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Gap results for compact quasi-Einstein metrics

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Science China Mathematics 2018年第5期61卷 943-954页

作者： linfeng wang School of Science Nantong University

In this paper, we work on compact quasi-Einstein metrics and prove several gap results. In the first part, we get a gap estimate for the first nonzero eigenvalue of the weighted Laplacian, by establishing a comparison theorem for the weighted heat kernel. In the second part, we establish two gap results for the Ricci curvature and the scalar curvature, based on which some rigid properties can be derived.

关键词： quasi-Einstein metric heat kernel eigenvalue diameter Ricci curvature scalar curvature gap result

Contact Electrification and Adhesion Between Carbon Nanotube and Graphene on Metal Surfaces: Insights from First-principles Study

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Journal of Bionic Engineering 2022年第1期19卷 103-112页

作者： Jing Tao linfeng wang Jin Li Zhendong Dai Jiangsu Provincial Key Laboratory of Bionic Functional Materials College of Mechanical and Electrical EngineeringNanjing University of Aeronautics and AstronauticsNanjing210016China College of Aerospace Engineering Nanjing University of Aeronautics and AstronauticsNanjing210016China

The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion *** understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles *** transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function ***,the adhesion energy is linearly related to the transferred charge for both CNT and *** charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal *** curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge ***,the curved structure induces electronic localization,which also decreases the interfacial charge *** structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different *** study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.

关键词： Contact electrification Adhesion Bio-inspired adhesive CNT First-principles calculation Interfacial interaction

Effects of the Tensile and Shear Properties of Bolts on the Shear Properties of Bolted Rock Joints

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Journal of Earth Science 2024年第5期35卷 1626-1639页

作者： Chenlu wang Luobin Zheng Liangqing wang linfeng Zhu Shanbai Wu Shan Deng Faculty of Engineering China University of GeosciencesWuhan 430074China

The mechanical properties of bolts are important factors affecting the shear behavior of bolted *** this study,tensile and pure shear tests were conducted on five kinds of bolts made from different materials to measure their tensile and shear *** shear tests were conducted to analyze the effects of tensile and shear strength parameters on the shear behavior of bolted *** test results showed that the mechanical properties of bolts made from different materials were clearly different and that these differences mainly affected the plastic deformation stage of the bolted *** larger the bolt elongation was,the larger the joint shear displacement at bolt *** tensile and shear strengths of the bolts were positively correlated with the shear strength of the bolted *** to the standard regression analysis,the bolt shear strength had a greater influence than the bolt tensile strength on the bolt contributions when the bolts were perpendicular to the joint *** on the empirical equation for the bolt contribution proposed by Spang,the maximum shear loads in the pure shear test were introduced,and a new equation was established to predict the contributions of *** prediction results obtained using the modified equation were in good agreement with the experimental results.

关键词： rock bolt shear strength bolt contribution mechanical property engineering geology

Microstructure and strength in ultrastrong cold-drawn medium carbon steel

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Journal of Materials Science & Technology 2022年第2期97卷 89-100页

作者： Hanchen Feng Lei Cai linfeng wang Xiaodan Zhang Feng Fang Jiangsu Key Laboratory of Advanced Metallic Materials Southeast UniversityNanjing 211189China Sunnywell(China)New Material Technology Co.Ltd Changzhou 213200China Technical center of Baosteel Metal Co. LtdShanghai 200940China Department of Mechanical Engineering Technical University of DenmarkLyngbyDenmark

Via traditional wire drawing,the medium carbon ferrite-pearlite(MCFP)steel wires can achieve the ultrahigh strength beyond 4 GPa normally for high-carbon pearlitic steel wires,but have a 30-60%lower production *** microstructural evolution and mechanical properties of medium carbon ferrite-pearlite steel wires have been investigated by means of scanning electron microscopy,transmission electron microscopy and tensile *** tensile strength of medium carbon ferrite-pearlite steel wires increases from 750 MPa up to 4120 MPa when the drawing strain increases up toε=6.4,which represents the highest strength reported so far-to our knowledge for a carbon steel with such low carbon *** low and medium strains(ε≤1.95),the proeutectoid ferrite forms dense dislocation walls(DDWs)via dislocation activities,including sliding,accumulation,interaction,and *** the drawing strain increase,the reorientation of DDWs to the drawing direction forms the coarse proeutectoid ferrite ***,the proeutectoid ferrite deformed to high strains is characterized by a lamellar morphology and the average lamellar spacing of proeutectoid ferrite is about 55 nm atε=*** interlamellar spacing of pearlite and thickness of cementite decreases with the drawing strain *** dislocation density in ferrite lamellae increases with the drawing strain increases,and the dislocation density in ferrite lamellae is 7.8×10^(15)m^(2)atε=4.19.A higher dislocation density of 3.1×10^(16)m^(2)can be obtained atε=6.4 by means of extrapolation and TEM *** stress contributions of proeutectoid ferrite and pearlite to the flow stress are estimated based on quantified structural *** on the assumption that the stress contributions from different strengthening mechanisms are linearly additive and the general rule of mixtures,a good agreement between the measured and estimated flow stresses has been found in a large range of flow *** good applica

关键词： Medium carbon ferrite-pearlite steel Strengthening mechanisms Microstructure Mechanical properties Strength

Dynamic Stability and Fuzzy Reliability Analysis of Toppling Perilous Rock Under Seismic Excitation

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Journal of Earth Science 2024年第1期35卷 248-262页

作者： linfeng wang Jixu Zhang Wanchun Xia Xiaoming Huang Guojin Tan Key Laboratory of Geological Hazards Mitigation for Mountainous Highway and Waterway Chongqing Jiaotong UniversityChongqing 400074China School of Transportation Southeast UniversityNanjing 211189China College of Transportation Jilin UniversityChangchun 130012China

To predict the occurrence of the collapse disaster in toppling perilous rock under the action of bidirectional earthquakes,the dynamic stability and fuzzy reliability calculation method of toppling perilous rock under the action of bidirectional earthquakes is ***,the mass viscoelasticity model is used to simulate two main control surfaces of toppling perilous rock,the seismic dynamic response model and motion equation of toppling perilous rock are established based on the D'Alembert principle,and the Newmark-β method is used to solve the dynamic motion ***,the instability event of toppling perilous rock is considered a fuzzy event,the membership function expression of the stability coefficient of toppling perilous rock is determined based on the fuzzy failure criterion,the calculation equations of the toppling perilous rock dynamic stability coefficient and fuzzy reliability are established,and the fuzzy reliability evaluation method based on the probability distribution of reliability is ***,the influence of different superposition modes of seismic excitation on the fuzzy reliability of toppling perilous rock is *** calculation results of toppling perilous rock in the engineering case show that the fuzzy reliability calculated after considering the fuzzy failure criterion is reduced by 10.73% to 25.66% compared with the classical *** the bidirectional seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 5.46% to 14.89%.Compared with using the acceleration peak time encounter mode to superpose the seismic excitation,the fuzzy reliability of toppling perilous rock is reduced by 3.4% when the maximum action effect time encounter mode is adopted.

关键词： toppling perilous rock bidirectional earthquake fuzzy failure criterion dynamic stability fuzzy reliability Newmark-βmethod probability distribution function

A 10 bit 200 MS/s pipeline ADC using loading-balanced architecture in 0.18 μm CMOS

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Journal of Semiconductors 2017年第7期38卷 103-110页

作者： linfeng wang Qiao Meng Hao Zhi Fei Li Institute of RF- & OE-ICs Southeast University Nanjing 210096 China

A new loading-balanced architecture for high speed and low power consumption pipeline analog-todigital converter（ADC） is presented in this paper. The proposed ADC uses SHA-less, op-amp and capacitor-sharing technique, capacitor-scaling scheme to reduce the die area and power consumption. A new capacitor-sharing scheme was proposed to cancel the extra reset phase of the feedback capacitors. The non-standard inter-stage gain increases the feedback factor of the first stage and makes it equal to the second stage, by which, the load capacitor of op-amp shared by the first and second stages is balanced. As for the fourth stage, the capacitor and op-amp no longer scale down. From the system＇s point of view, all load capacitors of the shared OTAs are balanced by employing a loadingbalanced architecture. The die area and power consumption are optimized maximally. The ADC is implemented in a 0.18 μm 1P6M CMOS technology, and occupies a die area of 1.2×1.2 mm^2. The measurement results show a 55.58 dB signal-to-noise-and-distortion ratio（SNDR） and 62.97 dB spurious-free dynamic range（SFDR） with a 25 MHz input operating at a 200 MS/s sampling rate. The proposed ADC consumes 115 m W at 200 MS/s from a 1.8 V supply.

关键词： pipeline ADC loading-balanced op-amp sharing SHA-Less MDAC scaling down

A Thrice-Told Tale of Japanese Staffrooms and a Transformative Journey in Searching for East Asia as Method

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ECNU Review of Education 2024年第3期7卷 618-640页

作者： Yanping Fang linfeng wang Nanyang Technological University Osaka Kyoiku University

Purpose:This study aims to search for fitting lenses to view and interpret teacher learning in a Japanese secondary school teacher staffroom and capture the reconstituting of researcher subjectivities in this ***/Approach/Methods:A narrative approach chronically documents the findings and use of the lenses in analyzing the staffroom daily interactions and traces the journey of transformation inour researcher ***:The telling of a Japanese staffroom(shokuinshitsu)as a thrice-told tale under the three lenses—cultural-historic activity theory,contextualism,and intimacy orientationeach uncovers a unique interpretation of the learning going on in the daily life of the Japanese *** complementary,Western-lenses are found to be unable to explain the nature of the everyday practices in the staffroom formed under the worldviews and ethics of East *** critical examination of the major academic encounters involved in the past two decades illuminates the complex dynamism behind our research perspectives,awakens us to the dominance of Western-centralism in our researcher subjectivities,transforms our worldviews,and returns us to our cultural roots to build alternative frames of reference as East Asia as ***:This study not only uniquely demonstrates what decentered,alternative,and diversified frames of reference would look like in studying East Asian practices but also what it would take for scholars to move toward East Asia as ***,going beyond the three lenses,it contributes to our understanding of how space(staffroom as an entity)mediates forming of the character of those who are dwellers of the shokuinshitsu.

关键词： East Asia as method space as a mediating entity teacher learning teacher staffrooms in Japan and East Asia transforming researcher subjectivities

Effect of Supported Bearing Clearance on Load-Sharing Characteristics of a Double-Row Planetary Gear System

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Journal of Donghua University(English Edition) 2021年第2期38卷 140-147页

作者： wang linfeng LIU Jing College of Mechanical and Vehicle Engineering Chongqing UniversityChongqing 400044China School of Marine Science and Technology Northwestern Polytechnical UniversityXi an 710072China

Few studies were focused on the load-sharing characteristics of double-row planetary gear(DRPG)systems with ***,the supported bearing has an important influence on the transmission characteristics of the entire *** overcome this problem,a multi-body dynamic(MBD)model of the DRPG system fully considering the influences of bearing parameters is *** loads among contacting gear pairs have been obtained to calculate the load-sharing coefficient(LSC)of the *** LSC of each gear tooth pair has been compared to study the effect of the supported bearing clearance on the load-sharing *** methods are based on Hertz contact *** liner stiffness and damping are used in the *** results show that the supported bearing clearance has a greatly effect on the LSC of the DRPG *** appropriate clearance parameters of supported bearing can help suppress the uneven load distribution of the DRPG *** results can provide some guidance to find new method to study the LSC and increase the service life of planetary gear systems.

关键词： double-row planetary gear(DRPG)system supported bearing clearance load-sharing coefficient(LSC) multi-body dynamic(MBD)

Enabling ultranarrow blue emission linewidths in colloidal alloy quantum dots by decreasing the exciton fine structure splitting and exciton–phonon coupling

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Nano Research 2023年第1期16卷 1576-1585页

作者： Jinke Bai linfeng wang Tingting Zhang Tianyi Hou Meilun Zhang Bing Xu Dongyu Li Xiao Jin Qinghua Li Yuxiao wang Xueru Zhang Yinglin Song Department of Physics Harbin Institute of TechnologyHarbin 150001China Guangdong Provincial Key Laboratory of Development and Education for Special Needs Children Lingnan Normal UniversityZhanjiang 524048China

The realization of colloidal alloy quantum dots(QDs)with narrow spectral linewidths requires minimization of the contributions of inhomogeneous and homogeneous broadening to the ensemble ***,there has been remarkable progress in eliminating the inhomogeneous contribution by controlling the size distribution of the ***,considerable challenges remain in suppressing the homogeneous broadening,in terms of both intrinsic principles and rational synthetic *** find that ground-state exciton fine structure splitting and exciton-phonon coupling play a pivotal role in the homogeneous broadening *** we demonstrate that the elimination of the lattice mismatch strain by using a coherent strain structure can decrease the light-heavy hole splitting,thus suppressing the asymmetric broadening of the emission on the high energy ***,the improvement of the uniformity of the alloy by using a stepwise ion exchange strategy can weaken the exciton-longitudinal optical(LO)-phonon interactions,further minimizing the homogeneous *** a result,the final alloy QD products exhibit a widely tunable blue emission wavelength(445-470 nm)with the narrowest ensemble photoluminescence full width at half maximum(FWHM)of 10.1-13.5 nm(or 58.4-75.3 meV).Our study provides a potential strategy for other semiconductor nanocrystals with ultranarrow spectral linewidths.

关键词： alloy quantum dots spectral linewidth light-heavy hole splitting exciton-phonon coupling homogeneous broadening