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T.SONG Post-Doctoral Fellow School of Civil Structural Engineering Nanyang Technological University Nanyang Avenue Singapore . Presently Civil Engineer Engineering Depatment Technology Division Maritime Port Authority of Singapore. 《国际泥沙研究》1997,(3)
I.INTRODUCTIONBedloadtransportinsteadyuniformopenchannelflowhasbeenextensiVelystudied.Manyoftheformulasdevelopedforthepredictionofbedloadtransportinuniformopen-channelflowcanbebroughtinthefollowingform(ChienandWan,1983);ac=f(O)(l)xvhereacisthedimensionlessparameterofbedloadtranSPortandOisthedimensionlessparameterofflowintensity.TheseparametersaredefinedasfwheregsisthebedloadtranspoftratePerunitwidthindryweight;disthesedimentdiameter,Sisthebedslopeofthechannel;Rbisthehydraulicradiusdue… 相似文献
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We develop two algorithms for estimating member stiffnesses and masses of a structure from measured modal response in conjunction with a finite element model of the structure. The mathematical model has known geometry and topology and parameterized constitutive properties. A few of the natural frequencies are measured and the corresponding modes are sampled at certain locations in space. The proposed algorithms are based on the concept of minimizing the sum of the squares of errors, specified as an index of discrepancy between the model and the structure, over all of the measured modes. The recursive quadratic programming method is used to solve the non-linear constrained estimation problem. Both proposed estimators can handle incompletely measured models, have robust convergence, and are amenable to modelling of complex structures. We demonstrate the use of our parameter estimation algorithm by applying it to identify the properties of a building from measured data. 相似文献
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《Marine pollution bulletin》2014,78(1-2):412-417
Concentrations of PAHs, PCBs, metals and lipids in hepatopancreas of rock crabs (Cancer irroratus) were measured in Sydney Harbour (SH) for one year prior to remediation and three years of remediation of the Sydney Tar Ponds (STP), Nova Scotia. Low level concentrations of PCBs and metals were measured, although PAHs were mostly undetected. Metal concentrations showed little spatio-temporal variability, although highest concentrations of As, Cd and Cu were measured at reference stations furthest from the STP remediation site. Mercury concentrations were at least an order of magnitude lower than Canadian guidelines. Moderately elevated PCB concentrations were detected in crabs near Muggah Creek, but these were generally not higher than those measured during baseline. Despite remediation activities, current contaminant burdens measured in crabs were much lower than previously reported in other studies of crabs and lobster in industrial harbours in eastern Canada, due in part to natural recovery of SH sediments. 相似文献
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Comparison of Hydraulic Conductivity Values Obtained from Aquifer Pumping Tests and Conservative Tracer Tests 总被引：1，自引：0，他引：1
《Ground Water Monitoring & Remediation》2000,20(3):122-128
Afield site was established in an area of glacial outwash near Des Moines, Iowa. Hydraulic conductivity (K) of the outwash was measured in various ways including six pumping tests and two natural-gradient Cl- tracer tests. The velocity of the conservative tracer was converted to K using measured gradients and effective porosity determined from two radial-convergent Cl- tracer tests.
K values measured from the conservative tracer tests are approximately one-tenth to one-twentieth the average pumping-test value. Thus the K relevant to solute transport does not reflect the K measured by pumping tests. This discrepancy may be caused by the different scale and dimensionality of the two test types. Dispersion may prevent solutes from flowing exclusively within smaller high-conductivity paths which strongly affect the K measured by pumping tests. 相似文献
K values measured from the conservative tracer tests are approximately one-tenth to one-twentieth the average pumping-test value. Thus the K relevant to solute transport does not reflect the K measured by pumping tests. This discrepancy may be caused by the different scale and dimensionality of the two test types. Dispersion may prevent solutes from flowing exclusively within smaller high-conductivity paths which strongly affect the K measured by pumping tests. 相似文献
5.
Analysis of methods to estimate spring flows in a karst aquifer 总被引：2，自引：0，他引：2
Sepúlveda N 《Ground water》2009,47(3):337-349
Hydraulically and statistically based methods were analyzed to identify the most reliable method to predict spring flows in a karst aquifer. Measured water levels at nearby observation wells, measured spring pool altitudes, and the distance between observation wells and the spring pool were the parameters used to match measured spring flows. Measured spring flows at six Upper Floridan aquifer springs in central Florida were used to assess the reliability of these methods to predict spring flows. Hydraulically based methods involved the application of the Theis, Hantush-Jacob, and Darcy-Weisbach equations, whereas the statistically based methods were the multiple linear regressions and the technology of artificial neural networks (ANNs). Root mean square errors between measured and predicted spring flows using the Darcy-Weisbach method ranged between 5% and 15% of the measured flows, lower than the 7% to 27% range for the Theis or Hantush-Jacob methods. Flows at all springs were estimated to be turbulent based on the Reynolds number derived from the Darcy-Weisbach equation for conduit flow. The multiple linear regression and the Darcy-Weisbach methods had similar spring flow prediction capabilities. The ANNs provided the lowest residuals between measured and predicted spring flows, ranging from 1.6% to 5.3% of the measured flows. The model prediction efficiency criteria also indicated that the ANNs were the most accurate method predicting spring flows in a karst aquifer. 相似文献
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选取库尔勒地震台2008—2015年记录的数字地震资料,与中国地震台网测定的体波震级进行对比,从震级大小、震中距、震源深度以及震中方位,分析二者之间的关系。结果可知,库尔勒地震台计算震级相对偏大,其中mb平均偏差为0.1455,mB平均偏差为0.1941;震源深度在0—96km时,mb和mB震级偏差接近平均值;当震源深度h>96km时,测定震级和中国地震台网测定震级基本一致;地震发生在第三象限时,台站测定震级与中国地震台网测定震级基本一致。 相似文献
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A. Migné N. Spilmont G. Boucher L. Denis C. Hubas M.-A. Janquin M. Rauch D. Davoult 《Continental Shelf Research》2009
In order to provide an accurate annual rate of net benthic community production, community photosynthetic response to incident irradiance and respiration were measured at different times of the year, at mid-tide level on the muddiest part of the Mont Saint-Michel Bay. As the water turbidity prevented any photosynthesis by the microphytobenthos during immersion periods, primary production was measured only during emersion periods. In contrast respiration was expected to vary according to the tidal cycle and was measured during both emersion and immersion periods. Primary production and respiration rates under emersion were assessed using in situ infra-red gas analysis of CO2 exchange measured in a benthic chamber. Respiration rates under immersion were assessed through total CO2 concentration variations in incubated cores. 相似文献
9.
Information about electrical anisotropy in and around the deep borehole of the German Continental Deep Drilling Program (KTB) has been acquired using three different methods: (1) Under surface temperature and pressure conditions, the azimuthal dependence of resistivity has been measured in horizontal planes perpendicular to the axes of drill cores. (2) Simulated in-situ conditions (high temperature and pressure) have been applied to mini cores drilled at different orientations to structural features such as foliation. The resistivity was then measured in the direction of the mini cores' long axes. (3) Under quasi-in-situ (downhole) conditions, the azimuthal dependence of resistivity has been measured in horizontal planes using the Azimuthal Resistivity Imager (ARI), a down hole logging tool.These investigations have shown that electrical anisotropy is strongly related to structural features. The anisotropy of gneisses is the highest due to the strong foliation (averaged anisotropy factor 2.8). Lamprophyres are most isotropic (factor 1.2). Most rocks from KTB are amphibolites with intermediate anisotropies (factor 1.3). The anisotropies measured under surface temperature and pressure conditions and quasi-in-situ conditions on amphibolites are approximately the same, whereas anisotropies under simulated in-situ conditions are partially higher.Furthermore, the anisotropies measured on the cm to m scale using the various methods outlined above shall be compared with large scale anisotropies of the km scale measured around KTB using Magneto Tellurics. 相似文献
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太湖秋季水体遥感反射比的简单经验估测模型 总被引：2，自引：1，他引：1
2004年10月现场测量了太湖水体的遥感反射比、后向散射系数以及其他必要参数,实验室测量了水体的悬浮颗粒物质浓度.首先把太湖划分为3个大区,即遥感反射比受湖底影响的区域(影响区)、不受湖底影响的区域(非影响区)以及可能受湖底影响的区域(可能影响区),然后再把太湖分为高混浊、中混浊、低清澈以及高清澈等4类水体类型,分别列出了各种水体区域类型的相关属性数据.在整个太湖区域范围内,建立了后向散射和悬浮颗粒物质浓度的经验回归模型;仅在非影响区内,建立了遥感反射比和后向散射的经验回归模型,并可以利用悬浮颗粒物质浓度直接估测遥感反射比.最后详细分析了模型的精度. 相似文献
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Martin Wegehenkel 《水文研究》2005,19(6):1139-1164
The validation of soil water balance models and the evaluation of the quality of the model predictions at field‐scale require time‐series of in situ measured model outputs. In our study, we have validated such a model using a 6‐year period with time‐series of automatically recorded, daily volumetric soil water contents measured with the time‐domain reflectometry with intelligent microelements (TRIME) method and daily pressure heads measured with tensiometers. The comparisons of simulated with measured soil water contents and pressure heads were analysed using the modelling efficiency index (IA) and the square root of the mean square error (RMSE) in order to evaluate the prediction quality of the model. In our study, IA and RMSE, obtained either from the comparison of simulated with measured soil water contents or the comparison of calculated with observed pressure heads, in some cases lead to different results regarding the evaluation of the simulation quality of the soil water balance model. For example, a good fit between simulated and observed soil water contents does not necessarily result in a comparably good fit between the corresponding calculated and measured pressure heads. Therefore, a combined use of both measurement techniques, which takes into account their respective advantages and disadvantages, gives a more complete overview on the simulation quality of the soil water balance model than the single use of one of those techniques. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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M J Lebata 《Marine pollution bulletin》2001,42(11):1133-1138
Oxygen, sulphide and nutrient (ammonia, nitrite and phosphate) uptake of Anodontia edentula was measured. Oxygen and sulphide were measured from sealed containers provided with 1 l fresh mangrove mud (sulphide source) and seawater (oxygen source) with two treatments (with and without clam) at 16 replicates each. Oxygen, sulphide and other parameters were measured at days 1 (initial), 3 and 5 (final). Nutrients were measured from containers filled with 1.5 l wastewater from a milkfish broodstock tank with two treatments (with and without clam) at eight replicates each. Ammonia, NO2 and P04 were measured at days 0 (initial) 3, 6, 9 and 12 (final). Results showed significantly decreasing oxygen and sulphide concentrations in treatment with clams (ANOVA, p < 0.001). A significantly higher ammonia concentration (ANOVA, p < 0.05) was observed in treatment with clams while no significant difference was observed in nitrite and phosphate between the two treatments. A decreasing ammonia and an increasing nitrite trend was also observed in both treatments starting at day 3. 相似文献
15.
Yee Meng CHIEW 《国际泥沙研究》1992,(1)
This paper examines the effect of dune migration on local scour around bridge piers. Experiments show that local scour depths fluctuate in response to the translation of dunes past the scour hole. The scour depths measured in a model study conducted in live-bed conditions contain both scour due to the pier and that due to dunes. The con' tribution from scour due to the dunes may form a significant fraction of the total scour depth measured in model investigations. Therefore, it is imperative to separate these two components of scour for analysis and comparison. The study proposes that an equilibrium or time-average scour depth normalized using pier diameter be used for analysis, and the contribution from dunes to the total scour depth be added independently. Dune size, in the absence of field or measured data, may be estimated using published predictive curves. Comparisons between computed and measured scour depths show a good correlation, and 90% of all the data tested fall within a scatter of 15%. 相似文献
16.
地下水溶解气数字化观测程控定量自动脱气装置 总被引：4，自引：1，他引：3
介绍了一种适于与气体自动观测仪器配套、应用于地震地下水前兆数字化观测的定量自动脱气装置。该装置根据气体溶解平衡原理设计而成,采用了交联双循环技术,由单板机实现程序控制,可利用连续流经该装置的被测水样,周期性制备定量体积的与被测水样具有确定浓度关系的气态样品,供气体自动观测仪器进一步测量,并按照给定的理论公式,对被测水样中相关溶解气的真实浓度给出精确的定量表达。专门设置的“稳压功能”和“除水功能”使该装置具有较稳定的工作性能。 相似文献
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Sublimation is a critical component of the snow cover mass balance. Although sublimation can be directly measured using eddy covariance (EC), such measurements are relatively uncommon in complex mountainous environments. The EC measurements of surface snowpack sublimation from three consecutive winter seasons (2004, 2005 and 2006) at a wind‐exposed and wind‐sheltered site were analysed to characterise sublimation in mountainous terrain. During the 2006 snow season, snow surface and near‐surface air temperature, humidity and wind were also measured, permitting the calculation of sublimation rates and a comparison with EC measurements. This comparison showed that measured and simulated sublimation was very similar at the exposed site but less so at the sheltered site. Wind speeds at the exposed site were nearly four times than that at the sheltered site, and the exposed site yielded measured sublimation that was two times the magnitude of that at the sheltered site. The time variation of measured sublimation showed diurnal increases in the early afternoon and increased rates overall as the snow season progressed. Measured mean daily sublimation rates were 0.39 and 0.15 mm day?1 at the exposed and sheltered sites, respectively. At the exposed site, measured sublimation accounted for 16% and 41% of the maximum snow accumulation in 2006 and 2005, respectively. At the sheltered site, measured seasonal sublimation was approximately 4% in 2004 and 2006 and 8% in 2005 of the maximum snow water equivalent. Simulated sublimation was only available for 2006 and suggested smaller but comparable percentages to the sublimation estimated from observations. At the exposed site, a total of 42 mm sublimated for the snow season, which constituted 12% of the maximum accumulation. At the sheltered site, 17 mm (2.2% of maximum accumulation) was sublimated over the snow season. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Seepage rate and direction measured with a seepage metre modified for use in flowing water were greatly variable along a 300‐m reach of a shallow, gravel‐bed river and depended primarily on the local‐scale bed topography. The median value of seepage measured at 24 locations was 24 cm/day, but seepage measured at specific sites ranged from ?340 to +237 cm/day. Seepage also varied substantially over periods of hours to days and occasionally reversed direction in response to evolution of the sediment bed. Vertical hydraulic conductivity was related to seepage direction and was larger during upward seepage than during downward seepage; with differences ranging from 4 to 40% in areas of active sediment transport to more than an order of magnitude in areas where current was too slow to mobilize bed sediment. Seepage was poorly related to hydraulic gradient measured over vertical distances of 0·3 m and appeared to be opposite the hydraulic gradient at 18% of the locations where both parameters were measured. Results demonstrate the scale dependence of these measurements in coarse‐grained hyporheic settings and indicate that hydraulic gradients should be determined over a much shorter vertical increment if used to indicate exchange across the sediment–water interface. Published in 2009 by John Wiley & Sons, Ltd. 相似文献
19.
For four years measurements of solar radiation have been made with an instrument which observes the sky radiance in two spectral regions. The measured incident radiation is independent of the direction. Formulas are derived which allow to conclude the daily sun intensity in one region, knowing the measured intensity in the other region. The effect of ozone is noticeable in the difference between the measured and computed values in an ozone-absorbing region. The optical behaviour of the atmosphere can be defined by parameterization of extinction effects. From this one can conclude the intensity of any other spectral region and thus define selective influences of other absorbing gases like air-polluting constituents. 相似文献
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深入了解不同压力、频率、流体含量和流体分布对岩石中弹性波传播特性的影响,对指导油气勘探开发具有重要意义.不同尺度下的波致流效应,是声波传播过程中产生速度频散和衰减的重要原因.本文以不同压力下水饱和区域改进的骨架模量为纽带,建立了联合介观尺度斑块饱和效应与微观尺度喷射流效应的部分饱和岩石声学理论模型.开展针对性声学实验,根据不同压力下部分饱和砂岩纵波速度测量数据,确定理论模型中的相关参数,从而实现对不同压力下部分饱和岩石纵波衰减的定量表征.在此基础上,通过理论与实验测量的纵波衰减的对比,分析不同压力、含水饱和度以及频率对岩石纵波衰减的影响.研究结果表明,在较低压力,较高含水饱和度以及较高频段,喷射流效应较强,因此新建模型计算的衰减明显大于斑块饱和模型的衰减.由于新建模型体现了斑块饱和效应与喷射流效应的综合影响,相比于斑块饱和模型,新建模型计算的部分饱和岩石的纵波衰减更接近于实测衰减,但受到岩石自身因素影响,新建模型计算的衰减仍略小于实测衰减. 相似文献