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991.
992.
993.
在役结构抗震评估地震作用取值研究 总被引:7,自引:0,他引:7
本文阐述了研究在役结构评估用地震作用取值的必要性。并提出了评估基准期和评估烈度的概念;根据现有的烈度分布函数。建立了考虑不同评估基准期和不同地区地震危险性差异的地震烈度概率模型;按照等超越概率原则,提出了确定在役结构抗震评估用地震烈度的取值标准和方法,并给出了强度验算和变形验算地震作用参数的具体取值;对服役期间已遭遇过地震的结构。提出了烈度调整建议,为在役结构的抗震安全性评估提供了合理可行的荷载标准。 相似文献
994.
Ideal-gas thermodynamic properties for natural-gas applications 总被引:2,自引:0,他引:2
Calculating caloric properties from a thermal equation of state requires information such as isobaric heat capacities in the ideal-gas state as a function of temperature. In this work, values for the parameters of thec
p
0
correlation proposed by Aly and Lee were newly determined for 21 pure gases which are compounds of natural gas mixtures. The values of the parameters were adjusted to selectedc
p
0
data calculated from spectroscopic data for temperatures ranging from 10 to 1000 K. The data sources used are discussed and compared with literature data deduced from theoretic models and caloric measurements. The parameters presented will be applied in a current GERG project for evaluating equations of state (e.g., the AGA 8 equation) for their suitability for calculating caloric properties. 相似文献
995.
Measurement of interfacial fracture parameters using coherent gradient sensing (CGS) 总被引:1,自引:0,他引:1
An optical interferometry called coherent gradient sensing (CGS) has been extended for mapping interface crack tip fields and for evaluating fracture parameters. The optical technique is a double grating shearing interferometer with an on line spatial filtering arrangement. The method offers real time full field measurements and can be used both in transmission made and reflection mode. The interferometer measures small angular deflections of light rays which can be further related to in plane gradients of x + y in transmission through elasto-optic relations. Direct interfacial crack tip measurements in a high stiffness mismatch PMMA-aluminium bimaterial system are performed. A variety of crack tip mode mixities are studied using asymmetric four point bend specimens subjected to different far field mechanical loads. The. complex stress intensity factors and the associated phase angles are measured from CGS patterns using an asymptotic expansion field. The measurements are compared with finite element results. 相似文献
996.
本文计算了厚壁筒的动态应力强度因子,研究了有限单元法计算动态应力强度因子的几个主要问题,提供了合理计算方案,本文还提供了计算厚壁筒动态应力强度因子的叠加积分法,方便于各种动态内压下的动态应力强度因子的计算。 相似文献
997.
Acoustic determination of ideal-gas heat capacity and second virial coefficients of some refrigerants between 250 and 420 K 总被引:1,自引:0,他引:1
An apparatus for speed-of-sound measurements with a spherical resonator was adapted for temperatures up to 42(I K. This included new microphones with a special wiring, a pressure indicator which can be thermostatted to 420 K, and some installations to avoid temperature gradients. Calibration of the radius of the resonator with argon was extended to higher temperatures. Speed-of-sound measurements up to 420 K and 0.5 MPa were done onl,l-dilluoroethane (R152a). 1.l,l-trilluoroethane (R 143a ),l,l,l-chlorodifluoroethane (R 142b ), l,1,1,2-tetralluoroethane (R134a), and 2.2.2-trifluoroethanol. The ideal-gas heat capacities coincide with the statistical mechanical values, except for R134a, where our values as well as recent literature data are below the values calculated from spectroscopy. The reduced second virial coefficients can be interpreted in terms of the dipole moment and the angle between dipole moment and molecular axis. For the associated substance trifluoroethanol values of the third virial coefficient are given, which are appreciably negative at low temperatures.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994 Boulder, Colorado, U.S.A. 相似文献
998.
999.
Polarization artefacts of an FTIR microscope and the consequences for intensity measurements on anisotropic materials 总被引:1,自引:0,他引:1
The infrared beam on both the main Nicolet Nexus bench and the attached Spectra‐Tech Continuum microscope has been shown to be partially polarized. The degree of polarization is ≈ 30%. Although the state of polarization of the infrared beam is of no consequence when measuring the spectra of isotropic materials (gases, liquids), there is a potential problem when considering the spectra of anisotropic materials. Single band intensities are particularly prone to error as small changes in sample thickness or orientation directly affect the intensity. Thickness effects can be overcome by measuring intensity ratios. However, because of the partially polarized nature of the infrared beam, even intensity ratios, illustrated here by the ratio amide I/II of collagen fibres, vary with sample orientation. If overlooked, this effect can be problematic when measuring infrared spectra with an FTIR microscope from samples that are anisotropic or contain anisotropic domains, even though they may appear isotropic on a macroscopic scale. Because dichroic ratios remain unaffected, the intensity ratio from two bands with different transition moments may be used to give a strong indication of the orientation of the sample. This work is illustrated by reference to the FTIR spectra of orientated polyethylene, collagen tape and human trabecular bone. 相似文献
1000.
角锥棱镜阵列式反射镜反光性能及其评价的研究 总被引:4,自引:0,他引:4
角锥棱镜阵列式反射镜由角锥棱镜列阵构成,是用光学塑料注塑制造的。本文论述了这种反向镜反射光发散角的形成和反射光有效通光口径与入射角的系统等理论,提出了应从制造和使用角度考虑分别用新单项参数和综合参数来评定其反光性能,同时还提出了对各项参数的测量方法。 相似文献