• The Korean Journal of Malacology
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• v.11 no.2
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• pp.147-163
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• 1995

The unionid family Unionidae contains several genera in Korea, among which occru considerable variations in life histories and sexual conditions. Seven species from the Korea(Anodonta arcaeformis flavotincta, A. woodiana, Unio douglaseae, U. douglasiae sinuolatus, Lamprotula gottschei, Lanceolaria acrorhyncha, Solenaia triangularis)were stueide in order to identify and describe the seasonal gonadal activity and the visceral sex. The gonads of seven species were histologically examined by using the paraffin block technique for sectioning. All seven species were uniformly dioecious and testicular activity in six species except one species, S. triangularis, generated sperm-morulae(multinucleated cell). The annual reproductive cycle of the seven species could be classified into five successive stages; multicative, growing, mature, spent, deginerative and resting stages. The breeding season of six species was the summer and that of A. a. flavotincta was the winter.

• The Korean Journal of Zoology
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• v.37 no.3
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• pp.311-317
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• 1994

Seasonal variations of GnRH were investigated by immunohlstochemicsl technique in three species of frog, Rona niEromaculutu, R. dvbowskii 8nd R. mgosa with different ovulation period in order to examine the relationship between GnRH expression and reproductive function. In all three species of frog, the intensity of GnRH immunoreactivitv and the number of GnRH neurons in the brawn were relatively high in frogs at the pre-ovulation period and markedly increased at the ovulation period. Those were then decreased after ovulation and further lowered during early hibernation period. These results indicate that GnRH experssion is closely related to specific phases of annual reproductive cycle in frog.

• Journal of Plant Biology
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• v.2 no.1
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• pp.1-7
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• 1959

As no reference to the seasonal variations in the mosquito population of the country has been noted in the past literature and as such a survey is apparantlyprequite to insecticidal orerations, an observat on of the subject may be ofvalue. The investigation was made te different geographical locations during theperiod from March 1952 to Jul 1956 In order to obtain as accurte an averagepicture as pasaible of the country, the locations Covered geograpically such scat-tered lropertions as could represent a balance 1croverage : S_oui, kangoongNational Forestry, Incheon, Gunaa , Uejiongbu, Chungcheon, Wonju, Taegukangnoong of the eastcoast,pohang Pusan, Masan and two islands of Chejudo andPaeckyongdo. The total of approximately 3620 larval coll ctions r.corded fromthe check points described above were divided s follows ; sexul area, 950 larvae;Kangnoong National Forestry, 850 larae; Pusan area. 520 larvae; other loations,700 larvae In mosquito to adult collactions 134 light traps (new Jersey type)and 67biting collections were performed.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.38.2-38.2
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• 2009

The ionosphere displays variations on a wide variety of time-scales, ranging from few hours to days and up to solar cycles and even more. In this paper, we examine the ionospheric F2-layer variability in mid latitude by analyzing the foF2 and hmF2 from the Anyang ionosonde. Especially, we investigate how ionospheric semi-annual and seasonal anomalies vary with local time and solar activity. In addition to the characterization of the ionospheric semi-annual an seasonal anomalies, our study extends to the investigation of the relationship between ionospheric variability and geomagnetic activity. Finally we also discuss the coupling between ionospheric F2-layer variability and thermospheric neutral composition.

• Natural Product Sciences
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• v.27 no.4
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• pp.280-283
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• 2021

Cercidiphyllum japonicum is being used for the treatment of obesity and liver fibrosis in Korean local clinics. In the present study, we tried to develop an analytical methodology for the determination of the chemical markers of Cercidiphyllum japonicum. Four chemicals, maltol (1), chlorogenic acid (2), quercetin (3), and avicularin (4), were selected for method validation, and the analytical conditions were optimized and validated using high-performance liquid chromatography coupled with an ultraviolet detector (HPLC-UV). Additionally, the seasonal variations of four markers were monitored every month for six months. The contents of four chemicals markers were most detected in a sample collected in June.

• Ocean and Polar Research
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• v.44 no.2
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• pp.179-190
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• 2022

Data missing in optical satellite images caused by natural variations have been a crucial barrier in observing the status of marine surfaces. Although there have been many attempts to fill the gaps of non-observation, there is little research to analyze the ratio of missing grids to overall sea grids and their seasonal patterns. This report introduces the method of quantifying the distribution of missing points and then shows how the missing points have spatial correlation and seasonal trends. Both temporal and spatial integration methods are compared to assess the effectiveness of reducing missing data. The temporal integration shows more outstanding performance than the spatial integration. Moran's I and K-function with statistical hypothesis testing show that missing grids are clustered and there is a non-random distribution from daily integration. The result of the seasonality test for Moran's I through a periodogram shows dependency on full-year, half-year, and quarter-year periods respectively. These analysis results can be used to deduce appropriate integration periods with permissible estimation errors.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.3
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• pp.41-48
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• 1965

This study was aimed at knowing the magnitude of year variation in rice heading dates under the different seasonal cultures, and to estimate the heading date in advance. Using six rice varieties such as Kwansan, Suwon＃82, Suwon ＃144, Norin＃17, Yukoo＃132 and Paltal, the early, ordinary and late seasonal cultures had been carried out at Paddy Crop Division, Crop Experiment Station at Suwon for the six-year period 1959 to 1964. In addition the data of the standard rice cultures at the Provincial Offices of Rural Development for the 12-year period 1953 to 1954, were analyzed for the purpose of clarifying a relationship between variation of rice heading dates and some of meteorological data related to the locations and years. The results of this study are as follows: 1. Year variation of rice heading dates was as high as 14 to 21 days in the early seasonal culture and 7 to 14 days in the ordinary seasonal culture, while as low as one to seven days in the late seasonal culture which was the lowest among three cultures. The magnitude of variation depended greatly on variety, cultural season and location. 2. It was found out that there was a close negative correlation between the accumulated average air temperature for 40 days from 31 days after seeding and number of days to heading in the early seasonal culture. Accordingly, it was considered possible to predict the rice heading date through calculation of the accumulated average air temperature for the above period and then the linear regression(Y=a+bx). On the other hand, an estimation of the heading date in the late seasonal culture requires for the further studies. In the ordinary seasonal culture, no significant correlation between the accumulated average air temperature and number of days to heading was obtained in the six-year experiments conducted at Suwon. There was a varietal difference in relationship between the accumulated average air temperature for 70 days from seeding and number of days to heading in the standard cultures at the provincial offices of rural development. Some of varieties showed a significant correlation between two factors while the others didn't show any significant correlation. However, there was no regional difference in this relationship.

• Korean Journal of Ecology and Environment
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• v.52 no.1
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• pp.40-49
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• 2019

Seasonal succession of zooplankton community and species composition was studied from 2003 to 2014 in a deep reservoir, Lake Soyang, in monsoon climate region, Korea. Annual precipitation was concentrated more than 70% between June and September and it showed remarkably that seasonal variation in water quality. Seasonal variation of water quality in Lake Soyang appeared to be more significant than annual variations, and the inflow of turbid water during the summer rainfall was the most important environmental factor. Zooplankton sepecies composition in Lake Soyang showed obvious tendency through two periods (May to June and August to October) every year. Small zooplankton (rotifer; Keratella cochlearis, Polyarthra vulgaris) dominated in spring and mesozooplankton such as copepods and crustaceans were dominant in summer and fall. Zooplankton biomass showed the maximum in September after monsoon rainfall, and chlorophyll showed a similar seasonal variation and it showed a high correlation (r=0.45). The increase of zooplankton biomass is considered to be a bottom-up effect due to the increase of primary producers and inflow of nutrients and organic matter from rainfall. In this study, we found that the variation of zooplankton community was affected by rainfall in monsoon climate region and inflow of turbid water was an important environmental factor, which influenced the water quality, zooplankton seasonal succession in Lake Soyang. It was also considered to be influenced by hydrological characteristics of lake and environment of watershed. In conclusion, seasonal succession of zooplankton species composition was the same as the PEG model. But seasonal succession of zooplankton biomass differed not only in the temperate lake but also in the monsoon region.

• Journal of Astronomy and Space Sciences
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• v.19 no.2
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• pp.123-132
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• 2002

The electron density and temperature in the topside ionosphere are observed by the ionosphere Measurement Sensor (IMS) onboard the KOMPSAT-1, which has the sun-synchronous orbit of the altitude of 685 km and the orbital inclination of $98^{\circ}$ with a descending node at 22:50LT. Observations have been analyzed to determine the seasonal variations of the electron density and temperature in the low-latitude region. Only the night-time (22:50LT) behavior on magnetically quiet days (Kp < 4) has been examined. Observations show a strong longitudinal and seasonal variation. Generally, in the dip equator the density increases and the temperature decreases. In equinox the latitudinal distributions of the electron density and temperature are quite symmetric about the dip equator. However, the local maximum of the density and the local minimum of the temperature shift toward the Northern hemisphere in summer solstice but the Southern hemisphere in winter solstice. Such variations are due to the influences of field-aligned plasma transport induced by F region neutral wind. Compared with the IRI95 model, the observed electron density and temperature show significant differences from those predicted by the IRI95 model.

• Korean Journal of Ichthyology
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• v.9 no.1
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• pp.48-60
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• 1997

The species composition and seasonal variations of fish community in the Zostera marina belt at the coastal water off Hamduck, northern part of Cheju Island, were analyzed based on day and night samples collected by a small beam trawl from May 1993 to May 1994. The dominant species among the 58 fish species in 35 family were tubesnout, Aulichthys japonicus, gobie, Pterogobius zonoleucus, filefish, Rudarius ercodes, pipefish, Syngnathus schlegeli and sea catfish, Plotosus lineatus. These species comprised 86.1% in the number of individuals and 62% in biomass. The number of individuals and biomass were high between October and December, and low between January and April. About 90% of fishes were noncommercial and small-sized fishes, less than 14cm in total length. The larvae and juvenile fishes were collected in the study area throughout the year. The recruitments of dominant species were related to the seasonal variations of Z. marina utilized as a shelter or feeding ground. A japonicus, P. zonoleucus, Zoarchias glaber and Hexagrammos agrammus recruited between January and June, and R. ercodes, S. schlegeli, P. lineatus and Petroscirtes breviceps between July and December.