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Prediction of contact resistance of electrical contact wear using different machine learning algorithms

Friction 2024年第6期12卷 1250-1271页

作者： Zhen-bing CAI Chun-lin li Lei YOU Xu-dong CheN li-ping he Zhong-qing CAO Zhi-nan ZHANG Tribology Research Institute Southwest Jiaotong UniversityChengdu 610031China State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China

H62 brass material is one of the important materials in the process of electrical energy transmission and signal transmission,and has excellent performance in all aspects.Since the wear behavior of electrical contact pairs is particularly complex when they are in service,we evaluated the effects of load,sliding velocity,displacement amplitude,current intensity,and surface roughness on the changes in contact resistance.Machine learning(ML)algorithms were used to predict the electrical contact performance of different factors after wear to determine the correlation between different factors and contact resistance.Random forest(RF),support vector regression(SVR)and BP neural network(BPNN)algorithms were used to establish RF,SVR and BPNN models,respectively,and the experimental data were trained and tested.It was proved that BP neural network model could better predict the stable mean resistance of H62 brass alloy after wear.Characteristic analysis shows that the load and current have great influence on the predicted electrical contact properties.The wear behavior of electrical contacts is influenced by factors such as load,sliding speed,displacement amplitude,current intensity,and surface roughness during operation.Machine learning algorithms can predict the electrical contact performance after wear caused by these factors.Experimental results indicate that an increase in load,current,and surface roughness leads to a decrease in stable mean resistance,while an increase in displacement amplitude and frequency results in an increase in stable mean resistance,leading to a decline in electrical contact performance.To reduce testing time and costs and quickly obtain the electrical contact performance of H62 brass alloy after wear caused by different factors,three algorithms(random forest(RF),support vector regression(SVR),and BP neural network(BPNN))were used to train and test experimental results,resulting in a machine learning model suitable for predicting the stable mean resistance of H62 brass alloy after wear.The pr

关键词： electrical contact wear contact resistance machine learning(ML) neural network

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Predicting the electromechanical properties of small caliber projectile impact igniter using PZT dynamic damage constitutive model considering crack propagation

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Defence Technology（防务技术） 2023年第10期28卷 121-135页

作者： Rui-zhi Wang Zhi-qiang Wang En-ling Tang Lei li Guo-lai Yang Chun Cheng li-ping he Ya-fei Han Key Laboratory of Transient Physical Mechanics and Energy Conversion Materials of liaoning Province Shenyang Ligong UniversityShenyang110159LiaoningChina School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing210094JiangsuChina Key Laboratory of Impact and Safety Engineering Ministry of EducationNingbo UniversityNingbo315211ZhejiangChina

Block piezoelectric ceramics(PZTs)are often used in impact igniters to provide activation energy for electric initiators.Under the action of strong impact stress,PZTs release electric energy accompanied by crack initiation,propagation and crushing.At present,the electrical output performance of PZTs in projectile is usually calculated by quasi-static piezoelectric equation without considering the dynamic effect caused by strong impact and the influence of crack propagation on material properties.So the ignition parameters are always not accurately predicted.To tackle this,a PZT dynamic damage constitutive model considering crack propagation is established based on the dynamic impact test and the crack propagation theory of brittle materials.The model is then embedded into the ABAQUS subroutine and used to simulate the electromechanical response of the impact igniter during the impact of a small caliber projectile on the target.Meanwhile,the experiments of projectile with impact igniter impact on the target are carried out.The comparison between experimental and numerical simulation results show that the established dynamic damage model can effectively predict the dynamic electromechanical response of PZTs in the missile service environment.

关键词： Piezoelectric ceramics Impact Igniter Dynamic damage constitutive model Electromechanical response

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Foreground removal of 21cm fluctuation with multifrequency fitting

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Research in Astronomy and Astrophysics 2009年第6期9卷 653-664页

作者： li-ping he National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

The 21 centimeter （21 cm） line emission from neutral hydrogen in the intergalactic medium （IGM） at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200 MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 - 200 MHz. However, this method doesn＇t work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of ≈ 10 mK at 150 MHz with 40 antennas in 120 hours of observations.

关键词： cosmology theory, observations, diffuse radiation -- methods data analysis

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Modeling the WMAP large-angle anomalies as an effect of a local density inhomogeneity

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Research in Astronomy and Astrophysics 2010年第2期10卷 116-124页

作者： li-ping he Quan Guo National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China Graduate University of Chinese Academy of Sciences Beijing 100049 China

We investigate large-angle scale temperature anisotropy in the Cosmic Microwave Background （CMB） with the Wilkinson Microwave Anisotropy Probe （WMAP） data and model the large-angle anomalies as the effect of the CMB quadrupole anisotropies caused by the local density inhomogeneities. The quadrupole caused by the local density inhomogeneities is different from the special relativity kinematic quadrupole. If the observer inhabits a strong inhomogeneous region, the lo- cal quadrupole should not be neglected. We calculate such local quadrupole under the assumption that there is a huge density fluctuation field in the direction （284°, 74°）, where the density fluctuation is 10-3, and its center is - 112 h-1 Mpc away from us. After removing such mock signals from WMAP data, the power in the quadrupole, C2, increases from the range （200 - 260 μK2） to - 1000 μK2. The quantity S, which is used to estimate the alignment between the quadrupole and the octopole, decreases from （0.7 - 0.74） to （0.31 - 0.37）, while the model predicts that C2 = 1071.5 μK2, and S = 0.412. So our local density inhomogeneity model can, in part, explain the WMAP low-l anomalies.

关键词： cosmology： cosmic microwave background -- cosmology： large-scale structure of universe

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Parareal in Time Simulation of Morphological Transformation in Cubic Alloys with Spatially Dependent Composition

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Communications in Computational Physics 2012年第5期11卷 1697-1717页

作者： li-ping he Minxin he Department of Mathematics Shanghai Jiaotong UniversityShanghai 200240China

In this paper,a reducedmorphological transformation model with spatially dependent composition and elastic modulus is considered.The parareal in time algorithm introduced by lions et al.is developed for longer-time simulation.The fine solver is based on a second-order scheme in reciprocal space,and the coarse solver is based on a multi-model backward Euler scheme,which is fast and less expensive.Numerical simulations concerning the composition with a randomnoise and a discontinuous curve are performed.Some microstructure characteristics at very low temperature are obtained by a variable temperature technique.

关键词： Morphological transformation multi-model scheme parareal in time simulation

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Effect of temperature maintenance by forced-air warming blankets of different temperatures on changes in inflammatory factors in children undergoing congenital hip dislocation surgery

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Chinese Medical Journal 2020年第15期133卷 1768-1773页

作者： li-ping he Pei-Zhen liu Yuan-Ming Wen Jun Wu Department of Operation Room Guangzhou Women and Children's Medical CenterGuangzhou Medical UniversityGuangzhouGuangdong 510623China

Background:Hypothermia is associated with many adverse clinical outcomes in pediatric patients,and thus,it is important to an effective and safe method for preventing peri-operative hypothermia and its associated adverse outcomes in pediatric patients.This study aimed to investigate the effect of forced-air warming blankets with different temperatures on changes in the transforming growth factor-β(TGF-β),tumor necrosis factor(TNF)-α,interleukin(IL)-1β,and IL-10 levels in children undergoing surgical treatment for developmental displacement of the hip(DDH).Methods:The study included 123 children undergoing surgery for DDH under general anesthesia.The patients were randomly assigned to three groups,using a random number table:the 32,38,and 43°C groups according to the temperature setting of the forced-air warming blankets.For each patient,body temperature was recorded immediately after anesthesia induction and intubation(T0),at initial incision(T1),at 1 h after incision(T2),at2 h after incision(T3),at the end of surgery(T4),immediately upon return to the ward after surgery(T5),and then at 12 h(T6),24 h(T7),36 h(T8),and 48 h(T9)after the surgery.The serum levels of TGF-β,TNF-α,IL-1β,and IL-10 were measured at To and T4 for all groups.Results:The number of patients with fever in the 38°C group was significantly less than those in the 32 and 43°C groups(x^2=6.630,P=0.036).At To,the body temperatures in the 38 and 43°C groups were significantly higher than that in the 32°C group(F=17.992,Phe body temperature was significantly higher in the 43°C group than those in the 32 and 38°C groups(F=12.776,Phe serum levels of TGF-β(F=3286.548,Phe 38°C group,and the serum levels of TNF-α(F=911.415,Phe 38°C group,compared with the levels in the 32 and 43°C groups.Conclusion:Force-air warming blankets set at 38°C maintained stable body temperature with less ad

关键词： Body temperature Developmental displacement of the hip Inflammatory factor Rehabilitation Transforming growth factor-beta

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Same-day single-dose vs large-volume split-dose regimens of polyethylene glycol for bowel preparation:A systematic review and meta-analysis

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World Journal of Clinical Cases 2022年第22期10卷 7844-7858页

作者： Hui Pan Xiao-ling Zheng Chao-Ying Fang Lan-Zai liu Jian-Su Chen Chao Wang Yu-Dai Chen Jian-Min Huang Yu-Shen Zhou li-ping he Gastrointestinal Endoscopy Center Fujian Provincial HospitalThe Shengli Clinical Medical CollegeFujian Medical UniversityFuzhou 350001Fujian ProvinceChina Gastrointestinal Endoscopy Center Fujian Provincial Hospital South BranchFuzhou 350001Fujian ProvinceChina

BACKGROUND Split-dose regimens(SpDs)of 4 L of polyethylene glycol(PEG)have been established as the“gold standard”for bowel preparation;however,its use is limited by the large volumes of fluids required and sleep disturbance associated with night doses.Meanwhile,the same-day single-dose regimens(SSDs)of PEG has been recommended as an alternative;however,its superiority compared to other regimens is a matter of debate.AIM To compare the efficacy and tolerability between SSDs and large-volume SpDs PEG for bowel preparation.METHODS We searched MEDliNE/PubMed,the Cochrane library,RCA,EMBASE and Science Citation Index Expanded for randomized trials comparing(2 L/4 L)SSDs to large-volume(4 L/3 L)SpDs PEG-based regimens,regardless of adjuvant laxative use.The pooled analysis of relative risk ratio and mean difference was calculated for bowel cleanliness,sleep disturbance,willingness to repeat the procedure using the same preparation and adverse effects.A random effects model or fixed-effects model was chosen based on heterogeneity analysis among studies.RESULTS A total of 18 studies were included.There was no statistically significant difference of adequate bowel preparation(relative risk=0.97;95%CI:0.92-1.02)(14 trials),right colon Boston Bowel Preparation Scale(mean difference=0.00;95%CI:-0.04,0.03)(9 trials)and right colon Ottawa Bowel Preparation Scale(mean difference=0.04;95%CI:-0.27,0.34)(5 trials)between(2 L/4 L)SSDs and large-volume(4 L/3 L)SpDs,regardless of adjuvant laxative use.The pooled analysis favored the use of SSDs with less sleep disturbance(relative risk=0.52;95%CI:0.40,0.68)and lower incidence of abdominal pain(relative risk=0.75;95%CI:0.62,0.90).During subgroup analysis,patients that received low-volume(2 L)SSDs showed more willingness to repeat the procedure using the same preparation than SpDs(Phe two arms(P>0.05).CONCLUSION Regardless of adjuvant laxative use,the(2 L/4 L)SSD PEG-based arm

关键词： Bowel preparation Colonoscopy Polyethylene glycol Same-day single-dose Split-dose Metaanalysis

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地球内核各向异性结构成因:矿物学模型和动力学机制

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矿物岩石地球化学通报 2024年第2期43卷 282-291,I0002页

作者：何宇孙士川徐云帆李和平中国科学院地球化学研究所中国科学院地球内部物质高温高压重点实验室贵阳550081

地震学观测表明,地球内核具有复杂的不均一性和各向异性结构,认知内核结构的关键在于研究内核各向异性结构的矿物学组成和动力学机制。本文将介绍内核各向异性结构特征,并探讨其矿物模型和动力学机制。在内核温压下,六方相(hcp)和体心立... 详细信息

地震学观测表明,地球内核具有复杂的不均一性和各向异性结构,认知内核结构的关键在于研究内核各向异性结构的矿物学组成和动力学机制。本文将介绍内核各向异性结构特征,并探讨其矿物模型和动力学机制。在内核温压下,六方相(hcp)和体心立方(bcc)相铁合金都表现出各向异性,若其快轴沿自转轴产生定向排布,则可以解释内核南北方向快、赤道方向慢的各向异性特征。轻元素的加入将显著改变铁合金的各向异性,特别是超离子态铁-氢合金的快轴方向随氢含量的增加而发生倒转。内核各向异性的动力学机制可分为3种:(1)凝固时晶体的定向生长。凝固时的组构在内核温度下会很快消失,因此该机制不是导致内核各向异性结构的主要原因;(2)外应力驱动。外应力驱动的定向排列需要考虑内核物质的流变机制,目前的模型主要基于刚性内核假设,要求内核主要发生位错蠕变且黏度大于1018Pa·s;(3)扩散内应力驱动。若内核处于超离子态,地磁场驱动轻元素定向扩散所产生的内应力可驱动晶格的定向排布。上述机制的驱动力(化学对流、热对流、地磁场)均来自外核,因此了解外核动力学与内核动力学的相互作用是认知内核组成和结构的关键。

关键词：地球内核各向异性高温高压铁合金定向排布

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战骨叶甲醇部位化学成分及其抗炎活性研究

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中成药 2024年第6期46卷 1894-1899页

作者：贺非凡赵宁涛颜小捷卢凤来蒋小华李和平李典鹏陈月圆广西壮族自治区中国科学院广西植物研究所广西植物功能物质与资源持续利用重点实验室广西桂林541006 桂林理工大学广西桂林541006

目的研究战骨叶甲醇部位的化学成分及其抗炎活性。方法战骨叶甲醇部位采用薄层色谱、柱色谱和HSCCC进行分离纯化,根据理化性质及波谱数据鉴定所得化合物的结构。采用RAW264.7模型评价其体外抗炎活性。结果从中分离得到12个化合物,分别... 详细信息

目的研究战骨叶甲醇部位的化学成分及其抗炎活性。方法战骨叶甲醇部位采用薄层色谱、柱色谱和HSCCC进行分离纯化,根据理化性质及波谱数据鉴定所得化合物的结构。采用RAW264.7模型评价其体外抗炎活性。结果从中分离得到12个化合物,分别为鉴定为牡荆素(1)、balanophonin(2)、桦褐孔菌二糖(3)、4-allyl-2,6-dimethoxyphenol-β-D-glucopyranoside(4)、去氢催吐萝芙木醇(5)、地芰普内酯(6)、(E)-4-((1S,3R,4R)-1-hydroxy-4,5,5-trimethyl-7-oxabicyclo[4.1.0]heptan-1-yl)but-1-en-3-o-ne(7)、(E)-4-hydroxyphenylprop-7-ene 4-O-β-D-glucopyranoside(8)、4-羟基苯甲酸4-O-β-D-吡喃葡萄糖苷(9)、vicenin(10)、齐墩果酸(11)、芝麻素(12)。化合物1、2、5、7、10、12对NO均具有良好的抑制活性,IC 50值分别为(26.42±2.5)、(21.24±2.2)、(25.88±1.9)、(29.72±2.1)、(8.90±1.1)、(9.73±0.7)μmol/L。结论化合物2、4~8为首次从豆腐柴属植物中分离得到。化合物1、2、5、7、10、12具有抗炎活性。

关键词：战骨叶甲醇部位化学成分分离鉴定抗炎活性

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Searching for initial stage of massive star formation around the HⅡ region G18.2–0.3

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Research in Astronomy and Astrophysics 2017年第6期17卷 77-88页

作者： Chuan-Peng Zhang Jing-Hua Yuan Jin-Long Xu Xiao-Lan liu Nai-ping Yu Nan li li-ping he Guo-Yin Zhang Jun-Jie Wang National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China

Sometimes, early star formation can be found in cold and dense molecular clouds, such as an infrared dark cloud. Considering that star formation often occurs in clusters, H II regions may be triggering a new generation of star formation, so we can search for the initial stage of massive star formation around H II regions. Based on the above, this work introduces one method to search for the initial stage of massive star formation around H II regions. Towards one section of the H II region G18.2-0.3, multiwavelength observations are carried out to investigate its physical properties. Through analysis, we find three potential initial stages of massive star formation, suggesting that it is feasible to use in searching for the initial stage of massive star formation around H II regions.

关键词： infrared stars - stars formation - initial stage - H II regions

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