Wave climate variability of Taiwan waters

Global sea surface wind field data derived from NCEP reanalysis were used in driving a SWAN wave model to reconstruct historical wave records from 1948 to 2008. The reconstructed wave data were compared and verified by the observation of the data buoys of the Central Weather Bureau and the Water Resources Agency, Taiwan, and the National Data Buoy Center/National Oceanic and Atmospheric Administration, United States. Over the past six decades, the wave climate in Taiwan waters has undergone considerable changes. The annual mean significant wave heights have reduced an average of 0.31 cm/year. Winter wave heights have gradually dropped 0.86 cm/year, which are related to the weakening of winter monsoons. Regarding the inter-annual wave climate variation, the influence of El Niño/southern oscillation was substantial; the wave heights increased in La Niña years and decreased in El Niño years. In the past 60 years, extreme wave events have been concentrated in two periods: 1967–1974 and 2000–2008. More severe extreme wave events occurred in the latter compared with the former, and all were induced by typhoons. A clear trend, in which the summer (winter) extreme wave events have increased (decreased) gradually, has been identified. The 1980s was the transition period. After the transition period, the annual occurrence of extreme wave events caused by typhoons exceeded those caused by an intense outbreak of winter cold surges, although the total number of the annual extreme wave events has not changed substantially.     

Simulation of unsteady oceanic cable deployment by direct integration with suppression

An improved algorithm is developed for predicting the transient response of a system of serially connected cables and bodies during unsteady deployment from a surface vessel. The governing equations of a cable-body system are derived with dependent variables of cable velocities, direction cosines and tension magnitude to form a nonlinear combined initial-value and boundary-value problem. The problem is then solved by introducing a stable Newmark-like implicit integration scheme in time and by a direct integration method with suppression of extraneous erroneous solutions. Special boundary conditions simulating actively controlled payout and slack-cable/ocean-bottom contact boundary conditions are included in the present model.     

Methodology of disaster risk assessment for debris flows in a river basin

“Disaster risk assessment” is important in the planning of risk management strategies that reduce societal losses. However, governmental agencies in Taiwan generally assess risks that emerge from debris flows without adequately considering risk management and taking a systems approach. This work proposes an approach to thoroughly consider the interactive influence mechanism of debris flow disaster risk. Additionally, a systematic method for assessing disaster risks is developed. This proposed method can be used in the current risk assessment and as a basis for management strategy planning. Based on systems thinking, the components and attributes of a conceptual system of disaster risk management associated with debris flows in a river basin are identified. Subsequently, a conceptual mitigation–hazard–exposure–resistance framework and an indicator system for assessing the debris flow disaster risks in a river basin are identified. The disaster risks for each exposed community in each drainage zone can be systematically calculated based on the current status or plans of prevention and evacuation measures using the proposed indicator system. A case study of implementing the proposed methodology that involves the Chishan River Basin is presented, in which disaster risk according to the current status of prevention and evacuation measures is assessed. Drainage zones and communities with a significant debris flow disaster risk are located; this risk is associated with a lack of adequate prevention and evacuation measures that have been planned of government agencies. Analytical results indicate that the proposed methodology can systematically and effectively assess the disaster risks of a river basin. The proposed methodology provides a valuable reference for governmental agencies that must manage disaster risk associated with debris flows.     

Mechanistic roles of soil humus and minerals in the sorption of nonionic organic compounds from aqueous and organic solutions

Mechanistic roles of soil humus and soil minerals and their contributions to soil sorption of nonionic organic compounds from aqueous and organic solutions are illustrated. Parathion and lindane are used as model solutes on two soils that differ greatly in their humic and mineral contents. In aqueous systems, observed sorptive characteristics suggest that solute partitioning into the soil-humic phase is the primary mechanism of soil uptake. By contrast, data obtained from organic solutions on dehydrated soil partitioning into humic phase and adsorption by soil minerals is influenced by the soil-moisture content and by the solvent medium from which the solute is sorbed.     

Inactivation Efficiency of Bioaerosols Using Carbon Nanotube Plasma

The purpose of this study was to inactivate indoor bioaerosols using carbon nanotube corona discharge plasma technology. Escherichia coli, Bacillus subtilis, and λ virus bioaerosols were generated using a Collison nebulizer. The effect of various factors, including the flow rate (30, 60, and 90 lpm) and the operating voltages (?1.5, ?3.0, ?4.5, ?6.0, and ?7.5 kV), on bioaerosol reduction was examined. The results indicated that the corona discharge using the carbon nanotube electrodes decreased the threshold voltage of plasma. The inactivation efficiencies of E. coli bioaerosols using the carbon nanotube corona discharge system at discharge voltages of ?1.5, ?3.0, ?4.5, ?6.0, and ?7.5 kV were 57, 61, 71, 93, and 97%, respectively. The corona discharge system using carbon nanotube electrodes had higher bioaerosol inactivation efficiency than the corona discharge system using stainless steel electrodes. The results further demonstrated that the inactivation efficiency decreased with an increasing flow rate. The inactivation efficiencies of E. coli, B. subtilis, and λ virus bioaerosols using carbon nanotube corona discharge plasma were 93, 88, and 81%, respectively.     

Ground motion evaluation procedures for performance-based design

The objective of performance-based earthquake engineering (PBEE) is the analysis of performance objectives with a specified annual probability of exceedance. Increasingly undesirable performance is caused by increasing levels of strong ground motion having decreasing annual probabilities of exceedance. Accordingly, the evaluation of ground motion intensity measures is a vital component of PBEE. This paper provides a brief synthesis of ground motion analysis procedures within a performance-based design framework, and is a summary of a recent report to which the reader is referred for details. The principal topics addressed are probabilistic characterizations of source, path, and site effects, with the discussion of these effects focusing principally on applications in active regions such as California.