基于EM-MLC的高光谱图像方法识别海洋赤潮的研究

提出了一种综合利用小波变换高低通滤波数据的海洋赤潮识别方法.基于低通滤波数据,利用基于有限混合密度理论期望最大(EM)算法作为最大似然分类(MLC)参数估计的方法(EM-MLC)来进行赤潮、非赤潮和过渡水体的分类识别,并可进一步识别出不同优势种藻类引发的赤潮区域;利用高通滤波数据,可以分析赤潮爆发中非优势种藻类的信息,这就为引发赤潮的藻类种类的判断奠定了基础.通过实验验证了本方法可以有效地进行赤潮识别.同时,根据检测出的过渡水体区域信息,可以进行赤潮爆发前的预测.     

基于高光谱反射率的藻类水体基线荧光峰高度与叶绿素a浓度关系研究

采用现场实测和室内培养两种方式测定了甲藻、赤潮异弯藻、叉角藻赤潮和新月菱形藻、海洋蓝绿藻、叉鞭金藻、塔胞藻、扁藻和小球藻等非赤潮藻类光谱曲线。采用度量太阳激发的叶绿素荧光峰高度的基线荧光高度法 ,建立了不同藻类基线荧光高度与叶绿素浓度的关系。基线荧光高度法所用的 3个荧光高度波段分别为 6 6 5nm、6 80nm和86 5nm。在采用线性方程对不同藻类水体基线荧光高度与叶绿素浓度进行回归分析时 ,不同藻类产生了明显不同的结果。其中赤潮异弯藻、海洋蓝绿藻和甲藻为负相关 ,其余为正相关。在正相关的藻类中 ,小球藻最低 ,为 0 .4 6 92。结果偏差主要来自于两个方面 :一是藻类荧光峰位置变化影响 ;二是浮游植物红光和近红外波段高反射率的影响     

基于高光谱反射率的藻类水体基线荧光峰高度与叶绿素α浓度关系研究

采用现场实测和室内培养两种方式测定了甲藻、赤潮异弯藻、叉角藻赤潮和新月菱形藻、海洋蓝绿藻、叉鞭金藻、塔胞藻、扁藻和小球藻等非赤潮藻类光谱曲线。采用度量太阳激发的叶绿素荧光峰高度的基线荧光高度法，建立了不同藻类基线荧光高度与叶绿素浓度的关系。基线荧光高度法所用的3个荧光高度波段分别为665nm、680nm和865nm。在采用线性方程对不同藻类水体基线荧光高度与叶绿素浓度进行回归分析时，不同藻类产生了明显不同的结果。其中赤潮异弯藻、海洋蓝绿藻和甲藻为负相关，其余为正相关。在正相关的藻类中，小球藻最低，为0．4692。结果偏差主要来自于两个方面：一是藻类荧光峰位置变化影响；二是浮游植物红光和近红外波段高反射率的影响。     

一种基于GA-NSVM的自适应洛伦兹分峰拟合识别红外光谱吸收重叠峰的方法

提出一种基于遗传算法-非线性支持向量机的自适应洛伦兹分峰拟合识别红外光谱吸收重叠峰的方法。利用单质特征吸收线型的根本性差异,将混合物光谱分解为满足特征吸收线型的多个洛伦兹单峰,采用非线性支持向量机对多个拟合单峰进行多分类筛选确定特定目标组分的谱峰。采集了400个混合烷烃气体样本的红外光谱数据,论证了该方法在高相似分子结构的光谱识别分类的可行性。实验结果表明该方法能有效分离烷烃中甲烷、乙烷、丙烷的红外吸收单峰,具有良好的准确性和鲁棒性,模型参数的解释能力更强。该方法能够加速光谱检测技术在生物制药、食品化工、油气勘探等领域的应用,尤其是在含同系有机物混合物的分析及应用场合。     

基于表面反射率的赤潮卫星荧光线高度算法比较

采用现场实测和室内培养两种方式测定了甲藻、赤潮异弯藻和叉角藻等赤潮藻以及新月菱形藻、海洋蓝绿藻、叉鞭金藻、塔胞藻、扁藻和小球藻等非赤潮藻类光谱曲线。采用的各卫星(MERIS,GLI,MODIS)的荧光波段数据按照其中心波长,从实际测定的高光谱反射率曲线提取而来,并按照荧光高度的计算公式得到其荧光高度。同时,采用统计分析方法建立荧光高度与叶绿素浓度的关系。10种藻类水体的荧光线高度与叶绿素α的回归分析结果显示了良好的线性关系,但部分藻种出现了负相关的结果。因为在高叶绿素浓度即赤潮条件下,浮游植物在荧光波段(685nm附近)和近红外波段(700～750nm)复杂的光谱行为,使得采用星载遥感器的叶绿素荧光波段探测某些藻类的赤潮时会出现偏差。同时,由于不同藻类的荧光高度与叶绿素浓度的关系也不一致,本文建议针对单独的赤潮种类应建立特定的荧光算法。相关问题还需要在实测的基础上进行更深入的研究。     

基于紫外可见光谱法鉴别橙汁真伪

通过分析橙汁样品的紫外吸收光谱,建立了根据光谱特征吸收峰和主成分分析相结合,快速鉴别橙汁真伪的方法.橙汁在297nm和320nm处有特征吸收,根据该特征吸收可以鉴别样品中是否含有橙汁.根据400~550nm区间的特征峰可以判断样品中是否添加了β-胡萝卜素.对于无法通过特征吸收峰直观判断的样品,根据280~500nm光谱建立了主成分分析方法,可以鉴别是否掺杂其他果汁或食品添加剂.     

金属拉深件拉深过程微裂纹AE信号特征参数的优化及状态识别

本文通过对拉深件成型状态的声发射测试,进行了拉深过程AE特征参数信号的提取。对采集到的信号进行局域波分解后提取各IMF(Intrinsic Mode Function)的能量值作为初始特征参数,应用遗传算法对初始特征参数进行优化,生成最优特征参数。采用简单的马氏距离方法,将正常状态和微裂纹状态两种质量状态下的实验数据进行计算,比较两种状态下马氏距离的大小,取其中最小判别距离对应的状态为测试样本的状态类型。研究结果说明了该方法可以有效地识别出拉深件的微裂纹AE信号,从而判断出拉深件的初始裂纹状态,实现AE信号特征参数的优化及对金属拉深件成型质量状态的识别。     

依尔福胶卷FP4的防光晕浅析

用三种测定反射光晕的方法,对国外高清晰度黑白中速胶卷FP4进行了测试。该胶片微观性能中的一个重要因素是防光晕效果有明显改善;通过光谱感光度曲线和染料光谱吸收曲线证实:FP4防光晕层的染料光谱吸收峰与乳剂增感峰匹配良好,紫外区有很强的吸收峰,总的密度值也较高。为进行对比,引入了国内胶片HD—3作平行测试。     

片形FeSiAl磁粉复合材料的雷达波吸收机理

雷达波吸收材料已广泛应用于高频电子器件的抗电磁干扰和国防武器装备的雷达波隐身涂层.高性能的雷达波吸收材料要求其中的填充剂在GHz频段具有高的磁导率和合适的介电常数.片形FeSiAl磁粉由于良好的软磁性能,且在GHz频段具有较高的磁导率和相适应的介电常数,其复合材料被广泛用于高性能的雷达波吸收体.本工作制备了不同体积分数和不同厚度的片形FeSiAl磁粉/石蜡复合物,利用矢量网络分析仪测试了复合物在0.1～18 GHz的电磁参数,利用直接探测开路和短路状态下反射系数的方法研究了雷达波在空气-吸波涂层界面、吸波涂层-金属短路板界面的反射性能及反射损耗特性.结合开路和短路状态下反射系数的测量结果和相关模拟计算,直接确定了吸收峰峰值频率和吸波体厚度的依赖关系,进一步利用界面反射模型对吸收峰强度,吸收峰宽度做了深入的原理性讨论.     

质心识别及模糊判决方法在室内监控系统的应用

在有效提取特征参数后,结合具体的应用环境,提出一种模糊判决算法,依据运动物体的面积和运动物体的运动距离等特征参数,对目标进行识别报警判断,捕获并存储异常现象,最后发出报警信号.研究表明,通过异常识别及报警模糊判决方法可以使监控系统有效地消除日光灯频闪光线,部分运动阴影以及局部小扰动带来的区域干扰.     

海洋赤潮生物检测技术研究进展

赤潮是我国近海主要的多发性海洋生态灾害,加强赤潮生物检测技术研究,对于赤潮预报与治理工作具有重要的现实意义。本文综述了海洋水色遥感监测技术、赤潮生物光学检测技术及赤潮生物生物学分析技术的研究现状及其发展趋势。     

Successive wave crests in Gaussian seas

In this paper, following the theory of quasi-determinism of Boccotti [Boccotti P. Wave mechanics for ocean engineering. Oxford: Elsevier Science.], the necessary and sufficient conditions, for the occurrence of two successive wave crests of large heights in a gaussian sea, are given. It is proven that the first two-peaks part of the autocovariance function ψ(T) describes the structure of two successive-wave patterns. As a corollary, it is shown that the tail probability of the joint distribution of two successive wave crests is given by a bivariate Weibull distribution. The Weibull parameter is equal to . Here, is the abscissa of the second absolute maximum of the autocovariance function ψ(T). The analytical results are in agreement with Monte Carlo simulations. Finally, as an application, the maximum expected wave crest pressure in an undisturbed deep water waves is evaluated by taking into account the stochastic dependence of successive wave crests.     

基于深海声影区海底反射损失的地声参数反演方法

海底的声速、密度、衰减系数等地声参数,在声场预报、目标定位中十分重要。因地声参数原位测量和海底采样在深海中实施困难,需要寻找新的方法来获取地声参数。在深海声影区环境下,直达波会随着距离的增加而逐渐消失,一次反射波及多次反射波是对深海声影区声场起重要作用的多途信号。文章首先对声影区多途达到结构进行分析,利用多次比较法得到随掠射角变化的反射损失,并对海底地声参数进行反演,然后将反演的地声参数代入声场模型得到海底反射损失,将其与实验测量结果进行比较,结果吻合较好。并通过对反演过程的散点图和后验概率进行分析,证明了反演结果的可靠性。该方法可用于深海声影区的海底地声参数的反演。     

Microwave-absorbing properties of silver nanoparticle/carbon nanotube hybrid nanocomposites

Silver (Ag) nanoparticles fabricated by chemical reduction process were grafted onto the surface of carbon nanotubes (CNTs) to prepare hybrid nanocomposites. The Ag/CNT hybrid nanomaterials were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The Ag/CNT hybrid nanomaterials were then loaded in paraffin wax, and pressed into toroidal shape with thickness of 1 mm to evaluate their complex permittivity and complex permeability by scattering parameters measurement method in reflection mode using vector network analyzer. The reflection loss of the samples was calculated according to the transmission line theory using their measured complex permittivity and permeability. The minimum reflection loss of the Ag/CNT hybrid nanocomposite sample with a thickness of 1 mm reached 21.9 dB (over 99 % absorption) at 12.9 GHz, and also exhibited a wide response bandwidth where the frequency bandwidth of the reflection loss of less than ?10 dB (over 90 % absorption) was from 11.7 to 14.0 GHz. The Ag/CNT hybrid nanocomposite with thickness of 6 mm showed a minimum reflection loss of ~?32.1 dB (over 99.9 % absorption) at 3.0 GHz and was the best absorber when compared with the other samples of different thickness. The reflection loss shifted to lower frequency as the thickness of the samples increased. The capability to modulate the absorption band of these samples to suit various applications in different frequency bands simply by manipulating their thickness indicates that these hybrid nanocomposites could be a promising microwave absorber.     

Reflection of light in the vicinity of the Brewster angle from a multilayer system of ultrathin inhomogeneous dielectric films

An analysis of the influence of nanoscopically stratified dielectric overlayer on the reflection parameters of linearly polarized light from transparent substrates is carried out. The second-order formulas for characteristic Brewster angles are derived and their accuracy is estimated by using exact numerical methods for the solution of the inhomogeneous reflection problem. The possibilities are discussed for determining the parameters of nanometre-scale dielectric layers by means of characteristic reflection angles. A novel scanning angle differential reflectance method in the vicinity of the classical Brewster angle, whose sensitivity is in principle the same as that of ellipsometry, is developed.     

静水压力下高分子材料黏弹性动力学参数测量

提出测量静压下高分子材料黏弹性动力学参数方法。分别制作均匀实心覆盖层及圆柱空腔覆盖层样品,测量实心覆盖层复反射系数计算复纵波波数,测量圆柱空腔覆盖层复反射系数,结合圆柱空腔结构变形,利用圆柱管中轴对称波特征方程计算复剪切波波数,综合复纵波波数与复剪切波波数计算静压下复杨氏模量及复泊松比。对橡胶材料进行声管测试,分析、总结静压对黏弹性动力学参数影响规律。测量某吸声覆盖层静压下反射系数,并与用实测材料参数计算的反射系数进行比较,验证方法的可靠性。     

Optical properties of suspensions of organic and inorganic red pigments

Optical characterization of three red pigments, two organic and one inorganic, was studied in order to provide important and reliable parameters for research and applications. The pigments were C.I. Pigment Red 176, C.I. Pigment Red 57:1, and C.I. Pigment Red 101. All three pigments were used in their transparent form, that is, their radius of gyration was smaller than 250 nm. The particles were suspended in an apolar solvent and absorption, reflection, and scattering of the suspensions were measured by means of a single spectrophotometer and the effective complex refractive index was determined.     

High-efficiency reflective diffraction gratings in fused silica as (de)multiplexers at 1.55microm for dense wavelength division multiplexing application

We describe high-efficiency, high-dispersion reflection gratings fabricated in bulk fused silica illuminated by incident lights in the C + L bands as (de)multiplexers for dense wavelength division multiplexing (DWDM) application. Based on the phenomenon of total internal reflection, gratings with optimized profile parameters exhibit diffraction efficiencies of more than 90% under TM- and TE-polarized incident lights for 101-nm spectral bandwidths (1520-1620 nm) and can reach an efficiency of greater than 97% for both polarizations at a wavelength of 1550 nm. Without loss of metal absorption, without coating of dielectric film layers, and independent of tooth shape, this new kind of grating should be of great interest for DWDM application.     

Simulation and experimental validation of acoustic properties of hollow sphere structures

Customers nowadays regard the noise and vibration behavior as an essential product property. Cellular character materials, in particular hollow sphere structures, are predestined to absorb sound in a very efficient manner due to their cellular character. Depending on the constituent material, the geometric parameters like the diameter of the spheres, the thickness of the walls and the assembling schema of single spheres, the absorption coefficient can be reduced to very low levels. In contrast to other cellular materials, the frequency and bandwidth can actively be influenced by the variation of the above mentioned parameters. In order to predict the acoustic behavior of a structure, FE or CFD analyses are used as standard tools. In addition, there exist some parameter based models, e.g. the BIOT theory, which characterizes the absorption, transmission and reflection coefficients using a few macroscopic parameters. Within this contribution, the acoustic properties of hollow sphere structures are investigated by a so‐called virtual material laboratory GeoDict (by Math2Market GmbH, originally by the Fraunhofer Institute for Industrial Mathematics). The results for the absorption and reflection coefficients are compared to those gained by classical analysis methods and experiments based on Kundt's tube.