• Animal cells and systems
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• 제16권2호
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• pp.145-153
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• 2012

The pear psylla, $Cacopsylla$ $pyricola$ (Hemiptera: Psyllidae), is a serious insect pest of commercial pear crops. The species, which resides on pear trees throughout its life cycle, is rapidly spreading in some regions of the world. The population genetic structure of the species collected from several pear orchards in Korea was studied to understand the nature of dispersal and field ecology of the species. The 658-bp region of mitochondrial COI gene and the 716-bp long complete internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA were sequenced. Unlike other previously studied insect pests, the COI-based genetic diversity of the pear psylla was extremely low (maximum sequence divergence of 0.15%). This finding allowed us to conclude that the species may have been introduced in Korea relatively recently. ITS2 sequence-based analyses of phylogeny, population differentiation, gene flow, and hierarchical population structure all concordantly suggested that the pear psylla populations in Korea are neither genetically isolated nor hampered for gene flow. These genetic data are concordant with the dispersal of an overwintering winterform morph outside the non-pear habitat in the fall.

• The Korean Journal of Ecology
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• 제21권5_1호
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• pp.457.2-486
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• 1998

Ecological success of introduced species is frequently attributed to the reproductive characters of those species. We examined the relationship between both flowering season and plant size and reproductive characters in two introduced species of Taraxacum, e.g., T. officinale and T.laevigatum. Seventy six plants of T. officinale and 23 plants of T. laevigatum were randomly tagged from a population at the sungshin Women's University in April of 1997. The size and number of vegetative characters such as rosette diameter, leaf number, and the largest leaf length and width were measured for each plant at the onset of flowering. The infructescence was collected continually from each plant before seed dispersal from April to August of 1997. The number of infructescence per plant, and seed number and total seed weight per infructescence were measured. Mean individual seed weight per infructescence was also obtained. T. officinale possessed larger sized, but smaller number of, leaves than T. laevigatum, thereby resulting in no significant difference in total leaf area. There was a trend that vegetatively larger plants in both of these species produced reproductive characters larger in size or greater in number, except for seed number and total seed weight per infructescence in T. laevigatum. All reproductive characters examined in T. officinale decreased toward the end of flowering season. In T. laevigatum, infructescence number per plant also declined during a flowering season: however, mean seed number per infructescence increaed toward the end of flowering season with no significant seasonal change in the total seed weight per infructescence. T. officinale produced on average about twice as many seeds per plant as T. laevigatum during a growing season. These two Taraxacum species produced quite small seeds in size compared to the endemic species, exhibiting a far better dispersal ability of introduced species. These data demonstrate that most reproductive characters decline in size and number in both species during a long flowering period, but the two species appear to employ different strategies to achieve reproductive success in disturbed habitats.

• 식물분류학회지
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• 제40권3호
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• pp.157-162
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• 2010

우리나라의 울릉도와 독도에 분포하는 한국특산종인 섬기린초는 해안암석지대를 터전으로 넓게 분포하여 울릉도 생태계의 중요한 부분을 차지하고 있다. 본 연구는 섬기린초에 대한 엽록체 DNA의 trnL/F intergenic spacer 염기서열을 총 32개체에 대하여 조사하였다. 그 결과, 정렬된 염기서열 중 하나의 6-bp indel (-ATTCAC-)에 의하여 두 개의 type (TYPE01: 297bp과 TYPE02: 291bp)을 확인하였다. 확인된 두 개의 엽록체 DNA type은 울릉도와 독도에서 뚜렷한 지리적 분포양상을 보여주었다. TYPE01은 울릉도(15개체)에서만 관찰되었고 TYPE02는 울릉도(12개체)와 독도(5개체)에서 확인되었다. 섬기린초는 하나의 6-bp indel에 의하여 서로 다른 두 개의 엽록체 DNA haplotype이 확인되고 뚜렷한 지리적 분포양상을 보여주기 때문에, 울릉도와 독도에 자생하는 개체군 내에 진화적으로 서로 다른 두 개의 계통이 있음을 추정할 수 있고 울릉도와 독도 간 원거리 분산 기작의 가능성을 지지하였다.

• Animal cells and systems
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• 제3권1호
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• pp.29-39
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• 1999

Current data on reproductive characters of endemic and native species are essential to provide a strategy for the conservation of these species. Red pine (Pinus densiflora Sieb. & Zucc.) is one of the dominant, native tree species in Korea, but its reproductive ecology is not well-known. In 1997, the pattern of variation in cone and seed yields contributing to the conservation of declining populations of red pines was examined. Plant height and dbh were measured, and several new cones were collected from each tagged tree after counting the number of cones on each tree. For a subset of cones sampled, the number of fertile scales, the number of seeds at three development stages (early/late aborted, and filled seed), seed wing size, wing color, and individual filled seed mass were measured. The three sites which differed significantly in mean plant size also differed in mean cone and seed production per plant. However further analyses showed that most variation in characters examined occurred among plants within sites, but not among sites. An average of 90% of the potential seeds on the cones aborted at an early developmental stage, demonstrating that early abortion is a major factor affecting the number of filled seeds per cone. Individual seed mass was the only character which exhibited significant variations among sites as well as among trees within sites. Individual seed mass was overall negatively correlated with both the percentage of late abortion and the number of old cones per plant, suggesting that both the past and current years' reproductive activities have caused variations in seed mass. The potential dispersal distance of red pine seeds is quite large. However, wing loading was correlated with seed mass and number in a complex pattern across the sites. Distribution of seeds with varied colored wings differed among sites and among trees within sites. These results suggest that red pines at different sites might possess different strategies to cope with selection pressures acting during the final phase of reproduction, from seed dispersal to establishment. Then the ‘fitted’ red pine trees at each site should be identified and managed to conserve or restore populations.

• 한국환경과학회지
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• 제25권5호
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• pp.635-644
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• 2016

Birds play a main role in the formation and change of forest structures as they are seed-dispersal agents. This study aims to identify birds consuming fruits and seeds of the tree and their associated fruits and seeds on Jeju Island in the context on the forest restoration in Korea. We conducted field surveys twice a month from 2013 to 2015 at nine study sites located across Jeju Island and collected available photographic and observation records. A total of 50 species of birds consuming fruits and seeds of the tree were identified and birds belonging to Bombycillidae, Pycnonotidae, Zosteropidae, Sturnidae and Fringillidae were confirmed as major birds consuming fruits and seeds of the tree. Gulping was the dominant type of feeding as well as crushing, but relationship between the size of a bird and the number of fruit and seed species used by the bird was not significant. We also documented that 118 fruit and seed species were consumed by birds and that shrubby fruits and seeds were more consumed by birds than those of other plant types. The relative consumption rate of fruits and seeds ranged from 0.02 to 0.44, but five species were the most important fruits and seeds for birds. Our finding suggest that avian frugivorous gulpers will benefit the seed dispersal, especially of five fruiting plants, providing useful baseline data for forest restoration and urban park design.

• Nuclear Engineering and Technology
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• 제42권1호
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• pp.17-36
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• 2010

In this study, we compare the mass release rates of radionuclides(1) from waste forms arising from the KIEP-21 pyroprocessing system with (2) those from the directly-disposed pressurized-water reactor spent fuel, to investigate the potential radiological and environmental impacts. In both cases, most actinides and their daughters have been observed to remain in the vicinity of waste packages as precipitates because of their low solubility. The effects of the waste-form alteration rate on the release of radionuclides from the engineered-barrier boundary have been found to be significant, especially for congruently released radionuclides. the total mass release rate of radionuclides from direct disposal concept is similar to those from the pyroprocessing disposal concept. While the mass release rates for most radionuclides would decrease to negligible levels due to radioactive decay while in the engineered barriers and the surrounding host rock in both cases even without assuming any dilution or dispersal mechanisms during their transport, significant mass release rates for three fission-product radionuclides, $^{129}I$, $^{79}Se$, and $^{36}Cl$, are observed at the 1,000-m location in the host rock. For these three radionuclides, we need to account for dilution/dispersal in the geosphere and the biosphere to confirm finally that the repository would achieve sufficient level of radiological safety. This can be done only after we have known where the repository site would by sited. the footprint of repository for the KIEP-21 system is about one tenth of those for the direct disposal.

• 농업생명과학연구
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• 제45권6호
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• pp.89-94
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• 2011

본 연구는 상록활엽수림의 합리적인 관리를 위한 기초정보를 제공하기 위하여 동백나무림 주변 산림군집에 대한 상록활엽수종의 치수발생량과 종자산포량을 분석하였다. 치수밀도와 비율의 경우, 동백나무림과 동백나무림 가장자리, 동백나무림내 해송아래, 편백림에서 발생하는 전체치수의 약 90%이상이 동백나무를 포함한 참식나무와 후박나무, 광나무, 생달나무, 까마귀쪽나무, 돈나무 등의 상록활엽수류가 차지하고 있었으며, 특히 참식나무, 후박나무, 광나무는 동백나무림에서 200 m 정도 떨어진 해송림과 낙엽활엽수림에까지 밀도는 낮지만 치수발생이 이루어지고 있어 상록활엽수림으로 천이가 시작되고 있었다. 흉고 직경급 분포에서 동백나무는 역J자형의 분포를 나타내고 있었고 후박나무, 참식나무, 광나무는 뚜렷한 경향을 나타내지 않았다. 동백나무 종자는 동백나무림 주변 50 m 이내에 주로 산포되고 있는 것으로 조사되었다.

• 한국산업융합학회 논문집
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• 제27권2_2호
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• pp.437-443
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• 2024

The purpose of radiological Dispersal Device(RDD) is to kill people by explosives and to cause radiation exposure by dispersing radioactive materials. And It is a form of explosive that combines radioactive materials such as Co-60 and Ir-192 with improvised explosives. In this study, we tested and evaluated whether it was possible to read the internal structure of an explosive using X-rays in a radioactive explosive situation. The improvised explosive device was manufactured using 2 lb of model TNT explosives, one practice detonator, one 9V battery, and a timer switch in a leather briefcase measuring 41×35×10 cm³. The radioactive material used was the Co-60 source used in the low-level gamma ray irradiation device operated at the Advanced Radiation Research Institute of the Korea Atomic Energy Research Institute. The radiation dose used was gamma ray energy of 1.17 MeV and 1.33 MeV from a Co-60 source of 2208 Ci. The dose rates are divided into 0.5, 1, 2, and 4 Gy/h, and the exposure time was divided into 1, 3, 5, and 10 minutes. Co-60 source was mixed with the manufactured explosive and X-ray image reading was performed. As a result of the experiment, the X-ray image appeared black in all conditions divided by dose rate and time, and it was impossible to confirm the internal structure of the explosive. This is because γ-rays emitted from radioactive explosives have higher energy and stronger penetrating power than X-rays, so it is believed that imaging using X-rays is limited By blackening the film. The results of this study are expected to be used as basic data for research and development of X-ray imaging that can read the internal structure of explosives in radioactive explosive situations.

• 한국토양비료학회지
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• 제51권1호
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• pp.16-27
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• 2018

To predict the influence of volcano eruption on agriculture in South Korea we evaluated the dispersal ranges of the volcanic ashes toward the South Korea based on the possibilities of volcano eruption in Mt. Baekdu. The possibilities of volcano eruption in Mt. Baekdu have been still being intensified by the signals including magmatic unrest of the volcano and the frequency of volcanic earthquakes swarm, the horizontal displacement and vertical uplift around the Mt. Baekdu, the temperature rises of hot springs, high ratios of $N_2/O_2$ and $_3He/_4He$ in volcanic gases. The dispersal direction and ranges and the predicted amount of volcanic ash can be significantly influenced by Volcanic Explosivity Index (VEI) and the trend of seasonal wind. The prediction of volcanic ash dispersion by the model showed that the ash cloud extended to Ulleung Island and Japan within 9 hours and 24 hours by the northwestern monsoon wind in winter while the ash cloud extended to northern side by the south-east monsoon wind during June and September. However, the ash cloud may extent to Seoul and southwest coast within 9 hours and 15 hours by northern wind in winter, leading to severe ash deposits over the whole area of South Korea, although the thickness of the ash deposits generally decreases exponentially with increasing distance from a volcano. In case of VEI 7, the ash deposits of Daejeon and Gangneung are $1.31{\times}10^4g\;m^{-2}$ and $1.80{\times}10^5g\;m^{-2}$, respectively. In addition, ash particles may compact close together after they fall to the ground, resulting in increase of the bulk density that can alter the soil physical and chemical properties detrimental to agricultural practices and crop growth.

• 방사성폐기물학회지
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• 제5권3호
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• pp.199-212
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• 2007

IP-2형 운반용기는 정상운반조건에서의 자유낙하시험 및 적층시험을 수행한 후에 운반내용물의 분산 및 유실이 없어야 하며 외부표면에서의 방사선량률이 20%이상 증가할 수 있는 차폐능력의 상실이 없어야 한다. 본 연구에서는 두꺼운 철판을 구조재로 사용하며 볼트체결방식의 뚜껑을 가진 IP-2형 운반용기에 대한 구조 안전성을 평가하기 위한 해석적인 방안을 제안하였다. 해석적인 방법을 통하여 원자력발전소에서 발생된 방사성폐기물 드럼을 폐기물 처리시설에서 임시저장고까지 운반하기 위한 두 종류의 IP-2형 방사성폐기물 운반용기에 대하여 자유낙하조건에서 운반내용물의 분산 및 유실과 차폐손실이 없음을 확인하였다. 자유낙하조건에서 운반내용물의 분산 및 유실을 평가하기 위하여 최대 볼트단면 평균응력값과 최대 뚜껑열림량을 볼트의 인장강도와 뚜껑부에 존재하는 단차와 비교 평가하였다. 또한 최대 차폐두께 감소량을 이용하여 차폐손실을 평가하였다. 자유낙하조건에 대한 동적충돌해석을 검증하고 구조 안전성을 시험적으로 평가하기 위하여 자유낙하시험을 다양한 방향으로 실시하였다. 자유낙하시험에서는 운반내용물의 분산 및 유실은 볼트체결방식의 뚜껑에서 볼트의 파손 및 플랜지의 변형 등을 검사하여 평가하였으며, 차폐손실은 초음파 두께 측정기를 이용한 차폐두께를 측정하여 평가하였다. 해석에 대한 검증을 위하여 시험에서 취득한 변형률과 가속도를 동일한 위치에서 얻어진 해석결과와 비교하였다. 해석결과는 시험결과에 비하여 보수적인 결과를 보여주므로 해석에서 입증한 IP-2형 방사성폐기물 운반용기의 안전성은 보수적인 결과이다. 마지막으로 유한요소해석을 통하여 적층조건에 대한 IP-2형 방사성폐기물 운반용기는 안전함을 입증하였다.