基于灰关联分析的顺层钻孔瓦斯抽采有效半径主控因素研究

基于顺层抽采钻孔固气耦合模型,采用COMSOL对钻孔直径、煤层物性参数及抽采参数三类因素进行了模拟分析,并运用灰关联分析方法确定了顺层钻孔瓦斯抽采有效半径的主控因素。研究表明:煤层初始瓦斯压力与煤体初始渗透率为有效半径的主控因素,抽采时间次之,钻孔直径与有效抽采负压的变化对有效半径的影响甚微;提高瓦斯抽采有效半径的首要任务是通过技术手段卸压、增透,其次要把握合理的预抽时间。     

从某正样机的鉴定试验谈可靠性试验设计

介绍了在正样机定型质量控制过程中,强化鉴定试验可靠性设计方法研究。从编制鉴定试验大纲、方案评审、试验程序控制、试验数据分析、试验过程组织和技术能力提高等关键环节入手。确定正样机置信水平,得出正样机功能及主要性能满足战术技术指标要求。     

环境影响后评价工作内容研究——以码头建设项目后评价为例

《中华人民共和国环境影响评价法》是建设项目环境影响后评价的法律依据,中国环境影响后评价的起步较晚,相关制度正在完善,对于开展后评价的对象及评价内容,以及后评价相适应的技术方法,还需要根据不同情形进行深入探讨.通过探讨环境影响后评价的适用对象、适用情形、主要工作内容,并以某码头建设项目环境影响后评价为例,介绍了环境影响后评价的主要工作内容,希望为环境影响后评价工作的规范提供借鉴.     

Empirical Estimation of Stream Discharge Using Channel Geometry in Low‐Gradient,Sand‐Bed Streams of the Southeastern Plains

Manning's equation is used widely to predict stream discharge (Q) from hydraulic variables when logistics constrain empirical measurements of in‐bank flow events. Uncertainty in Manning's roughness (n_M) is the major source of error in natural channels, and sand‐bed streams pose difficulties because flow resistance is affected by flow‐dependent bed configuration. Our study was designed to develop and validate models for estimating Q from channel geometry easily derived from cross‐sectional surveys and available GIS data. A database was compiled consisting of 484 Q measurements from 75 sand‐bed streams in Alabama, Georgia, South Carolina, North Carolina (Southeastern Plains), and Florida (Southern Coastal Plain), with six New Zealand streams included to develop statistical models to predict Q from hydraulic variables. Model error characteristics were estimated with leave‐one‐site‐out jackknifing. Independent data of 317 Q measurements from 55 Southeastern Plains streams indicated the model (Q = A_cR_H^0.6906S^0.1216; where A_c is the channel area, R_H is the hydraulic radius, and S is the bed slope) best predicted Q, based on Akaike's information criterion and root mean square error. Models also were developed from smaller Q range subsets to explore if subsets increased predictive ability, but error fit statistics suggested that these were not reasonable alternatives to the above equation. Thus, we recommend the above equation for predicting in‐bank Q of unbraided, sandy streams of the Southeastern Plains.     

双线盾构隧道斜交下穿既有机场高速公路的地表沉降预测模型研究*

为指导隧道盾构下穿既有建构筑物施工的变形控制,考虑隧道收敛模式和复合地层主要影响角的影响,以双线圆形盾构隧道斜交下穿既有机场高速公路为例,构建圆形隧道地层主要影响角计算方法,改进传统Peck公式,分析盾构斜交角、盾构坡角和隆起偏角的共同影响,引入地层损失率几何修正系数,并利用叠加原理建立双线盾构隧道斜交下穿既有机场高速公路的地表沉降预测模型,依托实际工程对预测模型的工程适用性进行验证。研究结果表明:本文预测模型的整体精度相比Suwansawat等预测模型提升44.15％,可预测施工影响范围内任意点的地表沉降值,相比现有模型更适用于解决双线盾构隧道斜交下穿施工的地表沉降预测问题,可为类似工程中的地表沉降变形预测及控制提供指导。     

近20年来淮北市植被变化遥感动态监测与分析

通过遥感技术对淮北市主城区(相山建成区)18年间植被变化进行统计分析,从而得出结论,并对所得结果进行了分析。     

Distribution and ratios of Cs and K in control and K-treated coconut trees at Bikini Island where nuclear test fallout occurred: effects and implications

Coconut trees growing on atolls of the Bikini Islands are on the margin of K deficiency because the concentration of exchangeable K in coral soil is very low, ranging from only 20 to 80 mg kg⁻¹. When provided with additional K, coconut trees absorb large quantities of K and this uptake of K significantly alters the patterns of distribution of ¹³⁷Cs within the plant. Following a single K fertilization event, mean total K in trunks of K-treated trees is 5.6 times greater than in trunks of control trees. In contrast, ¹³⁷Cs concentration in trunks of K-treated and control trees is statistically the same while ¹³⁷Cs is significantly lower in edible fruits of K-treated trees. Within one year after fertilization (one rainy season), K concentration in soil is back to naturally low concentrations. However, the tissue concentrations of K in treated trees stays very high internally in the trees for years while ¹³⁷Cs concentration in treated trees remains very low in all tree compartments except for the trunk. Potassium fertilization did not change soil Cs availability.     

Bankfull Regional Curves for North and Northwest Florida Streams1

Abstract: Regional curves, which relate bankfull channel dimensions and discharge to watershed drainage area, are developed to aid in identifying the bankfull stage in ungaged watersheds, and estimating the bankfull discharge and dimensions for river studies and natural channel design applications. This study assessed 26 stable stream reaches in two hydro‐physiographic regions of the Florida Coastal Plain: the Northwest Florida Coastal Plain (NWFCP) and the North Florida Coastal Plain (NFCP). Data from stream reaches in Georgia and Alabama were also used to develop the Florida regional curves, since they are located in the same hydro‐physiographic region. Reaches were selected based on the presence of U.S. Geological Survey gage stations and indicators of limited watershed development (e.g., <10% impervious surface). Analyses were conducted to determine bankfull channel dimensions, bankfull discharge, average channel slope, and Rosgen stream classification. Based on these data, significant relationships were found between bankfull cross‐sectional area, width, mean depth, and discharge as a function of drainage area for both regions. Data from this study suggested that bankfull discharges and channel dimensions were larger from NWFCP streams than from Coastal Plain streams in North Carolina and Maryland. Bankfull discharges were similar between NFCP and Georgia coastal plain streams; therefore, the data were combined into one regional curve. In addition, the data were stratified by Rosgen stream type. This stratification strengthened the relationships of bankfull width and mean depth as a function of drainage area.     

交通运输航道噪声的预测方法及其防治措施

交通运输航道产生的噪声是航道两岸声环境污染的重要来源.随着人们环境保护意识的增强,对交通运输航道噪声的影响评价及防治越来越受到重视.结合环境评价实例,提出了交通运输航道噪声预测评价方法,并给出了一些防治措施.     

预混乙炔-空气爆燃火焰在平板狭缝中传播与熄灭的实验研究

通过对预混乙炔-空气爆燃火焰在平板狭缝中的传播与熄灭过程进行试验研究,分析临界火焰传播速度、狭缝高度和熄灭长度之间的关系。实验结果表明,当狭缝高度一定时,临界火焰传播速度越大,熄灭长度越大,熄灭长度与临界火焰传播速度近似呈正比例关系。在相同的临界火焰传播速度条件下,随着狭缝高度的增加,熄灭长度值迅速增大,说明狭缝高度对预混火焰的传播与熄灭有显著影响。