Variation reduction in quality of an optical triangulation system employed for underwater range finding

This paper attempts to more thoroughly understand the factor effects on the performance of an optical triangulation system used for range finding in water. In this study analytical expressions for estimating the peak of the laser spot and for image processing were presented. Both the design of experiment process and the Taguchi method have been used to evaluate factor effects and to specify design parameters. To assess the effects of monochrome and color image displays on the performance of range finding, two sets of experiments were carried out. The optimum models based on factor effects were predicted and constructed through the analysis of variance. The confirmation experiments were performed and the outcomes are in good agreement with the predicted optima. Based upon the results of experiments and analyses, it is found that brightness, contrast, and peak detection algorithms are the main factors to dominate the quality of range finding while using a monochrome camera. And further, all control factors of brightness, contrast, peak detection algorithm, sampling range, and specific primary color for intensity computation are critical to the quality of range finding while using a color camera. Notably, right selections of the image resolution and the sampling range can shorten the computing time and get high precision results.     

两类增长曲线模型误差方差估计——二次型容许估计

研究两类增长曲线模型误差方差的二次型估计的容许性，在损失函数为（ｄ－σ２）／σ４时，对这两类模型分别给出一个二次型估计在二次型估计类中可容许的充要条件     

油气运移中断层精细刻画的优选方法——以南海北部珠江口盆地惠西南地区为例

油气运移是油气成藏的关键要素之一,依据油气运移方式及动力和空间位置等可分为初次运移和二次运移2个阶段,其中,二次运移决定了油气主要运移方向以及源—汇—聚成藏的空间位置。二次运移包括：油气通过储集层及不同类型载体的运移;已形成油气聚集或油气藏在圈闭条件变化尤其是断层活动引起的再次运移。毋庸置疑,断层作为油气运聚的主要载体其在油气运移和聚集中起到了非常重要的作用。然而前人对断层在油气运移输导作用的研究多集中在运聚机理的定性描述上,对油气二次运移中断层运聚输导作用分析尚缺少宏观、立体及实际的手段。鉴此,在南海北部珠江口盆地惠西南转换带油气运移及断层对油气的封堵输导机制的研究中,尝试在应用地球物理方法获取的高质量断层剖面分析基础上,精细刻画断层走向以及微裂隙的分布特征,深入剖析断层对油气封堵与输导作用的差异,进而为油气运移路径分析等提供技术支持。采取的具体技术方法是：首先,对地震数据体做方差体属性分析,并提取时间切片进而确定断层空间展布特征;其次,在方差属性体基础上实施蚂蚁体追踪技术,进一步刻画断层微裂隙概貌,深入分析不同断层及其不同部位对油气封堵与输导差异;再次,利用成像精度较高的三维可视化技术进一步分析断层空间上对油气封堵与输导的作用,为剖析油气运移路径及方向提供新的思路与方法。总之,这种地震与地质相结合的研究思路及方法,大大提高了油气二次运移方向判识的精度及可靠性,故对油气勘探目标的评价优选具有参考借鉴意义。     

Wave-induced water table fluctuations,sediment transport and beach profile change: Modeling and comparison with large-scale laboratory experiments

Coastal groundwater systems can have a considerable impact on sediment transport and foreshore evolution in the surf and swash zones. Process-based modeling of wave motion on a permeable beach taking into account wave-aquifer interactions was conducted to investigate the effects of the unconfined coastal aquifer on beach profile evolution, and wave shoaling on the water table. The simulation first dealt with wave breaking and wave runup/rundown in the surf and swash zones. Nearshore hydrodynamics and wave propagation in the cross-shore direction were simulated by solving numerically the two-dimensional Navier–Stokes equations with a k–ε turbulence closure model and the Volume-Of-Fluid technique. The hydrodynamic model was coupled to a groundwater flow model based on SEAWAT-2000, the latter describing groundwater flow in the unconfined coastal aquifer. The combined model enables the simulation of wave-induced water table fluctuations and the effects of infiltration/exfiltration on nearshore sediment transport. Numerical results of the coupled ocean/aquifer simulations were found to compare well with experimental measurements. Wave breaking and infiltration/exfiltration increase the hydraulic gradient across the beachface and enhance groundwater circulation inside the porous medium. The large hydraulic head gradient in the surf zone leads to infiltration across the beachface before the breaking point, with exfiltration taking place below the breaking point. In the swash zone, infiltration occurs at the upper part of the beach and exfiltration at the lower part. The simulations confirm that beaches with a low water table tend to be accreted while those with a high water table tend to be eroded.     

海道测量中余水位分离方法的研究

证明了基于余水位信息进行海洋潮汐推算时不需考虑测量区域内潮汐性质是否相似;计算了中数法、陈宗镛法、Rossiter法、Doodson法、Godin法关于63个主要分潮的滤波器谱数值,从理论上对各模型滤波能力进行了量化表征;基于上述滤波法进行了仿真和实测水位的余水位分离计算。结果表明,Godin法可基本消除实测水位的短周期分潮影响,若进一步消除其隐含的中、长周期分潮影响,则Godin法在海道测量水位改正中将有更大应用价值。     

Sources of dissolved organic carbon during stormflow in a headwater agricultural catchment

Increasing dissolved organic carbon (DOC) concentrations have been reported during the last 15 years in streams from the United Kingdom, Northern Europe and North America. Identifying the sources of DOC and the controls of the delivery to the stream is important to understand the significance of these trends. This relies on the availability of observations of DOC dynamics during storm events, since much of the DOC export from soils to streams occurs during high flows. This study analyses DOC data for eight storm events during winter 2005–2006 in a small agricultural experimental catchment—the Kervidy‐Naizin experimental catchment—located in Western France. A four end‐member mixing approach was applied to the eight monitored storm events to identify DOC sources and quantify their respective contribution to DOC stream fluxes, using DOC, nitrate, sulphate and chloride as tracers. The results show that DOC concentrations in the stream at the outlet of this catchment increase markedly during storm events. The slope of the linear regression between DOC concentration and discharge was not constant for the eight events and depended on pre‐event hydrological conditions. Between 64 and 86% of the DOC that enter the stream during storms originated from the upper layers of the riparian wetland soils. The variation of the delivery of DOC seems to be controlled by hydrological processes only, the wetland soils acting as a non‐limiting store. Copyright © 2009 John Wiley & Sons, Ltd.     

Separation of base flow from streamflow using groundwater levels—illustrated for the Pang catchment (UK)

A new filter to separate base flow from streamflow has developed that uses observed groundwater levels. To relate the base flow to the observed groundwater levels, a non‐linear relation was used. This relation is suitable for unconfined aquifers with deep groundwater levels that do not respond to individual rainfall event. Because the filter was calibrated using total streamflow, an estimate of the direct runoff was also needed. The direct runoff was estimated from precipitation and potential evapotranspiration using a water balance model. The parameters for the base flow and direct runoff were estimated simultaneously using a Monte Carlo approach. Instead of one best solution, a range of satisfactory solutions was accepted. The filter was applied to data from two nested gauging stations in the Pang catchment (UK). Streamflow at the upstream station (Frilsham) is strongly dominated by base flow from the main aquifer, whereas at the downstream station (Pangbourne) a significant component of direct runoff also occurs. The filter appeared to provide satisfactory estimates at both stations. For Pangbourne, the rise of the base flow was strongly delayed compared with the rise of the streamflow. However, base flow exceeded streamflow on several occasions, especially during summer and autumn, which might be explained by evapotranspiration from riparian vegetation. To evaluate the results, the base flow was also estimated using three existing base‐flow separation filters: an arithmetic filter (BFI), a digital filter (Boughton) and another filter based on groundwater levels (Kliner and Knĕz̆ek). Both the BFI and Boughton filters showed a much smaller difference in base flow between the two stations. The Kliner and Knĕz̆ek filter gave consistently lower estimates of the base flow. Differences and lack of clarity in the definition of base flow complicated the comparison between the filters. An advantage of the method introduced in this paper is the clear interpretation of the separated components. A disadvantage is the high data requirement. Copyright © 2004 John Wiley & Sons, Ltd.     

Runoff production processes in small alpine catchments within the unconsolidated Pleistocene sediments of the Lainbach area (Upper Bavaria)

In the Lainbach catchment, unconsolidated Pleistocene moraine sediments are widely distributed. Because of the great natural risk of floods, together with extreme loads of sediments, investigations of runoff production processes have been conducted in this area. At hillslope scale three test sites with different states of soil development and vegetation cover were instrumented with V‐shaped weirs, precipitation gauges and measurement devices for electrical conductivity (EC) of discharge water. The EC has been used as a geochemical tracer for hydrograph separation, since the statistical relationship between content of dissolved Ca²⁺, Mg²⁺ cations and EC is highly significant for different stages of runoff. This method allows hydrograph separation at high temporal resolution for both the rising and falling limb of the hydrograph. The following results of the investigations can be resumed. If relief conditions are similar, the effectiveness of runoff production decreases with an increasing density of vegetation cover. The runoff delivery ratio decreases as well as the peaks of runoff. In contrast, concentration times of hillslope catchments are equal, even if vegetation cover is of great density and soils are well developed. As a reason for the short reaction times, different runoff production processes have been detected. On bare ground, infiltration excess overland flow intensified by surface sealing processes is the main source for quick runoff. On hillslopes well covered by vegetation, translatory flow processes indicated by soil water with high solute contents force a rapid runoff reaction only a few minutes after rainfall has begun. It is to be assumed that translatory flow is a runoff production process typical for hillslopes covered by vegetation in a steep alpine relief. By means of the areal distribution of the topographic index, concentration of runoff production on a small part of the catchment has been demonstrated for hillslopes densely covered by vegetation. The investigations have shown that there is a lack of studies on runoff production processes in steep alpine relief, as well as a deficit of methods to quantify hydraulic properties of coarse‐grained soils with a wide grain size distribution. Copyright © 2003 John Wiley & Sons, Ltd.     

III: Methods of correcting for systematic errors in atmospheric precipitation measurements in Czechoslovakia

The methods of correcting for systematic errors in precipitation measurements using the Czechoslovak gauge METRA 886 are presented. This gauge has an orifice area of 500 cm² and is elevated 1 m above the ground. The wetting correction amounts to 0.1–0.2 mm per measurement. The evaporation correction ranges from 3 per cent in frost-free periods to 10 per cent in frost periods. The wind-induced correction amounts to 5 per cent for rain and 45 per cent for snow. The total sum of corrections on average 10–15 per cent per year in lower localities.     

Generalized cross-covariances and their estimation

Generalized cross-covariances describe the linear relationships between spatial variables observed at different locations. They are invariant under translation of the locations for any intrinsic processes, they determine the cokriging predictors without additional assumptions and they are unique up to linear functions. If the model is stationary, that is if the variograms are bounded, they correspond to the stationary cross-covariances. Under some symmetry condition they are equal to minus the usual cross-variogram. We present a method to estimate these generalized cross-covariances from data observed at arbitrary sampling locations. In particular we do not require that all variables are observed at the same points. For fitting a linear coregionalization model we combine this new method with a standard algorithm which ensures positive definite coregionalization matrices. We study the behavior of the method both by computing variances exactly and by simulating from various models.