场地地下水中氯代甲烷烃自然衰减机制

自然衰减监控技术在农药污染场地的实践应用较少,作用机制尚不明确.为此,以农药污染场地监控自然衰减实际工程案例为基础,对地下水中氯代甲烷烃的自然衰减能力、作用机制及降解时间进行了分析.Mann-Kendall趋势检验结果表明,作为污染源的MW1-17点位地下水中的四氯化碳和氯仿随时间呈现下降趋势,在4 a内降解率分别在9...     

机械故障振动信号征兆提取方法

在机械状态监测与故障诊断中，故障征兆的提取是关键环节，本文将介绍几种效果较好的故障征兆提取方法。     

Effects of Bridge Shading on Estuarine Marsh Benthic Invertebrate Community Structure and Function

The effect of bridge shading on estuarine marsh food webs was assessed by comparing benthic invertebrate communities beneath seven highway bridges with marshes outside of bridge-affected areas (reference marshes). We used light attenuation and height–width ratio (HW ratio), which takes into account the two main bridge characteristics that determine the degree of shading, to quantify the impact of shading on invertebrate communities. Low bridges, with HW ratio <0.7 and light attenuation greater than 85–90%, had benthic invertebrate densities and diversity that were significantly lower than reference marshes. Density of benthic invertebrates at low bridges was 25–52% (29,685–72,920 organisms/m²) of densities measured in adjacent reference marshes (119,329–173,351 organisms/m²). Likewise, there were fewer taxa under low bridges (5.8/11.35 cm² core) as compared to the reference marshes (9.0/11.35 cm² core). Density of numerically dominant taxa (e.g., oligochaetes and nematodes) as well as surface- and subsurface deposit feeders also were reduced under low bridges. Decreased invertebrate density, diversity, dominant taxa, and alterations of trophic feeding groups beneath low bridges was correlated with diminished above- and below-ground macrophyte biomass that presumably resulted in fewer food resources and available refuges from predators. With a greater knowledge of bridge shading effects, bridge construction and design may be improved to reduce the impacts on estuarine benthic invertebrate communities and overall ecosystem structure and function.     

A GIS-based approach for the long-term prediction of human health risks at contaminated sites

A Health Index/Risk Evaluation Tool (HIRET) has been developed for the integration of risk assessment and spatial planning using GIS capabilities. The method is meant to assist decision makers and site owners in the evaluation of potential human health risk with respect to land use. Human health risk defined as the potential adverse effects on human life or health is generally accepted as the most important aspect for site assessment and planning of remediation strategies. It concerns polluted sites that endanger human health on one hand and derelict land that does not cause the immediate risk on the other hand. In current state-of-the-art risk-assessment, long-term spatial and temporal changes of risks, in relation to changes in contamination patterns and land use functions, are not taken into account. The aim of this paper is to demonstrate the methodology developed for human health risk assessment in aspect of spatial and temporal domain. HIRET was developed as an extension for ESRI software ArcView 3.2 and allows performing dynamic human health risk assessment in long-term period, which is relevant for land use planning. The paper illustrates how such methodology can assist in environmental decision-making to enhance the efficiency of contaminated land management. A case study of contaminated site is given showing how data can be used within a GIS framework to produce maps indicating areas of potential human health risk.     

Accuracy improvement of various short-term load forecasting models by a novel and unified statistical data-filtering method

ABSTRACT

Time-series and machine-learning methods are being strongly exploited to improve the accuracy of short-term load forecasting (STLF) results. In developing countries, power consumption behaviors could be suddenly changed by different customers, e.g. industrial customers, residential customers, so the load-demand dataset is often unstable. Therefore, reliability assessment of the load-demand dataset is obviously necessary for STLF models. Hence, this paper proposes a novel and unified statistical data-filtering method with the best confidence interval to eliminate unexpected noises/outliers of the input dataset before performing various short-term load forecasting models. This proposed novel data-filtering method, so-called the data pre-processing method, is also compared to other existing data-filtering methods (e.g. Kalman filter, Density-Based Spatial Clustering of Applications with Noise, Wavelet transform, and Singular Spectrum Analysis). By using an SCADA system?-based database of a typical 22kV distribution network in Vietnam, NYISO database, and PJM-RTO database, case studies of short-term load forecasting have been conducted with a conventional ARIMA model, an ANN forecasting model, an LSTM-RNN model, an LSTM-CNN combined model, a deep auto-encoder (DAE) network, a Wavenet-based model, a Wavenet and LSTM hybrid model, and a Wavelet Neural Network (WNN) model, which are to validate the novel and unified statistical data-filtering method proposed. The achieved numerical results demonstrate which the accuracy of the aforementioned STLF models can be significantly improved due to the proposed statistical data-filtering method with the best confidence interval of the input load dataset. The proposed statistical data-filtering method can considerably outperform the existing data-filtering methods.     

石油烃类污染物在地下水中自然衰减特性

污染物在地下水中的自然衰减是目前解决地下水污染问题的一个重要的研究领域，是地下水污染生物修复的基础课题，本文以地下水中的常见污染物石油烃为对象，着重阐述该物在地下水中的自然衰减特性。根据所获取的国内外资料，介绍了其自然衰减的三种动力学方程：Monod动力学方程，一级衰减动力学方程和瞬时反应动力学方程，并且对于石油烃的自然衰减速率进行了详细的描述，为以后的研究提供参考。     

低应变反射波法基桩动测资料分析中的若干问题探讨

本文对低应变反射波法基桩动测资料分析中存在的信号分析方法、尺寸效应、桩周土的影响等问题的最新研究进展进行了分析,并且对相应问题给出了一些建议和可能的解决方法.     

声波吹灰器在锅炉吹灰中的应用

扬子热电厂7#锅炉通过对吹灰器正确地选型以及因地制宜地安装改造,解决了吹灰系统长期不能投用的问题并发挥了较好的吹灰效果。吹灰器改造后的运行统计数据,验证了投用声波吹灰器对提高锅炉效率和锅炉安全性能有明显作用,具有推广意义。     

山体尾流对烟羽扩散影响的风洞实验

本文以中性模拟的相似参数为判据,用四种不同的方法探测组合山体的流场.根据探测结果,探讨了尾流的结构并进行了较细致的区划.指出复杂地形的摩擦速度(u~*)在近地层不为常数.文中还讨论了尾流中扩散参数的变化及烟羽轴线下倾角分布,指出用修正的高斯烟羽模式描述尾流浓度场的可行性.风洞的实验结果与现场实验结果基本一致.     

爆炸性气体在连续拐弯管道中传播特性的实验研究

针对复杂燃气管网燃气爆炸致灾严重,传播规律复杂的问题,利用实验室加工成的连续拐弯管道,模拟研究了复杂燃气管网爆炸性气体通过连续拐弯管道时的火焰传播速度、爆炸波超压变化情况。研究结果表明,当整个管道内充满瓦斯气体时,通过连续拐弯后,火焰传播速度和爆炸波超压值产生显著变化,在连续拐弯管道拐弯处为一扰动源,诱导附加湍流,气流湍流度增大,管道拐弯增加了燃烧区的湍流度,火焰燃烧产生加速度,加速燃烧产生更大能量以推动加速传播。研究结果对指导现场如何防治复杂燃气管网气体爆炸,减轻爆炸的威力具有重要作用。