• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.5
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• pp.588-597
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• 1999

Sokkuram grotto, a UNESCO cultural heritage in Kyongju Korea, was originally covered with crushed rocks over its dome with ventilating holes. The grotto was perfectly preserved for more than 12 centuries until the upper structure was replaced with a concrete dome in the early 20th century to protect from total collapse. Since then, heavy dew formed on the granite surface to seriously damage the sculptures until it was further remodeled with air-conditioning facilities in the 60s. It is considered that the original upper porous structure had a dehumidifying capability. This research is made to unveil the dehumidifying mechanism of the rock layer during the rainy season in that area. A rock layer and a concrete layer are tested in a temperature/humidity-controlled room. No dew formation is observed for the two specimen for continued sunny days or continued rainy days. However, heavy dew formed on the concrete surface for a sunny day after long rainy days. It is thought that the sun evaporates water on the ground and dew is formed at the surface as the highly humid air touches the yet cold concrete. On the contrary, no dew formation is observed for the rock layer at any time. Even in the above worst situation, air flows downward through the cool rock layer and moisture is removed before reaching inside. Temperature measurement, flow visualization, observation of dew formation and measurement of air velocity are made to verify the mechanisms.

• Korean Journal Plant Pathology
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• v.14 no.6
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• pp.578-582
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• 1998

In greenhouse studies, control efficacy of water chestnut (Eleocharis Kuroguwai) by Epicoccosorus nematosporus was affected by temperature and dew condition. The appressoria were formed abundantly in the range of 20~28$^{\circ}C$. When stem segments o(30 cm long) of the water chestnut were inoculated with the conidial suspension of E. nematorporus, the mean conidial number attacted amounted to 2,545 conidia. Out of 2545 conidia attacted to the stem pieces, 1,733 (68%) conidia formed appressoria. When these stem pieces were treated for 24 hr at 28$^{\circ}C$ under dew condition, 183,1 (7.2%) lesions were formed 10 days after incubation. The time necessary for the death of the plants was about 24 days. Appressoria were formed at 15~35$^{\circ}C$, but decreased rapidly in their numbers at the temperature lower than 1$0^{\circ}C$ or at 35$^{\circ}C$. The appressoria formation seemed to be depended on the dew duration, which was effective to the lesion formation and plant mortality. Under dew duration of 16~24 hr with temperature range of $25^{\circ}C$ to 3$0^{\circ}C$, the weed control was increased up to 93.9%. There were no differences between the first and second or third dew treatments. A delay of 2 or 3 days in dew treatment did not increase the mortality of plants. For the use of E. nematosporus as a mycoherbicide of water chestnut, a conidial suspension should be applied when dew conditions are kept for 12 hr after inoculation.

• The Plant Pathology Journal
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• v.18 no.1
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• pp.50-53
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• 2002

To develop Epicoccosorus nematosporus as a mycoherbicide of Eleocharis kuroguwai, the optimum temperature and humidity for sporulation of the pathogen were studied. Conidial production was most abundant at $28^{\circ}C$ with RH 60%, which yielded 661 mg in 9 cm Petri dish. Light intensity of 3,000 up to 7,500 lux was effective in stimulating conidial production of E. nematosporus on oatmeal agar, Light intensity affected sporulation more significantly than temperature. In the pot test, at least 12 h of dew period at $20^{\circ}C$ and $25^{\circ}C$ was required to achieve satisfactory conidial germination and appressorial formation. Few were killed at 8 h of dew period regardless of temperature. Sixteen hours of a single dew treatment immediately after inoculation killed more plants than did two or three repetitive dew treatments of 8-12 h.

• Corrosion Science and Technology
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• v.22 no.5
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• pp.351-358
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• 2023

Although many thermal power plants use heat recovery systems, high exhaust gas temperatures are maintained due to corrosion at dew points and ash deposits caused by condensate formation. The dew point of exhaust gas is primarily determined by the concentration of SO₃ and steam, and various experiments and calculation equations have been employed to estimate it. However, these methods are known to be less suitable for exhaust gases with low SO₃ concentrations. Therefore, in this study, since the temperature of the exhaust gas is expected to decrease due to the low-load operation of the coal-fired power plant, sulfuric acid condensation and low-temperature corrosion are anticipated. We aimed to conduct a quantitative evaluation to propose ways to prevent damage by limiting operating conditions and improving facilities. The experimental results showed that the corrosion rate increased linearly with rising temperatures at a certain sulfuric acid concentration. Furthermore, variations in sulfuric acid concentrations generated during the current power plant operation process did not significantly affect the dew point, and the dew point of sulfuric acid under these conditions was observed to be between 120 - 130 ℃.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.247-253
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• 2010

The characteristics of selective oxidation prior to hot-dip galvanizing with the annealing atmosphere dew point and chemical composition in dual-phase steels and their effect on the inhibition layer formation relevant to coating adhesion have been studied using a combination of electron microscopic and surface analytical techniques. The annealed and also galvanized samples of 3 kinds of Si/Mn ratios with varied amounts of Si addition were prepared by galvanizing simulator. The dew point was controlled at soaking temperature $800^{\circ}C$ in 15%$H_2$ -85%$N_2$ atmosphere. It was shown that good adhesion factors were mainly uniformity of oxide particle distribution of low number density and low Si/Mn ratio prior to hot-dip galvanizing. Their effect was the greatly reduced coating bare spots and the formation of uniform inhibition layer leading to good adhesion of Zn overlay. The mechanism of good adhesion is suggested by two processes: the formation of inhibition layer on the oxide free surface uncovered with no $SiO_2$-containing particles in particular, and the inhibition layer bridging of oxide particles. The growth of inhibition layer was enhanced markedly by the delayed reaction of Fe and Al with the increase of Si/Mn ratio.

• The Plant Pathology Journal
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• v.18 no.2
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• pp.81-84
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• 2002

Effects of temperature and dew period on sporulation of a mycoherbicide, Epicoccosorus nematosporus, on the lesion of its host, Eleocharis kuroguwai were determined. Conidia formation was first observed after 10 days on plants incubated for either 12 or 16 h in a dew chamber at 28$^{\circ}C$; 16 h dew period resulted in more conidia formation. As the dew period was decreased to less than 8 h, fewer conidia formed. Conidial production was most abundant at 28$^{\circ}C$ and produced as much as 3.3$\times$10$^4$conidia per lesion, while 0.1$\times$10$^3$and 2.3$\times$10$^3$conidia per lesion were produced at 16$^{\circ}C$ and 36$^{\circ}C$, respectively. Alternating temperature regimes, i.e., 30/15, 30/20, 28/20, and 28/15$^{\circ}C$ (day/night) were much better than constant temperature, i.e., 30/30, 28/28/, and 20/2$0^{\circ}C$ for sporulation. In the second sporulation, there were as much as 3.1$\times$10$^4$conidia per lesion (ca. <50% of the first sporulation). Then, sporulation dropped sharply to 6.2$\times$10$^2$conidia per lesion in the third sporulation. Results of this study suggest that temperature combined with dew period is the primary limiting factor in the use of E. nematosporus as a mycoherbicide off, kuroguwai.

• Corrosion Science and Technology
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• v.10 no.1
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• pp.6-12
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• 2011

The selective surface oxidation of a transformation-induced-plasticity (TRIP) steel containing 1.6 wt.% Mn and 1.5 wt.% Si during annealing at $800^{\circ}C$ was investigated for its influence on the formation of an inhibition layer during hot-dip galvanizing. The selective oxidation of the alloying elements and the oxide morphology were significantly influenced by the annealing atmosphere. The pure $N_{2}$ atmosphere with a dew point $-40^{\circ}C$ promoted the selective oxidation of Mn as a crystalline $Mn_{2}SiO_{4}$ phase, whereas the $N_{2}$ + 10% $H_{2}$ atmosphere with the same dew point $-40^{\circ}C$ promoted the selective oxidation of Si as an amorphous Si-rich oxide phase. During hot-dip galvanizing, the $Mn_{2}SiO_{4}$ phase was reduced more readily by Al in the Zn bath than the Si-rich oxide phase. Consequently, the pure $N_{2}$ atmosphere resulted in a higher formation rate of $Fe_{2}Al_{5}$ particles at the Zn/steel interface and better galvanizability than the $N_{2}$ + 10% $H_{2}$ atmosphere.

• Journal of the Mineralogical Society of Korea
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• v.29 no.3
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• pp.131-139
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• 2016

Detailed knowledge on maskelynite, a glassy phase of plagioclase found in shocked meteorites and impact craters, is essential to understand a shock metamorphism. Here, we explore an inhomogeneous shock metamorphism in the lunar meteorite Mount DeWitt (DEW) 12007 with an aim to understand the formation mechanism of maskelynite. Most plagioclase grains in the DEW 12007 partially amorphized into maskelynite with a unidirectional orientation. Back-scattered electron (BSE) images of maskelynite show a remnant of planar deformation fracture possibly indicating that the maskelynite would be formed by solid-state transformation(i.e., diaplectic glass). Plagioclase with flow texture is also observed along the rim of maskelynite, which would be a result of recrystallization of melted plagioclase. Results of Raman experiments suggest that shock pressure for plagioclase and maskelynite in the DEW 12007 is approximately 5-32 GPa and 26-45 GPa, respectively. The difference in shock pressures between plagioclase and maskelynite can be originated from 1) external factors such as inhomogeneous shock pressure and/or 2) internal factors such as chemical composition and porosity of rock. Unfortunately, Raman spectroscopy has a limitation in revealing the detailed atomic structure of maskelynite such as development of six- or five-coordinated aluminum atom upon various shock pressure. Further studies using nuclear magnetic resonance spectroscopy are necessary to understand the formation mechanism of maskelynite under high pressure.

• Applied Microscopy
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• v.43 no.1
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• pp.40-45
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• 2013

Phase transformation by the Mn-deprivation was observed in the high-Mn twinning-induced plasticity-aided steel. Mn-depletion was induced by the formation of Mn-O oxide during the dew-point control process at temperature above $-20^{\circ}C$, which changed austenitic parent phase to multi-grained ferrite. Mixture of Al-O, Al-Mn-Si-O oxides were observed at the grain boundaries of transformed ferrite.

• Atmosphere
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• v.23 no.4
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• pp.443-452
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• 2013

The original Fog Stability Index (FSI) is formulated as FSI=$2(T-T_d)+2(T-T_{850})+WS_{850}$, where $T-T_d$ is dew point deficit (temperature-dew point temperature), $T-T_{850}$ is atmospheric stability measure (temperature-temperature at 850 hPa altitude) and $WS_{850}$ is wind speed at 850 hPa altitude. As a way to improve fog prediction at Incheon International Airport (IIA), we develop the modified FSI for IIA, using the meteorological data at IIA for two years from June 2011 to May 2013, the first one year for development and the second one year for validation. The relative contribution of the three parameters of the modified FSI is 9: 1: 0, indicating that $WS_{850}$ is found to be a non-contributing factor for fog formation at IIA. The critical success index (CSI) of the modified FSI is 0.68. Further development is made to consider the fact that fogs at IIA are highly influenced by advection of moisture from the Yellow Sea. One added parameter after statistical evaluation of the several candidate parameters is the dew point deficit at a buoy over the Yellow Sea. The relative contribution of the four parameters (including the new one) of the newly developed FSI is 10: 2: 0.5: 6.4. The CSI of the new FSI is 0.50. Since the developmental period of one year is too short, the FSI should be refined more as the data are accumulated more.