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A FAS approach for stabilization of generalized chained forms: part 1. Discontinuous control laws

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science China(Information sciences) 2024年第2期67卷 118-143页

作者： Guang-Ren DUAN center for Control Theory and Guidance Technology Harbin Institute of Technology center for Control science and Technology Southern University of Science and Technology

In this paper, a type of general nonholonomic systems is proposed, which contains both the Brockett’s two example systems, and their extended n-dimensional chained forms, as special cases. For the stabilization of such systems, a stabilizing controller is proposed based on the fully actuated system(FAS)approach, which is discontinuous at the origin but time-invariant when the open-loop system is time-invariant,and drives the feasible trajectories of the system to the origin exponentially. Furthermore, the proposed FAS approach is also extended to the sub-normal system case and the time-delay system case.

关键词： nonholonomic systems feedback stabilization exponential convergence sub-fully actuated systems time-delay systems

Bilayer borophene:an efficient catalyst for hydrogen evolution reaction

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Frontiers of Chemical science and Engineering 2024年第3期18卷 13-23页

作者： Na Xing Nan Gao Panbin Ye Xiaowei Yang Haifeng Wang Jijun Zhao College of sciences/Xinjiang Production&Construction Corps Key Laboratory of Advanced Energy Storage Materials and Technologies Shihezi UniversityShihezi832000China Key Laboratory of Materials Modification by laser Ion and Electron Beams(Ministry of Education)Dalian University of TechnologyDalian116024China School of Materials science and Engineering Taizhou UniversityTaizhou318000China

The electrocatalytic hydrogen evolution reaction is a crucial technique for green hydrogen ***,finding affordable,stable,and efficient catalyst materials to replace noble metal catalysts remains a significant *** experimental breakthroughs in the synthesis of two-dimensional bilayer borophene provide a theoretical framework for exploring their physical and chemical *** this study,we systematically considered nine types of bilayer borophenes as potential electrocatalysts for the hydrogen evolution *** first-principles calculations revealed that bilayer borophenes exhibit high stability and excellent conductivity,possessing a relatively large specific surface area with abundant active *** surface boron atoms and the bridge sites between two boron atoms can serve as active sites,displaying high activity for the hydrogen evolution ***,the Gibbs free energy change associated with adsorption for these bilayer borophenes can reach as low as−0.002 eV,and the Tafel reaction energy barriers are lower(0.70 eV)than those on ***,the hydrogen evolution reaction activity of these two-dimensional bilayer borophenes can be described by engineering their work ***,we considered the effect of pH on hydrogen evolution reaction activity,with significant activity observed in an acidic *** theoretical results reveal the excellent catalytic performance of two-dimensional bilayer borophenes and provide crucial guidance for the experimental exploration of multilayer boron for various energy applications.

关键词： bilayer borophene hydrogen evolution reaction work function pH effect

Microstructure and property of laser additive manufactured alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si after aged at different temperatures

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Rare Metals 2024年第5期43卷 2275-2281页

作者： Guo-Chao Li Xu Cheng Hua-Ming Wang National Engineering Laboratory of Additive Manufacturing for Large Metallic Components and Engineering Research center of Ministry of Education on laser Direct Manufacturing for Large Metallic Components School of Materials Science and EngineeringBeihang UniversityBeijing 100191China

The solid solution and aging treatment for conventional manufacturing processes might not be suitable for laser additive manufactured titanium alloys due to the different lamellar *** this study,the influence of aging temperatures(600,700 and 800°C)on microstructure and mechanical properties of titanium alloy Ti-6Al-2V-1.5Mo-0.5Zr-0.3Si was *** results indicate that after solid solution treatment at 970°C followed by water quenching,the alloy mainly consists of coarsening lamellar a phase in martensite α' *** at 600°C will not change the size of primary lamellar α phase but lead to huge amount of secondary a phases(α_(s))generating with very fine *** increasing the aging temperature,the number of α_(s) decreases but with coarsened *** aged at 800°C,the width of the asphase reaches 350 nm,almost 7 times wider than that aged at 600°*** changing size of α_(s) obviously influences the property of the *** fine α_(s) leads to high strength and microhardness but low plasticity,and specimen aged at 700°C with suitable assize has the best comprehensive properties.

关键词： α+βtitanium alloy laser additive manufacturing Solid solution and aging treatment Microstructure Room temperature tensile property

Diagnosis of indirectly driven double shell targets with point-projection hard x-ray radiography

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Matter and Radiation at Extremes 2024年第2期9卷 50-62页

作者： Chao Tian Minghai Yu Lianqiang Shan Fengjuan Wu Bi Bi Qiangqiang Zhang Yuchi Wu Tiankui Zhang Feng Zhang Dongxiao Liu Weiwu Wang Zongqiang Yuan Siqian Yang Lei Yang Zhigang Deng Jian Teng Weimin Zhou Zongqing Zhao Yuqiu Gu Baohan Zhang science and Technology on Plasma Physics Laboratory Laser Fusion Research CenterChina Academy of Engineering PhysicsMianyang 621900People’s Republic of China Joint Laboratory for Extreme Conditions Matter Properties Southwest University of Science and TechnologyMianyang 621010People’s Republic of China IFSA Collaborative Innovation center Shanghai Jiao Tong UniversityShanghai 200240People’s Republic of China

We present an application of short-pulse laser-generated hard x rays for the diagnosis of indirectly driven double shell targets. Coneinserted double shell targets were imploded through an indirect drive approach on the upgraded SG-II laser facility. Then, based on thepoint-projection hard x-ray radiography technique, time-resolved radiography of the double shell targets, including that of their near-peakcompression, were obtained. The backlighter source was created by the interactions of a high-intensity short pulsed laser with a metalmicrowire target. Images of the target near peak compression were obtained with an Au microwire. In addition, radiation hydrodynamicsimulations were performed, and the target evolution obtained agrees well with the experimental results. Using the radiographic images, arealdensities of the targets were evaluated.

关键词： double projection point

Effect of a negative DC bias on a capacitively coupled Ar plasma operated at different radiofrequency voltages and gas pressures

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Plasma science and Technology 2024年第5期26卷 62-71页

作者：相垚君王晓坤刘永新王友年 Key Laboratory of Materials Modification by laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024People’s Republic of China Chair of Applied Electrodynamics and Plasma Technology Ruhr University BochumBochum 44801Germany

The effect of a negative DC bias,|V_(dc)|,on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas *** electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission *** electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current *** was found that at a low|V_(dc)|,***α-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plasma impedance becomes more capacitive due to a widened ***,RF power deposition is ***|V_(dc)|exceeds a certain value,the plasma changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF ***,the plasma impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages,andα–γmode transition occurs at a lower|V_(dc)|at a higher RF *** increasing the pressure,plasma impedance becomes more resistive,so RF power deposition and electron density are *** particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

关键词： RF capacitively coupled plasma DC-overlapped RF discharge power deposition discharge mode transition

In-Situ Atomic-Scale Observation of Brownmillerite to Ruddlesden-Popper Phase Transition Tuned by Epitaxial Strain in Cobaltites

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Chinese Physics Letters 2024年第4期41卷 152-158页

作者：林挺高昂汤哲歆林炜光孙慕华张庆华王雪锋郭尔佳谷林 Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical sciences University of Chinese Academy of ScienceBeijing 100049China Beijing National center for electron Microscopy and Laboratory of Advanced Materials Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China Department of Physics&center of Materials science and Optoelectronics Engineering University of Chinese Academy of SciencesBeijing 100049China

Phase transitions involving oxygen ion extraction within the framework of the crystallographic relevance have been widely exploited for sake of superconductivity,ferromagnetism,and ion conductivity in perovskiterelated ***,atomic-scale pathways of phase transitions and ion extraction threshold are inadequately *** we investigate the atomic structure evolution of LaCoO_(3) films upon oxygen extraction and subsequent Co migration,focusing on the key role of epitaxial *** brownmillerite to Ruddlesden-Popper phase transitions are discovered to stabilize at distinct crystal orientations in compressive-and tensile-strained cobaltites,which could be attributed to in-plane and out-of-plane Ruddlesden-Popper stacking faults,respectively.A two-stage process from exterior to interior phase transition is evidenced in compressive-strained LaCoO_(2.5),while a single-step nucleation process leaving bottom layer unchanged in tensile-strained *** analyses reveal that the former process is initiated by an expansion in Co layer at boundary,whereas the latter one is associated with an edge dislocation combined with antiphase *** findings provide a chemomechanical perspective on the structure regulation of perovskite oxides and enrich insights into strain-dependent phase diagram in epitaxial oxides films.

关键词： strained Phase oxides

Ionizing terahertz waves with 260 MV/cm from scalable optical rectification

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Light(science & Applications) 2024年第6期13卷 1075-1087页

作者： Hyeongmun Kim Chul Kang Dogeun Jang Yulan Roh Sang Hwa Lee Joong Wook Lee Jae Hee Sung Seong Ku Lee Ki-Yong Kim Advanced Photonics Research Institute GISTGwangju61005Korea Department of Physics and Optoelectronics Convergence Research center Chonnam National UniversityGwangju61186Korea Pohang Accelerator Laboratory POSTECHPohang37673Korea center for Relativistic laser science Institute for Basic ScienceGwangju61005Korea Institute for Research in electronics and Applied Physics Department of PhysicsUniversity of MarylandCollege ParkMaryland20742USA

Terahertz(THz)waves,known as non-ionizing radiation owing to their low photon energies,can actually ionize atoms and molecules when a sufficiently large number of THz photons are concentrated in time and ***,we demonstrate the generation of ionizing,multicycle,15-THz waves emitted from large-area lithium niobate crystals via phase-matched optical rectification of 150-terawatt laser pulses.A complete characterization of the generated THz waves in energy,pulse duration,and focal spot size shows that the field strength can reach up to 260 megavolts per *** particular,a single-shot THz interferometer is employed to measure the THz pulse duration and spectrum with complementary numerical *** intense THz pulses are irradiated onto various solid targets to demonstrate THz-induced tunneling ionization and plasma *** study also discusses the potential of nonperturbative THz-driven ionization in gases,which will open up new opportunities,including nonlinear and relativistic THz physics in plasma.

关键词： optical interferometer matched

Characteristics and suppression of beam distortion in a high repetition rate nanosecond stimulated Brillouin scattering phase conjugation mirror

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High Power laser science and Engineering 2024年第2期12卷 69-78页

作者： Yifu Chen Bowen Tan Duo Jin Bin Chen Zhenxu Bai Kun Wang Yulei Wang Zhiwei Lü School of Astronautics Harbin Institute of TechnologyHarbinChina center for Advanced laser Technology Hebei University of TechnologyTianjinChina Hebei Key Laboratory of Advanced laser Technology and Equipment TianjinChina School of Energy and Environmental Engineering Hebei University of TechnologyTianjinChina

The stimulated Brillouin scattering phase conjugation mirror (SBS-PCM) based on liquid media is widely used in high-power laser systems due to its robust thermal load capacity, high energy conversion efficiency and improved beam quality. Nevertheless, with an increase in the pump repetition rate, thermally-induced blooming and optical breakdown can emerge, leading to distortions in the Stokes beam. In this study, we delved into the thermal effects in liquid SBS-PCMs employing hydrodynamic analysis, establishing a relationship between beam profile distortion and the thermal convection field. We calculated the temperature and convection velocity distribution based on the pump light parameters and recorded the corresponding beam profiles. The intensities of the beam profiles were modulated in alignment with the convection directions, reaching a velocity peak of 2.85 mm/s at a pump pulse repetition rate of 250 Hz. The residual sum of squares (RSS) was employed to quantify the extent of beam profile distortion relative to a Gaussian distribution. The RSS escalated to 7.8, in contrast to 0.7 of the pump light at a pump pulse repetition rate of 500 Hz. By suppressing thermal convection using a high-viscosity medium, we effectively mitigated beam distortion. The RSS was reduced to 0.7 at a pump pulse repetition rate of 500 Hz, coinciding with a twentyfold increase in viscosity, thereby enhancing the beam quality. By integrating hydrodynamic analysis, we elucidated and mitigated distortion with targeted solutions. Our research offers an interdisciplinary perspective on studying thermal effects and contributes to the application of SBS-PCMs in high-repetition-rate laser systems by unveiling the mechanism of photothermal effects.

关键词： beam profile high power high repetition rate stimulated Brillouin scattering phase conjugation mirror thermal convection

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Revisit of the anisotropic vortex states of 2H-NbSe_(2) towards the zero-field limit

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Chinese Physics B 2024年第6期33卷 80-86页

作者：张凡侯兴元姜宇轩张宗源涂玉兵朱相德陈根富单磊 Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical sciences University of Chinese Academy of SciencesBeijing 100190China center of free electron laser and High Magnetic Field Anhui UniversityHefei 230601China Information Materials and Intelligent Sensing Laboratory of Anhui Province Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Key Laboratory of Structure and Functional Regulation of Hybrid Materials in Anhui University Ministry of EducationHefei 230601China School of Physics and Materials science Anhui UniversityHefei 230601China Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions High Magnetic Field LaboratoryHFIPSAnhuiChinese Academy of Sciencesand University of Science and Technology of ChinaHefei 230031China Hefei National Laboratory Hefei 230088China

We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling *** structures of the anisotropic vortex states were distinguished, one is a spatially non-splitting zero bias peak, and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest *** of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields, implying an important role played by the vortex–vortex interactions. To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K. It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy, and the spatially evolved crossing features are related to the vortex–vortex interaction. The vortex core size under the zero-field limit is determined. These results provide a paradigm for studying the inherent vortex states of type-II superconductors especially based on an isolated vortex.

关键词： vortex states zero-bias conductance peak scanning tunneling microscopy