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How ploughing and frictional melting regulate ice-skating friction

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摩擦:英文版 2023年第11期11卷 2036-2058页

作者： Feng DU peng ke Ping HONG School of Transportation Science and Engineering Beihang UniversityBeijing 100191China Beijing Sports University Beijing 100084China

The slipperiness of ice is well known while,for ice skating,its mechanism still needs further investigation,where the complex interactions including the thermal conduction of the skate–meltwater–ice system,the ploughing and the frictional melting of ice to the friction force are still unclear.This study presents a theoretical framework and a simplified analytical solution to unveil the friction mechanism when a curved skate sliding on ice.The theory is validated by experiments and the effects of these various factors,including the sliding velocity,the ice temperature,the supporting weight,and the geometry of the skate blade to the friction are revealed in detail.This study finds that the contribution of friction force from the ploughing deformation through skate indentation and that from the fluid friction through the shear motion of the meltwater layer is comparable with each other,which thus clarifies how the ploughing deformation of the ice substrate together with its frictional melting regulates the friction during skating.

关键词： ice friction skating ploughing frictional melting coefficient of friction

Effects of the windshield inclination angle on head/brain injuries in car-to-pedestrian collisions using computational biomechanics models

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Transportation Safety and Environment 2024年第2期6卷 1-12页

作者： Fang Wang Mingliang Wang Lin Hu ke peng Jiajie Yin Danqi Wang Liangliang Shi Zhou Zhou School of Automotive and Mechanical Engineering Changsha University of Science and TechnologyChangsha 410114HunanChina Hunan Province key Laboratory of Safety Design and Reliability Technology for Engineering Vehicle Changsha University of Science and TechnologyChangsha 410114HunanChina State key Laboratory of Vehicle NVH and Safety Technology China Automotive Engineering Research Institute Co.Ltd.Chongqing 401122China Division of Neuronic Engineering KTH Ro y al Institute of TechnologyStockholm 14152Sweden

Car-to-pedestrian collision(CPC)accidents occur frequently,and pedestrians often suffer serious head/brain injuries.One major cause is the primary impact with the windshield.Here,we use an umerical sim ulation method to study the influence of the windshield in-clination angle of a passenger car on pedestrian head/brain injury due to CPC accidents.The range of the windshield inclination angle was set at 24°-50°,with an interval of 2°.The results show that the windshield angle significantly affects the pedestrian kine-matics and exerts different effects on the head injury when evaluating with various head injury criteria.Regarding the head peak linear/rotational acceleration and acceleration-based head injury criterion(HIC)/rotational injury criterion(RIC),the predictions at the secondary impact stage have no clear relationship with the windshield angle(R^(2)=0.04,0.07,0.03 and 0.26,respectively)and their distributions are scattered.In the primary impact,the peak linear acceleration and HIC show a weak trend of first decreasing and then increasing with the increasing of the windshield angle,and the rotational acceleration and RIC tend to remain relatively con-stant.Regarding the cum ulative strain dama ge measure(CSDM)criterion,the predictions at the primary impact are slightly lower than those at the secondary impact,and the trend of first decreasing and then increasing with the increase in the windshield angle is observed at both impact stages.When the windshield inclination angle is approximately 32°-40°,the head injury severity in both impact phases is generally lower than that predicted at other windshield angles.

关键词： car-to-pedestrian collision(CPC) head/brain injury head injury criterion(HIC) windshield inclination angle computa-tional biomechanics model(CPCBM)

Geographic Variations in the Prevalence,Awareness,Treatment,and Control of Dyslipidemia among Chinese Adults in 2018–2019:A Cross-sectional Study

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Biomedical and Environmental Sciences 2023年第4期36卷 313-323页

作者： ZHANG Mei peng ke ZHANG Xiao LIU Yi Shu LIU Xiao Ying HAN Gui Yuan SHI Yu HUANG Zheng Jing LI Chun ZHAO Zhen Ping WANG Li Min LI Yi Chong National Center for Chronic and Non-communicable Disease Control and Prevention Chinese Center for Disease Control and PreventionBeijing 100050China National Clinical Research Center for Cardiovascular Diseases ShenzhenFuwai Hospital Chinese Academy of Medical SciencesShenzhen 518057GuangdongChina The George Institute for Global Health 2042New South WalesAustralia School of Medical Science Faculty of Medicine and HealthUniversity of Sydney2006New South WalesAustralia

Objective To investigate the spatial patterns of the prevalence,awareness,treatment,and control rates of dyslipidemia at the provincial level in China.Methods A national and provincial representative cross-sectional survey was conducted among 178,558 Chinese adults in 31 provinces in China's Mainland in 2018–2019,using a multi-stage,stratified,cluster-randomized sampling design.Subjects,as households,were selected,followed by a home visit to collect information.Both descriptive and linear regression procedures were applied in the analyses.Results The overall prevalence of dyslipidemia was 35.6%,and wide geographic variations of prevalence,treatment,and control rates of dyslipidemia were identified among 178,558 eligible participants with a mean age of 55.1±13.8 years.The highest-lowest difference regarding the provincial level prevalence rates were 19.7%vs.2.1%for high low-density lipoprotein cholesterol,16.7%vs.2.5%for high total cholesterol,35.9%vs.5.4%for high triglycerides,and 31.4%vs.10.5%for low high-density lipoprotein cholesterol.The treatment rate of dyslipidemia was correlated with the socio-demographic index(P<0.001),urbanization rate(P=0.01),and affordable basic technologies and essential medicines(P<0.001).Conclusion Prevailing dyslipidemia among the Chinese population and its wide geographic variations in prevalence,treatment,and control suggest that China needs both integrated and localized public health strategies across provinces to improve lipid management.

关键词： Lipids management Dyslipidemia Public health Chinese

三轴剪切过程中排水条件对钙质砂颗粒破碎、变形和强度特性的影响

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岩土力学 2024年第2期45卷 375-384页

作者：张季如陈敬鑫王磊彭伟珂武汉理工大学土木工程与建筑学院湖北武汉430070

钙质砂的颗粒破碎、变形和强度特性与受剪时的排水条件有关。然而当前的研究很少考虑不排水剪切过程对钙质砂颗粒破碎和力学特性的影响。对不同初始相对密实度的钙质砂进行了一系列不同有效围压下的三轴固结排水和不排水剪试验,以研究... 详细信息

钙质砂的颗粒破碎、变形和强度特性与受剪时的排水条件有关。然而当前的研究很少考虑不排水剪切过程对钙质砂颗粒破碎和力学特性的影响。对不同初始相对密实度的钙质砂进行了一系列不同有效围压下的三轴固结排水和不排水剪试验,以研究剪切过程中排水条件对钙质砂颗粒破碎和力学性质的影响。结果表明:在相同的有效围压下,排水剪试验的颗粒破碎率高于不排水剪试验。在排水剪与不排水剪过程中,钙质砂的应力-应变曲线都表现为应变软化行为,其剪胀趋势受到初始相对密实度和有效围压的影响。钙质砂的临界状态与初始状态无关,与剪切过程中的排水条件有关,对于临界应力比和相变应力比,排水剪试验大于不排水剪试验。钙质砂的峰值有效内摩擦角随初始相对密实度、有效围压和颗粒破碎率的增大而减小,但是临界有效内摩擦角不受初始条件、有效围压和颗粒破碎的影响,两种有效内摩擦角都与剪切过程中的排水条件有关。对于峰值有效内摩擦角和临界有效内摩擦角,排水剪试验大于不排水剪试验。上述结果表明,钙质砂的颗粒破碎、变形和强度特性与剪切过程中的排水条件具有明显的相关性。

关键词：钙质砂颗粒破碎排水条件变形抗剪强度

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阴道炎五联检在阴道炎检验中的应用

妇儿健康导刊 2024年第2期3卷 123-125页

作者：彭可湖北省麻城市人民医院检验科湖北麻城438300

目的探讨阴道炎五联检在阴道炎检验中的应用。方法选取2021年1月至2023年1月于麻城市人民医院检验科进行检查的100例疑似阴道炎患者,以阴道分泌物培养结果作为金标准,比较阴道炎五联检与显微镜检测法的诊断效能。结果阴道炎五联检阳性... 详细信息

目的探讨阴道炎五联检在阴道炎检验中的应用。方法选取2021年1月至2023年1月于麻城市人民医院检验科进行检查的100例疑似阴道炎患者,以阴道分泌物培养结果作为金标准,比较阴道炎五联检与显微镜检测法的诊断效能。结果阴道炎五联检阳性检出率高于显微镜检测法(P<0.05)。阴道炎五联检的敏感度、准确度、特异性均高于显微镜检测法(P<0.05)。结论阴道炎五联检在阴道炎检验中的诊断价值更高,值得临床推广应用。

关键词：阴道炎阴道炎五联检显微镜检测诊断效能

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Responsiveness of stroke volume variation and central venous pressure during acute normovolemic and hypervolemic hemodilution

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Chinese Medical Journal 2013年第10期126卷 1838-1843页

作者： JI Fu-hai LI Wen-jing LI Jiang peng ke YANG Jian-ping LIU Hong Department of Anesthesiology First Affiliated Hospital of SoochowUniversity Suzhou Jiangsu 215006 China Department of Anesthesiology and Pain Medicine University ofCaiifomia Davis Health System USA

Background Stroke volume variation （SW） is a robust indicator of fluid responsiveness during volume change. We compared the sensibility of SW by Vigileo/Flotrac to central venous pressure （CVP） when volume changes in patients undergoing intraoperative acute normovolemic hemodilution （ANH） and acute hypervolemic hemodilution （AHH）. Methods Forty patients were randomly divided into an ANH group （n=20） and an AHH group （n=20）. All patients received general anesthesia and were mechanically ventilated. Data were collected from 7 different time-points in the ANH group： baseline, after withdrawal of 5%, 10%, and 15% of the estimated blood volume （EBV） and after replacement with an equal volume of 6% hydroxyethyl starch 130/0.4 （HES） in 5% EBV increments to baseline. There were four time points in the AHH group： baseline, after 5%, 10%, and 15% expansion of the EBV with 6% HES. At each time-point, CVP, SW and other hemodynamic parameters measurements were obtained. Results After removal of 10% and 15% EBV, SVV significantly increased from 10.9±3.0 to 14.1±3.4 and 10.9±3.0 to16.0±3.3 （P 〈0.01）, and returned to a final value of 10.6±3.4 after volume replacement. The CVP value was unchanged after removal and replacement of 15% of the EBV. There were no significant changes in SW after 5%, 10% whereas there was a significant reduction after 15% （8.2±1.7） expansion of the EBV compared with baseline （9.9±1.8）（P=0.033）. However, there was a significant increase in CVP after10% （10.3±2.4）, 15% （11.3±2.2） expansion of the EBV compared with baseline （8.2±2.7）（P 〈0.01）. Conclusion SW is a more sensitive parameter for volume than CVP during hypovolemia, on the contrary CVP is more sensitive than SW during hypervolemia.

关键词： hemodilution stroke volume variation central venous pressure

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产业链韧性对经济高质量发展的影响

沈阳大学学报（社会科学版） 2024年第3期26卷 18-29页

作者：胡艳柯鹏安徽大学经济学院安徽合肥230039

基于2011—2022年长三角地区41个城市的面板数据,运用计量模型,分析研究了产业链韧性对经济高质量发展的影响效果及作用机制,并构建空间杜宾模型探索了产业链韧性对经济高质量发展的空间效应影响。结果表明:产业链韧性对经济高质量发展... 详细信息

基于2011—2022年长三角地区41个城市的面板数据,运用计量模型,分析研究了产业链韧性对经济高质量发展的影响效果及作用机制,并构建空间杜宾模型探索了产业链韧性对经济高质量发展的空间效应影响。结果表明:产业链韧性对经济高质量发展有显著正向作用;产业链韧性可以通过产业结构升级和产业创新两条路径来促进经济高质量发展;产业链韧性对于都市圈内城市和区位更具优势的城市的经济高质量发展的促进效果更明显;产业链韧性提升对周边城市经济高质量发展存在正向溢出效应。认为应从产业链延链补链强链、改善创新环境、做大产业集群等方面提升产业链韧性,推动产业转型升级和产业创新,促进经济高质量发展。

关键词：产业链产业链韧性高质量发展长三角空间效应

快速热压烧结制备高性能B_(4)C-LaB_(6)复合陶瓷

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粉末冶金材料科学与工程 2024年第1期29卷 35-44页

作者：徐志伟彭可袁铁锤中南大学轻质高强结构材料国家级重点实验室长沙410083

为了解决碳化硼(B_(4)C)难以烧结致密化和韧性差的问题,以B_(4)C和氧化镧(La_(2)O_(3))为原料,在2000℃和30 MPa下快速热压烧结制备B_(4)C-LaB_(6)复合陶瓷,研究La_(2)O_(3)含量对B_(4)C-LaB_(6)复合陶瓷微观结构和力学性能的影响,分析L... 详细信息

为了解决碳化硼(B_(4)C)难以烧结致密化和韧性差的问题,以B_(4)C和氧化镧(La_(2)O_(3))为原料,在2000℃和30 MPa下快速热压烧结制备B_(4)C-LaB_(6)复合陶瓷,研究La_(2)O_(3)含量对B_(4)C-LaB_(6)复合陶瓷微观结构和力学性能的影响,分析LaB_(6)的增韧机制。结果表明:w(La_(2)O_(3))=3%的B_(4)C-LaB_(6)复合陶瓷综合力学性能较好,其相对密度、维氏硬度、抗弯强度和断裂韧性分别为99.51%、36.56 GPa、547.43 MPa和4.18 MPa·m^(1/2)。LaB_(6)可细化B_(4)C-LaB_(6)复合陶瓷晶粒,同时提高其相对密度和断裂韧性。LaB_(6)的增韧机制与裂纹偏转和晶粒裂解有关。

关键词： B_(4)C-LaB_(6)复合陶瓷晶粒细化晶界相对密度增韧机制

Investigation of water impingement on a multi-element high-lift airfoil by Lagrangian and Eulerian approach

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Propulsion and Power Research 2015年第3期4卷 161-168页

作者： Chenxing Yu peng ke Guangfeng Yu Chunxin Yang School of Transportation Science and Engineering Beihang UniversityBeijing 100191China School of Aeronautics Science and Engineering Beihang UniversityBeijing 100191China

McDonnell Douglas Aerospace(MDA)high-lift model is widely used in the study of multi-element airfoil,while there is still short knowledge of ice accretion and water impingement on it.In this paper,based on two-phase flow theory,two numerical models were presented by using both Eulerian approach and Lagrangian approach,respectively,in order to predict the water impingement efficiency on a two-dimensional(2D)multi-element high-lift airfoil.Both computational results were validated with the experiment data,which shown good agreements in the impingement limitations and tendency.The trend that how the attack angle and droplet diameter affect the feather of local water impingement characteristics on the different elements of MDA were further investigated.As shown in this research,the trends that the local impingement intensity and extent on flap of MDA varied differently as in general understanding due to the complex structures of flow field,which should be careful cognized in design of the ice protection system.

关键词： Water impingement Multi-element high-lift airfoil Numeral simulation Lagrangian approach Eulerian approach