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21.
现代黄河三角洲粉土触变性研究及其应用 总被引:5,自引:0,他引:5
通过对现代黄河三角洲砂质粉土和粉质粘土触变性的对比试验研究,阐述了黄河口粉土的触变性。试验结果对解释粉土的失稳机制、解决工程地基的稳定性和防止地质灾害等具有重要的现实意义。 相似文献
22.
Submersible pressure hulls with fiber-reinforced multilayer-sandwich constructions have been developed in recent years as substitutes for classical metallic ring-stiffened pressure hulls. This study aims to optimize the design of filament-wound multilayer-sandwich submersible pressure hulls, taking into consideration the shell buckling strength constraint, the angle-ply laminated facing failure strength constraint and the low-density isotropic core yielding strength constraint under hydrostatic pressure using the hybrid genetic algorithm (HGA). The thickness of the facing, the thickness of the core layer, the orientation angle of the fibers in the facings and the shear modulus of the core material are taken as design variables. A sensitivity analysis is performed to study the effects of the operational depths and the hull shell geometry parameter, the length-to-diameter ratio (L/D), on the optimal design of filament-wound multilayer-sandwich submersible pressure hulls with graphite/epoxy, glass/epoxy and boron/epoxy composite facings. The results reveal that the optimal weight of various sandwich pressure hulls increases linearly with the operational depth, but it is almost unchanged as the geometry paramter. Furthermore, Graphite/Epoxy is the best choice for the material of the facings in a light-weight design. With reference to wall design, Boron/Epoxy is the best choice for the material of the facing at shallow depths, but Graphite/Epoxy is the best choice at extreme depths. Results of this study provide a valuable reference for designers of underwater vehicles. 相似文献
23.
K. S. Rao Y. S. Rao H. K. Al Jassar 《Journal of the Indian Society of Remote Sensing》2008,36(2):123-136
Spaceborne Imaging Radar (SIR-C) data acquired over Gujarat, India in 1994 were processed and analysed using differnet techniques
applicable to polarimetric SAR data such as polarization signatures, polarization index, decomposition of the signal and polarization
phase difference and limited groundtruth data. It has been observed that multi-frequency polarimetric data enhances the potential
of retrieving geo-physical parameters. The polarization signatures are found to vary with the nature of the target. Target
decomposition of the returned signal will be useful for the classification of various features. Polarization Phase Difference
(PPD) gives good information about the vegetation parameters. 相似文献
24.
地震瞬时属性分析技术在岩溶勘查中的应用 总被引:3,自引:1,他引:2
介绍地震瞬时属性分析技术的原理及处理方法,分别对岩溶在地震剖面、瞬时振幅剖面、瞬时频率剖面、瞬时相位剖面上的表现特征作了说明.并结合实际资料进行多参数解释,进而确定地下岩溶的发育情况、分布范围和规模,同时对异常进行钻井验证,结果表明,地震瞬时属性分析技术比常规地震处理方法能更好地排除干扰,确定岩溶异常. 相似文献
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27.
This paper introduces a new method for GPS signal acquisition, which is based on the repeatability of successive code phase
measurements and the M-of-N search algorithm. The performance of the proposed method in terms of probability of signal detection
is similar to that of traditional methods, except that the calculation of the probability of detection does not rely on the
noise distribution or the Carrier-to-Noise ratio (C/N0). The code phase repeatability-based method is presented along with equations for probability of detection and probability
of false detection. If the distribution of the noise is known, it also provides an estimate of the C/N0. The proposed method is illustrated for coherent and non-coherent acquisition and C/N0 estimation. 相似文献
28.
29.
Mirdita Zone ophiolites and associated sediments in Albania reveal Neotethys Ocean origin 总被引:1,自引:1,他引:0
Hans-Jürgen Gawlick Wolfgang Frisch Lirim Hoxha Paulian Dumitrica Leopold Krystyn Richard Lein Sigrid Missoni Felix Schlagintweit 《International Journal of Earth Sciences》2008,97(4):865-881
The Mirdita Ophiolite Zone in Albania is associated with widespread mélanges containing components of up to nappe-size. We
dated matrix and components of the mélange by radiolarians, conodonts, and other taxa. The components consist of radiolarites,
pelagic limestones and shallow-water limestones, all of Triassic age, as well as ophiolites. Triassic radiolarite as a primary
cover of ophiolite material proves Middle Triassic onset of Mirdita ocean-floor formation. The mélange contains a turbiditic
radiolarite-rich matrix (“radiolaritic flysch”), dated as Late Bajocian to Early Oxfordian. It formed as a synorogenic sediment
during west-directed thrusting of ophiolite and sediment-cover nappes representing ocean floor and underplated fragments of
the western continental margin. The tectonic structures formed during these orogenic events (“Younger Kimmeridian or Eohellenic
Orogeny”) are sealed by Late Jurassic platform carbonates. The geological history conforms with that of the Inner Dinarides
and adjoining areas; we therefore correlate the Mirdita-Pindos Ophiolite Zone with the Vardar Zone and explain its present
position by far-distance west-directed thrusting. 相似文献
30.
We developed light requirements for eelgrass in the Pacific Northwest, USA, to evaluate the effects of short- and long-term
reductions in irradiance reaching eelgrass, especially related to turbidity and overwater structures. Photosynthesis-irradiance
experiments and depth distribution field studies indicated that eelgrass productivity was maximum at a photosynthetic photon
flux density (PPFD) of about 350–550 μmol quanta m−2 s−1. Winter plants had approximately threefold greater net apparent primary productivity rate at the same irradiance as summer
plants. Growth studies using artificial shading as well as field monitoring of light and eelgrass growth indicated that long-term
survival required at least 3 mol quanta m−2 day−1 on average during spring and summer (i.e., May-September), and that growth was saturated above about 7 mol quanta m−2 day−1. We conclude that non-light-limited growth of eelgrass in the Pacific Northwest requires an average of at least 7 mol quanta
m−2 day−1 during spring and summer and that long-term survival requires a minimum average of 3 mol quanta m−2 day−1. 相似文献