Seismic resilience timber connection—adoption of shape memory alloy tubes as dowels

This study investigates a novel timber dowel-type connection system using superelastic shape memory alloy (SMA) bar and tubes as dowels, in order to provide self-centering effect. Double-shear connections with SMA and mild steel dowels were tested under dynamic loadings at different displacement levels. The results showed that SMA dowel-type connections have good self-centering behaviours and can mitigate the residual deformation effectively compared with steel dowel-type connections after excessive deformation; although the steel dowel-type connections present higher strength. These tests reveal that the connection with tube dowels show higher equivalent viscous damping ratio than those use solid bar as tube would allow larger deformation to dissipate energy. To demonstrate application of the benefit of this system, an analytical model of a 3-storey timber framed structure was built for parametric study. The results showed that the structures with conventional dowel-type type connections exhibit large unrecoverable deformation after timber framed structures experience an earthquake. In comparison, those with the connections developed in this project show limited unrecoverable deformation due to the self-centering capacity of the connections

Microbial communities associated with anaerobic degradation of polybrominated diphenyl ethers in river sediment

AbstractBackground/purposePolybrominated diphenyl ethers (PBDEs) are extensively used as a class of flame retardants and have become ubiquitous environmental pollutants. We aimed to uncover the changes in microbial community with PBDE anaerobic degradation with and without zero-valent iron in sediment from the Erren River, considered one of the most heavily contaminated rivers in Taiwan.MethodsPBDE anaerobic degradation in sediment was analyzed by gas chromatography with an electron capture detector. Microbial community composition was analyzed by a pyrosequencing-based metagenomic approach.ResultsThe anaerobic degradation rate of BDE-209 was higher than BDE-28 in sediment; the addition of zero-valent iron enhanced the degradation rates of both. In total, 19 known bacterial genera (4 major genera: Clostridium, Lysinibacillus, Rummeliibacillus, and Brevundimonas) were considered PBDE degradation-associated bacteria (sequence frequency negatively correlated with PBDE remaining percentage) as were four known archaea genera (Methanobacterium, Methanosarcina, Methanocorpusculum, and Halalkalicoccus; sequence frequency positively correlated with PBDE remaining percentage).ConclusionThe composition of bacteria and that of archaea affected the anaerobic degradation of BDE-28 and BDE-209. The addition of zero-valent iron further decreased the archaea content to undetectable levels

Matrix Formulation of Hamiltonian Structures of Constrained KP Hierarchy

We give a matrix formulation of the Hamiltonian structures of constrained KP hierarchy. First, we derive from the matrix formulation the Hamiltonian structure of the one-constraint KP hierarchy, which was originally obtained by Oevel and Strampp. We then generalize the derivation to the multi-constraint case and show that the resulting bracket is actually the second Gelfand-Dickey bracket associated with the corresponding Lax operator. The matrix formulation of the Hamiltonian structure of the one-constraint KP hierarchy in the form introduced in the study of matrix model is also discussedComment: 19 pages, Revtex, no figures. Minor changes, reference correcte

Modelling the Asymmetric Volatility in Hog Prices in Taiwan: The Impact of Joining the WTO

The hog industry, where prices are determined according to an auction system, is of vital importance to the agricultural industry in Taiwan by providing significant production and employment. In particular, there were significant impacts on daily hog prices in the periods before, during and after joining the WTO, which we will refer to as periods of anticipation, adjustment and settlement. The purpose of the paper is to model the growth rates and volatility in daily hog prices in Taiwan from 23 March 1999 to 30 June 2007, which enables an analysis of the effects of joining the WTO. The paper provides a novel application of financial volatility models to agricultural finance. The empirical results have significant implications for risk management and policy considerations in the agricultural industry in Taiwan, especially when significant structural changes, such as joining the WTO, are concerned. The three sub-samples relating to the period before, during and after joining the WTO display significantly different volatility persistence, namely symmetry, asymmetry but not leverage, and leverage, respectively, whereby negative shocks increase volatility but positive shocks of a similar magnitude decrease volatility.Hog prices, joining the WTO, conditional volatility models, asymmetry, leverage, moment conditions.

Modelling the Asymmetric Volatility in Hog Prices in Taiwan: The Impact of Joining the WTO

Prices in the hog industry in Taiwan are determined according to an auction system. There are significant differences in hog prices before, during and after joining the World Trade Organization (WTO). The paper models growth rates and volatility in daily hog prices in Taiwan from 23 March 1999 to 30 June 2007, which enables an analysis of the effects of joining the WTO. The empirical results have significant implications for risk management and policy in the agricultural industry. The three sub-samples for the periods before, during and after joining the WTO display significantly different volatility persistence of symmetry, asymmetry and leverage, respectively.Hog prices; joining the WTO; conditional volatility models; asymmetry; leverage; moment conditions