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991.
992.
选取湖南省1990-2010年经济增长、对外贸易以及环境综合质量的时间序列数据,建立经济增长与环境污染水平的计量模型,检验湖南省环境综合质量的变动轨迹.结果表明:研究期内,湖南省环境污染的变动轨迹大致呈底部平滑的正“U”型曲线,由于湖南经济增长对环境始终存在负的规模效应与正的技术效应,环境曲线的变动轨迹主要取决于经济增长的结构效应,因此,实现产业结构的升级,合理配制轻重工业的比重,在经济增长与环境效益中寻求平衡,是湖南改善环境质量与经济发展关系的关键;此外,无论从FDI还是出口贸易的角度来看,“污染天堂”假说在湖南均不成立. 相似文献
993.
Y. Deng J. P. Wilson B. O. Bauer 《International journal of geographical information science》2013,27(2):187-213
This paper documents resolution dependencies in terrain analysis and describes how they vary across landform location. Six terrain attributes were evaluated as a function of DEM resolution—slope, plan curvature, profile curvature, north–south slope orientation, east–west slope orientation, and topographic wetness index. The research highlights the effect of varying spatial resolution through a spatial sampling/resampling scheme while maintaining sets of indexed sample points at various resolutions. Tested sample points therefore coincide exactly between two directly compared resolutions in terms of their location and elevation value. An unsupervised landform classification procedure based on statistical clustering algorithms was employed to define landform classes in a reproducible manner. Correlation and regression analyses identified sensitive and consistent responses for each attribute as resolution was changed, although the tested terrain attributes responded in characteristically different ways. These responses displayed distinguishable patterns among various landform classes, a conclusion that was further verified by a series of two‐sample, two‐tailed t‐tests. 相似文献
994.
Zhang Liqiang Deng Hao Chen Dong Wang Zhen 《International journal of geographical information science》2013,27(4):721-740
This article presents a spatial cognition analysis technique for automated urban building clustering based on urban morphology and Gestalt theory. The proximity graph is selected to present the urban mrphology. The proximity graph considers the local adjacency among buildings, providing a large degree of freedom in object displacement and aggregation. Then, three principles of Gestalt theories, proximity, similarity, and common directions, are considered to extract potential Gestalt building clusters. Next, the Gestalt features are further characterized with seven indicators, that is, area difference, height difference, similarity difference, orientation difference, linear arrangement difference, interval difference, and oblique degree of arrangement. A support vector machine (SVM)-based approach is employed to extract the Gestalt building clusters. This approach transforms the Gestalt cluster extraction into a supervised discrimination process. The method presents a generalized approach for clustering buildings of a given street block into groups, while maintaining the spatial pattern and adjacency of buildings during the displacement operation. In applications of urban building generalization and three-dimensional (3D) urban panoramic-like view, the method presented in this article adequately preserves the spatial patterns, distributions, and arrangements of urban buildings. Moreover, the final 3D panoramic-like views ensure the accurate appearance of important features and landscapes. 相似文献
995.
The morphological characteristics of glacial deposits during the Last Glaciation, taking the Parlung Zangbo River Basin as an example 总被引:1,自引:0,他引:1
Moraine morphology is a valuable indicator of climate change. The glacial deposits of ten valleys were selected in the Parlung Zangbo River Basin, southeastern Tibetan Plateau, to study the glacial characteristics of the Last Glaciation and the climate change processes as revealed by these moraines. Investigation revealed that a huge moraine ridge was formed by ancient glacier in the Marine Isotope Stage 2 (MIS2), and this main moraine ridge indicates the longest sustained and stable climate. There are at least two smaller moraine ridges that are external extensions of or located at the bottom of the main moraine ridge, indicating that the climate of the glacial stage before MIS2 was severer but the duration was relatively shorter. This distribution may reflect the climate of MIS4 or MIS3b. The glacial valleys show multi-channel, small-scale moraine ridges between the contemporary glacial tongue and the main moraine ridge. Some of these multi-channel mo- raine ridges might be recessional moraine, indicating the significant glacial advance during the Younger Dryas or the Heinrich event. The moraine ridges of the Neoglaciation and the Little Ice Age are near the ends of the contemporary glaciers. Using high-precision system dating, we can fairly well reconstruct the pattern of climate change by studying the shape, extent, and scale characteristics of glacial deposits in southeastern Tibet. This is valuable research to understand the relationship between regional and global climate change. 相似文献
996.
Tan K. Wang Ben Jhong Yang Jia-Ming Deng Chao-Shing Lee Char-Shine Liu 《Marine Geophysical Researches》2010,31(1-2):59-76
Horizon velocity analysis and pre-stack depth migration of seismic profiles collected by R/V Maurice Ewing in 1995 across the accretionary prism off SW Taiwan and along the continental slope of the northernmost South China Sea were implemented for identifying gas hydrates. Similarly, a survey of 32 ocean-bottom seismometers (OBS), with a spacing of about 500 m, was conducted for exploring gas hydrates on the accretionary prism off SW Taiwan in April 2006. Travel times of head wave, refraction, reflection and converted shear wave identified from the hydrophone, vertical and horizontal components of these OBS data were applied for imaging P-wave velocity and Poisson’s ratio of hydrate-bearing sediments. In the accretionary prism off SW Taiwan, we found hydrate-bearing sediment, with a thickness of about 100–200 m, a relatively high P-wave velocity of 1.87–2.04 km/s and a relatively low Poisson’s ratio of 0.445–0.455, below anticlinal ridges near imbricate emergent thrusts in the drainage system of the Penghu and Kaoping Canyons. Free-gas layer, with a thickness of about 30–120 m, a relatively low P-wave velocity of 1.4–1.8 km/s and a relatively high Poisson’s ratio (0.47–0.48), was also observed below most of the bottom-simulating reflectors (BSR). Subsequently, based on rock physics of the three-phase effective medium, we evaluated the hydrate saturation of about 12–30% and the free-gas saturation of about 1–4%. The highest saturation (30% and 4%) of gas hydrates is found below anticlines due to N–S trending thrust-bounded folds and NE-SW thrusting and strike-slip ramps in the lower slope of the accretionary prism. We suggest that fluid may have migrated through the relay-fault array due to decollement folding and gas hydrates have been trapped in anticlines formed by the basement rises along the thrust faults. In contrast, in the rifted continental margin of the northernmost South China Sea, P-wave velocities of 1.9–2.2 km/s and 1.3–1.6 km/s, and thicknesses of about 50–200 m and 100–200 m, respectively, for a hydrate layer and a free-gas layer were imaged below the remnant and erosional ridges in the upper continental slope. High P-wave velocity of hydrate-bearing sediment below erosional ridges may also indicate high saturation of hydrates there. Normal faults due to rifting in the South China continental crust may have provided conduits for gas migration below the erosional ridges where P-wave velocity of hydrate-bearing sediment in the passive continental margin of the northernmost South China Sea is greater than that in the active accretionary prism off SW Taiwan. 相似文献
997.
Vertical total electron content (VTEC) time series were obtained from 22 GPS stations near the epicenter of the Lushan earthquake. In this paper, we have adopted a sliding average method to detect and analyze anomalous VTEC associated with the earthquake. The results show that signif- icant, negative ionosphere VTEC anomalies appeared over the 5 days before the earthquake, and on the day when earthquake occurred. The maximum value of VTEC anoma- lies that exceeded the lower bound reached 20 TECU. The spatial distribution of VTEC anomalies showed a conjugate structure, which shifted to the magnetic equator, and subse- quently moved westwards. 相似文献
998.
This paper uses the density functional theory to analyse the stabilities, bond characters, static linear polarisabilities, and aromaticities of the `in-out' isomerism Hn-60@CnH60 (n=70, 72, 74). The binding energies, C--H bond energies, and energy gaps explore that the `in-out' isometric perhydrogenation of Cn (n=70, 72, 74) can remarkably improve the stabilities. The static linear polarisabilies of Hn-60@CnH60 (n=70, 72, 74) are indeed relative to their shapes, while they show almost nonaromatic character. This study can suggest that the `in-out' isometric perhydrogenation of fullerenes could lead to the invention of entirely novel potential hydrogen storage nanomaterials. 相似文献
999.
Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform. 相似文献
1000.
Zhen Zheng Yanjing Chen Xiaohua Deng Suwei Yue Hongjin Chen Qingfei Wang 《地学前缘(英文版)》2019,10(2):569-580
The Qiman Tagh W-Sn belt lies in the westernmost section of the East Kunlun Orogen, NW China, and is associated with early Paleozoic monzogranites, tourmaline is present throughout this belt. In this paper we report chemical and boron isotopic compositions of tourmaline from wall rocks, monzogranites, and quartz veins within the belt, for studying the evolution of ore-forming fluids. Tourmaline crystals hosted in the monzogranite and wall rocks belong to the alkali group, while those hosted in quartz veins belong to both the alkali and X-site vacancy groups. Tourmaline in the walk rocks lies within the schorl-dravite series and becomes increasingly schorlitic in the monzogranite and quartz veins. Detrital tourmaline in the wall rocks is commonly both optically and chemically zoned,with cores being enriched in Mg compared with the rims. In the Al-Fe-Mg and Ca-Fe-Mg diagrams,tourmaline from the wall rocks plots in the fields of Al-saturated and Ca-poor metapelite, and extends into the field of Li-poor granites, while those from the monzogranite and quartz veins lie within the field of Li-poor granites. Compositional substitution is best represented by the MgFe_(-1), Al(NaR)_(-1), and AlO(Fe(OH))_(-1) exchange vectors. A wider range of δ~(11)B values from -11.1‰ to -7.1‰ is observed in the wall-rock tourmaline crystals, the B isotopic values combining with elemental diagrams indicate a source of metasediments without marine evaporates for the wall rocks in the Qiman Tagh belt. The δ~(11)B values of monzogranite-hosted tourmaline range from -10.7‰ and-9.2‰, corresponding to the continental crust sediments, and indicate a possible connection between the wall rocks and the monzogranite. The overlap in δ~(11)B values between wall rocks and monzogranite implies that a transfer of δ~(11)B values by anataxis with little isotopic fractionation between tourmaline and melts. Tourmaline crystals from quartz veins have δ~(11)B values between -11.0‰ and-9.6‰, combining with the elemental diagrams and geological features, thus indicating a common granite-derived source for the quartz veins and little B isotopic fractionation occurred. Tourmalinite in the wall rocks was formed by metasomatism by a granite-derived hydrothermal fluid, as confirmed by the compositional and geological features.Therefore, we propose a single B-rich sedimentary source in the Qiman Tagh belt, and little boron isotopic fractionation occurred during systematic fluid evolution from the wall rocks, through monzogranite, to quartz veins and tourmalinite. 相似文献