• 한국진공학회지
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• 제22권5호
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• pp.225-230
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• 2013

크라이오펌프는 응축과 흡착을 통해 기체를 배기하므로 극저온 표면 온도와 증기압이 배기성능에 큰 영향을 미친다. 어느 부분의 온도가 어중간하면 한번 응축했던 기체분자가 방출과 재응축 또는 재흡착을 반복하여 진공용기 압력이 어느 선 이하로 떨어지지 않고 심한 요동을 나타낸다. 어떤 기체나 특정 온도 범위에서 이런 불안정성이 나타날 수 있지만 크라이오펌프를 많이 사용하는 스퍼터 장치의 공정기체인 알곤을 배기할 때 불안정성이 발생하는 것은 좋지 않다. 본 논문에서는 알곤 회복시간 측정실험을 수행하면서 크라이오펌프의 알곤 불안정성의 원인과 대책을 분석했다.

• 대한기계학회논문집
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• 제19권11호
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• pp.2981-2994
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• 1995

In order to elucidate the effects of positive pressure gradient on flame properties, structure and stabilization, an experimental study is made on turbulent diffusion flame stabilized by a circular cylinder in a divergent duct flow. A commercial grade gaseous propane is injected from two slits on the rod as fuel. In this paper, stabilization, characteristics and flame structure are examined by varying the divergent angle of duct. Temperature, ion current and Schlieren photographs were measured. It is found that critical divergent angle is expected to be about 8 ~ 12 degree through blow-off velocity pattern to divergent angle and the positive pressure gradient influences the flame temperature, intensity of ion current and eddy structure behind the rod. With the increase of divergent angle, typical temperature of recirculation zone is low but intensity of ion current is high in shear layer behind rod. Energy distributions of fluctuating temperature and ion current signals turn up low frequency corresponding to large scale eddies but high frequency corresponding to small scale eddies as well as low with the increase of divergent angle. Therefore the flame structure becomes a typical distributed-reacting flame.

• 한국자원식물학회지
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• 제36권6호
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• pp.580-587
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• 2023

Androsace septentrionalis is a grass species restricted to North Korea; however, it is at the brink of extinction due to habitat loss and environmental changes caused by natural disasters and anthropogenic activities. This study was conducted to characterize the dormancy conditions of A. septentrionalis in an effort to conserve this North Korean plant resource. For this purpose, the morphological characteristics and vigor of A. septentrionalis seeds were examined, and its germination characteristics under different temperature conditions (15/6℃ and 25/15℃ ), low-temperature stratification, and gibberellin (GA₃) treatment were determined. The results revealed that A. septentrionalis exhibits non-deep type morpho-physiological dormancy, and low-temperature stratification treatment was not effective in breaking the dormancy of A. septentrionalis seeds. Meanwhile, GA₃ treatment significantly increased the mean germination time, rate, and speed of the seeds. The optimal conditions for the germination of A. septentrionalis seeds were 25/15℃ fluctuating temperature and 500 mg·L¹ GA₃ treatment. The results of this study are useful for the mass propagation of A. septentrionalis.

• 한국수산과학회지
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• 제15권4호
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• pp.271-282
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• 1982

The browning development, mainly through the Maillard reaction, occurring in the dried fish meat products during storage causes reduction of the nutritional value due to the loss of the essential amino acid such as available lysine as well as off -flavor resulting in the deterioration of the food quality thus shortening the shelflife. In the work, the changes in the amount of available lysine, extractable nitrogenous compounds (nonprotein-N, amino-N, trimethylamine oxide, trimethylamine, and free lysine) and development of browning were measured to assess the relationship between the shelflife and the quality loss in dried filefish under the steady state conditions (35,45, and $55^{\circ}C;a_{w}'s$ of 0.44 0.52, 0.65 and 0.75 at each temperature) and fluctuating temperature condition of $35/55^{\circ}C$ will. alternating 7 day periods at each water activity. The results indicated that the amount of available lysine and extractable nitrogenous compounds except TMA decreased rapidly with increasing temperatures and water activities while the rate of available lysine and extractable nitrogenous compounds must be involved in the initial stage of brown pigment formation. The available lysine loss of the dried filefish products stored under the fluctuating temperature conditions was greater than that stored under its fixed mean temperature, $45^{\circ}C$. The activation energies for lysine loss obtained from the Arrhenius plot ranged 6.9 to 4.4 Kcal/mol and $Q_{10}$ values at $40^{\circ}C$ were 1.4 to 1.2. The values for browning were 15.7 to 14.4 Kcal/mol and 2.2 to 2.0 respectively. Shelf-life, defined as the time to reach 0.15 O. D./g solid or the limit of off-color deterioration by browning reaction, was extented longer than the halflife of Iysine loss, actually corresponding $75\%$ loss of available lysine. This suggested that the halflife of lysine loss might not be adequate to assess the shelf-life of the food system with high potential of protein, nonproteinous nitrogen compounds, and lipids.

• Ocean Science Journal
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• 제43권1호
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• pp.1-7
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• 2008

Physical and biological environmental variations in the East Sea were investigated by analysing time-series of oceanographic data and meteorological indices. From 1971 to 2000, dominant periodicity in water temperature variations had two apparent periods of 3 to 4 years and of decades, especially in the southwestern part of the East Sea affected by the influence of inflowing Tsushima warm current. Fluctuating water temperature within a certain period appears to respond to El $Ni{\tilde{n}}o$ events with a time lag. It was found that there was a strong correlation between water temperature and El $Ni{\tilde{n}}o$ events with a time lag of 1.5 and 5.5 years for periods of 3 to 6 years and of decades, respectively. Corresponding with El $Ni{\tilde{n}}o$ events, water temperature variability also showed strong correlation with shift and/or changes in biological and chemical environments of nutrient concentrations, zooplankton biomass, and fisheries. However, there also occurred a short-term periodicity of water temperature variations. Within a period of 1 to 4 years, a relatively short-term cycle of water temperature variation had strong correlation with other climate indices such as Pacific Decadal Oscillation and monsoon index. After comparing coherence and phase spectrum between water temperature and different climate indices, we found that there was a shift of coherent periods to another climate index during the years when climate regime shift was reported.

• 한국식품영양과학회지
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• 제11권3호
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• pp.21-27
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• 1982

건조(乾燥) 말쥐치를 저장중(貯藏中)의 온도(溫度)와 수분활성(水分活性)을 달리하였을 때의 비효소적갈변(非酵素的褐變)을 반응속도론적(反應速度論的)으로 고찰(考察)한 결과(結果)를 요약(要約)하면 다음과 같다. (1) 비효소적갈변(非酵素的褐變)의 반응속도(反應速度)는 수분활성(水分活性) 0.75에서 가장 높았고, Arrhenius식(式)에서 계산(計算)한 활성화(活性化) 에너지는 $12.5{\sim}16.5kcal/mole$, $Q_{10}$치(値)는 $1.9{\sim}2.3$이었다. (2) $25^{\circ}C$에서의 shelf-life(O.D. 0.15/g solid에 도달하는 시간)는 179일(日)${\sim}$302일(日)의 범위였으며 온도(溫度)와 수분활성(水分活性)이 증가(增加)함에 따라 급격히 단축되었다. (3) 변온조건(變溫條件)에서의 저장실험결과(貯藏實驗結果)와 이론적으로 예측한 값 사이에는 ${\Delta}T_{eff}$가 $2.0{\sim}2.6^{\circ}C$로서 실측치(實測値)보다 낮은 값을 보였고, shelf-life는 예측치(豫測値)가 1주일(週日)정도 짧았으나 이 방면의 연구(硏究)가 더욱 진행(進行)된다면 변온저장(變溫貯藏)의 결과(結果)를 효율적으로 예측(豫測)할 수 있을 것으로 예상된다.

• Journal of Microbiology and Biotechnology
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• 제30권7호
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• pp.1072-1081
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• 2020

Screening suitable strains with high temperature adaptability is of great importance for reducing the cost of temperature control in microalgae cultivation, especially in summer. To obtain high temperature-tolerant diatoms, water samples were collected in summer from 7 different regions of China across the Northeast, North and East. A total of 731 water samples was collected and from them 131 diatom strains were isolated and identified based on the 18S rRNA sequences. Forty-nine strains out of the 131 diatoms could survive at 30℃, and 6 strains with relatively high biomass and lipid content at high temperature were selected and were found to be able to grow at 35℃. Cyclotella sp. HB162 had the highest dry biomass of 0.46 g/l and relatively high triacylglycerol (TAG) content of 237.4 mg/g dry biomass. The highest TAG content of 246.4 mg/g dry biomass was obtained in Fistulifera sp. HB236, while Nitzschia palea HB170 had high dry biomass (0.33 g/l) but relatively low TAG content (105.9 mg/g dry biomass). N. palea HB170 and Fistulifera sp. HB236 presented relatively stable growth rates and lipid yields under fluctuating temperatures ranging from 28 to 35℃, while Cyclotella HB162 maintained high lipid yield at temperatures below 25℃. The percentage of saturated fatty acids and monounsaturated fatty acids in all the 6 strains was 84-91% in total lipids and 90-94% in TAGs, which makes them the ideal feedstock for biodiesel.

• 한국수산과학회지
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• 제55권4호
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• pp.449-454
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• 2022

The oxygen consumption rate (OCR) based on the water temperature and body size of the sea squirt Halocynthia roretzi was examined to provide quantitative information about the metabolic response of the species. OCRs were measured using a closed flow-through respirometer at four different water temperatures (10, 15, 20 and 25℃) and two different body sizes (21.4±1.1 g and 150.5±1.3 g, wet weight) with triplicates of each treatment. OCR increased as water temperature increased at both body sizes, but decreased as body size increased regardless of the water temperature (P<0.001). The effect of body size evaluated as a power function ranged from 0.8055 to 0.8884. The highest Q₁₀ values in the small and large size groups ranged from 15 to 20℃ and 20 to 25℃, respectively. The metabolic daily energy loss rate via respiration at all tested temperatures ranged from 56.2 to 106.1 J g^-1 d^-1 in the small-size group and from 44.5 to 92.0 J g^-1 d^-1 in the large-size group. Our results indicate that the metabolic response of H. roretzi highly depends on fluctuating water temperature at a given life stage.

• Journal of Positioning, Navigation, and Timing
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• 제4권2호
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• pp.87-95
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• 2015

In this study, the temporal and spatial variation in precipitable water vapor (PWV) was analyzed for typhoon Ewiniar which had made landfall in the Korean peninsula in 2006. To make a contour map of PWV, zenith total delay (ZTD) was calculated using about 60 GPS permanent stations in Korea, and the pressure and temperature data of nearby AWS stations were interpolated and applied to the equation for calculating the PWV. While Typhoon Ewiniar was migrating north from the southern coast to the eastern coast of Korea, the PWV migrated showing a spatial distribution similar to that of rainfall. Also, the fluctuating pattern of the normalized PWV was analyzed, and the moving speed of the PWV was estimated using the delay time of the increase/decrease pattern in the eight-test stations. The result indicated that the moving speed of the PWV was about 35 km/h, which was similar to the average moving speed of the typhoon (38.9 km/h).

• 동력기계공학회지
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• 제2권2호
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• pp.13-19
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• 1998

The purpose of study is to investigate the flame stability and Structure of turbulent diffusion flame behind the hollowed flame holder, which is located on the waste gas coming out from the test furnace. Fluctuating temperature and ion current measurement and their statistical treatment were used for the purpose. Three types of flame were stabilized and each of which were changed by adequate equivalence ration. And we found that have no periodicity near reacting zone.