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321.
Banana is one of the main economic agrotypes in Zhangzhou, Fujian Province. The multi-temporal ENVISAT ASAR data with different
polarization are used to classify the banana fields in this paper. Principal component analysis (PCA) was applied for six
pairs of ASAR dual-polarization data. For its large leaves, banana has high backscatter. So the value of banana fields is
high and shows very bright in the 1st component, which makes it much easier for banana fields extraction. Dual-polarization
data provide more information, and the VV and VH backscatter of banana show different characters with other land covers. Based
on the analysis of the radar signature of banana fields and other land covers and the 1st component, banana fields are classified
using object-oriented classifier. Compared to the field survey data and ASTER data, the accuracy of banana fields in the study
area is 83.5%. It shows that the principal component analysis provides the useful information in SAR images analysis and makes
the extraction of banana fields easier.
Supported by the Program for New Century Excellent Talents in University (NCET-05-0573), Fujian Science and Technology Project
(No.2006I0018), the Science Project of the Education Department of Fujian Province(No. 2006F5022). 相似文献
322.
This paper systematically studies the statistical diagnosis and hypothesis testing for the semiparametric linear regression model according to the theories and methods of the statistical diagnosis and hypothesis testing for parametric regression model.Several diagnostic measures and the methods for gross error testing are derived.Especially,the global and local influence analysis of the gross error on the parameter X and the nonparameter s are discussed in detail;at the same time,the paper proves that the d... 相似文献
323.
Geochemistry of pore waters from the Xisha Trough, northern South China Sea and their implications for gas hydrates 总被引:2,自引:0,他引:2
Shao-Yong Jiang Tao Yang Lu Ge Jing-Hong Yang Hong-Fei Ling Neng-You Wu Jian Liu Dao-Hua Chen 《Journal of Oceanography》2008,64(3):459-470
This paper reports all available geochemical data on sediments and pore waters from the Xisha Trough on the northern continental
margin of the South China Sea. The methane concentrations in marine sediments display a downhole increasing trend and their
carbon isotopic compositions (δ
13C = −25 to −51‰) indicate a thermogenic origin. Pore water Cl− concentrations show a range from 537 to 730 mM, and the high Cl− samples also have higher concentrations of Br−, Na+, K+, and Mg2+, implying mixing between normal seawater and brine in the basin. The SO4
2− concentrations of pore waters vary from 19.9 to 36.8 mM, and show a downhole decreasing trend. Calculated SMI (sulfate-methane
interfaces) depths and sulfate gradients are between 21 and 47 mbsf, and between −0.7 and −1.7 mM/m, respectively, which are
similar to values in gas hydrate locations worldwide and suggest a high methane flux in the basin. Overall, the geochemical
data, together with geological and geophysical evidence, such as the high sedimentation rates, high organic carbon contents,
thick sediment piles, salt and mud diapirs, active faulting, abundant thermogenic gases, and occurrence of huge bottom simulating
reflector (BSR), are suggestive of a favorable condition for occurrence of gas hydrates in this region. 相似文献
324.
Dissolved inorganic carbon (DIC) and its carbon isotopic composition in sediment pore waters from the Shenhu area,northern South China Sea 总被引:2,自引:0,他引:2
Tao Yang Shao-Yong Jiang Jing-Hong Yang Ge Lu Neng-You Wu Jian Liu Dao-Hua Chen 《Journal of Oceanography》2008,64(2):303-310
The Shenhu area is one of the most favorable places for the occurrence of gas hydrates in the northern continental slope of
the South China Sea. Pore water samples were collected in two piston cores (SH-A and SH-B) from this area, and the concentrations
of sulfate and dissolved inorganic carbon (DIC) and its carbon isotopic composition were measured. The data revealed large
DIC variations and very negative δ
13C-DIC values. Two reaction zones, 0–3 mbsf and below 3 mbsf, are identified in the sediment system. At site SH-A, the upper
zone (0–3 mbsf) shows relatively constant sulfate and DIC concentrations and δ
13C-DIC values, possibly due to bioturbation and fluid advection. The lower zone (below 3 mbsf) displays good linear gradients
for sulfate and DIC concentrations, and δ
13C-DIC values. At site SH-B, both zones show linear gradients, but the decreasing gradients for δ
13C-DIC and SO4
2− in the lower zone below 3 mbsf are greater than those from the upper zone, 0–3 mbsf. The calculated sulfate-methane interface
(SMI) depths of the two cores are 10.0 m and 11.1 m, respectively. The depth profiles of both DIC and δ
13C-DIC showed similar characteristics as those in other gas hydrate locations in the world oceans, such as the Blake Ridge.
Overall, our results indicate an anaerobic methane oxidation (AMO) process in the sediments with large methane flux from depth
in the studied area, which might be linked to the formation of gas hydrates in this area. 相似文献
325.
326.
327.
Biological invasions represent one of the significant components of global change. A comparative study of invaders and co-occurring natives is a useful approach to gaining insights into the invasiveness of exotic plants. Spartina alterniflora, a C4 grass, is a widespread invader in the coastal wetlands in China and other regions of the world. We conducted a comparative study of S. alterniflora and native C3 species, Phragmites australis and Scirpus mariqueter, in terms of their gas exchange and efficiencies in resource utilization. We tested the hypothesis that S. alterniflora has growth-related ecophysiological advantages over the natives in its non-native range, which result in its rapid growth and enhance its invasiveness. Photosynthesis, leaf area index (LAI), specific leaf area (SLA), and the efficiency of resource use (light, water, and nitrogen) were examined monthly for eight months in 2004. Overall, S. alterniflora had greater LAI, higher maximal net photosynthetic rate (Amax), and longer growing season than those of the native species. On average, the efficiencies of S. alterniflora in light, water, and nitrogen utilization were respectively 10.1%, 26.1%, and 33.1% higher than those of P. australis, and respectively 70.3%, 53.5%, 28.3% higher than those of S. mariqueter. However, SLA of S. alterniflora was significantly lower than those of P. australis and S. mariqueter. Although there was no general pattern in the relationship between invasiveness and plant photosynthetic types, in this study, most of the ecophysiological characteristics that gave S. alterniflora a competitive advantage in the Yangtze River estuary were associated with photosynthetic pathways. Our results offer a greater understanding of the relationship between invasiveness and plant photosynthetic type. Our results also indicate that LAI and the length of the photosynthetic season, which vary with habitats, are also important in invasion success. 相似文献
328.
船载ADCP资料的潮流分离方法在厦门港断面重复走航中的应用 总被引:1,自引:0,他引:1
本文运用Candela等提出的潮流分离方法,选用高斯函数作为基函数,采用Matlab程序,首次对厦门港嵩鼓水道的船载ADCP断面重复走航资料进行潮流分离计算.通过对14个计算点的Candela方法计算结果与引进差比关系准调和分析方法计算结果的分析比较可见:(1)两种方法计算所得余流在大、小潮的相关系数分别为0.9882和0.8521,余流相对误差在大、小潮分别为0.065和0.150,而所得余流方向在大、小潮的相关系数分别为0.9982和0.9865,余流方向相对误差在大、小潮分别为0.023和0.027.两种方法计算的余流及其方向的相关性很高(在样本数为14,置信度为α=1%时,相关系数大于0.6610,结果是可信的),而平均相对误差也很小.(2)对14个计算点的M2、S2、K1、O1、M4和MS4等6个分潮的计算结果(共有84个样本数据)进行分析比较,两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的相关系数分别为0.9838、0.8960和0.2335,而在小潮的相关系数分别为0.9656、0.7555和0.2209.这两种方法计算所得6个分潮的长轴、长轴方向和短轴在大潮的平均相对误差分别为0.375、0.071和0.753,而在小潮的平均相对误差分别为0.287、0.254和0.845.两种方法计算的分潮长轴及其方向的相关性很高(在样本数为84,置信度为α=1%时,相关系数大于0.283,结果是可信的).相应的分潮长轴的相关性略低,但是在样本数为84,置信度为α=5%时,相关系数均大于0.217.可认为在置信度为α=5%时,计算结果是可信的,而平均相对误差则略显较大.综上所述,我们认为采用Candela等的方法对船载ADCP断面重复走航资料进行潮流分离计算是可行的. 相似文献
329.
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330.
基于非线性动力学模型的旅游生态容量分析 总被引:1,自引:0,他引:1
近年来,大量增加的游客给景区的旅游生态容量带来了较大的压力,矛盾日渐突出。为了实现景区的环境保护与可持续发展,研究游客活动量与景区旅游生态容量之间的关系是十分必要的。本文从非线性动力学观点出发,构建二者非线性动力学模型,并进行平衡态分析。研究结果表明:(1)系统要达到可持续发展,必须建立在景区环境的自我更新能力及人工恢复程度之和大于外界污染水平,且游客的增长率必须保持在较低水平的基础上;(2)景区旅游生态容量的承载力是有限的,所能容纳的游客也是有限的,超过一定的限度就会引起生态系统失衡。采取严格控制游客量,加强对景区内外环境的保护和改善、提升游客素养等措施,对于系统的协调发展至关重要。 相似文献