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利用非线性高斯-赫尔默特模型与抗差估计的点云拟合方法

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武汉大学学报（信息科学版） 2024年第7期49卷 1201-1211页

作者：赵志胜陈宇王彬南京工业大学测绘科学与技术学院江苏南京211816

目前已有的点云拟合方法大多是在线性的高斯-马尔可夫(Gauss-Markov,GM)或变量误差(errors-in-variables,EIV)模型基础上提出的,无法严格适用于非线性的曲面拟合问题。将点云拟合的数学模型统一抽象为更具一般性的非线性高斯-赫尔默特(G... 详细信息

目前已有的点云拟合方法大多是在线性的高斯-马尔可夫(Gauss-Markov,GM)或变量误差(errors-in-variables,EIV)模型基础上提出的,无法严格适用于非线性的曲面拟合问题。将点云拟合的数学模型统一抽象为更具一般性的非线性高斯-赫尔默特(Gauss-Helmert,GH)模型,并针对数据存在粗差的情况,引入等价权抗差方案,提出了一种基于抗差非线性GH(robust nonlinear GH,RGH)模型的点云拟合方法。该方法首先从原始观测值的误差出发,将导出的点坐标的协方差阵作为先验随机模型,然后利用标准化残差和中位数构造权函数,进行抗差迭代计算。结果表明,当数据包含粗差时,RGH模型获得的球面仿真数据的参数均方根误差分别仅为随机抽样一致性(random sample consensus,RANSAC)算法的25.77%~30.67%,实测数据的参数标准差分别仅为RANSAC方法的4.63%~5.49%,验证了所提方法在点云拟合的精度和稳健性方面具有显著优势。

关键词：点云拟合粗差非线性GH模型抗差估计标准化残差

Surface-sensitive electronic structure of kagome superconductor CsV_(3)Sb_(5)

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Chinese Physics B 2024年第10期33卷 35-40页

作者： zhisheng zhao Jianghao Yao Rui Xu Yuzhe Wang Sen Liao Zhengtai Liu Dawei Shen Shengtao Cui Zhe Sun Yilin Wang Donglai Feng Juan Jiang School of Emerging Technology and Department of Physics University of Science and Technology of ChinaHefei 230026China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201210China National Synchrotron Radiation Laboratory School of Nuclear Science and Technology and New Cornerstone Science LaboratoryUniversity of Science and Technology of ChinaHefei 230026China

We systematically study the electronic structure of a kagome superconductor CsV_(3)Sb_(5)at different temperatures coveringboth its charge density wave state and normal state with angle-resolved photoemission *** observe thatthe V-shaped band aroundГshows three different behaviors,referred to as a/a',βandγ,mainly at different *** investigations confirm that these bands are all from the same bulk Sb-p_(z)origin,but they are quite sensitiveto the sample surface conditions mainly modulated by ***,the intriguing temperature dependent electronicbehavior of the band nearГis affected by the sample surface condition,rather than intrinsic electronic behavior originatingfrom the phase *** result systematically reveals the confusing electronic structure behavior of the energy bandsaroundГ,facilitating further exploration of the novel properties in this material.

关键词： kagome ARPES charge density wave surface sensitive

Ultrafine-grained high-entropy zirconates with superior mechanical and thermal properties

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Journal of Materiomics 2023年第2期9卷 370-377页

作者： Mengdong Ma Yangjie Han zhisheng zhao Jing Feng Yanhui Chu School of Materials Science and Engineering South China University of TechnologyGuangzhou510641China Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao066004China School of Materials Science and Engineering Kunming University of Science and TechnologyKunming650093China

Ultrafine-grained(Sm_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2)Yb_(0.2))_(2)Zr_(2)O_(7)high-entropy zirconates with single fluorite structure have been fabricated by high-pressure sintering of the self-synthesized nanopowders for the first *** as-sintered samples exhibit a good microstructure with a grain size of 220 nm and a relative density of 96.8%,which yield excellent comprehensive mechanical properties with a high Vickers hardness of 12.5 GPa and a high fracture toughness of 3.4 MPa·m1/*** addition,the as-sintered samples possess a good thermostability with the grain growth rate of 30 nm/h,and a low thermal conductivity of 1.57 W·m^(-1)·℃^(-1)at room *** superior mechanical and thermal properties are primarily attributed to the“high-entropy”and grain-refinement effects and good interface bonding.

关键词： High-entropy ceramics Zirconates Mechanical properties Thermal conductivity

Design of a Class of New sp^(2)-sp^(3)Carbons Constructed by Graphite and Diamond Building Blocks

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Chinese Physics Letters 2021年第2期38卷 112-117页

作者： Kun Luo Bing Liu Lei Sun zhisheng zhao Yongjun Tian Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China

The sp^(2)–sp^(3)-hybridized carbon allotropes with the advantage of two hybrid structures possess rich and fascinating electronic and mechanical properties and they have received long-standing *** design a class of versatile sp^(2)–sp^(3)carbons composed of graphite and diamond structural units with variable *** class of sp^(2)–sp^(3)carbons is energetically more favorable than graphite under high pressure,and their mechanical and dynamical stabilities are further confirmed at ambient *** calculations of band structure and mechanical properties indicate that this class of sp^(2)–sp^(3)carbons not only exhibits peculiar electronic characteristics adjusted from semiconducting to metallic nature but also presents excellent mechanical characteristics,such as superhigh hardness and high *** sp^(2)–sp^(3)carbons have desirable properties across a broad range of potential applications.

关键词： ductility Diamond versatile

Discovery of superhard materials via CALYPSO methodology

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Chinese Physics B 2019年第10期28卷 10-21页

作者： Shuangshuang Zhang Julong He zhisheng zhao Dongli Yu Yongjun Tian Center for High Pressure Science (CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan University

The study of superhard materials plays a critical role in modern industrial applications due to their widespread applications as cutting tools, abrasives, exploitation drills, and coatings. The search for new superhard materials with superior performance remains a hot topic and is mainly considered as two classes of materials:(i) the light-element compounds in the B-C-N-O(-Si) system with strong and short covalent bonds, and(ii) the transition-element light-element compounds with strong covalent bonds frameworks and high valence electron density. In this paper, we review the recent achievements in the prediction of superhard materials mostly using the advanced CALYPSO methodology. A number of novel, superhard crystals of light-element compounds and transition-metal borides, carbides, and nitrides have been theoretically identified and some of them account well for the experimentally mysterious phases. To design superhard materials via CALYPSO methodology is independent of any known structural and experimental data, resulting in many remarkable structures accelerating the development of new superhard materials.

关键词： CALYPSO superhard materials crystal structure prediction

Continuous strengthening in nanotwinned diamond

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npj Computational Materials 2019年第1期5卷 111-116页

作者： Bin Wen Bo Xu Yanbin Wang Guoying Gao Xiang-Feng Zhou zhisheng zhao Yongjun Tian Center for High Pressure Science State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 66004China Center for Advanced Radiation Sources University of ChicagoChicagoIL 60439USA

Strengths of nanograined(ng)and nanotwinned(nt)metals increase with decreasing grain size and twin thickness,respectively,until reaching a critical value,below which strength *** behavior is known as the reverse Hall–Petch effect(RHPE),which has also been observed in nanograined cubic boron nitride(cBN)and ***,however,hardness of nt-cBN and nt-diamond increases continuously with decreasing twin thickness down to several nanometers,suggesting the absence of RHPE in these covalent *** mechanism responsible for such a behavior remains *** we investigate the strengthening mechanisms in ng-and nt-diamond using molecular dynamics and first-principles *** ng-diamond,the competition between shuffle-set dislocation(SSD)and grain boundary atom motions gives rise to *** nt-diamond,SSDs remain dominant but their slips along twin boundaries energetically show no advantage over those along other slip *** domains are locked and mechanically stable,resisting SSD propagation and inhibiting *** findings provide new insights into the hardening mechanism of nanotwinned covalent materials.

关键词： strengthening grain mechanism

Properties of CaB_6 single crystals synthesized under high pressure and temperature

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Science China(Physics,Mechanics & Astronomy) 2011年第10期54卷 1791-1795页

作者： XIN ShengWei LIU ShaoCun zhao zhisheng YANG JianQing XU Bo TIAN YongJun YU DongLi State Key Laboratory of Metastable Materials Science and Technology Yanshan University Qinhuangdao 066004 China

Pure CaB6single crystals are synthesized under high pressure (1 GPa) and temperature (1050°C). The temperature-dependenceof electric resistivity and Hall coefficient from 2 to 300 K shows that the CaB6single crystals are conductors withsemi-metallic behavior and electron carriers. Band structure calculations indicate that the conduction and valence bands meetat the X point at the Fermi level, which is consistent with the experimentally determined conducting behavior of CaB6singlecrystals. Calculations of state density suggest that the states at the Fermi level originate from the 2p orbital of the B atoms andthe 3d orbital of the Ca atom. Magnetization measurements show the paramagnetic nature of the CaB6. The micro-hardness ofCaB6is 24.39 GPa, and the Raman spectra of CaB6yield three sharp peaks at around 780.9, 1138.9, and 1282.1 cm 1for T2g,Eg, and A1g, respectively. The specific heat of the crystal is measured and found to be well described by the Debye and Einsteincombined model. The fitting results show Debye and Einstein temperatures are 1119 and 199 K, respectively.

关键词： high pressure CaB6 semi-metallic single crystals

Nanocrystalline high-entropy hexaboride ceramics enable remarkable performance as thermionic emission cathodes

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Fundamental Research 2023年第6期3卷 979-987页

作者： Mengdong Ma Xinyu Yang Hong Meng zhisheng zhao Julong He Yanhui Chu School of Materials Science and Engineering South China University of TechnologyGuangzhou 510641China Center for High Pressure Science(CHiPS) State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China

The development of high-entropy borides with combined structural and functional performance holds untold scientific and technological potential,yet relevant studies have been rarely *** this work,we report nanocrystalline(La_(0.25)Ce_(0.25)Nd_(0.25)Eu_(0.25))B6 high-entropy rare-earth hexaboride(HEReB6-1)ceramics fabricated through the high-pressure sintering of self-synthesized nanopowders for the first *** as-fabricated samples exhibited a highly dense(96.3%)nanocrystalline(94 nm)microstructure with major(001)fiber textures and good grain boundaries without any impurities,resulting in a remarkable mechanical,electrical,and thermionic emission *** results showed that the samples possessed outstanding comprehensive mechanical properties and a high electrical resistivity from room temperature to high temperatures;these were greater than the average values of corresponding binary rare-earth hexaborides,such as a Vickers hardness of 23.4±0.6 GPa and a fracture toughness of 3.0±0.4 MPa•m^(1/2)at room *** importantly,they showed high emission current densities at elevated temperatures,which were higher than the average values of the corresponding binary rare-earth *** instance,the maximum emission current density reached 48.3 A•cm^(−2)at 1873 *** superior performance makes the nanocrystalline HEReB6-1 ceramics highly suitable for potential applications in thermionic emission cathodes.

关键词： High-entropy ceramics Hexaborides Nanocrystalline Mechanical properties Thermionic emission

Broadband photodetector of high quality Sb2S3 nanowire grown by chemical vapor deposition

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Journal of Materials Science & Technology 2021年第16期75卷 14-20页

作者： Kun Ye Bochong Wang Anmin Nie Kun Zhai Fusheng Wen Congpu Mu zhisheng zhao Jianyong Xiang Yongjun Tian Zhongyuan Liu Center for High Pressure Science State Key Laboratory of Metastable Materials Science & Technology Yanshan University Key Laboratory for Microstructural Material Physics of Hebei Province School of Science Yanshan University

Low dimensional semiconductors can be used for various electronic and optoelectronic devices because of their unique structure and property. In this work, one-dimensional SbSnanowires(NWs) with high crystallinity were grown via chemical vapor deposition(CVD) technique on SiO/Si substrates. The SbSNWs exhibited needle-like structures with inclined cross-sections. The lengths of SbSnanowires changed from 7 to 13 μm. The photodetection properties of SbSnanowires were comprehensively and systematically characterized. The SbSphotodetectors show a broadband photoresponse ranging from ultraviolet(360 nm) to near-infrared(785 nm). An excellent specific detectivity of 2.1 × 101~4 Jones, high external quantum efficiency of 1.5 × 10~4%, sensitivity of 2.2 × 104 cm~2 Wand short response time of less than 100 ms was achieved for the SbSNW photodetectors. Moreover, the SbSNWs showed outstanding switch cycling stability that was beneficial to the practical applications. The high-quality SbSnanowires fabricated by CVD have great application potential in semiconductor and optoelectronic fields.

关键词： Sb 2 S 3 nanowires Photodetector Chemical Vapor Deposition