Dynamic response characteristics of seismic isolation systems for building structures

Isolation is an effective method of reducing effects of seismic events on building structures. Steel-reinforced elastomeric isolator (SREI) is one kind of isolation system which is used extensively, but there are some problems associated with its use, such as cost and weight. Fiber-reinforced elastomeric isolator (FREI) has been developed in an attempt to solve the problems of high cost and heavy weight for SREI. In this study, mechanical properties for the SREI and the FREI are investigated. Systematic dynamic response analyses are performed for three different models such as a fixed based, an SREI based and an FREI based low-story building structures. Two-dimensional and three-dimensional dynamic response analysis results for each model are compared in terms of displacement, drift, acceleration and shear force in this study. In the two-dimensional dynamic response analysis, the SREI and the FREI based structures are proven to be the more effective isolation systems against seismic events by comparing with the fixed based one. As a result, the FREI has shown better isolation performances than that of the SREI. Furthermore, to extract the characteristics of the FREI on building structure resisting the seismic effects, two models of three-dimensional framed structure with fixed bases and FREI isolated bases are built, respectively. After the dynamic response analysis of these two structures subjected to bi-directional ground motions, the analyzed results are compared with each other. It is shown that the FREI could effectively absorb the seismic energy, and decreases the destructive effects acting on a building structure due to ground horizontal motions that could occur in an earthquake. This paper was recommended for publication in revised form by Associate Editor Seockhyun Kim Beom-Soo Kang received his B.S. in Mechanical Engineering from Pusan National University in 1981 and his M.S. in Aerospace Engineering from KAIST in 1983, Korea, respectively. He then received his Ph.D. from the University of California at Berkeley, USA, in 1990. Dr. Kang is currently a Professor at the Department of Aerospace Engineering at Pusan National University in Busan, Korea. His research interests include seismic isolation, materials processing, FEM and flexible forming technology. Tae-Wan Ku received his B.S., M.S. and Ph.D. in Aerospace Engineering from Pusan National University, Korea, in 1997, 1999 and 2003, respectively. Dr. Ku is currently a research professor at the Department of Aerospace Engineering at Pusan National University in Busan, Korea. His research interests include multi-stage deep drawing, flexible forming technology, and forming limit surface theory.     

Anchoring of Chiral Manganese(III) Salen Complex onto Organo Clay and Porous Clay Heterostructure and Catalytic Activity in Alkene Epoxidation

The chiral Mn(III) salen complex (C1) was immobilised onto a natural clay (BEN) and a porous clay heterostructure (PCH) functionalised with 3-aminopropyltriethoxysilane (APTES). FTIR, XPS and Mn chemical analysis confirm the C1 anchorage in both materials, but with higher efficiency in BEN_APTES clay. The catalytic activity of C1@BEN_APTES and C1@PCH_APTES, was assessed in the epoxidation of styrene (sty) and ∝-methylstyrene (∝-Mesty) using NaOCl and m-chloroperoxybenzoic acid (m-CPBA)/N-methylmorpholine-N-oxide (NMO). Both materials behave as moderate catalysts, show high epoxide selectivity but low enantiomeric excesses. In the case of sty epoxidation with m-CBPA/NMO the C1@PCH_APTES catalyst showed the highest catalytic activity, whereas in ∝-Mesty epoxidation, the C1@PCH_APTES catalyst, although leading to lower substrate conversion than the BEN analogue, presented the lowest complex leaching. In all cases, the oxidant NaOCl had some destructive effect in the hybrid catalysts, highlighting the importance of a careful choice of catalyst and oxidant system.     

Comparison of Kayzero for Windows and k0-IAEA software packages for k0 standardization in neutron activation analysis

For many years the well-established Kayzero for Windows software for neutron activation analysis (NAA) using k₀ standardization was the only commercial program available. Recently, the freeware k0-IAEA software has been launched by the International Atomic Energy Agency (IAEA). The software is based on an adapted Høgdahl convention in which the cadmium cut-off energy from the k₀-formulas is removed. The holistic approach of γ-ray spectra evaluation is used which minimizes the user's interaction with the software.Several certified reference materials were analyzed with the k0-IAEA and Kayzero for Windows software using the same gamma-ray spectra obtained from several irradiation and counting modes. The results obtained were compared and evaluated in terms of precision, accuracy and detection limits. The work-flow procedures performed by the two software packages and the results obtained are discussed.     

A novel design of solid-state NaBH4 composite as a hydrogen source for 2 W PEMFC applications

Hydrolysis of sodium borohydride (NaBH₄) is a promising method for on-board hydrogen supply to polymer electrolyte membrane fuel cells (PEMFC). This article presents an attempt to design a novel solid-state NaBH₄ composite, which is made up of NaBH₄ powder, Co²⁺/IR-120 catalyst and silicone rubber, for hydrogen generator. The silicone rubber can act as a stabilizer in the solid-state NaBH₄ composite because of its surface hydrophobicity leading to reduced diffusion rate of water into the composite. The solid-state NaBH₄ composite can produce hydrogen stably near 25 mL min⁻¹ for at least 2 h without employment of any mechanical control system. Using the hydrogen generated from the solid-state NaBH₄ composite, a 2 W PEMFC stack is successfully operated to power a cellular phone.     

Mechanical properties and durability of PMMA impregnated mortar

Polymer impregnated concrete (PIC) is known to exhibit better strength and durability characteristics than the other classes of polymer cement composites. In the work described herein the monomer was impregnated into cement mortar and polymerized by two methods — the conventional thermal method and using microwaves. The mechanical properties and durability characteristics of the samples and on exposure to chemical environments were then evaluated. The above studies revealed that the strengths of PIC specimens were almost 2–3 times better than those of conventional cement mortars. The chemical resistance was also found to be superior even on prolonged exposure to the chemical media. This may be attributed to the protective layer formed by the polymer on the cement mortar, which prevents the external chemical media from interacting with the cement particles. The properties of the PIC specimens prepared by both methods have also been compared and discussed in this paper.     

Fictitious domain formulations of unilateral problems: analysis and algorithms

The present article deals with fictitious domain methods for numerical realization of scalar variational inequalities with the Signorini type conditions on the boundary. Two variants are introduced and analyzed. A discretization is done by finite elements. It leads to a system of non-smooth, piecewise linear equations. This system is solved by the semismooth Newton method. Numerical experiments confirm the efficiency of this approach.     

Luminescent and structural properties of Yb-doped Al2O3 nanopowders

In this work, we discuss structural and luminescent properties of Al₂O₃ nanopowders doped with Yb³⁺ ions prepared by a novel method, in which organic compounds were used as a solvent and lanthanide organic derivatives, served as a rare-earth ion source. The set of samples differing in activator concentrations and particle sizes was carefully studied by means of structural and optical characterization methods. In particular, the high resolution electron and transmission microscopy has been deployed together with X-ray diffraction technique to determine fundamental structural properties of nanopowders. The optical characterization was focused mainly on basic excitation and emission features and their sensitiveness on dopant concentration and the average nanoparticle size.     

Multiple small-angle scattering of light

A way of desribing multiple small angle scattering of light is by a modification of the Fokker-planck equation. While for non-relativistic particles fundamental solutions of the analogous equation are well known, their extension to light scattering appears difficult, except in the case with no space dependence.     

The results of the brain computer tomography and clinical picture in acute cholinesterase inhibitors poisoning

The aim of this study was to evaluate a morphological and functional status of the CNS in acute cholinesterase inhibitors (ChI) poisonings using the brain computer tomography (CT) and complex psychiatric examination. Under examination there were 59 cholinesterase inhibitors orally poisoned patients, treated at the Department of Clinical Toxicology in years 1984-1997, aged from 14 to 68 (mean 34.7 +/- 12.8) years. The examined group comprised 9 women (15.3%) and 50 men (84.7%). Between the 3rd and 7th day of hospitalisation a complex psychiatric examination was performed. The CNS damage was diagnosed when the point score from complex psychiatric examination was minimum 5 points. CT was performed between the 3rd and 10th day after the intoxication. Incorrect CT scans were found in 78% of poisoned patients. The most common lesion was generalised cortex atrophy and subcortex atrophy of the brain (73.9%), followed by isolated cortex (17.4%) and subcortex atrophy with simultaneous areas of low density in the subcortical nuclei (8.7%). The frequency of incorrect CT scans was statistically higher (p < 0.01) in the group of organophosphorous compounds poisoned patients compared to those poisoned with carbamates. The complex psychiatric examination revealed in 24 patients (40.7%) the differently intensified alterations, but the point score was not higher than 4. Unquestionable damage of the CNS was recognised in 34 patients (57.6%) of the ChI poisoned patients. The frequency of CNS changes detected in complex psychiatric examination was statistically higher (p < 0.01) in the group of the severely poisoned patients. The significantly higher frequency of pathological changes revealed by the brain CT was found in the group of patients with higher than 5 point score obtained from the complex psychiatric evaluation compared to those with score lower than 5 (p < 0.001).