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231.
Sedimentological constraints on hydrometeor-enhanced particle deposition: 1992 Eruptions of Crater Peak, Alaska 总被引:2,自引:2,他引:0
Water is a dominant component of volcanic clouds and has fundamental control on very fine particle deposition. Particle size characteristics of distal tephra-fall (100s km from source volcano) have a higher proportion of very fine particles compared to predictions based on single particle settling rates. In this study, sedimentological analyses of fallout from for the 18 August and 16–17 September 1992 eruptions of Crater Peak, Alaska, are combined with satellite observations, and cloud trajectory and microphysics modeling to investigate meteorological influences on particle sedimentation. Total grain size distributions of tephra fallout were reconstructed for both Crater Peak eruptions and indicate a predominance of fine particles < 125 μm. Polymodal analysis of the deposits has identified a particle subpopulation with mode ~ 15–18 μm involved in particle aggregation. Accounting for the magmatic water source only, calculated ice water content of the 3.7 hour old September 1992 Spurr cloud was ~ 4.5 × 10− 2 g m− 3 (based on an estimated cloud thickness of ~ 1000 m from trajectory modeling). Hydrometeor formation on particles in the volcanic cloud and subsequent sublimation may induce a cloud base instability that leads to rapid bulk (en masse) sedimentation of very fine particles through a mammatus-like mechanism. 相似文献
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Structural vibration passive control and economic analysis of a high-rise building in Beijing 总被引:1,自引:0,他引:1
Performance analysis of the Pangu Plaza under earthquake and wind loads is described in this paper.The plaza is a 39-story steel high-rise building,191 m high,located in Beijing close to the 2008 Olympic main stadium.It has both fluid viscous dampers(FVDs) and buckling restrained braces or unbonded brace(BRB or UBB) installed.A repeated iteration procedure in its design and analysis was adopted for optimization.Results from the seismic response analysis in the horizontal and vertical directions show that th... 相似文献
234.
Lucija Boskovic Igor S. Altman Roger D. Braddock Igor E. Agranovski 《洁净——土壤、空气、水》2009,37(11):843-849
Elongated aerosol particle removal on fibrous filters has been investigated. It was shown that particle agglomerates are removed much more efficiently compared to the regularly shaped single particles with identical electrical mobility diameter at two filtration velocities tested. The experimental results were compared with the classical filtration theory and it was shown that the theoretical predictions, which are based on the assumption that the particles are spherical, are significantly different compared to an agglomerate filtration efficiency value. In order to account for a particle shape non-regularity, dominating nanoparticle removal mechanisms were firstly evaluated for a regular particle of certain size and then adjusted by fitting coefficients k1 (for diffusion component) and k2 (for interception). These coefficients were determined by fitting the theoretical values that gives the best coincidence with the measured data points. As was further demonstrated theoretically, the coefficient k1 is identical to the ratio of the actual particle surface area to the surface area of the spherical particle of the equivalent diameter. On the other hand, the coefficient k2 was found to be equal to the ratio of the projection of a given particle on a plane perpendicular to a streamline, to that of the spherical particle of the equivalent diameter. The reported findings would allow undertaking more accurate evaluation of the removal efficiency of non-regular aerosol particle, which is especially important for industrial applications where non-regular aerosols are frequently met. 相似文献
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应用渗流力学的基本原理,研究油气初次运移的机制问题。研究认为,油气的初次运移是以连续相、而不是以溶液相和扩散相的形式进行的;油气初次运移的动力是浮力,因而初次运移的方向是向上的;油气初次运移所需的时间与源岩的渗透能力有关,与油气的粘度有关,还与源岩的厚度有关;油气藏的异常高压是一种暂时的压力状态,气藏的异常高压多于油藏,新生油气藏多于古油气藏;油气初次运移的通道就是源岩的粒间孔隙,源岩的非均质性和微裂缝对油气初次运移十分不利,因形成微油气藏而降低油气运移效率;源岩的厚度越大,越有利于油气聚集;“倒灌”现象是不存在的,缺少基本的动力驱动,基岩油气藏的形成是二次运移过程中侧向运移的结果。初次运移与二次运移具有相同的动力机制、运移相态和运移方向,因而两者是完全统一的。 相似文献
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238.
基于FLAC3D岩石黏弹塑性流变模型的二次开发研究 总被引:14,自引:1,他引:13
由于岩土介质的复杂多样性,通用分析软件所提供的岩石流变本构模型往往不能满足工程实际数值分析的需要。依据FLAC3D(Version 2.1)所提供的二次开发程序接口,结合西原黏弹塑性流变模型分析了二次开发程序运行的基本原理,给出了西原流变模型具体实施的程序框图和代码编写中应该注意的几个关键技术。通过一个简单的算例验证了程序编制的正确性与可靠性。由于采用了面向对象的程序技术,FLAC3D二次开发接口更加简单实用,提供的研究思路可为其他流变本构模型的二次开发提供参考。 相似文献
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240.
Betty K. Pun Christian Seigneur Daniel Grosjean Pradeep Saxena 《Journal of Atmospheric Chemistry》2000,35(2):199-223
Atmospheric particles contain a myriad of organiccompounds, including many multifunctional,water-soluble organic compounds. Many of thesecompounds are postulated to be secondary of origin. This work investigates the possible precursors ofseveral classes of multifunctional, water-solublesecondary organic compounds by analyzing the pathwaysleading to their formation, based on known gas-phasereactions. The analysis is termed `retrosynthetic'due to the backward direction of the analysis, fromproducts to precursors. Pathways for multi-functionalcompounds were generated combinatorially, consideringthe formation of one functional group at a time.Many multifunctional organic compounds with carboxylicacid, carbonyl, and hydroxy functional groups werefound to be first- or second-generation products ofcommon anthropogenic and biogenic volatile organiccompounds such as alkanes, alkenes, aromatics, andcyclic alkenes. The estimated yields of water-solubleorganic compounds from primary precursors ranged fromless than 1% to over 10%, based on stoichiometricconsiderations. The SOA formation index, whichcombines the concepts of yields and rates, was used tocompare the feasibility of the retrosyntheticpathways. Many of the candidate pathways involve theisomerization reaction of alkoxy radicals andoxygenated intermediate products such asmonocarboxylic acids and hydroxyaldehydes. 相似文献