• Title/Summary/Keyword: C-22

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Effects of Oxidation and Hot Corrosion on the Erosion of Silicon Nitride

  • Kim, Jong Jip
    • Corrosion Science and Technology
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    • v.4 no.4
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    • pp.136-139
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    • 2005
  • The effect of oxidation and hot corrosion on the solid particle erosion was investigated for hot-pressed silicon nitride using as-polished, pre-oxidized and pre-corroded specimens by molten sodium sulfates. Erosion tests were performed at 22, 500 and $900^{\circ}C$ using angular silicon carbide particles of mean diameter $100{\mu}m$. Experimental results show that solid particle erosion rate of silicon nitride increases with increasing temperature for as-polished or pre-oxidized specimens in consistent with the prediction of a theoretical model. Erosion rate of pre-oxidized specimens is lower than that of as-polished specimens at $22^{\circ}C$, but it is higher at $900^{\circ}C$. Lower erosion rate at $22^{\circ}C$ in the pre-oxidized specimens is attributed due to the blunting of surface flaws, and the higher erosion rate at $900^{\circ}C$ is due to brittle lateral cracking. Erosion rate of pre-corroded specimens decreases with increasing temperature. Less erosion at $900^{\circ}C$ than at $22^{\circ}C$ is associated with the liquid corrosion products sealing off pores at $900^{\circ}C$ and the absence of inter-granular crack propagation observed at $22^{\circ}C$.

STUDIES ON THE LIPID OF AQUATIC PRODUCTS (PART 2) (수산물의 지질에 관한 연구 (제2보) -해조류 지질의 지방산조성에 대하여-)

  • HA Bong Seuk
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.10 no.4
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    • pp.199-204
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    • 1977
  • The patterns of fatty acid composition of lipid extracted from eight species of edible marine benthic algae; i. e. two species of green, five of brown and one of red algae, were investigated quantitatively by using gas liquid chromatography. The total lipid contents in average of the algae were $1.51\%$ in the green algae, $2.81\%$ in brown algae and $1.02\%$ in red algae respectively. Upon analyzing fatty acid composition, green algae contained the highest proportion of $C_{16:0}$ acid and comparatively higher content of $C_{18:1},\;C_{18:2}\;and\;C_{18:3}$ acids than the other algae. In brown angae, $C_{16:0}$ acid content was highest, but not more than that of green algae, and $C_{14:0},\;C_{18:1}$ acids were higher than other $C_{16:1},\;C_{18:2}\;and\;C_{18:3}$ acids while the content of $C_{18:0}$ acid was very low. Red algae showed low content of $C_{14:0},\;C_{18:1},\;C_{18:2}\;and\;C_{18:3}$ acids, but the content of $C_{16:0}$ acid was high as a major component. In regard to the composing patterns of carbon number of fatty acid of algae; i. e. $C_{14},\;C_{15},\;C_{16},\;C_{18}\;and\;C_{22}$ and $C_{22}$ acids, the green algae contained $C_{16}$ and $C_{18}$ acids, the brown algae $C_{16},\;C_{18},\;and\;C_{22}$ and $C_{22}$ acids, and the red algae $C_{15},\;C_{16}$, and $C_{18}$ acids as the major component.

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Comparison of Condenser Characteristics using R134a and R22 under the Same Inlet Temperature Condition (동일한 유입온도조건에서 R134a와 R22 적용 응축기의 특성비교)

  • Kang, Shin-Hyung;Byun, Ju-Suk;Kim, Chang-Duk
    • Journal of Energy Engineering
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    • v.15 no.3 s.47
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    • pp.166-173
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    • 2006
  • R134a is considered as an alternative refrigerant to R22 for air conditioners. An experimental investigation was made to study the characteristics of the heat transfer and pressure drop for R134a flowing in a fin-and-tube heat exchanger used for commercial air-conditioning units. Experiments were carried out under the conditions of inlet refrigerant temperature of $60^{\circ}C$ and refrigerant mass fluxes of $150,\;200,\;and\;250\;kg/m^{2}s$. The inlet air has dry bulb temperature or $35^{\circ}C$, relative humidity of 40% and air velocity varying from 0.68 to 1.6 m/s. Experiments show that air velocity decreased by 5.9% is needed for R134a than that of R22 while pressure drop for R134a was $18.1{\sim}20.4%$ higher than that of R22 for the degree of subcooling $5^{\circ}C$. The results are useful in designing more compact and effective condensers for various refrigeration and air conditioning systems using refrigerant R134a.

Study on the Performance of Heat Pump Using Non-azeotropic Refrigerant Mixtures R-22+R-114 (비공비혼합냉매 R-22+R-114를 이용한 열펌프의 성능에 관한 연구)

  • 박기원;구학근;오후규
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2131-2137
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    • 1993
  • This study, examines the performance and the heat pump cycle systematizing characteristics for non-azeotropic refrigerant systems. In order to conduct such an examination, the cycle characteristics of heat pumps for pure R-22, R-114, and their mixtures were experimentally investigated. The results show that cooling/heating capacities for the mixtures was more suited at the evaporating temperature of $5^{\circ}C$ than that of $0^{\circ}C$, $-5^{\circ}C$, and $-10^{\circ}C$. The C.O.P of the 50 wt% mixtures was considerably higher than for pure R-22, and the compression power of the 25 wt% was as much as 60% lower than that of pure R-22. Even small fractional mixture variations can lead to significant changes in the characteristics of the heat pump cycle. This experiment verified the importance of accurate weight fractions of refrigerant mixtures.

Effects of Temperature, Relative Humidity, and Leaf Wetness Period on the Development of Rice Leaf Blast (잎도열병(稻熱病) 발생(發生)에 미치는 온도(溫度), 상대습도(相對濕度) 및 잎표면상(表面上)의 수분존재시간(水分存在時間)의 영향(影響))

  • Choi, W.J.;Park, E.W.;Lee, E.J.
    • Korean journal of applied entomology
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    • v.26 no.4 s.73
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    • pp.221-228
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    • 1987
  • The optimum temperature range for conidial germination of Pyriculacia oryzae on a slide glass was $26{\sim}30^{\circ}C$, at which at least four hours of leaf wetness period was required to germinate. Conidial germination was significantly reduced under dry conditions (relative humidity<85%) at $34^{\circ}C$ but not at lower temperature (18, 22, 26, $30^{\circ}C$). Number of lesions developed were greater at $26^{\circ}C$ than at other temperature tested. The average leaf wetness period required for production of a lesion per plant was 22 hours at $18^{\circ}C$, 16 hours at $22^{\circ}C$, 10 hours at $26^{\circ}C$, and 8 hours at $30^{\circ}C$. Less than one lesion per plant occurred at $34^{\circ}C$ even under 24 hours of leaf wetness period. The time period between inoculation and lesion appearance was $7{\sim}8$ days at $18^{\circ}C$, $4{\sim}5$ days at $22^{\circ}C$ and $26^{\circ}C$, and $3{\sim}4$ days at $30^{\circ}C$. The time period required for lesion appearance after inoculation was not affected by leaf wetness period and relative humidity. Lesion length increased most rapidly at $30^{\circ}C$ during the first four days after lesion appearance. Thereater, the rate of increase in lesion length was geratest at $26^{\circ}C$. The average increment of lesion length per day when relative humidity was greater than 90% was 0.7mm at $18^{\circ}C\;and\;22^{\circ}C$, 1mm at $26^{\circ}C$, and 0.8mm at $30^{\circ}C$. When relative humidity was less than 85%, the increments of lesion length per day were approximately $50{\sim}60%$ of those under humid conditions (relative humidity>90%) at all temperature regimes except $30^{\circ}C$. Relative humidity did not significantly affected lesion length at $30^{\circ}C$.

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Condensation Heat Transfer of R22, R407C, and R410A in Slit Fin-and-Tube Heat Exchanger

  • Jeon, Chang-Duk;Lee, Jin-Ho
    • International Journal of Air-Conditioning and Refrigeration
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    • v.11 no.4
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    • pp.188-198
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    • 2003
  • R410A and R407C are considered to be alternative refrigerants of R22 for the air-conditioners. An experimental study is carried out to investigate the effect of the change of mass flow rate on the characteristics of heat transfer and pressure drop in three row slit finned-tube heat exchanger for R407C, R410A and R22. R407C, a non-azeotropic refrigerant mixture, exhibited a quite different condensation phenomenon from those of R22 and R410A and its condensation heat transfer coefficient was much lower than that of R22 and R410A. On the other hand, the condensation heat transfer coefficient of R410A, near-azeotropic refrigerant mixture, was a little higher than that of R22. R410A also showed the lowest condensation pressure drop across the test section. For all refrigerants, the condensation heat transfer coefficient and pressure drop increase as the mass flux increases. The condensation heat transfer coefficient correlation proposed by Kedzierski shows the best agreement with the experimental data within $\pm$20%.

Effect of Temperature on Development and Reproduction of the Emma Field Cricket, Teleogryllus emma(Orthoptera: Gryllidae)

  • Kim, Nam-Jung;Hong, Seong-Jin;Seol, Kwang-Youl;Kim, Seong-Hyun;Ahn, Nan-Hee;Kim, Mi-Ae
    • International Journal of Industrial Entomology and Biomaterials
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    • v.15 no.1
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    • pp.69-73
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    • 2007
  • To establish the indoor-rearing system of the emma field cricket, Teleogryllus emma, the effects of temperature on development and reproduction of the emma cricket have been studied. The influence of temperature on developmental periods of emma field cricket was investigated under the eight temperatures of 15, 18, 21, 25, 27, 29, 31 and $35^{\circ}C$, under $60{\pm}5%$ R.H. and 16L:8D photoperiod. The developmental periods of T. emma nymphs had a range of 124.8 days to 44.4 days at the temperature of $21^{\circ}C$ and $35^{\circ}C$, respectively. At $15^{\circ}C$ and $18^{\circ}C$, however, all tested individuals died before emergence. The highest survival rate was 90% at $25^{\circ}C$, but there were no statistically significant differences among the temperatures. The adult weight increased with increasing temperatures although the weight at $35^{\circ}C$ was decreased. In addition, the influence of temperature on reproduction of emma field cricket was investigated under three temperatures $22^{\circ}C,\;25^{\circ}C\;and\;28^{\circ}C$, under $60{\pm}5%$ R.H. and 16L:8D photoperiod. The longevity of female/male adults were 65.8/79.2 days, 68.5/67.8 days, 46.8/57.4 days at the temperature $22^{\circ}C,\;25^{\circ}C\;and\;28^{\circ}C$, respectively. The preoviposition periods were 32.5 days at $22^{\circ}C,\;22.9^{\circ}C$ days at $25^{\circ}C$ and 22.1 days at $28^{\circ}C$. The highest average fecundity per female was 737.3 at $25^{\circ}C$.

Studies on Lipids in Fresh-Water Fishes 7. Comparison of Lipid Components among Wild and Cultured Eel (Anguilla japonica), and Conger Eel (Astroconger myriaster) (담수어의 지질에 관한 연구 7. 천연 및 양식 뱀장어와 붕장어의 지질성분 비교)

  • CHOI Jin-Ho;RHIM Chae-Hwan;BAE Tae-Jin;BYUN Dae-Seok;YOON Tai-Heon
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.18 no.5
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    • pp.439-446
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    • 1985
  • This study was designed to compare the lipid components among wild and cultured eel, Anguilla japonica, and conger eel, Astroconger myriaster. The lipid components of cultured eel were analyzed and compared with those of wild and conger eel. In the content of total lipid, the lipid content in cultured eel was slightly higher than that in wild one, but 2 times higher than that in conger eel. The lipid contents in edible portion of wild and cultured eel were 5 times higher than those in viscera, but the lipid content in edible portion of conger eel showed a similar trend to that in viscera. In the fatty acid composition of neutral lipid in edible portion, percentages of $C_{14:0},\;C_{16:0}\;and\;C_{18:1}$ in cultured eel were higher than those in wild one, while percentages of $C_{16:1},\;C_{18:2},\;C_{18:3},\;C_{20:4},\;C_{20:5},\;C_{22:5}\;and\;C_{22:6}$ lower, and percentages of $C_{18:0},\;C_{20:4}\;and\;C_{22:6}$ in conger eel were noticeably higher than those in wild and cultured eels. In the case of phospholipid in edible portion, percentages of $C_{18:0}\;and\;C_{18:2}$ in cultured eel were higher than those in wild one, while percentages of $C_{16:0},\;C_{16:1},\;C_{18:1},\;C_{18:3},\;C_{20:4},\;C_{20:5},\;C_{22:5}\;and\;C_{22:6}$ lower. The unsaturation (TUFA/TSFA) of neutral lipid was no significant difference among wild and cultured eel, and conger eel, but that of phospholipid in wild eel was higher than that in cultured eel and conger eel. The essential fatty acid content(TEFA) of neutral lipid in edible portion of wild eel was 3 times higher than that of cultured one. but the TEFA of phospholipid in edible portion was no significant difference among wild and cultured eels, and conger eel. The w3 highly unsaturated fatty acid content (w3 HUFA) of neutral lipid in edible portion of wild eel was 2.0 to 2.5 times higher than that of cultured eel and conger eel, but the w3 HUFA of phospholipid in edible portion of wild eel was noticeably higher than that of cultured eel and conger eel. In the ratio (A/B) of fatty acid content (A) in cultured eel to that (B) in diet, the A/B ratios of $C_{18:2}\;w6,\;C_{18:3}\;w3,\;C_{20:5}\;w3\;and\;C_{22:6}\;w3$ were 0.23 to 0.48 much lower than the other fatty acid. Consequently, it is considered that the ratios of w3 HUFA is related to the biosynthesis of polyenoic acid and growth rate of cultured eel.

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Effects of Temperature and Day-Length on Heading Habit of Recently Developed Korean Rice Cultivars

  • Choi, Kyung-Jin;Lee, Jung-Il;Chung, Nam-Jin;Yang, Won-Ha;Shin, Jin-Chul
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.51 no.1
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    • pp.41-47
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    • 2006
  • To understand the heading habit of recently developed 20 Korean rice cultivars, rice plants in a phytotron were exposed to different temperature: $22.5^{\circ}C(day\;27^{\circ}C/night\;18^{\circ}C),\;27.5^{\circ}C(day\;32^{\circ}C/night\;23^{\circ}C)$, and day-length conditions: 10, 12, 13, 14, 15 hours. Four rice cultivars (Sobibyeo, Juanbyeo, Ilpumbyeo and Shindongjinbyeo) showed relatively short Basic Vegetative Phase (BVP) of 17 to 18 days, while Dasanbyeo showed the longest (35 days) BVP, compared to other remaining 15 tested cultivars which exhibited 24 to 31 days of BVP. In this experiment, it was tried out to separate the eliminable vegetative phase into photosensitivity and thermo-sensitivity with two different pathways. Many tested cultivars, however, exhibited quite different responses under low temperature and / or long day-length conditions. Especially, Surabyeo and Juanbyeo were the most difficult cultivars to separate into photo- or thermo-sensitivity in that the eliminable vegetative phase of these two cultivars increased greatly only under low temperature $(22.5^{\circ}C)$ and long day-length (15 hr.) conditions. Regarding the heading response to temperatures, tested cultivars could be categorized into 2 groups. In 1st group of rice cultivars, the eliminable vegetative phase decreased almost equally as the temperature changed from $20.0^{\circ}C\rightarrow22.5^{\circ}C\rightarrow25.0^{\circ}C\rightarrow27.5^{\circ}C$. In contrast, the 2nd group of rice cultivars exhibited eliminable vegetative phase slowly decreasing when the temperature changed from $22.5^{\circ}C\rightarrow25.0^{\circ}C\rightarrow27.5^{\circ}C$, but rapidly decreasing when the mean temperature changed from $20.0^{\circ}C\;to\;22.5^{\circ}C$. All the cultivars belonged to 2nd group, the heading date would be very delayed if cool summer comes.

The Changes of Pectic Substances During the Fermentation of Kimchis (김치의 숙성 과정에 따른 펙틴질의 변화)

  • 이용호;이혜수
    • Korean journal of food and cookery science
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    • v.2 no.1
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    • pp.54-58
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    • 1986
  • The changes of acidity, hardness, and pectic substances of Kimchis fermented at 6-1$0^{\circ}C$ and 22-24$^{\circ}C$ were investigated. With fermentation, acidity was increased and hardness was decreased, and these changes were more marked in Kimchis fermented at 22-24$^{\circ}C$. The contents of AIS was decreased with fermentation. Hot water soluble pectin was increased and protopectin was decreased with fermentation, but the amount of changes was small.

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