• Journal of Korean Society of Forest Science
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• v.110 no.4
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• pp.543-553
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• 2021

This research focused on the investigation of isoprene and terpene emissions from 30 major urban tree species. We conducted sampling using a specific dynamic enclosure system between August and September 2020. Seedlings less than three years old were enclosed in a chamber consisting of a 400 L transparent Tedlar bag. The air-flows from the chamber's outlet were sampled using Tenax-filled sorbent tubes in the presence of standard conditions (temperature: 30℃, PAR: 1,000 μmol/m²/sec). A thermal desorption GC/MS system was used to analyze 38 BVOC compounds (isoprene, monoterpene, sesquiterpene, oxygenated monoterpene, and sesquiterpene). Isoprene emitters included Phyllostachys bambusoides, Quercus serrata, Daphniphyllum macropodum, and Buxus Koreana. Monoterpene emitters included Pinus rigida, Acer pictum subsp. mono, Larix kaempfer, Magnolia denudata, Metasequoia glyptostroboides, Pinus koraiensis, Pinus densiflora, and Abies holophylla. The monoterpene emission profiles were dominated by α-pinene, myrcene, limonene, β-pinen, and sabinene, while caryophyllene and farnesene were the prominent sesquiterpenes. Predominant oxygenated monoterpene compounds were also discovered as pulegone, borneol, menthol, eucalyptol, and nerol, while caryophyllene oxide were the prominent oxygenated sesquiterpenes. Sesquiterpenes and oxygenated sesquiterpenes had relatively lower contributions for all species.

• Journal of the Korean Geotechnical Society
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• v.35 no.6
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• pp.39-48
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• 2019

This study investigated the lateral behavior of monopile embedded in the dry sand through cyclic lateral loading test using a centrifuge test. The sand sample for the experiment was the dry Jumunjin standard sand at 80% relative density and the friction angle of $38^{\circ}$. In the experimental procedure, firstly, it was determined the static lateral bearing capacity by performing the static lateral loading test to decide the cyclic load. This derived static lateral bearing capacity values of 30%, 50%, 80%, 120% were determined as the cyclic lateral load, and the number of cycle was performed 100 times. Through the results, the experiment cyclic p-y curve was calculated, and the cyclic p-y backbone curve by depth was derived using the derived maximum soil resistance point by the load. The initial slope at the same depth was underestimated than API (1987) p-y curves, and the ultimate soil resistance was overestimated than API (1987) p-y curves. In addition, the result of the comparison with the suggested dynamic p-y curve was that the suggested dynamic p-y curve was overestimated than the cyclic p-y backbone curve on the initial slope and soil resistance at the same depth. It is considered that the p-y curve should be applied differently depending on the loading conditions of the pile.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.1
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• pp.1-13
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• 2019

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulted in the deposition of large quantities of radionuclides over parts of eastern Japan. Radioactive contaminants have been observed over a large area including forests, cities, rivers and lakes. Due to the strong adsorption of radioactive cesium by soil particles, radioactive cesium migrates with the eroded soil, follows the surface flow paths, and is delivered downstream of population-rich regions and eventually to coastal areas. In this study, we developed a model to simulate the transport of contaminated sediment in a watershed hydrological system and this model was compared with observation data from eroded soil observation instruments located at the Korea Atomic Energy Research Institute. Two methods were applied to analyze the soil particle size distribution of the collected soil samples, including standardized sieve analysis and image analysis methods. Numerical models were developed to simulate the movement of soil along with actual rainfall considering initial saturation, rainfall infiltration, multilayer and rain splash. In the 2019 study, a numerical model will be used to add rainfall shield effect by trees, evaporation effect and shield effects of surface water. An eroded soil observation instrument has been installed near the Wolsong nuclear power plant since 2018 and observation data are being continuously collected. Based on these observations data, we will develop the numerical model to analyze long-term behavior of radionuclides on land as they move from land to rivers, lakes and coastal areas.

• Journal of the Korean Chemical Society
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• v.64 no.6
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• pp.327-333
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• 2020

Performance of a portable GC that can be utilized for the real time determination of volatile organic compounds in air was evaluated. It employs purified/compressed ambient air as the carrier gas eliminating the need for high pressure gas tanks. The compact system with dimensions of 35 × 26 × 15 ㎤ and weight of 5 kg is powered by either a 24 V DC external adapter or battery pack. Chromatograms of the mixture sample including benzene, toluene, ethylbenzene, and oxylene at concentrations of 1 ppmv and 20 ppmv represent a good reproducibility: 3.79% and 0.48% relative standard deviations (RSDs) for peak area variations; 0.40% and 0.08% RSDs for retention times. The method detection limit was 0.09 ppmv. A 30 m long, 0.28 mm I.D. column operated at an optimal condition yielded a peak capacity of 61 with good resolution for a 10 min isothermal analysis. The relative standard deviations (RSD) of the peak area variations and retention times during consecutive measurements over 27 h were less than 2.4%RSD and 0.5%RSD, respectively. Thus, this instrument makes it suitable for continuous and field analysis of low-concentration VOC mixtures in the indoor/outdoor environment as well as the spillage accident of hazardous chemicals.

• New Physics: Sae Mulli
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• v.68 no.11
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• pp.1167-1172
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• 2018

Carbon nanotubes (CNTs) are structures of carbon atoms bonded together in hexagonal honeycomb shapes, with multi-walled CNTs having a very high thermal conductivity of $3000W/m{\cdot}K$ and single-walled CNTs having a conductivity of $6000W/m{\cdot}K$. In this work, the transmittance and the thermal diffusivity of a multi-walled carbon nanotube dispersion with a concentration of 1.5 M were measured using a single beam method, a dual beam method, and the thermal lens effect. The nonlinear optical coefficients were obtained by using the z-scan method, which moved the sample in the direction of propagation of the single laser beam, propagation and the thermal diffusivity was measured using a double laser beam. As a pump beam, a diode-pumped solid state (DPSS) laser with a wavelength of 532 nm and an intensity of 100 mW was used. As the probe beam, a He-Ne laser having a wavelength of 633 nm and an intensity of 5 mW was used. The experimental result shows that when the concentrations of the sample were 9.99, 11.10, 16.65, and 19.98 mM, the nonlinear absorption coefficients were 0.046, 0.051, 0.136 and 0.169 m/W, respectively. Also, the nonlinear refractive indices were 0.20, 0.51, 1.25 and $1.32{\times}10^{-11}m^2/W$, respectively, and the average thermal diffusivity was $1.33{\times}10^{-6}m^2/s$.

• Journal of the Korean Geotechnical Society
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• v.37 no.6
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• pp.29-37
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• 2021

Since many geotechnical structures are constructed on a weathered granite layer, it is important to evaluate their characteristics. As a seismic design is the more important nowadays, the demands to estimate a shear wave velocity (V_S) based on acceptable methods are increasing. In this study, an empirical equation predicting V_S of the weathered granite layer is suggested based on the nonlinear multiple variable regression analysis whose independent variables are both SPT (Standard penetration test)-N₆₀ and chemical weathering index. It is concluded that the accuracy of the empirical equation estimating V_S of the weathered granite layer increases when it considers the chemical weathering index as an additional independent variable compared to the result of simple regression analysis using only N₆₀.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.701-718
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• 2021

Geological field surveys and a series of laboratory tests were conducted to obtain data related to landslides in Sancheok-myeon, Chungju-si, Chungcheongbuk-do, South Korea where many landslides occurred in the summer of 2020. The magnitudes of various factors' influence on landslide occurrence were evaluated using logistic regression analysis and an artificial neural network. Undisturbed specimens were sampled according to landslide occurrence, and dynamic cone penetration testing measured the depth of the soil layer during geological field surveys. Laboratory tests were performed following the standards of ASTM International. To solve the problem of multicollinearity, the variation inflation factor was calculated for all factors related to landslides, and then nine factors (shear strength, lithology, saturated water content, specific gravity, hydraulic conductivity, USCS, slope angle, and elevation) were determined as influential factors for consideration by machine learning techniques. Minimum-maximum normalization compared factors directly with each other. Logistic regression analysis identified soil depth, slope angle, saturated water content, and shear strength as having the greatest influence (in that order) on the occurrence of landslides. Artificial neural network analysis ranked factors by greatest influence in the order of slope angle, soil depth, saturated water content, and shear strength. Arithmetically averaging the effectiveness of both analyses found slope angle, soil depth, saturated water content, and shear strength as the top four factors. The sum of their effectiveness was ~70%.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.493-506
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• 2021

Liquefaction refers to a phenomenon in which excessive pore water pressure occurs when a dynamic load such as an earthquake rapidly acts on a loose sandy soil saturated with soil, and the ground loses effective stress and becomes liquefied. The indoor repeated test for liquefaction evaluation can be confirmed through the repeated triaxial compression test and the repeated shear test. In this regard, this study tried to confirm the liquefaction resistance strength according to the relative density and particle size distribution of sand using the repeated triaxial compression test. As a result of the experiment, it was confirmed that the liquefaction resistance strength increased as the relative density increased regardless of the soil classification, and the liquefaction resistance strength according to the particle size distribution of the sand was confirmed that the liquefaction resistance strength of the SP sample close to SW was significantly higher. In addition, as a result of analyzing 30% of fine powder compared to 0% of fine powder, as the relative density increased to 40~70%, the liquefaction resistance strength decreased by 5~20%, and the domestic weathered soil ground had a fine liquefaction resistance strength compared to Jumunjin standard sand. When the minute was 10%, it was measured to be 30% or more, and when the fine particle was 30%, it was measured to be less than 50%.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.242-250
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• 2022

Here we aimed to date the year and season of the resin collection from Korean red pines at Worak mountain and investigate the natural healing ability of the wounds using the tree-ring analysis technique. We determined the dating of the resin collection based on the synchronization between the ring-width time series from the wound surface of the experimental trees and the local master chronology, which is the mean time series from the sound surface on the opposite side of the wounds. For the dating of resin collection, we selected thirteen Korean red pines with resin wounds. For the investigation on the annual healing ability of the wounds, we sampled three dead trees out of 13 trees as disks. Through the comparison of the individual ring-width time series from the wounds with the local master chronology, it was verified that the resin collection was undertaken between the spring of 1962 and the autumn of 1975. The mean healing length of the wounds was 15.8 cm over the preceding 42 years, making their annual mean healing 0.38 cm. Through our study we successfully verified the healing ability of the wounded Korean red pines for the resin collection as well as the undocumented resin collection history.

• Journal of Korean Society of Forest Science
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• v.111 no.4
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• pp.490-501
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• 2022

In this study, the isoprene and terpene emissions from 32 major urban tree species were investigated. We conducted sampling using a dynamic enclosure system between June and July 2021. Seedlings aged < three years were enclosed in a chamber consisting of a 400 L transparent Tedlar bag. The air flow from the outlet of the chamber was sampled using Tenax-filled sorbent tubes under standard conditions (temperature: 30°C; PAR: 1,000 μmol/m²/sec). A thermal desorption gas chromatography/mass spectrometry system was used to analyze the following 38 biogenic volatile organic compounds: isoprene, monoterpenes, sesquiterpenes, oxygenated monoterpenes, and oxygenated sesquiterpenes. Isoprene emitters included Quercus mongolica, Salix koreensis, Robinia pseudoacacia, and Salix chaenomeloides. Monoterpene emitters included Pinus strobus, Cedrela sinensis, and Cercis chinensis. The monoterpene emission profiles were dominated by á-pinene, myrcene, camphene, and limonene. The predominant oxygenated monoterpene and oxygenated sesquiterpene were eucalyptol and caryophyllene oxide, respectively. For all species, the contributions of sesquiterpenes and oxygenated sesquiterpenes were relatively low.