• Journal of Ecology and Environment
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• v.30 no.2
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• pp.121-126
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• 2007

We monitored gold-spotted pond frog (Rana chosenica) populations near the Korea National University of Education in Chungbuk, Korea, from 19 May to 8 August, 2006 to examine the spatial distribution of populations in local areas and to investigate patterns of migration of adult gold-spotted pond frogs from terrestrial hibernation sites to breeding sites, We captured individuals from the largest population using a drift fence with 22 pitfall traps surrounding the breeding site. A total of 22 individuals (19 males and 3 females) were captured between 23 May and 15 June. No peak in breeding migration was detected, but the onset of the breeding migration may correspond with increased humidity. Male body weights were negatively correlated with sampling dates. Seven of 22 individuals were captured at the 4th pitfall trap, which was placed between two culverts. The capture rate per pitfall trap was higher in traps close to the rice field banks (1.44, traps $1{\sim}9$) than in traps facing hilly land (0.33, traps $13{\sim}18$). Comparative data from the Korean frog (Rana coreana), a sympatric species in the study area, were also collected and compared with those of the gold-spotted pond frog.

• ALGAE
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• v.17 no.1
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• pp.1-9
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• 2002

Diel vertical distribution of phytoflagellates and interactions between the phytoplankton components and environmental and biological factors were studied in a small artificial pond for three days on the December 18, 1998 and April 9 to 10, 1999. The phytoplankton population was dominated by Mallomonas akrokomos of chrysophytes and Cryptomonas marssonii and Chroomonas sp. of cryptophytes. The vertical distribution of these phytoflagellates taxa exhibited clear diel migration pattern. Moreover their migration patterns are showed differential fluctuation between M. akrokomos, C. marssonii and Chroomonas sp. The later two species upward migrated in the evening as well as night, whereas the former species migrated downward. Their distinctive migration pattern was found during the night but was not observed in the morning. During daytime C. marssonii and Chroomonas sp. showed maximum density above 2 m depth but M. akrokomos below 2 m depth. The diel vertical distribution of the dominant phytoflagellates did not show significant correlation between physical, chemical and biotic factors.

• The Korean Journal of Community Living Science
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• v.20 no.2
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• pp.193-204
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• 2009

Although the majority of elderly are residentially stable, many western studies have recently reported that there has been a gradual growth of retirement migration. However, little is known about that in Korea. Therefore, this study intended to examine the trend and nature of elderly migration. For this purpose, inter- and intra-province migration among the aged 65 and over were analyzed, using the migration data of the Korea National Statistical Office, compiled from the 2000 and 2006 resident registration records. The results were as follows. First, there was an increase of elderly migrants to 531 thousand persons in 2006 from 383 thousand persons in 2000. Secondly, the migration rate of elderly has steadily grown with a 11.7% in 2000 and 12% in 2006. Also, the move of female among old population was active but this trend tended to decrease in 2006. Thirdly, the number of provinces which showed a positive net inter-province migration of old population increased from 7 provinces in 2000 to 8 provinces in 2006. Fourthly, we found that the destinations of elderly migrants were mostly neighboring province except the Chungnam, Jeonbuk, and Jeju. These results suggested that elderly migration would be expected to increase gradually and be important in the future of Korea.

• Journal of the Korean association of regional geographers
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• v.15 no.5
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• pp.572-589
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• 2009

To grasp the migration characteristics of the Busan metropolitan area(BMA), this study analyzed the change of population and households, and the migration at the intra-regional and inter-regional scales. The major findings of the study are as follows: First, the ratio of population and households of the BMA to the whole country has continuously decreased, especially those 25 to 39 years of age greatly decreased. Second, the ratio of intra-regional migration is relatively high, and the ratio of inter-regional migration is relatively low in the BMA compared to the Seoul metropolitan area. Thus, Busan seems to be less integrated with the urban fringe. Third, the out-migration towards the Seoul metropolitan area from Busan has increased, so that Seoul metropolitan area becomes to have more considerable influence upon the population decrease in Busan.

• Animal cells and systems
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• v.14 no.4
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• pp.297-303
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• 2010

To document the basic ecological aspects of Chaoborus species, which has never been reported in Korea, we attempted to identify the species, to monitor seasonal and vertical dynamics, and to elucidate trophic relations of the species in Sang-Chun reservoir. Using morphological characteristics, we identified the collected samples as C. flavicans. Also, we compared the distribution of C. flavicans, Daphnia rosea and chlorophyll a to observed seasonal dynamics. The increase of C. flavicans was observed 1-2 weeks after the increase of D. rosea. Survey of diel vertica migration patterns in the summer season showed that C. flavicans were in hypolimnion at daytime, but moved to the epilimnion at night. Finally, to determine trophic relationships in Sang-Chun reservoir, additional studies on the food web were undertaken by stable isotope analysis. Chaoborus flavicans I-II instars appear to be filter feeders based on carbon isotope values. Trophic levels of C. flavicans III-IV instars were shown to be higher than other zooplankto based on nitrogen isotope values.

• Journal of Applied Reliability
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• v.12 no.3
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• pp.153-163
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• 2012

Recently, as a electronic components are becoming more high-density, so that electronic circuits have smaller pitches between the leads and are more vulnerable to insulation failure. And the reliability of electric insulation has become an ever important issue as device contact pitches and print patterns shrink. Ion migration occurs in highly humid environment as voltage is applied to an installed print circuit. Under highly humid and voltage applied circumstances, electronic components respond to applied voltages by electrochemical ionization of metals, and a conducting filament forms between the anode and cathode across a nonmetallic medium. This leads to short-circuit failure of the electronic component. In thesis, we study acceleration test of ion migration in FR-4 PCB plated with Sn. Voltage applied test of FR-4 PCB circuits plated with Sn was tested in the temperature and humidity environments. As a result of this test, equation of acceleration model was derived.

• Korean Journal of English Language and Linguistics
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• v.3 no.1
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• pp.15-36
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• 2003

This paper investigates the patterns of language choice among bilingual Korean students in New Zealand and presents the findings by the individual variables which influence their language behaviour. Respondent variables such as gender, present age, age at migration, region, and duration of residence were adopted as frames of analyses as they were thought to bring us macro-sociolinguistic features of language behaviour in a broad sense. A total of 177 primary to tertiary students from three regions of New Zealand (Auckland, Wellington, and Christchurch) were surveyed to find out characteristics of their language choice patterns with diverse interlocutors in a wide range of contexts. It was found that the younger AAM (age at migration) group showed a greater shift towards English. In addition, the longer the respondents had resided in New Zealand the more they used English. The results also revealed that females generally used less English and were more flexible choosing either Korean or English according to the situation. The younger respondents were using more English in some exceptional contexts where tertiary students were ahead of secondary students. Respondents from Wellington, on the whole, shifted towards English more than others from Auckland, and Christchurch. From these findings some implications are suggested for Korean students, teachers, researchers, and the government not only in New Zealand but also in Korea.

• Journal of the Korean Geographical Society
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• v.43 no.4
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• pp.561-579
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• 2008

The population concentration in Seoul has caused the chronic housing shortage. Accordingly the new towns in the Capital region were developed to alleviate overcrowding conditions in Seoul. The purpose of this study is to analyze changes of migration and commuting patterns according to new town development in the Capital region for the period of $1995{\sim}2005$. Further this study examines the changes of self-sufficiency level for new towns using jobs to housing ratio. During the last 10 years, the migration pattern in the Capital region has been pretty much followed the new town development. Such a migration pattern has influenced the commuting patterns, expanding the Seoul Metropolitan Area into northeastern par of the Capital region. The result reveals that self-sufficiency levels of new towns have become higher over the period of $1995{\sim}2005$, indicating that new towns are gradually strengthening their economic functions and have potential to become new business centers in the future. Therefore, the policy focusing on the increase of the job-housing balance ratio and self-sufficient level in new towns will be a desirable policy alternative to solve the transportation problems in the Capital region.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.58-66
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• 2009

The telemetry of eight adult manchurian trouts (Brachymystax lenok tsinlingensis) in the upper part of the Nakdong River, which is the southern limit of distribution of manchurian trout on the Korean peninsula, was used to examine migration patterns and evaluate characteristics of over-wintering and the spawning season between December, 2007 and May, 2008. Based on the tracking data, the tagged fish showed a limited migration between adjacent pools, moving only up to $8.6m\;day^{-1}$ during the winter season (December to February). Hydraulic conditions of over-wintering pool areas were, ca. 1m depth, slow moving surface water with areas of sand and gravel. The migration of tagged individuals was successful, moving up to $96.2m\;day^{-1}$ during the spawning season. Two tagged individuals (BL4, BL6) exhibited upstream migration, whereas others showed downstream movements. The timing of upstream migration of the two individuals was consistent with an increasing phases of water level and discharge. The fishes migrating toward the down stream moved to the wide pool areas downstream, where they spent the summer season for the growth.

• Korean Journal of Environmental Biology
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• v.40 no.1
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• pp.25-53
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• 2022

In this study, trends in research methods and topics of seabird and marine fish migration were examined. Based on the framework of existing animal migration studies, future research directions were proposed in relation to the migration of seabirds and fish. In terms of research methodology, with the development of science and technology, tracking techniques using radio telemetry, acoustic telemetry, RFID (radio-frequency identification), satellite tracking, and geolocators are widely used to study seabird and fish migration. Research is also conducted indirectly through a population survey and the analysis of substances in the body. Research contents are largely classified into extrinsic factors that affect migration(such as environmental variables and interspecific competition), intrinsic factors such as hormones, anthropogenic activities including fishery and offshore wind farm, and the effect of global climate change. In future studies, physiological factors that influence or cause migration and dispersal should be identified concerning intrinsic factors. For the analysis of migration ability, it is necessary to study effects of changes in the magnetic field on the migration ability of seabirds and fish, interspecific differences in spatiotemporal migration ability, and factors that influence the migration success rate. Regarding extrinsic factors, research studies on effects of anthropogenic disturbances such as fishery and offshore wind farm and global climate change on the migration and dispersal patterns of marine animals are needed. Finally, integrated studies on the migration of seabirds and fish directly or indirectly affecting each other in various ecological aspects are required.