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Attenuation of ground vibrations due to different technical sources 被引量:6
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作者 L.Auersch s.said 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2010年第3期337-344,共8页
The attenuation of technically induced surface waves is studied theoretically and experimentally. In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road a... The attenuation of technically induced surface waves is studied theoretically and experimentally. In this paper, nineteen measurements of ground vibrations induced by eight different technical sources including road and rail traffic, vibratory and impulsive construction work or pile driving, explosions, hammer impulses and mass drops are described, and it is shown that the technically induced ground vibrations exhibit a power-law attenuation v - r ~ where the exponents q are in the range of 0.5 to 2.0 and depend on the source types. Comparisons performed demonstrate that the measured exponents are considerably higher than theoretically expected. Some potential effects on ground vibration attenuation are theoretically analyzed. The most important effect is due to the material or scattering damping. Each frequency component is attenuated exponentially as exp(-kr), but for a broad-band excitation, the sum of the exponential laws also yields a power law but with a high exponent. Additional effects are discussed, for example the dispersion of the Rayleigh wave due to soil layering, which yields an additional exponent of 0.5 in cases of impulsive loading. 展开更多
关键词 wave attenuation environmental vibrations field tests material damping scattering damping Rayleigh wave
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经肛内窥镜微损伤外科10年经验总结——组织学和临床分析
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作者 s.said D.Stippel 张林 《德国医学》 CAS 1997年第4期217-218,共2页
大于2cm的宽基息肉,即使是用镊子牵拉人工造成一个蒂或经基底注射产生一个假蒂,用圈套法仍不能安全摘除。为防止复发、再出血和穿孔必须彻底治疗。本人从近期和远期结果介绍了经肛内窥镜手术系统及其优点。 主要适应证是:摘除直径>2c... 大于2cm的宽基息肉,即使是用镊子牵拉人工造成一个蒂或经基底注射产生一个假蒂,用圈套法仍不能安全摘除。为防止复发、再出血和穿孔必须彻底治疗。本人从近期和远期结果介绍了经肛内窥镜手术系统及其优点。 主要适应证是:摘除直径>2cm的宽基直肠腺瘤、早期肿瘤、局限性非硬化性癌的姑息切除以及有剖腹手术禁忌证或病人拒绝经腹手术时。禁忌证:腹膜内直肠癌和在乙状结肠区已扩散的腺瘤(>5cm)。 展开更多
关键词 内窥镜 经肛内窥镜 微损伤器械 直肠 结肠 息肉
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