EARTHQUAKE SCALING PARADOX

Two measures of earthquakes, the seismic moment and the broadband radiated energy, show completely different scaling relations. For shallow earthquakes worldwide from January 1987 to December 1998, the frequency distribution of the seismic moment shows a clear kink between moderate and large earthquakes, as revealed by previous works. But the frequency distribution of the broadband radiated energy shows a single power law, a classical Gutenberg-Richter relation. This inconsistency raises a paradox in the self-organized criticality model of earthquakes.     

论不确定性结构力学的发展

结构力学是直接为工程结构设计服务的,而工程设计中包含大量不确定性因素和信息,包括随机性、模糊性和未确知性信息.由于引用统计数学方法处理随机性问题,在结构力学中产生了可靠性理论和随机振动理论.随着模糊性和未确知性问题的提出和研究,近年来在结构力学中又逐渐形成了一些新的分支,包括结构的不确定性优化设计,广义(模糊随机)可靠性理论,模糊随机振动理论和模糊地震工程学等.本文简要地介绍这四个新的分支的发展情况,主要介绍作者及其学生们的工作,并着重介绍基本概念.      

Inelastic coupled response of eccentric buildings with respect to different earthquake intensity

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｂｅｈａｖｉｏｒｏｆｌａｔｅｒａｌ＿ｔｏｒｓｉｏｎａｌｃｏｕｐｌｅｄｂｕｉｌｄｉｎｇｉｎｔｈｅｉｎｅｌａｓｔｉｃｒａｎｇｅｈａｄｂｅｅｎｗｉｄｅｌｙｉｎｖｅｓｔｉｇａｔｅｄ.ＫａｎａｎｄＣｈｏｐｒａ(1981)[1]ｓｔｕｄｉｅｄａｏｎｅ＿ｓｔｏｒｙｍｏｄｅｌｗｉｔｈｓｉｎｇｌｅｌａｔｅｒａｌｒｅｓｉｓｔａｎｔｅｌｅｍｅｎｔａｎｄｒｅａｃｈｅｄｔｈｅｃｏｎｃｌｕｓｉｏｎｔｈａｔｇｅｎｅｒａｌｌｙｔｈｅｒｅｓｐｏｎｓｅｉｎｔｈｅｉｎｅｌａｓｔｉｃｒａｎｇｅｉｓａｆｆｅｃｔｅｄｂ…     

In Vitro Monitoring of Live Cardiomyocytes Dynamics by a Scanning Near Field Optical Microscope Setup

We describe an original scanning near field optical microscope setup developed to examine rhythmically beating cardiac myocytes fully immersed in culture media. Scans could be halted at any point to record localized contraction profiles. Contractions could be detected with high sub nanometric vertical sensitivity and changed shape dramatically within adjacent sub micron-sized areas. We believe that the spatial dependency of contractions arises because of system’s ability to resolve the dynamic behavior of individual sub membrane actin bundles. Our results, combining imaging and real time recording in localized areas, reveal a new, non-invasive method for studying sub micron morphological activity in live biological samples.This paper was originally presented at the 5th International Conference on NEAR FIELD OPTICS and RELATED TECHNLOGIES (NFO-5), which was held on December 6–10, 1998 at Coganoi Bay Hotel, Shirahama, Japan, in cooperation with the Japan Society of Applied Physics and Mombusho Grant-in Aid for Scientific Research on Priority Areas “Near-Field Nano-optics” Projects, sponsored by Japan Society for the Promotion of Science.     

地震作用下摩擦耗能减震结构优化

提出了地震作用下摩擦耗能支撑参数优化的一种新的数学模型。它的特点是在给定的几条地震波作用下,在满足框架的规范层间位移角限值要求下,框架各层安装的耗能支撑刚度之和最小,从而实现安装较少的耗能装置而能达到相同的抗震要求。本文利用遗传算法求解该优化问题,并编制了基于遗传算法的几条地震波分别作用下的摩擦耗能框架结构支撑参数弹塑性动力优化分析程序GAOFF。最后给出了一6层框架在三条地震波分别输入下的优化算例,分析结果表明本文方法是有效的。     

Novel mechanism for discrete scale invariance in sandpile models

Numerical simulations and a mean-field analysis of a sandpile model of earthquake aftershocks in 1d, 2d and 3d Euclidean lattices determine that the average stress decays in a punctuated fashion after a main shock, with events occurring at characteristic times increasing as a geometrical series with a well-defined multiplicative factor which is a function of the stress corrosion exponent, the stress drop ratio and the degree of dissipation. These results are independent of the discrete nature of the lattice and stem from the interplay between the threshold dynamics and the power law stress relaxation. This novel mechanism of log-periodicity does not rely on a pre-existing discrete structural hierarchy of faults but is dynamical and reflects the existence of an approximately fixed stress drop together with the scale-free stress corrosion power law acting during inter-seismic phases. Received 24 November 1999     

Transmission Properties of the Femtosecond Pulse Through a Near-field Optical Fiber probe

The experimental results are given on the broadening characteristics of the time and frequency profile of the femtosecond pulse passed through a SNOM fiber probe. The power threshold for the spectral and temporal broadening was 158 μw for pulses with 250 fs width and the repetition rate of 250 kHz at 830 nm wavelength. The time broadening reached lps for 250 fs incident pulse of 500 μw. A finite-difference time-domain (FDTD) simulation was carried out to illuminate the transmission properties of ultrafast pulse through the SNOM probe. The broadening influence on temporal resolution spectrum and near-field fluorescence excited by two-photon technique are discussed.     

Transmission Properties of the Femtosecond Pulse Through a Near-field Optical Fiber probe

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｔｈｅｕｌｔｒａｆａｓｔｐｕｌｓｅｓｃａｎｎｉｎｇｎｅａｒ ｆｉｅｌｄｏｐｔｉｃａｌｍｉｃｒｏｓｃｏｐｙａｎｄｔｅｍｐｏｒａｌｒｅｓｏｌｕｔｉｏｎｎｅａｒ ｆｉｅｌｄｓｐｅｃｔｒａｌｔｅｃｈｎｉｑｕｅ,ｗｈｉｃｈｄｅｖｅｌｏｐｅｄｆｒｏｍｔｈｅｃｏｍｂｉｎａｔｉｏｎｏｆｓｃａｎｎｉｎｇｎｅａｒ ｆｉｅｌｄｏｐｔｉｃａｌｍｉｃｒｏｓｃｏｐｙ (ＳＮＯＭ )ａｎｄｔｈｅｕｌｔｒａｆａｓｔｐｕｌｓｅ,ｈａｖｅａｔｔｒａｃｔｅｄｇｒｅａｔｉｎｔｅｒｅｓｔ[1～ 3] .Ｔｈｅｓｅｔｅｃｈ…     

近场光学显微镜下的生物世界

扫描近场光学显微镜由于其超过常规光学显微镜的光学分辨能力及其一些特殊的功能,正在受到生物学家们越来越多的关注。文章介绍了近年来近场光学显微技术在生命科学研究中的应用和进展。     

Nano-Raman spectroscopy with side-illumination optics

We describe an apertureless near-field Raman spectroscopy setup that has successfully produced substantial enhancements for a wide variety of samples and achieved a high contrast. The tremendous potential of tip-enhanced Raman spectroscopy (TERS) for nanoscale chemical characterization has been demonstrated by various groups by measuring organic dyes, biological molecules, single-walled carbon nanotubes and silicon. Keys to rapid advances in the application of TERS to pressing scientific problems include the optimization of the method to achieve greater reproducibility and greater enhancement factors if possible, but more importantly, greater imaging contrast. Using a side-illumination geometry, we demonstrate reproducible enhancements of the Raman signal per volume on the order of 10³–10⁴ using silver- and gold-coated tips on various molecular, polymeric and semiconducting materials as well as on carbon nanotubes. We have experimentally verified localization of the enhancement to a depth of ∼20 nm. Most importantly, optimization of the polarization geometry makes possible a contrast between the near-field and far-field signals of 900% in the case of silicon—a level that makes the technique attractive for various applications. Copyright © 2005 John Wiley & Sons, Ltd.