LOCALLY NONLINEAR STOCHASTIC ANALYSIS OF OFFSHORE STRUCTURES

This paper' presents a simple method for the stochastic dynamic analysis of some offshore platforms with localized nonlinearity. The transfer function of the platform with initial linear stiffness is first determined, and the nonlinear iteration is performed on the condensed stiffness matrix only. Computational efforts are reduced. This method can be used to analyze a fixed platform on nonlinear foundation and a guyed tower platform having nonlinear guylines.     

The IRS 1 circumstellar disk, and the origin of the jet and CO outflow in B5

We report the discovery of the inner edge of the high velocity CO outflow associated with the bipolar jet originating from IRS 1 in Barnard 5 and the first ever resolution of its circumstellar disk in the 2.6 mm dust continuum and C18O. From high spatial resolution observations made with the Owens Valley Millimeter Array we are able to locate the origin of the outflow to within approximately 500 AU on either side of IRS 1 and apparently at the edge of, or possibly within, its circumstellar disk. The orientation of the continuum disk is perpendicular to the highly collimated jet outflow recently seen in optical emission at much farther distances. The disk has been detected in C18O giving a disk mass approximately 0.16 M (solar). Our HCO+ and HCN maps indicate significant chemical differentiation in the circumstellar region on small scales with HCO+ tracing an extended disk of material. The 12CO interferometer maps of the outflow show two conelike features originating at IRS 1, the blue one fanning open to the northeast and the red one to the southwest. The vertices of the cones are on either side of the circumstellar disk and have a projected opening angle of about 90 degrees. The intrinsic opening angle is in the range of 60 degrees-90 degrees which leads to significant interaction between outflow and infall.     

Homochirality as the signature of life: the SETH Cigar

A characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. It is therefore suggested that a search for extra-terrestrial life can be approached as a Search for Extra-Terrestrial Homochirality (SETH). A novel miniaturized space polarimeter, called the SETH Cigar, is described which could he used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. It is believed that homochirality will be found in the subsurface layers on Mars as a relic of extinct life.     

一次地震导致另一次地震

在本期(Nature,375卷,1995年5月18日)的221页上,Harris,Simpson和Reasenberg考察了南加州相邻地震间可能存在的联系。作者发现在一个大于等于5级地震震后的前18个月内,任一个邻近地区发生的后续大震(M≥5)几乎总是发生在一条被首震引起的静应力场变化所加载趋于破裂的断层上。如果是这样的话,它对于地震危险性评价意味着什么呢? 一次地震能够用一个弹性介质内的有限位错