Seafloor sediment classification based on multibeam sonar data

The multibeam sonars can provide hydrographic quality depth data as well as hold the potential to provide calibrated measurements of the seafloor acoustic backscattering strength. There has been much interest in utilizing backscatters and images from multibeam sonar for seabed type identification and most results are obtained. This paper has presented a focused review of several main methods and recent developments of seafloor classification utilizing multibeam sonar data or/and images. These are including the power spectral analysis methods, the texture analysis, traditional Bayesian classification theory and the most active neural network approaches.     

利用地面气象观测资料确定对流层加权平均温度

地基GPS气象学的核心思想是通过垂直方向上GPS信号的湿分量延时确定出可降水分,而这两个物理量之间的转换必须使用对流层加权平均温度。本文首先讨论了上述转换估计中加权平均温度的几种逼近方式及其容许误差,然后利用香港地区的地面和高空气象资料,采用逐步回归分析方法,建立了适合香港地区的对流层加权平均温度计算公式,通过数据分析表明,这个公式有效地消除了在香港地区使用Bevis经验公式引起的系统误差,较好地满足了地基GPS气象应用中实时性和高精度的要求。本研究也充分表明,在地基GPS气象研究中,应该利用本地区的气象资料来确定适合本地区的估计对流层加权平均温度的经验公式。     

The inverse problem of optimal regulators and its application

1 IntroductionThe inverse problem of oPtirnal regulators is tofind a suitable quadratic ast function fOr a lineartime-invariable system with constant but unknowndisturbance so that the optimal control law canmeet the requirements of relative stability. Inl984,Juang and Lee presented a methed of OPtitnalPOle assignrnent in a sPecified region. In l986, Leeand Liaw presented a new methed for finding theweighting matrices Q and R of inverse regulatorswithout soution of the Ricatti equation. …     

基于大数据的世界文化遗产属性深度融合与分析

全球世界文化遗产本体及其环境数据是遗产价值认知和保护的基础,更是大数据时代遗产研究、展示以及可持续利用的依据.本文基于网络和地球大数据,利用自然语言处理、空间分析、领域知识图谱等技术,构建了包括领域知识图谱5万个节点,94万条三元组的全球世界文化遗产知识图谱,支持世界文化遗产的属性、节点关系查询以及图结构表达.基于知识...     

吉林省城市空间结构及地方中心城市腹地范围界定

将经济流与交通流相结合,运用社会网络分析法,分析了吉林省城市空间联系网络特征,选出吉林省地方中心城市,根据各市(县)间的综合联系程度界定地方中心城市的腹地。结果显示:①吉林省的经济、公路和铁路3个网络联系密度均偏低,长春市处于各网络中的核心地位,全省范围内各网络联系程度差异较大;②从综合联系网络来看,中部与其他地区的联系较为密切,东部和西部地区联系较弱;中部地区内的2个凝聚子群间联系有待加强,吉林省中部地区一体化发展任重道远,产业协调发展是未来的发展方向;南部地区内部的联系应进一步提升,促进南部轴线的发展;③结合吉林省47个市(县)的点度中心度、点入度和点出度值及实际发展需要,将长春市、吉林市、四平市、辽源市、通化市、延吉市和白城市作为吉林省的地方中心城市,其中,长春市的辐射带动能力最大,白城市最低;延吉市与敦化市应组团发展,成为东部地区的发展核心,共同带动东部地区发展;白城市应增强自身的中心性和辐射带动能力,充分发挥西部门户城市作用。     

Modelling and numerical simulation of two-phase debris flows

Gravity-driven geophysical mass flows often consist of fluid–sediment mixtures. The contemporary presence of a fluid and a granular phase determines a complicated fluid-like and solid-like behaviour. The present paper adopts the mixture theory to incorporate the two phases and describe their respective movements. For the granular phase, a Mohr–Coulomb plasticity is employed to describe the relationship between normal and shear stresses, while for the fluid phase, the viscous Newtonian fluid is taken into account. At the basal topography, a Coulomb sliding condition for the solid phase and a Navier’s sliding condition for the fluid phase are satisfied, while the top free surface is traction-free for both the phases. For the interactive forces between the phases, the buoyancy force and viscous drag force are included. The established governing equations are expressed in a curvilinear coordinate system embedded in a curvilinear reference basal surface, above which an arbitrary shallow basal topography is permitted. Taking into account the typical length characteristics of such geophysical mass flows, the “thin-layer” approximation is assumed, so that a depth integration can be performed to simplify the governing equations. The resulting strongly nonlinear partial differential equations (PDEs) are first simplified and then analysed for a steady state in a travelling coordinate system. We find the current model can reproduce the characteristic shape of some flow fronts. Additionally, a stability analysis for steady uniform flows is performed to demonstrate the development of roll waves that means instabilities grow up and become clearly distinguishable waves. Furthermore, we numerically solve the resulting PDEs to investigate general unsteady flows down a curved surface by means of a high-resolution non-oscillatory central difference scheme with the total variation diminishing property. The dynamic behaviours of the granular and fluid phases, especially, the effects of the drag force and the fluid bed friction are discussed. These investigations can enhance the understanding of physics behind natural debris flows.     

Kriging法在区域重力场插值中的适用性研究

由于重力观测网点位分布不均匀,密度不够,在精细刻画区域重力场变化时受到很大限制,因此需采用合理的插值算法。文中介绍Kriging插值算法和变异函数理论模型的基础上,结合陕西地区2011—2012年离散重力变化数据,利用最小二乘法得到各个理论变异函数模型的拟合参数,并将实验变异函数模型用于Kriging插值算法,同时综合考虑交叉验证精度统计、插值精度统计结果,以此来研究Kriging插值算法的适用性,研究结果表明:基于最小二乘法获得的球形模型、指数模型拟合参数精度高,高斯模型、对数模型精度最差;基于球形模型、指数模型的实验变异函数用于Kriging插值算法得到的插值结果精度最高、图像平滑自然、异常区明显,是一种适合陕西地区重力离散数据进行插值计算的有效算法。     

全球变暖趋缓研究进展

近十几年来,全球年平均表面温度上升趋势显示出停滞状态,即全球变暖趋缓,这引起了国际社会的广泛关注,同时也引发了对全球变暖的质疑,各国气候学家正努力就全球变暖趋缓的事实、原因及其可能影响展开研究。本文综述了目前国内外对全球变暖趋缓的研究结果。多数科学家认可近十几年来全球变暖停滞的事实,并认为太阳活动处于低位相、大气气溶胶（自然和人为）增加以及海洋吸收热量是变暖停滞的可能影响因子,其中海洋（尤其是700米以下的深海）对热量的储存可能是变暖停滞的关键。国际耦合模式比较计划第5阶段中的模式并未精确地描述各种有利降温影响因子的近期位相演变,因而其模拟的近期增暖趋势较观测偏强。由此推断,变暖停滞主要是自然因素造成的,并且预测变暖趋缓将在近几年或几十年内结束（依赖于太平洋年代际振荡的位相转变）,未来气温将仍主要受到温室气体增加的影响而表现出明显的上升趋势。因此,目前的全球变暖趋缓不大可能改变到本世纪末全球大幅度变暖带来的风险。本综述展望未来的研究热点包括:精确估算全球气温和海洋热含量的变率及其不确定性,海洋年代际信号（太平洋以及大西洋的年代际振荡）的转型机制,存储在深海的热量将在何时返回海洋表面及其对区域气候的潜在影响。     

花鲈稚、幼鱼生长的初步研究

对相同条件不同时期及相同时期不同环境条件下的花鲈稚、幼鱼的生长进行了比较。结果表明：威海羊亭养殖花鲈三月比一月、二月生长快，三月体重约是二月的9倍；不同环境条件下的花鲈生长差异极大，威海羊亭养殖花鲈体重分别是厦门、漳州和天然水域花钙体重的10．9、15．2和34．0倍。