基于高光谱数据的荔枝SPAD值快速估测

通过分析荔枝叶片的反射光谱曲线与荔枝秋稍老熟阶段叶片SPAD-502 叶绿素计读数（SPAD 值）之间的关系,探索高光谱数据进行荔枝叶片SPAD 值估算的能力。研究4 类光谱变量,第1 类变量是其他文献中提出的光谱指数,第2 类变量是基于波段迭代算法进行波段优化后的新指数,第3 类变量是蓝边、黄边和红边（“三边”）的面积、位置、斜率,第4 类变量是二阶导数光谱波峰、波谷区间区间内光谱曲线的面积、最值、最值处波长。结果表明：一阶导数的蓝边斜率和光谱二阶导数提取的490~520 nm 范围内光谱数值之和与SPAD 值的相关程度也很高（r 分别为-0.834 和-0.856）;对于3 种光谱数据处理形式SNV 光谱（Standard Normal Variate,SNV）、FD 光谱（First Derivative,FD）和SD 光谱（Second Derivative,SD）,波段迭代算法优化后的最佳四波段双差值指数与SPAD 值相关性最好,其中（FD516－FD474）－（FD684－FD660）与SPAD 值的相关系数最高达到0.875,预测模型的确定系数达到0.747,RMSECV 为2.375。利用高光谱数据监测荔枝叶片SPAD 值是可行的。     

岷江上游山区聚落生态位垂直分异研究

以岷江上游山区聚落为研究对象,采用生态位的方法,利用遥感资料和GIS技术,提取岷江上游山区空间信息,定量研究山区聚落生态位影响尺度、人口密度及民族类型带谱垂直分异特征,并建立民族聚落生态位类型图谱。研究表明：聚落生态位地理半径随着海拔升高而增大,其数值介于300~600 m;相反,聚落生态位人口密度却随着海拔升高而递减,其数值介于200~630 人/km²;聚落生态位地理半径和人口密度的垂直分异特征,是山区居民长期适应山地环境的结果,与民族类型及其生计方式密切相关。在流域尺度上,岷江上游作为我国西南地区的一条民族廊道,聚落生态位民族类型空间格局具有典型的带谱特征：藏族和回族聚落生态位均处于河流干支流的上部,羌族聚落生态位对应于干旱河谷和V型河谷上部的低半山缓坡地带,汉族聚落生态位位于岷江上游入口处的河谷地带。     

Spatial and temporal variability of colored dissolved organic matter absorption properties in the Taiwan Strait

Spatial and temporal variability of the absorption properties of colored dissolved organic matter (CDOM) in the Taiwan Strait was investigated in summer (July to August of 2006) and winter (from December 2006 to January of 2007) seasons. The CDOM absorption coefficient at 280 nm (a 280 ) showed a decreasing trend from nearshore to offshore areas while the spectral slope coefficient parameter calculated between wavelengths 275-295 nm (S 275 295 ) showed an increase, indicative of decreasing aromaticity and molecular weight of the CDOM. The average a 280 in winter (1.47 ± 0.50 m 1 ) was significantly higher than in summer (1.10 ± 0.41 m 1 ), while the average S 275 295 in winter (26.7 ± 5.2 μm 1 ) was significantly lower than in summer (30.6 ± 5.5 μm 1 ), demonstrating clear seasonal variation in CDOM abundance and properties in the Taiwan Strait. A three-end- member conservative mixing model showed that local terrestrial CDOM inputs from several rivers along the western coast were small (<5%). However, the distribution of CDOM in the Taiwan Strait is mainly controlled by water mass movement [i.e., the Zhe-min Coastal Current (ZCC) and the Kuroshio Branch Current (KBC) in winter and the South China Sea Water (SCSW) in summer]. Biological activity was also an important factor affecting the distribution of CDOM in the offshore region in summer months.     

闪电放电过程的近红外光谱及温度沿放电通道的演化特征

利用无狭缝红外光谱仪, 获得山东地区闪电放电过程760~970 nm范围的近红外光谱.光谱特征分析得出: 近红外光谱主要是峰值电流之后、放电后期的辐射, 谱线主要是中性原子的贡献.首次讨论了放电后期的通道温度和光谱总强度沿放电通道的演化特征.结果表明, 通道温度较回击电流上升至峰值阶段降低, 约为16000 K; 不同闪电的光谱结构、通道温度差异不大, 反映了放电等离子体复合阶段的特性; 地闪通道的温度和光谱总强度沿放电通道略呈单调变化趋势, 接地点附近最大; 云闪通道的温度和光谱总强度沿放电通道非单调变化, 在通道的拐弯、分叉以及结点附近发生突变.     

Free‐field rotations during earthquakes: Relevance on buildings

Soil rotations around horizontal axes, during an earthquake, are studied through records collected by closely spaced arrays of strong motion accelerometers. The cross power spectrum of accelerations at nearby stations has been generally utilized to describe the spatial distribution of the motion. A number of cross spectra have been obtained during the training of these arrays. To take profit of these elaborations, a mathematical relation is established between the cross power spectrum and the power spectrum of the rotation. Rotation data presented by Liu et al, concerning 52 earthquake records collected at a single station in Taiwan, are compared with rotation data computed according to our procedure. The two series of data are suitably normalized to the peak horizontal acceleration. The data are shown in function of the distance from epicentre. The same ratio, computed according to our procedure, is in good agreement with the average value of these data. Direct measurements and the present approach have lead to evaluations of rotation higher than those predicted by mathematical investigations on the basis of the wave propagation theory, for comparable circumstances. The relevance of this input motion for relatively tall structures is examined, with reference to the structural effects that the horizontal motion concurrently provides. Meaningful will be ranked those effects of the order of magnitude of 20% or higher than those implied by the horizontal excitation. For understanding the relevance on building structures, the procedure has two areas of concern: 1) the coherence implicit in the cross power spectra, which depends on the interpolation process of the original records, collected in the arrays of instruments, and 2) the relative importance of the vertical to the horizontal input motion. As to the second item, the relevance of the rotation component on structures largely depends on the relative importance of the vertical to the horizontal input motion. When the records in an area a few km from the epicenter are considered, the response spectrum of vertical motion is comparable and in some records even higher, than that of horizontal motion, over the entire range of frequencies. This has been observed as well for the 2009 earthquake event of L'Aquila, Italy, and that at the Christchurch (New Zealand) 2011. When the response spectrum of vertical motion is comparable to that of horizontal motion, the effects of rotational motions on most engineering structures can be meaningful. Copyright © 2011 John Wiley & Sons, Ltd.     

Horizontal floor response spectra of base‐isolated buildings due to vertical excitation

A mechanism of horizontal floor response spectra amplification in the vicinity of higher modes' frequencies is investigated. It is demonstrated, by means of a simple two‐degrees‐of‐freedom model, that in the case of unsymmetrical superstructure, such amplification may occur because of the coupling between vertical excitation and horizontal response of the non‐isolated modes. This phenomenon is further illustrated by the results of analyses of a model of a nuclear plant. Copyright © 2011 John Wiley & Sons, Ltd.     

Conditional simulation of spatially variable seismic ground motions based on evolutionary spectra

This paper proposes a computational procedure for the conditional simulation of spatially variable seismic ground motions for long span bridges with multiple supports. The seismic ground motions, with part of their time histories measured at some supports, are regarded as zero‐mean nonstationary random processes characterized by predefined evolutionary power spectral density. To conditionally simulate unknown seismic ground motion time histories at other supports, the Kriging method is first described briefly for the conditional simulation of a random vector comprised of zero‐mean Gaussian variables. The multivariate oscillatory processes characterized by the evolutionary power spectral density matrix are then introduced, and the Fourier coefficients of the oscillatory processes and their covariance matrix are derived. By applying the Kriging method to the random vector of the Fourier coefficients and using the inverse Fourier transform, unknown nonstationary seismic ground motion time histories can be simulated. A numerical example is selected to demonstrate capabilities of the proposed simulation procedure, and the results show that the procedure can ensure unbiased time‐varying correlation functions, especially the cross correlation between known and unknown time histories. The procedure is finally applied to the Tsing Ma suspension bridge in Hong Kong to generate ground accelerations at its multiple supports using limited seismic records. Copyright © 2012 John Wiley & Sons, Ltd.     

An efficient approach for frequency-domain and time-domain hydrodynamic analysis of dam–reservoir systems

An efficient procedure is developed for the hydrodynamic analysis of dam–reservoir systems. The governing equations of hydrodynamic pressure in the frequency as well as time domain are derived in the framework of the scaled boundary finite element method. The water compressibility and absorption of reservoir sediments can be conveniently taken into consideration. By extending the reservoir to infinity with uniform cross-section, only the dam–reservoir interface needs to be discretized to model the fluid domain, and the hydrodynamic pressure in the stream direction is solved analytically. Several numerical examples including a gravity dam with an inclined upstream face and an arch dam with a reservoir of arbitrary cross-section are provided to demonstrate the computational efficiency and accuracy of the proposed method. Copyright © 2012 John Wiley & Sons, Ltd.     

辽东山地老秃顶子北坡植被类型及垂直带谱

基于沿海拔梯度的样方调查数据,运用TWINSPAN分类方法,科学划分老秃顶子北坡的森林群落类型,确定老秃顶子北坡植被垂直带谱,并对其种类组成和生活型谱进行系统研究。结果表明:⑴老秃顶子北坡植被垂直带谱由8个带组成,即海拔500~720m的蒙古栎+色木槭落叶阔叶林带,海拔720~820m的紫椴+色木槭落叶阔叶林带,海拔820~920m的臭冷杉+暴马丁香针阔混交林带,海拔920~1080m的臭冷杉+鱼鳞云杉暗针叶林带,海拔1080~1190m的枫桦+臭冷杉针阔混交林带,海拔1190~1280m的岳桦+簇毛槭落叶阔叶林带,海拔1280~1320m的矮灌化槭树+毛榛子山地灌丛带,海拔1320~1367m的小叶章+苔草山地草甸带。⑵老秃顶子北坡自山麓至山顶8个植被带的物种丰富度分别为43、27、33、39、54、45、47和34种,呈现出了在中等海拔高度拥有最高物种多样性的现象。⑶老秃顶子北坡在山麓~920m间,随着海拔的升高,群落中高位芽植物明显增多,地面芽植物明显减少;在海拔920m~山顶,随着海拔的升高,群落中高位芽植物明显减少,至山顶基本消失,而地面芽植物比例则由21.2%显著增加到山顶的79.4%。     

The chemical compositions of 10 new sub-DLAs and strong Lyman-limit systems at z≲ 1.5

We present chemical abundance measurements from medium-resolution observations of eight subdamped Lyα (sub-DLA) absorber and two strong Lyman-limit systems at   z ≲ 1.5  observed with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5-m Magellan II Clay telescope. These observations were taken as part of an ongoing project to determine abundances in   z _abs≲ 1.5  quasar absorption line systems focusing on sub-DLA systems. These observations increase the sample of Zn measurements in   z _abs≲ 1.5  sub-DLAs by ∼50 per cent. Lines of Mg  i , Mg  ii , Al  ii , Al  iii , Ca  ii , Mn  ii , Fe  ii and Zn  ii were detected and column densities were determined. Zn  ii , a relatively undepleted element and tracer of the gas-phase metallicity is detected in two of these systems, with  [Zn/H]=−0.05 ± 0.12  and  [Zn/H] > +0.86  . The latter one is however a weak system with   N _{H  I} < 18.8  , and therefore may need significant ionization corrections to the abundances. Fe  ii lines were detected in all systems, with an average Fe abundance of  〈[Fe/H]〉=−0.68  , higher than typical Fe abundances for DLA systems at these redshifts. This high mean [Fe/H] could be due to less depletion of Fe on to dust grains, or to higher abundances in these systems. We also discuss the relative abundances in these absorbers. The systems with high metallicity show high ratios of [Mn/Fe] and [Zn/Fe], as seen previously in another sub-DLA. These higher values of [Mn/Fe] could be a result of heavy depletion of Fe on to grains, unmixed gas, or an intrinsically non-solar abundance pattern. Based on cloudy modelling, we do not expect ionization effects to cause this phenomenon.