富营养化湖泊典型水华蓝藻的固有光学特性

固有光学特性是水体光学特性的重要内容,掌握富营养化湖泊水体内典型水华蓝藻的固有光学特性,是开展不同水华蓝藻遥感识别的理论基础.利用AC-S吸收衰减仪、BB9后向散射仪,通过实验室纯藻培养,研究微囊藻（Microcystis）、鱼腥藻（Dolichospermum）和束丝藻（Aphanizomenon）3种典型水华蓝藻的固有光学特性,并探讨色素浓度、色素占比以及藻类等效粒径对不同水华蓝藻固有光学特性的影响.结果表明,3种典型水华蓝藻的吸收光谱曲线均具有440、620和675 nm吸收峰,微囊藻620和675 nm的比吸收系数最大,鱼腥藻440 nm处的比吸收系数最大;束丝藻单位色素浓度的散射和后向散射能力最高,鱼腥藻次之,微囊藻最低;固有光学特性影响因子分析表明,色素浓度和藻蓝素占比是影响3种水华蓝藻固有光学特性的主要因素.3种蓝藻的吸收系数、散射系数以及鱼腥藻、束丝藻的后向散射系数均随着色素浓度（叶绿素a或藻蓝素）的增加而增大;当蓝藻中藻蓝素占比增加时,3种蓝藻的单位色素浓度的后向散射系数逐渐下降;而藻细胞粒径与固有光学特性之间并未表现出很好的相关性.因此,3种水华蓝藻单位色素浓度的固有光学特性将为典型水华蓝藻的遥感识别提供重要的理论基础和数据支持.     

太湖水体散射特性及其空间分异

利用Wetlabs公司研制的AC-S和BB9于2006年10月24目至11月2目对太湖水体的散射系数和后向散射系数进行了测量,在此基础上建立了太湖水体散射系数与后向散射系数之间的关系模型。用2种曲线函数模拟,即在蓝光波段使用S形曲线模型,在绿光和红光波段使用逆函数模型,各模型的MAPE和RMSE变化范围分别为0.027-0.156m^-1、0.005-0.050m^-1,模型整体预测精度都较高。研究发现后向散射系数与散射系数的空间分异现象明显,北部梅梁湾、湖心区、西部及西南部水域散射较强,而东太湖、胥口湾等东部水域的散射相对较弱。     

非均匀正交各向异性特征参数地震散射反演方法研究

在长波长假设条件下,水平层状地层中发育一组垂直排列的裂缝构成了等效正交各向异性介质.各向异性参数与裂缝弱度参数的估算有助于非均匀各向异性介质的各向异性特征描述,而弹性逆散射理论是非均匀介质参数反演的有效途径.基于地震散射理论,我们首先推导了非均匀正交介质中纵波散射系数方程,并通过引入正交各向异性特征参数,提出了一种新颖的正交各向异性方位弹性阻抗参数化方法.为了提高反演的稳定性与横向连续性,我们发展了贝叶斯框架下的正交各向异性方位弹性阻抗反演方法,同时考虑了柯西稀疏约束正则化和平滑模型约束正则化,最终使用非线性的迭代重加权最小二乘策略实现了各向异性特征参数的稳定估算.模型和实际资料处理表明,反演结果与测井解释数据相吻合,证明了该方法能够稳定可靠地从方位叠前地震资料中获取各向异性特征参数,减小参数估算的不确定性,为非均匀正交介质的各向异性预测提供了一种高可靠性的地震反演方法.     

基于非线性薛定谔方程的波浪预报方法研究

为探索海浪波面信息的实时预报方法,以三阶非线性薛定谔(NLS)方程的逆散射变换求解为基础,通过理论推导,给出了一种由实测波高时历数据计算其NLS方程本征值的方法,进一步实现了对波浪包络时空演变的预报。通过预报结果与实测波列的比对,验证了方法的有效性和准确性。该方法可为船舶或海上平台的大浪预警,以及为大波浪中海上作业寻找窗口期等提供一条新的技术途径。     

北半球夏季中高纬海洋声散射层分布研究

利用第八次北极调查走航ADCP后向散射强度数据,结合太阳高度、海冰密集度和实测水体环境参数数据,统计分析了中高纬海洋声散射层的时空变化特征。结果表明,纬度越高,声散射层在海表滞留时间越短,即使在极昼期间及全海冰覆盖海域,虽然其迁移幅度和后向散射强度减弱,但仍受太阳高度变化影响,且二者具有较强的时序相关性;在北极中央海域,不仅声散射层迁移活动较弱,且出现无明显散射层的情况,可能是因为该海域浮游动物和鱼类聚集度相对较低且迁移活动微弱,超出了本文所用ADCP的探测精度范围;从鄂霍次克海至白令海西南海域,往返ADCP数据均显示有两个后向散射强度上高下低,但垂直迁移时间同步的声散射层,且二者间距随纬度增加而逐渐减小并合为一体,这可能是由不同生活习性的海洋生物造成的。     

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter(SPM) within the water column.However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scienti?c cruise in July 2016, in situ ef fective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into(1) small particles(<32 μm),(2) medium particles(32–256 μm) and(3) large particles(>256 μm). Large particles and medium particles dominated the total volume concentrations(VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values(<0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values(0.1–1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles <32 μm in?uenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic ?ne particles, while large particles were mucus-bound organic aggregates or individual plankton.The vertical distribution of coarser particles was clearly related to water strati?cation. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of?ne material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer.Abundant large biogenic particles were present in both surface and middle layers.     

基于权重散射特征的FSVM算法在极化SAR影像分类中的应用

提出了一种基于权重散射特征的模糊支持向量机的极化SAR数据监督分类方法。首先,对极化SAR数据进行H/SPAN/A/α散射特征提取;其次,根据样本可分离度设置最佳散射特征权重参数C,得到最优分类输入数据(H/6SPAN/A/α);最后,利用FSVM算法对数据进行监督分类。实验结果证明,所提出的FSVMH/6SPAN/A/α分类结果优于FSVM-H/SPAN/A/α。     

长江口及其邻近海域悬浮颗粒物浓度和粒径的时空变化特征

长江口是典型的高浊度河口,长江口及其邻近海域悬浮颗粒物（suspended particulate matter,SPM）浓度跨度大,泥沙过程活跃、复杂。2015年7月9-20日（洪季）和2016年3月7-19日（枯季）,使用OBS和LISST分别测定了该区域99个和89个站位的SPM浊度、光衰减系数、总体积浓度、平均粒径和粒径谱等参数;同时通过现场过滤测定了各站位表、中、底3层的SPM质量浓度以及典型站位SPM中颗粒有机碳（particulate organic carbon,POC）的δ13C、颗粒氮（particulate nitrogen,PN）的δ15N以及POC/PN摩尔比值。结果表明,浊度、光衰减系数、总体积浓度等3个参数均与SPM质量浓度显示出了显著的正相关关系。研究区域SPM平均粒径一般表层大于底层、枯季大于洪季;长江淡水端元输出的SPM粒径枯季也明显大于洪季。具有相似粒径谱特征的SPM可以通过测定δ13C和δ15N值来进一步区分其来源和组成。SPM质量浓度和总体积浓度等参数结合还可以计算SPM有效密度,用以了解研究区域SPM的沉降过程。结果表明两个季节SPM有效密度和粒径之间显示出了显著的负相关关系,说明枯季长江输出的SPM由于粒径大、密度小、沉降速度低,加之强烈的垂直混合和口门拦门沙附近的再悬浮,随着环流可能到达研究区域北部的最东端;而洪季长江输出的SPM由于粒径小、密度大、沉降速度高,在口门附近快速沉降。     

Scattering of elastic waves by a plane crack of finite width in a transversely isotropic medium

This work presents a numerical algorithm for solving crack scattering in a transversely isotropic medium whose symmetry axis is perpendicular to the crack surface. The crack is modelled as boundary discontinuities in the displacement u and the particle velocity v, of the stresses [κu+ζv], where the brackets denote discontinuities across the interface. The specific stiffness κ introduces frequency-dependence and phase changes in the interface response and the specific viscosity ζ is related to the energy loss. The numerical method is based on a domain decomposition technique that assignes a different mesh to each side of the interface, that includes the crack plane. As stated above, the effects of the crack on wave propagation are modelled through the boundary conditions, that require a special boundary treatment based on characteristic variables. The algorithm solves the particle velocity–stress wave equations and two additional first-order differential equations (two-dimensional case) in the displacement discontinuity. For each mesh, the spatial derivatives normal to the interface are solved by the Chebyshev method, and the spatial derivatives parallel to the interface are computed with the Fourier method. They allow a highly accurate implementation of the boundary conditions and computation of the spatial derivatives, and an optimal discretization of the model space. Moreover, the algorithm allows general material variability. © 1998 John Wiley & Sons, Ltd.     

基于原位激光粒度仪(LISST)的悬浮体平均粒径计算方法对比研究

根据2012年夏季和2016年冬季在南黄海中部利用原位激光粒度仪(laser in situ scattering and transmissometry,LISST)进行调查获得的实测数据,对两种平均粒径计算方法的结果进行比较研究,并对产生差别的原因进行分析。结果表明:无论在夏季和冬季,在温度跃层以上粒度分布以粗颗粒为主,两种计算方法差值较小,可以相互替代。在温盐跃层以下层位,细颗粒组分增加,导致二者计算差值变大。端元分析表明较高的平均粒径值倾向于造成平均粒径差值增大。矩值法强调了粗颗粒组分的贡献,而平均粒级法对细颗粒组分的贡献更加敏感,后者是更适用于将LISST观测数据应用于陆架海区现代沉积环境研究的粒径参数计算方法。本文为使用LISST在陆架海区进行现代沉积过程研究提供了参考。