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Responses of a cantilever retaining wall under multiple earthquake sequences
No full textThe seismic behaviors of retaining walls were evaluated considering only a single earthquake. However, aftershock or foreshock ground motions can occasionally be as strong as mainshock ground motions and can aggravate damage to structures. This study investigated the seismic responses of a cantilever retaining wall under earthquake sequences by performing a series of finite-difference-based numerical simulations. We collected a suite of mainshock-aftershock and foreshock-mainshock sequential ground motions, which were used as the input ground motions in the numerical simulations. This study focused on revealing the differences in wall responses under a single earthquake and multiple earthquake sequences, considering a wide range of ground motion intensities. The relative wall movements caused by mainshock-aftershock and foreshock-mainshock sequential ground motions can be much larger than those caused by a single mainshock motion. In addition, the sequence itself had the effect of increasing the relative wall movements under strong sequential ground motions. However, the effects of the aftershock and foreshock motions on the wall responses were insignificant under weak sequential ground motions
Experimental investigation of heat transfer limitations in concentric annular sodium heat pipes and thermosyphon
No full textThis paper presents experimental investigations on the heat transfer performance of concentric annular heat pipe (CAHP) and thermosyphon (CATP) using sodium as a working fluid for microreactor applications. CAHP characterized by wicks on the inner and outer walls offers the potential to enhance capillary force and enable more compact microreactor designs. The research aims to understand the implications of structural differences between CAHP, CATP and conventional heat pipe (CHP) and identify favorable conditions for their use in microreactors. The thermal behavior and heat transfer limits of CAHP and CATP were examined under various boundary conditions. The experimental results revealed that CAHP exhibited capillary limits approximately 71.2% higher than cylindrical heat pipes under horizontal conditions. However, the Chi model used for predicting capillary limits showed a difference about 19.7% in horizontal operation and exceeded 44.6% in vertical operation, highlighting the need for considering the effect of non-uniform capillary forces in CAHP. The presence of additional inner wick in CAHP provided large evaporation areas, which facilitated rapid vapor generation and enabled the development of a continuum flow faster than in CHP, by approximately 70 degrees C. However, in vertical operation, CATP necessitates higher heat fluxes and exhibits notable temperature disparities between the evaporator and condenser regions compared to CAHP. This difference can be explained depend on the vapor generation mechanisms: heat pipes utilize additional wick area to facilitate evaporation, while thermosyphon depend on boiling that the advantages related to the annular flow path in CATP are not clear. Furthermore, the presence of an adiabatic section yields contrasting effects: while it promotes the formation of larger menisci in heat pipes, its presence is unfavorable in thermosyphons as it can elevate boiling temperatures that delayed operations. The findings underscore the advantages of CAHP over CHP, particularly in microreactor applications, provide insights into design optimizations for compact microreactors, and showed gaps in operating prediction models and experimental results
Isotopic investigation of sources and processes affecting gaseous and particulate bound mercury in the east coast, South Korea
No full textUnderstanding sources and processes affecting atmospheric mercury (Hg) are key to enabling targeted Hg manage-ments under the Minamata Convention on Mercury. We employed stable isotopes (& delta;202Hg, & UDelta;199Hg, & UDelta;201Hg, & UDelta;200Hg, & UDelta;204Hg) and backward air trajectories to characterize sources and processes affecting total gaseous Hg (TGM) and par-ticulate bound Hg (PBM) in a coastal city, South Korea, subjected to atmospheric Hg sources of a local steel manufacturing industry, coastal evasion from the East Sea, and long-distance transport from East Asian countries. Based on the simulated airmasses and the isotopic comparison with TGM characterized from other urban, remote, and coastal sites, TGM evaded from the coastal surface of the East Sea (warm seasons) and from the land surface in high latitude regions (cold seasons) act as important sources relative to local anthropogenic emissions at our study lo-cation. Conversely, a significant relationship between & UDelta;199Hg and concentrations of PBM (r2 = 0.39, p < 0.05) and a seasonally uniform & UDelta;199Hg/& UDelta;201Hg slope (1.15), except for summer (0.26), suggest that PBM is generally sourced from local anthropogenic emissions and subjected to Hg2+ photo-reduction on particles. The striking isotopic similarity be-tween our PBM (& delta;202Hg; -0.86 to 0.49 %o, & UDelta;199Hg; -0.15 to 1.10 %o) and those previously characterized along the coastal and offshore regions of the Northwest Pacific (& delta;202Hg; -0.78 to 1.1 %o, & UDelta;199Hg; -0.22 to 0.47 %o) infer that anthropogenically emitted PBM from East Asia and those processed in the coastal atmosphere serves as a regional iso-topic end-member. The implementation of air pollution control devices can reduce local PBM, while regional and/or multilateral efforts are required to manage TGM evasion and transport. We also anticipate that the regional isotopic end-member can be used to quantify the relative influence of local anthropogenic Hg emissions and complex processes affecting PBM in East Asia and other coastal regions
Control of cavitation in Venturi using hemispherical bump
No full textIn this study, we investigated how the performance of a Venturi changes when a hemispherical bump is applied to the divergent part of the Venturi tube and what causes the performance difference. The Venturi-tunnel experiment was conducted in the Reynolds number range of 0.2 ?? 105 - 1.2 ?? 105 and cavitation number range of 0.9 - 10. The bump was found to reduce the pressure loss coefficient and increase the discharge coefficient by shortening the cavitation length. The decrease in the cavitation length by the bump was explained by the strengthening of the re-entrant jet. The wake generated from the hemispherical bump seems to increase the adverse pressure gradient on the Venturi surface, thereby strengthening the re-entrant jet
Staphylococcus aureus Sensitivity to Membrane Disrupting Antibacterials Is Increased under Microgravity
No full textIn a survey of the International Space Station (ISS), the most common pathogenic bacterium identified in samples from the air, water and surfaces was Staphylococcus aureus. While growth under microgravity is known to cause physiological changes in microbial pathogens, including shifts in antibacterial sensitivity, its impact on S. aureus is not well understood. Using high-aspect ratio vessels (HARVs) to generate simulated microgravity (SMG) conditions in the lab, we found S. aureus lipid profiles are altered significantly, with a higher presence of branch-chained fatty acids (BCFAs) (14.8% to 35.4%) with a concomitant reduction (41.3% to 31.4%) in straight-chain fatty acids (SCFAs) under SMG. This shift significantly increased the sensitivity of this pathogen to daptomycin, a membrane-acting antibiotic, leading to 12.1-fold better killing under SMG. Comparative assays with two additional compounds, i.e., SDS and violacein, confirmed S. aureus is more susceptible to membrane-disrupting agents, with 0.04% SDS and 0.6 mg/L violacein resulting in 22.9- and 12.8-fold better killing in SMG than normal gravity, respectively. As humankind seeks to establish permanent colonies in space, these results demonstrate the increased potency of membrane-active antibacterials to control the presence and spread of S. aureus, and potentially other pathogens
Free-breathing high isotropic resolution quantitative susceptibility mapping (QSM) of liver using 3D multi-echo UTE cones acquisition and respiratory motion-resolved image reconstruction
No full textPurpose: To enable free-breathing and high isotropic resolution liver quantitative susceptibility mapping (QSM) using 3D multi-echo UTE cones acquisition and respiratory motion-resolved image reconstruction. Methods: Using 3D multi-echo UTE cones MRI, a respiratory motion was estimated from the k-space center of the imaging data. After sorting the k-space data with estimated motion, respiratory motion state-resolved reconstruction was performed for multi-echo data followed by nonlinear least-squares fitting for proton density fat fraction (PDFF), R-2*, and fat-corrected B-0 field maps. PDFF and B-0 field maps were subsequently used for QSM reconstruction. The proposed method was compared with motion-averaged (gridding) reconstruction and conventional 3D multi-echo Cartesian MRI in moving gadolinium phantom and in vivo studies. Region of interest (ROI)-based linear regression analysis was performed on these methods to investigate correlations between gadolinium concentration and QSM in the phantom study and between R-2* and QSM in in vivo study. Results: Cones with motion-resolved reconstruction showed sharper image quality compared to motion-averaged reconstruction with a substantial reduction of motion artifacts in both moving phantom and in vivo studies. For ROI-based linear regression analysis of the phantom study, susceptibility values from cones with motion-resolved reconstruction (QSM(ppm) = 0.31 x gadolinium(mM)+ 0.05, R-2 = 0.999) and Cartesian without motion (QSM(ppm) = 0.32 x gadolinium(mM)+ 0.04, R-2 = 1.000) showed linear relationships with gadolinium concentrations and showed good agreement with each other. For in vivo, motion-resolved reconstruction showed higher goodness of fit (QSM(ppm) = 0.00261 x R-2*(s-1) - 0.524, R-2 = 0.977) compared to motion-averaged reconstruction (QSM(ppm) = 0.0021 x R-2*(s-1) - 0.572, R-2= 0.723) in ROI-based linear regression analysis between R-2* and QSM
Butyl acrylate/TiO2-copolymer hybrid one-dimensional photonic crystal-based colorimetric sensor for detection of C-6-C-16 n-alkanes of kerosene in adulterated diesel
No full textDiesel fuel, which is widely used in engines, generators, and industrial equipment, is often adulterated with kerosene. The use of adulterated diesel fuel reduces the performance and durability of diesel-fuel-powered engines, causes environmental pollution, and promotes tax evasion. However, detecting kerosene in diesel using a high-precision instrumental technique such as gas chromatography with flame ionization detection is difficult because both diesel and kerosene contain C-6-C-16 paraffins. In this study, we developed a simple and reliable colorimetric sensor to detect various volumetric fractions of kerosene in diesel. A novel 15-layered one-dimensional photonic crystal (1D PC) was prepared using a photo-crosslinked butyl acrylate (BA)-based copolymer [P(BA-co-BPA)] as the low-refractive-index material and a photo-crosslinked copolymer-TiO2 hybrid (Ti70) as the high-refractive-index material. The P(BA-co-BPA) layers swelled to a greater extent in smaller-sized C-6-C-16 n-alkanes than in the larger ones. Consequently, the reflection colors of P(BA-co-BPA)/Ti70 PC underwent a greater red shift from the sky-blue color of the pristine state as the swelling increased from the C-16 to the C-6 n-alkanes. When immersed in pure diesel, the 1D PC exhibited a green color, which underwent a greater red shift as the volume fraction of kerosene increased from 10% (similar to limit of colorimetric detection) to 100% in the kerosene + diesel mixtures. The 1D PC reached saturation within 45 min and changed color from the sky-blue corresponding to the pristine state to greenish yellow, yellow, yellow-orange, orange, and reddish orange in 10%, 20%, 30%, 50-70%, and 100% kerosene, respectively. Moreover, it exhibited recyclability in five swelling/deswelling cycles in diesel and kerosene. We expect that these findings will promote the development of simple and state-of-the-art 1D PC sensors
Expansion and optimization of ammonia import to the Republic of Korea for electricity generation
No full textAmmonia is considered a promising energy source for achieving carbon neutrality because it is carbon-free. This study aims to evaluate the feasibility of ammonia-based power generation by conducting techno-economic and carbon footprint analyses of an integrated ammonia decomposition and phosphoric acid fuel cell system. Using a commercial process simulator, the power generation process is designed to reveal an energy efficiency of 46.7% and an upper limit for the ammonia price to compete with industrial electricity prices is identified as 421.3 $ tNH3-1 through economic analysis. Furthermore, the study establishes five different scenarios for ammonia import from the top ten exporting countries to the Republic of Korea (KOR), according to historical data, for optimi-zation. Ammonia import is optimized in terms of exporting countries and quantities to satisfy the ammonia price while minimizing overall emissions using the Monte Carlo method for ammonia production costs and carbon dioxide emissions in each nation. The results show that carbon intensity falls within the range of 0.707-0.736 kgCO2-eq kWh-1, which exceeds the 20-year average value of carbon intensity in KOR if carbon-based ammonia is solely imported. However, the system can be competitive in terms of both economic and environmental aspects if the carbon-neutral ammonia ratio is over 78% (more than Scenario 4). In conclusion, this study statistically investigates the optimization results focusing on major ammonia export countries, identifies the trend of carbon intensity in the scenarios, and provides guidelines for reducing overall carbon intensity by considering the production, transportation, and utilization of ammonia
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No full textKorean fir (Abies koreana Wilson) is one of the most important environmental indicator tree species for assessing climate change impacts on coniferous forests in the Korean Peninsula. However, due to the nature of alpine and subalpine regions, it is difficult to conduct regular field surveys of Korean fir, which is mainly distributed in regions with altitudes greater than 1,000 m. Therefore, this study analyzed the vegetation change trend of Korean fir using regularly observed remote sensing data. Specifically, normalized difference vegetation index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS), land surface temperature (LST), and precipitation data from Global Precipitation Measurement (GPM) Integrated Multi-satellitE Retrievalsfor GPM from September 2003 to 2020 for Hallasan and Jirisan were used to analyze vegetation changes and their association with environmental variables. We identified a decrease in NDVI in 2020 compared to 2003 for both sites. Based on the NDVI difference maps, areas for healthy vegetation and high mortality of Korean fir were selected. Long-term NDVI time-series analysis demonstrated that both Hallasan and Jirisan had a decrease in NDVI at the high mortality areas (Hallasan: -0.46, Jirisan: -0.43). Furthermore, when analyzing the long-term fluctuations of Korean fir vegetation through the Hodrick-Prescott filter-applied NDVI, LST, and precipitation, the NDVI difference between the Korean fir healthy vegetation and high mortality sitesincreased with the increasing LST and decreasing precipitation in Hallasan. Thissuggests that the increase in LST and the decrease in precipitation contribute to the decline of Korean fir in Hallasan. In contrast, Jirisan confirmed a long-term trend of declining NDVI in the areas of Korean fir mortality but did not find a significant correlation between the changes in NDVI and environmental variables (LST and precipitation). Further analyses of environmental factors, such as soil moisture, insolation, and wind that have been identified to be related to Korean fir habitats in previous studies should be conducted. This study demonstrated the feasibility of using satellite data for long-term monitoring of Korean fir ecosystems and investigating their changes in conjunction with environmental conditions. Thisstudy provided the potential forsatellite-based monitoring to improve our understanding of the ecology of Korean fir
British ???Guilt??? Concerning Anglo-New Zealand Relations and the Migration of Former IRA Detainees, 1970-1977
No full textThis article examines how Britain???s deteriorating relations with New Zealand in the early 1970s rendered the London government to accommodate the Wellington administration???s foreign policy decisions at the risk of exposing Britain???s contentious internal policy arrangements to the wider world. Britain???s decision in the late 1960s and early 1970s to withdraw her troops from Southeast Asia and to join the European Economic Community had a negative impact on her diplomatic relations with various Commonwealth partners, including her traditionally strong bond with New Zealand. This was evident in the increasing anti-British sentiment amongst the people of New Zealand and in the introduction of anti-British policies by the Wellington government in the early 1970s. Consequently, Britain actively sought to placate New Zealand???s feelings and to improve Anglo-New Zealand relations by agreeing to accommodate New Zealand Prime Minister Robert Muldoon???s policy of allowing former IRA detainees in Northern Ireland to emigrate to New Zealand, even though this meant that Britain???s controversial detention policy in Northern Ireland could be laid bare to global scrutiny. London???s high-risk decision to give unofficial advice to Wellington on the suitability of candidates for emigration had to be concealed in order to give the impression that the British government was not in any way involved in New Zealand???s decisions. Therefore, when questions were raised in the British Parliament over the question of London???s involvement in Muldoon???s scheme, the British government went so far as to mislead the Commons on the issue.
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