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Stochastic Gradient Descent and Anomaly of Variance-Flatness Relation in Artificial Neural Networks

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Chinese Physics Letters 2023年第8期40卷 6-10页

作者：熊霞陈永聪石春晓敖平 Shanghai Center for Quantitative Life Sciences and Physics Department Shanghai UniversityShanghai 200444China Colloge of Biomedical Engineering Sichuan UniversityChengdu 610065China

Stochastic gradient descent(SGD),a widely used algorithm in deep-learning neural networks,has attracted continuing research interests for the theoretical principles behind its success.A recent work reported an anomaly(inverse)relation between the variance of neural weights and the landscape flatness of the loss function driven under SGD[Feng Y and Tu Y *** 118 e2015617118(2021)].To investigate this seeming violation of statistical physics principle,the properties of SGD near fixed points are analyzed with a dynamic decomposition *** approach recovers the true“energy”function under which the universal Boltzmann distribution *** differs from the cost function in general and resolves the paradox raised by the the *** study bridges the gap between the classical statistical mechanics and the emerging discipline of artificial intelligence,with potential for better algorithms to the latter.

关键词： neural bridges holds

In search of infall motion in molecular clumpsⅡ:HCO+(1-0)and HCN(1-0)observations toward a sub-sample of infall candidates

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Research in Astronomy and Astrophysics 2020年第8期20卷 129-142页

作者： Yang Yang Zhi-Bo Jiang Zhi-Wei Chen Shao-Bo Zhang Shu-Ling Yu Yi-ping ao Purple Mountain Observatory Chinese Academy of SciencesNanjing 210008China University of Science and Technology of China Chinese Academy of SciencesHefei 230026China Center astronomy and Space Sciences China Three Gorges UniversityYichang 443002China

Gravitational accretion accumulates the original *** process is crucial for us to understand the initial phases of star *** the specific infall profiles in optically thick and thin lines,we searched the clumps with infall motion from the Milky Way Imaging Scroll Painting(MWISP)CO data in previous *** this study,we selected 133 sources as a sub-sample for further research and *** excitation temperatures of these sources are between 7.0 and 38.5 K,while the H2 column densities are between 10^21 and 10^23 cm^-*** have observed optically thick lines HCO+(1-0)and HCN(1-0)using the DLH 13.7-m telescope,and found 56 sources with a blue profile and no red profile in these two lines,which are likely to have infall motions,with a detection rate of 42%.This suggests that using CO data to restrict the sample can effectively improve the infall detection *** these confirmed infall sources are 43 associated with Class O/I young stellar objects(YSOs),and 13 which are *** 13 sources are probably associated with the sources in the earlier evolutionary *** comparison,the confirmed sources that are associated with Class O/I YSOs have higher excitation temperatures and column densities,while the other sources are colder and have lower column *** infall velocities of the sources that we confirmed are between 10^-1 to 10^0 km s^-1,which is consistent with previous studies.

关键词： stars:formation ISM:kinematics and dynamics ISM:molecules radio lines:ISM

Gas-kinetic unified algorithm for computable modeling of Boltzmann equation and application to aerothermodynamics for falling disintegration of uncontrolled Tiangong-No.1 spacecraft

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Advances in Aerodynamics 2019年第1期1卷 75-95页

作者： Zhi-Hui Li ao-ping Peng Qiang Ma Lei-Ning Dang Xiao-Wei Tang Xue-Zhou Sun Hypervelocity Aerodynamics Institute China Aerodynamics Research and Development CenterP.O.Box 211Mianyang 621000China National Laboratory for Computational Fluid Dynamics BUAANo.37 Xueyuan RoadBeijing 100191China College of Mathematics Sichuan UniversityChengdu 610043China

How to solve the hypersonic aerothermodynamics around large-scale uncontrolled spacecraft during falling disintegrated process from outer space to earth,is the key to resolve the problems of the uncontrolled Tiangong-No.1 spacecraft reentry *** study aerodynamics of spacecraft reentry covering various flow regimes,a Gas-Kinetic Unified Algorithm(GKUA)has been presented by computable modeling of the collision integral of the Boltzmann equation over tens of *** this basis,the rotational and vibrational energy modes are considered as the independent variables of the gas molecular velocity distribution function,a kind of Boltzmann model equation involving in internal energy excitation is presented by decomposing the collision term of the Boltzmann equation into elastic and inelastic collision ***,the gas-kinetic numerical scheme is constructed to capture the time evolution of the discretized velocity distribution functions by developing the discrete velocity ordinate method and numerical quadrature *** unified algorithm of the Boltzmann model equation involving thermodynamics non-equilibrium effect is presented for the whole range of flow *** gas-kinetic massive parallel computing strategy is developed to solve the hypersonic aerothermodynamics with the processor cores 500~45,000 at least 80%parallel *** validate the accuracy of the GKUA,the hypersonic flows are simulated including the reentry Tiangong-1 spacecraft shape with the wide range of Knudsen numbers of 220~0.00005 by the comparison of the related results from the DSMC and N-S coupled methods,and the low-density tunnel experiment *** uncontrolling spacecraft falling problem,the finite-element algorithm for dynamic thermalforce coupling response is presented,and the unified simulation of the thermal structural response and the hypersonic flow field is tested on the Tiangong-1 shape under reentry aerodynamic ***,the forecasting analysis platform of e

关键词： Aerodynamics covering all flow regimes Boltzmann model equation in thermodynamic non-equilibrium effect Gas-Kinetic Unified Algorithm Simulation of structural failure/disintegration Numerical forecast of flying path

Band alignment between NiO_(x) and nonpolar/semipolar GaN planes for selective-area-doped termination structure

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Chinese Physics B 2021年第6期30卷 583-587页

作者： Ji-Yao Du Ji-Yu Zhou Xiao-Bo Li Tao-Fei Pu Liu-An Li Xin-Zhi Liu Jin-ping ao School of Automation and Electrical Engineering Shenyang Ligong UniversityShenyang 110159China Institute of Technology and Science Tokushima UniversityTokushimaJapan School of Physics Sun Yat-Sen UniversityGuangzhou 510275China

Band alignment between NiO_(x) and nonpolar GaN plane and between NiO_(x) and semipolar GaN plane are measured by x-ray photoelectron spectroscopy. They demonstrate that the maximum value of the valence band in the unintentional-doped a-plane, m-plane, and r-plane GaN are comparable to each other, which means that all the substrates are of n-type with similar background carrier concentrations. However, the band offset at the NiO_(x)/GaN interface presents obvious crystalline plane dependency although they are coated with the same NiO_(x) films. By fitting the Ga 3 d spectrum obtained from the NiO_(x)/GaN interface, we find that relatively high Ga–O content at the interface corresponds to a small band offset. On the one hand, the high Ga–O content on the GaN surface will change the growth mode of NiO_(x). On the other hand, the affinity difference between Ga and O forms a dipole which will introduce an extra energy band bending.

关键词： GaN NiO_(x) band alignment vertical diode

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干细胞处于所有癌症的中心吗？

科学通报 2018年第12期63卷 1076-1081页

作者：朱晓梅敖平上海大学定量生命科学国际研究中心物理系上海200444 上海交通大学系统生物医学研究院上海200240

干细胞和癌细胞是细胞众多状态中的一部分,这个事实说明干细胞不会处于所有癌症的中心,但会是癌症发生发展的一个重要因素.近年来更多的生物实验研究和医学临床观察也充分支持这个结论.干细胞与癌症的关系是关于细胞形态维持与转化——... 详细信息

干细胞和癌细胞是细胞众多状态中的一部分,这个事实说明干细胞不会处于所有癌症的中心,但会是癌症发生发展的一个重要因素.近年来更多的生物实验研究和医学临床观察也充分支持这个结论.干细胞与癌症的关系是关于细胞形态维持与转化——生物的中心问题之一.通过分析干细胞和癌症在3种层次-现象、分子生物标志、系统生物机理-中的关系,21世纪内发展起来的内源性网络理论可以作为一个全新的、综合性的思考平台.它能定量地刻画细胞状态的稳定性和相互转化的动态路径,把遗传和表观遗传现象的描述统一在同一个理论中,能更好地理解目前对这个问题研究的热潮下的生物学意义并能在理论和计算上帮助它向前推进.所有这些进展都指向一个可能:革命性的突破就在我们眼前.

关键词：干细胞癌症遗传和表观遗传内源性网络理论适应性功能景观景观拓扑图

Design of vertical diamond Schottky barrier diode with junction terminal extension structure by using the n-Ga_(2)O_(3)/p-diamond heterojunction

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Chinese Physics B 2022年第10期31卷 120-125页

作者： Wang Lin Ting-Ting Wang Qi-Liang Wang Xian-Yi Lv Gen-Zhuang Li Liu-An Li Jin-ping ao Guang-Tian Zou State Key Laboratory of Superhard Material College of PhysicsJilin UniversityChangchun 130012China Shenzhen Research Institute Jilin UniversityShenzhen 518057China National Key Discipline Laboratory of Wide Bandgap Semiconductor Xidian UniversityXi’an 710071China

A novel junction terminal extension structure is proposed for vertical diamond Schottky barrier diodes(SBDs) by using an n-Ga_(2)O_(3)/p-diamond heterojunction. The depletion region of the heterojunction suppresses part of the forward current conduction path, which slightly increases the on-resistance. On the other hand, the reverse breakdown voltage is enhanced obviously because of attenuated electric field crowding. By optimizing the doping concentration, length, and depth of n-Ga_(2)O_(3), the trade-off between on-resistance and breakdown voltage with a high Baliga figure of merit(FOM)value is realized through Silvaco technology computer-aided design simulation. In addition, the effect of the work functions of the Schottky electrodes is evaluated. The results are beneficial to realizing a high-performance vertical diamond SBD.

关键词： diamond Schottky barrier diode junction terminal extension simulation

Normally-off AlGaN/GaN heterojunction field-effect transistors with in-situ AlN gate insulator

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Chinese Physics B 2022年第12期31卷 526-530页

作者： Taofei Pu Shuqiang Liu Xiaobo Li Ting-Ting Wang Jiyao Du Liuan Li Liang He Xinke Liu Jin-ping ao Hanshan Normal University Chaozhou 521041China No.5 Electronics Research Institute of the Ministry of Industry and Information Technology Guangzhou 510610China Shenzhen University Shenzhen 518000China School of Microelectronics Xidian UniversityXi’an 710071China School of Automation and Electrical Engineering Shenyang Ligong UniversityShenyang 110159China Yibin Research Institute Jilin UniversityYibin 644000China

AlGaN/GaN heterojunction field-effect transistors(HFETs)with p-GaN cap layer are developed for normally-off operation,in which an in-situ grown AlN layer is utilized as the gate *** with the SiNxgate insulator,the AlN/p-GaN interface presents a more obvious energy band bending and a wider depletion region,which helps to positively shift the threshold *** addition,the relatively large conduction band offset of AlN/p-GaN is beneficial to suppress the gate leakage current and enhance the gate breakdown *** to the introduction of AlN layer,normally-off p-GaN capped AlGaN/GaN HFET with a threshold voltage of 4 V and a gate swing of 13 V is ***,the field-effect mobility is approximately 1500 cm^(2)·V^(-1)·s^(-1)in the 2DEG channel,implying a good device performance.

关键词： AlGaN/GaN HFET normally-off in-situ AlN metal-insulator-semiconductor

Influence of SiC Contents in Al_2O_3-SiO_2 Castables on Resistance to PbO-rich Slag

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China's Refractories 2009年第3期18卷 6-10页

作者： YU Renhong ao ping ZHOU Ningsheng WEI Ruili Henan University of Science ＆ Technology Luoyang 471003 China

Low cement Al2O3 - SiO2 castables was prepared using super grade bauxite （ w（ Al2O3 ）〉85% ） as aggregate, brown fused corundum, silicon carbide, Secar 71 CA cement, α-Al2O3 micropowder and microsilica as fine powders. The influence of SiC （0, 5 wt%, 10 wt%, and 15 wt% ）on resistance to PbO- rich slag was investigated by static crucible slag test （1 300℃ for 5 h, in air）. The slag corrosion mechanism of the castables was analyzed by means of SEM, EDS and XRD. The results show that the resistance of Al2O3 -SiO2 castables to PbO-rich slag is improved obviously by the addition of SiC. The corrosion mechanism of the PbO-rich slag can be discribed as that PbO in the slag reacts with SiO2 and Cao in Al2O3 - SiO2 castables, forming low-melting compounds （such as PbO · SiO2 and 2PbO · SiO2 ）.

关键词： Silicon carbide, Alumina silicacastables Slag resistance, Corrosion mechanism

Statistical analysis can fail to reveal underlying true biological mechanism:a demonstration of expression profile generation

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Statistical analysis can fail to reveal underlying true biol...