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Improving the Forecasts of Coastal Wind Speeds in Tianjin,China Based on the WRF Model with Machine Learning Algorithms

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Journal of Meteorological Research 2024年第3期38卷 570-585页

作者： weihang zhang Meng TIAN Shangfei HAI Fei WANG Xiadong AN Wanju LI Xiaodong LI Lifang SHENG College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao266100China Tianjin Key Laboratory for Oceanic Meteorology Tianjin Institute of Meteorological ScienceTianjin300074China CMA Earth System Modeling and Prediction Centre China Meteorological Administration(CMA)Beijing100081China Qingdao Meteorological Bureau Qingdao266003China

Characterized by sudden changes in strength,complex influencing factors,and significant impacts,the wind speed in the circum-Bohai Sea area is relatively challenging to *** the western side of Bohai Bay,as the economic center of the circum-Bohai Sea,Tianjin exhibits a high demand for accurate wind *** this study,three machine learning algorithms were employed and compared as post-processing methods to correct wind speed forecasts by the Weather Research and Forecast(WRF)model for *** results showed that the random forest(RF)achieved better performance in improving the forecasts because it substantially reduced the model bias at a lower computing cost,while the support vector machine(SVM)performed slightly worse(especially for stronger winds),but it required an approximately 15 times longer computing *** back propagation(BP)neural network produced an average forecast significantly closer to the observed forecast but insufficiently reduced the *** regard to wind speed frequency forecasting,the RF method commendably corrected the forecasts of the frequency of moderate(force 3)wind speeds,while the BP method showed a desirable capability for correcting the forecasts of stronger(force>6)*** addition,the 10-m u and v components of wind(u_(10)and v_(10)),2-m relative humidity(RH_(2))and temperature(T_(2)),925-hPa u(u925),sea level pressure(SLP),and 500-hPa temperature(T_(500))were identified as the main factors leading to bias in wind speed forecasting by the WRF model in Tianjin,indicating the importance of local dynamical/thermodynamic processes in regulating the wind *** study demonstrates that the combination of numerical models and machine learning techniques has important implications for refined local wind forecasting.

关键词： machine learning Weather Research and Forecast(WRF)model wind speed forecasting coastal region

A Modified CycleGAN for Multi-Organ Ultrasound Image Enhancement via Unpaired Pre-Training

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Journal of Beijing Institute of Technology 2024年第3期33卷 194-203页

作者： Haonan Han Bingyu Yang weihang zhang Dongwei Li Huiqi Li School of Information and Electronics Beijing Institute of TechnologyBeijing 100081China School of Medical Technology Beijing Institute of TechnologyBeijing 100081China

Handheld ultrasound devices are known for their portability and affordability,making them widely utilized in underdeveloped areas and community healthcare for rapid diagnosis and early ***,the image quality of handheld ultrasound devices is not always satisfactory due to the limited equipment size,which hinders accurate diagnoses by *** the same time,paired ultrasound images are difficult to obtain from the clinic because imaging process is ***,we propose a modified cycle generative adversarial network(cycleGAN) for ultrasound image enhancement from multiple organs via unpaired *** introduce an ultrasound image pre-training method that does not require paired images,alleviating the requirement for large-scale paired *** also propose an enhanced block with different structures in the pre-training and fine-tuning phases,which can help achieve the goals of different training *** improve the robustness of the model,we add Gaussian noise to the training images as data *** approach is effective in obtaining the best quantitative evaluation results using a small number of parameters and less training costs to improve the quality of handheld ultrasound devices.

关键词： ultrasound image enhancement handheld devices unpaired images pre-train and finetune cycleGAN

即刻种植与延期种植在牙齿外伤修复患者中的应用效果比较

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中国民康医学 2024年第13期36卷 152-154,158页

作者：张玮航郑州人民医院口腔科(东) 河南郑州450000

目的:比较即刻种植与延期种植在牙齿外伤修复患者中的应用效果。方法:选取2022年1月至2023年1月于该院接受种植治疗的179例牙齿外伤患者进行前瞻性研究,按随机数字表法将其分为研究组(n=89)和对照组(n=90)。研究组实施即刻种植,对照组... 详细信息

目的:比较即刻种植与延期种植在牙齿外伤修复患者中的应用效果。方法:选取2022年1月至2023年1月于该院接受种植治疗的179例牙齿外伤患者进行前瞻性研究,按随机数字表法将其分为研究组(n=89)和对照组(n=90)。研究组实施即刻种植,对照组实施延期种植,比较两组种植体稳定程度[种植体稳定系数(ISQ)]、治疗周期、修复前后牙周相关指标[探诊深度(PD)、菌斑指数(PLI)、龈沟出血指标(SBI)]水平、美观度[红色美学指数(PES)、白色美学指数(WES)]评分和临床疗效。结果:两组ISQ评分比较,差异无统计学意义(P>0.05);研究组治疗周期短于对照组,差异有统计学意义(P0.05)。结论:即刻种植应用于牙齿外伤修复患者中可提高美观度评分,缩短治疗周期,降低牙周指标水平,其效果优于延期种植。

关键词：即刻种植延期种植牙齿外伤修复种植体稳定性牙周指标美观度

基于光化学指示剂法研究华北平原臭氧生成敏感性及气象因素影响:以2021年为例

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环境科学研究 2024年第3期37卷 479-492页

作者：刘冬晖海尚飞张玮航高阳周杨赵园红荆琦刘晓瑜盛立芳中国海洋大学海洋与大气学院山东青岛266100 中国气象局地球系统数值预报中心北京100081 中国海洋大学海洋环境科学与生态教育部重点实验室深海圈层与地球系统前沿科学中心山东青岛266100

近年来,随着大气污染防治措施的实施,我国城市地区空气质量得到有效改善,以细颗粒物(PM_(2.5))为代表的污染物年均浓度持续下降,但是臭氧污染并没有得到很好的控制.明确臭氧生成敏感性变化规律及气象影响因子是制定有效臭氧污染控制策... 详细信息

近年来,随着大气污染防治措施的实施,我国城市地区空气质量得到有效改善,以细颗粒物(PM_(2.5))为代表的污染物年均浓度持续下降,但是臭氧污染并没有得到很好的控制.明确臭氧生成敏感性变化规律及气象影响因子是制定有效臭氧污染控制策略的基础.本研究利用WRF-Chem模式数据计算VOCs/NO_(x)、HCHO/NO_(2)和H_(2)O_(2)/HNO_(3)(均为质量浓度的比值)三类光化学指示剂,对华北平原2021年4−9月的臭氧生成敏感性(OFS)控制区进行划分,并探讨不同天气状况下影响OFS的关键气象因子.结果表明:华北平原OFS控制区变化存在地域与季节性差异.人为活动水平越高的区域,OFS受挥发性有机物(VOCs)的影响越大,唐山市−北京市−天津市、石家庄市−邢台市、潍坊市−淄博市−济南市等地带臭氧生成主要处于VOCs控制;华北平原的VOCs控制区面积在4−7月间缩小,在7−9月间扩大,其中7月VOCs的控制区范围最小.此外,在华北平原地区,阴雨天相较晴天更利于发生OFS的日变化.晴天时,高温是OFS变化的关键因素;阴天时,高温高湿是引起臭氧敏感性转变的关键;而雨天,高湿条件发挥了更为重要的作用,但当雨量较大时,反而会抑制OFS发生转变.研究显示,华北平原的OFS与VOCs浓度密切关联,在不同天气下,气象因子通过影响VOCs浓度进而影响OFS.因而,针对不同天气状况实施差异化的前体物减排策略是有效控制臭氧污染的关键.

关键词：臭氧生成敏感性控制区气象因子 WRF-Chem 光化学指示剂

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Influence of rainfall-induced diabatic heating on southern rainfall-northern haze over eastern China in early February 2023

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Science China Earth Sciences 2023年第11期66卷 2579-2593页

作者： Xiadong AN Wen CHEN Chun LI Lifang SHENG weihang zhang Shangfei HAI Peng HU Department of Marine Meteorology College of Oceanic and Atmospheric SciencesOcean University of ChinaQingdao 266100China Department of Atmospheric Sciences Yunnan UniversityKunming 650500China Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion Yunnan UniversityKunming 650091China Center for Monsoon System Research Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100190China CMA Earth System Modeling and Prediction Center China Meteorological AdministrationBeijing 100081China

In early February 2023,there was severe haze on the North China Plain(NCP)that was contemporaneous with heavy rainfall over southern China,which was known as southern rainfall-northern haze(SR-NH).Based on observational and reanalysis data,the meteorological causes of this SR-NH event are investigated in this study using correlation analysis,dynamic diagnostics and numerical *** results show that the anticyclonic anomaly in the Pacific Northwest(also referred to as the northeast Asian anomalous anticyclone)is responsible for the *** the one hand,this anticyclonic anomaly leads to persistent rainfall over southern China by causing strong ascending motion in conjunction with an anomalous cyclone over the Chinese mainland and transporting large amounts of water vapor *** the other hand,it weakens the climatological northerly winds of the NCP through the southeasterly flow,worsening the horizontal diffusion conditions of ***,the atmospheric stability and relative humidity over the NCP are significantly increased by this anticyclonic *** conditions result in higher PM2.5concentrations over the *** results suggest that this anticyclonic anomaly is related to diabatic heating released by rainfall in southern China,which not only intensifies the rainfall process there(with a contribution of 11.5%)but also induces an anticyclonic anomaly in the upper troposphere of the Pacific Northwest(i.e.,200 hPa).The rainfall-related anticyclonic anomaly reinforces the anticyclonic anomaly in the Pacific Northwest caused by large-scale circulation(with a contribution of 27%)and thus affects haze over the *** study provides a new reference for understanding the contribution of rainfall in southern China to haze over the NCP.

关键词： Rainfall Haze Diabatic heating Anticyclonic anomaly Eastern China

2.29-kV GaN-based double-channel Schottky barrier diodes on Si substrates with high VON uniformity

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Science China(Information Sciences) 2023年第6期66卷 309-310页

作者： Ren HUANG weihang zhang Jincheng zhang Chunxu SU Xi LIU Liyu FU Yue HAO Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University Wide Bandgap Semiconductor Innovation Center of Guangzhou Guangzhou Institute of TechnologyXidian University

The GaN on Si technology is attractive for power electronic systems owing to its low cost and large wafer size [1]. GaN Schottky barrier diodes(SBDs) on Si substrates have been extensively studied due to their superio...

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High-breakdown-voltage (>3000 V) and low-power-dissipation Al0.3Ga0.7N/GaN/Al0.1Ga0.9N double-heterostructure HEMTs with Ohmic/Schottky hybrid drains and Al2O3/SiO2 passivation

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Science China(Information Sciences) 2023年第12期66卷 297-298页

作者： Yutong FAN Xi LIU Ren HUANG Yu WEN weihang zhang Jincheng zhang Zhihong LIU Shenglei ZHAO Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices School of MicroelectronicsXidian University Guangzhou Wide Bandgap Semiconductor Innovation Center Guangzhou Institute of TechnologyXidian University

GaN power devices have broad application prospects in fast charging systems, power supplies, data centers, and electric vehicles due to their high critical breakdown field strength, high switching frequency, and high conversion efficiency [1–3]. AlGaN/GaN/AlGaN double-heterostructure(DH) high-electron-mobility transistors(HEMTs) have been extensively studied owing to their low leakage current and low off-state power dissipation.

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Investigation of heavy ion irradiation effects on 650-V p-GaN normally-off HEMTs

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Science China(Information Sciences) 2022年第8期65卷 254-260页

作者： Yinhe WU Jincheng zhang Shenglei ZHAO Zhaoxi WU Zhongxu WANG Bo MEI Chao DUAN Dujun ZHAO weihang zhang Zhihong LIU Yue HAO Key Laboratory of Wide Band-Gap Semiconductors and Devices School of MicroelectronicsXidian University China Aerospace Components Engineering Center

In this study, we investigate heavy ion irradiation effects on commercial 650 V p-GaN normallyoff HEMTs. Ge and Cl ions are used to irradiate the GaN devices in the experiments. Ge and Cl ion beam irradiation have little impact on the output characteristics of GaN devices. After heavy ion irradiation, the leakage currents between source and drain electrodes increase significantly under off-state, decreasing the breakdown voltage(BVDS) sharply. Additionally, Ge and Cl ion irradiation have little effect on the trap states under the gate electrode; thus, the gate leakage currents increase slightly. Many line-shaped crystal defects extending from the surface to the GaN buffer layer can be captured using a transmission electron microscope after Ge/Cl ion irradiation. The buffer layers of the irradiated devices were damaged, and the leakage path was generated in the buffer layer. Defect percolation process in buffer layer is the dominant factor of irradiated high-voltage GaN device failure.

关键词： heavy ions irradiation p-GaN normally-off HEMTs line-shaped crystal defects leakage path defect percolation process

Cyclic Beam Direction of Arrival Estimation Method for Ship Propeller Noise

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JOURNAL OF OCEAN UNIVERSITY OF CHINA 2024年第4期23卷 883-896页

作者： zhang, Xiaowei Nie, weihang Xu, Ji Yan, Yonghong Chinese Acad Sci Key Lab Speech Acoust & Content Understanding Inst Acoust Beijing 100190 Peoples R China Univ Chinese Acad Sci Inst Acoust Key Lab Speech Acoust & Content Understanding Beijing 100049 Peoples R China Chinese Acad Sci State Key Lab Acoust Inst Acoust Beijing 100190 Peoples R China

In underwater acoustic applications, the conventional cyclic direction of arrival algorithm faces challenges, including a low signal-to-noise ratio and high bandwidth when compared with modulated frequencies. In response to these issues, this paper introduces a novel, robust, and broadband cyclic beamforming algorithm. The proposed method substitutes the conventional cyclic covariance matrix with the variance of the cyclic covariance matrix as its primary feature. Assuming that the same frequency band shares a common steering vector, the new algorithm achieves superior detection performance for targets with specific modulation frequencies while suppressing interference signals and background noise. Experimental results demonstrate a significant enhancement in the directibity index by 81% and 181% when compared with the traditional Capon beamforming algorithm and the traditional extended wideband spectral cyclic MUSIC (EWSCM) algorithm, respectively. Moreover, the proposed algorithm substantially reduces computational complexity to 1/40th of that of the EWSCM algorithm, employing frequency band statistical averaging and covariance matrix variance.

关键词： cyclostationarity direction of arrival extended wideband spectral cyclic music cyclic covariance matrix MUSIC CYCLOSTATIONARITY EXPLOITATION