复合体系有机气体氧化生成二次有机气溶胶研究进展          下载免费PDF全文

陈晓文  李坤  李建龙  杜林 《大气科学学报》2023,46(5):641-654

生物源与人为源有机气体氧化形成的二次有机气溶胶(SOA)对气候变化和人类健康具有重要影响。SOA的产生与其前体物研究已取得了一些进展,但由于有机气体之间存在复合相互作用以及SOA形成机制复杂,目前对不同有机气体混合体系中SOA的形成认知还比较匮乏。因此,深入了解有机气体多源、复杂的相互作用,摸清有机气体的大气氧化机制、SOA的形成及影响等对深入理解真实大气有机气体化学演变具有指导意义。本文旨在了解复合体系有机气体氧化生成SOA的相关研究进展。一方面总结了复合体系有机气体产生SOA质量浓度、产率、成分、挥发性、光学性质等的变化,侧重于实验室复合体系有机气体氧化对SOA形成的多重影响以及SOA组成元素、分子构成的变化特征,并总结了目前实验室基于模型对复合体系SOA生成的模拟研究和拟合情况;另一方面探究了环境因素,如相对湿度(RH)、温度(T)以及无机气体,如氮氧化物(NO_x)、二氧化硫(SO₂)、氨气(NH₃)等对复合体系有机气体形成SOA的影响。  相似文献   

2007 年长江口邻近海域夏季上升流演变机制研究   总被引：3，自引：0，他引：3  

曹公平  宋金宝  樊伟 《海洋科学》2013,37(1):102-112

研究长江口邻近海域夏季上升流强度和空间分布的变化,对渔业生产和赤潮的防治具有重要的指导意义.采用2007年6~10月高分辨率卫星遥感资料 NGSST 海表温度和 CCMP 风场,通过经验正交函数(EOF)分解和区域海洋数值模式(ROMS)研究了该海域夏季上升流的短期演变机制及其与 SST 异常的关系.结果表明,夏季上升流强度和范围存在明显变化,是引起该海域 SST 异常的重要原因;风场对上升流短期演变起着关键作用,风应力旋度对局地上升流变化的影响与沿岸风应力同等重要;地形变化影响着上升流中心的分布,陡而窄的海底凸起容易在顺流侧形成较强的上升流中心,并在逆流侧诱发下降流.  相似文献   

Behavior of soil plugs in open‐ended model piles driven into sands     

Kyu‐Ho Paik  Seung‐Rae Lee 《Marine Georesources & Geotechnology》2013,31(4):353-373

Calibration chamber tests were conducted on open‐ended model piles driven into dried siliceous sands with different soil conditions in order to clarify the effect of soil conditions on load transfer mechanism in the soil plug. The model pile used in the test series was devised so that the bearing capacity of an open‐ended pile could be measured as three components: outside shaft resistance, plug resistance, and tip resistance. Under the assumption that the unit shaft resistance due to pile‐soil plug interaction varies linearly near the pile tip, the plug resistance was estimated. The plug capacity, which was defined as the plug resistance at ultimate condition, is mainly dependent on the ambient lateral pressure and relative density. The length of wedged plug that transfers the load decreases with the decrease of relative density, but it is independent of the ambient pressure and penetration depth. Under several assumptions, the value of earth pressure coefficient in the soil plug can be calculated. It gradually reduces with increase in the longitudinal distance from the pile tip. At the bottom of the soil plug, it tends to decrease with increase in the penetration depth and relative density, and to increase with the increase of ambient pressure. This may be attributed to (1) the decrease of friction angle as a result of increase in the effective vertical stress, (2) the difference in the dilation degree of the soil plug during driving with ambient pressures, and (3) the difference in compaction degree of soil plug during driving with relative densities. Based on the test results, an empirical equation was suggested to compute the earth pressure coefficient to be used in the calculation of plug capacity using one‐dimensional analysis, and it produces proper plug capacities for all soil conditions.  相似文献   

电子探针和LA-ICP-MS技术研究内蒙古浩尧尔忽洞金矿床毒砂矿物学特征     

员媛娇  范成龙  吕喜平  史哲锋  窦智慧  王义天  王梦琦  叶会寿 《岩矿测试》2022,(2):211-225

毒砂的主微量元素组成可以用于判断元素的赋存状态,探讨元素在不同阶段的活化迁移行为.内蒙古浩尧尔忽洞金矿床是产自白云鄂博群黑色岩系中的一个超大型金矿,发育重要载金矿物毒砂和斜方砷铁矿.前人利用传统粉末溶样法对矿石进行同位素分析,探讨了成矿物质来源,但金的迁移富集机制尚未获得解决.为探讨该矿床金迁移富集过程,本文在矿相学的...  相似文献   

压缩气体射流切割破土机理     

张永光  殷琨  王如生  曹丽娜  彭枧明 《吉林大学学报(地球科学版)》2011,41(2):518-522

压缩气体射流切割破土机理既是气力喷射反循环钻孔技术的基础也是其重要的理论依据,而气力喷射反循环钻孔技术又是一项高效环保的软地层钻进技术,所以压缩气体射流切割破土机理研究对于气力喷射反循环钻孔技术有重要意义。首先,应用CFD软件模拟,得出8 mm直径喷孔切割能力为2.868×10³ kPa,与单喷孔地秤实验得到的2.468×10³ kPa拟合较好,其值都远远大于软地层破坏强度;其次,通过LS-DYNA模拟可知单次喷射18 μs时的切割深度约为2.23 mm;最后,用CFD软件分析得到土体微裂隙断裂压力分布图及气体流速图。结果表明,压缩气体射流切割破土机理为：压缩气体沿薄弱环节进入孔隙和微裂隙后急剧膨胀,在恢复到钻孔围压过程中继续膨胀、扩张,同时在反循环抽吸力的共同作用下使土体结构破坏、断裂脱离母体;符合土体微裂隙断裂原理。  相似文献   

非均质与各向异性黏土基坑抗隆起稳定分析     

杜佐龙  黄茂松 《岩土力学》2013,34(2):455-461

经典的Prandtl 机构不能很好地反映支护结构入土深度的影响,也不能反映土体强度非均质和各向异性的影响。根据塑性极限分析上限定理,基于修正的Prandtl机构,推导了既可以合理反映支护结构入土深度影响,又可以反映土体强度非均质和各向异性特性的基坑抗隆起稳定的上限解公式,同时基于商业化程序的二次开发,建立了可以考虑土体强度非均质和各向异性影响的强度折减弹塑性有限元方法。通过提出的修正Prandtl机构上限解与强度折减有限元方法以及多块体上限解的对比,验证了修正机构上限解以及强度折减有限元法的合理性和可行性,最后讨论了非均质系数、各向异性系数、支护机构入土深度等因素对基坑抗隆起稳定性的影响,并通过了实例的验证,相关结论可供工程参考。  相似文献   

澳大利亚冷空气活动与西北太平洋台风频次的关系分析   总被引：1，自引：0，他引：1  

吴胜安 《热带气象学报》2013,29(4):641-648

利用中国气象局《台风年鉴》资料和NCEP/NCAR再分析资料,分析1968—2006年北半球夏季（6—9月）澳大利亚冷空气活动与西北太平洋夏季台风频次（WNPSTYF）的关系,并研究其影响的可能机制。结果表明,夏季澳大利亚东部对流层经向风年际增量变化与WNPSTYF年际增量变化呈显著正相关;西太平洋近赤道区对流层上层纬向风年际增量与同期WNPSTYF年际增量呈显著负相关。澳大利亚冷空气活动影响WNPSTYF的可能机理是:当澳大利亚东部从对流层低层至上层的经向风年际增量有南风异常时（此时澳大利亚西侧对流层上层有年际增量的北风异常）,冷空气在向低纬移动过程中受热上升,同时因柯氏力向左偏转,并在对流层上层向中纬度辐散,导致110～160 °E区间的南半球近赤道附近对流层上层纬向风年际增量的偏北东风异常;由于赤道上空大气运动的无旋转特性及连续性,北半球也会出现同向的纬向风年际增量异常。赤道附近对流层上层纬向风年际增量的东风异常产生纬向风的经向切变,使对流层上层出现涡度年际增量的负异常;对流层上层涡度年际增量负异常的抽吸作用导致对流层低层出现涡度年际增量的正异常,利于台风生成,导致台风年际增量偏多。反之亦反。   相似文献   

Focal Mechanism Solutions of the 2008 Wenchuan earthquake sequence from P-wave polarities and SH/P amplitude ratios: new results and implications     

Yuan Tian  Jieyuan Ning  Chunquan Yu  Chen Cai  Kai Tao 《地震科学（英文版）》2013,26(6):357-372

The 2008 Wenchuan earthquake, a major intraplate earthquake with M _w 7.9, occurred on the slowly deforming Longmenshan fault. To better understand the causes of this devastating earthquake, we need knowledge of the regional stress field and the underlying geodynamic processes. Here, we determine focal mechanism solutions (FMSs) of the 2008 Wenchuan earthquake sequence (WES) using both P-wave first-motion polarity data and SH/P amplitude ratio (AR) data. As P-wave polarities are more reliable information, they are given priority over SH/P AR, the latter of which are used only when the former has loose constraint on the FMSs. We collect data from three categories: (1) permanent stations deployed by the China Earthquake Administration (CEA); (2) the Western Sichuan Passive Seismic Array (WSPSA) deployed by Institute of Geology, CEA; (3) global stations from Incorporated Research Institutions for Seismology. Finally, 129 events with magnitude over M _s 4.0 in the 2008 WES are identified to have well-constrained FMSs. Among them, 83 are well constrained by P-wave polarities only as shown by Cai et al. (Earthq Sci 24(1):115–125, 2011), and the rest of which are newly constrained by incorporating SH/P AR. Based on the spatial distribution and FMSs of the WES, we draw following conclusions: (1) the principle compressional directions of most FMSs of the WES are subhorizontal, generally in agreement with the conclusion given by Cai et al. (2011) but with a few modifications that the compressional directions are WNW–ESE around Wenchuan and ENE–WSW around Qingchuan, respectively. The subhorizontal compressional direction along the Longmenshan fault from SW to NE seems to have a left-lateral rotation, which agrees well with regional stress field inverted by former researchers (e.g., Xu et al., Acta Seismol Sin 30(5), 1987; Acta Geophys Sin 32(6), 1989; Cui et al., Seismol Geol 27(2):234–242, 2005); (2) the FMSs of the events not only reflected the regional stress state of the Longmenshan region, but also were obviously controlled by the faults to some extent, which was pointed out by Cai et al. (2011) and Yi et al. (Chin J Geophys 55(4):1213–1227, 2012); (3) while the 2008 Wenchuan earthquake and some of its strong aftershocks released most of the elastic energy accumulated on the Longmenshan fault, some other aftershocks seem to occur just for releasing the elastic energy promptly created by the 2008 Wenchuan earthquake and some of its strong aftershocks. (4) Our results further suggest that the Longmenshan fault from Wenchuan to Beichuan was nearly fully destroyed by the 2008 Wenchuan earthquake and accordingly propose that there is less probability for great earthquakes in the middle part of the Longmenshan fault in the near future, although there might be a barrier to the southwest of Wenchuan and it is needed to pay some attention on it in the near future.  相似文献   

与挠曲作用相关的一种特殊裂缝形成机制     

董有浦  肖安成  吴磊  毛黎光  徐波 《地球科学》2013,38(4):755-762

浙江省临安市上侏罗统劳村组火山凝灰岩露头中发育了很多与挠曲相关的裂缝, 地层构造简单、露头良好, 为研究与挠曲相关裂缝提供了良好的条件.通过对两处野外露头的精细测量, 发现裂缝面平直、且未被充填, 均为构造裂缝, 在剖面上裂缝的组合呈扇形.裂缝面与岩层层面夹角为44°~80°, 裂缝密度随着地层厚度的增加而增加.根据裂缝面与层面的交切关系, 将两组裂缝分别命名为: 锐夹角指示邻层相对运动方向的D裂缝和锐夹角指示本层相对运动方向的D’裂缝.通过对地层挠曲变形的几何分析, 发现两组裂缝的形成是为了调节核部地层在变形过程中产生缩短量和剩余剪切, 地层厚度与地层中产生剩余剪切成正比.结果表明, 地层厚度越大, 形成的裂缝也越多.   相似文献   

基于黏性土分散机制的分散性土化学改性研究     

赵高文  樊恒辉  陈华  路立娜  石美 《岩土力学》2013,34(Z2):210-213

分散性土具有遇水易分散的特性,可导致堤坝等水利工程的冲蚀破坏。基于黏性土分散机制的研究,选用AlCl3• 6H2O、MgCl2•6H2O、CaCl2及CaO作为分散性土的化学改性材料,采用针孔试验和碎块试验对其改性效果进行判别和比较。试验表明,上述改性材料均可将分散性土改性为非分散性土,显著提高土体的抗冲蚀能力。结果说明：在分散性土中掺加高价态阳离子的可溶性盐,通过置换土粒表面钠离子或降低土体碱性,减小颗粒扩散层的厚度,可抑制土体的分散性,从而达到改性的目的;根据黏性土分散机制以及改性试验结果,提出了分散性土化学改性的原则,即改性材料中含有高价态的可溶性阳离子,或改性材料呈酸性,且环境友好,价格低廉,施工方便。  相似文献