检索结果-南通市图书馆

Spatiotemporal changes in sunshine duration and its influential factors in Chongqing,China from 1961 to 2020

Journal of Mountain Science 2024年第6期21卷 2005-2024页

作者： LI Jun XIA Hongxuan JIANG Jinge xu weifeng WEN Di xu Junfeng College of Geography and Tourism Chongqing Normal UniversityChongqing 401331China Key Laboratory of GIS Application of Chongqing Chongqing 401331China Chongqing Key Laboratory of Earth Surface Processes and Environmental Remote Sensing in Three Gorges Reservoir area Chongqing 401331China Institute of Remote Sensing and Earth Sciences School of Institute of Remote Sensing and Earth SciencesSchool of ScienceHangzhou Normal UniversityHangzhou 311121China

The surface solar radiation in most parts of the world has undergone a phenomenon known as global dimming and brightening,characterized by an initial decrease followed by an *** a result,the sunshine duration(SD)has decreased in the past 60 *** the backdrop of global dimming and brightening,SD has decreased to varying degrees in many regions of *** the observed data of SD,cloud amount(total cloud amount and low cloud amount,abbreviated as TCA and LCA),precipitation,and relative humidity(RH)from 34 meteorological stations in Chongqing during the period of 1961-2020,along with a digital elevation model(DEM)with a resolution of 90 m,this study analyzed the spatiotemporal variations and influencing factors of *** analysis employed methods such as linear regression,Mann-Kendall test,wavelet transformation,and DEM-based possible SD distributed *** results showed that the annual SD in Chongqing has significantly decreased over the last 60 years,with a decreasing interannual trend rate(ITR)of 40.4 h/*** for no obvious trend in spring,SD decreased significantly in summer,autumn and winter at the ITR of 21.1 h/10a,8.5 h/10a and 7.5 h/10a,*** abrupt decrease in the annual SD was found in *** difference before and after the abrupt decrease was 177.7 *** difference before and after the abrupt decrease was 177.7 *** annual SD possessed the oscillation period of *** spatial heterogeneity of the mean annual SD during the last 60 years was *** distribution of SD in Chongqing is high in the northeast and low in the *** addition,about 73%of the total area in Chongqing showed a significant and very significant decreasing *** regions with significant changes are mainly concentrated in the regions with altitudes of 200~1000 *** increasing LCA was the main cause of the decrease of the annual SD in the regions with 200-400 m altitude decreased the most and changed the *** LCA is the prim

关键词： Sunshine duration Spatiotemporal changes Mann-Kendall test Wavelet analysis Geodetector model

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

基于改进YOLOv7的麦穗检测算法

引用

吉林大学学报（理学版） 2024年第4期62卷 886-894页

作者：陈森徐伟峰王洪涛雷耀华北电力大学(保定)计算机系河北保定071003 河北省能源电力知识计算重点实验室河北保定071003

针对麦穗数据集中存在的检测目标密集、遮挡、各地区形态不一致现象引起的漏检、模型泛化能力弱等问题,提出一种基于改进YOLOv7的麦穗检测算法.首先,在YOLOv7网络的骨干特征提取网络引入混合注意力机制加强对位置特征的提取,缓解检测目... 详细信息

针对麦穗数据集中存在的检测目标密集、遮挡、各地区形态不一致现象引起的漏检、模型泛化能力弱等问题,提出一种基于改进YOLOv7的麦穗检测算法.首先,在YOLOv7网络的骨干特征提取网络引入混合注意力机制加强对位置特征的提取,缓解检测目标密集导致的漏检问题;其次,在骨干特征提取网络引入能结合不同尺寸的可切换空洞卷积(switchable atrous convolution, SAC),通过增大感受野实现提取不同尺度的特征信息,可有效改善因遮挡现象引起的漏检问题;最后,在特征融合部分引入增量学习模块(example vector correction, EVC),提高模型的鲁棒性和泛化能力.实验结果表明,改进后的麦穗识别算法在全球小麦麦穗数据集的平均目标检测精度与原YOLOv7相比提高了2.11个百分点.

关键词：小麦麦穗检测混合注意力增量学习空洞卷积

来源：

维普期刊数据库

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Through-thickness heterogeneity in creep properties of friction stir welding 7B50-T7451 aluminum alloy thick plate joint:Experiments and modeling

引用

Chinese Journal of Aeronautics 2023年第6期36卷 378-389页

作者： Huan WANG weifeng xu Hongjian LU Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical UniversityXi'an 710072China

Through-thickness heterogeneity in creep properties of 7B50-T7451 aluminum alloy Friction Stir Welding(FSW)joints was *** tests for three slices of the FSW joint were conducted at the temperature of 150-200℃ and applied stress of 60-225 *** theta projection method was used to predict creep curves and minimum creep *** results show that the minimum creep rate increases and creep rupture life decreases with the increase of creep temperature and applied *** properties of the FSW joint deteriorate along the thickness direction from the top to the *** threshold stress of all three slices of the FSW joint decreases with the increase of creep temperature and even disappears at 200℃ for the bottom *** activation energy approaches the activation energy of the lattice self-diffusion of *** value of true stress exponent for different slices is approximately equal to *** predominant creep mechanism of the FSW joint is dislocation viscous glide by lattice *** is more,a constitutive model is established based on the theta method to accurately describe creep behavior ofdifferent slices of the FSW joint.

关键词： 7B50 high strength aluminum alloy Creep mechanism Creep modeling Friction stir welding Theta projection method Through-thickness heterogeneity

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

血清FGF23对2型糖尿病患者冠状动脉钙化的预测价值

引用

全科医学临床与教育 2024年第3期22卷 212-215页

作者：王琦徐卫锋诸暨市第三人民医院内一科浙江诸暨311825 诸暨市人民医院肾内科

目的评估血清全段成纤维细胞生长因子(FGF23)对2型糖尿病患者冠状动脉钙化的预测价值。方法选择2022年1月至2023年1月门诊及住院的2型糖尿病患者共86例为2型糖尿病患者组,选择年龄、性别匹配的80例健康体检者为对照组。比较两组患者的... 详细信息

目的评估血清全段成纤维细胞生长因子(FGF23)对2型糖尿病患者冠状动脉钙化的预测价值。方法选择2022年1月至2023年1月门诊及住院的2型糖尿病患者共86例为2型糖尿病患者组,选择年龄、性别匹配的80例健康体检者为对照组。比较两组患者的临床资料,血压、血脂、肾功能、钙磷代谢指标,血清FGF23及冠状动脉钙化发生率等。分析血清FGF23及碱性磷酸酶(AKP)对2型糖尿病患者冠状动脉钙化的预测价值。结果2型糖尿病患者组的糖化血红蛋白(HbA1c)、血清FGF23、收缩压(SBP)、舒张压(DBP)、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)、甘油三脂(TG)、尿蛋白肌酐比值(UACR)、血磷、钙磷乘积、AKP以及冠状动脉钙化发生率均明显高于对照组,高密度脂蛋白胆固醇(HDL-C)低于对照组,差异均有统计学意义(t分别=6.32、5.12、3.65、4.25、5.78、2.47、3.45、5.12、2.45、2.47、3.89,χ^(2)=3.46,t=-2.46,P均<0.05)。多元线性回归分析,logFGF23与吸烟、血磷、AKP、UACR、冠状动脉钙化有相关性(t分别=9.02、5.69、6.35、7.65、12.89,P均<0.05)。受试者工作特征曲线(ROC)结果显示,血清FGF23预测2型糖尿病患者合并冠状动脉钙化的曲线下面积为0.70(95%CI 0.62~0.78),当检测的截点为305.52 pg/mL时,其灵敏度及特异度分别为76.73%及68.12%。血清AKP预测2型糖尿病患者合并冠状动脉钙化的曲线下面积为0.62(95%CI 0.55~0.70),当检测的截点为67.15 mmol/L,其灵敏度及特异度分别为66.52%及58.26%。结论2型糖尿病患者有更高的血清FGF23水平,血清FGF23对2型糖尿病患者合并冠状动脉钙化具有较好的预测价值。

关键词：成纤维细胞生长因子23 2型糖尿病钙磷代谢碱性磷酸酶冠状动脉钙化

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Quantitative Verification of Knowledge Precondition for Open System

引用

Chinese Journal of Electronics 2016年第2期25卷 227-233页

作者： xu weifeng LIU Shufen WANG Xiaoyan College of Computer Science and Technology Jilin University

A quantitative verification method is proposed to quantitatively verify knowledge precondition of actions and plans. Probability epistemic game structure(PEGS) is proposed to model knowledge preconditions in open systems, an extension of concurrent game structure with probabilistic transition. We introduce a probability operator P-λinto Alternating temporal epistemic logic(ATEL) and define a Probability alternating-time temporal epistemic logic(PATEL) for quantitatively model checking the properties of PEGS. We designed an algorithm to compute the probability aiming at model checking verification problems of PATEL based on DTMC and *** convert a portion of the PATEL verification problems into PATL problems by defining the knowledge formulas Ka φ, EA sφ and CA sφ as atomic propositions. We study a train controller using PRISM-games to demonstrate the applicability of above quantitative verification method.

关键词： Quantitative verification Knowledge precondition Alternating-time temporal logic(ATL) Open system

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Influence of Test Temperature on the Tensile Properties along the Thickness in a Friction Stir Welded Aluminum Alloy

引用

Journal of Materials Science & Technology 2015年第9期31卷 953-961页

作者： weifeng xu Jinhe Liu Daolun Chen State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Department of Mechanical and Industrial Engineering Ryerson University

The aim of this study was to evaluate microstructures and the influence of test temperature on the tensile properties, strain hardening behavior and fracture characteristics of friction stir welded （FSWed） 2219- T62 aluminum alloy thick plate joints. A fine and equiaxed recrystallized grain structure had no significant change in grains at the top of weld nugget zone （WNZ） at a rotational rate of 500 r/min compared with 300 r/min, but the grains and second-phase particles at the middle of WNZ exhibited obvious coarsen- ing. The yield strength, ultimate tensile strength and joint efficiency were observed to decrease with increasing test temperatures. However, the elongation presented a contrast trend. Compared with the middle and bottom slices, the top slice （216 and 342 MPa） had a higher strength and a lower elongation （8.5%） at different test temperatures. Hardening capacity and strain hardening exponent of bottom slices were higher than those of the top and middle slices. Both of them at room temperature （RT） were bigger than those at higher temperature （HT） and lower temperature （LT）. The FSWed joints basically failed in the border area between the thermo-mechanical affected zone （TMAZ） and heat-affected zone （HAZ） of the top slice, and in the HAZ of the middle or bottom slices, while the fracture surfaces exhibited dimple fracture characteristics at different test temperatures.

关键词： Friction stir weldingAluminum alloyMicrostructureTensile propertiesStrain hardeningTest temperature

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Comparative study on local and global mechanical properties of bobbin tool and conventional friction stir welded 7085-T7452 aluminum thick plate

引用

Journal of Materials Science & Technology 2018年第1期34卷 173-184页

作者： weifeng xu Yuxuan Luo Wei Zhang Mingwang Fu State Key Laboratory of Solidification Processing Shaanxi Key Laboratory of Friction Welding Technologies Northwestern Polytechnical University Department of Mechanical Engineering The Hong Kong Polytechnic University

7085-T7452 plates with a thickness of 12 mm were welded by conventional single side and bobbin tool friction stir welding （SS-FSW and BB-FSW, respectively） at different welding parameters. The temperature distribution, microstructure evolution and mechanical properties of joints along the thickness direction were investigated, and digital image correlation （DIC） was utilized to evaluate quantitatively the deformation of different zones during tensile tests. The results indicated that heat-affected zone （HAZ）, the local softening region, was responsible for the early plastic deformation and also the fracture location for SS-FSW samples, while a rapid fracture was observed in weld nugget zone （WNZ） before yield behavior for all BB-FSW specimens. The ultimate tensile strength （UTS） of SS-FSW joints presented the highest value of 410 MPa, 82% of the base material, at a rotational speed of 300 rpm and welding speed of 60 mm/min, much higher than that of BB-FSW joints, with a joint efficiency of only 47%. This should be attributed to the Lazy S defect produced by a larger extent of heat input during the BB-FSW process, The whole joint exhibited a much higher elongation than the slices. Scanning electron microscopic （SEM） analysis of the fracture morphologies showed that joints failed through ductile fracture for SS-FSW and brittle fracture for BB-FSW.

关键词： Aluminum alloy Friction stir welding Bobbin tool Temperature distribution Microstructure Mechanical properties

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Enantioselective esterification of(R,S)-2-(4-methylphenyl)propionic acid via Novozym 435:Optimization and application

引用

Chinese Journal of Chemical Engineering 2020年第7期28卷 1816-1823页

作者： Xin Yuan LujunWang Panliang Zhang weifeng xu Kewen Tang Department of Chemistry and Chemical Engineering Hunan Institute of Science and TechnologyYueyang 414006China

This paper reports on the resolution of(R,S)-2-(4-methylphenyl)propionic acid(MPPA)enantiomers by enzymatic esterification in organic *** 435(CALB)has the best catalytic performance compared with other *** the alcohols screened,n-hexanol is the best acyl acceptor and gives the highest enzyme activity and enantioselectivity in *** surface methodology(RSM)was used to evaluate the influence of the factors,such as temperature,enzyme amount,substrate concentration and reaction time on the substrate conversion(c)and enantiomeric excess(ee).The correlation coefficient R2 for enantiomeric excess and the conversion are 0.9827 and 0.9910,respectively,indicating that can accurately predict the experimental *** simulation and optimization,the optimal conditions were obtained,involving 600 mmol·L^-1 MPPA concentration(0.60 mmol),850 mmol·L^-1 hexanol concentration(0.85 mmol),58 mg enzyme amount,75℃temperature and 4.5 h reaction time,*** the optimized conditions,the experimental values of conversion and enantiomeric excess were 89.34%and 97.84%,respectively,which are in good agreement with the model predictions.

关键词： (R,S)-2-(4-Methylphenyl)propionic acid Novozym 435 Esterification kinetic resolution Response surface methodology

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Modeling for tungstic precipitation and extraction based on Pitzer equation

引用

Science China Chemistry 2016年第4期59卷 497-504页

作者： Xinyue Zhang Pengge Ning weifeng xu Hongbin Cao Yi Zhang School of Chemical Engineering and Technology National Engineering Research Center of Distillation TechnologyTianjin UniversityTianjin 300072China Research Centre for Process Pollution Control Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Collaborative Innovation Center of Chemical Science and Engineering(Tianjin) Tianjin 300072China

This work presented the results of tungstic precipitation from Na2WO4-Na2SO4-H20 system at 293.15 K, with which the Pitzer parameters of β（0）Na2wo4 and β（1）Na2wo4 were determined from Pitzer equation by regression. Thus the mean ionic activity coeffi- cients of sodium tungstate were calculated. The obtained β（0）Na2wo4 and β（1）Na2wo4 were substituted as fixed values in extraction modeling from Na2WO4-H2SO4-H20 system by primary amine （N1923） in toluene as diluent. Meanwhile the activity coeffi- cient expressions in organic phase were varied based on Pitzer theory that the interaction term for the solvent should not be in- cluded. The Pitzer parameters for organic phase were re-regressed in order to make the model more accurate. The average ab- solute relative deviation （AARD） for calculated and experimental molality of WO42 in aqueous phase was 5.24%. The results showed that the model can not only correlate but also predict the liquid-liquid equilibrium （LLE） data.

关键词： tungstic precipitation Pitzer parameter activity coefficient extraction

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Thermodynamic models based on Pitzer-NRTL and Pitzer-Margules equations for the extraction of tungstic acid with primary amine N1923

引用

Science China(Technological Sciences) 2015年第5期58卷 935-942页

作者： LIN Xiao NING PengGe xu weifeng CAO HongBin ZHANG Yi Research Centre for Process Pollution Control of Beijing Institute of Process Engineering Chinese Academy of Sciences Institute of Process Engineering Chinese Academy of Sciences National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Chinese Academy of Sciences

The thermodynamic model of the extraction of W with primary amine under near neutral conditions is reported in this paper. The activity coefficients of the nonelectrolytes in organic phase are calculated by the Margules and NRTL equations which are based on previously tested liquid-liquid extraction equilibrium data in combination with mass balances and charge balance formula. The activity coefficients of the electrolytes in aqueous phase are calculated by the Pitzer equation. The thermodynamic model of the extraction of W by a primary amine is constructed from the calculated activity coefficients of electrolytes and nonelectrolytes. The extraction of W using primary amine is also predicated, and the data is compared to the calculated results of the thermodynamic model. It is concluded that Margules equation proves to be suitable and reliable for calculating the activity coefficients of nonelectrolytes in complex organic phase systems.

关键词： thermodynamic neutral calculating concluded toluene dilute constants negligible tungsten purification

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：