Products and mechanisms of the gas phase reactions of NO3 with CH3SCH3, CD3SCD3, CH3SH and CH3SSCH3     

N. R. Jensen  J. Hjorth  C. Lohse  H. Skov  G. Restelll 《Journal of Atmospheric Chemistry》1992,14(1-4):95-108

Products and mechanisms of the reaction between the nitrate radical (NO₃) and three of the most abundant reduced organic sulphur compounds in the atmosphere (CH₃SCH₃, CH₃SH and CH₃SSCH₃), have been studied in a 480 L reaction chamber using in situ FT-IR and ion chromatography as analytical techniques. In the three reactions, methanesulphonic acid was found to be the most abundant sulphur containing product. In addition the stable products SO₂, H₂SO₄, CH₂O, and CH₃ONO₂ were identified and quantified and thionitric acid-S-methyl ester (CH₃SNO₂) was observed in the i.r. spectrum from all of the three reactions. Deuterated dimethylsulphide (CD₃SCD₃) showed an isotope effect on the reaction Deuterated dimethylsulphide (CD₃SCD₃) showed an isotope effect on the reaction rate constant (k_H/k_D) of 3.8±0.6, indicating that hydrogen abstraction is the first step in the NO₃+CH₃SCH₃ reaction, probably after the formation of an inital adduct.Based on the products and intermediates identified, reaction mechanisms are proposed for the three reactions.  相似文献   

SH固土剂在遗址土中的渗透注浆扩散规律     

谌文武  张起勇  刘宏伟 《岩土力学》2019,40(2):429-435

风化是中国西北地区土遗址最常见的病害之一。土遗址防风化方法主要是表面喷洒和钻孔注浆。通过对不同干密度重塑土样的钻孔注浆试验,来寻找改性聚乙烯醇（SH）固土剂扩散规律,建立了SH固土剂渗透范围模型——旋转抛物体,解释了产生该渗透现象的原因,并通过计算得到了SH固土剂渗透加固土体体积以及渗透范围内SH的固含量,确定了土遗址中含该固含量的SH固土剂足以对其产生防风化的作用。利用Image J图像分析软件对SEM照片进行处理,获得了不同干密度条件下孔隙分布、孔隙分形维数和平均Feret直径。研究发现,随着干密度增大,土体渗透性减弱,其主要原因是中、大孔隙被压缩成微、小孔隙,并建议将SH固土剂渗透注浆应用于平均Feret直径大于4.98 ?m的土体。最后通过多元线性回归的方法发现,注浆量对渗透半径影响最大,其次是平均Feret直径,孔径的影响最小。  相似文献   

Diffraction of anti-plane SH waves by a semi-circular cylindrical hill with an inside concentric semi-circular tunnel   总被引：8，自引：3，他引：5  

Vincent W.Lee  罗昊  梁建文 《地震工程与工程振动(英文版)》2004,3(2):249-262

A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semicylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method. The solution is reduced to solving a set of infinite linear algebraic equations. Fourier expansion theorem with the form of complex exponential function and cosine function is used. Numerical solutions are obtained by truncation of the infinite equations. The accuracy of the presented numerical results is carefully verified.  相似文献   

NWMEFENS方法的数值稳定性     

张晓志  屈成忠  谢礼立 《世界地震工程》2008,24(1):77-81

概要总结了NWMEFENS方法及其主要创新点.对采用该方法求解点源出平面波动问题时的数值稳定性和精度进行了数值试验研究.研究结果表明:对于合理的时空离散步距,该方法的阻尼稳定性、近场稳定性较之现有同类方法具有显著提高.  相似文献   

弹性层状半空间中凸起地形对入射平面SH波的放大作用   总被引：7，自引：0，他引：7  

梁建文  巴振宁 《地震工程与工程振动》2008,28(1):1-10

对Wolf理论进行拓展,使之可解决凸起地形对波的散射问题,进而利用间接边界元法,求解了弹性层状半空间中凸起地形对入射平面SH波的放大作用问题。本文模型的显著特点之一是考虑了层状半空间的动力特性以及层状半空间和凸起地形的阻尼;特点之二是计算精度高。文中以基岩上单一土层中半圆凸起地形对入射平面SH波的放大作用为例进行了数值计算分析。研究表明,基岩上单一土层中凸起地形对入射平面SH波放大作用和均匀半空间中凸起地形有着本质的差别;土层动力特性不仅影响凸起地形地表位移的幅值,还会影响地表位移的频谱;阻尼会显著降低凸起地形对高频波的放大作用。  相似文献   

Soil-structure interaction on shallow rigid circular foundation: plane SH waves from far-field earthquakes     

Vincent W. Lee  Hao Luo 《地震工程与工程振动(英文版)》2014,13(1):29-45

A closed-form wave function analytic solution of two-dimensional scattering and diffraction of incident plane SH-waves by a fl exible wall on a rigid shallow circular foundation embedded in an elastic half-space is presented. This research generalizes the previous solution by Trifunac in 1972, which tackled only the semi-circular foundation, to arbitrary shallow circular-arc foundation cases, and is thus comparatively more realistic. Ground surface displacement spectra at higher frequencies are also obtained. As an analytical series solution, the accuracy and error analysis of the numerical results are also discussed. It was observed from the results that the rise-to-span ratio of the foundation profi le, frequency of incident waves, and mass ratios of different media(foundation-structure-soil) are the three primary factors that may affect the surface ground motion amplitudes near the structure.  相似文献   

On planar seismic wavefront modeling for estimating rotational ground motions: Case of 2-D SH line-source     

《Soil Dynamics and Earthquake Engineering》2016

At large hypocentral distances, it is convenient to approximate the curved transient seismic wavefronts as planar to estimate rotational ground motions from the single-station recordings of translational ground motions. In this paper, we investigate whether and when this approximation, referred to as the ‘plane-wave’ approximation, can be considered adequate close to the source. For this, we consider a simplistic source model comprising a two-dimensional, kinematic shear dislocation SH line-source buried in a homogenous, elastic half-space and assume this to be an equivalent representation of a finite-sized fault. The ‘plane-wave’ rotational motion is then synthesized from the exact translational motion solution to the assumed model and compared with the exact rotational motion solution for this model. The comparison between the two sets of rotational amplitudes in frequency domain suggests that the plane-wave approximation may be adequate, when the wavelengths of the seismic waves are much smaller than the source depth. When this is not true, the plane-wave approximation is seen to underestimate the Fourier amplitudes close to the source by several orders, particularly when the fault planes are vertically oriented. A similar comparison in the time domain indicates that a severe underestimation may also occur when the source rise time is longer than the shear-wave arrival time at the epicenter. Significant discrepancies are also observed between the waveforms of the exact and plane-wave rotational motions.  相似文献   

含断层破碎带场地对平面SH波的放大作用   总被引：2，自引：0，他引：2       下载免费PDF全文

梁建文  冯领香  巴振宁 《地震学报》2010,32(3):300-309

借助Wolf的土层和半空间精确动力刚度矩阵和斜线荷载格林函数,采用间接边界元法在频域内求解了含断层破碎带场地对SH波的放大作用,着重分析了破碎带较窄断层两侧围岩动力响应的基本规律及场地动力特性对散射的影响.结果表明,断层破碎带对SH波有显著的影响,即使破碎带很窄,也可对SH波产生很大的放大作用;层状场地动力特性对放大作用有显著的影响.  相似文献   

含多个圆弧状沉积层河谷场地对平面SH波散射问题的解析解     

杨彩红  梁建文  张郁山 《地震工程与工程振动》2010,30(3)

利用波函数展开法给出了含多个圆弧状沉积层河谷(盆地)场地对平面SH波二维散射问题的一个解析解,并以具有三个沉积层的河谷为例,分析了河谷中沉积层层数与排列次序对SH波散射的影响。  相似文献   

Seismic response of multi-layered basins with velocity gradients upon incidence of plane shear waves     

Yong Zeng  Rafael Benites 《地震工程与结构动力学》1998,27(1):15-28

A boundary integral scheme based on boundary-integral discrete-wave-number approach has been developed to compute the seismic response of two-dimensional irregular-shaped basins with horizontal soil layers. Each layer exhibits a linear gradient of shear wave velocity with depth. The approach combines the boundary-integral representation of the seismic wave field outside the basin with plane wave representation of the seismic wave field inside the basin. The propagation throughout the layers is performed by matrix propagators in which the effect of the vertical variation of the velocity is incorporated by using confluent hyper-geometric functions of the Whittaker type. Our method is tested against otherwell-accepted solutions for the case of a circular basin with excellent agreement. Test of the ground response for a semi-circular basin with radius a shows that stable solutions are obtained if the chosen model parameters satisfy following conditions: (1) the distance from the sources to the interface is greater than 0·1a; (2) the distance between the sources is smaller than a quarter of the incident wavelength; and (3) the discrete wave-number step is smaller than 2π/4a. The computation of ground response of basins with a sharp interface and several horizontal deposits leads to the following main results: (1) the amplification of a basin with velocity gradients is larger than that of a basin with homogeneous layers; (2) the frequencies of the second- and third-order harmonics for a basin with velocity gradients are lower than those of a basin with homogeneous layers; and (3) the response amplitude of the basin with velocity gradients attenuates more slowly in time domain than when layers are homogeneous. Since these results have been obtained for realistic values of basin geometrical and mechanical consideration, they should find some interest in earthquake engineering or seismic microzonation studies. © 1998 John Wiley & Sons, Ltd.  相似文献