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A generalized π2-diffeomorphism finiteness theorem

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Frontiers of Mathematics in China 2020年第2期15卷 399-418页

作者： Xiaochun RONG xuchao YAO Department of Mathematics Rutgers UniversityNew BrunswickNJ 08903 USA School of Mathematical Sciences Capital Normal UniversityBeijing 100048China

Theπ2-diffeomorphism finiteness result of *** and ***(independently)asserts that the diffeomorphic types of compact n-manifolds M with vanishing first and second homotopy groups can be bounded above in terms of n,and upper bounds on the absolute value of sectional curvature and diameter of *** this paper,we will generalize thisπ2-diffeomorphism finiteness by removing the condition thatπ1(M)-0 and asserting the diffeomorphism finiteness on the Riemannian universal cover of M.

关键词： Collapsing with bounded sectional curvature diffeomorphism finiteness vanishing second homotopy group

Effect of sulfate-reducing bacteria on hydrogen permeation and stress corrosion cracking behavior of 980 high-strength steel in seawater

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Journal of Materials Science & Technology 2021年第33期92卷 109-119页

作者： Meiying Lv xuchao Chen Zhenxin Li Min Du Key Laboratory of Marine Chemistry Theory and Technology Ministry of EducationCollege of Chemistry and Chemical EngineeringOcean University of ChinaQingdao 266100China

980 high-strength steel has been widely used in marine engineering structures due to its high strength and ***,it is easily affected by the harsh environmental conditions(such as the presence of sulfate-reducing bacteria,SRB),leading to the risk of stress corrosion cracking(SCC).In this paper,the effects of SRB and its metabolites on hydrogen permeation and SCC mechanism of 980 steel in seawater solution were investigated by slow strain rate tensile test,scanning electron microscope,Xray energy spectroscopy,Raman spectroscopy and Devanathan-Stachurski double electrolytic *** demonstrated that the SCC susceptibility of 980 steel was promoted in the presence of SRB,which was related to the cultivation time of the *** SRB were cultivated for 3 d and 6 d,the SCC mechanism was controlled by hydrogen-induced cracking(HIC);while the cultivation time extended to 11 d,the SCC of 980 steel was under the combined effect of the anodic dissolution(AD) and HIC *** cultivated for 16 d,the SCC of 980 steel was caused by the dominant *** the SRB accelerated hydrogen permeation under cathodic depolarization process and SRB assisted AD(pitting corrosion)played an enhancing role in promoting SCC susceptibility of 980 steel.

关键词： Stress corrosion cracking Sulfate-reducing bacteria Microbiologically influenced corrosion 980 High-strength steel Seawater

Role of nitrification inhibitor DMPP(3,4-dimethylpyrazole phosphate) in NO^-_3-N accumulation in greengrocery( Brassica campestris L. ssp. chinensis ) and vegetable soil

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Journal of Environmental Sciences 2005年第1期17卷 81-83页

作者： xuchao WULiang-huan JUXiao-tang ZHANGFu-suo CollegeofEnvironmentalandResourceSciences ZhejiangUniversityHangzhou310029China CollegeofResourcesandEnvironment ChinaAgriculturalUniversityBeijing100094China

The influence of nitrification inhibitor(NI) 3,4 dimethylpyrazole phosphate(DMPP) on nitrate accumulation in greengrocery( Brassica campestris L. ssp. chinensis ) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003 Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO - 3 N concentration in greengrocery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO - 3 N concentration during the prophase stage of storage.

关键词： dimethylpyrazole phosphate(DMPP) NO^-_3-N vegetable soil greengrocery( Brassica campestris L. ssp. chinensis )

Collapse of a Deep Excavated Foundation Pit in the Soft Soils by 3-D FEM

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第1期36卷 162-174页

作者： ZHUANG Haiyang XUE xuchao YU Xu Institute of Geotechnical Engineering Shandong University Institute of Geotechnical Engineering Nanjing Tech University School of Architecture Engineering Nanjing Institute of Technology

In view of the collapse of a deep excavated foundation pit of the Xianghu subway underground station in Hangzhou of China,the main features of the accident are analyzed,and the induced factors of the accident are summarized. Then,a 3-D FEM analysis model is created to demonstrate the soil-support structures interaction system,and the effect of the main factors,such as the volume replacement ratio of the bottom soil reinforcing,the asymmetric ground overload,the embedded depth of the diaphragm wall,the shear strength of the bottom soils disturbed by the construction,and the excessive excavation of the bottom soil,are analyzed and compared. The results show that the ineffective original reinforcement plan for the bottom soft soil is the most prominent factor for the accident,and the disturbance effect of the deep excavation on the shear strength of the bottom soft soil is another significant factor for the accident. Meanwhile,if the reinforcement of the bottom soft soil is canceled,an appropriate extension of the diaphragm retaining walls to the under lying harder soil layer can also effectively prevent the collapse of the deep excavated foundation pit. In addition,the partly excessive excavation in the process has a great influence on the axial force of the most nearby horizontal support but few effect on the stability of the diaphragm wall. Thus,the excessive excavation of the bottom soils should not be the direct inducing factor for the accident. To the asymmetric ground overload,it should be the main factor inducing the different damage conditions of the diaphragm walls on different sides. According to the numerical modeling and actual engineering accident condition,the development process of the accident is also identified.

关键词： deep excavation subway station collapse process numerical modeling soft soil

Mechanism of Fixation of Ozone and Its Medical Value

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Journal of Wuhan University of Technology(Materials Science) 2014年第6期29卷 1183-1186页

作者：朱磊 MIN Xinmin WANG xuchao Chemistry Department School of Sciences Wuhan University of Technology State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology

Because of both ozone gas and ozone solution are instable which limits the application of ozone, to solve the storage problem, it is necessary to find a kind ofideal ozone carrier which can combine ozone as an ＂ozonic compound＂ in which the bond strength between ozone and carrier should not be too high or too low, to appropriately release ozone from the ozonic compound. Combining Criegee’s three-step reaction mechanism of ozone and olefins, the charge, covalent bond levels and energy levels of ozone, ethylene, butadiene and their ozonic compounds were calculated by the first-principles calculation method based on density functional theory methods. The stability of the ozonide, or the bond strength between ozone and ions of carrier were controlled felicitously to release ozone from the ozonide with proper velocity. Ozone antimicrobial was composed on the above principle. It can be used conveniently, especially for common families.

关键词： ozone fixation carrier release velocity antimicrobial

Mapping soil erodibility in southeast China at 250 m resolution:Using environmental variables and random forest regression with limited samples

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International Soil and Water Conservation Research 2022年第1期10卷 62-74页

作者： Zhiyuan Tian Feng Liu Yin Liang xuchao Zhu State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil ScienceChinese Academy of SciencesNanjing210008China

Soil erodibility(K factor)mapping has been accomplished mainly by soil map-linked or geo-statistical ***,the resulting maps usually have coarse spatial resolution at a regional *** objectives of this study were a)to map the K factors using a set of environmental variables and random forest(RF)model,and b)to identify the important environmental variables in the predictive mapping on a regional *** collected 101 surface soil samples across southeast China in the summer of *** each sample,we measured the particle size distribution and organic matter content,and calculated the K factors using the nomograph *** hyperparameters of RF were optimized through 5-fold cross validation(m_(ay)=2,n_(tree)=500,p=63),and a digital map with 250 m resolution was generated for the K *** lower and upper limits of a 90% prediction interval were also pro-duced for uncertainty *** was found that the important environmental variables for the K factor prediction were relief,climate,land surface temperature and vegetation *** the existing K factor map has an average polygonal area of 6.8 km^(2),our approach dramatically improves the spatial resolution of the K factor to 0.0625 km^(2).The new method captures more distinct differences in spatial details,and the spatial distribution of the K factor derived from RF prediction followed a similar pattern with kriging *** suggests the presented approach in this study is effective for mapping the K factor with limited sampling data.

关键词： Soil K factor Predictive soil mapping Machine learning Uncertainty

Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers

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Journal of Environmental Sciences 2005年第4期17卷 584-588页

作者： SUNYue LIXiao-tao xuchao CHENJin-long LIAi-min ZHANGQuan-xing StateKeyLaboratoryofPollutionControlandResourcesReuse SchooloftheEnvironmentNanjingUniversityNanjing210093China.

Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

关键词： hypercrosslinked polymer catechol adsorption thermodynamics kinetics

Pinpointing and scheduling access conflicts to improve internal resource utilization in solid-state drives

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Frontiers of Computer Science 2019年第1期13卷 35-50页

作者： xuchao XIE Liquan XIAO Dengping WEI Qiong LI Zhenlong SONG Xiongzi GE College of Computer National University of Defense TechnologyChangsha 410073China Department of Computer Science University of MinnesotaMinneapolisMN 55455USA

Modern solid-state drives (SSDs)are integrating more internal resources to achieve higher *** accesses across internal resources can potentially enhance the performance of ***,exploiting parallelism inside SSDs is challenging owing to real-time access *** this paper,we propose a highly parallelizable I/O scheduler (PIOS)to improve internal resource utilization in SSDs from the perspective of I/O ***, we first pinpoint the conflicting flash requests with precision during the address translation in the Flash Translation Layer (FTL).Then,we introduce conflict eliminated requests (CERs)to reorganize the I/O requests in the device-level queue by dispatching conflicting flash requests to different *** to the significant performance discrepancy between flash read and write operations,PIOS employs differentiated scheduling schemes for read and write CER queues to always allocate internal resources to the conflicting CERs that are more *** small dominant size prioritized scheduling policy for the write queue significantly decreases the average write *** high parallelism density prioritized scheduling policy for the read queue better utilizes resources by exploiting internal parallelism *** evaluation results show that the paralle/izable I/O scheduler (PIOS)can accomplish better SSD performance than existing I/O schedulers implemented in both SSD devices and operating systems.

关键词： solid-state drive access conflict I/O scheduler internal resource utilization PIOS

Three-Dimensional Urban Thermal Effect across a Large City Cluster during an Extreme Heat Wave:Observational Analysis

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Journal of Meteorological Research 2022年第3期36卷 387-400页

作者： Yue MA Ping LIANG Sue GRIMMOND xuchao YANG Jun LYU Yihui DING Key Laboratory of Cities’Mitigation and Adaptation to Climate Change in Shanghai Shanghai Regional Climate CenterChina Meteorological AdministrationShanghai 200030China Shanghai Jiading District Meteorological Bureau Shanghai 201800China Department of Meteorology University of ReadingReading RG66ETUnited Kingdom Ocean College Zhejiang UniversityZhoushan 316021China Jiangsu Meteorological Information Center Jiangsu Meteorological BureauNanjing 210008China National Climate Center China Meteorological AdministrationBeijing 100081China

Given extensive and rapid urbanization globally,assessing regional urban thermal effects(UTE)in both canopy and boundary layers under extreme weather/climate conditions is of significant *** population and economic growth in the Yangtze River Delta(YRD)have made it one of the largest city clusters in ***,we explore the three-dimensional(3D)UTE in the YRD using multi-source observations from high-resolution automatic weather stations,radiosondes,and eddy covariance sensors during the record-setting heat wave(HW)of July-August *** is found that the regional canopy layer UTE is up to 0.6-1.2℃,and the nocturnal UTE(0.7-1.6℃)is larger than daytime UTE(0.2-0.5℃)during the *** regional canopy layer UTE is enhanced and expanded northwards,with some rural sites contaminated by the urban influences,especially at *** the boundary layer,the strengthened regional UTE extends vertically to at least 925 hPa(~750 m)during this *** strengthened 3D UTE in the YRD is associated with an enlarged Bowen ratio difference between urban and non-urban *** findings about the 3D UTE are beneficial for better understanding of the thermal environment of large city clusters under HW and for more appropriate adaption and mitigation strategies.

关键词： urban thermal effect three-dimensional Yangtze River Delta heat wave