黔中地区不同林龄马尾松小气候特征研究

以黔中地区不同林龄马尾松人工林为研究对象,采用时空替代法,选取农田（对照）、林窗、中林龄、近熟林、成熟林和过熟林6个样地,每月选择代表日分时段测量光照强度、光通量密度、气温、相对湿度、蒸气压亏损和风速等小气候指标,同时对样地内不同垂直高度（0.5,1.0和1.5m）观测指标进行比较.结果表明：（1）除风速随测量高度变化（1.5m > 1.0m > 0.5m）差异极显著外（P<0.01）,其余观测指标随测量高度均无显著差异（P>0.05）.（2）观测时段内,不同林龄马尾松林小气候均存在显著性差异（P<0.05）,其中光照强度、光通量密度、气温、蒸气压亏损和风速变化为农田 > 林窗 > 马尾松林;相对湿度变化为马尾松林 > 林窗 > 农田.（3）与农田相比,马尾松林分别降低了光照强度、光通量密度、气温、蒸气压亏损和风速的917.36%、837.35%、5.33%、30.77%、193.58%,增加了6.39%的相对湿度,具有显著的遮阳降温、增湿保湿、维持林冠下小气候稳定的作用.在演替前期,抵挡阳光和风速的效果明显,而在后期,降温增湿以及保湿效果显著.舒适度评价显示,除冬季外,黔中地区马尾松林可发挥良好的森林康养和游憩生态功能.     

Effect of current density on groundwater arsenite removal performance using air cathode electrocoagulation

• With the same charge, current density had little effect on As(III) removal in ACEC. • ACEC had the lowest energy consumption compared with EC/O₂ or EC/N₂. • There was a trade-off relationship between energy consumption and removal time. • The ·OH concentration in ACEC was 1.5 times of that in the EC/O₂ system. Naturally occurring arsenic enrichment in groundwater poses a huge threat to human health. Air cathode electrocoagulation (ACEC) has recently been proposed to enhance As(III) oxidation and lower energy consumption. In this study, ACEC, EC/O₂ and EC/N₂ were evaluated with different current densities from 1 to 8 mA/cm² to investigate the effect on As(III) removal in different redox environments. Current density had no appreciable effect on arsenic removal efficiency given the same charge in ACEC because the concentration ratio of Fe/H₂O₂ under different current densities remained stable. However, in EC/O₂ and EC/N₂, As(III) removal was inhibited at higher current densities (4–8 mA/cm²), likely because more Fe(II) competed with As(III) for the oxidant, leading to less effective oxidation of As(III). In all EC systems, the ·OH units generated per power consumption reached the highest value at the lowest current density. Compared with other EC systems, the ACEC system showed lower energy consumption at all current densities due to the low energy consumption of the electrode reaction and more free radical generation. A lower current density saved more energy at the expense of time, showing the trade-off relationship between energy consumption and removal time. The operation costs for As(III) removal under optimal conditions were calculated as 0.028 $/m³ for ACEC, 0.030 $/m³ for EC/O₂, and 0.085 $/m³ for EC/N₂     

粉尘云浓度对HDPE粉尘云最低着火温度的影响

为准确评价高密度聚乙烯（HDPE）粉尘爆炸敏感性和开展有效的粉尘防爆工作,采用Godbert-Greenwald恒温炉标准实验装置研究了典型HDPE粉尘云最低着火温度的分布特性,着重探讨了粉尘云浓度对不同喷尘压力条件下HDPE粉尘云最低着火温度的影响规律。研究表明:测试条件下HDPE粉尘云最低着火温度的变化处于360~445 ℃范围,随粉尘云浓度的增加呈现先降低后升高的总体趋势,粉尘云浓度为1.111 kg/m3时出现拐点,且粉尘云最低着火温度随喷尘压力的增加而降低。     

基于有限元法的工字形结构安全优化设计

为了提高工字形结构安全力学性能,采用设计软件建立结构优化模型,通过软件Workbench进行拓扑优化辅助设计.主要对工字形结构在静载作用下开展拓扑优化设计,以质量减少百分比、最大应力、最大形变为约束条件,结构材料密度为可变参数量,结构最小体积密度设为目标函数,得出拓扑优化理想模型,为运用拓扑技术对结构安全应用领域优化提...     

染色法——一种改进的丛枝菌根孢子密度快速测定方法

菌根是目前应用于煤矿区生态治理的一种新技术,菌根孢子密度是衡量菌根生态适应性的标准之一。采用改进的曲利本兰染色方法,对孢子密度测定方法作了改进,以提高测定的精度和速度。结果表明：经染色后的基质中孢子及其菌丝呈紫色,在双目显微镜下观测孢子的数量和形态很容易识别,计数的精度和速度明显提高,降低了孢子密度测定过程中的人为误差。为检验菌根技术在野外大规模的生态应用效果提供了一种快速测定方法。     

近地面NO_2浓度卫星遥感估算问题

对卫星遥感监测大气NO_2的差分算法涉及的科学问题进行了综述,包括去除大气散射和地表反射噪声影响、大气拉曼散射引起的Ring效应校正、不同大气成分分离和观测垂直归一化等问题。国际上通过剔除平流层NO_2获得对流层柱浓度产品,文章绕开平流层NO_2获取问题,提出了结合大气化学模式模拟的垂直廓线直接估算近地面NO_2浓度技术方法,以更好地满足环境空气质量的观测需求,阐述了几个影响NO_2反演精度的相关问题。     

基于AVMD与DPC-FCM的旋转机械无监督故障诊断方法

目的 针对旋转机械故障诊断过程中存在故障信号特征提取困难、故障诊断过程有标签数据较少、故障诊断准确率低等问题,提出自适应变分模态分解算法(Adaptive Variational Mode Decomposition, AVMD)与密度峰值算法优化的模糊C均值算法(Clustering by Fast Search and Find of Density Peaks Optimizing Fuzzy C-Means,DPC-FCM)结合的无监督诊断方法。方法 首先,将多尺度排列熵与峭度相结合的综合系数作为适应度函数,对VMD算法的惩罚因子alpha和模态个数K进行参数寻优,提取分解后本征模态函数(Intrinsic Mode Function,IMF)的平均样本熵与平均模糊熵,并输入至聚类算法中。其次,提出利用密度峰值聚类算法确定FCM的初始聚类中心,降低聚类结果的随机性。结果 将提出的无监督故障诊断模型应用到滚动轴承试验信号中,实现了准确的故障诊断。结论 AVMD在故障提取方面具有优越性,同时DPC算法可以有效提高FCM算法无监督聚类的准确性,二者结合可以有效实现旋转机械故障的智能分类。     

细水雾抑制固体燃料火焰辐射特性的研究

采用热电偶测温系统和热流辐射传感器等仪器对细水雾施加前后火场温度及辐射热流密度进行测量.研究了不同喷雾气压下固体燃烧场的温度及辐射热流密度的变化特性.结果表明,细水雾的蒸发冷却是影响火焰热辐射的一个重要因素.在实验基础上,建立了固体可燃物燃烧场辐射热流密度的计算模型,计算结果与实验结果较为吻合.     

Water Quality in Drinking Water Reservoirs of a Megacity, Istanbul

Providing clean water at relevant quality and quantity is a challenge that regulatory authorities have to face in metropolitan cities that seem to develop at their limits of sustainability. Istanbul strives to face such a challenge for its population of over 10 million, through six surface water resources. Two approaches of classification for the reservoirs are presented, one based on current regulations and an alternative based on a more detailed classification. The results have shown that nutrient control is the primary issue, and one of the reservoirs has already exceeded the limits of being eutrophic, one is at mesotrophic conditions, and the remaining four are at the limit of being eutrophic, indicating the significance of making the correct decision and taking pertinent measures for management and control. It has been observed that the only mesotrophic resource, which also has the best general quality class, has no industry and a very low population density, whereas the one that is already eutrophic is also the one with the lowest quality class, has the highest population density, and has the greatest percentage of urban land use within its watershed.     

利用硝化细菌对煤矿固体废物生态毒性的检测

主要研究了在水或不同酸性条件下，徐州某矿矸石和煤泥可提取成份对硝化细菌硝化作用强度的影响。结果表明，矸石和煤泥在不同酸性条件下的可提取成份对硝化作用强度均产生不同程度的抑制作用，提示本方法在反映煤矿固体废物生态毒性方面有一定检测作用。