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Adsorption of Th and Pa onto particles and the effect of organic compounds in natural seawater

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Journal of Oceanology and Limnology 2021年第6期39卷 2209-2219页

作者： Xinxing ZHANG weifeng yang Yusheng QIU Minfang ZHENG College of Ocean and Earth Sciences Xiamen UniversityXiamen 361102China North China Sea Environmental Monitoring Center State Oceanic AdministrationQingdao 266033China State Key Laboratory of Marine Environmental Science Xiamen 361102China

^(231)Pa and ^(230)Th are two crucial isotopes in the ongoing GEOTRACES ***,the controversy on ^(231)Pa/^(230)Th proxy pertaining to archiving ocean circulation or recording paleoproductivity,is still unresolved,partly owing to the unclear understanding of fractionation between ^(231)Pa and ^(230)Th during *** this study,controlled experiments were conducted to examine the adsorption of ^(234)Th and ^(233)Pa onto biogenic particles(SiO_(2) and CaCO_(3)),authigenic minerals(MnO_(2) and Fe_(2)O_(3)),and lithogenic minerals(kaolinite,attapulgite,montmorillonite,and aluminum oxyhydroxides),and the role of organic compounds in regulating the adsorption of ^(234)Th and ^(233)Pa in natural seawater was *** distribution coefficients(K d,presented as logK_(d))varied from 3.56 to 6.05 and from 3.27 to 5.82 for ^(234)Th and ^(233)Pa,***_(2)O_(3) is the strongest sorbent for both ^(234)Th and ^(233)*** of the particles showed comparable logK_(d) values for either ^(234)Th(~4.8)or ^(233)Pa(~3.9)in the presence of dextran,indicating that the adsorption of Th and Pa is likely controlled by organic coating on particle *** fractionation factors(F Th/Pa)of SiO_(2)(3±1)and CaCO_(3)(33±1)suggest in situ observed preferential scavenging of ^(230)Th to ^(231)Pa in the surface water of low-to mid-latitude regions and the nearly equal removal in the Antarctic Ocean where biogenic silica dominates the particle *** F Th/Pa values of the lithogenic and biogenic particles indicate that ^(230)Th is scavenged prior to ^(231)Pa in the particle-scarce ocean *** equal scavenging of ^(230)Th and ^(231)Pa at the ocean margins and the ridge crests is dominated by high particle fl uxes instead of particle composition *** results imply that ^(230)Th/^(231)Pa can be used as different proxies in different oceanic settings.

关键词： thorium protactinium paleoproductivity circulation particle dynamics

Utilizing ^(234)Th/^(238)U disequilibrium to constrain particle dynamics in hydrothermal plumes in the Southwest Indian Ocean

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Acta Oceanologica Sinica 2021年第6期40卷 16-25页

作者： weifeng yang Xinxing Zhang Min Chen Ziming Fang Yusheng Qiu State Key Laboratory of Marine Environmental Science Xiamen UniversityXiamen 361102China College of Ocean and Earth Sciences Xiamen UniversityXiamen 361102China North China Sea Environmental Monitoring Center State Oceanic AdministrationQingdao 266033China Department of Ocean Science Hong Kong University of Science and TechnologyHong Kong 999077China

Metal-enriched minerals have been widely observed near hydrothermal vent ***,the dynamics of particulate metals influenced by hydrothermal activities is poorly ***,radioactive 234Th in both dissolved and particulate phases were used to examine the kinetics of particle-reactive metal adsorption,removal,and residence in a newly found hydrothermal plume over the Southwest Indian *** results showed a relatively low value on ^(234)Th/^(238)U ratios(i.e.,0.73-0.88)compared to the deep oceans,indicating an enhanced adsorption of particle-reactive metals onto particulate matter in the *** on the 234Th-238U disequilibria,the adsorption and sinking rate constants of 234Th averaged(0.009±0.001)d^(-1) and(0.113±0.024)d^(-1) in the hydrothermal plume,corresponding to the residence times of(115±19)d and(16±5)d for dissolved and particulate 234Th,*** timescale allows vent-discharged particle-reactive metals to disperse hundreds to thousands of miles ***,hydrothermal activities might influence the metal distribution in deep ocean over a very large ***,a high sinking flux of(36.2±5.4)B q/(m^(2)·d)for 234Th was observed for the plume,suggesting an enrichment of metal in particles deposited close to the *** enhancement of particle sinking could also benefit the transport of organic carbon and nitrogen and fuel the benthic ecosystems under the plume ***,hydrothermal plumes may have an impact on both the elemental geochemistry and/or ecosystem to the deep oceans interior than previous expectation.

关键词： thorium-234 particle dynamics hydrothermal plume Indian Ocean

The GNSS PWV retrieval using non-observation meteorological parameters based on ERA5 and its relation with precipitation

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Geodesy and Geodynamics 2024年第3期15卷 302-313页

作者： weifeng yang Zhiping Chen Kaiyun Lv Pengfei Xia Tieding Lu School of Surveying and Geoinformation Engineering East China University of TechnologyNanchang 330013China Key Laboratory of Mine Environmental Monitoring and Improving around Poyang Lake of Ministry of Natural Resources East China University of TechnologyNanchang 330013China State Key Laboratory of Geodesy and Earth's Dynamics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430077China Jiangxi Province Engineering Research Center of Surveying Mapping and Geographic InformationNanchang 330025China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China

The pressure and temperature significantly influence precipitable water vapor(PWV) retrieval. Global Navigation Satellite System(GNSS) PWV retrieval is limited because the GNSS stations lack meteorological sensors. First, this article evaluated the accuracy of pressure and temperature in 68 radiosonde stations in China based on ERA5 Reanalysis data from 2015 to 2019 and compared them with GPT3model. Then, the accuracy of pressure and temperature calculated by ERA5 were estimated in 5 representative IGS stations in China. And the PWV calculated by these meteorological parameters from ERA5(ERA5-PWV) were analyzed. Finally, the relation between ERA5-PWV and precipitation was deeply explored using wavelet coherence analysis in IGS stations. These results indicate that the accuracy of pressure and temperature of ERA5 is better than the GPT3 model. In radiosonde stations, the mean BIAS and MAE of pressure and temperature in ERA5 are-0.41/1.15 hpa and-0.97/2.12 K. And the mean RMSEs are 1.35 hpa and 2.87 K, which improve 74.77% and 40.58% compared with GPT3 model. The errors of pressure and temperature of ERA5 are smaller than the GPT3 model in bjfs, hksl and wuh2, and the accuracy of ERA5-PWV is improved by 18.77% compared with the GPT3 model. In addition, there is a significant positive correlation between ERA5-PWV and precipitation. And precipitation is always associated with the sharp rise of ERA5-PWV, which provides important references for rainfall prediction.

关键词： ERA5 GNSS Precipitable water vapor Precipitation Wavelet coherence analysis

Excess polonium-210 in the coastal atmosphere originating from marine biogenic material

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Acta Oceanologica Sinica 2006年第6期25卷 78-87页

作者： yang weifeng CHEN Min HUANG Yipu LIU Guangshan JIA Chengxia Department of Oceanography Xiamen University Xiamen 361005 China State Key Laboratory of Marine Environmental Science Xiamen University Xiamen 361005 China

The depositional fluxes of atmospheric polonium-210 were measured at one site in Xiamen from August 2001 to March 2002. With predominant marine air mass, the depositional fluxes of atmospheric polonium-210 ranged from 0.01 to 0.09 Bq/（m^2· d）, with an average of 0.04 Bq/（m^2 · d）. The seasonal pattern showed elevated polonium-210 fluxes in summer and autumn rather than in winter. Atmospheric depositional fluxes of polonium-210 showed a good correlation with beryllium-7 （r^2 =0. 85） and lead-210 fluxes （r^2 =0.71 ）, indicating their similar removal mechanism from atmosphere. The relationship between the polonium-210 depositional fluxes and the precipitation amount demonstrated that the precipitation dominates the polonium-210 removal from the atmosphere. The observed high activity ratios of polonium-210 to lead-210 indicated the occurrence of excess polonium-210 in coastal atmosphere, which may originate from marine surface waters either by indirect （foam）, or mare likely, direct （ air - sea exchange） input of marine bingenic material into the atmosphere. This source is even more important than the in situ decay of lead-210.

关键词： excess polonium-210 depositional flux coastal atmosphere precipitation

Interfacial properties of 2D WS_(2)on SiO_(2)substrate from X-ray photoelectron spectroscopy and firstprinciples calculations

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Frontiers of physics 2022年第5期17卷 93-103页

作者： Changjie Zhou Huili Zhu weifeng yang Qiubao Lin Tongchang Zheng Lan yang Shuqiong Lan Xiamen Key Laboratory of Ultra-Wide Bandgap Semiconductor Materials and Devices Department of PhysicsSchool of ScienceJimei UniversityXiamen 361021China Department of Microelectronics and Integrated Circuits Xiamen UniversityXiamen 361005China

Two-dimensional(2D)WS_(2)films were deposited on SiO_(2)wafers,and the related interfacial properties were investigated by high-resolution X-ray photoelectron spectroscopy(XPS)and first-principles *** the direct(indirect)method,the valence band offset(VBO)at monolayer WS_(2)/SiO_(2)interface was found to be 3.97 eV(3.86 eV),and the conduction band offset(CBO)was 2.70 eV(2.81 eV).Furthermore,the VBO(CBO)at bulk WS_(2)/SiO_(2)interface is found to be about 0.48 eV(0.33 eV)larger due to the interlayer orbital coupling and splitting of valence and conduction band ***,the WS_(2)/SiO_(2)heterostructure has a Type I energy-band *** band offsets obtained experimentally and theoretically are consistent except the narrower theoretical bandgap of SiO_(2).The theoretical calculations further reveal a binding energy of 75 meV per S atom and the totally separated partial density of states,indicating a weak interaction and negligible Fermi level pinning effect between WS_(2)monolayer and SiO_(2)*** combined experimental and theoretical results provide proof of the sufficient VBOs and CBOs and weak interaction in 2D WS_(2)/SiO_(2)heterostructures.

关键词： band offsets WS_(2) SiO_(2) X-ray photoelectron spectroscopy first-principles calculations

High responsivity 4H-SiC based metal-semiconductor-metal ultraviolet photodetectors

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Science China(Physics,Mechanics & Astronomy) 2008年第11期51卷 1616-1620页

作者： yang weifeng ZHANG Feng LIU ZhuGuang LüYing WU ZhengYun Department of Physics Xiamen UniversityXiamen 361005China MEMS Research Center Xiamen UniversityXiamen 361005China

4H-SiC based metal-semiconductor-metal (MSM) photodetectors with diverse spacing were designed, fabricated, and characterized, in which nickel Schottky contacts were needed. Current-voltage and spectral responsivity measurements were carried out at room temperature. The fabricated 4 μm-spacing device showed a very low dark current (0.25 pA at 5 V bias voltage), a typical responsivity of 0.103 A/W at 20 V, and a peak re-sponse wavelength at 290 nm. The fabricated devices held a high DUV to visible re-jection ratio of >103.

关键词： 4H-SiC MSM UV photodetector responsivity

Condition monitoring and fault diagnosis strategy of railway point machines using vibration signals

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Transportation Safety and Environment 2023年第2期5卷 27-37页

作者： Yongkui Sun Yuan Cao Haitao Liu weifeng yang Shuai Su National Engineering Research Center of Rail Transportation Operation and Control System Beijing Jiaotong UniversityBeijing 100044China CRRC Zhuzhou Institute Co Ltd Zhuzhou 412001HunanChina Frontiers Science Center for Smart High-speed Railway System Beijing Jiaotong UniversityBeijing 100044China

Condition monitoring of railway point machines is important for train operation safety and *** to the fields of mechanical equipment fault detection,this paper proposes a fault detection and identification strategy of railway point machines via vibration signals.A comprehensive feature distilling approach by combining variational mode decomposition(VMD)energy entropy and time-and frequency-domain statistical features is presented,which is more effective than single type of *** optimal set of features was selected with ReliefF,which helps improve the diagnosis *** vector machine(SVM),which is suitable for a small sample,is adopted to realize *** diagnosis accuracy of the proposed method reaches 100%,and its effectiveness is verified by experiment *** this paper,vibration signals are creatively adopted for fault diagnosis of railway point *** presented method can help guide field maintenance staff and also provide reference for fault diagnosis of other equipment.

关键词： railway point machines condition monitoring variational mode decomposition(VMD)energy entropy statistical features

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Low ^(210)Pb in the upper thermocline in the Canadian Basin: scavenge process over the Chukchi Sea

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Acta Oceanologica Sinica 2014年第6期33卷 28-39页

作者： HU Wangjiang CHEN Min yang weifeng ZHANG Run QIU Yusheng ZHENG Minfang College of Ocean and Earth Sciences Xiamen University State Key Laboratory of Marine Environmental Science Xiamen University

210pb was measured during the 3rd Chinese National Arctic Research Expedition cruise to investigate its spa- tial pattern in the western Arctic Ocean, as well as its relation with the thermocline in the Canadian Basin. The specific activities varied from 0.04 to 2.72, 〈0.013 to 4.37, and 0.1 to 4.85 Bq/m3 for dissolved, particu- late, and bulk 210pb, respectively, corresponding to respective averages of 0.65, 0.43, and 1.08 Bq/m3. In the Canadian Basin, the minimum 210pb activities occurred in the thermocline, which was characterized by low temperature of-1.52℃ and salinity of 33.1. Combining the spatial distribution of 210pb and hydrographical characteristics in the western Arctic Ocean, this scenario was ascribed to the effective scavenging of 210pb when the Pacific water flowed across the Chukchi Shelf. Quantitatively, this interpretation was supported by both the shorter residence times and higher scavenging efficiencies （SE） of dissolved 210pb over the Chukchi Shelf. The highest SE values were observed in the Herald Shoal and bottom waters over the slope.

关键词： 210Pb halocline Canadian Basin Chukchi Sea

Energy band alignment of 2D/3D MoS_(2)/4H-SiC heterostructure modulated by multiple interfacial interactions

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Frontiers of physics 2023年第1期18卷 153-164页

作者： Huili Zhu Zifan Hong Changjie Zhou Qihui Wu Tongchang Zheng Lan yang Shuqiong Lan weifeng yang Xiamen Key Laboratory of Ultra-Wide Bandgap Semiconductor Materials and Devices Department of PhysicsSchool of ScienceJimei UniversityXiamen 361021China Department of Microelectronics and Integrated Circuit School of Electronic Science and Engineering(National Model Microelectronics College)Xiamen UniversityXiamen 361005China School of Marine Equipment and Mechanical Engineering Jimei UniversityXiamen 361021China

The interfacial properties of MoS_(2)/4H-SiC heterostructures were studied by combining first-principles calculations and X-ray photoelectron ***(theoretical)valence band offsets(VBOs)increase from 1.49(1.46)to 2.19(2.36)eV with increasing MoS_(2) monolayer(1L)up to 4 layers(4L).A strong interlayer interaction was revealed at 1L MoS_(2)/SiC *** level pinning and totally surface passivation were realized for 4H-SiC(0001)*** 0.96e per unit cell transferring forms an electric field from SiC to MoS_(2).Then,1L MoS_(2)/SiC interface exhibits type I band alignment with the asymmetric conduction band offset(CBO)and *** 2L and 4L MoS_(2)/SiC,Fermi level was just pinning at the lower MoS_(2)*** interaction keeps weak vdW interaction between upper and lower MoS_(2) *** exhibit the type II band alignments and the enlarged CBOs and VBOs,which is attributed to weak vdW interaction and strong interlayer orbital coupling in the multilayer MoS_(2).High efficiency of charge separation will emerge due to the asymmetric band alignment and built-in electric field for all the MoS_(2)/SiC *** multiple interfacial interactions provide a new modulated perspective for the next-generation electronics and optoelectronics based on the 2D/3D semiconductors heterojunctions.

关键词： MoS_(2) SiC X-ray photoelectron spectroscopy band alignment first-principles calculations