改性污泥替代垃圾填埋场覆土的研究

以市政污泥为研究对象,采用固化剂对污泥进行改性,通过分析不同固化剂添加比例下固化产物的抗压强度和渗透系数,比较不同养护时间下污泥固化产物浸出液的COD、氨氮和重金属性质,探讨市政污泥固化产物作为垃圾填埋场覆土可行性。实验结果表明：固化剂添加比例为30％的固化产物抗压强度高于50kPa,其渗透系数达到10^-7cm／s数量级,基本满足覆土材料的标准要求。污泥固化产物重金属的最大浸出量远远低于《污水综合排放标准》（GB8978-88）中一级排放标准。随养护时间延长,固化产物浸出液COD和氨氮浸出浓度亦呈下降趋势,重金属Pb、Cd浸出量明显减少,浸出比例小于1％。养护有利于降低固化产物的浸出污染程度,30％的污泥固化产物养护3d后可作为垃圾填埋场日覆盖材料。     

The relationship between blood alcohol concentration (BAC), age, and crash risk

PROBLEM: The role of age (youth and driving inexperience) and alcohol as major risk factors in traffic crash causation has been firmly established by numerous studies over the past 50 years. Less well established is how the two variables interrelate to influence crash risk. Some investigations have hypothesized an interactive or synergistic effect in which young drivers with less experience and a greater tendency to take risks are more adversely affected at lower blood alcohol concentrations (BACs) than are older drivers. The evidence for this hypothesis is mixed. Resolution of this issue has important implication for developing countermeasures directed at the young driver crash problem. METHOD: Case control data previously collected in Long Beach and Fort Lauderdale were reanalyzed using a more sensitive method for detecting interaction effects than used in the original analysis. A conditional logistic regression analyses found a highly significant agexBAC interaction (P<.0001) involving differences between drivers under 21 and those 21 and older. DISCUSSION: The results clearly indicate that positive BACs in drivers under 21 are associated with higher relative crash risks than would be predicted from the additive effect of BAC and age. It is likely that two mechanisms are operating to cause the interaction. First, it seems likely that the crash avoidance skill of young novice drivers would be more adversely affected by alcohol due to their driving inexperience, immaturity, and less experience with alcohol. Second, drivers under 21 who choose to drink and to drive after drinking probably have pre-existing characteristics that predisposed them to risk taking and crash involvement apart from any increased vulnerability to alcohol impairment. IMPACT ON INDUSTRY: The results support increased enforcement of zero-tolerance BAC laws for minors.     

Risks older drivers pose to themselves and to other road users

Problem

Studies have shown that older drivers have high death rates and lower rates of involvement in crashes that kill others; but most studies have not considered drivers' responsibility for their crashes, and many have considered only one particular measure of risk.

Method

This study examines risks that drivers of various ages pose to themselves and to others on per-driver, per-trip, and per-mile bases, taking responsibility for crashes into account, using United States fatal crash data from 1999 through 2003 and travel estimates from 2001.

Results

Relative to other age groups, drivers aged 85 and older face the highest risk of their own death, whereas teens pose the greatest risk to passengers, occupants of other vehicles, and non-motorists.

Discussion

The oldest drivers pose more risk to other road users than middle-aged drivers do; the degree of their excess risk depends strongly upon how risk is measured.

Impact on industry

These results demonstrate the importance of keeping clear the meaning and implications of various risk measures.     

采空区渗透率分布对流场的影响

根据多孔介质渗流理论,利用计算流体力学软件Fluent,设定采空区渗透率为均匀分布、分段均匀分布和连续性分布,分别模拟这3种情况的采空区漏风流场。当渗透率均匀分布时漏风量小,自燃带靠近工作面。渗透率分段均匀分布时,速度在分区界面上产生跳跃。采空区渗透率连续分布条件下的漏风分布与假设分段均匀分布和均匀分布条件下的漏风量、漏风风速分布和自燃三带的位置和宽度有很大差别。结果表明,只有采用更能如实反映采空区岩石冒落和压实规律的渗透率分布,得到的采空区的风流流动规律才更符合实际。     

采空区渗透率对瓦斯运移影响的模拟研究

根据计算流体力学基本理论,利用Fluent软件,对采空区渗透率为均匀分布、分段均匀分布、连续分布、"O"型连续分布4种不同分布情况下采空区瓦斯运移规律进行数值模拟。当渗透率均匀分布时采空区漏风较少,高浓度瓦斯分布靠近工作面;当渗透率分段均匀分布时,在采空区中有2条跳跃的瓦斯沟壑;当渗透率连续分布时,采空区漏风较多,高浓度瓦斯分布靠近采空区深部;当渗透率"O"型连续分布时,采空区漏风最多。结果表明,当渗透率不同分布情况下采空区漏风和瓦斯分布有很大差别。因此,为了得到更符合现场实际情况的瓦斯运移规律,在模拟采空区瓦斯运移规律时需要描述更能如实反映采空区煤岩冒落规律的渗透率分布。     

低渗透非达西流场中的一维溶质运移模拟

为了准确地研究低渗介质中地下水污染问题,在充分考虑地下水在低渗介质中渗流时存在启动压力梯度和动边界的基础上,建立了低渗介质中地下水污染和地下水渗流的耦合数学模型。采用有限差分法和混合有限分析法对耦合模型进行数值求解,并分析了启动压力梯度对地下水污染浓度的影响。结果表明启动压力梯度对地下水污染浓度的分布有着重要的影响,在研究低渗介质中的污染问题时不容忽视。     

Flow and transport in fractured tuff at Yucca Mountain: numerical experiments on fast preferential flow mechanisms

Recent discovery of bomb-related ³⁶Cl at depth in fractured tuff in the unsaturated zone at the Yucca Mountain candidate high-level waste (HLW) repository site has called into question the usual modeling assumptions based on the equivalent continuum model (ECM). A dual continuum model (DCM) for simulating transient flow and transport at Yucca Mountain is developed. In order to ensure properly converged flow solutions, which are used in the transport simulation, a new flow solution convergence criteria is derived. An extensive series of simulation studies is presented which indicates that rapid movement of solute through the fractures will not occur unless there are intense episodic infiltration events. Movement of solute in the environs of the repository is enhanced if the properties of the tuff layer at the repository horizon are modified from current best-estimate values. Due to a large advective–dispersive coupling between the matrix and fractures, the matrix acts as a major buffer which inhibits rapid transport along the fractures. Consequently, fast movement of solutes through the fractures to the repository depth can only be explained if the matrix–fracture coupling term is significantly reduced from a value that would be calculated on the basis of data currently available.     

烟气连续监测系统的相对准确度检测

阐述了HJ／T76—2001《固定污染源排放烟气连续监测系统技术要求及检测方法》标准中烟气连续监测系统的相对准确度计算和相对准确度计算中存在的问题。对存在问题中的重复性或复现性的假设、B类不确定度的忽略、标准分析方法平均值的采用和偏差检验进行了探讨。     

塑性混凝土渗透及渗透变形试验模型与指标测定

介绍了为堤防防渗工程设计的塑性混凝土渗透系数及渗透破坏比降试验模型及其测定方法。     

SUBSURFACE DISTRIBUTION OF NITRATES BELOW COMMERCIAL CATTLE FEEDLOTS,TEXAS HIGH PLAINS1

ABSTRACT. Samples for water-quality analyses were collected from beneath eighty commercial cattle feedlots in the Texas High Plains. Twenty-two feedlots were drilled and/or cored to establish vertical gradients of dissolved solids. Sample and gamma logs, size analyses and vertical permeability of cores were determined from samples beneath these lots. Relationships of groundwater saturated thickness, depth to watertable, and age of lots to specificion distribution were evaluated. The study includes lots ranging in age from 35 years to new installations. Runoff collection-systems on lots include playas, man-made ponds, and dammed and undammed stream channels. Infiltration of feedlot liquid waste to the watertable below feedyards is insignificant in most localities in the Texas High Plains. Infiltration of “collected” feedlot runoff and subsequent concentration of dissolved ions in groundwater in the High Plains are dependent upon, among other things, (1) surface and subsurface geology, (2) depth to water, (3) thickness of the groundwater zone, and to (4) differences in lateral and vertical permeabilities of the Ogallala Formation, the major aquifer. Certainly, no regional subsurface pollution problem exists today nor is one foreseen from cattle feedlot runoff in the Texas High Plains.