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Characterization of machined surface quality and near-surface microstructure of a high speed thrust angular contact ball bearing

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Journal of Materials Science & Technology 2021年第27期86卷 219-226页

作者： Di Wu Xiao-Chen zhang yi-Feng Li Jianqiu Wang En-Hou han Institute of Metal Research Chinese Academy of Sciences62 Wencui RoadShenyang110016China School of Materials Science and Engineering University of Science and Technology of China72 Wenhua RoadShenyang110016China Institute of Materials Shanghai University99 Shangda RoadShanghai200072China

Bearings are one of the most important components in modern *** contact fatigue(RCF)initiating from surface and subsurface is the major failure *** this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstructure of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were *** is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and *** other is nano-crystalline layer due to machining,in the outermost layer around the surface of *** results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.

关键词： Rolling bearing GCr15 Race-way Rolling ball Machined surface quality Surface nano-crystalline layer

Microalloying Al alloys with Sc:a review

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Rare Metals 2020年第6期39卷 636-650页

作者： Jin-Yu zhang yi-han Gao Chong Yang Peng zhang Jie Kuang Gang Liu Jun Sun State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China

As a kind of important light alloys,the Al alloys exhibit mechanical properties that are closely related to the *** the main alloying elements and adjusting heat treatments are usually approaches to tune the microstructure and hence artificially control the mechanical ***,the windows for the two approaches have become quite narrow,after extensive studies in the last half of *** has become the most promising strategy to further modify the microstructure and improve the mechanical properties of Al alloys,among which the element of scandium(Sc)is especially *** this paper,the recent progresses in Al alloys microalloyed with Sc are briefly reviewed,focusing on the microstructural characterization,strengthening response,and underlying *** possible key research points are also proposed for the further development of Al alloys microalloyed with Sc and other rare earth elements.

关键词： Al alloys Microalloying effect Scandium Mechanical properties

Key minerals influencing apple quality in Chinese orchard identified by nutritional diagnosis of leaf and soil analysis

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Journal of Integrative Agriculture 2015年第5期14卷 864-874页

作者： WANG Guo-yi zhang Xin-zhong WANG yi XU Xue-feng han Zhen-hai Institute for Horticultural Plants China Agricultural University Yantai Research Institute China Agricultural University

We investigated the correlation between leaf/soil minerals and fruit quality in apple trees grown in orchards,with the ultimate goal of improving the *** mineral nutrients;soil nutrients in the 0-20,20-40,and 40-60 cm layers;and fruit quality traits in 32 apple orchards in China were monitored for 2 *** factors associated with fruit quality were identified via correlation *** analysis of leaf data revealed that leaf nitrogen（N） and leaf magnesium（Mg） levels were extremely high in 75 and 89%of the orchards,*** the Bohai Gulf region,94%of the orchards showed significantly higher values than the *** soil pH values of the orchards in eastern China like eastern Shandong or Liaoning were lower than 7.0,while the pH values in the Loess Plateau of northwestern China like Shaanxi were much higher than *** alkali-hydrolyzable N levels in 47%of the orchards were lower than the optimal level of 70 mg kg^-***,the soil alkali-hydrolyzable N levels of orchards in the Bohai Gulf region were significantly higher than those in the Loess Plateau *** available P levels in the orchards of the Bohai Gulf region were up to three times higher than those of the Loess Plateau ***,although the available potassium（K） in most orchards was sufficient（51.39-309.94 mg kg^-1）,leaf K content in 73%of the orchards was low,possibly due to fruit bagging or fruit *** 63%of the orchards in Shandong and 29%of the orchards in Shannxi showed leaf Fe *** the Loess Plateau,most orchards showed high leaf Ca levels,a strong correlation was observed between leaf and soil phosphorus/potassium（P/K）content and fruit organic acid *** amounts of fruit soluble sugar or fructose were positively correlated with soil calcium/potassium（Ca/K） levels and leaf calcium/boron（Ca/B） levels in most *** excessive leaf N levels caused by the extensive application of N fertilizers had a negative effect on

关键词： apple nutrients minerals potassium phosphorus fruit Plateau Bohai monitored fructose

Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N, N-Diallylbenzoylamide

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Chinese Chemical Letters 2003年第8期14卷 771-772页

作者： yi Min HU Yu zhang Jian Lin han Cheng Jian ZHU yi PAN School of Chemistry and Chemical Engineering Nanjing UniversityNanjing 210093

A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excel... 详细信息

关键词： Palladium Heck reaction benzyl halides cyclization cascade reaction.

Load Shedding Strategy Based on Combined Feed-Forward Plus Feedback Control over Data Streams

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Journal of Beijing Institute of Technology 2019年第3期28卷 437-446页

作者： Donghong han yi Fang Daqing yi yifei zhang Xiang Tang Guoren Wang School of Computer Science and Engineering Northeastern UniversityShenyang 100819LiaoningChina School of Computer Science Carnegie Mellon UniversityPittsburghPAUSA

In data stream management systems (DSMSs), how to maintain the quality of queries is a difficult problem because both the processing cost and data arrival rates are highly unpredictable. When the system is overloaded, quality degrades significantly and thus load shedding becomes necessary. Unlike processing overloading in the general way which is only by a feedback control (FB) loop to obtain a good and stable performance over data streams, a feedback plus feed-forward control (FFC) strategy is introduced in DSMSs, which have a good quality of service (QoS) in the aspects of miss ratio and processing delay. In this paper, a quality adaptation framework is proposed, in which the control-theory-based techniques are leveraged to adjust the application behavior with the considerations of the current system status. Compared to previous solutions, the FFC strategy achieves a good quality with a waste of fewer resources.

关键词： data stream management systems (DSMSs) load shedding feedback control feed-forward control quality of service (QoS)

Estimation of transpiration coefficient and aboveground biomass in maize using time-series UAV multispectral imagery

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The Crop Journal 2022年第5期10卷 1376-1385页

作者： Guomin Shao Wenting han Huihui zhang yi Wang Liyuan zhang Yaxiao Niu Yu zhang Pei Cao College of Mechanical and Electronic Engineering Northwest A&F UniversityYangling 712100ShaanxiChina Key Laboratory of Agricultural Internet of Things Ministry of AgricultureYangling 712100ShaanxiChina Institute of Water-Saving Agriculture in Arid Areas of China Northwest A&F UniversityYangling 712100ShaanxiChina Water Management and Systems Research Unit USDA-ARS2150 Centre AvenueBldg.D.Fort CollinsCO 80526USA College of Information Xi’an University of Finance and EconomicsXi’an 710100ShaanxiChina Institute of Soil and Water Conservation Northwest A&F UniversityYangling 712100ShaanxiChina University of Chinese Academy of Sciences Beijing 100049China

Estimating spatial variation in crop transpiration coefficients(CTc) and aboveground biomass(AGB)rapidly and accurately by remote sensing can facilitate precision irrigation management in semiarid regions. This study developed and assessed a novel machine learning(ML) method for estimating CTc and AGB using time-series unmanned aerial vehicle(UAV)-based multispectral vegetation indices(VIs)of maize under several irrigation treatments at the field scale. Four ML regression methods: multiple linear regression(MLR), support vector regression(SVR), random forest regression(RFR), and adaptive boosting regression(ABR), were used to address the complex relationship between CTcand VIs. AGB was then estimated using exponential, logistic, sigmoid, and linear equations because of their clear mathematical formulations based on the optimal CTcestimation model. The UAV VIs-derived CTcusing the RFR estimation model yielded the highest accuracy(R^(2)= 0.91, RMSE = 0.0526, and n RMSE = 9.07%). The normalized difference red-edge index, transformed chlorophyll absorption in reflectance index, and simple ratio contributed significantly to the RFR-based CTcmodel. The accuracy of AGB estimation using nonlinear methods was higher than that using the linear method. The exponential method yielded the highest accuracy(R^(2)= 0.76, RMSE = 282.8 g m, and n RMSE = 39.24%) in both the 2018 and 2019 growing seasons. The study confirms that AGB estimation models based on cumulative CTcperformed well under several irrigation treatments using high-resolution time-series UAV multispectral VIs and can support irrigation management with high spatial precision at a field scale.

关键词： Crop transpiration Normalized difference red-edge index Unmanned aerial vehicles Random forest regression Biomass

Fast frequency response of inverter-based resources and its impact on system frequency characteristics

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Global Energy Interconnection 2020年第5期3卷 475-485页

作者： Lining Su Xiaohui Qin Shang zhang Yantao zhang yilang Jiang yi han China Electric Power Research Institute Haidian DistrictBeijing 100192P.R.China

The inertia response and primary frequency regulation capability of synchronous grids are declining owing to the increasing penetration of inverter-based resources. The fast frequency response(FFR) of inverter-based resources is an important mitigation option for maintaining grid security under the conditions of low inertia and insufficient primary frequency response capability. However, the understanding and technical characteristics of the FFR of inverter-based resources are still unclear. Aiming at solving the aforementioned problems, this paper proposes a definition for FFR based on the impact mechanism of FFR on system frequency. The performance requirements of FFR are clarified. Then, the effects of FFR on system frequency characteristics are further analyzed based on steady-state frequency deviation, the initial rate of change of frequency, and the maximum transient frequency deviation. Finally, the system requirements for FFR and its application effects are verified by simulating an actual bulk power grid, providing technical support for subsequent engineering application.

关键词： Fast frequency response Rate of change of frequency Frequency deviation ROCOF-based FFR Deviation-based FFR

Sinusoidal obstruction syndrome: A systematic review of etiologies,clinical symptoms, and magnetic resonance imaging features

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World Journal of Clinical Cases 2019年第18期7卷 2746-2759页

作者： Yun zhang han-Yu Jiang yi Wei Bin Song Department of Radiology Sichuan University West China Hospital

BACKGROUND Sinusoidal obstruction syndrome (SOS) is a kind of rare liver disease which is characterized by damage to small hepatic vessels, affecting particularly the sinusoidal endothelium. Due to the special etiology and high mortality, early diagnosis of SOS is significant for clinical survival and prognosis. AIM To generalize the common etiologies and clinical symptoms of SOS and summarize the characteristic magnetic resonance imaging (MRI) features so as to provide more valuable information for early diagnosis of SOS. METHOD We searched PubMed, Web of science, Wanfang Data, China Knowledge Resource Integrated, VIP, and Cochrane Library databases without a limiting period and the types of articles. The search process mainly revolved around the etiologies, common clinical symptoms, and MRI imaging features of SOS. Ultimately, 29 full articles were included in this review and 222 articles were excluded. RESULTS Eleven case reports included 13 patients. The etiologies of these patients including chemotherapy (5/13), medicinal herbs containing pyrrolidine alkaloids (PAs, e.g. Tusanqi)(4/13), hematopoietic stem cell transplantation (HSCT)(2/13), drug toxicity (6-thioguanine)(1/13), and “poppers”, a recreational drug used during anal intercourse (1/13). Eighteen case series including 497 patients, and SOS in 465 (93.6%) patients was caused by PAs. Ascites, abdominal pain and swelling, jaundice were the most common clinical symptoms. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (GGT), total bilirubin (TBil), direct bilirubin (DBil), and prothrombin time (PT) had varying degrees of *** signals on T1 weighted imaging/T2 weighted imaging (T1WI/T2WI), heterogeneous enhancement of liver parenchyma, ascites, hepatomegaly, narrowing and blurring of intrahepatic inferior vena cava and three main hepatic veins, edema around the portal vein, and gallbladder wall edema were the most

关键词： Sinusoidal obstruction syndrome Hematopoietic stem cell transplantation Chemotherapy Tusanqi Ascites

The method of variation on parameters for integration of a generalized Birkhoffian system

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Acta Mechanica Sinica 2011年第6期27卷 1059-1064页

作者： yi zhang College of Civil Engineering Suzhou University of Science and Technology 215011 Suzhou China

This paper focuses on studying the integration method of a generalized Birkhoffian *** method of variation on parameters for the dynamical equations of a generalized Birkhoffian system is *** procedure for solving the problem can be divided into two steps：the first step,a system of auxiliary equations is constructed and its general solution is given;the second step,the parameters are varied,and the solution of the problem is obtained by using the properties of generalized canonical *** method of variation on parameters for the generalized Birkhoffian system is of universal significance,and we take a nonholonomic system and a nonconservative system as examples to illustrate the application of the results of this paper.

关键词： Birkhoffian system Method of integration Variation on parameter. Nonholonomic constraint. Nonconservative system