Estimation of ecological high flow     

Jen‐Yang Lin  Yen‐Chang Chen  Eric Hsienshao Tsao 《水文研究》2006,20(2):319-328

Floods can destroy fish habitat. During a flood a fish has to seek shelters (refuges) to survive. It is necessary to know the maximum discharge that the fish can sustain against the strong current. Ecological and hydraulic engineers can simulate the flow condition of high flow for designing the refuge when restoring and enhancing the rivers are needed. Based on the average ratio of the mean and maximum velocities invariant with time, discharge and water level, this paper tries to introduce the concept of ecological high flow. The mean‐maximum velocity ratio can be used to estimate the mean velocity of the river. If the maximum velocity of the cross section is replaced by the maximum sustained swimming speeds of fish, the mean velocity of ecological high flow can be calculated with the constant ratio. The cross‐sectional area can be estimated by the gage height. Then the ecological high flow can be estimated as the product of mean velocity of ecological high flow multiplied by the cross‐sectional area. The available data of the upstream of the Dacha River where is the habitat of the Formosan landlocked salmon were used to illustrate the estimation of the ecological high flow. Any restoration project at Sonmou that try to improve the stream habitat can use the ecological high flow to design the hydraulic structure at suitable location to offer refuges for the Formosan landlocked salmon that is an endangered species in Taiwan Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

胶州湾风暴潮增水重现值的长期预测   总被引：1，自引：0，他引：1  

董胜  许鹏婧  刘伟 《中国海洋大学学报(自然科学版)》2009,39(5)

以胶州湾30 a风暴潮过程的极值增水值为统计序列,按照年、季、月等不同时段,分别抽样极值增水样本,提出泊松最大熵分布,采用年极值法和过阈法对增水重现值进行长期预测,统计分析结果对于胶州湾防潮减灾有参考作用,其随机分析方法对于遭受风暴潮影响的海岸区域有借鉴意义。  相似文献   

Thermal expansion of Mg(OH)<Subscript>2</Subscript> brucite under high pressure and pressure dependence of entropy   总被引：1，自引：1，他引：0  

H.?FukuiEmail author  O.?Ohtaka  T.?Suzuki  K.?Funakoshi 《Physics and Chemistry of Minerals》2003,30(9):511-516

An equation of state for Mg(OH)₂ brucite under high-pressure and high-temperature conditions has been obtained by measuring temperature dependence of volume up to 600 K at ambient pressure and pressure dependence of volume up to 16 GPa at 300, 473, 673, and 873 K with in situ X-ray diffraction. Pressure dependence of entropy of brucite has been calculated with thermal expansion coefficient and volume which are derived from the present EoS. This dependence indicates that generation of secondary OH dipoles affects entropy. The OH dipoles probably appear around 2 GPa and the number seems not to change over 8 GPa at 300 K.  相似文献   

The Entropy Score and its Uses in Earthquake Forecasting   总被引：1，自引：0，他引：1  

David Harte  David Vere-Jones 《Pure and Applied Geophysics》2005,162(6-7):1229-1253

Suppose a forecasting scheme associates a probability p^* with some observed outcome. The entropy score given to this forecast is then –logp^*. This article provides a review of the background to this scoring method, its main properties, and its relationships to concepts such as likelihood, probability gain, and Molchans - diagram. It is shown that, in terms of this score, an intrinsic characterization can be given for the predictability of a given statistical forecasting model. Uses of the score are illustrated by applications to the stress release and ETAS models, electrical signals, and M8.  相似文献   

Heat-capacity measurements and absolute entropy of ɛ-Mg2PO4OH     

Catherine Leyx  J. Cornelis Van Miltenburg  Christian Chopin  Lado Cemič 《Physics and Chemistry of Minerals》2005,32(1):13-18

The low-temperature heat capacity of -Mg₂PO₄OH was measured between 10 and 400 K by adiabatic calorimetry. No phase transition was observed over this temperature range. A relative enthalpy increment of 22,119 J mol^–1 and an absolute entropy value of 127.13±0.25 J mol^–1 K^–1 at 298.15 K are derived from the results. The low-temperature heat-capacity data are compared with the DSC data obtained from 143 K to 775 K and show marginal differences in the common temperature range. The latter data are fitted by the polynomial which allows extrapolation to high temperatures.Software information: WINDOWS operating system, WORD word processing, SigmaPlot diagrams exported in tiff format.  相似文献   

Capturing the essential spatial variability in distributed hydrological modelling: Hydraulic roughness     

Baxter E. Vieux  Nadim S. Farajalla 《水文研究》1994,8(3):221-236

The spatial variability of each parameter affecting storm runoff must be accounted for in distributed modelling. The objective of the work reported here is to assess the effects of using distributed versus lumped hydraulic roughness coefficients in the modelling of direct surface runoff. A spatially variable data set composed of Manning roughness coefficients is used to model direct surface runoff. To assess the information content (as measured by entropy) of spatially variable data and its significance in distributed modelling, various degrees of smoothing are applied. The error resulting from smoothing the hydraulic roughness coefficients is determined by modelling overland flow using a finite element solution. The Manning roughness coefficients were taken from field measurements of the Manning roughness coefficient at 0.6 m on a 14 m hillslope. These values were then used in a numerical simulation of outflow hydrographs to investigate the dependence of error on spatial variability. Our study focuses on the characteristics of spatial data used in distributed hydrological modelling. The field sites have fractal dimensions of ≈? 1.4, which is close to a Brownian variation. The sampling interval that captures the essential spatial variability of the Manning roughness coefficient does not seem to matter due to its Brownian variation in the field sites. Hence due to the nearly uniform random distribution, measurements at 0.6 m intervals are not necessary and larger intervals would yield results that are just as acceptable provided the mean value together with a uniformly random distribution is maintained for any size of finite element or sampling resolution. Because detailed measurements of hydraulic roughness are not practically available for deterministic catchment modelling, it is important to know that larger sampling resolutions may be used than 0.6 m.  相似文献   

Assessing the spatial distribution of crop areas using a cross-entropy method   总被引：1，自引：0，他引：1  

Liangzhi You  Stanley Wood 《International Journal of Applied Earth Observation and Geoinformation》2005,7(4):310-323

While crop production statistics are reported on a geopolitical – often national – basis, we often need to know, for example, the status of production or productivity within specific sub-regions, watersheds, or agro-ecological zones. Such re-aggregations are typically made using expert judgments or simple area-weighting rules. We describe a new, entropy-based approach to the plausible estimates of the spatial distribution of crop areas. Using this approach tabular crop production statistics are blended judiciously with an array of other secondary data to assess the areas of specific crops within individual ‘pixels’—typically 25–100 km² in size. The information utilized includes crop production statistics, farming system characterization, satellite-based interpretation of land cover, biophysical crop suitability assessments, and population density. An application is presented in which Brazilian state level production statistics are used to generate pixel level crop area data for eight crops. To validate the spatial allocation we aggregated the pixel estimates to obtain synthetic estimates of municipality level areas in Brazil, and compared those estimates with actual municipality statistics. The approach produced extremely promising results. We then examined the robustness of these results compared to simplified approaches to spatializing crop production statistics and showed that, while computationally intensive, the cross-entropy method does provide more reliable spatial allocations.  相似文献   

关于熵与城市发展之探讨   总被引：5，自引：0，他引：5  

郑锋 《热带地理》2001,21(4):374-377

城市的形成和发展是一个历史过程，如何评判城市是一个深刻的哲学命题，从熵定律角度来研究城市发展，可以帮助我们建立一种新的城市发展观。城市发展是一个不可逆过程，城市作为一个开放的系统，只要能够从外部环境得到足够的负熵流以抵消内部的熵增，城市将形成耗散结构系统并朝着进化的方向发展。未来的城市应进入低熵社会，主要途径是：建立生态城市，走可持续发展的道路；建立数字城市，实现城市社会信息化；控制城市人口，合理发展城市规模。  相似文献   

运用灾害熵浅析沙尘暴强度   总被引：5，自引：3，他引：5  

李向军  陈亚宁  欧阳辉 《干旱区地理》2002,25(4):350-353

以信息熵原理为基础，引入灾害熵概念，评价自然灾害的发生的不确定性和根据各致灾因子的强弱，确定灾害事件的重要性因子，构建灾害信息量计算模型。并以新疆境内达坂城、精河、哈密、吐鲁番、鄯善等五个地区的多年沙尘暴灾害统计数据为研究实例，计算分析了灾害次数、灾害熵。经过分析得出：哈密地区的沙尘暴灾害不仅灾害强度最烈，致灾因子亦最为活跃。通过应用灾害熵及其相应的修正模式，可以定量的确定灾害的影响强度，定性地说明致灾因子的多寡。  相似文献   

断层形变高频波动丛集性前兆和异常判据研究     

葛彦增  卢良玉 《东北地震研究》1996,12(3):15-27

断层形变短临前兆表现形式是多样的，并作了初步分类，丛集性高频波动是其一种重要现形式，探索了这种前兆信息的提取思路和方法，认为信息丛集度Ｃ是描述这种前兆短临信息，熵值积分平滑值Ｇ是描述中短信息较理想的特征量，震例学表明第二类前兆具有较好的预报效能，对异常判据了初步探索。  相似文献