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A strong correlation between the bending rigidity and the length of single-walled carbon nanotubes

MATERIALS TODAY COMMUNICATIONS 2020年 24卷

作者： Liang, Haidong Wang, Qi Huang, Baoling Yao, Haimin He, Linghui Kuang, Youdi Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn Guangzhou Peoples R China Hong Kong Univ Sci & Technol Dept Mech & Aerosp Engn Kowloon Hong Kong Peoples R China Hong Kong Polytech Univ Dept Mech Engn Kowloon Hung Hom Hong Kong Peoples R China Univ Sci & Technol China Dept Modern Mech Hefei Peoples R China

Continuous efforts to discover the novel carbon nanotube ultrahigh frequency resonators or sensors have being made since past two decades. The bending rigidity plays a key role in determining the frequency magnitude. Although it is previously justified that the bending rigidity has the almost linear dependence on the cubic of tube diameter, its dependence on another characteristic scale, i.e., the tube length is missing. Considering that the direct experimental observation faces significant challenge due to the low measurement precision by the inevitable thermodynamic fluctuation, we theoretically explored such size effect by means of three approaches respectively at different scale levels including quantum mechanics lattice dynamics calculations, molecular mechanics simulations and nonlocal continuum modeling for single-walled carbon nanotubes. The results from the different approaches give the consistent conclusion that there exists a strong correlation between the tube length and the bending rigidity, i.e., the rigidity increases with the tube length and converges to the value predicted by continuum theories. Moreover, we also find the nonlocal parameter reflecting the microscopic lattice effect in present continuum modeling almost independent of the chirality and linearly increases with the tube diameter with a scale factor 1.5. The comprehensive study may not only guide the design of ultrahigh frequency carbon nanotube devices but also provide insight to the bending nanomechanics of other devices made from nanotubes, nanobeams and nanowires.

关键词： Carbon nanotubes Bending rigidity Lattice dynamics Molecular mechanics Nonlocal continuum theories

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Static and dynamic tensile behaviors of BFRP bars embedded in seawater sea sand concrete under marine environment

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COMPOSITES PART B-engineering 2022年 242卷

作者： Li, Sheng Zhu, Deju Guo, Shuaicheng Xi, Huifeng Rahman, Md Zillur Yi, Yong Fu, Bing Shi, Caijun Hunan Univ Coll Civil Engn Key Lab Green & Adv Civil Engn Mat & Applicat Tech Changsha 410082 Peoples R China Hunan Univ Int Sci Innovat Collaborat Base Green & Adv Civil Changsha 410082 Peoples R China Hunan Univ Key Lab Bldg Safety & Energy Efficiency Minist Educ Changsha 410082 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Ahsanullah Univ Sci & Technol Dept Mech Engn Dhaka 1208 Bangladesh Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Basalt fiber reinforced polymer (BFRP) bars can be used as an appropriate substitute for steel rebars in marine concrete structures due to their corrosion-free nature and high tensile performance. However, the long-term dynamic properties of BFRP bars in the marine environment are not well known, which is critical for structural safety when subjected to external dynamic loads (e.g., tsunamis and earthquakes). Therefore, this study investigates the static and dynamic tensile behaviors of BFRP bars after exposure to the seawater sea sand concrete (SWSSC) under marine environment. Accelerated corrosion tests were conducted under various exposure periods (60, 90, and 120 days) and temperatures (25, 40, and 55 C). Both optical stereo microscope (OSM) and scanning electron microscope (SEM) were used to examine the failure patterns of BFRP bars, whereas the degradation mechanisms were investigated by X-ray micro-computed tomography (micro-CT), SEM, and Fourier transform infrared spectroscopy (FTIR). Results show that the tensile properties of BFRP bars are sensitive to strain rate. Both the tensile strength and the elastic modulus of BFRP bars increase with increasing strain rate, but the failure strain drops. The tensile strength and failure strain reduce with increasing exposure temperature and duration, whereas the elastic modulus does not change significantly. Microstructure analysis clearly reveals that failures of BFRP bars occur due to fiber breakage, matrix cracking, and interface debonding. The basalt fibers always exhibit brittle fracture, but the fracture surfaces change from relatively flat to rough when the strain rate increases. Moreover, the deterioration of BFRP bars is caused by resin hydrolysis, fiber-resin interfaces debonding and fiber damage after corrosion. These results can provide some insights to promote the application of BFRP composites in coastal and marine structures.

关键词： BFRP bars Seawater sea sand concrete Marine environment Tensile properties Strain rate Failure patterns

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Aqueous Ammonia With Sodium Sulfite Pretreatment For Enhancing Enzymatic Saccharification and Bioethanol Production of Sugarcane Bagasse

Research Square

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Research Square 2021年

作者： Zeng, Minxia Tang, Baoying Li, Peijin Liang, Zhiquan Li, Xiaozhen Wang, Jue Lin, Jianghai Xiao, Wenjuan Xu, Yuan Huang, Shiqing Liu, Zehuan Research Center for Molecular Biology Institute of Life and Health Engineering College of Life Science and Technology Jinan University Guangzhou510632 China MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China Guangzhou Institute of Low-carbon Biotechnology China

Background: Bioethanol is considered as a promising alternative fuel. Lignocellulosic biomass can be used for the production of bioethanol, but its recalcitrant structure makes it difficult to be utilized. Thus, proper pretreatment is a crucial step to break this structure and enhance enzymatic saccharification. Aqueous ammonia with sodium sulfite pretreatment (AAWSSP) was first applied to enhance the enzymatic saccharification and bioethanol production of sugarcane bagasse (SCB) in this research. Results: Response surface methodology was applied to optimize the conditions of pretreatment. Under optimal parameters, 16.92 g/L of total sugar concentration (P1 SCB: 202.08℃, 11.06% aqueous ammonia, 13.37% sodium sulfite, 1.22 h) and 0.51 g/g of total sugar yield (P2 SCB: 199.47℃, 10.17% aqueous ammonia, 13.11% sodium sulfite, 1.17 h) were achieved, respectively. The results of ethanol fermentation showed that separate hydrolysis and fermentation performed better than that of simultaneous saccharification and fermentation, and the maximum ethanol yields of 143.30 g/kg for P1 SCB and 145.33 g/kg for P2 SCB, were obtained, respectively. Conclusions: This research indicated that aqueous ammonia and sodium sulfite in pretreatment solution might have a synergistic effect on delignification and enzymatic saccharification. AAWSSP might be a prospective method for enhancing enzymatic saccharification and bioethanol production of SCB, which provided new guidance for the bio-refinery of lignocellulose. © 2021, CC BY.

关键词： Ethanol

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Mathematical modelling of axonal microtubule bundles under dynamic torsion

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Applied Mathematics and Mechanics(English Edition) 2018年第6期39卷 829-844页

作者： J.Y.WU Hong YUAN L.Y.LI MOE Key Laboratory of Disaster Forecast and Control in Engineering Institute of Applied MechanicsJinan University School of Engineering University of Plymouth

Owing to its viscoelastic nature, axon exhibits a stress rate-dependent me- chanical behavior. An extended tension-shear chain model with Kelvin-Voigt viscoelas- ticity is developed to illustrate the micromechanical behavior of the axon under dynamic torsional conditions. Theoretical closed-form expressions are derived to predict the de- formation, stress transfer, and failure mechanism between microtubule （MT） and tau protein while the axon is sheared dynamically. The results obtained from the present an- alytical solutions demonstrate how the MT-tau interface length, spacing between the tau proteins, and loading rate affect the mechanical properties of axon. Moreover, it is found that the MTs are more prone to rupture due to the contributions from the viscoelastic effects. Under the torsional force, the MTs are so long that the stress concentrates at the loaded end where axonal MTs will break. This MT-tau protein dynamics model can help to understand the underlying pathology and molecular mechanisms of axonal injury. Additionally, the emphasis of this paper is on the micromechanical behavior of axon, whereas this theoretical model can be equally applicable to other soft or hard tissues, owning the similar fibrous structure.

关键词： torsion biocomposite diffuse axonal injury （DAI） Kelvin-Voigt viscoelas-tic model dynamic response tension-shear chain model

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A unified simulation for effects of gellan polymer concentrations on large strain elastic behaviors of gellan gels

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MULTIDISCIPLINE MODELING IN MATERIALS AND STRUCTURES 2019年第5期15卷 859-870页

作者： Ding, Xie-Fei Zhan, Lin Xi, Hui-Feng Xiao, Heng Shanghai Univ Shanghai Inst Appl Math & Mech Shanghai Peoples R China Sch Mech & Construct Engn Guangzhou Guangdong Peoples R China MOE Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China

Purpose A direct and unified approach is proposed toward simultaneously simulating large strain elastic behaviors of gellan gels with different gellan polymer concentrations. The purpose of this paper is to construct an elastic potential with certain parameters of direct physical meanings, based on well-designed invariants of Hencky's logarithmic strain. Design/methodology/approach For each given value of the concentration, the values of the parameters incorporated may be determined in the sense of achieving accurate agreement with large strain uniaxial extension and compression data. By means of a new interpolating technique, each parameter as a function of the concentration is then obtained from a given set of parameter values for certain concentration values. Findings Then, the effects of gellan polymer concentrations on large strain elastic behaviors of gellan gels are studied in demonstrating how each parameter relies on the concentration. Plane-strain (simple shear) responses are also presented for gellan gels with different polymer concentrations. Originality/value A direct, unified approach was proposed toward achieving a simultaneous simulation of large elastic strain behaviors of gellan gels for different gellan polymer concentrations. Each parameter incorporated in the proposed elastic potential will be derived as a function of the polymer concentration in an explicit form, in the very sense of simultaneously simulating large strain data for different concentrations.

关键词： Elastic potential Gellan gels Gellan polymer concentration Hencky strain Large elastic deformation Simultaneous simulation

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Simultaneous strength-ductility enhancement in as-cast Ti6Al4V alloy by trace Ce

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MATERIALS & DESIGN 2022年 215卷

作者： Li, K. M. Liu, Y. J. Liu, X. C. Wu, X. Zhou, S. F. Zhang, L. C. Li, W. Zhang, W. C. Changsha Univ Sci & Technol Inst Met Coll Mat Sci & Engn 9602 Sect Changsha 410004 Hunan Peoples R China Jinan Univ Inst Adv Wear & Corros Resistance & Funct Mat Key Lab Disaster Forecast & Control Engn MOE Guangzhou 510632 Guangdong Peoples R China Edith Cowan Univ Sch Engn 270 Joondalup Dr Perth WA 6027 Australia Jinan Univ Affiliated Hosp 1 Guangzhou 510632 Guangdong Peoples R China

Impurity elements always play a major role in hindering mechanical property improvement in Ti6Al4V, and specifically most of them e.g. O, P, Cl, and S dissolved in the matrix deteriorate the mechanical properties of Ti6Al4V. This work presents a strategy of enhancing the mechanical performance of as-cast Ti6Al4V alloy by adding a small amount of rare earth (i.e. 0.1 wt% Ce), where deleterious elements could be absorbed from the crystalline lattice during solidification process, forming uniformly distributed Cerich oxides or precipitates with-200 nm in size. The Ce-rich precipitates in turn refine the beta phase lamellae by introducing more nucleation in the cast alloy, which further enhances the strength. As such, the cast Ti6Al4V with Ce addition exhibits a tensile strength of 957 +/- 47 MPa and elongation of 12.3%, which exhibits a simultaneous strength-ductility enhancement compared with the Ti6Al4V counterpart (787 +/- 65 MPa and 8.8%). In addition, the Ce-rich precipitates also pin dislocation motions, which effectively shields the stress concentration at the crack tip and deflects the crack propagation during fracture process.(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://***/licenses/by/4.0/).

关键词： Rare earth Ce Titanium Mechanical properties Geometrically-necessary dislocations Slip systems

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Ill-Posedness Determination of Moving Force Identification and Parameters Selection for Regularization Methods

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INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS 2021年第8期21卷

作者： Chen, Zhen Sun, Pudong Chan, Tommy H. T. Yu, Ling North China Univ Water Resources & Elect Power Sch Civil Engn & Commun Zhengzhou 450045 Peoples R China Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Queensland Univ Technol QUT Sch Civil & Environm Engn Brisbane Qld 4000 Australia

Moving force identification (MFI) from dynamic responses of bridges is a typical inverse problem with ill-posedness. Under the efforts of researchers, some regularization methods have been presented to solve the ill-posed problem, but there still lacks an effective index to reveal the ill-posedness of the vehicle-bridge dynamic system such that it can be utilized as a guidance for the regularization parameter selection. In this paper, an ill-posedness indicator (IPI) defined as the ratio of the Fourier coefficient to the singular value is adopted to reveal the ill-posedness in the MFI problem. Simulation results show that the larger the IPI value is, the more obvious the ill-posedness of the vehicle-bridge system equation, namely, the intrinsic factor of ill-posedness in MFI is attributed to very large IPI value. The maximum IPI value increases with the increasing noise level, which leads directly to the ill-posedness of the vehicle-bridge system equation. In addition, a relative percentage error (RPE) is used to select the optimal regularization parameters, while evaluating the ill-posedness existing in the MFI. Using the proposed IPI value, the influence of ill-posedness on identified results is evaluated in this study, which can assist qualitatively and quantitatively in selecting optimal regularization parameters and proper regularization methods.

关键词： Vehicle bridge moving force identification Fourier coefficient ill-posedness indicator relative percentage error

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The 2022 report of synergetic roadmap on carbon neutrality and clean air for China:Accelerating transition in key sectors

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Environmental Science and Ecotechnology 2024年第3期19卷 4-18页

作者： Yu Lei Zhicong Yin Xi Lu Qiang Zhang Jicheng Gong Bofeng Cai Cilan Cai Qimin Chai Huopo Chen Renjie Chen Shi Chen Wenhui Chen Jing Cheng Xiyuan Chi Hancheng Dai Xiangzhao Feng Guannan Geng Jianlin Hu Shan Hu Cunrui Huang Tiantian Li Wei Li Xiaomei Li Jun Liu Xin Liu Zhu Liu Jinghui Ma Yue Qin Dan Tong Xuhui Wang Xuying Wang Rui Wu Qingyang Xiao Yang Xie Xiaolong Xu Tao Xue Haipeng Yu Da Zhang Ning Zhang Shaohui Zhang Shaojun Zhang Xian Zhang Xin Zhang Zengkai Zhang Bo Zheng Yixuan Zheng Jian Zhou Tong Zhu Jinnan Wang Kebin He Center of Air Quality Simulation and System Analysis Chinese Academy of Environmental PlanningBeijing100041China Center for Carbon Neutrality Chinese Academy of Environmental PlanningBeijing100041China Key Laboratory of Meteorological Disaster Ministry of Education/Joint International Research Laboratory of Climate and Environment Change(ILCEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD)Nanjing University of Information Science&TechnologyNanjing210044China State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China Institute for Carbon Neutrality Tsinghua UniversityBeijing100084China Ministry of Education Key Laboratory for Earth System Modelling Department of Earth System ScienceTsinghua UniversityBeijing100084China State Key Joint Laboratory for Environment Simulation and Pollution Control College of Environmental Sciences and Engineering and Center for Environment and HealthPeking UniversityBeijing100871China National Center for Climate Change Strategy and International CooperationBeijing100035China Nansen-Zhu International Research Centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing100029China School of Public Health Key Lab of Public Health Safety of the Ministry of Education and Key Lab of Health Technology Assessment of the Ministry of HealthFudan UniversityShanghai200032China School of Economics and Management Beijing University of Chemical TechnologyBeijing100029China Department of Earth System Science University of CaliforniaIrvineCA92697USA National Meteorological Center China Meteorological AdministrationBeijing100081China College of Environmental Sciences and Engineering Peking UniversityBeijing100871China Policy Research Center for Environment and Economy Ministry of Ecology and Environment of the People's Republic of ChinaBeijing100029China Jiangsu Key Laboratory of Atmospheric Environment Monitoring

China is now confronting the intertwined challenges of air pollution and climate *** the high synergies between air pollution abatement and climate change mitigation,the Chinese government is actively promoting synergetic control of these two *** Synergetic Roadmap project was launched in 2021 to track and analyze the progress of synergetic control in China by developing and monitoring key *** Synergetic Roadmap 2022 report is the first annual update,featuring 20 indicators across five aspects:synergetic governance system and practices,progress in structural transition,air pollution and associated weather-climate interactions,sources,sinks,and mitigation pathway of atmospheric composition,and health impacts and benefits of coordinated *** to the comprehensive review presented in the 2021 report,the Synergetic Roadmap 2022 report places particular emphasis on progress in 2021 with highlights on actions in key sectors and the relevant *** milestones include the proportion of non-fossil power generation capacity surpassing coal-fired capacity for the first time,a decline in the production of crude steel and cement after years of growth,and the surging penetration of electric ***,in 2022,China issued the first national policy that synergizes abatements of pollution and carbon emissions,marking a new era for China's pollution-carbon *** changes highlight China's efforts to reshape its energy,economic,and transportation structures to meet the demand for synergetic control and sustainable ***,the country has witnessed a slowdown in carbon emission growth,improved air quality,and increased health benefits in recent years.

关键词： Synergetic roadmap Carbon neutrality Clean air

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Compressed sensing for moving force identification using redundant dictionaries

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2020年第0期138卷 106535-000页

作者： Liu, Huanlin Yu, Ling Luo, Ziwei Pan, Chudong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Guangzhou Univ Sch Civil Engn Guangzhou 510006 Peoples R China

Moving force identification (MFI) techniques have been widely studied in recent years. However, the contradiction between response acquisition and energy consumption limits applications of existing MFI methods and has become one of the most prominent issues in the field of structural health monitoring (SHM). In fact, sample length of response data can be shortened by exploiting compressed coefficients of responses based on compressed sensing (CS) theory. In order to mitigate this contradiction and to study if these compressed coefficients can be efficiently exploited for MFI, a novel method is proposed for MFI based on CS with redundant dictionaries in this study. Firstly, a redundant dictionary is designed for creating a sparse expression on each moving force based on prior knowledge of moving forces. Then, by the aid of relationship between moving forces and responses, an indirect way is presented to design dictionaries for different types of structural responses, sparse expression of responses is established simultaneously, and a MFI governing equation is formulated by directly exploiting compressed coefficients of responses via CS. Moreover, sparse regularization is introduced to ensure the accuracy of MFI results. Finally, the proposed method is validated by both numerical simulations and experimental verifications. The illustrated results show that the sample length of each acquired data can be obviously shortened and the compressed coefficients rather than structural responses can be directly used for MFI. The identified moving forces are in good agreement with the true ones, which shows the effectiveness and applicability of the proposed method. In addition, the proposed method can estimate the total weight of the car with a good accuracy and a strong robustness to noise. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Moving force identification (MFI) Compressed sensing (CS) Redundant dictionary Sparse regularization Structural health monitoring (SHM)

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Analysis of the Effect of Urban Geometric Form Factors on Heat Islands in Guangzhou

Analysis of the Effect of Urban Geometric Form Factors on He...

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作者： Langtao Zheng Jian Tang Xiong Chen Guangdong Engineering Technology Research Center for Green Building Materials and Fabricated Architecture MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University

The geometric form factors of urban space include height width ratio(H/W), sky view factor(SVF) and street direction, which directly affect the incidence of solar radiation, and then affect the temperature change of the block. In this study, the representative hot island and cold island streets in Guangzhou are selected as the research objects. According to the intensity and range distribution map of Guangzhou heat island in summer of 2014-2017 issued by Guangzhou Meteorological Bureau, the intersection area with high intensity of 4-year continuous heat island is found out by two-dimensional image superposition. In the region, the typical measurement points and comparison points are selected in groups, the temperature of each measurement point is monitored, and the urban geometry data is collected for comparative analysis. The results show that under the condition of the same underlying surface factor and no significant difference in artificial heat factor, the urban geometry can alleviate the heat island effect, and the measuring points with smaller sky view factor and larger height width ratio(H/W) have lower temperature, and the temperature of each measuring point has higher correlation with the size of SVF. In addition, the direction defined by the long axis of the valley will also affect the solar radiation equivalent of the street pavement, and the reclamation open land is also easy to become a heat island area.

关键词： Urban heat island (UHI) sky view factor (SVF) spatial geometric form factor open area of reclamation

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