检索结果-南通市图书馆

A CNN-SVR model for NO_(2)profile prediction based on MAX-DOAS observations:The influence of Chinese New Year overlapping the 2020 COVID-19 lockdown on vertical distributions of tropospheric NO_(2)in Nanjing,China

引用

Journal of Environmental Sciences 2024年第7期141卷 151-165页

作者： Xin Tian Zijie Wang Pinhua Xie Jin Xu Ang Li Yifeng Pan Feng hu zhaokun hu Mingsheng Chen Jiangyi Zheng Information Materials and Intelligent Sensing Laboratory of Anhui Province Institutes of Physical Science and Information TechnologyAnhui UniversityHefei 230601China Key laboratory of Environmental Optical and Technology Anhui Institute of optics and Fine MechanicsHefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China School of Environmental Science and Optoelectronic Technology University of Science and Technology of ChinaHefei 230026China

In this study,a hybrid model,the convolutional neural network-support vector regression model,was adopted to achieve prediction of the NO_(2)profile in Nanjing from January 2019to March 2021.Given the sudden decline in NO_(2)in February 2020,the contribution of the Coronavirus Disease-19(COVID-19)lockdown,Chinese New Year(CNY),and meteorologi cal conditions to the reduction of NO_(2)was evaluated.NO_(2)vertical column densities(VCDs) from January to March 2020 decreased by 59.05%and 32.81%,relative to the same period in 2019 and 2021,respectively.During the period of 2020 COVID-19,the average NO_(2)VCDs were 50.50%and 29.96%lower than those during the pre-lockdown and post-lockdown pe riods,respectively.The NO_(2)volume mixing ratios(VMRs)during the 2020 COVID-19 lock down significantly decreased below 400 m.The NO_(2)VMRs under the different wind fields were significantly lower during the lockdown period than during the pre-lockdown period This phenomenon could be attributed to the 2020 COVID-19 lockdown.The NO_(2)VMRs be fore and after the CNY were significantly lower in 2020 than in 2019 and 2021 in the same period,which further proves that the decrease in NO_(2)in February 2020 was attributed to the COVID-19 lockdown.Pollution source analysis of an NO_(2)pollution episode during the lockdown period showed that the polluted air mass in the Beijing-Tianjin-Hebei was trans ported southwards under the action of the north wind,and the subsequent unfavorable meteorological conditions(local wind speed of<2.0 m/sec)resulted in the accumulation o pollutants.

关键词： MAX-DOAS CNN-SVR Nitrogen dioxide COVID-19 Chinese New Year Regional transport

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

Observation on the aerosol and ozone precursors in suburban areas of Shenzhen and analysis of potential source based on MAX-DOAS

引用

Journal of Environmental Sciences 2023年第10期132卷 109-121页

作者： Hairong Zhang Ang Li zhaokun hu Hongmei Ren Hongyan Zhong Jianfeng Guo Long Yun Mingdi Zhang Key Laboratory of Environmental Optics and Technology Anhui Institute of Optics and Fine MechanicsHefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031China University of Science and Technology of China Hefei 230026China Institutes of Physical Science and Information Technology Anhui UniversityHefei 230601China Shenzhen Environmental Monitoring Center Station Shenzhen 518049China

Long-term stereoscopic observations of aerosol,NO2,and HCHO were carried out at the Yangmeikeng(YMK)site in Shenzhen.Aerosol optical depths and NO2 vertical column concentration(NO2 VCD)derived from MAX-DOAS were found to be consistent with other datasets.The total NO2 VCD values of the site remained low,varying from 2×10^(15)to 8×10^(15)mol/cm^(2),while the HCHO VCD was higher than NO2 VCD,varying from 7×10^(15)to 11×10^(15)mol/cm^(2).HCHO VCD was higher from September to early November than that was from mid-late November to December and during February 2021,in contrast,NO2 VCD did not change much during the same period.In January,NO2 VCD and HCHO VCD were both fluctuating drastically.High temperature and HCHO level in the YMK site is not only driving the ozone production up but alsomay be driving up the ozone concentration as well,and the O_(3)production regime in the YMK site tends to be NOx-limited.At various altitudes,backward trajectory clustering analysis and Potential Source Contribution Function(PSCF)were utilized to identify possible NO2 and HCHO source locations.The results suggested that the huizhou-Shanwei border and the Daya Bay Sea area were the key potential source locations in the lower(200 m)and middle(500 m)atmosphere(WPSCF>0.6).The WPSCF valuewas high at the 1000maltitude whichwas closer to the YMKsite than the near ground,indicating that the pollution transport capability in the upper atmosphere was limited.

关键词： Multi-axial differential optical absorption spectroscopy (MAX-DOAS) Nitrogen dioxide(NO2) Formaldehyde(HCHO) Potential source contribution function(PSCF)

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

Long-term observations of tropospheric NO_2, SO_2 and HCHO by MAX-DOAS in Yangtze River Delta area, China

引用

Journal of Environmental Sciences 2018年第9期30卷 207-221页

作者： Xin Tian Pinhua Xie Jin Xu Ang Li Yang Wang Min Qin zhaokun hu School of Environmental Science and Optoeclectronic Technology University of Science and Technology of China Hefei 230026 China. Key laboratory of Environmental Optical and Technology Anhui Institute of Optics and Fine Mechanies Chinese Academy of ScienceHefei 2:30031 China CAS Center for Excellence in Urban Atmospheric Environment Institute of Urban Environment Chinese Academy of Sciences Xiamen361021 China Max Planck Institute for Chemistry Mainz 55128 Germany

Yangtze River Delta （YRD） area is one of the important economic zones in China. However, this area faces increasing environmental problems. In this study, we use ground-based multi-axis differential optical absorption spectroscopy （MAX-DOAS） network in Eastern China to retrieve variations of NO2, SO2, and formaldehyde （HCHO） in the YRD area. Three cities of YRD （Hefei, Nanjing, and Shanghai） were selected for long-term observations. This paper presents technical performance and characteristics of instruments, their distribution in YRD, and results of vertical column densities （VCDs） and profiles of NO2, SO2, and HCHO. Average diurnal variations of tropospheric NO2 and SO2 in different seasons over the three stations yielded minimum values at noon or in the early afternoon, whereas tropospheric HCHO reached the maximum during midday hours. Slight reduction of the pollutants in weekends occurred in all the three sites. In general trace gas concentrations gradually reduced from Shanghai to Hefei. Tropospheric VCDs of NO2, SO2, and HCHO were compared with those from Ozone Monitoring Instrument （OMI） satellite observations, resulting in R2 of 0.606, 0.5432, and 0.5566, respectively. According to analysis of regional transports of pollutants, pollution process happened in YRO under the north wind with the pollution dissipating in the southeast wind. The feature is significant in exploring transport of tropospheric trace gas pollution in YRD, and provides basis for satellite and model validation.

关键词： MAX-DOAS instrument column densities NO2 HCHO SO2 Yangtze River Delta area Pollution transport

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

Variation of temporal and spatial patterns of NO_2 in Beijing using OMI and mobile DOAS

引用

Science China Chemistry 2015年第9期58卷 1367-1376页

作者： Ang Li Jie Zhang Pinhua Xie zhaokun hu Jin Xu Fusheng Mou Fengcheng Wu Jianguo Liu Wenqing Liu Key Laboratory of Environmental Optical and Technology Anhui Institute of Optics and Fine Mechanics Chinese Academy of Sciences School of Environmental and Photoelectric Technology University of Science and Technology of China

Control policies such as "odd-and-even license plate rule" were implemented by the Chinese government to restrict traffic and suspend factory production in Beijing and neighboring cities during the Asia-Pacific Economic Cooperation summit. We use ozone monitoring instrument(OMI), mobile differential optical absorption spectroscopy(DOAS), and multi-axis differential optical absorption spectroscopy(MAX-DOAS) to measure the variation of the spatial and temporal patterns of NO2 column densities from October 24, 2014 to November 22, 2014. It is found that the NO2 column densities during the episode of control policies are significantly lower than those during other periods, and the emission flux of NO2 calculated by mobile DOAS is also lower than the results from other periods. Some daily low NO2 column densities occur with the northwest wind direction. We then compare the relationship between OMI and mobile DOAS NO2 column density observations, and the results of mobile DOAS are approximately 2.7 times larger than the OMI values. The largest discrepancy occurs in the northern part of Beijing city. In other parts, the two instruments have a better correlation coefficient(R2) of 0.61. The low NO2 column densities that occur during the episode of control policies are affected by the control policies as well as meteorological conditions.

关键词： DOAS 空间利用变异模式时间差分光学吸收光谱浓度控制 NO2 中国政府

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

甲型流感病毒H1N1型灭活病毒标准物质研究

引用

计量学报 2024年第2期45卷 294-299页

作者：许丽乐丽欢杨雪王炤坤李兰英闻艳丽陶晴胡轶红刘刚上海市计量测试技术研究院国家市场监管重点实验室(生物分析计量溯源) 上海201203 中国科学院上海免疫与感染研究所公共技术服务中心病原发现与大数据平台上海200031

以人工培养真实病毒为原料,研制了一种甲型流感病毒H1N1型灭活病毒标准物质。该标准物质经化学灭活及灭活效果验证后,联合多家实验室采用数字PCR定量检测方法对拷贝数浓度进行定值,对标准物质的均匀性、稳定性及不确定度进行了评估。结... 详细信息

以人工培养真实病毒为原料,研制了一种甲型流感病毒H1N1型灭活病毒标准物质。该标准物质经化学灭活及灭活效果验证后,联合多家实验室采用数字PCR定量检测方法对拷贝数浓度进行定值,对标准物质的均匀性、稳定性及不确定度进行了评估。结果显示该标准物质均匀性良好,在-80~-70℃保存条件下稳定保存5个月,标准物质最终定值结果为(1384.5±249.3)copies/μL(k=2)。该标准物质可为H1N1型甲型流感病毒检测的全过程提供计量溯源和质量控制支撑,有助于提升相关核酸检测结果的准确性和可靠性。

关键词：生物计量学甲型流感病毒 H1N1 灭活病毒标准物质数字PCR

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

Effect of aluminum on microstructure and magnetic properties of sintered Nd-Fe-B magnets processed by grain boundary diffusion of Tb-Al

引用

Journal of Rare Earths 2023年第5期41卷 705-712,I0003页

作者： Tinghui Wang zhaokun Ma Qihang Zhu Lijing Yang Baosheng Liu Yu Zhao Cheng Xu Bizhang Zheng Fangqin hu Jianzhong Li Qingfang huang Zhenlun Song CAS Key Laboratory of Magnetic Materials and Devices Zhejiang Province Key Laboratory of Magnetic Materials and Application TechnologyNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China College of Materials Science and Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Baotou Hidyree Technology Co. Ltd.Baotou 014030China Hangzhou Permanent Magnet Group Co. Ltd.Hangzhou 311231China Ningbo Permanent Magnetics Co. Ltd.Ningbo 315201China Fujian Key Laboratory for Rare Earth Functional Materials Longyan 366300China

The grain boundary diffusion process(GBDP)of Tb can improve the coercivity of sintered Nd-Fe-B magnets.In this study,the effect of AI on the diffusion of Tb in the GBDP was investigated.The content of diffused Tb-Al was precisely controlled by adjusting the magnetron sputtering process.The Tb equivalent of Al was also studied.Results show that AI promotes the diffusion of Tb deeper into the magnet,reducing the thickness of the shell in the core-shell structure.This study is helpful for further developing the process,reducing the consumption of heavy rare earth elements(Tb),and improving the coercivity of sintered Nd-Fe-B magnets.

关键词： Sintered Nd-Fe-Bmagnet Heavy rare earth elements Grain boundary diffusion process Coercivity

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

Distinct roles of ASIC3 and TRPV1 receptors in electroacupuncture-induced segmental and systemic analgesia

引用

Frontiers of Medicine 2016年第4期10卷 465-472页

作者： Juanjuan Xin Yangshuai Su zhaokun Yang Wei He Hong Shi Xiaoyu Wang Ling hu Xiaochun Yu Xianghong Jing Bing Zhu Institute of Acupuncture and Moxibustion China Academy of Chinese Medical Sciences Beo'ing 100700 China

Previous studies have demonstrated the effects of different afferent fibers on electroacupuncture （EA）- induced analgesia. However, contributions of functional receptors expressed on afferent fibers to the EA analgesia remain unclear. This study investigates the roles of acid-sensing ion channel 3 （ASIC3） and transient receptor potential vanifioid 1 （TRPV1） receptors in EA-induced segmental and systemic analgesia. Effects of EA at acupoint ST36 with different intensities on the C-fiber reflex and mechanical and thermal pain thresholds were measured among the ASIC3-/-, TRPV1-/-, and C57BL/6 mice. Compared with C57BL/6 mice, the ipsilateral inhibition of EA with 0.8 C-fiber threshold （0.8Tc） intensity on C-fiber reflex was markedly reduced in ASIC3-/- mice, whereas the bilateral inhibition of 1.0 and 2.0Tc EA was significantly decreased in TRPV1-/- mice. The segmental increase in pain thresholds induced by 0.3 mA EA was significantly reduced in ASIC3-/- mice, whereas the systemic enhancement of 1.0 mA EA was markedly decreased in TRPV1-/- mice. Thus, segmental analgesia of EA with lower intensity is partially mediated by ASIC3 receptor on Aβ-fiber, whereas systemic analgesia induced by EA with higher intensity is more likely induced by TRPV1 receptor on Aδ- and C-fibers.

关键词： electroacupuncture analgesia ASIC3 TRPV1 C-fiber reflex

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Vertical‐organic‐nanocrystal‐arrays for crossbar memristors with tuning switching dynamics toward neuromorphic computing

引用

SmartMat 2021年第1期2卷 99-108页

作者： Fangxu Yang Lingjie Sun Qingxi Duan huanli Dong zhaokun Jing Yuchao Yang Rongjin Li Xiaotao Zhang Wenping hu Leon Chua Key Laboratory of Molecular Optoelectronic Sciences School of ScienceTianjin UniversityTianjinChina Beijing National Research Center for Molecular Sciences Chinese Academy of SciencesBeijingChina Joint School of National University of Singapore and Tianjin University International Campus of Tianjin UniversityBinhai New CityFuzhouChina Key Laboratory of Microelectronic Devices and Circuits(MOE) Institute of MicroelectronicsPeking UniversityBeijingChina Department of Electrical Engineering and Computer Sciences University of CaliforniaBerkeleyCaliforniaUSA

Memristors proposed by Leon Chua provide a new type of memory device for novel neuromorphic computing applications.However,the approaching of distinct multi‐intermediate states for tunable switching dynamics,the con-trolling of conducting filaments(CFs)toward high device repeatability and reproducibility,and the ability for large‐scale preparation devices,remain full of challenges.Here,we show that vertical‐organic‐nanocrystal‐arrays(VONAs)could make a way toward the challenges.The perfect one‐dimensional structure of the VONAs could confine the CFs accurately with fine‐tune resistance states in a broad range of 103 ratios.The availability of large‐area VONAs makes the fabrication of large‐area crossbar memristor arrays facilely,and the analog switching characteristic of the memristors is to effectively imitate different kinds of synaptic plasticity,indicating their great potential in future applications.

关键词： conducting filament memristor organic electronics organic single crystal

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Fe_(40)Cr_(25)Ni_(25)Al_(5)Ti_(5)中熵合金的微观组织和力学性能

引用

材料工程 2023年第6期51卷 93-100页

作者：胡朝辉娄照坤王鑫张利赵元余建新张璐沈阳航空航天大学材料科学与工程学院沈阳110136 哈尔滨工业大学分析测试与计算中心哈尔滨150001

采用真空电弧熔炼炉制备Fe_(40)Cr_(25)Ni_(25)Al_(5)Ti_(5)(原子分数/%)中熵合金,利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、透射电镜(TEM)及拉伸试验机研究合金固溶态和退火态的微观组织、力学性能、强化机制及变形机制。... 详细信息

采用真空电弧熔炼炉制备Fe_(40)Cr_(25)Ni_(25)Al_(5)Ti_(5)(原子分数/%)中熵合金,利用扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)、透射电镜(TEM)及拉伸试验机研究合金固溶态和退火态的微观组织、力学性能、强化机制及变形机制。结果表明:Fe_(40)Cr_(25)Ni_(25)Al_(5)Ti_(5)中熵合金固溶态为FCC+BCC1+BCC2三相固溶体组织,屈服强度为520 MPa,断裂强度为852 MPa,伸长率为13%。经600℃退火2 h,合金相组成未改变,颗粒状BCC2相尺寸增大,FCC区与BCC区体积分数无明显变化,屈服强度为668 MPa,断裂强度达1029 MPa,伸长率降低至9%。Fe_(40)Cr_(25)Ni_(25)Al_(5)Ti_(5)合金的强度源于共格应变强化、固溶强化及界面强化的协同作用,位错滑移为合金主要的变形机制。

关键词：中熵合金力学性能强化机制变形机制

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

重离子诱变选育高产核黄素枯草芽孢杆菌

引用

生物学杂志 2022年第4期39卷 33-37页

作者：胡建华张兆昆李永丽兰辉刘占英内蒙古工业大学化工学院呼和浩特010051 内蒙古自治区发酵产业节能减排工程技术研究中心呼和浩特010051

研究以产核黄素的枯草芽孢杆菌C0为出发菌株,经^(12)C^(6+)重离子辐射诱变后,以8-氮鸟嘌呤作为拮抗物进行高产菌株的筛选,初步获得60个诱变菌株,进一步筛选得到4株高产菌株,最后经摇瓶发酵,发现4株诱变菌株中B13的核黄素产量最高为(401.... 详细信息

研究以产核黄素的枯草芽孢杆菌C0为出发菌株,经^(12)C^(6+)重离子辐射诱变后,以8-氮鸟嘌呤作为拮抗物进行高产菌株的筛选,初步获得60个诱变菌株,进一步筛选得到4株高产菌株,最后经摇瓶发酵,发现4株诱变菌株中B13的核黄素产量最高为(401.8±9.2)mg/L,比原始菌株提高18.5%。经二次重离子诱变选育后,获得一株高产菌株BII7,核黄素产量达到(818.8±17.3)mg/L,比一次诱变菌株B13提高77.7%,表明重离子辐射对产核黄素的枯草芽孢杆菌具有良好的诱变效果。对诱变菌株BII7进行培养温度、pH值及转速等条件的优化,最适培养条件为37℃、pH 7.7、220 r/min。在5 L双联发酵罐中扩大培养高产菌株BII7,37℃、pH 7.7及溶氧浓度40%时,发酵时间缩短12 h,核黄素产量达1385.3 mg/L,比摇瓶培养提高69.2%,该诱变菌株具有较好的放大生产能力。6次传代培养实验表明该诱变高产菌株具有稳定的遗传特性。

关键词：重离子诱变选育核黄素枯草芽孢杆菌

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：