面向多区域高效搜索的UUV集群任务分配

UUV 集群在执行大范围搜索任务时分配方案的优劣对于提高任务执行效率至关重要。研究解决 UUV 集群同时进行多区域搜索中的任务分配问题,使得全部区域搜索完成时长最小。针对传统匈牙利算法无法高效解决不平衡任务分配的问题,提出一种改进匈牙利多轮分配算法。该算法通过多轮任务分配,实现空闲 UUV 高效利用和目标区域合理分配,通过在代价函数中引入边际代价和保守估计时长,大大减小了全部区域搜索完成时长。仿真实验结果表明：提出的算法相比传统匈牙利算法能够合理分配空闲 UUV,提高分配效率。此外,相较于仅采用搜索时长为代价函数,在代价函数中引入边际代价和保守估计时长能够针对耗时长的区域最大限度缩短搜索时长,保证随着 UUV 数量的增加,全部区域搜索完成时长单调递减。     

Influence of Near Real-Time Green Vegetation Fraction Data on Numerical Weather Prediction by WRF over North China

The green vegetation fraction(GVF) can greatly influence the partitioning of surface sensible and latent heat fluxes in numerical weather prediction(NWP) models. However, the multiyear averaged monthly GVF climatology—the most commonly used representation of the vegetation state in models—cannot capture the real-time vegetation state well. In this study, a near real-time(NRT) GVF dataset generated from an 8-day composite of the normalized difference vegetation index is compared with the 10-yr averaged monthly GVF provided by the WRF model. The annual variability of the GVF over North China is examined in detail. Many differences between the two GVF datasets are found over dryland, grassland, and cropland/grassland mosaic areas. Two experiments using different GVF datasets are performed to assess the impacts of GVF on forecasts of screen-level temperature and humidity. The results show that using NRT GVF can lead to a widespread reduction of 2-m temperature forecast errors from April to October.Evaluation against in-situ observations shows that the positive impact on 2-m temperature forecasts in the morning is more distinct than that in the afternoon. Our study demonstrates that NRT GVF can provide a more realistic representation of the vegetation state, which in turn helps to improve short-range forecasts in arid and semiarid regions of North China. Moreover, our study shows that the negative effect of using NRT GVF is closely related to the initial soil moisture.     

The impacts of base level and lithology on fluvial geomorphic evolution at the tectonically active Laohu and Hasi Mountains,northeastern Tibetan Plateau

Previous researches had emphasized tectonic impacts on the fluvial system at the tectonically active areas, while the effects of lithology and local base level change have received relatively rare attention. Here we investigated fluvial landforms at different spatial scales, focusing on knickpoints and channel network reorganization from an area affected by the Haiyuan Fault in the northeastern Tibetan Plateau. The geomorphic indices, i.e., drainage pattern and χ anomalies, were calculated and investigated. The results show that two regional radial drainages formed around the Laohu and Hasi Mountains. Within the interior of the radial drainage, tributaries from the southeast side of the Laohu Mountain experienced near 180° direction change.We interpret this as the gradual drainage capture originating from the height difference(～190 m) of the local base level between the two catchments. Some tributaries from the Hasi Mountain show alternating gorges and broad valleys controlled by lithology.Besides, tectonic uplift and the lowering of base level(from the incision of the Yellow River) triggered an autogenic positivefeedback transition from parallel to dendritic drainage patterns. These observations suggest that base level change and lithology play a crucial role in landscape evolution, even in a tectonically active region.     

江东大桥建设对钱塘江水动力的影响

应用二维水流数学模型模拟了江东大桥建设前后大范围的流场,比较了建桥前后水位、流速、流向等水动力因子的变化,评价了大桥建设对工程区域水动力的影响,并与物理模型试验的结果进行对比,分析了结果的合理性。研究成果为大桥的设计和管理提供了技术依据。     

均匀流体和不均匀流体的形成机制:来自合成流体包裹体的证据

为详细了解流体的形成机制, 对系统的流体包裹体合成实验进行研究.研究表明, 在合成流体包裹体实验中, 广泛存在流体的均一化和沸腾作用; 流体的均匀与否, 与流体p-t轨迹在TP (H₂O)-CP(H₂O)-CP(NaCl-H₂O) 曲线的部位有密切的关系.p-t轨迹在曲线上部的流体为均匀流体, 反之则为沸腾流体.但也有例外, 如在溶解曲线上被主矿物捕获的流体.这为本次研究一定条件下流体的形成机制、探讨成矿作用提供了理论依据.      

我国"信息社会的地理学"关键研究领域综述

该文旨在描述十年来我国"信息社会的地理学"发展的大体轮廓。依据主题词选择、领域选择、期刊选择和论文选择的标准,以国内地理期刊上发表的96篇论文为研究对象,并按期刊、主题词、研究方法、研究区域进行分类分析,进而从7大领域综述我国"信息社会的地理学"的研究内容。研究发现,十年来我国"信息社会的地理学"呈现出研究不断深化、领域和主要内容全面化、研究方法和研究区域多样化的特点,据此探讨其研究趋势以引导未来的研究。     

洞庭湖区的泥沙淤积效应

以1951-2005 年长系列实测泥沙等资料为依据, 从泥沙淤积特性与资源环境之间的关系上, 探讨了洞庭湖区的泥沙淤积效应。研究表明: 由于洞庭湖区始终处于淤积状态, 加之人类活动影响, 导致了泥沙淤积循环演进的格局, 以至于使泥沙的灾害性效应与资源性效应 均在湖区得到充分的显示。主要表现在: ① 塑造了水体滩地、泥沙滩地、湖草滩地、芦苇滩地等类型滩地, 构成了湖泊巨系统的主体; ② 孕育或诱发了泥沙淤积→洲滩扩展、围垦→调洪功能下降、鱼类资源枯竭、生物多样性减少灾害链: 泥沙淤积→洲滩扩展→洪涝、水质污染; 泥沙淤积→植被洲滩浮涨→血吸虫病、害鼠致害灾害链; 泥沙淤积→洪溃决堤→土地沙 化灾害链。这些淤积型泥沙灾害链给湖区直接或间接地造成巨大的经济损失。③ 近55 年间, 泥沙塑造土地约98.13×10⁸hm², 人类合理开发利用洲滩资源获得了巨大的经济效益, 就地挖沙加高防洪大堤2~3 m, 累积土石方约55×10⁸ m³, 节省了购买大量原材料的开支。     

不同沉积微相致密储层的成岩响应及其控储机理 ——以鄂尔多斯盆地西部延长组为例

沉积微相是影响陆相致密油气储层发育的重要控制因素,不同微相的成岩响应和储层质量不同,制约了储层精细刻画与有利区预测工作.通过岩心、薄片、测井、孔渗、扫描电镜、XRD矿物分析、微米CT和压汞资料,识别了鄂尔多斯盆地西南部延长组三角洲—湖相致密储层8种沉积微相类型,刻画了不同微相在矿物组成、成岩作用、储层物性和孔隙结构方面...     

海洋中CO的研究进展

研究海洋中的CO具有重要的生物地球化学意义,因为它在控制大气中羟基自由基的浓度、参与全球碳循环进而影响全球气候变化等方面起着重要作用。对过去几十年来海洋中CO的研究进展进行评述。详细介绍了海洋环境中CO浓度的分布特征、通量、来源及去除途径。指出在这一研究领域我国和国际的差距以及一些有待于进一步研究的问题。