Mitigation of Salinity Intrusion in Well-mixed Estuaries by Optimization of Freshwater Diversion Rates

The diversion of fresh water from estuaries for agricultural and municipal uses leads to an upstream shift in the brackish water zone that can disrupt ecosystems and deteriorate water quality at downstream points. Models are routinely used to predict hydrodynamic and water quality conditions in estuaries, and presented here is a modeling approach that ultimately could prove helpful in designing strategies to divert fresh water while mitigating changes in salinity further downstream. An optimization problem is formulated whereby a least-squares function of the salinity distribution predicted by the model is minimized by optimizing a parameter vector describing the diversion rate as a function of time. The optimization method is shown to rapidly identify diversion schedules in a range of test systems. Optimization is performed by a quasi-Newton method that utilizes a Broyden–Fletcher–Goldfarb–Shanno update, and an adjoint sensitivity method is formulated and applied to evaluate the gradient of the objective function with respect to the parameter vector. The sensitivity of salinity levels to diversion rates is predicted to have both intratidal and intertidal variability, giving insight into the potential for diversions at any given time and any location along an estuary to have either a rapid or longer-term effect on the salinity distribution. The controllability of salinity levels by fresh-water diversions is directly related to these sensitivities.     

液压系统管路冲洗方法分析与改进

结合生产实践,对高压大流量冲洗、系统带阀台冲洗、带蓄能器伺服系统冲洗、高温冲洗及提高绝对过滤精度的档次及纳污容量等冲洗手段进行了分析与改进,提高了液压系统的清洁度。     

Quantifying Levels of Wasted Time in Construction with Meta-Analysis

Quantifying the waste present in an operation is an important part of a number of performance improvement initiatives in the architecture engineering construction industry. Contemporary management approaches focus on waste minimization to reduce operating costs and to increase operating responsiveness and flexibility. In construction, studies have been conducted over the past 30?years as part of productivity-improvement efforts that have documented levels of wasted time in construction activities. This paper draws on the methodology of meta-analysis to provide a synthesis of the findings across all of these studies. The analysis reveals that an average of 49.6% of time in construction is devoted to wasteful activity, although this amount is widely varied. Among other things, these results demonstrate considerable potential for improvement in construction through initiatives that reduce levels of wasteful activity.     

Probabilistic Critical Excitation Method for Earthquake Energy Input Rate

Since earthquake ground motions and their input effects on structures are very uncertain even with the present state of knowledge, it is desirable to develop a “robust” structural design method taking into account these uncertainties. Approaches based on critical excitation methods have been proven to be promising for such robust structural design. A new critical excitation method is developed here in which the mean earthquake energy input rate is chosen as a measure of criticality. The earthquake energy input rate is closely correlated with the story deformation and this supports the suitability of the energy input rate as a criticality measure in the case where the deformation is crucial in the design. The ground motion is described as a uniformly modulated nonstationary random process. The power [area of power spectral density (PSD) function] and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. The key for finding the new random critical excitation is the interchange of the order of the double maximization procedures with respect to time and to the PSD function. Examples for a specific envelope function of the ground motion are presented for demonstrating the validity of the proposed method. Extension of the proposed method will be discussed for a more general ground motion model, i.e., nonuniformly modulated nonstationary models, and for a more general problem for variable envelope functions and variable frequency contents.     

Simulating Entrainment and Particle Fluxes in Stratified Estuaries

Settling and entrainment are the dominant processes governing noncohesive particle concentration throughout the water column of salt-wedge estuaries. Determination of the relative contribution of these transport processes is complicated by vertical gradients in turbulence and fluid density. A differential-turbulence column (DTC) was designed to simulate a vertical section of a natural water column. With satisfactory characterization of turbulence dissipation and saltwater entrainment, the DTC facilitates controlled studies of suspended particles under estuarine conditions. The vertical decay of turbulence in the DTC was found to obey standard scaling law relations when the characteristic length scale for turbulence in the apparatus was incorporated. The entrainment rate of a density interface also followed established grid-stirred turbulence scaling laws. These relations were used to model the change in concentration of noncohesive particles above a density interface. Model simulations and experimental data from the DTC were consistent over the range of conditions encountered in natural salt-wedge estuaries. Results suggest that when the ratio of entrainment rate to particle settling velocity is small, sedimentation is the dominant transport process, while entrainment becomes significant as the ratio increases.     

Formula for Sediment Transport in Rivers, Estuaries, and Coastal Waters

The aim of the present study is to develop a formula for the relationship between flow strength and sediment discharge. The appropriate definition of energy dissipation rate E in the theorem of Bagnold in 1966 is discussed and it is found that the sediment transport rate gt in unidirectional flows can be well predicted when E is defined as the product of bed shear stress τ0 and near bed velocity u*′. Then the linear relationship between u*′E and the sediment transport rate is examined using measured data. The good agreement between measured and predicted values indicates that the phenomena of sediment transport can be reasonably described by the near bed flow characteristics. As the hydrodynamic modelers are able to calculate the bed shear stress and near bed velocity in various cases now, thus the new relationship may provide numerical modelers a tool to calculate the sediment transport in rivers, estuaries and coastal waters. To prove this, the simplified analytical expressions of E and u*′ in wave-current flows and coastal waters are derived, the results are checked with the available data over a wide range of flow conditions; and good agreements are achieved, indicating that the presumption is valid in the cases investigated.     

用LEC法量化PHA中危险等级的应用研究

介绍了预先危险性分析法（PHA）的应用步骤、实现方法，用作业条件危险性评价法（LEC）结合企业现状定性分析定量计算确定预先危险性分析中的危险等级，并以某矿山采矿方法的安全评价为例，具体说明了用LEC法确定危险等级的PHA法在工程中的应用。     

高炉水冲渣系统节能改造

为了有效降低高炉冲渣系统动力运行成本,采取焦化废水替代新水、高炉渣沟密封、应用管改沟、提高冲渣水泵运行效率、利用冲渣循环水余热等措施,有效降低了高炉冲系统水电动力成本,同时降低了生活区域蒸汽消耗量,年节约动力成本2 000余万元。     

Dimensionless Approach for the Design of Flushing Gates in Sewer Channels

The various hydraulic and environmental problems related to the accumulation of solids have recently drawn increasingly attention to deposits in the management of sewer systems. Among the mechanical and hydraulic devices used for deposit removal, hydraulic flushing gates have proved to be a cost-effective solution and have been adopted in several sewer networks. This paper reports the results of an investigation on the scouring performance of flushing waves produced by hydraulic flushing gates. A numerical model based on the De Saint Venant–Exner equations in dimensionless form was validated by using data derived from laboratory experiments and was then utilized in this investigation. Simulations were carried out considering various values of the dimensionless parameters involved in the analysis, in order to obtain indications for the design and positioning of flushing devices in sewer channels. The problem of optimal flushing frequency was also investigated.     

BIEM Modeling of 3D Circulation and Transport in Stratified Estuaries

Here the boundary integral equation method (BIEM) is used for 3D modeling of hydrodynamics and pollutant transport in stratified estuaries. The flow computations are made using a newly developed BIEM solution. The transport modeling has been done using an Eulerian-Lagrangian BIEM (ELBIEM) model. In ELBIEM, the advection part in the transport equation is treated by the concept of the Eulerian-Lagrangian scheme, which overcomes the limitation of traditional BIEM to deal with an arbitrary velocity field. The coupling of the 3D shallow water BIEM model and advection-diffusion ELBIEM model enables one to effectively deal with fluctuation of free surface and density stratification in an estuary. The main advantages of the BIEM model include reduction in computational dimensions, ease in discretization and data preparation, accurate free surface simulation, less numerical diffusion and dispersion problems, and direct flux solution at boundaries. The numerical simulation results are compared with other model results and found to be satisfactory. The illustrated case study shows the effectiveness of the model in the simulation of mass, momentum, and heat transfer due to air-water interaction in stratified estuary problems.     

Automated Sewer and Drainage Flushing Systems in Cambridge, Massachusetts

This paper summarizes the design of passive automatic flushing systems installed in the City of Cambridge’s storm and sanitary sewer system tributary to the Alewife Brook as part of a $75 million sewer separation program. Grit and debris deposition is severe in the existing combined sewers, storm drains, and sanitary trunk sewers due to the flat topography of the area. This condition is exacerbated by hydraulic constraints imposed on the system’s outlet by the Alewife Brook (shallow stream) and downstream sanitary siphons (again because of the Alewife Brook). The use of pumps to lift flows from sewers and drains to permit self-scouring velocities is prohibitively expensive. To overcome this problem, five automated flushing systems using quick opening (hydraulic operated) gates discharging collected stormwater were constructed in conjunction with downstream collector grit pits covering a distance of 1,604 m for storm drain pipes ranging from 1.4 m circular to 1.2 m by 1.8 m rectangular. New 450 and 600 mm sanitary trunk sewers, 561 m long, will be flushed daily by two flushing systems using spent filtrate water from Cambridge’s water treatment plant recently constructed nearby. The flushing systems are sized to achieve wave velocity of 1 m/s at the end of the flushing segment. The flush vault volumes range from 11 to 40?m3 for the storm drain systems and 6?m3 for the sanitary system. Construction was completed in May 2002 and functional testing of the flushing systems is in progress. Partial test results are reported.     

福生水电站冲沙闸水工模型试验研究

根据福生水电站冲沙闸佛氏数低消能效果差的特点,采用物理横型试验方法对冲沙闸的泄流能力、水面线、流态、消能效果及对下游河道冲刷影响进行了试验研究,提出了优化后的消耗建筑物型式和结构尺寸,为设计提供了依据.     

Integrated Framework for Quantifying and Predicting Weather-Related Highway Construction Delays

Constant exposure to the environment makes highway construction highly dependent on weather. However, highway construction contracts are often unclear about the potential influence of weather-related delays on highway construction project schedules. There is a need to discourage litigation arising from weather-related delays by including in contracts a reasonable number of nonwork days as a consequence of adverse weather and providing an equitable criteria for the course of action when the predictions in the contracts turn out to be inaccurate. To address this need, an integrated framework consisting of the following two key components is proposed: (1) identification of attributes of weather that cause construction delays and (2) generation of synthetic weather sequences using a stochastic weather generator to quantify and provide probabilistic forecasts of weather threshold values. The utility of this framework is demonstrated through its application to construction work on a project in Texas. The use of probabilistic forecast of construction delay attributes provided by a semiparametric weather generator in this research is an example of interdisciplinary study to help address this problem. The result of the research is better decision support for agencies who wish to author contracts that more equitably allow for the influence of weather during construction.     

Metrics for Quantifying the Similarities and Differences between IFC Files

Recently, several papers reported problems in data exchange using industry foundation classes (IFC). However, most comparisons were made based on a visual check, a manual count, and observation of properties that were selectively chosen. This study proposes a set of metrics for quantifying the similarities and differences between IFC files. The proposed metrics include the similarity rate, the matching rate, the globally unique identifier (GUID) preservation rate, the missing rate, and the addition rate. A long-term goal of this study is to develop a set of metrics for quantifying the information exchange rate between two IFC files. Automated identification of modified information versus newly generated information is an unsolved challenge. The proposed metrics were used in analyzing 88 IFC files generated from different systems to demonstrate the potential use of the proposed metrics.     

大线能量焊接用厚钢板的发展

1　前言厚钢板的重要特性是焊接性能 ,而焊接效率则尤其重要 ,因此从降低结构钢板的建设成本来看 ,最大的课题就是大线能量焊接钢板的应用。当钢板使用大线能量焊接时 ,由于焊接部 ,尤其是焊接热影响区 ( HAZ)的韧性会随焊接线能量的增大而变差 ,因此为确保结构钢板的安全性 ,重要的课题就是要确保结构钢板的韧性。造船行业为适应大量物流时代的到来 ,需要建造大型船舶 ;城市发展 ,需要建超高层大楼和大型桥梁等 ,为适应这些建设对厚钢板的强度和韧性要求不断提高的需要 ,已相继开发了新型大线能量焊接用钢板。大线能量焊接技术是以造船行…     

Enhanced Soil Flushing for Simultaneous Removal of PAHs and Heavy Metals from Industrial Contaminated Soil

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are environmental concerns and must be removed to acceptable levels. This paper evaluates different flushing agents to enhance the remediation of soil contaminated with PAHs and heavy metals at a former manufactured gas plant site. Four flushing column tests at a constant hydraulic gradient of 1.2 were conducted using four different flushing agents, which included deionized water, chelant (0.2?M EDTA), surfactant (5% Igepal CA-720), and cyclodextrin (10% hydroxypropyl-β-cyclodextrin or HPCD). Additional column tests using Igepal and HPCD at a lower hydraulic gradient of 0.2 were conducted to investigate the effects of rate-limited desorption or solubilization of PAHs. The results showed that the EDTA produced the maximum metal removal from the soil compared with deionized water, Igepal, and HPCD under different hydraulic gradient conditions. The 0.2?M EDTA flushing solution removed approximately 25–75% of the toxic heavy metals found in the soil. None of the PAHs were removed from the soil when deionized water and EDTA were the flushing solutions. The PAHs removal efficiencies in the Igepal and HPCD systems decreased as the hydraulic gradient decreased. However, the surfactant-enhanced systems were more efficient in removing PAHs from the soil than the HPCD systems under high- and low-hydraulic gradients. The results also demonstrated that the removal of PAHs in surfactant-enhanced systems depended upon the micelles formation, whereas in the HPCD-enhanced systems, it depended upon the sterioselective diffusion of the PAHs to the nonpolar cavity of the HPCD. Overall, this study showed that the contaminant removal in soil flushing systems depends on the flushing solution affinity and selectivity toward the target contaminant and the existing hydraulic gradient condition.     

Performances of Hydraulics and Bedload Sediment Flushing in Rigid Channel Using Surge Flows

This paper presents an investigation of the performance of the hydraulic and sediment removal of a flushing system in a detention basin. A hydraulic criterion for the design of the flushing system is proposed. An equation for the maximum height of the flushing wave front as a function of the distance from the gate, the initial water depth in the chamber, and the chamber length is proposed. The Lauber and Hager equation for the maximum velocity of a flushing wave is also verified. Effective removal of sediment particles on the bed is a direct function of the bed shear stress generated by the flushing flow. This study reveals that the bed shear stress on the channel bed induced by the flushing flow can be attributed to the hydrostatic pressure, the flow acceleration, and the convection-induced momentum. The shear stress associated with fluid distortion and the turbulent viscosity may be neglected. Significant error would occur if the hydrostatic pressure component were used as an estimate of the bed shear stress on a mild slope channel. The energy slope method may provide an overestimate of the bed shear stress. Finally, an appropriate equation to evaluate the maximum bed shear stress is proposed.     

Quantifying Uncertainty in Estuarine and Coastal Ocean Circulation Modeling

A methodology is developed to describe the effect of errors (or uncertainty) in the specification of certain drivers (bathymetry, river inflow, and wind speeds) on the circulation computed by a three-dimensional estuarine and coastal hydrodynamic circulation model. The methodology is based on first order variance analysis. Two analytical examples are used to illustrate the method and to provide a context for interpreting real world settings. An application of the method to a model of the N.Y./N.J. Harbor Estuary shows that current predictions are considerably sensitive to the accurate specification of bathymetry, and are usually more sensitive than water level predictions to errors in bathymetry. Estuarine properties with a strong seasonal (or spatial) component such as temperature or salinity did exhibit a sensitivity to driver accuracy that shifted from one season (or regime) to another. Bathymetry appears to control the circulation of the N.Y./N.J. Estuary more than the dynamic forcing of the winds and the Hudson River inflow, perhaps due to the fact that the estuary is primarily tidally driven.