Air and water flows induced by pumping tests in unconfined aquifers with low‐permeability zones

Air flows from the atmosphere into an unconfined aquifer when the water table falls during pumping tests. Pumping test results in unconfined aquifers may be significantly affected by low‐permeability zones (LPZs) near the initial water table position, because they restrict the downward movement of air. A transient, three‐dimensional air–water two‐phase flow model is employed to investigate numerically the effects of local heterogeneity on pumping test results in unconfined aquifers. Two cases of local heterogeneities are considered herein: a LPZ around the pumping well and on one side of the pumping well. Results show that the drawdown with the LPZ is significantly greater than that of the homogeneous aquifer. The differences in drawdown are the most significant at intermediate times and gradually diminish at later times. The LPZ significantly reduces air flow from the atmosphere to the aquifer. The pore air velocity in the LPZ is very low. The air pressure at the observation point under the LPZ when air begins to enter is significantly lower than the air pressure of the homogeneous aquifer at the same point. After that, the air pressure increases quickly and then increases slowly. The time for the air pressure to reach the atmospheric pressure is significantly longer. Copyright © 2013 John Wiley & Sons, Ltd.     

Seasonal dynamics of soil CO2 effluxes with responses to environmental factors in lower subtropical forests of China

Seasonal metrics and environmental responses to forestry soil surface CO₂ emission effluxes among three types of lower subtropical forests were consistently monitored over two years with static chamber-gas chromatograph techniques among three types of lower subtropical forests. Results showed that annual CO₂ effluxes (S+L) reached 3942.20, 3422.36 and 2163.02 CO₂ g·m⁻²·a⁻¹, respectively in the monsoon evergreen broadleaf forest, mixed broadleaf-coniferous forest and coniferous forest. All the three types of forests revealed the same characteristics of seasonal changes with the CO₂ effluxes peaking throughout June to August. During this peaking period, the effluxes were 35.9%, 38.1% and 40.2% of the total annual effluxes, respectively. The CO₂ emission process responding to the environmental factors displayed significantly different patterns in forestry soils of the three types of forests. The coniferous forest (CF) was more sensitive to temperature than the other two types. The Q ₁₀ values were higher, along with greater seasonal variations of the CO₂ efflux, indicating that the structurally unique forestry ecosystem has disadvantage against interferences. All the three types of forestry CO₂ effluxes showed significant correlation with the soil temperature (T _s), soil water content (M _s) and air pressure (P _a). However, stepwise regression analysis indicated no significant correlation between air pressure and the soil CO₂ efflux. With an empirical model to measure soil temperature and water content in 5 cm beneath the soil surface, the CO₂ effluxes accounting for 75.7%, 77.8% and 86.5% of the efflux variability respectively in soils of BF, MF and PF were calculated. This model can be better used to evaluate the CO₂ emission of soils under water stress and arid or semi-arid conditions.

     

牙鲆选育F3代家系的建立及遗传效应分析

牙鲆是太平洋西岸海水养殖、捕捞和自然增殖的主要鱼类,但是人工养殖病害多、生长慢,针对这一问题,从2003年开始开展了牙鲆选择育种。本文利用筛选和培育的F1、F2代牙鲆家系核心群体,构建了F3代家系52个,在生长到196d时,对家系1 560尾鱼苗全长、体宽、体质量、全长日增量和体重日增量5个生长性状进行测量和计算,获得7 800个数据。采用"加性-显性"线性模型、最小范数二阶无偏估计法(MINQUE)对以上生长性状的边际平均值、加性方差分量、显性方差分量、随机方差分量、狭义遗传力、广义遗传力、亲本加性效应、杂交随机效应等遗传参数进行了评估。结果显示:1202、1206、1226和1211家系以上生长性状的边际平均值同时显著高于其他家系。以上5个生长性状的加性方差分量比率为(0.099±0.01)~(0.24±0.02),显性方差分量比率(0.30±0.02)~(0.31±0.02),随机方差分量比率(0.48±0.02)~(0.61±0.01),5个性状狭义遗传力0.099~0.24,广义遗传力0.38~0.54,以上遗传参数均达极显著性水平(P0.01)。综合比较18个亲本5个性状的加性效应预测值,发现F0917、F0908、F0905、F0915、F09125和KS(韩国牙鲆)亲本在5个性状上都具有极显著的正向效应(P0.01),其他亲本5个性状都不同程度的表现为显著(P0.05)或极显著(P0.01)的负向加性效应。对42个杂交组合显性随机效应进行预测,D(2×6)、D(2×18)、D(3×4)、D(7×12)、D(7×14)和D(8×13)6个杂交组合在5个性状上都表现为极显著(P0.05)正效应,利用这些杂交组合建立家系将促进牙鲆以上5个性状的生长。本文研究结果,为牙鲆优良家系的建立及新品种的培育初步筛选出了性状优良的亲本、杂交组合和家系,同时为牙鲆进一步选择育种提供了理论和技术依据。     

泥石流冲击作用下框架结构的破坏机理

推导了泥石流冲击力作用下结构的最大位移,可以看出最大位移与泥石流的密度、速度,结构的周期、刚度有关。通过对泥石流冲击力的简化,利用有限元软件模拟二层框架结构在泥石流冲击作用下的响应,得到了底层框架柱的位移时程曲线,并对底层柱破坏形态进行了分析。把结构理论最大位移与模拟最大位移进行比较,得到了结构最大位移限值,为建筑物抵抗泥石流冲击设计提供了参考。     

黄淮地区汛期降水预测的一种前兆信号

为探讨黄淮地区汛期降水预测的物理因子,应用奇异值分解(SVD)技术研究了冬季北太平洋地区上空100hPa高度场与黄淮地区汛期降水场的时空结构及相互关系。结果表明其SVD分解的第一模态有较高的相关,一般1月份40~60°N,160°E~160°W的北太平洋地区上空100hPa高度场偏低(高)时,则黄淮地区汛期降水偏少(偏多),可作为预测黄淮地区汛期降水的一种前兆信号。     

浅谈IE浏览器在办公自动化中的应用

为了能够充分利用山西省临汾市气象通信网络系统,市局要求各县(市)局的气象信息要通过网络进行传递,这样加快了文件的传递速度,提高了我们的工作效率。而Windows98中所带的ETP工具虽然实用,但由于它的命令比较繁琐,不容易掌握。市局为了能加快传报速度,开发了一套传报系统,非常实用,但局限性较大,只能用于地面观测发报所用。     

基于ANSYS的采动围岩视电阻率动态变化模拟

以煤层开采引起的顶底板岩层变形破坏理论及岩、矿石导电性的影响因素为理论依据,在顶底板岩层破坏分布范围的基础上,可以将煤层顶底板分别划分为若干个电性区段并建立地电模型。利用ANSYS软件进行有限元分析,通过视电阻率等值线图总结分析煤层开采引起的视电阻率变化规律,对视电阻率的变化状况进行分析,可以解决一系列的矿井地质问题,从而能够指导煤矿安全高效的生产。     

南亚热带森林植被恢复演替中土壤有机碳组分及其稳定性

以鼎湖山森林植被恢复演替过程中的松林(初期)、混交林(中期)和季风林(后期)为研究对象,通过测定其土壤总有机碳(TOC)、易氧化有机碳(ROC)和不易氧化有机碳(NROC)及凋落物13C-NMR分析,以期阐明森林植被恢复演替过程中土壤有机碳组分变化规律及其原因。结果表明:(1)3个森林土壤ROC含量差异不显著;由松林向季风林演替过程中,ROC占TOC的比例下降。松林新鲜凋落物层的烷氧基碳含量(57.03%)高于季风林(49.10%)和混交林(54.50%)。(2)3个森林土壤NROC含量差异显著,大小顺序为:季风林混交林松林。混交林和季风林凋落物半分解层和已分解层的惰性指数明显高于松林。TOC趋势与NROC一致。南亚热带森林由松林向季风林恢复演替过程中,土壤有机碳的稳定性增加,惰性有机碳的持续积累可能是季风林和混交林土壤TOC积累的一个重要过程。     

山东省稀有金属矿产资源特征及找矿方向浅析

稀有金属在现代高新技术和国防建设中具有重要用途,属于国家战略性矿产。山东省已发现多个稀有金属矿床（点）,主要分布在威海、青岛、泰安、枣庄等地区。山东省内稀有金属矿床按其成因主要分为滨海沉积型、花岗伟晶岩型以及滨海澙湖沉积型3种稀有金属矿床。本文总结了山东省稀有金属矿产勘查及开发利用现状和供需形势,论述了3种成因类型典型稀有矿床的地质特征,划分了找矿远景区并提出了相应工作手段,为今后稀有金属矿产勘查提供参考。