• Wind and Structures
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• v.34 no.1
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• pp.115-125
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• 2022

The high-Reynolds number flow around a rectangular cylinder, having streamwise to crossflow length ratio equal to 5 is analyzed in the present paper. The flow is characterized by shear-layer separation from the upstream edges. Vortical structures of different size form from the roll-up of these shear layers, move downstream and interact with the classical vortex shedding further downstream in the wake. The corresponding mean flow is characterized by a recirculation region along the lateral surface of the cylinder, ending by mean flow reattachment close to the trailing edge. The mean flow features on the cylinder side have been shown to be highly sensitive to set-up parameters both in numerical simulations and in experiments. The results of 21 Large Eddy Simulations (LES) are analyzed herein to highlight the impact of the lateral mean recirculation characteristics on the near-wake flow features and on some bulk quantities. The considered simulations have been carried out at Reynolds number Re=DU_∞/ν=40 000, being D the crossflow dimension, U_∞ the freestream velocity and ν the kinematic viscosity of air; the flow is set to have zero angle of attack. Some simulations are carried out with sharp edges (Mariotti et al. 2017), others with different values of the rounding of the upstream edges (Rocchio et al. 2020) and an additional LES is carried out to match the value of the roundness of the upstream edges in the experiments in Pasqualetto et al. (2022). The dimensions of the mean recirculation zone vary considerably in these simulations, allowing us to single out meaningful trends. The streamwise length of the lateral mean recirculation and the streamwise distance from the upstream edge of its center are the parameters controlling the considered quantities. The wake width increases linearly with these parameters, while the vortex-shedding non-dimensional frequency shows a linear decrease. The drag coefficient also linearly decreases with increasing the recirculation length and this is due to a reduction of the suctions on the base. However, the overall variation of C_D is small. Finally, a significant, and once again linear, increase of the fluctuations of the lift coefficient is found for increasing the mean recirculation streamwise length.

• Composites Research
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• v.36 no.1
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• pp.37-41
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• 2023

The treated water inside the ballast electrolytic cell creates a highly alkaline atmosphere due to hydroxide generated at the DSA(Dimension Stable Anode) electrode during electrolysis. In this study, a composite material that can replace the weakness of the PE-coated steel pipe used in the existing ballast pipe was prepared. The test samples are BRE(Basalt fiber reinforced epoxy), BRP(Basalt fiber reinforced unsaturated polyester), GRE(Glass fiber reinforced epoxy), and GRP(Glass fiber reinforced unsaturated polyester). And then it was immersed in NaOH for 720 hours. The friction test of each specimen was conducted. The Friction coefficient analysis according to material friction depth and interfacial adhesion behavior between resin and fiber were analyzed. As a result, the mechanism of interfacial separation between resin and fiber could be analyzed. In the case of the unsaturated polyester resin with low interfacial bonding strength the longer the immersion time in the alkaline solution, the faster the internal deterioration caused by the deterioration that started from the surface, resulting in a decrease in the friction coefficient. It is hoped that this study will help to understand the degradation behavior of composite materials immersed in various chemical solutions such as NaOH, acid, and sodium hypochlorite in the future.

• Journal of the Korean Chemical Society
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• v.37 no.9
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• pp.820-825
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• 1993

The ion exchange capacity of HDBPDA ion exchanger, {(4,5) : (13,14)-dibenzo-6,9,12-trioxa-3,15,21-triazabicyclo[15.3.l]heneicosa-(1,17,19)(18,20,21) triene ion exchanger: HDBPDA ion exchanger} was 3.8 meq/g. The distribution coefficients of alkali and alkaline earth metal ions in water and the various concentration of hydrochloric acid were determined. Concentration of hydrochloric acid have almost not influenced on the distribution coefficients of alkali and alkaline earth metal ions, but generally, the distribution coefficient was slightly increased with decrease of concentration of hydrochloric acid. The distribution coefficients of metal ions in water are larger than those of various hydrochloric acid concentrations. Also, alkali and alkaline earth metal ions are separated by column ion exchange chromatography using HDBPDA ion exchange with water as eluent. The distribution coefficents of alkali and alkaline earth metal ions were increased with increase of ionic radii of metal ions.

• Wind and Structures
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• v.13 no.1
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• pp.57-82
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• 2010

The 486m-long roof of Shenzhen Citizens Centre is one of the world's longest spatial lattice roof structures. A comprehensive numerical study of wind effects on the long-span structure is presented in this paper. The discretizing and synthesizing of random flow generation technique (DSRFG) recently proposed by two of the authors (Huang and Li 2008) was adopted to produce a spatially correlated turbulent inflow field for the simulation study. The distributions and characteristics of wind loads on the roof were numerically evaluated by Computational Fluid Dynamics (CFD) methods, in which Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes Equations (RANS) Model were employed. The main objective of this study is to explore a useful approach for estimations of wind effects on complex curved roof by CFD techniques. In parallel with the numerical investigation, simultaneous pressure measurements on the entire roof were made in a boundary layer wind tunnel to determine mean, fluctuating and peak pressure coefficient distributions, and spectra, spatial correlation coefficients and probability characteristics of pressure fluctuations. Numerical results were then compared with these experimentally determined data for validating the numerical methods. The comparative study demonstrated that the LES integrated with the DSRFG technique could provide satisfactory prediction of wind effects on the long-span roof with complex shape, especially on separation zones along leading eaves where the worst negative wind-induced pressures commonly occur. The recommended LES and inflow turbulence generation technique as well as associated numerical treatments are useful for structural engineers to assess wind effects on a long-span roof at its design stage.

• Asian-Australasian Journal of Animal Sciences
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• v.13 no.6
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• pp.861-882
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• 2000

The seed, or grain, of modern cultivars of Lupinus angustifolius, commonly known as Australian sweet lupins (ASL), is an established feed resource for the intensive animal industries of Australia, Japan, Korea and several other countries in Asia and Europe. Since the introduction of ASL to the world marketplace about 25 years ago, researchers in many countries have found them to be a valuable component of the diet of beef and dairy cattle, sheep, pigs, poultry, finfish and crustaceans. The seed of ASL contains ~32% crude protein (CP) (~35% DM basis) and 5% oil. The main storage carbohydrates in the seed are the ${\beta}$-galactans that comprise most of the cell-wall material of the kernel and the cellulose and hemicellulose of the thick seed coats. ASL seeds contain about 40% non-starch polysaccharides (NSP) and a negligible amount of starch. This makes them an excellent ingredient for ruminant diets, as the risk of acidosis is very low. The seed of modern cultivars of domesticated Lupinus species contain negligible amounts of lectins and trypsin inhibitors so they do not require preheating before being used as an ingredient in feeds for monogastric species. They have a high digestibility coefficient for protein, >90% for most species, but a low energy digestibility, ~60%, which is mostly due to the high content of NSP. The low content of methionine (0.22%) and of lysine (1.46%) is typical of the legumes. The lysine availability for pigs is >70%. Lupin kernels contain ~39% CP (~42% DM basis), 6% oil and 30% NSP. They have a higher digestible energy for pigs and finfish and a higher metabolisable energy for poultry than whole seed. Commercial operations rarely achieve complete separation of kernel from hull and it is more likely that the kernel fraction, called splits or meats, will contain ~36% CP. The replacement of soybean meal or peas with ASL in cereal-based diets for most intensively reared animals, birds and fish is possible provided lysine, methionine and digestible energy levels are kept constant. This makes ASL economically competitive in many, but not all, circumstances.

• Earthquakes and Structures
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• v.12 no.3
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• pp.333-347
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• 2017

Masonry infill walls are unavoidable parts of any building to create a separation between internal space and external environment. In general, there are some prevalent openings in the infill wall due to functional needs, architectural considerations or aesthetic concerns. In current design practice, the strength and stiffness contribution of infill walls is not considered. However, the presence of infill walls may decisively influence the seismic response of structures subjected to earthquake loads and cause a different behavior from that predicted for a bare frame. Furthermore, partial openings in the masonry infill wall are significant parameter affecting the seismic behavior of infilled frames thereby decreasing the lateral stiffness and strength. The possible effects of openings in the infill wall on seismic behavior of RC frames is analytically studied by means of pushover analysis of several bare, partially and fully infilled frames having different bay and story numbers. The stiffness loss due to partial opening is introduced by the stiffness reduction factors which are developed from finite element analysis of frames considering frame-infill interaction. Pushover curves of frames are plotted and the maximum base shear forces, the yield displacement, the yield base shear force coefficient, the displacement demand, interstory drift ratios and the distribution of story shear forces are determined. The comparison of parameters both in terms of seismic demand and capacity indicates that partial openings decisively influences the nonlinear behavior of RC frames and cause a different behavior from that predicted for a bare frame or fully infilled frame.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.312-321
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• 2015

Objectives: The purpose of this study was to determine the best method to analyze PAHs at extremely low concentrations. To this end, 16 PAHswere analyzed simultaneously by GC/MS, HPLC/FLD and HPLC/UVD, and the analytical characteristics of HPLC and GC/MS were compared. Methods: This study was conducted by GC/MS and HPLC/FLD/UVD, and evaluated linearity, precision and detection limit. Standard solutions were prepared for 21 samples in the range of $0.00001{\sim}1.0{\mu}g/mL$ and the samples were divided into four groups. All samples were made in three sets and analysis was replicated seven times. Results: Sixteen PAHs could be simultaneously separated by HPLC and GC/MS, and the adequate equipment was HPLC/FLD. The retention times by HPLC were shorter than GC/MS, and HPLC had better separation for most PAHs than GC/MS. The peaks of naphthalene and naphthalene-D8 partially overlapped for GC/MS. HPLC/FLD had a 20-2000 times lower limit of detection than GC/MS and UVD. However FLD was not adequate for analyzing acenaphthylene because it has too low a fluorescence quantum yield to be detected. The precision of HPLC/FLD/UVD and GC/MS showed less than 20% at $0.001{\mu}g/mL$ PAHs and when the concentration was higher, the coefficient of variation was decreased. HPLC/FLD was better for the overall detection of limits. Conclusions: The results indicate that the HPLC/FLD method has good linear range, precision and a detection of limits from $0.00001{\sim}0.0001{\mu}g/mL$ for all 16 PAHs. This study contributes to providing useful data for analysis technology and can be applied to occupational exposure measurement for PAHs in workplaces.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.12-24
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• 2016

The standard ${\kappa}-{\varepsilon}$ and realizable ${\kappa}-{\varepsilon}$ models are adopted to improve the prediction performance on the recirculating flow. In this paper, the backward facing step flows are used to assess the prediction performance of the recirculation zone. The model constants of turbulence model are obtained by the experimental results and they have a different value according to the flow. In the case of an isotropic flow situation, decaying of turbulent kinetic energy should follow a power law behavior. In accordance with the power law, the coefficients for the dissipation rate of turbulent kinetic energy are not universal. Also, the other coefficients as well as the dissipation coefficient are not constant. As a result, a suitable coefficients can be varied according to each of the flow. The changes of flow over the backward facing step in accordance with model constants of the ${\kappa}-{\varepsilon}$ models show that the reattachment length is dependent on the growth rate(${\lambda}$) and the ${\kappa}-{\varepsilon}$ models can be improved the prediction performance by changing the model constants about the recirculating flow. In addition, it was investigated for the curvature correction effect of the ${\kappa}-{\varepsilon}$ models in the recirculating flow. Overall, the curvature corrected ${\kappa}-{\varepsilon}$ models showed an excellent prediction performance.

• Korean Journal of Pharmacognosy
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• v.47 no.4
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• pp.381-388
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• 2016

Hyangso-san is a traditional herbal medicine that consists of the seven herbal medicines, Cyperi Rhizoma, Perillae Folium, Atractylodis Rhizoma, Citri Unshius Pericarpium, Glycyrrhizae Radix et Rhizoma, Zingiberis Rhizoma Crudus, and Allii Fistulosi Bulbus. Hyangso-san has long been clinically used to treat the influenza, including headache, ferver, chills, and pantalgia. In this study, we were performed the simultaneous analysis of the 15 marker compounds (liquiritin apioside, liquiritin, ferulic acid, naringin, hesperidin, rosmarinic acid, liquiritigenin, kaempferol, glycyrrhizin, nobiletin, 6-gingerol, elemicin, atractylenolide III, nootkatone, and atractylenolide I) in Hyangso-san using liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS/MS). Column for the separation of the 15 ingredients was used a Waters Acquity UPLC BEH $C_{18}$ analytical column ($2.1{\times}100mm$, $1.7{\mu}m$) at $45^{\circ}C$ by using a mobile phase of 0.1% (v/v) formic acid in water and acetonitrile with gradient condition. Identifications of all analytes were performed using a Waters ACQUITY TQD LC-MS/MS system. The flow rate and injection volume were 0.3 mL/min and $2.0{\mu}L$, respectively. Correlation coefficient of the calibration curve was ${\geq}0.9958$. The values of limits of detection and quantification of the 15 components were 0.002-4.29 and 0.01-12.88 ng/mL, respectively. The result of an analysis using the established LC-MS/MS method, kaempferol and atractylenolide I were not detected, while other 13 compounds were 0.08-56.87 mg/g in lyophilized Hyangso-san sample.

• Journal of Wetlands Research
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• v.15 no.4
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• pp.609-618
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• 2013

Curve number (CN), originally developed, compiled by 'The Natural Resources Conservation Service (NRCS)', and has been widely used throughout the world. However, there is the uncertainty of CN derived from the use of antecedent moisture condition (AMC)/Antecedent Runoff Condition (ARC). As in Korea where nearly 70% covered by mountainous area, it is still not sufficient handbook precedent to guide or support the estimation of AMC/ARC. The failure to develop formal criteria of applying AMC/ ARC will be a gaping profession and results not only in uncertainty of CN estimation in particular, but also in designing appropriate structures in Korea as a whole. This paper is aiming at presenting a critical review of AMC/ARC and deriving a procedure to deal more realistically with event rainfall-runoff over wider variety of initial conditions. Proposed methods have been developed. It is based on modifying estimated runoff to observed runoff with coefficient of determination and then applying different algebraic expression with the verification of AMC by antecedent rainfall table of NEH-1964. The result shows that algebraic expression by Arnold et al. (1996) is the most appropriate for AMC/ARC and the results of AMC/ARC estimation criteria are generally very close to each other. Therefore, this algebraic expression might be applied in South Korea condition properly.