基于MSPA-MCR模型的云南德昂族乡景观生态安全格局构建

在社会经济高速发展的冲击下,传统少数民族地区的生态景观呈现“破碎化”“边缘化”的现象。本研究以云南德昂族乡为研究区,采用形态学空间分析(MSPA)和景观连通性指数分析方法,提取出连通性较高且具有重要意义的生态源地,基于AHP层次分析法选取地形地貌、自然环境、地质灾害、人类活动四个方面的10个阻力因子作为指标,构建德昂族乡生态综合阻力面,结合最小阻力模型(MCR)生成潜在生态廊道,最后基于重力模型对潜在廊道进行识别并提取出重要的生态廊道,构建德昂族乡景观生态安全格局。在此基础上,提出加强生态源地的保护和生态廊道的建设以及建设生态踏脚石的建议,以期为我国少数民族乡生态环境保护以及生物多样性营造提供参考。     

物流绩效水平对中国—RCEP国家农产品出口效率的影响

基于2007—2018年RCEP国家LPI及其分项指标的描述分析,利用随机前沿引力模型探究中国—RCEP农产品出口效率和潜力以及国际物流绩效对出口效率的影响。结果表明:中国对RCEP伙伴国农产品出口效率较低,出口潜力较大。国际物流绩效有力解释了存在贸易损失的原因,海关效率、基础设施物流服务质量与能力和货物可追溯性对贸易效率的提升存在显著促进作用。为进一步提升农产品出口效率,中国应重点开发印度尼西亚、菲律宾和缅甸三个农产品贸易潜力较大的市场,加强与其物流基础设施建设的投资合作,帮助其提升物流绩效水平。     

Effects of land use/cover change (LUCC) on the spatiotemporal variability of precipitation and temperature in the Songnen Plain,China

Understanding the effects of land use/cover change (LUCC) on regional climate is critical for achieving land use system sustainability and global climate change mitigation. However, the quantitative analysis of the contribution of LUCC to the changes of climatic factors, such as precipitation & temperature (P&T), is lacking. In this study, we combined statistical methods and the gravity center model simulation to quantify the effects of long-term LUCC on P&T in the Songnen Plain (SNP) of Northeast China from 1980–2018. The results showed the spatiotemporal variability of LUCC. For example, paddy field had the largest increase (15 166.43 km²) in the SNP, followed by dry land, while wetland had the largest decrease (19 977.13 km²) due to the excessive agricultural utilization and development. Annual average precipitation decreased at a rate of –9.89 mm per decade, and the warming trends were statistically significant with an increasing rate of 0.256°C per decade in this region since 1980. The model simulation revealed that paddy field, forestland, and wetland had positive effects on precipitation, which caused their gravity centers to migrate towards the same direction accompanied by the center of precipitation gravity, while different responses were seen for building land, dry land and unused land. These results indicated that forestland had the largest influence on the increase of precipitation compared with the other land use types. The responses in promoting the temperature increase differed significantly, being the highest in building land, and the lowest in forestland. In general, the analysis of regional-scale LUCC showed a significant reduction of wetland, and the increases in building land and cropland contributed to a continuous drying and rapid warming in the SNP.     

Check dam extraction from remote sensing images using deep learning and geospatial analysis: A case study in the Yanhe River Basin of the Loess Plateau,China

Check dams are widely used on the Loess Plateau in China to control soil and water losses, develop agricultural land, and improve watershed ecology. Detailed information on the number and spatial distribution of check dams is critical for quantitatively evaluating hydrological and ecological effects and planning the construction of new dams. Thus, this study developed a check dam detection framework for broad areas from high-resolution remote sensing images using an ensemble approach of deep learning and geospatial analysis. First, we made a sample dataset of check dams using GaoFen-2 (GF-2) and Google Earth images. Next, we evaluated five popular deep-learning-based object detectors, including Faster R-CNN, You Only Look Once (version 3) (YOLOv3), Cascade R-CNN, YOLOX, and VarifocalNet (VFNet), to identify the best one for check dam detection. Finally, we analyzed the location characteristics of the check dams and used geographical constraints to optimize the detection results. Precision, recall, average precision at intersection over union (IoU) threshold of 0.50 (AP₅₀), IoU threshold of 0.75 (AP₇₅), and average value for 10 IoU thresholds ranging from 0.50-0.95 with a 0.05 step (AP_50-95), and inference time were used to evaluate model performance. All the five deep learning networks could identify check dams quickly and accurately, with AP_50-95, AP₅₀, and AP₇₅ values higher than 60.0%, 90.0%, and 70.0%, respectively, except for YOLOv3. The VFNet had the best performance, followed by YOLOX. The proposed framework was tested in the Yanhe River Basin and yielded promising results, with a recall rate of 87.0% for 521 check dams. Furthermore, the geographic analysis deleted about 50% of the false detection boxes, increasing the identification accuracy of check dams from 78.6% to 87.6%. Simultaneously, this framework recognized 568 recently constructed check dams and small check dams not recorded in the known check dam survey datasets. The extraction results will support efficient watershed management and guide future studies on soil erosion in the Loess Plateau.     

基于SIMA的重力式网箱阻力性能计算

近年来，深远海渔业养殖装备已引起国内外相关领域的广泛关注，其中网衣系统是渔业平台的重要组成部分。网衣属于小尺度柔性构件，在水动力作用下会产生变形，其阻力性能预报归于水弹性问题的范畴。目前，出现了1种较先进的基于非线性有限元的网衣水动力计算方法，该方法将势流理论与有限元方法相结合，用于求解网衣受力和变形。文章采用该方法计算一型重力式网箱的阻力性能，并将计算结果与试验数据进行比较，结果表明，采用该方法可以较好地预报网衣阻力性能，从而为开展大型深远海渔业平台网衣系统的阻力计算夯实基础。     

基于县域单元粮食生产空间演变与重心变化的测算分析——以广东省为例

本研究采用县域数据,以广东省121个县（区）作为研究对象,分析2000—2019年粮食生产空间演变的动态路径以及重心变化以及2000—2019年广东粮食生产的重点区域和西南地区粮食生产的变化。结果表明：中部偏东的趋势较强,并逐渐以珠三角为中心向四周移动,总体呈现“东、西扩张、北波动、珠三角收缩”的态势。此外,粮食生产逐步向重点县转移,产粮10大县产量占广东省22%~25%,产粮前20位的产量占广东省的40%~43%,产粮前40位的产量占广东省的63%~68%,但近年来保持相对稳定。     

沉积作用及应力历史对自重应力和沉降的影响

土体的沉积作用和应力历史会影响土体自重应力的确定，也会影响地基最终沉降量的确定。鉴于e-lnp比e-lgp坐标图能更方便、精确地描述线性问题，根据e-lnp坐标图推导沉积作用对成层土、正常固结土、超固结土的自重应力与沉降影响的计算式。用该计算式对昆明滇池国际会展中心部分深厚软土地基的自重应力和最终沉降量进行计算，并用计算结果和不考虑沉积作用及应力历史影响的计算结果进行对比分析，结果表明，沉积作用对深厚软粘土自重应力和最终沉降量计算值的影响非常显著，并且土体厚度越厚、上覆荷载越大，其影响越明显。     

淤地坝对黄土浅层滑坡的减蚀作用

为了研究淤地坝淤积对浅层滑坡的减蚀作用,基于三维连续介质动态数值模型,采用Voellmy流变模型,分析了侵蚀基准面抬升后黄土滑坡运动参数、动力参数以及能量参数的变化规律。结果表明:浅层滑坡在沟谷坡运动过程中,平均速度、前缘速度、侵蚀物质体积和总动能急剧增加,导致滑坡在接触坡脚时前缘速度出现波动且坡脚处侵蚀严重,极具破坏性。随着侵蚀基准面逐渐抬升,滑坡运行时间和平均速度峰值呈"S"形函数下降趋势,前缘速度和滑坡移动距离呈线性函数下降趋势,侵蚀物质体积和总动能呈指数函数下降趋势。随着侵蚀基准面逐渐抬升,滑坡的运动空间和侵蚀空间逐渐减少,仅在一定程度上降低了滑坡速度,但却有效抑制了滑坡的侵蚀作用,使侵蚀物质质量急剧减少,从而有效减少了滑坡体侵蚀总动能,在很大程度上减轻了浅层滑坡的致灾强度和致灾规模。研究结果揭示了淤地坝可以通过抬升侵蚀基准面来减少侵蚀,有助于加深淤地坝对黄土浅层滑坡减蚀作用机理的理解。     

基于无线图像传输的智能侦察系统研究

参照卫星驱动机构使用的C36018固体润滑角接触球轴承，建立了三维模型，借助ABAQUS有限元软件，对固体润滑滚动轴承进行显式动力学仿真分析，得到了不同转速和轴向力下轴承各部件的动态接触应力及滚珠和内圈的运动状态，并与无涂层润滑条件下的结果进行了对比分析.结果表明：轴向载荷增加，轴承各个部件的应力幅值都有所增大，滚珠和保持架开始转动所需的时间缩短；转速增加，接触区域应力峰值变化频率增大，但对应力幅值的影响很小；具有固体润滑涂层的滚道接触面，在与滚珠发生接触时，涂层发生弹性变形，接触面积增大，接触应力减小，可以有效地保护轴承.