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Peroxyacetyl nitrate measurem.nts by thermal dissociation-chemical ionization mass spectrometry in an urban environm.nt： perform.nce and characterizations

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Frontiers of Environm.ntal Science & Engineering 2017年第4期11卷 145-152页

作者： Xinfeng Wang Tao Wang Likun Xue wei nie Zheng Xu Steven C. n. Poon Wenxing Wang Environm.nt Research Institute Shandong University Jinan 250100 China Departm.nt of Civil and Environm.ntal Engineering Hong Kong Polytechnic University Hong Kong 999077 China Institute for Climate and Global Change Research & School of Atmospheric Sciences Nanjing University Nanjing 210023 China

Peroxyacetyl nitrate （PAn） is an important indicator of photochemical smog and has adverse effects on hum.n health and vegetation growth. A rapid and h!ghly selective technique of thermal dissociation chemical ionization mass spectrometry （TD-CImS） was recently developed to measure the abundance of PAn in real time; however, it may be subject to artifact in the presence of nitric oxide （nO）. In this study, we tested the interference of the PAn signal induced by nO, evaluated the perform.nce of TD- CImS in an urban environm.nt, and investigated the concentration and formation of PAn in urban Hong Kong. nO caused a significant underestimation of the PAn signal in TD-CImS, with the underestimation increasing sharply with nO concentration and decreasing slightly with PAn abundance. A formula was derived to link the loss of PAn signal with the concentrations of nO and PAn, which can be used for data correction in PAn measurem.nts. The corrected PAn data from TD- CImS were consistent with those from the comm.nly used gas chromatography with electron capture detection, which confirms the utility of TD-CImS in an urban environm.nt in which nO is abundant. In autumn of 2010, the hourly average PAn mixing ratio varied from 0.06 ppbv to 5.17 ppbv, indicating the occurrence of photochemical pollution in urban Hong Kong. The tbrmation efficiency of PAn during pollution episodes was as high as 3.9 to 5.9 ppbv per 100 ppbv ozone. The efficiency showed a near-linear increase with nO, concentration, suggesting a control policy of nO,. reduction for PAn pollution.

关键词： TD-CImS Peroxyacetyl nitrate Interference Photochemical pollution Formation efficiency

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Diffusion and mixing in fluid flow via the resolvent estimate

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Science China mathematics 2021年第3期64卷 507-518页

作者： Dongyi wei School of mathematical Sciences Peking UniversityBeijing 100871China Beijing International Center for mathematical Research Peking UniversityBeijing 100871China

In this paper, we first present a Gearhart-Pruss type theorem with a sharp bound for m-accretive operators. Then we give two applications:(1) we give a simple proof of the result proved by Constantin et al. on relaxation enhancem.nt induced by incompressible flows;(2) we show that shear flows with a class of weierstrass functions obey logarithmically fast dissipation time-scales.

关键词： mixing resolvent estimate shear flows weierstrass functions

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The m.nimal measurem.nt number for generalized conjugate phase retrieval

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Science China mathematics 2022年第3期65卷 655-664页

作者： wei Dan College of Big Data and Internet Shenzhen Technology UniversityShenzhen 518118China

The generalized conjugate phase retrieval problem aims to reconstruct a complex signal x ∈ C^(n) from quadratic measurem.nts x*A_(1)x,...,x*A_(m)x,where A_(1),...,A_(m)∈R^(n×n) are real symmetric *** equivalent formulation for generalized conjugate phase retrieval along with the m.nimal measurem.nt number required for accurate retrieval(up to a global phase factor as well as conjugacy) is derived in this *** present a set of nine vectors in R^(4) and prove that it is conjugate phase retrievable on C^(4).This result implies the measurem.nt number bound 4n-6 is not optimal for some n,which confirms a conjecture in the article by Evans and Lai(2019).

关键词： phase retrieval measurem.nt number conjugate

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STROnG COnVERGEnCE OF THE EULER-mARUYAmA mETHOD FOR A CLASS OF STOCHASTIC VOLTERRA InTEGRAL EQUATIOnS

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Journal of Computational mathematics 2022年第4期40卷 607-623页

作者： wei Zhang School of mathematical Sciences Heilongjiang UniversityHarbin 150080China

In this paper,we consider the Euler-maruyama method for a class of stochastic Volterra integral equations(SVIEs).It is known that the strong convergence order of the Eulermaruyama method is ***,the strong superconvergence order 1 can be obtained for a class of SVIEs if the kernelsσi(t,t)=0 for i=1 and 2;otherwise,the strong convergence order is ***,the theoretical results are illustrated by some numerical examples.

关键词： Strong convergence Stochastic Volterra integral equations Euler-maruyama method Lipschitz condition

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Platelet-activating factor receptor affects food intake and body weight

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Genes & Diseases 2015年第3期2卷 255-260页

作者： wei Li Thomas m.mcIntyre Departm.nts of Cellular and molecular medicine Lerner Research InstituteCleveland ClinicUSA molecular medicine Cleveland Clinic Lerner College of Medicine of Case Western Reserve UniversityClevelandOHUSA

“Let’s move!”is a comprehensive initiative,launched by the First Lady,michelle Obama,dedicates to solving problems of obesity,which is growing in *** life behaviors do affect obesity;however,the mechanistic insight in molecular level is still not *** this study,by continually m.nitoring mouse body weight under chow and high fat western diets as well as metabolic,physical activity and food intake behaviors assessed in a CLAmS Comprehensive Lab Animal m.nitoring System,we dem.nstrated that the platelet-activating factor receptor(PTAFR)contributes to modification of life *** does not affect metabolism of ingested dietary fat and carbohydrate in young animals;however,Ptafr ablation dramatically increased weight gain without affecting adipose tissue ***/mice possess new habits that increased food intake and decreased *** studies suggest that regulation of PTAFR activity may be a novel strategy to control obesity in children or young adults.

关键词： Behavior Food intake Obesity Physical activity Platelet-activating factor

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OnFractional(g,f,n′,m)-Critical Covered Graphs

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Journal of the Operations Research Society of China 2024年第2期12卷 446-460页

作者： wei Gao wei-Fan Wang School of Information Science and Technology Yunnan Normal UniversityKunming 650500YunnanChina Departm.nt of mathematics Zhejiang Normal UniversityJinhua 321004ZhejiangChina

The main contribution in this article is threefold:(1)we show the necessary and sufficient condition for graphs to be fractional(g,f)-covered which can be expressed in different forms,and extended to fractional(g,f,m)-covered graphs;(2)the concept of fractional-critical covered graph is put forward and its necessary and sufficient condition is given;(3)we present the degree condition for a graph to be fractional(g,f,n′,m)-critical covered,and show that degree bound is sharp when m is ***,the related result in fractional(a,b,n′,m)-critical covered setting is also verified.

关键词： network Fractional factor Data transmission Fractional covered graph Fractional critical covered graph

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光稀释效应对O_(2)近红外气辉星载测风的影响

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光谱学与光谱分析 2025年第1期45卷 160-169页

作者：李昊天李发泉李娟王后茂武魁军何微微烟台大学物理与电子信息学院山东烟台264005 中国科学院精密测量科学与技术创新研究院湖北武汉430071 中国科学院西安光学精密机械研究所陕西西安710119 中国科学院国家空间科学中心北京100190

利用星载光谱成像干涉仪测量O_(2)(a^(1)Δ^(g))日辉的多普勒频移信息是目前实现全球临近空间大气风场探测的先进技术手段,观测谱线O 19 P 18(7772.030 cm^(-1))的多普勒频移,可以在40~80 km的空间区域进行高精度和高灵敏度的风速测量,... 详细信息

利用星载光谱成像干涉仪测量O_(2)(a^(1)Δ^(g))日辉的多普勒频移信息是目前实现全球临近空间大气风场探测的先进技术手段,观测谱线O 19 P 18(7772.030 cm^(-1))的多普勒频移,可以在40~80 km的空间区域进行高精度和高灵敏度的风速测量,然而其探测精度受大气散射的具体影响尚不明晰。文章旨在分析光稀释效应对临近空间大气风场探测的影响,并对其引起的测风误差进行定量评估。首先介绍了O_(2)(a^(1)Δ^(g))光谱和大气散射的光谱特性。采用最新的HITRAn光谱参数、光化学反应速率常数以及大气模型计算得到O_(2)(a^(1)Δ^(g))不同反应机制的贡献。结合光化学反应速率计算得到O_(2)(a^(1)Δ^(g))的体辐射率,并分析了太阳天顶角对体辐射率分布的影响,基于爱因斯坦系数和谱线强度分别计算得到O_(2)(a^(1)Δ^(g))在不同温度和自吸收效应条件下的光谱辐射模型,并分析了不同地理气象因素对大气散射光谱造成的影响。其次,介绍了临边观测多普勒非对称空间外差光谱仪(DASH)的测量技术原理,描述了如何去除大气散射分量以生成纯净的气辉干涉图,基于DASH仪器概念对获取干涉图像的正演过程进行了阐释。再次,针对反演问题引入了“剥洋葱算法”,在考虑自吸收效应和光稀释效应影响的情况下,消除了目标层上方大气层贡献,解决了干涉图像中目标层信息的提取问题。最后,通过误差分析得到了大气风场探测精度廓线及其随地理气象因素影响的变化规律,证明光稀释效应的存在降低了干涉图对比度并增加了测量噪声,这对临边观测权重和有效信噪比产生了不利影响。研究表明,在45~80 km的切线高度范围内,测风精度受大气散射的影响较小,其误差约为2~3 m·s^(-1);而在45 km以下,测风精度受光稀释效应的影响随海拔高度的降低而急剧增大,且受地表反照率、气溶胶和云量等因素的影响而显著升高,在同时考虑三种因素影响的情况下,其探测下限最低约为40 km。

关键词：临近空间光稀释效应测量精度大气风场光学仪器

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High-sensitivity formaldehyde gas sensor based on Ce-doped urchin-like SnO_(2) nanowires derived from calcination of Sn-mOFs

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Frontiers of materials Science 2024年第1期18卷 29-43页

作者： wei Xiao wei Yang Shantang Liu Hubei Key Lab of novel Reactor&Green Chemical Technology School of Chemistry and Environmental EngineeringWuhan Institute of TechnologyWuhan 430073China Hubei Key Laboratory of Wudang Local Chinese medicine Research Department of ChemistrySchool of Pharmaceutical SciencesHubei University of MedicineShiyan 442000China

metal-organic frameworks(mOFs)have attracted widespread attention due to their regular structures,multiple material centers,and various *** are always considered as one kind of ideal templates for developing highly sensitive and selective gas *** this study,the advantages of mOFs with the high specific surface area(71.9891 m^(2)·g^(-1))and uniform morphology were fully utilized,and urchin-like SnO_(2) nanowires were obtained by the hydrothermal method followed by the calcination using Sn-mOFs consisting of the ligand of C_(9)H_(6)O_(6)(H_(3)BTC)and Sn/Ce center ions as sacrificial *** unique urchin-like nanowire structure facilitated gas diffusion and adsorption,resulting in superior gas sensitivity.A series of Ce-doped SnO_(2) nanowires with different doping ratios were synthesized,and their gas sensing properties towards formaldehyde were *** resulted Ce-SnO_(2) was revealed to have high sensitivity(201.2 at 250℃),rapid response(4 s),long-term stability,and good repeatability for formaldehyde sensing,and the gas sensing mechanism of Ce-SnO_(2) exposed to formaldehyde was also systematically discussed.

关键词： Ce-SnO_(2) SnO_(2) gas sensor formaldehyde Sn-mOF

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The prospects for China＇＇s food security and imports： Will China starve the world via imports？

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Journal of Integrative Agriculture 2017年第12期16卷 2933-2944页

作者： HUAnG Ji-kun wei wei CUI Qi XIE wei China Center for Agricultural Policy School of Advanced Agricultural Sciences Peking University Beijing 100871 P.R. China Center for Chinese Agricultural Policy Institute of Geographical Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 P.R.China University of Chinese Academy of Sciences Beijing 100049 P.R.China

China＇s food supply and dem.nd have significant implications for both China＇s own national food security and that of the world. This study reviews China＇s food security prospects and their implications, focusing on international trade in the com.ng decade. The results show that China＇s policies for ensuring food security will be enhanced and China will move to sustainable agriculture. most studies anticipate that China will increase its food and feed imports in the com.ng decade. China＇s overall food self-sufficiency is likely to fall from 94.5% in 2015 to around 91% by 2025. The greatest increases in imports are likely to be soybean, maize, sugar, and dairy products. However, within the production capacity of the major exporting countries and of m.ny food-importing developing countries, China＇s additional imports of 3 to 5% of its total food consumption in the com.ng decade are unlikely to threaten global food security. Indeed, the projected imports of feed and several foods could provide opportunities for m.ny exporting countries to expand their production and save global resources.

关键词： food security food supply import China global

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The barrier layer in the south-ern region of the South China Sea

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Chinese Science Bulletin 2001年第16期46卷 1388-1392页

作者： WU wei m.Tomczak FAnG Xinhua WU Dexing Laboratory of Physical Oceanography Institute of Physical OceanographyOcean University of QingdaoQingdao 266003China Flinders Institute of Atmospheric and marine Sciences Flinders University of South AustraliaAdelaide 5001Australia 不详

By analysing the CTD data in the southernregion of the South China Sea gathered during six cruisesbetween 1989 and 1999, a barrier layer with seasonalvariation just like what exists in the equatorial oceans isfound in this region. It is the first discovery in such amarginal sea yet. It is strong in autumn and a little weak in summer and winter. The thicker the barrier layer, the higher the average temperature of the upper mixed layer. The region with the thicker barrier layer overlaps the region with thehigher average temperature of the upper mixed layer, andaccords with the thicker region of the warm pool in the South China Sea got from the Levitus data. The barrier layer in the southern region of the South China Sea has significantinfluence on the heat storage of the upper ocean there.

关键词： barrier layer South China Sea thermocline pycnocline mixed layer.

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