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Considering the randomness of seismic input and the nonlinear characteristic of long-span structures, the probability density evolution method is used to study the dynamic response of the long-span steel-concrete composite structure under random earthquake. Three-dimensional structural model is established in the finite element software SAP2000, and then the displacements between layers and the response rule of vertical displacements of truss roof of the composite structure are obtained. The results show that under the input of three-dimensional earthquake, the vertical displacement of the grid roof of the isolated long-span steel-concrete composite structure is an order of magnitude larger than the horizontal direction of each layer. The probability density evolution method can offer comprehensive probability information of nodal displacements, and provide a reasonable way for the seismic reliability analysis of long-span isolated structures.

A fiber optic fluorescence biosensor for choline is introduced in this paper. Choline is an important neurotransmitter in mammals. Due to the growing needs for on-site clinical monitoring of the choline, much effect has been devoted to develop choline biosensors. Fiber-optic fluorescence biosensors have many advantages, including miniaturization, flexibility, and lack of electrical contact and interference. The choline fiber-optic biosensor we designed implemented a bifurcated fiber to perform fluorescence measurements. The light of the blue LED is coupled into one end of the fiber as excitation and the emission spectrum from sensing film is monitored by fiber-spectrometer (S2000, Ocean Optics) through the other end of the fiber. The sensing end of the fiber is coated with Nafion film dispersed with choline oxidase and oxygen sensitive luminescent Ru(II) complex (Tris(2,2'-bipyridyl)dichlororuthenium(II), hexahydrate). Choline oxidase catalyzes the oxidation of choline to betaine and hydrogen peroxide while consuming oxygen. The fluorescence intensity of oxygen- sensitive Ru(II) are related to the choline concentration. The response of the fiber-optic sensor in choline solution is represented and discussed. The result indicates a low-cost, high-performance, portable choline biosensor.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.