小流域水沙耦合模拟概念模型*

小流域水沙耦合模拟概念模型,采用文献[1]、[2]和[4]中提出的概念性坡面产沙、沟蚀产沙、坡面汇沙、沟道汇沙和格林-安普特下渗曲线结构,结合水文学中的概念性汇流计算方法,构成了一个完整的、具有明确物理意义的流域水流、泥沙耦合模拟模型.该模型结构简单,经子洲试验站团山沟三试验场和蛇家沟、团山沟、水旺沟三试验小流域实测资料的模拟检查表明,模型结构合理、效果较好,适合于黄土地区流域.     

Observations of desert flood bores

Flood bores have been measured in desert stream floods. The bores were steep and small pebbles were observed to be pushed ahead. Bore velocity changed downstream and was controlled by local channel geometry. In narrow reaches, the bore advanced at rates twice those of wide reaches. Mean bore velocity was about 50 per cent of that of mean flow at peak flood discharge. The surfaces of shallow bores were covered by air foams. This was not the case in deeper, faster examples.     

试论小区地震活动的时间规律

为了探讨小区域内地震活动的时间规律。本文在中国大陆选择了11个地点分析其从远古至公元1990年间的破坏性地震（M≥4 3／4）的活动性。因而发现小区的地震活动规律主要表现于以大震为代表的地震活动分期上，破坏性地震的频率、集中程度与阶段性变化上，以及与所在地震区地震活动期的关系上，不同小区的地震活动特征有共性，有类型区别，更有各自的特殊性。     

Structure,composition and bulk properties of upland stream gravels

Upland gravel-bedded streams in the U.K. have received only scant attention from both hydrologists and sedimentologists, but are worthy of further investigation. The sedimentology of three small streams in Teesdale in the Pennines has been examined in detail. Grain-size characteristics, bedforms, structure, composition and packing characteristics of these deposits are described, and compared where appropriate with published information. It is argued that a fuller appreciation of gravel bed composition and morphology should eventually contribute to an improved understanding of sediment transport and deposition mechanisms, and, hence, to improved accuracy in sediment transport and deposition estimates.     

川西地区小震重新定位及其活动构造意义

使用双差地震定位法对川西地区1992～2002年的13367个小震进行重新定位， 初步分析了地震活动性与地表活动构造的关系及其揭示的构造信息. 重新定位后，地震活动沿活动断裂成线（带）状分布现象非常突出，呈现出与地表活动构造的密切关系：结构简单的单一走滑断层具有上宽下陡的花状结构特征，拉分盆地与逆断裂具有线性而发散的分布式结构特征，逆断裂之下还存在缺震层. 此外，沿活动断裂带地震活动还具有空间分段性，揭示出局部地段存在着隐伏活动断裂和可圈定为地震危险区的地震空区. 震源深度分布显示，川西高原在15～20km的深度范围内普遍存在厚度约5km的缺震层，以高温高压实验结果为基础，通过计算川西地区地壳强度表明，大约14～19km的深度范围花岗岩处于塑性流变状态，说明缺震层的出现具有地壳物质塑性变形基础.     

Relationships between land-use and forced-pool characteristics in the Colorado Front Range

Land use practices in Colorado during the last two centuries altered the supply of sediment and water to many channels in the upper South Platte Basin. As a result of increased supply of sediment and mobility and reduced peak flows, the characteristics of pools associated with channel constrictions, referred to as forced pools, may have been altered. Increased supply of sediment and reduced transport capacity of high flows could lead to aggradation in forced pools. Channel confined by road corridors could lead to high velocities at normal flows, increased energy dissipation from riprap, or even increased pool frequency resulting from failed riprap. To assess potential alterations, four hypotheses were tested: (1) impacted streams will show significantly different mean volume of pools than a control stream; (2) mean volume of pools on streams where land-use activities increased the supply of sediment will be significantly different from streams solely affected by flow regulation; (3) the strongest change in characteristics of pools of impacted streams will be a reduced volume of pools; (4) streams affected by road corridors will show statistically lower spacing of pools than streams unaffected by roads. The downstream spacing and residual volume of twenty consecutive forced pools were surveyed on five streams in the Colorado Front Range that varied from no contemporary impact to multiple historical and contemporary impacts. ANCOVA with stepwise model selection indicated that degree of land-use (categorical), bankfull spacing of pools, upstream riffle slope and expansion ratio were all significant (α = 0.1) predictors of volume of pools (R² = 0.73). Simple linear regression of mean volume of pools and stream specific variables (gradient, drainage area and discharge) and least square means comparison of mean volume of pools indicated a need to standardize volumes of pools by slope and discharge so that the volumes of pools could be compared among different levels of land-use. Significant correlations between drainage area and volume of pools allowed volume of pools to be standardized by drainage area and thereby discharge. This dimensionless variable was also significantly correlated with channel slope, which permitted the construction of a new variable, PV_QS (volume of pools standardized by discharge and slope). Least square means comparison of mean PV_QS revealed that the control reach was significantly different from road-impacted reaches. Mean volume of pools was significantly larger in the control reach compared to all but one road-impacted stream. This was likely a function of higher wood loading in the control reach and the competence of high flows in the road-impacted reach. Streams affected by road corridors did not have significantly different bankfull spacing of pools from streams not impacted by roads. The multiple interactions among control and response variables explored in this study indicate the need to identify the most constrained and sensitive response variables when attempting to assess channel response to land use.     

Morphology of step-pools in a wilderness headwater stream: The importance of standardizing geomorphic measurements

The morphology of step-pools and cascades reflect the geological and climatic factors affecting channels in mountain watersheds. This study uses longitudinal and cross-section surveys to describe a headwater stream in the Boston Mountains of the Ozarks Plateau region in Arkansas and develop morphological relationships for comparisons with other regions. In the Bowers Hollow Creek watershed (3.5 km²), located within the boundaries of the Upper Buffalo Wilderness Area, step height and wavelength relationships are generally similar to those reported from other regions. Step-pool reaches were widely distributed in a discontinuous manner throughout the watershed. Average values of the sampled reaches are: reach slopes, 0.105 m/m; width, 6.10 m; crest particle sizes, 440 mm; step heights, 0.87 m; and step wavelengths, 6.62 m. The mean step steepness for the watershed was 0.13, whereas the mean length of a reach step to height ratio was 9:1. A comparison of morphological definitions found that the values of step height and steepness can vary by > 30% according to how step parameters are defined. Step height is particularly sensitive; thus, comparison of step height-based relationships from published data requires great care.     

小灌区农田土壤水分析

对山西省小灌区农田土壤水分在时空分布及其影响因素进行了分析.结果表明:大气降水、农田灌溉、作物蒸腾和田间土壤蒸发是影响土壤水分变化的主要因素.农田土壤水分分布随着作物的种类而变化.     

Geostatistical incorporation of spatial coordinates into supervised classification of hyperspectral data

 This paper presents a methodology to incorporate both hyperspectral properties and spatial coordinates of pixels in maximum likelihood classification. Indicator kriging of ground data is used to estimate, for each pixel, the prior probabilities of occurrence of classes which are then combined with spectral-based probabilities within a Bayesian framework. In the case study (mapping of in-stream habitats), accounting for spatial coordinates increases the overall producer's accuracy from 85.8% to 93.8%, while the Kappa statistic rises from 0.74 to 0.88. Best results are obtained using only indicator kriging-based probabilities, with a stunning overall accuracy of 97.2%. Significant improvements are observed for environmentally important units, such as pools (Kappa: 0.17 to 0.74) and eddy drop zones (Kappa: 0.65 to 0.87). The lack of benefit of using hyperspectral information in the present study can be explained by the dense network of ground observations and the high spatial continuity of field classification which might be spurious. Received: 12 April 2001 / Accepted: 7 September 2001     

应用高分辨CT（HRCT）扫描弥补腔隙诊断之不足

目的：应用高分辨CT（HRCT）扫描方法，增加对头颅腔隙梗塞诊断的可靠性，材料和方法：对临床疑有腔隙的病人，在基底节区及可疑部位加用HRC扫描，遇到腔隙病灶与像素颗粒难以区分时在相同层面或上下1－2mm处做HRCT扫描。结果，有489例常规CT正常的病例哪现了腔隙灶，在遇到的502例不易诊断的可疑病灶中，经HRCT确诊的真正腔隙灶300例，伪腔隙（像素）202例，同时发现HRCT对正常脑组织结构的显示要较常规CT越得多，结论HRCT不仅能提高腔隙性梗塞的检出率，还能辨伪腔隙，是弥补常规CT对腔隙诊断不足的较好手段。