pairing symmetry, suggesting predominantly s± wave pairing facilitated by spin fluctuations. Our findings not only highlight the pivotal role of spin resonance in the superconductivity of CaKFe4As4 but also enhance understanding of the electron-spin exciton interactions in unconventional superconductors. © 2025, CC BY.

关键词： Iron-based Superconductors

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