基于支持向量机的浙江汛期旱涝预测方法研究

利用浙江省38个测站的降水量资料,得到了能够反映全省旱涝状况的指标,将其作为预报量,通过对前期大气环流场、海温场的相关分析,提取高相关因子,然后运用逐步回归和支持向量机回归技术分别建立浙江省汛期早涝短期气候预测模型,并进行了对比分析.结果表明:支持向量机回归模型集中了众多预报因子的预报信息.有效地利用了支持向量机方法的非线性映射能力,无论在历史样本拟合的精度上还是模型实际预测的能力上都比逐步回归模型有一定提高,有良好的应用前景.     

加荷条件下软黏土的孔隙演化特征

开展上海软黏土的宏微观三轴剪切试验,研究软黏土受荷状态下孔隙的演化特征。结果表明：局部变形在加荷初期就开始发生。随着荷载的增加,细碎团聚体增多,孔隙不断地扩展,生成大的贯通孔隙,孔隙定向排列明显,剪切带形成。微观结构参数与剪应力比呈非线性正相关关系,最大孔隙面积、孔隙比、孔隙各向异性率及分布分维数在受荷初期缓慢地增大,后期快速增大。应变为8%时,最大各向异性率达到0.68,最大孔隙比为1.96。剪切带附近的微观结构参数都大于带外值。在受荷过程中,土的微观结构发生劣化,软黏土变形过程分为损伤开始、损伤发展剪切带形成和土体破坏3阶段,微观结构的劣化与土的宏观力学特性紧密相联系。     

An Effective Control System of Thrust and Moment Modulation for a Dynamically Positioned Vessel

Dynamic positioning (DP) is an operation method whereby the position of a surface vessel is maintained in close proximity to a required position in the horizontal plane through the controlled application of forces and moments generated by purposely installed thrusters. When estimating thrust, this kind of conventional control system often uses many acceleration sensors, velocity sensors, environment sensors, and filters. Usually, these sensors have measured electrical errors. To reduce the number of sensors used and to decrease the measurement errors, this article presents an effective control system for estimating thrust and moment commands, which is based on energy and impulsemomentum principles. Donha and Brinati's example is followed to verify the feasibility of the present control system, which performs semisubmersible platform positioning using an LQG controller, and the results are feasible and economical. A simulated coring vessel marine positioning in southern Taiwan is presented, which can estimate the counterthrust and moment commands, and the complex environmental forces and moments are described. The results can provide a valuable control system for dynamically positioned vessels.     

福建省海洋非法采砂行为管控初探

天然海砂是一种海洋矿产资源,由于在城市建设中使用十分广泛,海砂成为仅次于石油天然气的海洋第二大矿产资源。但近年来由于大量无度开采海砂,对海洋生态环境、海上航行安全以及建筑物安全都造成极大的破坏和影响。对此,各地执法部门进行了一系列打击非法采挖海砂专项行动,虽取得一定成效,但违法采挖海砂的猖獗势头依然未能得到遏制。文章从目前海砂市场的供求现状以及非法采挖海砂造成的问题出发,对执法部门打击非法采挖海砂未能取得预期效果的原因进行分析,并提出合理规划海砂合法开采、加大非法采砂惩处力度、合力完善治砂长效机制、用现代信息技术助力采砂监管等4个方面的解决思路,规范海洋采砂行为,使市场需求和环境保护得到兼顾。     

洋能否为中用?西方政治地理与地缘政治发展的借鉴与反思

以西方为主的国外政治地理和地缘政治学说为中国政治地理和地缘政治的发展提供了很好的参照和基础。因此,如何理性对待西方的政治地理学和地缘政治学的研究、如何正确处理中国政治地理学和地缘政治学中的本土化与国际化关系是关乎中国政治地理学和地缘政治学学科方向的重要议题。然而,目前中国政治地理学和地缘政治学的发展在这一问题上存在困惑乃至两难。一方面,过度依赖西方研究框架和理论为中国政治地理学和地缘政治学的学科建设带来了一定风险;另一方面,在对西方研究保持谨慎态度的同时不能走向封闭乃至仇外的极端,破除“唯西方论”的同时不能走进“中国特殊论”的陷阱。为此,国内高校和科研院所从事政治地理和地缘政治研究的青年学者自发于2019年举办了一次“政治地理与地缘政治理论前沿”青年论坛,集中探讨了对西方政治地理与地缘政治发展的借鉴与反思,取得了初步的共识。具体而言,西方政治地理学和地缘政治学研究议题的多尺度性、研究方法的多样性、研究氛围的批判精神、研究视野的国际化和研究规范的严谨性等方面值得中国借鉴;而历史视角缺失、知识生产不平衡、地图空间表达不足、话语分析过多、解决现实问题不足等方面存在局限,中国政治地理学和地缘政治学未来发展过程中应加以避免。希望本次讨论抛砖引玉,吸引更多学者共同推动中国政治地理学和地缘政治学的学科发展。     

广域网络环境下的土地资源空间数据更新机制

在分析土地资源数据更新内部联动性较强等特点的基础上,研究了适合广域网络环境的土地资源数据更新机制。该土地资源数据更新机制采用选定工作区域、数据提取、数据下载、离线数据编辑、数据上传、数据更新等流程来具体实现。测试表明：该土地资源数据更新机制能较好地运用于县级土地资源管理部门,满足县、乡等多级土地资源管理的日常业务需求。     

Free-surface evolution and wave kinematics for nonlinear uni-directional focused wave groups

This paper concerns the propagation of transient wave groups, focused at a point in time and space to produce locally large waves having a range of steepness. The experimental study was carried out in a wave flume at Dalian University of Technology. The numerical simulations were based on a nonlinear boundary integral equation solved by a higher-order boundary element method (HOBEM). Rather than simulate the whole experimental tank, local surface elevation measurements were used to drive the numerical solution from a point less than two wavelengths upstream of the focus position, leading to significant savings in computational time. Excellent agreement is achieved between the water surface elevations and the water particle kinematics measured in the experiments and those predicted numerically at wave group focus, even for near-breaking waves up to a steepness of kA=0.405 for which even locally matched 2nd-order theory is inadequate. Results based on the linear and 2nd-order theory are also presented in the comparisons. When compared with the first- and 2nd-order solutions, the fully nonlinear wave–wave interactions produce a steeper wave envelope in which the central wave crest is higher and narrower, while the adjacent wave troughs are broader and less deep.     

台阶式变深水槽造波的解析研究台阶式变深水槽造波的解析研究

利用特征函数展开法对台阶式变深水槽中推板式造波机造波问题进行了研究,建立了相应速度势和波面的解析表达式。与高阶边界元方法(HOBEM)数值结果进行了对比,验证了本解析解的正确性。通过数值试验,研究了台阶对入射波的影响,同时分析了造波板所在位置（上部台阶）水深、水槽工作区（下部台阶）水深、造波板运动周期和造波板水平位置等因素对生成波浪高度的影响。由此选择合适的造波板所在位置及水深来得到所需要的波浪高度,进而根据需要生成波浪的周期和波幅 来反演造波板的运动。     

The reflection of regular and irregular waves by a partially perforated caisson breakwater on a step bed

This study examines the reflection of regular and irregular waves from a partially perforated caisson breakwater located on a step bed. The step bed is treated as an idealized rubble mound foundation. Based on the linear potential theory, an analytical solution is developed to calculate the reflection coefficient of the structure subjected to regular waves. The matched eigenfunction expansion method is used for the solution. The regular wave method is also extended to irregular waves using a linear transfer function. The calculated results obtained for limiting cases are exactly the same as corresponding results given by the previous researchers. The present predictions also agree well with experimental data in the published literatures. Numerical experiments are conducted to examine the variations of the reflection coefficient versus its main effect factors, and some interesting results are presented.     

台阶式变深水槽造波的解析研究

利用特征函数展开法对台阶式变深水槽中推板式造波机造波问题进行了研究,建立了相应速度势和波面的解析表达式。与高阶边界元方法(HOBEM)数值结果进行了对比,验证了本解析解的正确性。通过数值试验,研究了台阶对入射波的影响,同时分析了造波板所在位置(上部台阶)水深、水槽工作区(下部台阶)水深、造波板运动周期和造波板水平位置等因素对生成波浪高度的影响。由此选择合适的造波板所在位置及水深来得到所需要的波浪高度,进而根据需要生成波浪的周期和波幅来反演造波板的运动。