Modelling mean annual sediment yield using a distributed approach

In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10–5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

地震作用下智能相邻建筑的主动锚索控制

研究了应用主动锚索控制装置控制相邻建筑地震响应的有效性。首先，建立了主动锚索－相邻建筑系统的运动方程；然后应用广义振型分析方法，寻求了主动锚索联结的相邻建筑的力学特性，特别是振型阻尼比；最后，在频率域内应用广义振型分析与虚拟激励相结合的方法，建立了主动锚索控制装置联结相邻建筑的随机地震响应的分析方法。应用本文建立的公式，我们编制了计算机程序，进行了广泛的参数研究，以评价控制装置的有效性，并确定最优传感器类型及控制装置参数。研究表明，如果应用速度传感器，并能适当地选择主动锚索控制器的参数，则可以显著地提高系统的振型阻尼比，减小两个结构的地震响应。     

抗震结构的阻尼减振效果分析

研究了抗震结构的阻尼减振效果。首先，考虑了单自由度体系在不同频率简谐干扰作用下阻尼比对结构反应的减小效果；然后，考虑了阻尼比对结构地震反应谱的影响，分析了我国现行建筑抗震设计规范反应谱，并讨论了不同阻尼比对水平地震影响系数的修正公式。     

岩石非均匀性对超声衰减的影响及其修正

在充分考虑了岩石的非均匀性引起的Rayleigh散射对衰减测量值的影响后，通过有关理论和计算，将岩石的本征衰减和散射加以区分，对原先以均匀介质为基本假定的频谱比法进行了修正，改进后的频谱比法可在较宽的频率范围内进行Q值计算，避免了传统频谱比法在不同频段上得出不同的Q值的不确定性问题，同时，我们还引进并改进了频率移动法，我们将传统和改进的频谱比法，以及频率移动法应用于同一套实验数据，计算结果符合较好。     

Impact of historic land‐use change on sediment delivery to a Chesapeake Bay subestuarine delta

Historic land use in the Chesapeake Bay drainage basin induced large fluxes of fluvial sediment to subestuarine tributaries. Stratigraphic and palaeoecologic analyses of deltaic deposits may be used to infer changes on the landscape, but are not sufficient to quantify past sediment supply. When viewed as an inverse boundary‐value problem, reconstruction of the sediment supply function may be achieved by combining deltaic sedimentation chronologies with an equation governing delta progradation. We propose that the diffusion equation is appropriate for simulating delta progradation and obtaining the sediment supply function provided a suitable diffusion constant (D) can be determined. Three new methods for estimating D are presented for the case of estuarine deltas. When the inverse boundary‐value technique was applied to Otter Point Creek, a tidal freshwater delta at the head of Bush River in upper Chesapeake Bay, D values ranged from 3763 to 6199 m² a^?1. Delta growth simulations showed a 1740–1760 initial pulse, a 1760–1780 erosive/redistributive interval, a 1780–1920 growth period, and a 1920‐present erosive/redistributive era. Coupling of simulated delta elevations with an empirical plant habitat predictive equation allowed for comparison of predicted versus actual relative habitat areas. Also, the model yielded reconstructed watershed erosion rates and stream suspended sediment concentrations that could be useful for development of water quality regulations. Copyright © 2001 John Wiley & Sons, Ltd.     

THE TECHNIQUE OF QUASI-LOSSLESS COMPRESSION OF THE REMOTE SENSING IMAGE

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Relationship between erosion and sediment yield in drainage basins of loess gully-hilly areas

From a long-term point of view, the balance between erosion and sediment yield in a drainage system can basically realize, i.e., the delivery ratio can be close to 1. However, substantial variations among individual rainfall events or between annual delivery ratio exist, causing frequent sediment retaining or re-erosion and re-delivery of the retained sediments in a short period of time. Thus the delivery ratio will be < 1 or > 1. The sediment delivery ratio is closely related to the spatial distribution of rainfall and magnitude of rise and fall of peak flood and that of runoff depth in the drainage system. Delivery ratio of single event in a drainage system and changes of delivery capacity of silt-laden runoff in various classes of gullies can be expressed by transformation mechanism of shear force of a single rainstorm event with flood resulting from increase and decrease of peak flood per unit area.     

尾波振幅比和能量比异常特征研究

利用中国数字地震台网（CDSN）兰州台记录的短周期数字地震资料，测定了尾波最大振幅与S波最大振幅之比r1、尾波能量与S波能量之比的平方根值r2随时间的变化。结果表明：在永登主震（19950和天祝-古浪主震（1996）前，r1和r2均出现上升或下降异常变化，且有较大的偏离平均值的异常高值或异常低值出现。     

调制模式和调制比在地震预报中的意义

本文系统而简略地介绍了调制模式和调制比在地震预报中的应用。它是把外因、震源区在临震前的不稳定性以及前兆显示有机地结合起来预报地震的。该预报思想和方法可操作性强，易于普及，并有一定的抗混沌效果。     

On the use of UV spectrophotometry to assess dissolved organic carbon origin variations in the Upper Rhône River

To detect temporal changes and the origin of the refractory dissolved organic matter in the Upper Rhône River, UV light absorbance (A) at 285 nm and quantitative dissolved organic carbon (DOC) measurements were carried out. Data from 63 visits to the main channel over a period of two years and from visits to different waterbodies in the alluvial plain before and after a flood are presented. There was a good correlation between A (0.019–0.160) and the DOC content (1.40–9.81 mg/L) for the waterbodies, but not for the river axis with lower A (0.013–0.044) and DOC content (1.13–2.20 mg/L). Due to this good correlation, the DOC content could be quantified for the waterbodies by absorbance measurements only. For the river water this indirect determination of the DOC content was not possible. However, the A/DOC ratio showed changes in the composition of DOC of river water and provided indications about the origin of the dissolved organic matter in the Upper Rhône River.