2000—2016年珠海市酸雨变化特征及酸雨概念模型

为评估我国酸雨控制效果与发展趋势,利用2000-2016年东亚酸沉降监测网（EANET）的监测数据及同步气象资料,研究了珠海市酸雨变化特征及EANET中国网所有4个城市（珠海、厦门、重庆、西安）的城市降水化学组分特征.利用HYSPLIT后向轨迹聚类和潜在源区PSCF分析方法,研究了珠海市降水气团和酸雨来源,建立了珠海市酸雨概念模型.结果表明：①珠海市酸雨日数与频率呈先增后减趋势,2008年后珠海市酸雨污染程度明显改善,我国酸雨控制效果明显.②沿海城市（珠海、厦门）与内陆工业城市（重庆、西安）降水离子组分区别明显,内陆工业城市酸雨受碱性颗粒物影响较大.③沿海城市（珠海、厦门）酸雨为硫酸-硝酸混合型;内陆工业城市（重庆、西安）酸雨以硫酸型为主,近年有向硫酸-硝酸混合型转变的趋势.④综合酸雨降水HYSPLIT后向轨迹聚类分析与PSCF潜在源区分析结果可建立酸雨概念模型,有助解释酸雨成因.珠海市强酸雨主要受珠海市外的珠三角地区污染物输送影响.     

河北省涞水县大气颗粒物单颗粒分析表征及来源识别

为了解河北省涞水县颗粒物污染特征,采用单颗粒分析技术扫描电镜-X射线能谱法和气团后向轨迹分析技术对该县2015年3个典型污染时段〔即正常管控、严格管控（2015年阅兵期间）及发生严重颗粒物染污〕采集的7个大气颗粒物样品进行了分析表征和来源解析.共测量了1 506个粒径≥0.5 μm的单颗粒,其中粒径小于2.5 μm的颗粒占98%以上,测量结果揭示了细颗粒污染特征.结果表明:①碳质颗粒为主要颗粒物种类,其检出数目占比在90%以上.②非供暖期严格管控时段,当地居民日常生活产生的球形碳质颗粒检出数目占比最高.③非供暖期正常管控时段,机动车排放的碳质集合体颗粒检出数目占比最高,交通污染贡献最大.④供暖期球形碳质颗粒检出数目占比最高,含硫颗粒检出数目占比相对增加,燃煤的贡献最大.3个采样时段48 h气团后向轨迹分析结果表明,在空气质量良好、颗粒物污染水平较低的情况下,影响研究区域空气质量的主要是本地源;雾霾天气（处于严重颗粒物污染时段）时,西南方向外来源和本地源共同构成研究区域的颗粒物污染状态.      

基于PCA-BP神经网络的多股铜导线 熔痕定量金相识别方法研究

为实现火灾现场中多股铜导线熔痕的自动识别,采用主成分分析(PCA)和反向传播(BP)神经网络算法对四种多股铜导线熔痕(一次短路熔痕、二次短路熔痕、过负荷熔痕和火烧熔痕)的金相组织进行了识别研究。利用Image-Pro Plus 6.0和Axio-Imaging软件获取每种熔痕30组17维金相组织参数数据,采用PCA对四种熔痕共120组数据降维,获得前6个主成分得分矩阵,建立具有6个输入层节点,10个隐层节点和4个输出节点的神经网络模式识别模型。随机抽取每种熔痕的20组样品的主成分得分矩阵作为训练集,将每种熔痕的剩余10组主成分得分为测试数据,输入最终训练完成的模型进行识别,其识别准确率达到92.5%。实验结果表明采用PCA+BP神经网络的算法,可以较好地实现多股铜导线熔痕识别,为火灾物证鉴定工作提供了有力的工具。     

基于卫星遥感的海南地区对流层NO2长期变化及成因分析

利用OMI卫星反演的较高分辨率(0.125°×0.125°)对流层NO_2(Tro NO_2)柱浓度数据,分析了近12年海南岛TroNO_2柱浓度的时空变化,同时,结合MODIS卫星反演的气溶胶光学厚度(AOD)资料、海口市空气质量指数(AQI)、GDP、SO_2排放总量,以及民用汽车保有量等探究其长期变化与成因.结果表明:海南地区TroNO_2柱浓度空间分布表现为北半部高于南半部、四周沿海高于中部山区的特征,其中,北部地区最大值可达20×1014molec·cm~(-2)以上.近12年来海南地区TroNO_2柱浓度表现为上升的变化趋势.季节变化表现为冬季高于夏季,夏季浓度偏低和雨水的冲刷作用有关,而冬季偏高与旅游过冬人口增多和外源输送作用有密切联系.四季TroNO_2柱浓度均有不同程度的上升,而且季节差异在2010年以后有增大的趋势.海南地区TroNO_2柱浓度分布与岛上经济水平和人口分布关系密切,海南地区民用机动车拥有量近10年呈现快速的增加趋势,机动车尾气NO_2排放也不容忽视.     

Morphology-Related Isometric Trunk Strength of South African Manual Workers: Implications for Prevention of Occupational Low-Back Stress

Occupational back stress among manual workers in South Africa is now a cause of governmental concern. Yet no data on the back strength of the South African workforce have been published. This study represents a first step in reporting the trunk strength of Xhosa workers in South Africa, in absolute and size-relative terms. Thirty-five male manual workers were tested isometrically while making maximal extension and flexion efforts at 0°, 23°, 46°, 69°, and 92° of stoop. The results show nonlinearity of the extensor-to-flexor (E/F) ratio of the trunk musculature. The E/F ratio increases in deep stoop because of a drop in flexor torques. The data suggest that predictions of flexor from extensor torques or vice versa can confidently be made so long as testing is done away from the fully flexed position. Significant differences between morphologically gracile and robust workers in this sample are discussed. The study has implications for occupational rehabilitation and for prophylaxis, for whereas muscular strength alone may not protect the spine from occupational injury, muscular weakness certainly predisposes it.     

基于颗粒流数值方法的岩石压剪破坏细观特征研究

压剪破坏是影响岩体工程安全的主要因素,基于颗粒流程序的伺服控制原理,采用等效晶质模型模拟了粉砂质板岩的压剪破坏过程,通过与室内试验对比验证了其适用性,并从细观角度揭示了岩石在压剪过程中的破坏机理。结果表明:裂纹增长速率与试件压剪过程中经历的弹性、塑性和破坏3个阶段具有相关性;张拉、剪切裂纹呈同步增长趋势,但峰后张拉裂纹增长速率快于剪切裂纹,即试件峰后以张拉破坏为主;随剪切角增大,由沿晶和穿晶断裂向以沿晶断裂为主转变,裂纹数量减小且扩展方向向断裂面集中;穿晶断裂的扩展更容易导致局部失稳,即在宏观上表现为塑性阶段;穿晶裂纹主要沿断裂面扩展、贯通,一定程度上可以抑制断裂面附近较大破裂块体的产生。     

单轴压缩下中部锁固岩桥变形破坏模式及演化机制研究

为了探究锁固岩桥破坏模式及演化机制，通过在完整试样端部预制裂隙以形成中部岩桥，采用物理试验和RFPA2D数值模拟方法，研究不同锁固岩桥角度试样破坏模式及裂隙扩展演化机制的影响规律，并利用断裂力学理论分析岩桥裂隙扩展机理。研究结果表明:利用数字图像技术，从定量角度分析裂隙扩展类型，得出试验试样最终破坏是由前期损伤不断积累所导致的结果；锁固段岩桥角度α对锁固段的破坏有重要影响，当α≤90°时，锁固岩桥段发生张拉贯通破坏；当90°＜α＜120°时，锁固岩桥段发生张拉剪切贯通破坏；当α≥120°时，锁固岩桥段并没有发生贯通破坏。最终得出3种试样破坏模式:下部裂隙张拉扩展，贯通中部岩桥；上下部裂隙同时张拉扩展，剪切贯通中部岩桥；下部裂隙张拉扩展，贯通试样上端面，中部岩桥没有发生破坏。     

Consequence prediction for dust explosions involving interconnected vessels using computational fluid dynamics modeling

Combustible dust explosions continue to present a significant threat toward operating personnel and pneumatic conveyance equipment in a wide variety of processing industries. Following ignition of suspended fuel within a primary enclosure volume, propagation of flame and pressure fronts toward upstream or downstream interconnected enclosures can result in devastating secondary explosions if not impeded through an appropriate isolation mechanism. In such occurrences, an accelerated flame front may result in flame jet ignition within the secondary vessel, greatly increasing the overall explosion severity. Unlike an isolated deflagration event with quantifiable reduced pressures (vent sizing according to NFPA 68 guidance), oscillation of pressure between primary and secondary process vessels leads to uncertain overpressure effects. Dependent on details of the application such as relative enclosure volumes, relief area, fuel type, suspended concentration, duct size, and duct length, the maximum system pressure in both interconnected vessels can be unpredictable. This study proposes the use of FLame ACceleration Simulator (FLACS) computational fluid dynamics (CFD) modeling to provide reliable consequence predictions for specific case scenarios of dust deflagrations involving interconnected equipment. Required minimum supplement to the originally calculated relief area (A_v) was determined through iterative simulation, allowing for reduced explosion pressures (P_red) to be maintained below theoretical enclosure design strengths (P_es).     

Suppression of flame propagation in a long duct by inertia isolation with inert gases

Experimental studies were done with a small pipe with a diameter of 0.043 m and a large pipe with a diameter of 0.49 m to demonstrate the flame propagation suppression with inertia isolation in a long duct. Tests were carried in an ignition section containing propylene/air mixture near stoichiometric concentration and generating a peak flame propagation speed of approximately 100 m/s. The ignition section is connected to a section filled with an inert gas, another section with flammable mixtures, and finally a sufficiently long, ambient section to accommodate flame propagation. The critical length of the inert gas section required for successful suppression of flame from the igniting the flammable section is found to be 0.6 m for CO₂ and 0.9 m for N₂ in the large pipe and 0.2 m for CO₂ and 0.3 m for N₂ in the small pipe. Additional tests with a 3 m of ignition section and peak flame propagation speed of 225 m/s showed that the critical length for successful suppression by CO₂ is only increased slightly to 0.9 m, confirming that the suppression is a result of inertia isolation rather than inert gas dilution. Finally, application of the results in responding to large-scale leak into a long, underground duct is discussed.     

基于人工神经网络的夜光藻密度预测模型

利用人工神经网络 BP算法 ,对各种理化因子与赤潮中夜光藻密度建立了人工神经网络预报模型 ,并利用该模型对各种理化因子与夜光藻密度的非线性对应规律进行了研究。结果表明 ,模型较好地反映了存在的对应规律