Evaluation of a gravel transport sensor for bed load measurements in natural flows

A recent acoustic instrument （Gravel Transport Sensor, GTS） was tested for predicting sediment transport rate （bed load rate） in gravel bed streams. The GTS operation is based on the particle collision theory of submerged obstacles in fluids. When particles collide with the GTS cylinder their momentum is recorded in the form of ping rates. The GTS is attractive for further consideration here because of its potential to provide continuous unattended local bed load measurements, especially in areas found in streams that access may be difficult under extreme conditions. Laboratory experiments coupled with numerical simulations for the same flow conditions were performed in order to determine the conditions under which particles of different size will hit the GTS cylinder and be able to register a ping rate. The GTS was able to detect the number of particles with diameter in the range of 15.9 to 25.4 mm, with reasonable accuracy, if the applied Shields effective stress τ＊e = τ＊ - τ＊cr was in the range of 0.006 to 0.015. A drawback of the tested prototype GTS, however, was that it exerted increased resistance on the incoming particles. The added drag effects increased the overall resistance that was exerted by the flow on particles and thus increased the likelihood that particles will rest in the ambient region of the cylinder instead of hitting it. Numerical simulation of the flow around the GTS cylinder revealed that changing the prototype geometry from cylindrical to ellipsoid or rhomboid will increase the likelihood of the particles hitting the instrument under the same flow conditions failed by the original tested GTS cylinder.     

Evaluation of total load sediment transport formulas using ANN

The calculated results from various sediment transport formulas often differ from each other and from measured data. Some parameters in the sediment transport formulas are more effective than others to estimate total sediment load. In this study, an Artificial Neural Network （ANN） model is trained using four dominant parameters of sediment transport formulas. ANN models are able to reveal hidden laws of natural phenomena such as sediment transport process. The results of ANN and some total bed material load sediment transport formulas have been compared to indicate the importance of variables which can be used in developing sediment transport formulas. To train ANN, average flow velocity, water surface slopes, average flow depth, and median particle diameter are used as dominant parameters to estimate total bed material load. Two hundreds and fifty samples are used to train the ANN model. Twenty-four sets of field data not used in the training nor calibration of ANN are used to compare or verify the accuracy of ANN and some well-known total bed material load formulas. The test results show that the ANN model developed in this study using minimum number of dominant factors is a reliable and uncomplicated method to predict total sediment transport rate or total bed material load transport rate. Results show that the accuracy of formulas in descending order are those by Yang （1973）, Laursen （1958）, Engelund and Hansen （1972）, Ackers and White （1973）, and Toffaleti （1969）. These results are similar to those made by ASCE （1982） based on laboratory and field data not used in this paper. Study results also show that the formulas based on physical laws of sediment transport, like those formulas that were developed based on power concept, are more accurate than other formulas for estimating total bed material sediment load in rivers.     

海岛重力测量负荷改正及其影响因素分析

利用927工程海岛绝对重力测量数据,研究了海潮负荷改正计算软件、海潮模型以及地球模型三因素对绝对重力海潮负荷改正的影响。根据计算结果,观测期间由不同海潮负荷计算软件造成的海潮重力值差异可达5.985 7μGal,不同海潮模型的差异可达2.532 7μGal,不同地球模型的差异可达5.928 3μGal。结论认为,在海岛绝对重力测量数据处理中,必须充分考虑以上因素造成的海潮负荷改正差异。     

电力负荷与气象要素相关分析

根据鹤壁市1996～2000年逐日电力负荷资料和气象资料，分析了电力负荷与各种气象因子之间的相关关系，结果表明：电力负荷总量呈现出明显的季节性变化，并且与多种气象因子存在较好的相关性。     

中空纤维膜作生物膜载体无泡供氧处理污水研究

采用中空纤维膜作生物膜载体及无泡供氧装置,利用具有死端式和漂浮式特点的浸没式接触氧化工艺进行污水处理试验研究.结果表明:在控制系统工作压力0.03 MPa、污水中ρ(DO)为5～8 mg/L及HRT＝8h的条件下,污水中COD、BOD、SS的去除率分别达70%、90%和75%以上,NH3 -N、P的去除率也在70%以上.系统连续运行3个月,表现了较好的稳定性和抗有机负荷冲击能力.     

佘山台倾斜固体潮观测的海潮负荷改正

采用FARRELL的负荷理论以及最新的TPXO6海潮模型和中国近海潮汐资料计算了海潮负荷对佘山台倾斜固体潮的影响,采用BAYTAP-G调和分析软件对佘山台倾斜固体潮观测进行了处理,获得不同潮波的潮汐参数。在此基础上进行海潮负荷改正。负荷改正后,东西分量的振幅因子和相位滞后与理论值较为接近,而南北分量的半日波振幅因子与理论值仍有较大的偏离。结果说明,佘山台倾斜东西分量主要受海潮负荷的影响,超过60%,甚至达到96%(O1);而南北分量受到的非潮汐的影响要比东西分量受到的影响大,如N2波甚至高达70%,但是这也可能是和海潮模型在近海的不精确有关。     

长江三峡库区干流水体主要污染负荷来源及贡献

目前三峡水库枯水期已有11.1%的监测断面水质超标。城区江段岸边水质已出现较为严重的污染带。利用面向环境问题的污染负荷计量方法,对长江三峡库区干流水体主要污染负荷来源及贡献进行了分析。结果表明,富营养化污染负荷2003年总量为2.79万t PO₄3-当量,其中总磷贡献量最大,占总量的45.8%。其次是总氮和COD_Cr,分别占37.9%和16.4%。城市生活污水和农业施肥是主要来源,分别占总量的61.0%和26.3%。水生生态毒性污染负荷为7 612.6t 1,4-二氯苯当量。其中挥发酚和汞贡献量分别占78.0%和21.2%。来自城市生活污水占76.52%,重点工业企业的占23.48%。富营养化污染负荷有逐年增加趋势。重点工业企业六价铬和铅,城市污水中挥发酚水生生态毒性污染负荷增加较快。     

流域污染负荷模型的比较研究

对美国目前常用的一些用于流域总量管理的数学模型进行了概括分类,把收集到47个模型划分为流域负荷模型、受纳水体模型和集成化模拟系统三类,并选择其中的19个流域污染负荷模型作为重点进行了比较研究。针对这19个模型,首先对各模型的主要输入数据、模型主要的输出信息、模型所能处理的土地利用类型、模型中水文侵蚀和沉积物的计算机理、污染负荷计算结果的基本形式、所能模拟的污染物类型、模型的时间尺度特征、模型软件的提供者等9个方面作了较为详细的介绍。在此基础上,结合文献调研和对部分模型实际使用的效果,从模型处理不同土地利用类型(包括对流域点源的识别和处理)的适用性、对不同时间尺度的适应性、水文过程的模拟能力、不同类型污染物负荷的计算能力、对污染物运移过程的描述、模型结果输出的友好性、输入数据的需求程度、评估和设计污染总量管理措施的支持能力、以及使用说明文档的完备性等9个方面,对模型性能进行了定性评估,分别用“高”、“中”、“低”来表示模型的优劣程度。     

地表水非点源污染负荷计算方法探讨

以多年河流统计监测资料为基础,运用两点法,考虑非点源影响,逆推计算,求得地表水非点源污染负荷。以吉林省为例,分析了吉林省4大水系15条河流65个监测断面2000~2004年统计资料,运用两点法确定吉林省主要河流COD衰减系数(K),逆推计算得到吉林省非点源污染负荷为1443.711m3/s,其中松花江水系802.93m3/s,图们江水系108.369m3/s,辽河水系372.392m3/s,浑江、鸭绿江水系160.02m3/s。非点源污染负荷是点源污染负荷的57.14倍,成为吉林省地表水环境主要污染源。     

地表流体变化对我国地壳垂直形变的影响

研究了大气、海洋、土壤水与积雪质量变化对我国25个GPS基准站地壳垂直形变的影响。谱分析结果表明，垂直形变周期为12个月，半周期为6个月，基准站高程主要表现为季节性变化，最大可达20mm。通造对负荷效应与GPS监测结果的相关分析和显著性检验可知，96％的基准站相关系数在99％的置信度水平上，也说明两者有较强的线性相关关系。