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151.
The major hydrological factors in lake-marsh systems are water level (depth), water surface area, and water volume. The key index for determining the lake-marsh pattern is water level, which leads to the variation of lake-marsh patterns under natural hydrological alternations. In addition, the vegetation structure also affects the lake-marsh pattern. With socioeconomic development and climate change, the ‘land use’ and ‘water use’ competitions appear more seriously between a lake-marsh system and its surrounding socioeconomic system, also inside the lake-marsh system. The possible optimal lake-marsh pattern could solve the contradictions mentioned above. As few studies focus on this issue, this study proposed an optimal lake-marsh pattern determination method with eco-hydrological management on relieving the land use and water use competitions. The optimal lake-marsh pattern determination method considers the protection objects (water depth demands), water supply (precipitation, surface water, and groundwater), and water demand (especially evapotranspiration) in the system at annual and monthly scales. Calculation and analysis were performed for the optimal pattern of the Wolonghu Wetlands as an example. The results mainly showed that the lake-marsh pattern of the Wolonghu Wetlands cannot be achieved on meeting both the maximum ecological services values and minimum water shortage amount under present natural condition. With artificial regulation measures, the possible optimal annual lake-marsh patterns can be obtained based on both ecological and hydrological objectives, with the area ratio of lake and marsh in the range of 0.650:0.350 and 0.726:0.274, the corresponding water level of lake body was of 86.85 to 87.0 m. This study could provide references for the Wolonghu Wetlands management, also for similar lake-marsh systems and other ecological systems. 相似文献
152.
In this paper, we give theBV photoelectric light curves of the Algol-type eclipsing binary EU Hydrae. We have analysed its period by means of the times of minima determined from this observation and the times of minima which other observers published. The period was found to gradually decrease with a change rate dP/dE = -3
.
d
29 × 10–10. The obtained light curves have been solved using Wilson-Devinney's synthetic light-curve program. The results demonstrate that EU Hydrae is a detached system, the secondary component fills the Roche-lobe, its mass ratio is 0.205. EU Hya may evolve to be a semidetached system in which the secondary component fills the Roche-lobe. 相似文献
153.
区域旅游开发的RMP分析——以河南省洛阳市为例 总被引:55,自引:4,他引:55
针对目前中国区域旅游开发所面临的旅游产品结构性过剩、产品开发由80年代的“低投入高产出”向“高投入高风险高产出”的特征变化,作者提出了区域旅游开发中应该从资源(Resource)、市场(Market)和产品(Product)三个方面进行程序式评价论证,即所谓的昂谱(RMP)分析模式,为区域旅游规划提供基本思路。这一模式在1999年进行的洛阳市旅游发展总体规划中得到了操作性应用 相似文献
154.
155.
Geo-engineered buffer capacity of two-layered absorbing system under the impact of rock avalanches based on Discrete Element Method 总被引:1,自引:0,他引:1
Yu-zhang Bi Si-ming He Xin-po Li Yong Wu Qiang Xu Chao-jun Ouyang Li-Jun Su Hao Wang 《山地科学学报》2016,13(5):917-929
Many rock avalanches were triggered by the Wenchuan earthquake on May 12, 2008 in southwest China. Protection galleries covered with a single soil layer are usually used to protect against rockfall. Since one-layer protection galleries do not have sufficient buffer capacity, a two-layered absorbing system has been designed. This study aims to find whether an expanded poly-styrol (EPS) cushion, which is used in the soil-covered protection galleries for shock absorption, could be positioned under dynamic loadings. The dynamic impacts of the two-layered absorbing system under the conditions of rock avalanches are numerically simulated through a 2D discrete element method. By selecting reasonable parameters, a series of numerical experiments were conducted to find the best combination for the two-layered absorbing system. The values of the EPS layer area as a percentage of the total area were set as 0% (S1), 22% (S2), and 70% (S3). 22% of the area of the EPS layer was found to be a reasonable value, and experiments were conducted to find the best position of the EPS layer in the two-layered absorbing system. The numerical results yield useful conclusions regarding the interaction between the impacting avalanches and the two-layered absorbing system. The soil layer can absorb the shock energy effectively and S2 (0.4-m thick EPS cushion covered with soil layer) is the most efficient combination, which can reduce the impact force, compared with the other combinations. 相似文献
156.
The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area. 相似文献
157.
Geophysical characterization of the lithological control on the kinematic pattern in a large clayey landslide (Avignonet,French Alps) 总被引:2,自引:1,他引:1
Grégory Bièvre Denis Jongmans David Goutaland Erwan Pathier Vilma Zumbo 《Landslides》2016,13(3):423-436
Lithology variation is known to have a major control on landslide kinematics, but this effect may remain unnoticed due to low spatial coverage during investigation. The large clayey Avignonet landslide (French Alps) has been widely studied for more than 35 years. Displacement measurements at 38 geodetic stations over the landslide showed that the slide surface velocity dramatically increases below an elevation of about 700 m and that the more active zones are located at the bottom and the south of the landslide. Most of the geotechnical investigation was carried out in the southern part of the landslide where housing development occurred on lacustrine clay layers. In this study, new electrical prospecting all across the unstable area revealed the unexpected presence of a thick resistive layer covering the more elevated area and overlying the laminated clays, which is interpreted as the lower part of moraine deposits. The downslope lithological boundary of this layer was found at around 700 m asl. This boundary coincides with the observed changes in slide velocity and in surface roughness values computed from a LiDAR DTM acquired in 2006. This thick permeable upper layer constitutes a water reservoir, which is likely to influence the hydromechanical mechanism of the landslide. The study suggests a major control of vertical lithological variations on the landslide kinematics, which is highlighted by the relation between slide velocity and electrical resistivity. 相似文献
158.
Genetic modification is useful for improving the nutritional qualities of cyanobacteria. To increase the total unsaturated fatty acid content, along with the ratio of ω-3/ω-6 fatty acids, genetic engineering can be used to modify fatty acid metabolism. Synechococcus sp. PCC7002, a fast-growing cyanobacterium, does not contain a Δ6 desaturase gene and is therefore unable to synthesize γ-linolenic acid (GLA) and stearidonic acid (SDA), which are important in human health. In this work, we constructed recombinant vectors Syd6D, Syd15D and Syd6Dd15D to express the Δ15 desaturase and Δ6 desaturase genes from Synechocystis PCC6803 in Synechococcus sp. PCC7002, with the aim of expressing polyunsaturated fatty acids. Overexpression of the Δ15 desaturase gene in Synechococcus resulted in 5.4 times greater accumulation of α-linolenic acid compared with the wild-type while Δ6 desaturase gene expression produced both GLA and SDA. Co-expression of the two genes resulted in low-level accumulation of GLA but much larger amounts of SDA, accounting for as much to 11.64% of the total fatty acid content. 相似文献
159.
160.
Experiments on the partitioning of Cu between different granitic silicate melts and the respective coexisting aqueous fluids have been performed under conditions of 850 °C, 100 MPa and oxygen fugacity(f O2) buffered at approaching Ni–Ni O(NNO). Partition coefficients of Cu(DCu= cfluid/cmelt) were varied with different alumina/alkali mole ratios [Al2O3/(Na2O·K2O), abbreviated as Al/Alk], Na/K mole ratios, and Si O2 mole contents. The DCu increased from 1.28 ± 0.01 to 22.18 ± 0.22 with the increase of Al/Alk mole ratios(ranging from 0.64 to 1.20)and Na/K mole ratios(ranging from 0.58 to 2.56). The experimental results also showed that DCuwas positively correlated with the HCl concentration of the starting fluid.The DCuwas independent of the Si O2 mole content in the range of Si O2 content considered. No DCuvalue was less than 1 in our experiments at 850 °C and 100 MPa, indicating that Cu preferred to enter the fluid phase rather than the coexisting melt phase under most conditions in the melt-fluid system, and thus a significant amount of Cu could be transported in the fluid phase in the magmatichydrothermal environment. The results indicated that Cu favored partitioning into the aqueous fluid rather than themelt phase if there was a high Na/K ratio, Na-rich, peraluminous granitic melt coexisting with the high Cl-fluid. 相似文献