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Lagrangian coherent structures and their heat-transport mechanism in the turbulent Rayleigh-Bénard convection

Science China(Technological Sciences) 2022年第4期65卷 966-976页

作者： CHENG Hang SHEN Jie zhang yizhao ZHOU Quan CHONG Kai Leong LIU YuLu LU ZhiMing Shanghai Institute of Applied Mathematics and Mechanics Shanghai Key Laboratory of Mechanics in Energy Engineering and School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China The School of Sciences Shanghai Institute of TechnologyShanghai 200072China

In this paper,we investigate the Lagrangian coherent structures(LCSs)and their heat-transport mechanism in turbulent Rayleigh-Bénard(RB)convection.Direct numerical simulations(DNS)are performed in a closed square cell with Rayleigh numbers(Ra)ranging from 10^(6) to 10^(9) and Prandtl(Pr)number fixed at Pr=0.7.First,our results show the power-law relationship between Nusselt number(Nu)and Ra,Nu=0.99Ra^(0.30±0.02),confirming the results from previous studies.To gain insights into the material transport,LCSs are extracted using the finite-time Lyapunov exponent(FTLE)method.Interestingly,lobe structures are widely present,and we elucidate their role in transporting heat from the corner rolls to large-scale circulation.Next,the relationships between LCSs and thermal plumes are examined,and we identify two behaviors of thermal plumes:first,most plumes transport along the LCSs;second,few plumes are exposed to the bulk and subsequently mix with the turbulent background.Furthermore,we quantify the heat flux along the LCSs,which contributes to about 85%of the total flux regardless of Ra.This suggests that LCSs play a significant role in heat transport.Finally,the viscous(thermal)dissipation rate along the LCSs is quantified,which is larger than 80%(60%)of the total value,suggesting that LCSs are responsible for the large viscous and thermal dissipations.

关键词： Rayleigh-Bénard convection finite-time Lyapunov exponent Lagrangian coherent structures

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企业委托贷款制度的理论反思及其功能化构造

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山东大学学报（哲学社会科学版） 2024年第1期 178-192页

作者：冉克平张仪昭武汉大学法学院武汉430072 武汉大学武汉430072 柏林自由大学

企业委托贷款制度是企业融资创新与金融监管政策结合的产物,商业银行在委托贷款制度中的角色定位既有监管属性又有代理人特征。商业银行在金融法与民商法中的二元定位为委托贷款法律关系的厘清造成了混乱,不仅未能发挥更好的监督能效,... 详细信息

企业委托贷款制度是企业融资创新与金融监管政策结合的产物,商业银行在委托贷款制度中的角色定位既有监管属性又有代理人特征。商业银行在金融法与民商法中的二元定位为委托贷款法律关系的厘清造成了混乱,不仅未能发挥更好的监督能效,而且引发了不容小觑的金融风险。因此,规制委托贷款需要从民商法与金融法结合视角,通过厘清委托贷款中以商业银行为核心的内外部法律关系,合理安排委托贷款法律关系各方权利格局,实现商业银行民事责任的归位与强化,以维护主体间利益平衡。推动委托贷款立法与司法规制系统适配,行政监管与金融司法协调互补,以促进委托贷款理论革新与制度优化,实现防范化解重大金融风险的制度目标。

关键词：委托贷款监管属性代理特征民商法与金融法交叉防范化解重大金融风险

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Improving constraint on Ωfrom SDSS using marked correlation functions

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Science China(Physics,Mechanics & Astronomy) 2024年

作者： Limin Lai Jiacheng Ding Xiaolin Luo yizhao Yang Zihan Wang Keshi Liu Guanfu Liu Xin Wang Yi Zheng Zhaoyu Li Le zhang Xiaodong Li School of Physics and Astronomy Sun Yat-sen University Zhuhai Campus Department of Astronomy Shanghai Jiao Tong University Department of Astronomy Tsinghua University CSST Science Center for the Guangdong-Hong Kong-Macao Greater Bay Area SYSU Peng Cheng Laboratory

Large-scale structure （LSS） surveys will increasingly provide stringent constraints on our cosmological models.Recently,the density-marked correlation function （MCF） has been introduced,offering an easily computable density-correlation statistic.Simulations have demonstrated that MCFs offer additional,independent constraints on cosmological models beyond the standard two-point correlation （2PCF）.In this study,we apply MCFs for the first time to SDSS CMASS data,aiming to investigate the statistical information regarding clustering and anisotropy properties in the Universe and assess the performance of various weighting schemes in MCFs,and finally obtain constraints on Ωm.Upon analyzing the CMASS data,we observe that,by combining different weights （α=[-0.2,0,0.2,0.6]）,the MCFs provide a tight and independent constraint on the cosmological parameter Ωm,yielding Ωm=0.293±0.006 at the 1σlevel,which represents a significant reduction in the statistical error by a factor of 3.4compared to that from 2PCF.Our constraint is consistent with recent findings from the small-scale clustering of BOSS galaxies(Zhai et al.Astronphys.J.948,99 （2023）) within the 1σlevel.However,we also find that our estimate is lower than the Planck measurements by about 2.6σ,indicating the potential presence of new physics beyond the standard cosmological model if all the systematics are fully corrected.The method outlined in this study can be extended to other surveys and datasets,allowing for the constraint of other cosmological parameters.Additionally,it serves as a valuable tool for forthcoming emulator analysis on the Chinese Space Station Telescope （CSST）.

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Road map for, and technical challenges of, carbon-nanotube integrated circuit technology

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National Science Review 2024年第3期11卷 14-16页

作者： Jia Si Panpan zhang Zhiyong zhang Key Laboratory for the Physics and Chemistry of Nanodevices and Center for Carbon-based Electronics School of Electronics Peking University State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

The past decade has witnessed an explosion of research on carbon-nanotube(CNT) electronics due to their outstanding properties, including an ultrathin body, a high carrier mobility and a high saturation velocity.

关键词： TRANSISTORS

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New structure transistors for advanced technology node CMOS ICs

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National Science Review 2024年第3期11卷 24-41页

作者： Qingzhu zhang Yongkui zhang Yanna Luo Huaxiang Yin Integrated Circuit Advanced Process R&D Center Institute of Microelectronics of Chinese Academy of Sciences(IMECAS) State key Lab of Fabrication Technologies for Integrated Circuits Institute of Microelectronics of Chinese Academy of Sciences School of Integrated Circuits University of Chinese Academy of Sciences

Over recent decades, advancements in complementary metal-oxide-semiconductor integrated circuits(ICs)have mainly relied on structural innovations in transistors. From planar transistors to the fin field-effect transistor(FinFET) and gate-all-around FET(GAAFET), more gate electrodes have been added to three-dimensional(3D) channels with enhanced control and carrier conductance to provide higher electrostatic integrity and higher operating currents within the same device footprint. Beyond the 1-nm node, Moore's law scaling is no longer expected to be applicable to geometrical shrinkage. Vertical transistor stacking, e.g. in complementary FETs(CFET), 3D stack(3DS) FETs and vertical-channel transistors(VFET), for enhanced density and variable circuit or system design represents a revolutionary scaling approach for sustained IC development. Herein, innovative works on specific structures, key process breakthroughs, shrinking cell sizes and design methodologies for transistor structure research and development are reviewed. Perspectives on future innovations in advanced transistors with new channel materials and operating theories are also discussed.

关键词： transistor CMOS GAAFET CFET 3DS FET

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轻量化机器人抓取位姿实时检测算法

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浙江大学学报（工学版） 2024年第3期58卷 599-610页

作者：宋明俊严文邓益昭张俊然涂海燕四川大学电气工程学院四川成都610065

针对机器人对形状、大小、种类变化不一的未知物体的抓取,提出轻量化的抓取位姿实时检测算法RTGN,以进一步提升抓取检测准确率及检测速度.设计多尺度空洞卷积模块,以构建轻量化的特征提取主干网络;设计混合注意力模块,以加强网络对重要... 详细信息

针对机器人对形状、大小、种类变化不一的未知物体的抓取,提出轻量化的抓取位姿实时检测算法RTGN,以进一步提升抓取检测准确率及检测速度.设计多尺度空洞卷积模块,以构建轻量化的特征提取主干网络;设计混合注意力模块,以加强网络对重要抓取特征的关注;引入金字塔池化模块融合多层级特征,以提升网络对物体的抓取感知能力.在Cornell抓取数据集上进行测试,RTGN检测速度为142帧/s,在图像拆分和对象拆分上的检测准确率分别为98.26%和97.65%;在实际抓取环境下进行抓取实验,机器人对20类未知物体进行400次抓取,抓取成功率为96.0%.实验结果表明,RTGN的检测准确率和检测速度较现有方法有明显提升,对物体的位置和姿态变化具有较强的适应性,并且能够有效地泛化到形状、大小、种类等变化不一的未知物体的抓取检测中.

关键词：机器人抓取抓取检测注意力机制卷积神经网络深度学习非结构化环境

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Advances in methane emissions from agricultural sources:Part I.Accounting and mitigation

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Journal of Environmental Sciences 2024年第6期140卷 279-291页

作者： Xiaokun Wu Ying zhang Yinghui Han Yagang zhang Yuhang zhang Xiaodan Cheng Pei Zhong Xue Yuan Yuanxun zhang Zhengqiang Li State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China Hebei Key Laboratory of Physics and Energy Technology North China Electric Power UniversityBaoding 071003China College of Resources and Environment University of Chinese Academy of SciencesBeijing 101408China Interdisciplinary Mathematics Institute University of South CarolinaColumbiaSC 29208United States Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094China

Methane is one of the major greenhouse gases(GHGs)and agriculture is recognized as its primary emitter.Methane accounting is a prerequisite for developing effective agriculture mitigation strategies.In this review,methane accounting methods and research status for various agricultural emission source including rice fields,animal enteric fermentation and livestock and poultry manure management were overview,and the influencing factors of each emission source were analyzed and discussed.At the same time,it analyzes the different research efforts involving agricultural methane accounting and makes recommendations based on the actual situation.Finally,mitigation strategies based on accounting results and actual situation are proposed.This review aims to provide basic data and reference for agriculture-oriented countries and regions to actively participate in climate action and carry out effective methane emission mitigation.

关键词： Methane emission Agricultural sources Accounting methodology Mitigation Emission influencing factors

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Interface Engineering of Titanium Nitride Nanotube Composites for Excellent Microwave Absorption at Elevated Temperature

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Nano-Micro Letters 2024年第9期16卷 147-160页

作者： Cuiping Li Dan Li Shuai zhang Long Ma Lei zhang* Jingwei zhang Chunhong Gong College of Chemistry and Molecular Sciences Henan UniversityKaifeng 475004People’s Republic of China National and Local Joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials Henan UniversityKaifeng 475004People’s Republic of China

Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction loss.Consequently,the development of high-performance EMWA materials with good impedance matching and strong loss ability in wide temperature spectrum has emerged as a top priority.Herein,due to the high melting point,good electrical conductivity,excellent environmental stability,EM coupling effect,and abundant interfaces of titanium nitride(TiN)nanotubes,they were designed based on the controlling kinetic diffusion procedure and Ostwald ripening process.Benefiting from boosted heterogeneous interfaces between TiN nanotubes and polydimethylsiloxane(PDMS),enhanced polarization loss relaxations were created,which could not only improve the depletion efficiency of EMWA,but also contribute to the optimized impedance matching at elevated temperature.Therefore,the TiN nanotubes/PDMS composite showed excellent EMWA performances at varied temperature(298-573 K),while achieved an effective absorption bandwidth(EAB)value of 3.23 GHz and a minimum reflection loss(RLmin)value of−44.15 dB at 423 K.This study not only clarifies the relationship between dielectric loss capacity(conduction loss and polarization loss)and temperature,but also breaks new ground for EM absorbers in wide temperature spectrum based on interface engineering.

关键词： TiN nanotubes Interface engineering Polarization loss Impedance matching Electromagnetic wave absorption performance

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Environmental arsenic(As)and its potential relationship with endemic disease in southwestern China

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Journal of Environmental Sciences 2024年第5期139卷 46-59页

作者： Donglin Li Hucai zhang Fengqin Chang Lizeng Duan Yang zhang Institute for Ecological Research and Pollution Control of Plateau Lakes School of Ecology and Environmental ScienceYunnan UniversityKunming 650500China Southwest United Graduate School Kunming 650500China

Many cases of an unknown disease exhibiting the clinical features of limb gangrene,blisters,ulceration,and exfoliation have been reported in Daping village(DV)in southwestern China.However,the pathogenesis is unknown and has puzzled doctors for many years.A preliminary study on heavy metals and symptoms indicated that arsenic might pose the greatest threat to the health of local residents.Here,to explore the sources of and factors influencing arsenic enrichment in DV,whose residents exhibit signs of arsenic poisoning,the As contents in soil,water,and plants were systematically measured.The results indicated high As contents in plant and soil samples obtained from the area,and the source of As may be linked to the weathering of black shale rock.Ingestion of soil and consumption of plants were the two main As exposure pathways among children and adults,respectively,and children exhibited a higher health risk than adults.We presume and emphasize that when extreme drought events occur,humans might face unusual risks resulting from exposure to toxic elements and the direct consumption of highly polluted water.Our study provides a new perspective and sheds light on the environmental geochemistry and health links of this disease.

关键词： Endemic disease Arsenic(As) Risk assessment Black shale Climate change

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N-doped graphene quantum dot-decorated N-TiO2/P-doped porous hollow g-C_(3)N_(4) nanotube composite photocatalysts for antibiotic photodegradation and H2 production

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 165-178页

作者： Jingshu Yuan Yao zhang Xiaoyan zhang Junjie zhang Shen’gen zhang Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China Xi’an Fanyi University Xi’an 710105China Shunde Graduate School of University of Science and Technology Beijing Foshan 528399China State Key Laboratory of Lunar and Planetary Sciences Macao University of Science and TechnologyMacao SAR 820000China

Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

关键词： N-doped TiO_(2) N-doped graphene quantum dots P-doped g-C_(3)N_(4) porous hollow nanotube heterojunction photocatalysis

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