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Field-assisted thermionic emission toward quantitative modeling of charge-transfer mechanisms in contact electrification

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SmartMat 2022年第4期3卷 619-631页

作者： Xin XIA Haoyu Wang Yunlong Zi Department of Mechanical and Automation Engineering The Chinese University of Hong KongHong KongShatinN.T.China

Charge transfer mechanisms of contact electrification(CE)are essential for widening applications of the triboelectric nanogenerator,and thus are widely studied by scientists around the world.However,the quantitative modeling of CE,especially that between polymers,is still lacking.Herein,a model was proposed to describe the contributions from different mechanisms,including electron transfer and mass transfer in polymer/polymer CE through the fieldassisted thermionic emission,where three groups of charge transfer mechanisms were distinguished by the polarity of the charge transfer and the corresponding electric field.The results indicated that the total generated charge in CE is actually much larger than the measured net surface charge,confirming the bidirectional material-dependent charge transfer mechanisms between two surfaces,which is meaningful for understanding the millennium puzzle in triboelectrification and provides a new perspective for promoting the applications to tailor surface charge generation.

关键词： charge-transfer mechanism contact electrification field-assisted thermionic emission quantitative modeling triboelectric effect

A manual inspection of Defects4J bugs and its implications for automatic program repair

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Science China(Information Sciences) 2019年第10期62卷 31-46页

作者： Jiajun JIANG Yingfei XIONG Xin XIA Key Laboratory of High Confidence Software Technologies Ministry of EducationInstitute of Software Department of Computer Science and Technology Peking University The Faculty of Information Technology Monash University

Automatic program repair techniques, which target to generate correct patches for real-world defects automatically, have gained a lot of attention in the last decade. Many different techniques and tools have been proposed and developed. However, even the most sophisticated automatic program repair techniques can only repair a small portion of defects while producing a large number of incorrect patches.A possible reason for the low performance is the test suites of real-world programs are usually too weak to guarantee the behavior of a program. To understand to what extent defects can be fixed with exiting test suites, we manually analyzed 50 real-world defects from Defects4J, where a large portion(i.e., 82%) of them were correctly fixed. This result suggests that there is much room for the current automatic program repair techniques to improve. Furthermore, we summarized seven fault localization and seven patch generation strategies that are useful in localizing and fixing these defects, and compared those strategies with current techniques. The results indicate potential directions to improve automatic program repair in the future.

关键词： automatic defect repair fault localization manual repair software maintenance case study

How does working from home affect developer productivity?——A case study of Baidu during the COVID-19 pandemic

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Science China(Information Sciences) 2022年第4期65卷 141-155页

作者： Lingfeng BAO Tao LI Xin XIA Kaiyu ZHU Hui LI xiaohu YANG College of Computer Science and Technology Zhejiang University Baidu Inc. Faculty of Information Technology Monash University

Nowadays, working from home(WFH) has become a popular work arrangement due to its many potential benefits for both companies and employees(e.g., increasing job satisfaction and retention of employees). Many previous studies have investigated the impact of WFH on the productivity of employees.However, most of these studies usually use a qualitative analysis method such as surveys and interviews,and the studied participants do not work from home for a long continuing time. Due to the outbreak of coronavirus disease 2019(COVID-19), a large number of companies asked their employees to work from home, which provides us an opportunity to investigate whether WFH affects their productivity. In this study, to investigate the difference in developer productivity between WFH and working onsite, we conduct a quantitative analysis based on a dataset of developers’ daily activities from Baidu Inc., one of the largest IT companies in China. In total, we collected approximately four thousand records of 139 developers’ activities of 138 working days. Out of these records, 1103 records are submitted when developers work from home due to the COVID-19 pandemic. We find that WFH has both positive and negative impacts on developer productivity in terms of different metrics, e.g., the number of builds/commits/code reviews. We also notice that WFH has different impacts on projects with different characteristics including programming language,project type/age/size. For example, WFH has a negative impact on developer productivity for large projects.Additionally, we find that productivity varies for different developers. Based on these findings, we get some feedback from developers of Baidu and understand some reasons why WFH has different impacts on developer productivity. We also conclude several implications for both companies and developers.

关键词： WFH developer productivity Developer Productivity

Conductivity and tribological properties of IL-PANI/WS_(2) composite material in lithium complex grease

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Friction 2023年第6期11卷 977-991页

作者： Yanqiu xia Yuanhui WANG Chenglong HU xin FENG School of Energy Power and Mechanical Engineering North China Electric Power UniversityBeijing102206China

An ionic liquid-polyaniline/tungsten disulfide(IL-PANI/WS_(2))composite was synthesized in 1-butyl-3-methylimidazole tetrafluoroborate(LB104)aqueous solution by in-situ polymerization and characterized by Fourier transform infrared spectroscopy.A current-carrying friction and wear tester was used to study the tribological properties of steel-steel and copper-copper friction pairs lubricated by an IL-PANI/WS_(2) lithium complex grease(LCG).After the experiment,scanning electron microscope was used to observe the surface morphology of the wear scar on the steel and copper plates,and X-ray photoelectron spectrometer was used to analyze the elemental composition of the wear scar surface.The results show that compared with greases containing IL-PANI and WS_(2),greases containing IL-PANI/WS_(2) exhibit better antiwear performance when lubricating steel-steel friction pairs and better tribological performance and electrical conductivity when lubricating copper-copper friction pairs.Therefore,it can be concluded that WS_(2) and IL-PANI have a synergistic effect.

关键词： lithium complex grease(LCG) current-carrying friction additive ionic liquid-polyaniline/tungsten disulfide(IL-PANI/WS_(2))

Classification and spectrum optimization method of grease based on infrared spectrum

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Friction 2024年第6期12卷 1154-1164页

作者： xin FENG Yanqiu xia Peiyuan XIE xiaohe LI School of Energy Power and Mechanical Engineering North China Electric Power UniversityBeijing 102206China State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical PhysicsChinese Academy of SciencesLanzhou 730000China

The infrared(IR)absorption spectral data of 63 kinds of lubricating greases containing six different types of thickeners were obtained using the IR spectroscopy.The Kohonen neural network algorithm was used to identify the type of the lubricating grease.The results show that this machine learning method can effectively eliminate the interference fringes in the IR spectrum,and complete the feature selection and dimensionality reduction of the high-dimensional spectral data.The 63 kinds of greases exhibit spatial clustering under certain IR spectrum recognition spectral bands,which are linked to characteristic peaks of lubricating greases and improve the recognition accuracy of these greases.The model achieved recognition accuracy of 100.00%,96.08%,94.87%,100.00%,and 87.50%for polyurea grease,calcium sulfonate composite grease,aluminum(Al)-based grease,bentonite grease,and lithium-based grease,respectively.Based on the different IR absorption spectrum bands produced by each kind of lubricating grease,the three-dimensional spatial distribution map of the lubricating grease drawn also verifies the accuracy of classification while recognizing the accuracy.This paper demonstrates fast recognition speed and high accuracy,proving that the Kohonen neural network algorithm has an efficient recognition ability for identifying the types of the lubricating grease.

关键词： grease infrared(IR)spectroscopy layered Kohonen network species recognition spectrum band optimization

A novel classification of tracheal defects and the reconstruction strategies:A retrospective study based on 106 cases

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World Journal of Otorhinolaryngology-Head and Neck Surgery 2023年第1期9卷 66-73页

作者： Xin XIA Zhu xiao-Li Ying-Ying Zhu Wen-Wen Diao xing-Ming Chen Department of Otolaryngology-Head and Neck Surgery Peking Union Medical College HospitalPeking Union Medical College and Chinese Academy of Medical SciencesBeijing100730China

Objective:The study aims to present a novel classification of tracheal defects and the corresponding reconstruction strategies.Methods:The retrospective study was designed to analyze patients with diagnosed primary or secondary tracheal tumors from 1991 to 2020.Surgical techniques,complications and prognosis were reviewed.Airway status and patient outcomes were the principal follow-up measures.Tracheal defects were classified into two plane sizes(vertical(V)and horizontal(H)planes).Vertical defects were further categorized into three groups based on their tracheal ring numbers(V 1,≤5 rings;V 2,6-10 rings;and V 3,>10 rings).Tracheal defects with horizontal plane size H 1 and H 2 represent defects less and more than one-half the circumference of trachea.Thus,suitable reconstruction strategies were planned primarily based on"V"and"H"classifications.The reconstruction strategies performed were sleeve resection followed by an end-to-end anastomosis,window resection with sternocleidomastoid myoperiosteal flap reconstruction,defects conversion with rotation anastomosis,and modified tracheostomy with secondary flap reconstruction.Results:A total of 106 patients diagnosed with tracheal defects were enrolled in the study,of whom 59 patients underwent sleeve resection followed by end-to-end anastomosis;40 patients received window resection alongside sternocleidomastoid(SCM)myoperiosteal flap reconstruction;five patients received converting defects with rotation anastomosis and two patients underwent modified tracheostomy with secondary stage flap reconstruction.Lumen stenosis occurred in three V 2H 1 defect cases and were treated by a second reconstruction surgery.Iatrogenic unilateral recurrent laryngeal nerve paralysis occurred in two patients with the V 3H 2 defect type,who were treated by temporary tracheotomy and partial vocal cord resection and extubated successfully during follow-up.All 106 patients achieved airway patency with adequate laryngeal function at the end of follow-up.No anastomotic dehiscence or bleeding

关键词： Classification Tracheal defect Tracheal reconstruction

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Nomogram for predicting disease-specific survival in osteosarcoma

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Chinese Medical Journal 2022年第9期135卷 1126-1128页

作者： xia Yang Yajie Yang xin Weng Meng Zhang Department of Pathology Sir Run Run Shaw hospital of Zhejiang UniversityZhejiang 310020China Department of Pathology Shenzhen Second People's HospitalShenzhenChina

To the Editor:Osteosarcoma(OS)is the most common malignant primary bone tumor majorly affecting children,adolescents,and young adults.Statistic studies showed that up to 20%of OS patients have clinically detectable metastatic tumor at presentation,and>85%of metastases occurs in the lung.Thus,identifying risk factors that reflect the biological characteristics and survival of OS could lead to better interventions for patients.

关键词： lung osteosarcoma patients

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Combined classifier for cross-project defect prediction： an extended empirical study

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Frontiers of Computer Science 2018年第2期12卷 280-296页

作者： Yun ZHANG David LO Xin XIA Jianling SUN College of Computer Science and Technology Zhejiang University Hangzhou 310027 China School of Information Systems Singapore Management University Singapore 641674 Singapore

To facilitate developers in effective allocation of their testing and debugging efforts, many software defect prediction techniques have been proposed in the literature. These techniques can be used to predict classes that are more likely to be buggy based on the past history of classes, methods, or certain other code elements. These techniques are effective provided that a sufficient amount of data is available to train a prediction model. However, sufficient training data are rarely available for new software projects. To resolve this problem, cross-project defect prediction, which transfers a prediction model trained using data from one project to another, was proposed and is regarded as a new challenge in the area of defect prediction. Thus far, only a few cross-project defect prediction techniques have been proposed. To advance the state of the art, in this study, we investigated seven composite algorithms that integrate multiple machine learning classifiers to improve cross-project defect prediction. To evaluate the performance of the composite algorithms, we performed experiments on 10 open-source software systems from the PROMISE repository, which contain a total of 5,305 instances labeled as defective or clean. We compared the composite algorithms with the combined defect predictor where logistic regression is used as the meta classification algorithm （CODEPLogistic）, which is the most recent cross-project defect prediction algorithm in terms of two standard evaluation metrics： cost effectiveness and F-measure. Our experimental results show that several algorithms outperform CODEPLogistic：Maximum voting shows the best performance in terms of F-measure and its average F-measure is superior to that of CODEPLogistic by 36.88%. Bootstrap aggregation （Bagging J48） shows the best performance in terms of cost effectiveness and its average cost effectiveness is superior to that of CODEPLogistic by 15.34%.

关键词： defect prediction cross-project classifier combination

Conductive and tribological properties of TiN-Ag composite coatings under grease lubrication

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Friction 2021年第4期9卷 774-788页

作者： Feihu LIN Yanqiu xia xin FENG School of Energy Power and Mechanical Engineering North China

TiN-Ag composite coatings were prepared by pulsed bias arc ion plating.X-ray diffraction(XRD)and energy dispersive X-ray spectroscopy(EDS)were applied to analyze the compositions of the coatings.Tribological properties of the coatings were studied using an MFT-R4000 ball-on-disk friction tester in the presence of lubricating greases containing multilayer graphene.Scanning electron microscopy(SEM),Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS)were used to analyze the worn surface compositions of the lubricating films.The results show that with the decrease in Ag in the film,hardness increased but electrical conductivity decreased.The coating with 10 at%Ag content shows the best friction-reducing and anti-wear properties,which can be attributed to the moderate content of Ag embedded in the TiN crystal gap that enhanced the grain bonding force to improve the anti-wear and self-lubricating ability.Graphene can be adsorbed on the coating as a solid lubricant.

关键词： silver tribology contact resistance lubricating grease

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