Capabilities of Large-scale Particle Image Velocimetry to characterize shallow free-surface flows

Irrespective of their spatial extent, free-surface shallow flows are challenging measurement environments for most instruments due to the relatively small depths and velocities typically associated with these flows. A promising candidate for enabling measurements in such conditions is Large-scale Particle Image Velocimetry (LSPIV). This technique uses a non-intrusive approach to measure two-dimensional surface velocity fields with high spatial and temporal resolutions. Although there are many publications documenting the successful use of LSPIV in various laboratory and field open-channel flow situations, its performance has not been equally substantiated for measurement in shallow flows. This paper aims at filling in this gap by demonstrating the capabilities of LSPIV to: (a) accurately evaluate complex flow patterns in shallow channel flows; and (b) estimate depth in shallow flows using exclusively LSPIV measurements. The demonstration is provided by LSPIV measurements in three shallow flow laboratory situations with flow depths ranging from 0.05 to 0.31 m. The obtained measurements illustrate the LSPIV flexibility and reliability in measuring velocities in shallow and low-velocity (near-zero) flows. Moreover, the technique is capable to evaluate and map velocity-derived quantities that are difficult to document with alternative measurement techniques (e.g. vorticity and shear stress distributions and mapping of large-scale structure in the body of water).     

带粒子滤波约束的PP-PS联合反演的稀疏解算法

随着地震勘探目标从构造型油气藏向岩性油气藏的转变,地震勘探难度日益增大,这就要求从地震数据中获得更多可靠且具有明确地质含义的属性信息,并充分利用这些属性信息来对储层的岩性、岩相进行分析.AVO三参数反演能够从振幅随炮检距的变化信息中直接提取纵波速度、横波速度以及密度来估计岩石和流体的性质,进而对储层进行预测.然而,AVO反演本身是一个不适定的问题,加上地震纵波反射系数对横波速度和密度的不敏感,会造成单纯利用纵波地震数据进行反演的结果误差大.随着地震接收和数据处理技术的发展,越来越多的学者对PP-PS联合反演方法进行了研究并在实际资料中得以运用.融合转换横波地震数据的联合反演在一定程度上提高了反演的精度,降低了解的不稳定性.但是在信噪比较低的情况下,联合反演的效果受到了限制.本文从优化理论出发,提出了基于粒子滤波提供先验知识的l₁范数约束极小化问题的稀疏解算法.并将上述方法运用到了不同的模型中,通过比较分析,证实了该方法在不同信噪比资料中的有效性和在信噪比较低情况下的优势.

     

A coastal prediction system as an event response tool: Particle tracking simulation of an anhydrous ammonia spill in Tampa Bay

A coastal prediction system for Tampa Bay, comprised of a numerical circulation model and Lagrangian particle transport model, rapidly produces hindcast/forecast simulations that alert authorities to high impact areas following the introduction of hazardous material into the bay. The effectiveness of the prediction system as an event response tool is evaluated during an anhydrous ammonia spill. A week-long simulation predicts the trajectory of the material due to winds and currents. Physical transport of the model particles alternates from being tidally driven to being driven both by wind action and residual circulation. A forecast simulation showing particle distribution drove field sampling that resulted in the detection of a Pseudo-nitzschia bloom likely initiated from excess ammonium in the bay. An online component of the coastal prediction system is in development to better manage response and mitigation efforts for future hazardous material spills in Tampa Bay.     

Non-food-chain transfer of sediment-associated persistent organic pollutants to a marine benthic fish

We investigated the transfer of persistent organic pollutants (POPs) from unspiked bottom sediment to a benthic marine fish, marbled sole (Pleuronectes yokohamae), via non-food-chain pathways, i.e., via sediment particles and water column. One-year-old sole were held for 28 days in an exposure tank with bottom sediment or in a control tank. o,p′-DDE and tri- to penta-chlorobiphenyls were transferred from the sediment to the fish via non-food-chain pathways, as demonstrated by concentrations in the exposed fish at 2.5-30 times the control levels. A model analysis based on first-order kinetic equations indicated that the overall rate constant of transfer of these compounds from sediment to fish was generally lower than that from food (median of ratio, 0.48). It also suggested that relatively high concentrations of the other POPs in the food and the longer times necessary for them to reach a steady state masked any transfer of them from the sediment.     

Crushed recycled glass as a filter medium and comparison with silica sand

The objective of this work was to evaluate crushed recycled glass as a medium for rapid filtration. In the first part of this work, physical and hydraulic characteristics of the glass medium were studied. In the second part, pilot scale inline filtration experiments were carried out using raw waters from three different water sources. Two physically identical filter columns were operated in parallel in all the experiments. One filter contained a silica sand medium that is widely used in Turkey, whereas the other filter contained crushed recycled glass. Experiments were repeated five times as follows: (i) Without the use of a coagulant, (ii–iii) with 5 mg/L and 10 mg/L of alum, and (iv–v) with 5 mg/L and 10 mg/L of ferric chloride. Turbidity, particle counts, and head losses were measured and compared as functions of time. The following were observed: (1) Provided that a coagulant was used, the filter containing crushed glass produced effluent turbidities and particle counts similar to those obtained with the sand filter. (2) The crushed glass medium generated both a smaller clean‐bed head loss and smaller clogging head losses than those of the sand filter. It is concluded that crushed glass shows significant promise as an alternative to silica sand in rapid filtration.     

Optimization tools and simulation methods for designing and evaluating a mining operation

Some of the major advances in the field of mining in the last three decades have referred to the development of new design and planning techniques for optimizing open-pit mining and the inclusion of a stochastic perspective in economic models that is more revealing than a purely deterministic perspective. These advances include the use of parametric techniques in the design and planning process, the formulation of criteria for establishing an optimum cut-off grade policy when the economic goal is to optimize net present value (NPV), and the introduction of economic risk analysis. This paper examines some of the difficulties involved in applying these techniques—arising largely as a result of a lack of knowledge of the spatial location and distribution of the deposit grades—and analyses how these difficulties can be tackled with the help of geostatistical simulation techniques that take probabilistic criteria into consideration during the optimization process. These techniques enable equally likely representations of the deposit to be obtained that reproduce the main dispersion features for the starting experimental data (covariance or variogram, as well as the histogram). Consequently, the uncertainty in regard to the deposit as well as its influence on the economic assessment of the deposit in risk terms can be evaluated. This paper also describes a simple method for introducing price and cost increases into the risk analysis via the Monte Carlo method and shows how geological, technical and economic uncertainty can be integrated in risk analyses. Although it is true that the relationship between prices and costs is maintained constant in mining planning based on using parametric techniques, it is no less true that the risk analysis requires the use of models in which the main parameters with a bearing on deposit economics are considered as stochastic variables. The proposed methodology simplifies the calculations and easily integrates the different sources of uncertainty.

Optimization of nutrient component for diesel oil degradation by Rhodococcus erythropolis

A novel bacterium T7-2 was isolated from the oil-polluted sea-bed mud of Bohai Sea, northern China, which can degrade diesel oil at 15 °C. This bacterium was identified as a strain of Rhodococcus erythropolis according to its 16S rDNA gene. In order to enhance degradation efficiency, a five-level, three-factor central composite design was employed to optimize the nutrition supplied to artificial seawater. The results indicate that a supplement of 2.53 g (NH₄)₂SO₄ L⁻¹, 2.75 g Na₂HPO₄ L⁻¹ and 0.01 g yeast extract L⁻¹ to artificial seawater increases the degradation rate from 12.61% to 75% within 7 d.     

Mapping groundwater quality in the Netherlands

Maps of 25 groundwater quality variables were obtained by estimating 4 km × 4 km block median concentrations. Estimates were presented as approximate 95% confidence intervals related to four concentration levels mostly obtained from critical levels for human consumption. These maps were based on measurements from 425 monitoring sites of national and provincial groundwater quality monitoring networks. The estimation procedure was based on a stratification by soil type and land use. Within each soil-land use category, measurements were interpolated. Spatial dependence between measurements and regional differences in mean level were taken into account. Stratification turned out to be essential: no or partial stratification (using either soil type or land use) results in essentially different maps. The effect of monitoring network density was studied by leaving out the 173 monitoring sites of the provincial monitoring networks. Important changes in resulting maps were assigned to loss of information on short-distance variation, as well as loss of location-specific information. For 12 variables, maps of changes in groundwater quality were made by spatial interpolation of short-term predictions calculated for each well screen from time series of yearly measurements over 5–7 years, using a simple regression model for variation over time and taking location-specific time-prediction uncertainties into account.

From a policy point of view, the resulting maps can be used either for quantifying diffuse groundwater contamination and location-specific background concentrations (in order to assist local contamination assessment) or for input and validation of policy supporting regional or national groundwater quality models. The maps can be considered as a translation of point information obtained from the monitoring networks into information on spatial units, the size of which is used in regional groundwater models. The maps enable location-specific network optimization. In general, the maps give little reason for reducing the monitoring network density (wide confidence intervals).     

基于粒子群优化算法的叠前角道集子波反演

本文探讨了粒子群优化(PSO)算法在叠前地震角道集子波反演中的应用.在基本最优PSO算法的基础上,提出了对粒子更新速度进行平滑滤波的改进最优粒子群算法.由于代表子波的粒子的维数较大,如果粒子的各维元素相互独立,将导致粒子速度更新紊乱,影响搜索速度.通过对粒子速度进行三点均值滤波,加强了单个粒子各维元素的相互联系,并防止了粒子速度逃逸,使粒子更快地向有利于最优解的位置收敛.该方法应用于叠前角道集子波的反演中,取得了较好的子波反演效果,证明了本文方法的有效性.     

Determination of the suspension competence of debris flows based on particle size analysis

The determination of the critical particle size between solid and fluid phases, i.e., the suspension competence, is fundamental for debris flow. A method for determining suspension competence based on particle size analysis is presented in this paper. Suspension competence of static experimental water-debris mixtures prepared with the sediment of Jiangjia Gully is -0.025 mm if the bulk density is less than 1,800 kg m-3 and it increases with bulk density of more concentrated mixtures. Suspension competence of natural debris flows in Jiangjia Gully increases exponentially with the bulk density. These two data sets are compared in order to understand the suspension mechanism. It is concluded that turbulence may play a leading role in particle suspension in non-viscous and sub-viscous debris flows, while in viscous debris flows both matrix strength and excess pore water pressure play important roles.