马尾松针叶光谱特征与其叶绿素含量间关系研究

以马尾松针叶野外高光谱数据为基础,分析了马尾松光谱变化,构建或借助不同光谱特征参数,在理论和实践分析的基础上,建立了马尾松针叶叶绿素含最与光谱反射率及9个特征参数之间的关系.研究结果表明:(1)马尾松叶绿素含量在527,703,1 364及1 640 nm四个波长附近,与其反射率具有较好的线性关系,为马尾松遥感监测在波段选择上提供了依据;(2)红边位置、红边平均反射率、红边位置附近平均反射率、红边斜率、红边面积、红谷吸收深度、绿峰反射高度、红边归一化植被指数、红边植被胁迫指数等9个马尾松反射光谱特征参数均与叶绿素含量间存在指数函数关系,相关系数绝对值在0.5～0.7之间;(3)采用9个光谱特征参数建立了马尾松针叶叶绿素含量预测模型,且所建立的基于高斯核函数变换的偏最小二乘回归模型对叶绿素含量的预测精度远远大于传统线性回归模型,模型的均方误差为0.008 8,平均绝对百分误差为0.761 7%.     

多孔泡沫镍分液隔板的气液分离性能研究

本文通过水与空气模拟两相流来探究多孔泡沫镍分液隔板的分液性能,测试不同工况下分液隔板分液能力的大小,总结分液隔板分液性能随入口空气流量以及水流量的变化规律,并且用达西渗流定律对多孔材料的渗流率进行了分析,从而对分液隔板的设计起到一定的指导意义。     

区间偏最小二乘结合差分进化算法应用于鱼粉近红外光谱波长筛选

蛋白质含量是评价鱼粉质量的重要指标,该文采用近红外(NIR)光谱分析技术结合特征筛选方法建立了鱼粉蛋白质含量的快速定量分析模型,并结合区间偏最小二乘(iPLS)和二进制变异策略的差分进化(DE)算法建立了区间偏最小二乘差分进化(iPLS-DE)的波长筛选优化模式,对鱼粉NIR光谱数据进行特征波长筛选。iPLS-DE通过调试iPLS中等分子区间的数量,优选出9个最优特征波段,再采用二进制变异策略的DE算法在最优特征波段内筛选离散特征波长组合,最后根据模型的评价指标确定iPLS-DE优选模型并与iPLS优选模型进行比较。结果表明,将鱼粉全谱等分为5个子区间时,iPLS-DE筛选出50个离散特征波长建立的优选模型对测试集样品的预测均方根误差和相对分析误差分别为1.033%和4.058,而iPLS优选模型对测试集样品的预测均方根误差和相对分析误差分别为1.131%和3.855。表明iPLS-DE方法能够有效地提高NIR光谱分析模型对鱼粉蛋白质定量检测的预测能力。     

课外练习

初一年级1.已知:x=2000/2001,y=2001/2002,试比较x与y的大小.     

Dependence of Structure and Haemocompatibility of Amorphous Carbon Films on Substrate Bias Voltage

Tetrahedral amorphous hydrogenated carbon (ta-C:H) films on Si(lO0) substrates were prepared by using a magnetic-field-filter plasma stream deposition system. Samples with different ratios of sp^3-bond to sp^2-bond were obtained by changing the bias voltage applied to the substrates. The ellipsometric spectra of various carbon films in the photon energy range of 1.9-5.4eV were measured. The refractive index n and the relative sp^3 C ratio of these films were obtained by simulating their ellipsometric spectra using the Forouhi-Bloomer model and by using the Bruggeman effective medium approximation, respectively. The haemocompatibility of these ta-C:H films was analysed by observation of platelet adhesion and measurement of kinetic clotting time. The results show that the sp^3 C fraction is dependent on the substrate bias voltage, and the haemocompatibility is dependent on the ratio of sp^3-bond to sp^2-bond. A good haemocompatibility material of ta-C:H films with a suitable sp^3 C fraction can be prepared by changing the substrate bias voltage.     

巧用特殊法 妙解课本题

根据题目条件的信息,选用恰当的化简技巧,是解决课本二次根式题的关键.一、变换所求,以简驭繁例1已知x=1/2(7~(1/2)+5~(1/2)),y=1/2(7~(1/2)-5~(1/2)),求x2-xy+y2的值.解当x=1/2(7~(1/2)+5~(1/2)),y=1/2(7~(1/2)-5~(1/2))时,有x-y=5~(1/2),xy=1/2.∴原式=(x-y)2+xy=(5~(1/2))2+1/2=11/2.二、化简变形,化难为易例2已知x=(3~(1/2)+2)/(3~(1/2)-2),y=(3~(1/2)-2)/(3~(1/2)+2),求     

Growth Mechanism of Vertically Aligned Ag（TCNQ） Nanowires

Highly oriented Ag(TCNQ) nanowires have been prepared on Si(111) wafer at 1O0℃ by the vapour-transport reaction between silver and TCNQ without any other catalyst. X-ray diffraction analysis shows that the composition and crystal structure of the obtained nanostructure were Ag(TCNQ) crystalline. Most Ag(TCNQ) nanowires were grown uniformly and vertically on the substrate with diameters ranging from 50 to 30Onto and the lengths measuring from 2 to 50μm by scanning electron microscopy. Ag particles were observed on the substrate from pure thin Ag film heated under the same conditions as used in synthesizing the nanowires. Nucleation and short Ag(TCNQ) nanowires were prepared by controlling the reaction time, providing direct evidence of the growth mechanism in a nanometre scale. The growth process was explained according to the vapour-liquid-solid model. The gradient of temperature and the densely distributed Ag particles may contribute to the vertically aligned growth. These results will be helpful for the controllable synthesis of Ag(TCNQ) nanowires.     

数字竞赛题的几个新知识

在近几年的数学竞赛试题中,出现了一些新亮点——以新知识为背景的题目.它通过介绍一种课本以外的知识,现学现解,以体现同学们分析、解决问题的能力.下面以2004年“创新杯”数学竞赛题为例,供大家参考.     

2-（二硝基亚甲基）-4，5-咪唑烷二酮的反应研究

2-(二硝基亚甲基)-4，5-咪唑烷二酮(1)是1998年首次报道的一个新化合物，是Latypov等在探索合成低感高能炸药1，1-二氨基-2，2-二硝基乙烯(FOX-7)的过程中得到的一个重要中间体，它去掉羰基开环即得FOX-7，     

铁路围岩分类专家系统中的不确定性推理问题

本文将专家的经验分类标准与需要评判的围岩用模糊数学中择近原则的方法进行模糊模式识别,对专家评判中有关因素采用因素关系图描述,将被评定的围岩视为论域上的一个模糊子集,把推理过程抽象为多维论域上确定隶属度的过程,进而提出用连续隶属函数进行围岩类别的模糊推理。最后,以隶属度的形式,给出评判的分类结果。