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An improved third-order HWCNS for compressible flow simulation on curvilinear grids

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Advances in Aerodynamics 2021年第1期3卷 580-596页

作者： Mingyang Cheng Lingyan tang Yu Liu huajun Zhu College of Liberal Arts and Sciences National University of Defense Technology410073 ChangshaChina School of Mechanical Engineering Shanghai Jiao Tong University200240 ShanghaiChina State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center621000 MianyangChina.

Due to the very high requirements on the quality of computational grids,stability property and computational efficiency,the application of high-order schemes to complex flow simulation is greatly constrained.In order to solve these problems,the third-order hybrid cell-edge and cell-node weighted compact nonlinear scheme(HWCNS3)is improved by introducing a new nonlinear weighting mechanism.The new scheme uses only the central stencil to reconstruct the cell boundary value,which makes the convergence of the scheme more stable.The application of the scheme to Euler equations on curvilinear grids is also discussed.Numerical results show that the new HWCNS3 achieves the expected order in smooth regions,captures discontinuities sharply without obvious oscillation,has higher resolution than the original one and preserves freestream and vortex on curvilinear grids.

关键词： Third-order Compact nonlinear scheme Curvilinear grids Nonlinear interpolation

Time-Series Modeling and Prediction of Global Monthly Absolute Temperature for Environmental Decision Making

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Advances in Atmospheric Sciences 2013年第2期30卷 382-396页

作者： YE Liming YANG Guixia Eric VAN RANST TANG HuaJun Key Laboratory of Agri-Informatics Ministry of Agriculture/Institute ofAgricultural Resources and Regional PlanningChinese Academy of Agricultural Sciences Beijing 100081 Department of Geology and Soil Science (WE13) Ghent University Krijgslaan 281 9000 Gent Belgium Chinese Academy of Agricultural Sciences Beijing 100081

A generalized, structural, time series modeling framework was developed to analyze the monthly records of absolute surface temperature, one of the most important environmental parameters, using a deterministicstochastic combined （DSC） approach. Although the development of the framework was based on the characterization of the variation patterns of a global dataset, the methodology could be applied to any monthly absolute temperature record. Deterministic processes were used to characterize the variation patterns of the global trend and the cyclic oscillations of the temperature signal, involving polynomial functions and the Fourier method, respectively, while stochastic processes were employed to account for any remaining patterns in the temperature signal, involving seasonal autoregressive integrated moving average （SARIMA） models. A prediction of the monthly global surface temperature during the second decade of the 21st century using the DSC model shows that the global temperature will likely continue to rise at twice the average rate of the past 150 years. The evaluation of prediction accuracy shows that DSC models perform systematically well against selected models of other authors, suggesting that DSC models, when coupled with other ecoenvironmental models, can be used as a supplemental tool for short-term （10-year） environmental planning and decision making.

关键词： time series analysis statistical model polynomial trend Fourier method ARIMA climatechange

A comparative analysis of five global cropland datasets in China

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Science China Earth Sciences 2016年第12期59卷 2307-2317页

作者： LU Miao WU WenBin ZHANG Li LIAO AnPing PENG Shu TANG HuaJun Key Laboratory of Agri-informatics Ministry of Agriculture/Institute of Agricultural Resources and Regional PlanningChinese Academy of Agricultural Sciences National Geomatics Centre of China

Accurate information of cropland area and spatial location is critical for studies of national food security, global environmental change, terrestrial ecosystem geophysics and the geochemical cycle. In this paper, we compared five global cropland datasets in circa 2010 of China from in terms of cropland area and spatial location, including Global Land30, FROM-GLC, Glob Cover, MODIS Collection 5, and MODIS Cropland. The results showed that the accuracies of cropland area and spatial location of Globe Land30 were higher than the other four products. The cropland areas of the five products varied in most of the provinces. Compared with the statistical data, the best goodness of fit was obtained using Globe Land30, followed by MODIS Collection 5 and FROM-GLC, with MODIS Cropland and Glob Cover having the poorer accuracies. Regarding the spatial location of cropland, Globe Land30 achieved the best accuracy, followed by FROM-GLC and MODIS Collection 5, with Glob Cover and MODIS Cropland having the poorer accuracies. In addition, the spatial agreement of the five datasets was reduced from agricultural production area to pastoral area and significantly affected by elevation and slope factors. Although the spatial resolution of MODIS Collection 5 was the lowest, accuracies of the cropland area and spatial location were better than those of Glob Cover and MODIS Cropland. Therefore, high spatial resolution remote sensing images can help to improve the accuracy of the dataset during land cover mapping, while it is also important to select a suitable classification method. Furthermore, in northwestern and southeastern China, spectral mixing pixels are universal because of the complicated landscape and fragmentized topography and result in uncertainty and poor consistency when using the five products. Therefore, these regions require additional attention in future cropland mapping studies.

关键词： Land cover Cropland area Spatial location Accuracy Spatial agreement

Change analysis of rice area and production in China during the past three decades

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Journal of Geographical Sciences 2013年第6期23卷 1005-1018页

作者： LIU Zhenhuan LI Zhengguo tang Pengqin LI Zhipeng WU Wenbin YANG Peng YOU Liangzhi TANG HuaJun Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences / Key Laboratory of Agri-informatics Ministry ofAgriculture Beijing 100081 China Environment and Production Technology Division International Food Policy Research Institute 2033KStreet NW Washington DC 20006 USA

Rice＇s spatial-temporal distributions, which are critical for agricultural, environ- mental and food security research, are affected by natural conditions as well as socio-eco- nomic developments. Based on multi-source data, an effective model named the Spatial Production Allocation Model （SPAM） which integrates arable land distribution, administrative unit statistics of crop data, agricultural irrigation data and crop suitability data, was used to get a series of spatial distributions of rice area and production with 10-km pixels at a national scale -it was applied from the early 1980s onwards and used to analyze the pattern of spatial and temporal changes. The results show that significant changes occurred in rice in China during 1980-2010. Overall, more than 50% of the rice area decreased, while nearly 70% of rice production increased in the change region during 1980-2010. Spatially, most of the increased area and production were in Northeast China, especially, in Jilin and Heilongjiang; most of the decreased area and production were located in Southeast China, especially, in regions of rapidly urbanization in Guangdong, Fujian and Zhejiang. Thus, the centroid of rice area was moved northeast approximately 230 km since 1980, and rice production about 320 km, which means rice production moved northeastward faster than rice area because of the significant rice yield increase in Northeast China. The results also show that rice area change had a decisive impact on rice production change. About 54.5% of the increase in rice pro- duction is due to the expansion of sown area, while around 83.2% of the decrease in rice production is due to contraction of rice area. This implies that rice production increase may be due to area expansion and other non-area factors, but reduced rice production could largely be attributed to rice area decrease.

关键词： rice distribution spatial production allocation model spatial-temporal changes China

Managed grassland alters soil N dynamics and N2O emissions in temperate steppe

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Journal of Environmental Sciences 2018年第4期30卷 20-30页

作者： Lijun Xu Xingliang Xu Xuejuan tang Xiaoping Xin Liming Ye Guixia Yang huajun tang Shijie Lv Dawei Xu Zhao Zhang Hulunber Grassland Ecosystem Observation and Research Station Institute of Agricultural Resources and Regional Planning of ChineseAcademy of Agricultural Sciences Beijing 100081 China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100081 China Department of Geology (WE13) Ghent University 9000 Gent Belgium Science College of Inner Mongolia Agricultural University Hohhot Inner Mongolia 010018 China

Reclamation of degraded grasslands as managed grasslands has been increasingly accelerated in recent years in China. Land use change affects soil nitrogen（N） dynamics and nitrous oxide（N2O） emissions. However, it remains unclear how large-scale grassland reclamation will impact the grassland ecosystem as a whole. Here, we investigated the effects of the conversion from native to managed grasslands on soil N dynamics and N2O emissions by field experiments in Hulunber in northern China. Soil（0-10 cm）, nitrate（NO3-）,ammonium（NH4＋）, and microbial N were measured in plots in a temperate steppe（Leymus chinensis grassland） and two managed grasslands（Medicago sativa and Bromus inermis grasslands） in 2011 and 2012. The results showed conversion of L. chinensis grassland to M.sativa or B. inermis grasslands decreased concentrations of NO3--N, but did not change NH4-N . Soil microbial N was slightly decreased by the conversion of L. chinensis grassland to M.sativa, but increased by the conversion to B. inermis. The conversion of L. chinensis grassland to M. sativa（i.e., a legume grass） increased N2O emissions by 26.2%, while the conversion to the B. inermis（i.e., a non-legume grass） reduced N2O emissions by 33.1%. The conversion from native to managed grasslands caused large created variations in soil NO3-＋-N and NH4-N concentrations. Net N mineralization rates did not change significantly in growing season or vegetation type, but to net nitrification rate. These results provide evidence on how reclamation may impact the grassland ecosystem in terms of N dynamics and N2O emissions.

关键词： Temperate steppe Managed grassland Land use Nitrogen mobility N2O emissions

Scenario-based assessment of future food security

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Journal of Geographical Sciences 2011年第1期21卷 3-17页

作者： WU Wenbin TANG HuaJun YANG Peng YOU Liangzhi ZHOU Qingbo CHEN Zhongxin SHIBASAKI Ryosuke Key Laboratory of Resources Remote Sensing & Digital Agriculture Ministry of Agriculture Beijing 100081 China Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences Beijing 100081 China Center for Spatial Information Science University of Tokyo Tokyo 153-8505 Japan International Food Policy Research Institute Washington DC 20006 USA

This paper presents a scenario-based assessment of global future food security. To do that,the socio-economic and climate change scenarios were defined for the future and were linked to an integrated modeling framework. The crop yields simulated by the GIS-based Environmental Policy Integrated Climate （EPIC） model and crop areas simulated by the crop choice decision model were combined to calculate the total food production and per capita food availability,which was used to represent the status of food availability and stability. The per capita Gross Domestic Product （GDP） simulated by IFPSIM model was used to reflect the situation of food accessibility and affordability. Based on these two indicators,the future food security status was assessed at a global scale over a period of approximately 20 years,starting from the year 2000. The results show that certain regions such as South Asia and most African countries will likely remain hotspots of food insecurity in the future as both the per capita food availability and the capacity of being able to import food will decrease between 2000 and 2020. Low food production associated with poverty is the determining factor to starvation in these regions,and more efforts are needed to combat hunger in terms of future actions. Other regions such as China,most Eastern European countries and most South American countries where there is an increase in per capita food availability or an increase in the capacity to import food between 2000 and 2020 might be able to improve their food security situation.

关键词： scenario food security per capita food availability per capita GDP model assessment

Application of TERRA/MODIS images, TM images and weather data to assess the effect of cold damage on rice yield

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International Journal of Agricultural and Biological Engineering 2010年第2期3卷 31-38页

作者： He Yingbin Satoshi Uchida TANG HuaJun Chen Youqi Liu Jia Key Laboratory of Resources Remote Sensing and Digital Agriculture/Hulunber Grassland Ecosystem Observation and Research Station Chinese Academy of Agricultural SciencesBeijing 100081China Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural SciencesBeijing 100081China Japan International Research Centre for Agricultural Sciences(JIRCAS) OhwashiTsukubaIbaraki305-8686 Japan

Data assimilation is extensively applied in agricultural remote sensing application.However,integration of multi-temporal and high spatial resolution images with crop growth model to evaluate the effect of cold damage on paddy rice was still lacking.In this paper,authors applied data assimilation combining LANDSAT/TM,a series of terra MODIS images with SIMRIW model to detect how cold damage affected paddy rice yield per unit in the Wuchang county,Heilongjiang province for the year 2006.In the study,MODIS images selected corresponding to a series of the key rice growth phases were utilized to retrieve daily LAI values that were needed in the SIMRIW model.Meanwhile,TM was applied to accurately extract paddy rice sown areas.The study results showed that the yield per unit was 10,628.5840 kg/ha under cold damage condition,which was little less than 10,768.3210 kg/ha under optimal condition.Moreover,the ratio of the calculated yield per value under cold damage condition to the actual value of paddy rice yield per unit was 0.56.The result was better than that acquired in USA and Japan.The results of this study expected to provide suggestions to policy-makers and reference to related research.

关键词： data assimilation MODIS TM cold damage rice yield per unit NDVI LAI

Hybrid optical parametrically-oscillating emitter at 1930 nm for volumetric photoacoustic imaging of water content

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eLight 2022年第1期2卷 68-74页

作者： Jiawei Shi Mingsheng Li huajun tang Jiqiang Kang Najia Sharmin Amir Rosenthal Kenneth K.Y.Wong Department of Electrical and Electronic Engineering The University of Hong Kong Pokfulam RoadHong KongChina.2 Department of Electrical EngineeringTechnion–Israel Institute of TechnologyTechnion City32000 HaifaIsrael Advanced Biomedical Instrumentation Centre Hong Kong Science ParkShatinNew TerritoriesHong KongChina

Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.

关键词： Fiber optical parametric oscillator Thulium-doped fiber laser Photoacoustic microscopy

Spatio-temporal dynamics of maize cropping system in Northeast China between 1980 and 2010 by using spatial production allocation model

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Journal of Geographical Sciences 2014年第3期24卷 397-410页

作者： TAN Jieyang YANG Peng LIU Zhenhuan WU Wenbin ZHANG Li LI Zhipeng YOU Liangzhi TANG HuaJun LI Zhengguo Key Laboratory of Agri-informatics Ministry of Agriculture/Institute of Agricultural Resources and Regional Planning Chinese Academy of Agricultural Sciences Beijing 100081 China Geography and Planning School of Sun Yat-sen University Guangzhou 510275 China Environment and Production Technology Division International Food Policy Research Institute 2033K Street NW Washington DC 20006 USA

Understanding crop patterns and their changes on regional scale is a critical re- quirement for projecting agro-ecosystem dynamics. However, tools and methods for mapping the distribution of crop area and yield are still lacking. Based on the cross-entropy theory, a spatial production allocation model （SPAM） has been developed for presenting spa- tio-temporal dynamics of maize cropping system in Northeast China during 1980-2010. The simulated results indicated that （1） maize sown area expanded northwards to 48~N before 2000, after that the increased sown area mainly occurred in the central and southern parts of Northeast China. Meanwhile, maize also expanded eastwards to 127°E and lower elevation （less than 100 m） as well as higher elevation （mainly distributed between 200 m and 350 m）; （2） maize yield has been greatly promoted for most planted area of Northeast China, espe- cially in the planted zone between 42°N and 48°N, while the yield increase was relatively homogeneous without obvious longitudinal variations for whole region; （3） maize planting density increased gradually to a moderately high level over the investigated period, which reflected the trend of aggregation of maize cultivation driven by market demand.

关键词： spring maize spatial production allocation model spatio-temporal pattern Northeast China