• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.316-326
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• 2014

Determination of the late marginal heading date (LMHD), which would allow estimation of the late marginal seeding date and the late marginal transplanting date, would help identification of potential double cropping areas and, as a result, establishment of cropping systems. The objective of this study was to determine the LMHD at 51 sites in Korea. For these sites, weather data were obtained from 1971 to 2000 and from 1981 to 2010, which represent past and current normal climate conditions, respectively. To examine crop productivity on the LMHD, climatic yield potential (CYP) was determined to represent the potential yield under a given climate condition. The LMHD was calculated using accumulated temperature for 40 days with threshold values of $760^{\circ}C$, $800^{\circ}C$, $840^{\circ}C$ and $880^{\circ}C$. The value of CYP on a given LMHD was determined using mean temperature and sunshine duration for 40 days from the LMHD. The value of CYP on the LMHD was divided by the maximum value of CYP (CYPmax) in a season to represent the relative yield on the LMHD compared with the potential yield in the season. Our results indicated that the LMHD was delayed at most sites under current normal conditions compared with past conditions. Spatial variation of the LMHD differed by the threshold temperature. Overall, the minimum value of CYP/CYPmax was 81.8% under all of given conditions. In most cases, the value of CYP/CYPmax was >90%, which suggested that yield could be comparable to the potential yield even though heading would have occurred on the LMHD. When the LMHD could be scheduled later without considerable reduction in yield, the late marginal transplanting date could also be delayed accordingly, which would facilitate doublecropping in many areas in Korea. Yield could be affected by sudden change of temperature during a grain filling period. Yet, CYP was calculated using mean temperature and sunshine duration for 40 days after heading. Thus, the value of CYP/CYPmax may not represent actual yield potential due to change of the LMHD, which suggested that further study would be merited to take into account the effect of weather events during grain filling periods on yield using crop growth model and field experiments.

• Korean Journal of Agricultural and Forest Meteorology
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• v.20 no.4
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• pp.284-295
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• 2018

The safe and late marginal heading dates (SMHD, LMHD), cropping probability, and growth duration of rice were assessed using temperature data in the 27 regions of North Korea. The medians of SMHD and LMHD ranged Jul. 16 and Jul. 27 in Hyesan to Aug. 18 and Aug. 28 in Haeju, respectively, except Changjin, Pungsan, and Samjiyon that did not show any of the SMHD and LMHD. The medians of the days from early marginal transplanting date (EMTD) to heading date ranged 51 days in Hyesan to 109 days in Pyongyang for SMHD and those were delayed by 9~15 days for LMHD, compared to SMHD. Nineteen regions (Kaesong, Haeju, Yongyon, Singye, Sariwon, Nampo, Pyongyang, Anju, Kusong, Sinuiju, Changjon, Wonsan, Hamhung, Pyonggang, Yangdok, Huichon, Supung, Sinpo, Kanggye) and additional four regions (Kimchaek, Chongjin, Sonbong, Chunggang) had the rice cropping probability higher than 80% when analyzed based on the SMHD and LMHD, respectively. The representative SMHD ranged Jul. 24 for Pyonggang to Aug. 12 for Haeju. Compared to the days from EMTD to SMHD, those from EMTD to LMHD were delayed by 9~17 days. When applied SMHD, thirteen regions (Yangdok, Kanggye, Huichon, Supung, Yongyon, Kusong, Anju, Sinuiju, Singye, Pyongyang, Kaesong, Nampo, Sariwon) had the appropriate range of cumulative temperature during grain filling (CT) for grain yield and quality. Sinpo, Hamhung, Pyonggang, Wonsan, Changjon, and Haeju had the CT higher than $1,300^{\circ}C$. It is supposed that rice cropping could be extended to the regions where LMHD-applied cropping probability was higher than 80%. Delaying the heading date than SMHD could be also considered in the regions where the days to SMHD is small but CT is large.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.317-322
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• 2008

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchanger with R410A for Gas Engine Driven Heat Pump (GHP) application and to find optimum design conditions of indoor heat exchanger by parametric analysis for the key parameters. In the air side, moisture out of the humid air condenses on the fin surface while the refrigerant (R410A) boils inside the smooth tube. Therefore this study uses Log Mean Enthalpy Difference (LMHD) method to analyze the heat transfer from the humid air to the refrigerant of R410A. The results show that fin pitch and longitudinal pitch have significant effect on the heat exchanger preformance. This study will provide the guideline for optimum design of indoor heat exchanger with R410A for GHP application.

• International Journal of Air-Conditioning and Refrigeration
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• v.17 no.4
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• pp.129-134
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• 2009

The objectives of this paper are to study the effects of thermal and geometric conditions on the performance of indoor heat exchangers with R-410A for Gas Engine Driven Heat Pump (GHP) application and to find the optimum design conditions of indoor heat exchangers by parametric analysis for the key parameters. The key parameters are number of tube row, number of tube pipe, fin pitch and transverse tube pitch. In the air side, moisture out of the humid air condenses on the fin surface while the refrigerant (R-410A) boils inside the smooth tube. Therefore this study uses Log Mean Enthalpy Difference (LMHD) method to analyze the heat transfer from the humid air to the refrigerant. This study determines the heat exchanger size, air side/refrigerant side pressure drop and overall heat transfer coefficient. Optimum design conditions for the key parameters are also determined by the parametric analysis. The results show that number of rows and pipes, fin pitch have significant effect on the heat exchanger size. It is also found that the tube length of the louver fin is $17{\sim}30%$ shorter than that of the plate fin.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.3
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• pp.190-200
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• 2021

The heading response of rice varieties, originated from South Korea, North Korea, and northern China, was examined under the temperature and day-length conditions of 10 low-temperature regions in North Korea. When 30-day-old broadcast tray-raised seedlings (BS) were used, only one or a few varieties reached the heading stage within the safe marginal heading date (SMHD) under the Hamhung, Pyonggang, Huichon, and Kanggye conditions. In the Yangdok and Sinpo environments, no varieties reached heading until SMHD. The South Korean varieties that reached the heading stage between SMHD and late marginal heading date (LMHD) were Jinbuol, Baegilmi, Joun, Jopum, Jinok, Jopyeong, Sanhomi, and Odae for the Hamhung, Pyonggang, Huichon, and Kanggye; Joun for Sinpo; and none for Yangdok, Kimchaek, Sonbong, and Chunggang environments. The number of days to heading (DTH) was positively correlated among all 10 regions. Reduced DTH in the 30-day-old pot tray-raised seedlings (PS), compared to BS, was not consistent with varieties and regions. Reduced DTH in PS, compared to BS, was the largest in Jinok and Sonbong9 among the South and North Korean varieties, respectively, whereas it was small in the northern Chinese varieties. The South Korean varieties that headed until SMHD in PS were Jinok for the Hamhung, Pyonggang, Yangdok, Sinpo, and Kanggye environments; and Jinbuol, Jopum, and Jinok for the Huichon condition. In the Kimchaek and Chunggang conditions, Jinok reached the heading stage within LMHD. With the use of PS for some responsive varieties such as Jinok, varietal adaptability could be improved to the conditions of low-temperature regions in North Korea. None of the PS or BS among the tested varieties reached the heading stage until LMHD for the Chongjin and Sonbong conditions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.68 no.4
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• pp.236-245
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• 2023

We investigated the basic vegetative phase (BVP), photoperiod-sensitivity (PS), and thermo-sensitivity (TS) of 40 rice varieties to characterize their heading ecology that is adaptable to North Korean rice production areas. The ranges were 12 - 43 days for BVP, 0 - 74 days for PS, and 15 - 33 days for TS, depending on the variety. The number of days from transplanting to the heading stage (DTH) was significantly correlated with PS in the 13 major rice production regions where all 40 varieties (including early-, middle-, and mid-late-maturing varieties) were tested. DTH was significantly correlated with BVP and TS but not with PS in the 10 low-temperature regions where only 28 early-maturing varieties were tested. The heading ecology of the adaptable varieties for each region could be characterized by an exponential equation between the BVP and PS of varieties that headed at the border of the safe marginal heading date (SMHD) for each of the seven regional environments (Kaesong, Haeju, Yongyon, Singye, Sariwon, Nampo, and Pyongyang). A PS of 25 - 30 days or less was an additional adaptive trait in the Sariwon and Pyongyang environments. The varieties that reached the heading stage not later than the SMHD in six regional environments (Anju, Kusong, Sinuiju, Changjon, Wonsan, and Supung) and those that reached the heading stage not later than the late marginal heading date (LMHD) in four regional environments (Hamhung, Pyonggang, Huichon, and Kanggye) had both a PS of 26 days or less and a BVP of 25 - 28 days or less. In the Yangdok, Sinpo, and Chunggang environments, varieties that reached the heading stage not later than the LMHD for each region had a BVP of 15 - 20 days or less. The results suggested that a shortened BVP trait should be introduced to existing early-maturing rice varieties to reduce the duration of growth period to reach the heading stage.