应用MATLAB设计高效多级抽取滤波器   总被引：1，自引：1，他引：0  

赵凤花  廖成旺  夏界宁  谭耀银 《大地测量与地球动力学》2007,27(Z1):133-136

介绍如何应用Matlab设计级联梳状(CIC)滤波器、半带滤波器和有限脉冲响应(FIR)滤波器。并设计了一种高效的多级抽取滤波器，将该算法用数字信号处理器(DSP)进行验证，结果表明，该多级抽取滤波器能满足地震数据采集系统的精度要求。  相似文献   

Hydrological alterations from water infrastructure development in the Mekong floodplains          下载免费PDF全文

Thanh Duc Dang  Thomas A. Cochrane  Mauricio E. Arias  Pham Dang Tri Van  Tonny T. de Vries 《水文研究》2016,30(21):3824-3838

The Mekong floodplains, which encompasses the region from Kratie Township in Central Cambodia to the Vietnamese East Sea, is a region of globally renown agricultural productivity and biodiversity. The construction of 135 dams across the Mekong basin and the development of delta‐based flood prevention systems have caused public concern given possible threats on the stability of agricultural and ecological systems in the floodplains. Mekong dams store water upstream and regulate flow seasonality, while in situ flood prevention systems re‐distribute water retention capacity in the floodplains. The main aim of this paper is to evaluate possible impacts of the recent development of both hydropower dams and flood prevention systems on hydrological regimes in the Mekong floodplains. An analysis of measured daily and hourly water level data for key stations in the Mekong floodplains from Kratie to the river mouth in Vietnam was conducted. Hydropower dam information was obtained from the hydropower database managed by the Mekong River Commission, and the MODIS satellite imagery was used to detect changes in flooding extent related to the operation of flood prevention systems in the Vietnam Mekong Delta. Results indicate that the upper part of the floodplains, the Cambodian floodplains, may buffer upstream dam impacts to the Vietnam Mekong Delta. Flood prevention up to date has had the greatest effect on the natural hydrological regime of the Mekong floodplains, evidenced by a significant increase of water level rise and fall rates in the upper delta and causing water levels in the middle delta to increase. The development of flood prevention systems has also effected spatial distribution of flooding as indicated via a time series analysis of satellite imagery. While this development leads to increase localized agricultural productivity, our historical data analysis indicates that development of one region detrimentally affects other regions within the delta, which could increase the risk of future conflicts among regions, economic sectors and the ecological value of these important floodplains. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Relating hydrograph components to rainfall and streamflow: a case study from northern Taiwan     

Yu-Ji Li  Tsang-Long Pao  Yi-jie Bi 《水文科学杂志》2013,58(5):861-877

Abstract

This study investigates the characteristics of hydrograph components from a watershed in Taiwan. Hydrograph components were modelled by using a model of three serial reservoirs with one parallel reservoir. Mean rainfall was calculated by using the block kriging method. The model parameters for 38 events were calibrated by using the shuffled complex evolution optimization algorithm. The model verification was made using 18 events. Based on the study results, the following findings were obtained: (1) for single-peak events, times to peak of hydrograph components are an increasing power function of the peak time of rainfall; (2) peak discharges of hydrograph components are linearly proportional to that of total runoff, and the ratios of quick and slow runoff are approximately 83% and 17% of total runoff, respectively; and (3) the total volume of quick runoff component is 52% of total runoff and that of slow runoff is 27%.

Editor D. Koutsoyiannis

Citation Li, Y.-J., Cheng, S.-J. Pao, T.-L. and Bi, Y.-J., 2012. Relating hydrograph components to rainfall and streamflow: a case study from northern Taiwan. Hydrological Sciences Journal, 57 (5), 861–877.  相似文献   

动能空间尺度分解及其在高原切变线的分析应用     

罗潇  李国平 《高原气象》2019,(2):314-324

应用NCEP FNL(1°×1°)全球分析资料和动能的空间尺度分解方法,对2014年8月25—27日一次高原切变线过程进行了能量诊断分析。结果表明:低层扰动动能的增幅与高原切变线的发生发展密切相关,在切变线的生成阶段至成熟阶段,扰动动能增加为切变线的发生发展提供了能量保障;平均动能变化大体与扰动动能呈相反趋势,在切变线生成阶段和发展阶段,中低层平均动能随时间减小。在影响动能变化的各因子中,斜压转换项贡献最大;在切变线生成阶段,低层平均动能与扰动动能间的转换对扰动动能变化影响明显。背景场和扰动场的相互作用使得扰动动能增大而平均动能减小,构成动能的降尺度串级,这种能量串级转换有利于中尺度的高原切变线生成。  相似文献   

Review study on near-natural conditions of Central European mountain streams, with particular reference to debris and beaver dams: Results of the “REG meeting” 2000     

Daniel Hering  Marc Gerhard  Ellen Kiel  Thomas Ehlert  Tanja Pottgiesser   《Limnologica》2001,31(2):81

This paper summarises the results of the “Rhithron Ecology Group” meeting in Essen (March 2000), supplemented by a literature evaluation.An extended view of small mountain streams in Central Europe under “potentially natural conditions” is presented. We focus on the potential impact of natural transverse structures (debris dams and beaver dams) on stream morphology, hydrology, habitat composition and communities. Furthermore, impact of other stream morphological features, which are presently lacking in the Central European landscape, is described.We suggest that Central European mountain streams are characterised by a higher proportion of lentic zones under “potentially natural conditions”. Morphological degradation leads to a loss of lentic zones and to an increase of current velocities and corresponding changes in faunal composition, particularly higher abundance and proportion of rheophilic species and a decrease of species preferring lentic zones. This should be regarded in future stream assessment.  相似文献   

Probabilistic assessment of seismic hazard of dam sites in Jordan     

Azm S. Al-Homoud  Abdallah I. Husein 《Natural Hazards》1995,11(2):123-134

A Probabilistic method is used to evaluate the seismic hazard of nineteen embankment dam sites in Jordan. A line source model developed by McGuire (1978) is used in this study. An updated earthquake catalogue covering the period from 1 A.D. to 1991 A.D. is used for this purpose. This catalogue includes all earthquakes that occurred in Jordan and adjacent areas, more specifically between latitudes 27.0°–35.5° N and longitudes 32.0°–39.0° E.Nine distinct seismic sources of potential seismic activities are identified. The seismic hazard parameters are determined using the method suggested by Kijko and Sellevoll (1989).The Peak Ground Acceleration (PGA) is selected as a measure of ground motion severity. Esteva (1974) attenuation relationship is used in evaluating PGA values at each dam site. Analysis is carried out for 50%, 90%, and 95% probability that is not being exceeded in a life time of 50, 100, and 200 years.Results of analysis indicate that PGA values are higher for dam sites closer to the Dead Sea Fault. This fault is believed to be responsible for most earthquake activities in Jordan and vicinity. The highest PGA value is found to be for Al-Karama dam site.  相似文献   

土地系统研究的几个问题   总被引：4，自引：0，他引：4  

史华 《地球科学进展》1993,8(5):75-80

对土地系统研究的形成背景、研究现状及发展趋势进行了综述,并在此基础上,就土地系统研究的对象、理论基础和体系等进行了探讨。  相似文献   

Hard state of the urban canopy layer turbulence and its self-similar multiplicative cascade models     

HU Fei  CHENG Xueling  ZHAO Songnian  QUAN Lihong 《中国科学D辑(英文版)》2005,48(Z2)

It is found by experiment that under the thermal convection condition, the temperature fluctuation in the urban canopy layer turbulence has the hard state character, and the temperature difference between two points has the exponential probability density function distribution. At the same time, the turbulent energy dissipation rate fits the log-normal distribution, and is in accord with the hypothesis proposed by Kolmogorov in 1962 and lots of reported experimental results. In this paper, the scaling law of hard state temperature n order structure function is educed by the self-similar multiplicative cascade models. The theory formula is Sn = n/3μ{n(n+6)/72+[2lnn!-nln2]/2ln6}, and μ Is intermittent exponent. The formula can fit the experimental results up to order 8 exponents, is superior to the predictions by the Kolmogorov theory, the β And log-normal model.  相似文献   

Seismic behaviour of cracked concrete gravity dams     

O. A. Pekau  Xueye Zhu 《地震工程与结构动力学》2006,35(4):477-495

A finite element model of incremental displacement constraint equations (IDCE), based on an existing node‐to‐surface concept, is implemented to deal with dynamic contact surfaces in the seismic behaviour analysis of cracked concrete gravity dams. After verification for sliding, rocking and impact, the IDCE model is applied to study the seismic responses of concrete gravity dams with different profiles and crack locations for a variety of parameters, such as coefficient of friction, water level and type of earthquake, as well as impact damping based on the concept of coefficient of restitution. It is revealed that cracked concrete gravity dams can experience not only sliding and rocking modes, but also the drifting mode in some cases of crack either at the base or at a height. Downstream sliding is normally accompanied by rocking, especially for the cases of crack at a height. Due to rocking and drifting, a cracked dam may still acquire a certain amount of residual sliding even if the effective coefficient of friction is relatively high. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

1995年云南孟连西7.3级地震前震序列特征及其与主震的关系     

刘祖荫  钱晓东  张俊伟 《湖南地质》1998,(4)

在分析１９９５年云南孟连西７３级地震的前震序列时,发现跟踪最大前震６２级的余震序列中,有一组较大震级的地震呈现出随时间的增长不断线性递增的特点,这种特点在云南其他震例中也曾多次出现过。利用修正的大森公式ｎ（ｔ）＝ｋ／（ｔ＋ｃ）ｐ拟合该序列,在获得的参数重新构造的频度－线性化时间坐标中,这一组地震显示出与海城前震序列随时间变化震级出现非线性增强的共同特征。采用表征物质加速应变而失稳的方程ｄ（∑Ｍ０１／２）／ｄｔ＝ｃ／（ｔｍ－ｔ）ｎ,对孟连西前震序列多方面进行跟踪定量分析,预测主震的发生时间平均比实发时间仅推迟２６ｍｉｎ,震级相差０１７级。  相似文献