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A meteorologically adjusted ensemble Kalman filter approach for inversing daily emissions:A case study in the Pearl River Delta,China

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Journal of Environmental Sciences 2022年第4期34卷 233-248页

作者： Guanglin Jia Zhijiong Huang Xiao Tang Jiamin Ou Menghua Lu Yuanqian Xu Zhuangmin Zhong Qing’e Sha Huangjian Wu Chuanzeng Zheng Tao Deng Duohong Chen Min He Junyu Zheng School of Environment and Energy South China University of TechnologyUniversity Town CampusGuangzhou 510006China Institute for Environmental and Climate Research Jinan UniversityGuangzhou 511486China Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029China Faculty of Social and Behavioural Sciences Utrecht UniversityUtrechtCH 3584the Netherlands Guangzhou Institute of Tropical and Marine Meteorology China Meteorological AdministrationGuangzhou 510640China State Environmental Protection Key Laboratory of Regional Air Quality Monitoring Guangdong Environmental Monitoring CenterGuangzhou 510308China Department of Environmental Science and Engineering College of Architecture and EnvironmentSichuan UniversityChengdu 610065China

The conventional Ensemble Kalman filter(EnKF),which is now widely used to calibrate emission inventories and to improve air quality simulations,is susceptible to simulation errors of meteorological inputs,making accurate updates of high temporal-resolution emission inventories challenging.In this study,we developed a novel meteorologically adjusted inversion method(MAEInv)based on the EnKF to improve daily emission estimations.The new method combines sensitivity analysis and bias correction to alleviate the inversion biases caused by errors of meteorological inputs.For demonstration,we used the MAEInv to inverse daily carbon monoxide(CO)emissions in the Pearl River Delta(PRD)region,China.In the case study,60%of the total CO simulation biases were associated with sensitive meteorological inputs,which would lead to the overestimation of daily variations of posterior emissions.Using the new inversion method,daily variations of emissions shrank dramatically,with the percentage change decreased by 30%.Also,the total amount of posterior CO emissions estimated by the MAEInv decreased by 14%,indicating that posterior CO emissions might be overestimated using the conventional EnKF.Model evaluations using independent observations revealed that daily CO emissions estimated by MAEInv better reproduce the magnitude and temporal patterns of ambient CO concentration,with a higher correlation coefficient(R,+37.0%)and lower normalized mean bias(NMB,-17.9%).Since errors of meteorological inputs are major sources of simulation biases for both low-reactive and reactive pollutants,the MAEInv is also applicable to improve the daily emission inversions of reactive pollutants.

关键词： Emission inversion Daily emissions Meteorological adjustment Ensemble Kalman filter

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Tuning electronic properties of cobalt phthalocyanines for oxygen reduction and evolution reactions

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Science China Chemistry 2024年第1期67卷 398-407页

作者： Jianlin Jiang Zhen Liu Shuaijun Pan Xinnian Xia Bing Qin Yang Hu Xuxu Wang jiamin Lan Yu Gu Encai ou Weijian Xu Joseph J.Richardson Rui Guo SINOPEC Research Institute of Petroleum Processing Co. Ltd.Beijing 100083China College of Chemistry and Chemical Engineering Hunan UniversityChangsha 410082China College of Chemistry and Materials Science Hunan Agricultural UniversityChangsha 410128China Department of Chemical Engineering The University of MelbourneParkville 3010Australia College of Environmental Science and Engineering Hunan UniversityChangsha 410082China School of Engineering RMIT UniversityMelbourneVictoria 3001Australia

Metal–phthalocyanines are a class of catalytically active materials promising in energy conversion and storage fields(e.g.,electrocatalysis).However,understanding and controlling the electrochemical properties in metal-phthalocyanine systems is challenging.Herein,we elucidate the electrocatalytic origins of a series of cobalt-phthalocyanine molecular catalysts and finetune their electronic properties at the atomic level,both experimentally and computationally.The interactions between the cobalt center and the local coordination environment are regulated by introducing either electron-donating or electron-withdrawing groups on the phthalocyanine ligand,and the spin-orbit splitting of cobalt is increased by~0.15 eV compared with the nonsubstituted ligand.Specifically,the aminated cobalt phthalocyanine-based electrocatalysts exhibit low free energies in the ratedetermining steps of the oxygen reduction(-1.68 eV)and oxygen evolution reactions(0.37 eV).This contributes to the high electrocatalytic activity(e.g.,a halfwave potential of 0.84 V and an overpotential of 0.30 V at 10 mAcm^(-2)),featuring a high selectivity of a four-electron pathway(i.e.,a negligible by-product of hydrogen peroxide).These catalysts also exhibit exceptional kinetic current density(Tafel slope of 100 mV dec^(-1))in oxygen reduction reactions,in addition to a superior power density(158 mWcm^(-2))and a high cycling stability(>1,300 cycles)in Zn-air batteries,outperforming the commercial Pt/C and/or RuO2counterparts.

关键词： interfacial wettability molecular catalysts carbon nanotubes density functional theory electrochemistry

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改进Retinex-Net的低光照图像增强算法

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模式识别与人工智能 2021年第1期34卷 77-86页

作者：欧嘉敏胡晓杨佳信广州大学电子与通信工程学院广州510006

针对Retinex-Net存在噪声较大、颜色失真的问题,基于Retinex-Net的分解-增强架构,文中提出改进Retinex-Net的低光照图像增强算法.首先,设计由浅层上下采样结构组成的分解网络,将输入图像分解为反射分量与光照分量,在此过程加入去噪损失... 详细信息

针对Retinex-Net存在噪声较大、颜色失真的问题,基于Retinex-Net的分解-增强架构,文中提出改进Retinex-Net的低光照图像增强算法.首先,设计由浅层上下采样结构组成的分解网络,将输入图像分解为反射分量与光照分量,在此过程加入去噪损失,抑制分解过程产生的噪声.然后,在增强网络中引入注意力机制模块和颜色损失,旨在增强光照分量亮度的同时减少颜色失真.最后,反射分量和增强后的光照分量融合成正常光照图像输出.实验表明,文中算法在有效提升图像亮度的同时降低增强图像噪声.

关键词：低光照图像增强深度网络视网膜大脑皮层网络(Retinex-Net) 浅层上下采样结构注意机制模块

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基于背景抑制与上下文感知的人群计数网络

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计算机工程 2022年第9期48卷 314-320页

作者：黄奕秋胡晓杨佳信欧嘉敏广州大学电子与通信工程学院广州510006 广州大学机械与电气工程学院广州510006

针对图像背景噪声、透视畸变等影响人群计数网络计数精度的问题,提出一种基于背景抑制与上下文感知的新网络。利用VGG-16网络提取图像特征,并分别将特征输入密度图生成模块和背景噪声抑制(BNS)模块中进行处理,生成密度特征图和空间注意... 详细信息

针对图像背景噪声、透视畸变等影响人群计数网络计数精度的问题,提出一种基于背景抑制与上下文感知的新网络。利用VGG-16网络提取图像特征,并分别将特征输入密度图生成模块和背景噪声抑制(BNS)模块中进行处理,生成密度特征图和空间注意力图。使用BNS模块优化密度特征图并生成初级密度图,以抑制图像中背景噪声干扰,提高人群区域的特征权重。为减少透视畸变对人群密度估计的影响,使用上下文感知增强网络优化初级密度图,并生成预测密度图。在ShanghaiTech、UCF-CC-50及UCF-QNRF 3个公开数据集上的实验结果表明,该网络相较于MCNN、SwitchCNN、CSRNet等网络的计算准确度较高,尤其在UCF-QNRF数据集上其平均绝对误差和均方误差分别为85.8、146.0,相较于其他网络最高分别下降69.0%和67.2%,能充分抑制图像背景噪声并有效减小透视畸变引起的误差,具有良好的泛化能力和较强的鲁棒性。

关键词：人群计数深度学习密度图背景噪声上下文感知

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Triples of almost primes

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Science China Mathematics 2023年第12期66卷 2779-2794页

作者： jiamin Li Jianya Liu School of Mathematics Shandong UniversityJinan 250100China

The k-tuple conjecture of Hardy and Little wood predicts that there are infinitely many primes p such that p+2 and p+6 are primes simultaneously.In this paper,we prove that there are infinitely many primes p such that Ω(p+2)≤3 and Ω(p+6)≤6,where Ω(n) denotes the total number of prime divisors of an integer n.We also prove a better conditional result,with the above Ω(p+6)≤6 replaced by Ω(p+6)≤3,under the Elliott-Halberstam conjecture.

关键词： the k-tuple conjecture of Hardy and Littlewood almost prime vector sieve weighted sieve

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Solving the transient response of the randomly excited dry friction system via piecewise RBF neural networks

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Science China(Technological Sciences) 2023年第5期66卷 1408-1416页

作者： QIAN jiamin CHEN LinCong SUN JianQiao College of Civil Engineering Huaqiao UniversityXiamen361021China Key Laboratory for Intelligent Infrastructure and Monitoring of Fujian Province Huaqiao UniversityXiamen361021China Department of Mechanical Engineering School of EngineeringUniversity of CaliforniaMercedCA95343USA

Over the years,practical importance and interesting dynamical features have caused a growing interest in dry friction systems.Nevertheless,an effective approach to capture the non-smooth transition behavior of such systems is still lacking.Accordingly,we propose a piecewise radial basis function neural network(RBFNN)strategy to solve the transient response of the randomly excited dry friction system.Within the established framework,the transient probability density function of the dry friction system is expressed in a piecewise form.Each segment of the solution is expressed by the sum of a series of Gaussian activation functions with time-dependent weights.These time dependent weights are solved by minimizing the loss function,which involves the residual of the Fokker-Planck-Kolmogorov equations and constraint conditions.To avoid the singularity of the initial condition being a Dirac delta function,a short-time Gaussian approximation strategy is presented to solve the initiating time-dependent weights.Based on some numerical results,the proposed scheme effectively performs.Moreover,a comparison with other existing methods reveals that the proposed scheme can completely capture the nonlinear characteristic of the dry friction system stochastic response more closely.Noteworthy,we can easily extend the proposed method to other types of non-smooth systems with piecewise response characteristics.Moreover,the semi-analytical solution provides a valuable reference for system optimization.

关键词： dry friction system transient response semi-analytical solution piecewise RBF neural networks

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Single and combined effects of secondary polyethylene microplastic on the growth of Pak choi and the soil microbiome composition

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FRONTIERS OF ENVIRONMENTAL SCIENCE & ENGINEERING 2024年第5期18卷 53-53页

作者： Hu, jiamin Xie, Zhenwen Zuo, Jiane Tsinghua Univ Sch Environm State Key Joint Lab Environm Simulat & Pollut Cont Beijing 100084 Peoples R China Tsinghua Univ Tsinghua Shenzhen Int Grad Sch Shenzhen 518055 Peoples R China

It has been confirmed that microplastics (MPs) are present in the environment. This study simulated secondary PE-MPs via aging and mechanical processes to evaluate their effects on Pak choi (Brassica rapa L.) over 21 d. Two common pollutants, dichlorodiphenyltrichloroethane (DDT) and naphthalene, were used in the combined toxicity tests. The results indicated that the growth of Pak choi was significantly inhibited after exposure to secondary PE-MPs, and the combined effects were antagonistic, owing to the adsorption capacity of secondary PE-MPs to DDT and naphthalene. Oxidative stress in Pak choi can be markedly affected, leading to oxidative damage to plant cells. The moisture content, soil bulk density, soil density, cation exchange capacity (CEC), and FDA hydrolase in the planted soils increased in the treated groups, and the TOC content changed significantly. We also found that the microbial composition of the soil in the DDT and naphthalene groups showed more significant alterations than that in the other groups. Alpha diversity analysis showed that species diversity increased in the combined groups but indicated a clear downward trend in the single MPs groups. This study suggests that secondary PE-MPs harm the growth of Pak choi and can change soil properties, revealing the harm to the ecosystem of MPs in the soil.

关键词： Secondary PE-MPs Combined effects Oxidative stress Soil properties Bacterial community POLYCYCLIC AROMATIC-HYDROCARBONS MULCH DEGRADATION FRACTIONS TOXICITY FILM DDT

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对比增强磁敏感加权成像序列与肺癌脑转移瘤检出的相关性

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中国医学物理学杂志 2022年第5期39卷 556-561页

作者：黎嘉敏区杰浩李晓丹康庄周美娟南方医科大学公共卫生学院放射医学系广东广州510515 广东省人民医院(广东省医学科学院)放射科广东广州510080 中山大学附属第三医院放射科广东广州510630

目的:研究对比增强磁敏感加权成像(CE-SWI)与肺癌脑转移瘤检出的相关性。方法:病例组选取肺癌脑转移瘤病例50例,对照组选取高血压病例50例,分析SWI与CE-SWI检出微出血的病例数、病灶个数、最大直径,采用χ^(2)检验分析两组检出的差异,采... 详细信息

目的:研究对比增强磁敏感加权成像(CE-SWI)与肺癌脑转移瘤检出的相关性。方法:病例组选取肺癌脑转移瘤病例50例,对照组选取高血压病例50例,分析SWI与CE-SWI检出微出血的病例数、病灶个数、最大直径,采用χ^(2)检验分析两组检出的差异,采用Logistic回归分析CE-SWI与肺癌脑转移瘤、高血压微出血的相关性。结果:CE-SWI在病例组检出患者45例,病灶数127个,最大直径5.428(3.663,11.405)mm;在对照组检出患者28例,病灶数121个,最大直径3.259(2.206,4.325)mm,χ^(2)检验得出两组病例检出均有统计学差异(P<0.05)。相关性检验中,病例组发生微出血的优势比高于高血压组,差异有统计学意义(P<0.05)。结论:CE-SWI对于微出血和脑转移瘤的检出敏感,肺癌脑转移、高血压都是微出血的危险因素,但肺癌脑转移瘤引起的微出血发生率显著增加。

关键词：肺癌脑转移瘤磁敏感加权成像对比增强微出血

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Investigation on switchable operation states in a Tm/Ho co-doped fiber laser based on nonlinear optical loop mirror

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Optoelectronics Letters 2023年第8期19卷 455-461页

作者： WANG Xiaofa PAN jiamin HE Yiping School of Optoelectronic Engineering Chongqing University of Posts and TelecommunicationsChongqing 400065China

The nonlinear pulse dynamics have been studied in a thulium/holmium co-doped passively mode-locked fiber laser based on nonlinear optical loop mirror(NOLM).By enhancing the nonlinear effect of the cavity and without changing the polarization state of the cavity,four types of operation states that switch between each other,including the basic mode-locking pulse,the two solitons pulse,the bright-dark pulse,and the harmonic mode-locking pulse,can be obtained.Compared with the laser of single mode-locking state,passively mode-locked fiber lasers(PMLFLs) with switchable operation states can be used in a wide range of applications,such as optical communication,material processing and optical fiber sensing technology.

关键词： fiber optical passive

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Generation and evolution of bright-dark pulses in a thulium/holmium co-doped fiber laser based on nonlinear polarization rotation

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Optoelectronics Letters 2023年第12期19卷 710-715页

作者： WANG Xiaofa HE Yiping PAN jiamin Chongqing Key Laboratory of Photoelectronic Information Sensing and Transmitting Technology School of Optoelectronic EngineeringChongqing University of Posts and TelecommunicationsChongqing 400065China

We report an experimental phenomenon of the splitting and merging of the bright-dark pulses(BDPs)in a mode-locked thulium/holmium co-doped fiber laser(THDFL)based on nonlinear polarization rotation(NPR).By adding 100-m-long highly nonlinear fiber(HNLF)into a simple ring cavity,the BDPs can be generated.The time interval between the bright and dark pulses increases linearly with the pump power and approximately equals to the inverse of the modulation frequency of the radio frequency(RF)spectrum.Apart from that,the bright and dark pulses are shown not to be orthogonally polarized.The obtained results are valuable for the evolutionary mechanism of the BDPs in passively mode-locked fiber lasers(PMLFLs).

关键词： fiber polarization pump

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