A study on temperature monitoring method for inverter IGBT based on memory recurrent neural network

The power module of the Insulated Gate Bipolar Transistor(IGBT)is the core component of the traction transmission system of high-speed trains.The module's junction temperature is a critical factor in determining device reliability.Existing temperature monitoring methods based on the electro-thermal coupling model have limitations,such as ignoring device interactions and high computational complexity.To address these issues,an analysis of the parameters influencing IGBT failure is conducted,and a temperature monitoring method based on the Macro-Micro Attention Long Short-Term Memory(MMALSTM)recursive neural network is proposed,which takes the forward voltage drop and collector current as features.Compared with the traditional electricalthermal coupling model method,it requires fewer monitoring parameters and eliminates the complex loss calculation and equivalent thermal resistance network establishment process.The simulation model of a highspeed train traction system has been established to explore the accuracy and efficiency of MMALSTM-based prediction methods for IGBT power module junction temperature.The simulation outcomes,which deviate only 3.2% from the theoretical calculation results of the electric-thermal coupling model,confirm the reliability of this approach for predicting the temperature of IGBT power modules.

Study of coexisting upstream solitary wave packet and downstream wakes induced by Diaoyu Dao and its affiliated islands detected by satellite sun glitter

Taking the advantage of sun glitter(SG)observed from high-resolution satellites Gaofen-1(GF-1)and Gaofen-6(GF-6),a new method named Shield and Vortex 1-2(SAV1-2)for extracting spatial texture information from sun glitter was established.Sea surface texture detail information around Diaoyu Dao and its affiliated islands was extracted using SAV1-2.Meanwhile,the dynamic characteristics of the water environment were analyzed by combining the water color,temperature and dynamic data.The results show the following information.(1)Stable westward shield effect and eastward Karman vortex streets,extracted from SG,appear upstream(westward)and downstream(eastward)of the Diaoyu Dao and its affiliated islands respectively.(2)The dominant direction of the Kuroshio Current in the Diaoyu Dao and its affiliated islands area is east,the Diaoyu Dao and its affiliated islands interacting with Kuroshio,inducing western shield and eastern shelter and wake.Furthermore,wave intervals of the shield in front of the island range from hundreds to thousands of metres,and extend wider than the island itself.(3)Combining with high-resolution sea surface temperature(SST)and chlorophyll a(Chl a)concentration,the directional changes of water color elements are mutually supported and proved with the stable shield(wave packet)effect in the west and vortex street effect in the east.The change of SST upstream of the island(western shield area)is not significant,the temperature in the downstream shelter area decreases slightly,and the SST in the downstream wake area shows a general trend of obvious decrease.The wake area is dominated by Karman vortex streets in shape,supplementing by vortices.The concentration of Chl a in the west shield of island is as low as that in downstream shelter area,while it increases significantly in the downstream wake area with shape in eddy or ribbon.(4)The SAV methods of extracting sea surface texture detail using SG can be widely used in different sea areas and water quality.This paper can provide reference for the protection and development of Diaoyu Dao and its affiliated islands and its surrounding waters.It is suggested that some kind of current buffer,such as marine wind farm,should be established in the western waters of Diaoyu Dao and its affiliated islands to protect the islands,and marine pasture should be developed in the downstream of eastern waters of Diaoyu Dao and its affiliated islands.

China-France Oceanography Satellite (CFOSAT) simultaneously observes the typhoon-induced wind and wave fields

The China-France oceanography satellite(CFOSAT)developed by the China National Space Administration(CNSA)and Centre National D’Etudes Spatiales(CNES)was successfully launched into its orbit on October 29,2018.The Chinese wind scatterometer(SCAT)with swath width of about 1000 km and French wave spectrometer(Surface Wave Investigation and Monitoring,SWIM)with swath width of about 180 km onboard the CFOSAT are in line with all requirements and performing operationally.Thus,it is the first time that CFOSAT provides simultaneous and co-located observations of wind and wave fields with high spatial resolutions of 12.5 km×12.5 km for the winds and 70 km×90 km for the wave directional spectrum.The real-time and large-scale monitoring of wind and wave fields are of great significance for navigation and human activities on the sea(Xu et al.,2010;Tan et al.,2018;Sun et al.,2019),especially during severe typhoon processes when violent winds and hazardous waves occur(Walsh et al.,2002;Zhou et al.,2008).

Localization Algorithm of Indoor Wi-Fi Access Points Based on Signal Strength Relative Relationship and Region Division

Precise localization techniques for indoor Wi-Fi access points(APs)have important application in the security inspection.However,due to the interference of environment factors such as multipath propagation and NLOS(Non-Line-of-Sight),the existing methods for localization indoor Wi-Fi access points based on RSS ranging tend to have lower accuracy as the RSS(Received Signal Strength)is difficult to accurately measure.Therefore,the localization algorithm of indoor Wi-Fi access points based on the signal strength relative relationship and region division is proposed in this paper.The algorithm hierarchically divide the room where the target Wi-Fi AP is located,on the region division line,a modified signal collection device is used to measure RSS in two directions of each reference point.All RSS values are compared and the region where the RSS value has the relative largest signal strength is located as next candidate region.The location coordinate of the target Wi-Fi AP is obtained when the localization region of the target Wi-Fi AP is successively approximated until the candidate region is smaller than the accuracy threshold.There are 360 experiments carried out in this paper with 8 types of Wi-Fi APs including fixed APs and portable APs.The experimental results show that the average localization error of the proposed localization algorithm is 0.30 meters,and the minimum localization error is 0.16 meters,which is significantly higher than the localization accuracy of the existing typical indoor Wi-Fi access point localization methods.

HY-1C Coastal Zone Imager observations of the suspended sediment content distribution details in the sea area near Hong Kong-Zhuhai-Macao Bridge in China

The impacts of the Hong Kong-Zhuhai-Macao Bridge(HKZMB)on suspended sediment content(SSC)were analysed in the Zhujiang River Estuary based on data from HY-1C,which was launched in September 2018 in China,carrying Coastal Zone Imager(CZI)and Chinese Ocean Color and Temperature Scanner on it.A new SSC inversion model was established based on the relationship between in-situ SSC and the remote sensing reflectance in red and near-infrared bands of CZI image.HY-1C satellite data obtained from October to December 2019 were applied to retrieve SSC in the Zhujiang River Estuary.The results show that SSC around the HKZMB is ranging from 20 mg/L to 95 mg/L.SSC change obviously on two sides of the bridge.During flooding and ebbing period,SSC increases obviously downstream of the bridge.SSC difference between upstream and downstream is ranging from 5 mg/L to 20 mg/L.Currents flowing across the HKZMB,the change trend of SSC in most places upstream and downstream is almost the same that SSC downstream of the bridge is higher than SSC upstream.The tidal currents interact with bridge piers,inducing vortexes downstream,leading the sediment to re-suspend downstream of the bridge piers.Other factors,including seafloor topography and wind,can also contribute to the distribution of SSC in the Zhujiang River Estuary.

Pressureless reactive sintering mechanism of nanocrystalline Bi_2O_3-Y_2O_3 solid electrolyte

The nanocrystalline Bi2O3-Y2O3 solid electrolyte material was synthesized by pressureless reactive sintering process with Bi2O3 and Y2O3 nano mixed powder as raw materials, which was prepared by a chemical coprecipitation process. The study on the behavior of nano δ-Bi2O3 formation and its grain growth showed that the solid solution reaction of Y2O3 and δ-Bi2O3 to form δ-Bi2O3 occurs mainly in the initial stage of sintering process, and nano δ-Bi2O3 crystal grains grow approximately following the rule of paracurve （（D-D0）^2=K.t） during sintering process. After sintered at 600℃ for 2 h, the samples could reach above 96% in relative density and have dense microstructure with few remaining pores, the δ-Bi2O3 grains are less than 100 nm in size.

Theory and practice of hull dynamic deformation law and heading angle transfer error correction

In order to meet the demand of high-precision heading angle transmission in the transfer alignment of inertial navigation system on moving base,the analytical function relationship between the hull deforma-tion and the turning angular velocity and angular acceleration was derived by using the classical beam theory based on the analysis of the equivalent load exerted by the hydrodynamic force and inertia force on the hull structure during the turning process under the combined action of the steering rudder mo-ment and wave force.The objective law between the angular motion and the azimuth deformation angle of the hull under the combined action of maneuvering and sea waves was revealed.Finally,the correc-tion coefficients were determined according to the left turn and right turn motions of the hull by using the measured data of the ship in the sea trial during the S-shape maneuvering navigation,and the az-imuth deformation angle correction was completed.The results indicated that the application of the Qu’s bending deformation correction formula could greatly reduce the influence of the hull flexural deforma-tion on the heading angle accuracy,meet the needs of high-precision heading angle transmission,and fully verify the correctness of the hull azimuth deformation law and the heading angle transmission er-ror correction theory.This theory and method provided technical support for establishing high-precision distributed digital reference in the field of transfer alignment of inertial navigation on moving base and the application of heading angle transfer of other shipborne equipment.

高功率连续绿光激光器的研究进展

近年来,高功率绿光激光器的快速发展引起了国内外学者的广泛关注,已经逐步应用于工业加工、3C电子行业、医疗、军事国防等领域.本文首先对高功率绿光激光相比于近红外激光的优势和主要的应用场景进行介绍,然后对二极管泵浦全固态、半导体、碟片和窄线宽光纤倍频四种类型的高功率连续绿光激光器的国内外发展现状进行总结.其中,光纤激光器具有电光效率高、体积小、光束质量好、成本较低和散热好等特点,并且单通倍频的方案具有结构简单、易于调节安装等优势.将高功率窄线宽光纤激光器和单通倍频方案结合,是实现高功率高亮度小型化绿光激光输出的理想技术方案.然后,主要分析了当前高功率窄线宽绿光光纤激光器的关键技术、发展趋势和面临的主要挑战.最后,介绍了该类型激光器在焊接工艺中的应用,并对未来的发展进行了展望.

Continuous variable quantum key distribution with a shared partially characterized entangled source

Locking the sophisticated and expensive entanglement sources at the shared relay node is a promising choice for building a star-type quantum network with efficient use of quantum resources,where the involved parties only need to equip low-cost and simple homodyne detectors.Here,to our best knowledge,we demonstrate the first experimental continuous variable quantum key distribution with an entanglement source between the two users.We consider a practical partially characterized entangled source and establish the security analysis model of the protocol under realistic conditions.By applying a biased base technology,the higher key rate than that of the original protocol is achieved.The experimental results demonstrate that the distance between two users can reach up to 60 km over telecom single-mode fiber,implying the feasibility for high-rate and secure communication with a shared entangled source at metropolitan distances.

Seasonal variations in wave-induced stress over global ocean based on China France Oceanography Satellite

Due to the scarcity of simultaneous observations on global-scale wind and wave spectra,there has been limited research on the characteristics of global wave-induced stress and wind stress with wave effects using observed wave spectra,particularly their seasonal variations.The China France Oceanography Satellite(CFOSAT)for the first time can simultaneously observe global sea surface wind and wave spectra,providing a solid data basis for investigating this difficult issue.In this study,the seasonal characteristics of global sea surface wave-induced stress and wind stress were analyzed by combining one-year simultaneous wind and wave observations from CFOSAT with a wave boundary layer model.Waveinduced stress was divided into wind-wave-induced stress and swell-induced stress based on different wave forms.The results showed that the wave-induced stress presented a significant inverse correlation with swell index.A higher swell index corresponded to a larger proportion of swell-induced stress,resulting in a decrease in wind stress,and vice versa,wind-wave-induced stress was dominant,resulting in an increase in wind stress.From spring to winter in the Northern Hemisphere(NH),wind-wave-induced stress predominated in the westerly belt of the Southern Hemisphere(SH),while swell-induced stress predominated near the equator.Further analysis revealed that the seasonal variation in wind-waveinduced stress in the SH was not significant,however,wind-wave-induced stress during the boreal summer was significantly lower than that in other seasons.The absolute value of swell-induced stress in the SH showed a trend of decrease and then increase from spring to winter.The percentage of increase or decrease in wind stress after considering the waveinduced stress showed a roughly symmetrical pattern between the NH and SH during the spring and autumn seasons,while the summer and winter seasons showed an asymmetrical feature.Wave-induced stress significantly modulated wind stress,resulting in zonal mean variations by up to±30%.This finding further highlights the important modulation of surface waves on wind stress at the global scale.

Extracting energetic disorder in organic solar cells using percolation models

The energetic disorder𝜎describes the energy state distribution in organic semiconducting materials.In organic solar cells(OSCs),energetic disorder is an important parameter for evaluating the charge transport behavior,and it is strongly correlated with the device performance.Thus far,a widely used approach for extracting energetic disorder values in OSCs is the Gaussian disorder model(GDM),in which the disorder values can be extracted by fitting the slope of lnμ∼1-T2,where𝜇is the charge mobility and𝑇is the temperature.Herein,we demonstrate the potential of the percolation approach to evaluate the energetic disorder values in OSCs and compare them with the data obtained using the GDM approach.Two typical non-fullerene acceptor(NFA)-based bulk heterojunction(BHJ)films,with PTB7-Th:ITIC and PM6:Y6,were selected as the model systems.When the percolation models were adopted in the two BHJ films,the energetic disorder values extracted from the Grünewald/Thomas and Nenashev percolation models gave similar results for electron transport in the PTB7-Th:ITIC and PM6:Y6 BHJ films.This work successfully demonstrates the feasibility of microresistance analysis in BHJ systems and the application potential of the percolation model for extracting energetic disorders in OSCs.

中国东海“桑吉”轮溢油污染类型的光学遥感识别

溢油是海洋环境监测的重要对象之一.在海洋环境动力作用下,溢油会形成复杂多样的污染类型.准确识别、分类并定量估算不同类型的溢油污染,有助于溢油事件应用处理策略的制定与灾损评估.微波雷达与光学是海洋溢油遥感监测的主要手段,具有不同的技术优势与应用特点.近年来,海洋溢油光学遥感的理论与应用研究发展迅速,其对不同海面溢油污染类型的识别、分类与定量估算能力得到认可.针对2018年1月中国东海"桑吉"轮溢油事件,利用中国GF-3合成孔径雷达数据,实现"桑吉"轮疑似溢油的圈定.优选欧洲空间局Sentinel-2卫星的多光谱数据,开展无云覆盖区域"桑吉"溢油的光学遥感探测.基于溢油模拟实验的光谱响应特征分析,阐明了典型溢油污染的Sentinel-2卫星多光谱特征,进一步开展"桑吉"轮溢油污染类型的光学遥感识别与分类.结果表明,"桑吉"轮溢油在其扩散与风化过程中,形成了3种显著差异的溢油污染类型,即海面油膜、油包水状、水包油状乳化物.不仅与GF-3合成孔径雷达的疑似溢油监测结果互为验证,更实现了不同溢油污染类型的光学遥感识别与分类.最后,初步讨论了光学遥感与微波雷达的集成应用策略,通过优势互补,能有效提高海洋溢油的遥感监测水平,并为中国海洋水色业务卫星的应用提供借鉴.

中国海洋水色业务卫星揭示我国近海溢油污染状况

溢油是海洋环境监测的重点对象.光学遥感能为海洋溢油的精细化监测提供技术支持,实现不同溢油污染类型的识别分类与量化估算.开展海洋溢油光学遥感业务化应用,光学载荷不仅要有高空间分辨率、高信噪比、大辐射动态范围等技术特点,还要满足大幅宽、高时间分辨率等要求.中国自主研发的海洋水色业务卫星——海洋一号C/D(Haiyang-1C/D, HY-1C/D)卫星,搭载有适宜于溢油监测的海岸带成像仪(coastal zone imager, CZI),双星组网后能为中国近海环境监测提供3 d两次的观测数据,具备开展溢油业务化监测应用的能力.本研究基于HY-1C/D卫星CZI载荷近3年观测数据,利用研发的国产海洋水色业务卫星溢油监测算法,对中国近海及相关海域开展溢油光学遥感监测与分析. HY-1C/D卫星CZI数据能有效识别不同耀光反射条件下的非乳化油膜与乳化油等溢油污染类型,为溢油类型鉴别提供新的参考.研究结果阐明了中国近海溢油污染状况,近3年来共监测到溢油事件57次,渤海、黄海、南海是溢油发生的主要海域,部分地区近海环境监管压力较大. HY-1C/D卫星对中国近海溢油具有大范围、高频次、动态监测能力,能识别不同溢油污染类型及面积,有利于溢油污染类型判定与溢油量估算,提高了海洋溢油监测精度,为中国海洋环境监测提供可靠的卫星数据支持.

The HY-2 satellite and its preliminary assessment

The HY-2 satellite was successfully launched on 16 August 2011.It carried four microwave instruments into space for operationally observing dynamic ocean environment parameters on a global scale.The HY-2 satellite altimeter provides sea surface height(SSH),significant wave height(SWH),sea surface wind(SSW)speed,and polar ice sheet elevation,while the HY-2 satellite scatterometer provides SSW fields.At the same time,other oceanic and atmospheric parameters such as sea surface temperature(SST)and wind speed,water vapor and liquid water content can also be obtained by its onboard scanning microwave radiometer.In this paper,we show the data processing methods of the HY-2 satellite’s payloads.The preliminary results show that wind vector,SSH,SWH,and SST conform to the designed technical specifications.

用汉森溶解度参数评估功能化石墨烯在溶剂中的分散性

石墨烯独特的结构使其容易团聚,不溶于大多数的溶剂,应用受到极大限制。本工作用海藻酸钠(SA)和聚乙烯吡咯烷酮(PVP)表面改性石墨烯抑制石墨烯团聚,用扫描电子显微镜、傅里叶变换红外光谱、拉曼光谱和X射线衍射仪对其进行表征,考察了两种功能化石墨烯在溶剂中的分散性,并根据分散结果计算了汉森溶解度参数。结果表明,石墨烯成功功能化,经两种分散剂表面改性的石墨烯在溶剂中的分散性改变较大,在水中分散性较好,汉森溶解度参数和汉森球半径均发生改变。汉森球半径变大表明表面改性增大了石墨烯在溶剂中的溶解度。

Multi-time Scale Optimal Power Flow Strategy for Medium-voltage DC Power Grid Considering Different Operation Modes

Direct current(DC)power grids based on flexible high-voltage DC technology have become a common solution of facilitating the large-scale integration of distributed energy resources(DERs)and the construction of advanced urban power grids.In this study,a typical topology analysis is performed for an advanced urban medium-voltage DC(MVDC)distribution network with DERs,including wind,photovoltaic,and electrical energy storage elements.Then,a multi-time scale optimal power flow(OPF)strategy is proposed for the MVDC network in different operation modes,including utility grid-connected and off-grid operation modes.In the utility grid-connected operation mode,the day-ahead optimization objective minimizes both the DER power curtailment and the network power loss.In addition,in the off-grid operation mode,the day-ahead optimization objective prioritizes the satisfaction of loads,and the DER power curtailment and the network power loss are minimized.A dynamic weighting method is employed to transform the multi-objective optimization problem into a quadratically constrained quadratic programming(QCQP)problem,which is solvable via standard methods.During intraday scheduling,the optimization objective gives priority to ensure minimum deviation between the actual and predicted values of the state of charge of the battery,and then seeks to minimize the DER power curtailment and the network power loss.Model predictive control(MPC)is used to correct deviations according to the results of ultra short-term load forecasting.Furthermore,an improved particle swarm optimization(PSO)algorithm is applied for global intraday optimization,which effectively increases the convergence rate to obtain solutions.MATLAB simulation results indicate that the proposed optimization strategy is effective and efficient.

Coordinated Control Strategy for Operation Mode Switching of DC Distribution Networks

Due to the advantages such as low line cost,low transmission loss,and high power supply reliability,DC distribution networks have become the main development trend for future distribution networks.In this paper,a typical DC distribution network with multiple voltage levels is considered as a research object.It is proposed that the interface converters between DC buses with different voltage levels be implemented through the series-parallel combination of full-bridge LLC resonant converters.To realize the decentralized self-discipline control of DC voltage under various working conditions,different slack buses are prepared according to the voltage ranges of the DC buses,and the voltage regulation modes of the DC distribution network are divided into main voltage regulation mode,backup voltage regulation mode,and off-grid voltage droop regulation mode.By introducing a voltage coefficient related to DC voltage deviation as a basis for mode switching,the voltage fluctuations caused by slow switching between control modes in the method of traditional voltage margin control is reduced,facilitating fast and smooth switching between different voltage regulation modes.Finally,a simulation model for DC distribution networks is constructed utilizing MATLAB/Simulink.Simulation results verify the effectiveness and feasibility of the proposed voltage regulation modes and switching methods for DC distribution networks.Finally,an experimental platform is also constructed to verify the feasibility of the mode switching method proposed in this paper.

Melt-Lithosphere Interaction Controlled Compositional Variations in Mafic Dikes from Fujian Province,Southeastern China

Late Mesozoic magmatism in southeastern China has been widely considered to be related to the subduction of the Paleo-Pacific Plate.However,it remains controversial whether mafic rocks are derived from the lithosphere or the asthenosphere.Here we present a comprehensive study on mafic dikes from Fujian Province in southeastern China,aiming to understand their source.Two types of mafic rocks have been recognized based on their trace-element features.Type-Ⅰrocks show arc-like trace-elemental characteristics,while type-Ⅱrocks are distinguished by their relatively flat patterns in primitive-mantle-normalized trace-element diagram.Despite such differences between two types of rocks,these mafic dikes show two trends in the plots of^(87)Sr/^(86)Sr(i)versus La/Nb,which can be explained by the influences of crustal contamination and melt-lithospheric mantle interaction,respectively.^(87)Sr/^(86)Sr(i),La/Nb,Sr/Y and Zr/Y ratios of type-I rocks are significantly correlated to the thickness of the underlying lithosphere,and the signals of lithosphere are clearer with increasing lithospheric thickness.This highlights the important influences of melt-lithosphere interaction during their formation.Such observations also indicate that these mafic rocks are more likely to have been originated from the asthenosphere rather than the lithospheric mantle.

Atmospheric correction for HY-1C CZI images using neural network in western Pacific region

With a spatial resolution of 50 m,a revisit time of three days,and a swath of 950 km,the coastal zone imager(CZI)offers great potential in monitoring coastal zone dynamics.Accurate atmo-spheric correction(AC)is needed to exploit the potential of quantitative ocean color inversion.However,due to the band setting of CZI,the AC over coastal waters in the western Pacific region with complex optical properties cannot be realized easily.This research introduces a novel neural network(NN)AC algorithm for CZI data over coastal waters.Total 100,000 match-ups of HY-1 C CZI-observed reflectance at the top-of-atmosphere and Operational Land Imager(OLI)-retrieved high-quality remote sensing reflectance(Rrs)at the CZI bands are built to train the NN model.These reflectance data are obtained from the standard AC algorithm in the SeaDAS.Results indicate that the distributions of the CZI retrieved Rrs were consistent with the quasi-synchronous OLI data,but the spatial information from the CZI is more detailed.Then,the accuracy of the CZI data for AC is evaluated using the multi-source in-situ data.Results further show that the NN-AC can successfully retrieve Rrs for CZI and the coefficients of determination in the blue,green,red,and near-infrared bands were 0.70,0.77,0.76,and 0.67,respectively.The NN algorithm does not depend on shortwave-infrared bands and runs very fast once properly trained.

Integrated monitoring of lakes’ turbidity in Wuhan, China during the COVID-19 epidemic using multi-sensor satellite observations

During the COVID-19 epidemic in Wuhan,China,a series of measures were implemented by the government to prevent the spread of disease,including the lockdown policy and construction of emergency hospitals.To estimate the impact of these measures on aquatic environments,turbidity of lakes in Wuhan was dynamically monitored by integrating multi-sensor satellite observations.Calibrated against field measurements,empirical turbidity models were developed with high accuracy(R^(2)=0.77,RMSE=3.13 NTU).Time series of lake turbidity during COVID-19 were then retrieved,and possible factors for the turbidity change were discussed,including meteorological conditions and human activities.Results demonstrated that(1)the mean turbidity showed a 24.9%decline from 33.4 NTU to 25.1 NTU after the lockdown in Wuhan,which dropped 16.0%compared to that in the previous year.This decline might be related to the sharp reduction in human activities after the lockdown;(2)no obvious turbidity disturbance was observed in the lakes around emergency hospitals during their construction,and the lakes remained stable after the operation of hospitals.The method of integrating multi-sensor satellite observations used in this study shows great performance in term of temporal resolution for dynamic monitoring of inland water.