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Chinese Journal of Mechanical Engineering 2024年第2期37卷 100-114页

作者： yan Shi Jiange Kou Zhenlei Chen Yixuan Wang qing Guo School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China School of Aeronautics and Astronautics University of Electronic Science and Technology of ChinaChengdu 611731China

Exoskeletons generally require accurate dynamic models to design the model-based controller conveniently under the human-robot interaction ***,due to unknown model parameters such as the mass,moment of inertia and mechanical size,the dynamic model of exoskeletons is difficult to ***,an enhanced whale optimization algorithm(EWOA)is proposed to identify the exoskeleton model ***,the periodic excitation trajectories are designed by finite Fourier series to input the desired position demand of exoskeletons with mechanical physical *** a backstepping controller based on the identified model is adopted to improve the human-robot wearable comfortable performance under cooperative ***,the proposed Model parameters identification and control are verified by a two-DOF exoskeletons *** knee joint motion achieves a steady-state response after 0.5 ***,the position error of hip joint response is less than 0.03 rad after 0.9 *** addition,the steady-state human-robot interaction torque of the two joints is constrained within 15 N·*** research proposes a whale optimization algorithm to optimize the excitation trajectory and identify model ***,an enhanced mutation strategy is adopted to avoid whale evolution’s unsatisfactory local optimal value.

关键词： Parameter identification Enhanced whale optimization algorithm(EWOA) Backstepping Human-robot interaction Lower limb exoskeleton

Preparation and Structure-Property Regulation Mechanism of Reversible Thermochromic Polydiacetylene

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Chinese Journal of Polymer Science 2024年第8期42卷 1111-1121页

作者： Zhi-qing Ge Shuo yan Zu-Xiong Pan Shan Lei Xuan-Zhi Mao Chu Zhao Mo-Zhen Wang Xue-wu Ge Key Laboratory of Precision and Intelligent Chemistry Department of Polymer Science and EngineeringUniversity of Science and Technology of ChinaHefei 230026China Marshall Laboratory of Biomedical Engineering International Cancer CenterLaboratory of Evolutionary Theranostics(LET)School of Biomedical EngineeringShenzhen University Medical SchoolShenzhen UniversityShenzhen 518055China Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China University of Chinese Academy of Sciences Beijing 100049China

The thermochromic mechanism and the structure-property regulation principle of reversible thermochromic polydiacetylene(PDA)materials have always been a challenging *** this work,a series of diacetylene monomers(m-PCDA)containing phenyl and amide or carboxyl groups were synthesized from 10,12-pentacosadiynoic acid(PCDA)through the esterification or amidation *** effects of the number and the distribution of the functional groups in m-PCDA molecules on their solid-state polymerization capability,and the thermochromic mechanism of their corresponding polymers(m-PDA)were investigated and discussed in *** results show that the m-PCDA monomers containing both benzene ring and groups that can form hydrogen bonding interactions have strong intermolecular interaction,and are easy to carry out the solid phase polymerization under 254-nm UV irradiation to obtain the corresponding new thermochromic m-PDA *** thermochromic behavior of m-PDA depends on its melting *** initial color-change temperature(blue to red)is determined by the onset melting tem perature,and the temperature range in which reversible color recovery can be achieved by repeat heating-cooling treatment is determined by its melting *** to the proposed thermochromic mechanism of PDA,various new PDA materials with precise thermochromic temperatu res and reversible thermochromic temperature ra nges can be designed and synthesized through the appropriate introduction of benzene ring and groups that can form hydrogen bonding interactions into the molecular structure of linear diacetylene *** work provides a perspective to the precise molecular structure design and the property regulation of the reversible thermochromic PDA materials.

关键词： Polydiacetylene Thermochromism Hydrogen bonding Chemical modification

电子-离子碰撞对超热电子影响的PIC模拟计算

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物理学报 2000年第5期49卷 915-921页

作者：吴衍青韩申生中国科学院上海光学精密机械研究所上海201800

超热电子离子的产生和输运在传统的ICF方案和“快点火”方案中都是很重要的问题 .讨论了电子离子碰撞对参量不稳定性产生超热电子的过程和超热电子输运过程的影响 .指出电子离子弱碰撞项的加入增强了碰撞吸收 ,提高了热电子温度 ... 详细信息

超热电子离子的产生和输运在传统的ICF方案和“快点火”方案中都是很重要的问题 .讨论了电子离子碰撞对参量不稳定性产生超热电子的过程和超热电子输运过程的影响 .指出电子离子弱碰撞项的加入增强了碰撞吸收 ,提高了热电子温度 ,降低了静电波破裂时的场能 .这些改变了超热电子的总能量和分布 ,使之更集中于静电波的相速 ;电子离子碰撞的存在还增强了自洽电场 ,阻碍了超热电子的输运 ,同样也是超热电子能量下降的原因之一 .同时 ,为确保计算结果的可靠 ,讨论了初条件对PIC模拟计算的影响 ,指出空间位置随机热启动容易引入非物理因素。

关键词：电子-离了碰撞超热电子 PIC模拟计算

Cosmological interpretation for the stochastic signal in pulsar timing arrays

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Science China(Physics,Mechanics & Astronomy) 2024年第4期67卷 43-50页

作者： Yu-Mei wu Zu-Cheng Chen qing-Guo Huang School of Fundamental Physics and Mathematical Sciences Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of SciencesHangzhou 310024China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Department of Astronomy Beijing Normal UniversityBeijing 100875China Advanced Institute of Natural Sciences Beijing Normal UniversityZhuhai 519087China Department of Physics and Synergistic Innovation Center for Quantum Effects and Applications Hunan Normal UniversityChangsha 410081China CAS Key Laboratory of Theoretical Physics Institute of Theoretical PhysicsChinese Academy of SciencesBeijing 100190China

The pulsar timing array(PTA)collaborations have recently reported compelling evidence for a stochastic signal consistent with a gravitational-wave *** this paper,we combine the latest data sets from NANOGrav,PPTA,and EPTA to explore cosmological interpretations for the PTA signal from first-order phase transitions,domain walls,and cosmic strings,*** find that the domain wall model is strongly disfavored with the Bayes factors compared with the first-order phase transitions and cosmic strings being 1/90 and 1/189,respectively,breaking the degeneracy among these models in individual data *** also find that:(1)a strong phase transition at temperatures below the electroweak scale is favored,and the bubble collisions make the dominant contribution to the energy density spectrum;(2)a small reconnection probability p<1.55×10^(-1)allowed by strings in(super)string theory is favored at the 95%confidence level,and ground-based detectors can further constrain the parameter space.

关键词： puslar timing arrays gravitational-wave background first-order phase transitions domain walls cosmic strings

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黑河流域不同水体中δ^(18)O的变化

水科学进展 2007年第6期18卷 864-870页

作者：张应华仵彦卿清华大学环境科学与工程系北京100084 上海交通大学环境科学与工程学院上海200240

水资源短缺和合理利用是干旱半干旱区黑河流域面临的一个严峻问题,解决问题的关键是要深入了解水循环机理,而分析不同水体中环境同位素变化特征是应用同位素示踪技术研究水循环机理所必须的前提。根据测得的黑河流域降水、河水和地下水... 详细信息

水资源短缺和合理利用是干旱半干旱区黑河流域面临的一个严峻问题,解决问题的关键是要深入了解水循环机理,而分析不同水体中环境同位素变化特征是应用同位素示踪技术研究水循环机理所必须的前提。根据测得的黑河流域降水、河水和地下水中δ18O,分析了取样期间不同水样δ18O的变化,揭示了降水中δ18O存在显著的温度效应、季节效应、高程效应以及与降水量的正相关关系;河水中δ18O的时空变化特征,即出山口地区河水中δ18O统计值低于山区和盆地,山区河水中δ18O的时间分布与大气降水一致,出山口河水中δ18O时间分布与大气降水相反,河水中δ18O沿黑河流程存在显著递增趋势;地下水中δ18O在张掖变化幅度较大,在临泽较均一且9月份普遍高于6月份,而在高台则分为显著的2组,较高的一组9月份普遍低于6月份。研究了不同因素对水循环过程中δ18O变化的影响及相互作用,为同位素技术在黑河流域水循环研究中的应用提供科学依据。

关键词：黑河水循环 δ^18O 同位素

Enhanced detection of freeze‒thaw induced landslides in Zhidoi county(Tibetan Plateau,China)with Google Earth Engine and image fusion

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Advances in Climate Change Research 2024年第3期15卷 476-489页

作者： Jia-Hui yanG yan-Chen GAO Lang JIA Wen-Juan WANG qing-Bai wu Francis ZVOMUYA Miles DYCK Hai-Long HE College of Natural Resources and Environment Northwest A&F UniversityYangling 712100China State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China Department of Soil Science University of Manitob1Winnipeg MB R3T 2N2Canada Department of Renewable Resources University of Albert1Edmonton AB T6G 2H1Canad

Freeze‒thaw induced landslides(FTILs)in grasslands on the Tibetan Plateau are a geological disaster leading to soil *** landslides reduce biodiversity and intensify landscape fragmentation,which in turn are strengthen by the persistent climate change and increased anthropogenic ***,conventional techniques for mapping FTILs on a regional scale are impractical due to their labor-intensive,costly,and time-consuming *** study focuses on improving FTILs detection by implementing image fusion-based Google Earth Engine(GEE)and a random forest *** of multiple data sources,including texture features,index features,spectral features,slope,and vertical‒vertical polarization data,allow automatic detection of the spatial distribution characteristics of FTILs in Zhidoi county,which is located within the qinghai‒Tibet Engineering Corridor(QTEC).We employed statistical techniques to elucidate the mechanisms influencing FTILs *** enhanced method identifies two schemes that achieve high accuracy using a smaller training sample(scheme A:94.1%;scheme D:94.5%)compared to other methods(scheme B:50.0%;scheme C:95.8%).This methodology is effective in generating accurate results using only~10%of the training sample size necessitated by other *** spatial distribution patterns of FTILs generated for 2021 are similar to those obtained using various other training sample sources,with a primary concentration observed along the central region traversed by the *** results highlight the slope as the most crucial feature in the fusion images,accounting for 93%of FTILs occurring on gentle slopes ranging from 0°to 14°.This study provides a theoretical framework and technological reference for the identification,monitoring,prevention and control of FTILs in *** developments hold the potential to benefit the management of grassland ecosystem,reduce economic losses,and promote grassland sustainability.

关键词： Permafrost degradation Random forest Thaw slump Spatial distribution Tibetan Plateau

Association between the cumulative triglyceride-glucose index and the recurrence of atrial fibrillation after radiofrequency catheter ablation

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Journal of Geriatric Cardiology 2024年第2期21卷 200-210页

作者： qing yan Jia-Qi LIANG Yi-De YUAN Yuan LI Jia-Li FAN Wen-Huan wu Pan XU Jia-Hong XUE Department of Cardiovascular Medicine the Second Affiliated Hospital of Xi’an Jiaotong UniversityShaanxiChina Department of Cardiovascular Medicine Zichang People’s HospitalShaanxiChina Department of Ultrasound Xijing HospitalAir Force Military Medical UniversityShaanxiChina

BACKGROUND Triglyceride-glucose(TyG)index values are a new surrogate marker for insulin *** study aimed to explore the relationship between cumulative TyG index values and atrial fibrillation(AF)recurrence after radiofrequency catheter ablation(RFCA).METHODS A total of 576 patients with AF who underwent RFCA at the Second Affiliated Hospital of Xi'an Jiaotong University were included in this *** participants were grouped based on cumulative TyG index values tertiles within 3 months after *** regression and restricted cubic spline analyses were used to determine the relationship between cumulative TyG index values and AF *** predictive value of all risk factors was assessed by receiver operating curve *** There were 375 patients completed the study(age:63.23±10.73 years,64.27%male).The risk of AF recurrence increased with increasing cumulative TyG index values *** adjusting for potential confounders,patients in the medium cumulative TyG index group[hazard ratio(HR)=4.949,95%CI:1.778–13.778,P=0.002]and the high cumulative TyG index group(HR=8.716,95%CI:3.371–22.536,P<0.001)had a higher risk of AF recurrence than those in the low cumulative TyG index *** restricted cubic spline regression model also showed an increased risk of AF recurrence with increasing cumulative TyG index *** considering cumulative TyG index values,left atrial diameter,and lactate dehydrogenase levels as a comprehensive factor,the model could effectively predict AF recurrence after RFCA[area under the curve(AUC)=0.847,95%CI:0.797–0.897,P<0.001].CONCLUSIONS Cumulative TyG index values were a risk factor for AF recurrence after *** longitudinal TyG index values may assist with optimized for risk stratification and outcome prediction for AF recurrence.

关键词： atrial fibrillation index

Global-local combined features to detect pain intensity from facial expression images with attention mechanism

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Journal of Electronic Science and Technology 2024年第3期22卷 80-93页

作者： Jiang wu Yi Shi Shun yan Hong-Mei yan yangtze Delta Region Institute(Huzhou) University of Electronic Science and Technology of ChinaHuzhou313001China MOE Key Laboratory for Neuroinformation School of Life Science and TechnologyUniversity of Electronic Science and Technology of ChinaChengdu611731China College of Engineering University of California at Santa BarbaraSanta Barbara93106USA

The estimation of pain intensity is critical for medical diagnosis and treatment of *** the development of image monitoring technology and artificial intelligence,automatic pain assessment based on facial expression and behavioral analysis shows a potential value in clinical *** paper reports a framework of convolutional neural network with global and local attention mechanism(GLA-CNN)for the effective detection of pain intensity at four-level thresholds using facial expression ***-CNN includes two modules,namely global attention network(GANet)and local attention network(LANet).LANet is responsible for extracting representative local patch features of faces,while GANet extracts whole facial features to compensate for the ignored correlative features between *** the end,the global correlational and local subtle features are fused for the final estimation of pain *** under the UNBC-McMaster Shoulder Pain database demonstrate that GLA-CNN outperforms other state-of-the-art ***,a visualization analysis is conducted to present the feature map of GLA-CNN,intuitively showing that it can extract not only local pain features but also global correlative facial *** study demonstrates that pain assessment based on facial expression is a non-invasive and feasible method,and can be employed as an auxiliary pain assessment tool in clinical practice.

关键词： Attention Convolutional neural network Facial expression Pain intensity

Influence of friction-lubrication characteristics varying with rolling speed on instability of chatter and slip in cold tandem rolling process

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Journal of Iron and Steel Research International 2024年第4期31卷 894-908页

作者： yan-li Xin Zhi-ying Gao Bo Tian qing-dong Zhang School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China

In the high-speed cold tandem rolling process of thin plate,chatter or slip instability gives rise to the deterioration of equipment and product *** instability behavior is closely related to interfacial friction-lubrication con-dition which is generally characterized by the friction ***,with higher and higher speed requirements,the commonly used model of friction coefficient is no longer applicable and accurate.A novel approach is suggested to calculate the speed-dependent friction coefficient,in which the viscosity-pressure-temperature effects of the lubricant,surface roughness states of work rolls and rolled piece are comprehensively involved and the mixed flm lubrication theory is ***,the influences of friction coefficient on the instability of slip and chatter are investigated for a five-stand cold tandem rolling *** one side,the critical friction coefficient for each stand is determined by calculating the corresponding slip factor;on the other hand,the friction coefficient varying with rolling speed is combined with the model of theoretical critical rolling speed presented under constant friction coefficient,so that the speed threshold is ***,the stable and unstable regions corresponding to the rear three stands are individually discussed,and the technical strategies are proposed to suppress both slip and chatter frequently occurring in the actual rolling process.

关键词： Cold tandem rolling:Oil film thickness Speed-dependent friction coefficient-Slip:Chatter

Vacuum chamber suppression of gas-explosion propagation in a tunnel

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Journal of China University of Mining and Technology 2008年第3期18卷 337-341页

作者： JIANG Shu-guang wu Zheng-yan LI qing-hua HE Xin-jian SHAO Hao QIN Jun-hui WANG Lan-yun HU Li-ming LIN Bai-quan School of Safety Engineering China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

To control and reduce the harm of a gas explosion, a new method is proposed for suppressing gas-explosion propagation in a tunnel by using a vacuum chamber. We studied the suppression effect on gas explosions by placing a vacuum chamber at dif-ferent positions along the tunnel. The results indicate that: 1) the vacuum chamber can absorb the explosion wave and explosion energy as much as possible at the beginning of the gas explosion, and; 2) when the vacuum chamber is used the closer it is to the ignition source the more significant the suppression effect. In addition, by using the vacuum chamber: 1) the flame propagation velocity decreases from ultrasonic to subsonic; 2) the flame propagation distance is remarkably shortened; 3) the maximum peak value of overpressure (pm) decreases from 0.34 to 0.17 MPa or less, and; 4) the impulse of the blast wave (I) decreases from 20 to 8 kPa·s or less.

关键词： vacuum chamber liquid venting flame quenching pressure venting impulse explosion suppression