• Journal of Species Research
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• v.9 no.2
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• pp.170-173
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• 2020

Research on Korean nematocerous flies (Diptera: Nematocera) was started by the National Institute of Biological Resources in 2012. This publication is a continuation of our previous work. During the season of 2019 insects were collected in Odaesan National Park by the researchers from Korea University. Among these samples, two specimens belonging to the family Hesperinidae, which was previously unrecorded from Korea, were noticed. This family is known from countries bordering Korea (East Siberia and Far East of Russia, Hokkaido Island of Japan), thus occurrence of hesperinid flies was expected on the Korean Peninsula. Only one genus Hesperinus Walker, 1848 with eight species belong to this family. They are developing in decaying wood of deciduous trees. Hesperinus rohdendorfi Krivosheina & Mamaev, 1967, which was known from East Siberia and Far East of Russia is recorded from South Korea. Redescription and photographs of the most important taxonomical details are presented.

• Journal of Advanced Marine Engineering and Technology
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• v.29 no.3
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• pp.260-274
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• 2005

An experimental investigation was performed to study the characteristics of turbulent swirling flow in the cylindrical annuli. The swirl angle measurements were performed by flow visualization technique using smoke and dye liquid. By using the particle image velocimetry method. this study has found the time-mean velocity distribution and turbulent intensity with swirl for Re=20,000. 30.000. 50.000. and 70,000 along longitudinal sections. The results appear to be physically reasonable. Other experimental study was performed to investigate heat transfer characteristics of turbulent swirling air flow in axisymmetric annuli. The static pressure. the local air flow temperature, and the wall temperature with decaying swirl were measured by using thermocouples and the friction factor and the local Nusselt number were calculated for Re=30,000. 50,000 and 70000. The local Nusselt number was compared with that obtained from the Dittus-Boelter equation with swirl and without swirl, respectively. The results showed that the swirl enhances the heat transfer at the inlet and the outlet of the test tube.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.66-73
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• 2004

This paper presents wafer motion modeling of transfer unit in clean tube system, which was developed as a means for transferring the air-floated wafers inside the closed tube filled with the super clean airs. When the wafer is transferred in x direction with an initial velocity the motion along x direction can be modeled as a simple decaying motion due to viscous friction of the fluid. But, the motion in y direction is modeled as a mass-spring-damper system where the recovering force by air jets issued from the perforated is modeled as a linear spring. Experiments with a clean tube system built fur 12 wafer show the validity of the presented force and motion models.

• Journal of Mechanical Science and Technology
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• v.19 no.6
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• pp.1378-1389
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• 2005

This work provides the fundamental knowledge of energy transport characteristics during very short-pulse laser heating of semiconductors from a microscopic viewpoint. Based on the self-consistent hydrodynamic equations, in-situ interactions between carriers, optical phonons, and acoustic phonons are simulated to figure out energy transport mechanism during ultrafast pulse laser heating of a silicon substrate through the detailed information on the time and spatial evolutions of each temperature for carriers, longitudinal optical (LO) phonons, acoustic phonons. It is found that nonequilibrium between LO phonons and acoustic phonons should be considered for ultrafast pulse laser heating problem, two-peak structures become apparently present for the subpicosecond pulses because of the Auger heating. A substantial increase in carrier temperature is observed for lasers with a few picosecond pulse duration, whereas the temperature rise of acoustic and phonon temperatures is relatively small with decreasing laser pulse widths. A slight lagging behavior is observed due to the differences in relaxation times and heat capacities between two different phonons. Moreover, the laser fluence has a significant effect on the decaying rate of the Auger recombination.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.380-383
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• 2019

인터넷의 급속한 발전은 네트워크를 통해 많은 정보를 흘러가도록 만들었다. 그 정보들 중에는 다른 시스템이나 사용자에게 루머나 바이러스와 같은 좋지 않은 정보를 포함하는 경우도 있는데, 이에 대비해서 이런 악성정보가 더 많이 퍼져나가지 않도록 다양한 보안방법들이 제안되었다. 본 논문에서는 이를 위해 정보를 처음 퍼뜨린 근원을 추정해 나가는 문제를 고려한다. 특히, 기존의 이 문제를 다룬 많은 연구에서와는 다르게 본 연구에서는 정보가 시간이 지남에 따라, 혹은 근원으로부터 멀어짐에 따라 그 전파력이 감쇠되는 여러 가지 정보확산 모델을 고려한 후, 각각의 모델에서 트리기반 추정법을 사용하여 정보의 근원을 얼마나 잘 탐지해 내는지에 대해 살펴본다.

• Entomological Research
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• v.48 no.6
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• pp.514-521
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• 2018

Drosophila melanogaster Meigen and Drosophila suzukii Matsumura are taxonomically close Drosophila species belonging to the family Drosophilidae and melanogaster group. D. melanogaster is thought to be evolutionarily adapted to overripe, decaying, and fermented fruits, in which large amounts of chemicals such as ethanol, acetic acid, and 2-phenylethanol are produced, whereas, D. suzukii is attracted to fresh ripening fruit. Considering the distinct habitats of the two flies, D. suzukii is hypothesized to exhibit higher susceptibility to these chemicals than D. melanogaster. Therefore, in this study, we investigated the survival rate of the flies at various concentrations of three chemicals (2-phenlyethanol, acetic acid, and ethanol) and calculated the lethal concentration (LC) values to compare the tolerance and susceptibility of D. melanogaster and D. suzukii to the chemicals. Our results revealed that D. melanogaster exhibited higher tolerance than D. suzukii to all chemicals, supporting the hypothesis of different evolutionary adaptations to distinct habitats of the two flies.

• Mycobiology
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• v.47 no.3
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• pp.261-272
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• 2019

Oomycetes are widely distributed in various environments, including desert and polar regions. Depending upon different habits and hosts, they have evolved with both saprophytic and pathogenic nutritional modes. Freshwater ecosystem is one of the most important habitats for members of oomycetes. Most studies on oomycete diversity, however, have been biased mostly towards terrestrial phytopathogenic species, rather than aquatic species, although their roles as saprophytes and parasites are essential for freshwater ecosystems. In this study, we isolated oomycete strains from soil sediment, algae, and decaying plant debris in freshwater streams of Korea. The strains were identified based on cultural and morphological characteristics, as well as molecular phylogenetic analyses of ITS rDNA, cox1, and cox2 mtDNA sequences. As a result, we discovered eight oomycete species previously unknown in Korea, namely Phytopythium chamaehyphon, Phytopythium litorale, Phytopythium vexans, Pythium diclinum, Pythium heterothallicum, Pythium inflatum, Pythium intermedium, and Pythium oopapillum. Diversity and ecology of freshwater oomycetes in Korea are poorly understood. This study could contribute to understand their distribution and ecological function in freshwater ecosystem.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.652-665
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• 2019

Analytical solutions of the reactant concentration inside porous spherical catalytic particles were obtained from unsteady reaction-diffusion equation by applying eigenfunction expansion method. Various surface concentrations as exponentially decaying or oscillating function were considered as boundary conditions to solve the unsteady partial differential equation as a function of radial distance and time. Dirac delta function was also used for the instantaneous injection of the reactant as the surface boundary condition to calculate average reactant concentration inside the particles as a function of time by Laplace transform. Besides spherical morphology, other geometries of particles, such as cylinder or slab, were considered to obtain the solution of the reaction-diffusion equation, and the results were compared with the solution in spherical coordinate. The concentration inside the particles based on calculation was compared with the bulk concentration of the reactant molecules measured by photocatalytic decomposition as a function of time.

• Bulletin of the Korean Chemical Society
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• v.12 no.3
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• pp.315-322
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• 1991

In a recent $paper^1$ we reported equilibrium (EMD) and non-equilibrium (NEMD) molecular dynamics simulations of liquid argon using the Green-Kubo relations and NEMD algorithms to calculate the thermal transport coefficients-the self-diffusion coefficient, shear viscosity, and thermal conductivity. The overall agreement with experimental data is quite good. In this paper the same technique is applied to calculate the thermal transport coefficients of liquid water at 298.15 K and 1 atm using TIP4P model for the interaction between water molecules. The EMD results show difficulty to apply the Green-Kubo relations since the time-correlation functions of liquid water are oscillating and not decaying rapidly enough except the velocity auto-correlation function. The NEMD results are found to be within approximately ${\pm}$30-40% error bars, which makes it possible to apply the NEMD technique to other molecular liquids.

• Korean Journal of Remote Sensing
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• v.38 no.4
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• pp.387-394
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• 2022

Coastal upwelling is a significantly imperative process for understanding the interactions between physical and ecological processes and has been investigated incessantly. In this study, we explored the upwelling index, specifically upwelling age (UA). UA enabled us to observe the initiating, sustaining, and decaying upwelling processes. Although the sensitivity of many other geophysical parameters to estimate UA has been investigated, the wind direction has not been evaluated. Thus, we assessed the appropriate wind direction for the UA and obtained efficient upwelling signals from the four coastal stations. Furthermore, we applied the UA and compared it with the satellite sea level anomaly, sea surface temperature, and chlorophyll-a changes to validate how UA depicts their spatial extents. Thus, UA can predict the timing of coastal upwelling events using predicted geophysical parameters.