A study of design spectra based on attenuation relationship of ground motion     

NI Yong-jun  ZHU Xi 《地震学报(英文版)》2001,14(6):705-710

In recent years, more and more studies are focused on the performance in seismic design instead of the strength of structures. People have realized that the structure deformation (displacement) can describe the damage more properly and directly than the strength (force). The displacement design spectra need to be constructed within more wide range of the period and the damping for the displacement-based seismic design.  相似文献   

天然金刚石的定向红外光谱研究   总被引：2，自引：2，他引：2  

杨志军  彭明生  苑执中 《矿物学报》2001,21(3):393-396

本文对天然金刚石在垂直于（100）、（110）和（111）三个方向上定向红外光谱进行了定量比较分析，指出C－H键和C－C键在以上三个方向上的浓度不相同，引起C－C键和C－C键在不同方向上的浓度差异是由于氢具有优先取代垂直于（111）方向上C－C键中碳原子的倾向。  相似文献   

Calculation of the UV Absorption Spectra of As(III) Oxo- and Thio- Acids and Anions in Aqueous Solution and of PF3 in the Gas-phase     

J. A. Tossell 《Aquatic Geochemistry》2001,7(4):239-254

Changes in the UV spectra of As(OH)₃ solutions with variations in pH and temperature have recently been used to determine the temperature dependence of the pK_a of the acid. In previous studies I used quantum mechanical techniques to study changes in structure and vibrational spectra as a function of pH for arsenites and thioarsenites. I previously calculated UV spectra for ``molecular' minerals, like realgar As₄S₄. Here I use a number of different quantum mechanical methods, both Hartree-Fock and density functional theory based, to calculate the UV spectra for both a related simple well-characterized gas-phase molecule PF₃ and for As(OH)₃ and As(SH)₃ and their conjugate anions and some neutral and anionic oligomers in aqueous solution. For the monomeric species small numbers of water molecules have been explicitly included, in a supermolecule or microsolvation approach. I find that UV absorption energies accurate to a few tenths of an eV can be obtained both for gas- phase PF₃ and for neutral arsenious acid in aqueous solution, for which the UV absorption maximum is calculated to occur around 6.5 eV, consistent with experiment. Accurate calculation of the UV energies for arsenite anions in aqueous solution is much more difficult, since basis set size and solvation effects are considerably larger than for the neutral molecules, but fairly reliable results can still be obtained. Deprotonation is found to reduce the lowest calculated UV transition energy by about half an eV. Oligomerization also reduces the lowest calculated UV energy by at least half an eV. Replacement of one or all the –OH groups by –SH groups reduces the lowest calculated UV energies by about 2 eV. UV excitation energies have been calculated for oligomeric species as large as As₃E₃(EH)₃ and As₄E₆, where E = O, S, and may be useful for identifying such species in solution.  相似文献   

北京地区一次特大强风过程边界层结构的研究   总被引：21，自引：2，他引：21  

刘小红  洪钟祥 《大气科学》1996,20(2):223-228

利用北京325 m气象塔资料对1993年4月9日北京地区出现的一次特大强风过程的边界层结构（风、温、风切变及阵风特征）进行了分析。随着该次大风的过境，边界层内风场出现数个风速高值中心，高度位于200～300 m，时间间隔1～3 h。伴随上层风速垂直切变和阵风特性。湍流能谱的计算结果表明了大尺度涡旋对边界层湍流微结构的影响。  相似文献   

太阳宇宙线高能电子能谱的形成          下载免费PDF全文

黄永年  汪学毅 《地球物理学报》1996,39(2):145-151

提出了一个太阳脉冲和经变耀斑中高能太阳宇宙线电子能谱的形成模型，探讨了高能电子通过日冕捕获区的库仑损失、轫致辐射和同步辐射等物理过程，首次研究了日冕等离子体尾场对太阳宇宙线电子的加速及其能谱的形成．所得结果和观测谱能很好地符合，从而较合理地阐明了脉冲耀斑和经变耀斑两类太阳宇宙线高能电子谱的结构．  相似文献   

植物在不同形态和不同状态下的荧光光谱特征研究     

吴荣  张崇静  朱永豪  刘南英  沈玉其  徐彬彬  石晓日  李德成  周斌 《遥感学报》1992,(Z1)

本文从光合作用的角度出发,讨论了植物叶片在不同形态、不同状态下的荧光光谱特征以及它们对荧光光谱的影响。文章涉及了以下几方面的内容:(1)植物在离体形态和活体形态下的荧光光谱特征;(2)叶片正面与反面的荧光光谱特征;(3)植物不同器官对荧光光谱的影响;(4)叶片放置时间对荧光光谱的影响;(5)叶片经不同处理时对荧光光谱的影响等。其目的是为激光荧光技术用于植被遥感的实施提供基础数据。  相似文献   

ISO Far-IR spectroscopy of IR-bright galaxies and ULIRGs     

J. Fischer  M.L. Luhman  S. Satyapal  M.A. Greenhouse  G.J. Stacey  C.M. Bradford  S.D. Lord  J.R. Brauher  S.J. Unger  P.E. Clegg  H.A. Smith  G. Melnick  J.W. Colbert  M.A. Malkan  L. Spinoglio  P. Cox  V. Harvey  J.-P Suter  V. Strelnitski 《Astrophysics and Space Science》1999,266(1-2):91-98

Based on far-infrared spectroscopy of a small sample of nearbyinfrared-bright and ultraluminous infrared galaxies (ULIRGs) with theISO Long Wavelength Spectrometer we find adramatic progression in ionic/atomic fine-structure emission line andmolecular/atomic absorption line characteristics in these galaxiesextending from strong [O III]52,88 m and [N III]57 m lineemission to detection of only faint [C II]158 m line emissionfrom gas in photodissociation regions in the ULIRGs. The molecularabsorption spectra show varying excitation as well, extending fromgalaxies in which the molecular population mainly occupies the groundstate to galaxies in which there is significant population in higherlevels. In the case of the prototypical ULIRG, the merger galaxy Arp220, the spectrum is dominated by absorption lines of OH, H₂O, CH,and [O I]. Low [O III]88 m line flux relative to the integratedfar-infrared flux correlates with low excitation and does not appear tobe due to far-infrared extinction or to density effects. A progressiontoward soft radiation fields or very dusty H II regions may explainthese effects.  相似文献   

土层结构对反应谱特征周期的影响   总被引：20，自引：3，他引：17  

薄景山  李秀领  刘德东  刘红帅 《地震工程与工程振动》2003,23(5):42-45

本文选取和构造了若干有工程意义的典型场地剖面,利用目前工程上广泛应用的场地地震反应分析的一维等效线性化波动方法,计算了在不同地震动输入下的不同场地剖面的地表加速度峰值和地表速度峰值。利用计算得到的地表加速度峰值和速度峰值计算了不同场地在不同地震动输入下的反应谱的特征周期。研究了不同土层结构对地表加速度反应谱特征周期的影响,获得了一些有意义的结果。  相似文献   

Multi‐variable relations for soil effects on seismic ground motion     

George D. Bouckovalas  Achilleas G. Papadimitriou 《地震工程与结构动力学》2003,32(12):1867-1896

Soil effects on peak ground acceleration, velocity and elastic response spectra (5% damping) are expressed by simple approximate relations in terms of five key parameters: (a) the fundamental vibration period of the non‐linear soil, T_S, (b) the period of a bedrock site of equal thickness, T_b, (c) the predominant excitation period, Te, (d) the peak seismic acceleration at outcropping bedrock, a, and (e) the number of significant excitation cycles, n. Furthermore, another relation is proposed for the estimation of T_S in terms of the soil thickness H, the average shear wave velocity of the soil V?_S,o and a. The aforementioned parameters were first identified through a simplified analytical simulation of the site excitation. The multivariable approximate relations were then formulated via a statistical analysis of relevant data from more than 700 one‐dimensional equivalent‐linear seismic ground response analyses, for actual seismic excitations and natural soil conditions. Use of these relations to back‐calculate the numerical results in the database gives an estimate of their error margin, which is found to be relatively small and unbiased. The proposed relations are also independently verified through a detailed comparison with strong motion recordings from seven well‐documented case studies: (a) two sites in the San Fernando valley during the Northridge earthquake, and (b) five different seismic events recorded at the SMART‐1 accelerometer array in Taiwan. It is deduced that the accuracy of the relations is comparable to that of the equivalent‐linear method. Hence, they can be readily used as a quick alternative for routine applications, as well as for spreadsheet computations (e.g. GIS‐aided seismic microzonation studies) where numerical methods are cumbersome to implement. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Peculiarities of the UV continuum energy distribution for T Tauri stars     

A. S. Kravtsova  S. A. Lamzin 《Astronomy Letters》2003,29(9):612-620

In the UV spectra of BP Tau, GW Ori, T Tau, and RY Tau obtained with the Hubble Space Telescope, we detected an inflection near 2000 Å in the F _λ ^c (λ) curve that describes the continuum energy distribution. The inflection probably stems from the fact that the UV continuum in these stars consists of two components: the emission from an optically thick gas with T<8000 K and the emission from a gas with a much higher temperature. The total luminosity of the hot component is much lower than that of the cool component, but the hot-gas radiation dominates at λ<1800 Å. Previously, other authors have drawn a similar conclusion for several young stars from low-resolution IUE spectra. However, we show that the short-wavelength continuum is determined from these spectra with large errors. We also show that, for three of the stars studied (BP Tau, GW Ori, and T Tau), the accretion-shock radiation cannot account for the observed dependence F _λ ^c (λ) in the ultraviolet. We argue that more than 90% of the emission continuum in BP Tau at λ>2000 Å originates not in the accretion shock but in the inner accretion disk. Previously, a similar conclusion was reached for six more classical T Tau stars. Therefore, we believe that the high-temperature continuum can be associated with the radiation from the disk chromosphere. However, it may well be that the stellar chromosphere is its source.  相似文献