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Numerical simulation for 2D double-diffusive convection(DDC) in rectangular enclosures based on a High resolution upwind compact streamfunction model Ⅰ: numerical method and code validation

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Applied Mathematics and Mechanics(English Edition) 2022年第9期43卷 1431-1448页

作者： Yaping YAN Shuang WU Kaiyuan TIAN Zhenfu TIAN Institute of Mechanics and Computational Engineering Department of Aeronautics and AstronauticsFudan UniversityShanghai 200433China College of Science Liaoning Technical UniversityFuxin 123000Liaoning ProvinceChina Research Institute of Intelligent Complex Systems Fudan UniversityShanghai 200433China School of Life Sciences Fudan UniversityShanghai 200433China

A High resolution upwind compact streamfunction numerical algorithm for two-dimensional(2D)double-diffusive convection(DDC)is developed.The unsteady Navier-Stokes(N-S)equations in the streamfunction-velocity form and the scalar temperature and concentration equations are used.An optimized third-order upwind compact(UCD3 opt)scheme with a low dispersion error for the first derivatives is utilized to approximate the third derivatives of the streamfunction in the advection terms of the N-S equations and the first derivatives in the advection terms of the scalar temperature and concentration equations.The remaining first derivatives of the streamfunction(velocity),temperature,and concentration variables used in the governing equations are discretized by the fourth-order compact Pade(SCD4)schemes.With the temperature and concentration variables and their approximate values of the first derivatives obtained by the SCD4 schemes,the explicit fourth-order compact schemes are suggested to approximate the second derivatives of temperature and concentration in the diffusion terms of the energy and concentration equations.The discretization of the temporal term is executed with the second-order Crank-Nicolson(C-N)scheme.To assess the spatial behavior capability of the established numerical algorithm and verify the developed computer code,the DDC flow is numerically solved.The obtained results agree well with the benchmark solutions and some accurate results available in the literature,verifying the accuracy,effectiveness,and robustness of the provided algorithm.Finally,a preliminary application of the proposed method to the DDC is carried out.

关键词： double diffusive convection(DDC) High resolution heat and mass transfer upwind compact difference streamfunction formulation

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High resolution and high signal-to-noise ratio imaging with nearfield high-order optical signals

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Nano Research 2022年第9期15卷 8345-8350页

作者： Fei Wang Shuming Yang Shaobo Li Shuhao Zhao Biyao Cheng Chengsheng Xia State Key Laboratory for Manufacturing Systems Engineering International Joint Laboratory for Micro/Nano Manufacturing and Measurement TechnologiesXi’an Jiaotong UniversityXi’an 710049China School of Mechanical Engineering Xi’an Jiaotong UniversityXi’an 710049China

The properties of near-field optics have always been the focus of nano-measurement technology.The 11th order effective nearfield optical signal with an incident laser wavelength of 1,550 nm is obtained using a platinum-coated optical probe(Pt–Si probe).The experimental results show that the local electric field intensity of the Pt–Si probe is nearly 30 times higher than that of silicon probe(Si probe).Therefore,the highest 7th order near-field optical imaging results are obtained with the Pt–Si probe.Further,near-field optical imaging is performed on samples such as gold grids and carbon nanotubes using the Pt–Si probe.The measurement results show that the high-order signal has the characteristics of less background,higher signal-to-noise ratio,and resolution up to 5.7 nm.

关键词： high-order optical signal local electric field enhancement High resolution optical probe

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Data processing of the Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system and application to South China Sea data

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Journal of Oceanology and Limnology 2023年第2期41卷 644-659页

作者： Yanliang PEI Mingming WEN Zhengrong WEI Baohua LIU Kai LIU Guangming KAN Key Laboratory of Marine Geology and Metallogeny First Institute of OceanographyMinistry of Natural ResourcesQingdao 266061China Guangzhou Marine Geological Survey China Geological SurveyMinistry of Natural ResourcesGuangzhou 511458China College of Ocean Science and Engineering Shandong University of Science and TechnologyQingdao 266590China Laoshan Laboratory Qingdao 266237Chin

The Kuiyang-ST2000 deep-towed high-resolution multichannel seismic system was designed by the First Institute of Oceanography,Ministry of Natural Resources(FIO,MNR).The system is mainly composed of a plasma spark source(source level:216 dB,main frequency:750 Hz,frequency bandwidth:150-1200 Hz)and a towed hydrophone streamer with 48 channels.Because the source and the towed hydrophone streamer are constantly moving according to the towing configuration,the accurate positioning of the towing hydrophone array and the moveout correction of deep-towed multichannel seismic data processing before imaging are challenging.Initially,according to the characteristics of the system and the towing streamer shape in deep water,travel-time positioning method was used to construct the hydrophone streamer shape,and the results were corrected by using the polynomial curve fitting method.Then,a new data-processing workflow for Kuiyang-ST2000 system data was introduced,mainly including float datum setting,residual static correction,phase-based moveout correction,which allows the imaging algorithms of conventional marine seismic data processing to extend to deep-towed seismic data.We successfully applied the Kuiyang-ST2000 system and methodology of data processing to a gas hydrate survey of the Qiongdongnan and Shenhu areas in the South China Sea,and the results show that the profile has very high vertical and lateral resolutions(0.5 m and 8 m,respectively),which can provide full and accurate details of gas hydrate-related and geohazard sedimentary and structural features in the South China Sea.

关键词： Kuiyang-ST2000 system deep-towed system seismic data process plasma spark source High resolution gas hydrate South China Sea

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Adaptive Statistical Spatial Downscaling of Precipitation Supported by high-resolution Atmospheric Simulation Data for Mountainous Areas of Nepal

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气象学报:英文版 2023年第4期37卷 508-520页

作者： Hua YANG Kun YANG Jun QIN Baohong DING Yaozhi JIANG Yingying CHEN Xu ZHOU Yan WANG Shankar SHARMA National Tibetan Plateau Data Center State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and ResourcesInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101 University of Chinese Academy of Sciences Beijing 100049 Ministry of Education Key Laboratory for Earth System Modeling Department of Earth System ScienceInstitute for Global Change StudiesTsinghua UniversityBeijing 100084 State Key Laboratory of Resources and Environmental Information System Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101 Key Laboratory of Land Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101

In complex terrain regions, it is very challenging to obtain high accuracy and resolution precipitation data that are required in land hydrological studies. In this study, an adaptive precipitation downscaling method is proposed based on the statistical downscaling model MicroMet. A key input parameter in the MicroMet is the precipitation adjustment factor(PAF) that shows the elevation dependence of precipitation. Its value is estimated conventionally based on station observations and suffers sparse stations in high altitudes. This study proposes to estimate the PAF value and its spatial variability with precipitation data from high-resolution atmospheric simulations and tests the idea in Nepal of South Himalayas, where rainfall stations are relatively dense. The result shows that MicroMet performs the best with the PAF value estimated from the simulation data at the scale of approximately 1.5 degrees. Not only the value at this scale is qualitatively consistent with early knowledge obtained from intensive observations, but also the downscaling performance with this value is better than or comparable to that with the PAF estimated from dense station data. Finally, it is shown that the PAF estimation, although critical, cannot replace the importance of increasing input station density for downscaling.

关键词： precipitation statistical downscaling precipitation adjustment factor adaptive estimation High resolution dynamical downscaling

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Aerial-BiSeNet:A real-time semantic segmentation network for High resolution aerial imagery

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Chinese Journal of Aeronautics 2021年第9期34卷 47-59页

作者： Fang WANG Xiaoyan LUO Qixiong WANG Lu LI School of Electronic and Information Engineering Beihang UniversityBeijing 100083China Image Processing Center School of AstronauticsBeihang UniversityBeijing 100083China AVIC Aerospace System Co. Ltd.Beijing 100028China

The aircraft system has recently gained its reputation as a reliable and efficient tool for sensing and parsing aerial scenes.However,accurate and fast semantic segmentation of highresolution aerial images for remote sensing applications is still facing three challenges:the requirements for limited processing resources and low-latency operations based on aerial platforms,the balance between high accuracy and real-time efficiency for model performance,and the confusing objects with large intra-class variations and small inter-class differences in high-resolution aerial images.To address these issues,a lightweight and dual-path deep convolutional architecture,namely Aerial Bilateral Segmentation Network(Aerial-Bi Se Net),is proposed to perform realtime segmentation on high-resolution aerial images with favorable accuracy.Specifically,inspired by the receptive field concept in human visual systems,Receptive Field Module(RFM)is proposed to encode rich multi-scale contextual information.Based on channel attention mechanism,two novel modules,called Feature Attention Module(FAM)and Channel Attention based Feature Fusion Module(CAFFM)respectively,are proposed to refine and combine features effectively to boost the model performance.Aerial-Bi Se Net is evaluated on the Potsdam and Vaihingen datasets,where leading performance is reported compared with other state-of-the-art models,in terms of both accuracy and efficiency.

关键词： Aerial imagery Deap learning High resolution Image segmentation Real time

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high-resolution bone microstructure imaging based on ultrasonic frequency-domain full-waveform inversion

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Chinese Physics B 2021年第1期30卷 295-310页

作者：李义方石勤振李颖宋小军刘成成他得安王威琪 Department of Electronic Engineering Fudan UniversityShanghaiChina Human Phenome Institute Fudan UniversityShanghaiChina Academy for Engineering and Technology Fudan UniversityShanghaiChina

The main challenge in bone ultrasound imaging is the large acoustic impedance contrast and sound velocity differences between the bone and surrounding soft tissue. It is difficult for conventional pulse-echo modalities to give accurate ultrasound images for irregular bone boundaries and microstructures using uniform sound velocity assumption rather than getting a prior knowledge of sound speed. To overcome these limitations, this paper proposed a frequency-domain fullwaveform inversion(FDFWI) algorithm for bone quantitative imaging utilizing ultrasonic computed tomography(USCT).The forward model was calculated in the frequency domain by solving the full-wave equation. The inverse problem was solved iteratively from low to high discrete frequency components via minimizing a cost function between the modeled and measured data. A quasi-Newton method called the limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm(L-BFGS) was utilized in the optimization process. Then, bone images were obtained based on the estimation of the velocity and density. The performance of the proposed method was verified by numerical examples, from tubular bone phantom to single distal fibula model, and finally with a distal tibia-fibula pair model. Compared with the high-resolution peripheral quantitative computed tomography(HR-p QCT), the proposed FDFWI can also clearly and accurately presented the wavelength scaled pores and trabeculae in bone images. The results proved that the FDFWI is capable of reconstructing high-resolution ultrasound bone images with sub-millimeter resolution. The parametric bone images may have the potential for the diagnosis of bone disease.

关键词： quantitative imaging full-waveform inversion bone microstructure ultrasonic computed tomography High resolution

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Efficient,high-resolution topology optimization method based on convolutional neural networks

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Frontiers of Mechanical Engineering 2021年第1期16卷 80-96页

作者： Liang XUE Jie LIU Guilin WEN Hongxin WANG State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body Hunan UniversityChangsha 410082China Center for Research on Leading Technology of Special Equipment School of Mechanical and Electric EngineeringGuangzhou UniversityGuangzhou 510006China

Topology optimization is a pioneer design method that can provide various candidates with high mechanical properties.However,High resolution is desired for optimum structures,but it normally leads to a computationally intractable puzzle,especially for the solid isotropic material with penalization(SIMP)method.In this study,an efficient,high-resolution topology optimization method is developed based on the super-resolution convolutional neural network(SRCNN)technique in the framework of SIMP.SRCNN involves four processes,namely,refinement,path extraction and representation,nonlinear mapping,and image reconstruction.high computational efficiency is achieved with a pooling strategy that can balance the number of finite element analyses and the output mesh in the optimization process.A combined treatment method that uses 2D SRCNN is built as another speed-up strategy to reduce the high computational cost and memory requirements for 3D topology optimization problems.Typical examples show that the high-resolution topology optimization method using SRCNN demonstrates excellent applicability and high efficiency when used for 2D and 3D problems with arbitrary boundary conditions,any design domain shape,and varied load.

关键词： topology optimization convolutional neural network High resolution density-based

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high-resolution Simulation of an Extreme Heavy Rainfall Event in Shanghai Using the Weather Research and Forecasting Model: Sensitivity to Planetary Boundary Layer Parameterization

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Advances in Atmospheric Sciences 2021年第1期38卷 98-115页

作者： Rui WANG Yiting ZHU Fengxue QIAO Xin-Zhong LIANG Han ZHANG Yang DING Key Laboratory of Geographic Information Science Ministry of EducationEast China Normal UniversityShanghai 200241China School of Geographic Sciences East China Normal UniversityShanghai 200241China Institute of Eco-Chongming Shanghai 200062China College of Atmospheric Science Nanjing University of Information Science and TechnologyNanjing 210044China Department of Atmospheric&Oceanic Science University of MarylandCollege ParkMaryland 20742USA Earth System Science Interdisciplinary Center University of MarylandCollege ParkMaryland 20742USA Shanghai Central Meteorological Observatory Shanghai 200030China

In this study,an extreme rainfall event that occurred on 25 May 2018 over Shanghai and its nearby area was simulated using the Weather Research and Forecasting model,with a focus on the effects of planetary boundary layer(PBL)physics using double nesting with large grid ratios(15:1 and 9:1).The sensitivity of the precipitation forecast was examined through three PBL schemes:the Yonsei University Scheme,the Mellor−Yamada−Nakanishi Niino Level 2.5(MYNN)scheme,and the Mellor−Yamada−Janjic scheme.The PBL effects on boundary layer structures,convective thermodynamic and large-scale forcings were investigated to explain the model differences in extreme rainfall distributions and hourly variations.The results indicated that in single coarser grids(15 km and 9 km),the extreme rainfall amount was largely underestimated with all three PBL schemes.In the inner 1-km grid,the underestimated intensity was improved;however,using the MYNN scheme for the 1-km grid domain with explicitly resolved convection and nested within the 9-km grid using the Kain−Fritsch cumulus scheme,significant advantages over the other PBL schemes are revealed in predicting the extreme rainfall distribution and the time of primary peak rainfall.MYNN,with the weakest vertical mixing,produced the shallowest and most humid inversion layer with the lowest lifting condensation level,but stronger wind fields and upward motions from the top of the boundary layer to upper levels.These factors all facilitate the development of deep convection and moisture transport for intense precipitation,and result in its most realistic prediction of the primary rainfall peak.

关键词： PBL parameterization extreme rainfall High resolution

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Plaques of Nonstenotic Basilar Arteries with Isolated Pontine Infarction on Three-dimensional high Isotropic resolution Magnetic Resonance Imaging

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Chinese Medical Journal 2015年第11期128卷 1433-1437页

作者： Xian-Jin Zhu Wei-Jian Jiang Lei Liu Li-Bin Hu Wu Wang Zun-Jing Liu Department of Radiology China-Japan Friendship Hospital Beijing 100029 China Department of New Era Stroke Care and Research Institute The Second Artillery'Geneial HospiiaI-People's Liberation Army Beijing 100088 China Department of Neurology China-Japan Friendship Hospital Beijing 100029 China

Background： There are few studies for evaluating plaque characteristics of nonstenotic basilar arteries （BA）. Our aim was to determine entire BA plaques with a three-dimensional volumetric isotropic turbo spin-echo acquisition （VISTA） and investigate the differences between the patients with and without isolated pontine infarction （IPI）. Methods： Twenty-four consecutive symptomatic patients with nonstenotic BA on time of flight magnetic resonance angiography （TOF MRA） were enrolled from China-Japan Friendship Hospital between January 2014 and December 2014. BA was classified as ＂normal＂ or ＂irregular＂ based on TOF MRA, and ＂normal wall＂, ＂slight wall-thickening＂, and ＂plaque＂ based on three-dimensional VISTA images. Outcomes from MRA and VISTA were compared. Patients were categorized as IPI and non-lPl groups based on the diffusion-weighted imaging. Clinical and plaque characteristics were compared between the two groups. Results： A total of 1024 image slices including 311 （30.37%） plaque slices, 427 （41.70%） slight wall-thickening slices, and 286 （27.93%） normal wall slices for the entire BA from 23 patients were finally included for analysis. VISTA images detected plaques in all the 9 （100%） irregular MRA patients and 7 of 14 （50%） normal MRA patients. IPl was found in 11 （47.83%） patients. Compared to non-IPI group, the IPI group had a higher percentage of plaque slices （P = 0.001 ） and lower percentage of normal wall slices （P = 0.014） than non-IPl group. Conclusions： Three-dimensional V1STA images enable detection of BA plaques not visualized by MRA. BA plaques could be found in both the IPl and non-IPl group. However, IPI group showed plaques more extensively in BA than the non-IPI group.

关键词： Atherosclerosis Basilar Artery High resolution Isolated Pontine Infarction Magnetic Resonance Imaging

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Perspective of Chinese GF-1 high-resolution satellite data in agricultural remote sensing monitoring

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Journal of Integrative Agriculture 2017年第2期16卷 242-251页

作者： ZHOU Qing-bo YU Qiang-yi LIU Jia WU Wen-bin TANG Hua-jun Key Laboratory of Agri-informatics Ministry of Agriculture/Institute of Agricultural Resources and Regional PlanningChinese Academy of Agricultural Sciences College of Urban & Environmental Sciences Central China Normal University

high-resolution satellite data have been playing an important role in agricultural remote sensing monitoring. However, the major data sources of high-resolution images are not owned by China. The cost of large scale use of High resolution imagery data becomes prohibitive. In pace of the launch of the Chinese ＂High resolution Earth Observation Systems＂, China is able to receive superb high-resolution remotely sensed images （GF series） that equalizes or even surpasses foreign similar satellites in respect of spatial resolution, scanning width and revisit period. This paper provides a perspective of using High resolution remote sensing data from satellite GF-1 for agriculture monitoring. It also assesses the applicability of GF-1 data for agricultural monitoring, and identifies potential applications from regional to national scales. GF-1＇s High resolution （i.e., 2 m/8 m）, high revisit cycle （i.e., 4 days）, and its visible and near-infrared （VNIR） spectral bands enable a continuous, efficient and effective agricultural dynamics monitoring. Thus, it has gradually substituted the foreign data sources for mapping crop planting areas, monitoring crop growth, estimating crop yield, monitoring natural disasters, and supporting precision and facility agriculture in China agricultural remote sensing monitoring system （CHARMS）. However, it is still at the initial stage of GF-1 data application in agricultural remote sensing monitoring. Advanced algorithms for estimating agronomic parameters and soil quality with GF-1 data need to be further investigated, especially for improving the performance of remote sensing monitoring in the fragmented landscapes. In addition, the thematic product series in terms of land cover, crop allocation, crop growth and production are required to be developed in association with other data sources at multiple spatial scales. Despite the advantages, the issues such as low spectrum resolution and image distortion associated with high spatial resolution and wide swath width, might pose challenges fo

关键词： GF-1 High resolution agricultural monitoring remote sensing CHARMS

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