• Archives of Craniofacial Surgery
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• v.19 no.3
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• pp.190-193
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• 2018

Background: This study was conducted to determine the effect of the distributional relationship between dental roots and the mandibular bone on single mandibular bone fractures, which are common craniofacial fractures. Methods: This was a retrospective, single-center study in Seoul, Korea. Patients with single mandibular fractures in the symphysis, parasymphysis, body, and angle area, with tooth structure involvement were included. The control group included patients with simple, bone-level lacerations without fractures. In total, 94 patients (72 males and 22 females) were included in the treatment group, and 125 (71 males and 54 females) were included in the control group. The height of the mandibular bone and the dental root were measured with panoramic radiography. The central incisor represented the symphysis area, the canine represented the parasymphysis area, the first molar represented the body area, and the second molar represented the angle area. Results: In the treatment group, symphysis fractures occurred in 16 patients (17%), parasymphysis fractures in 36 patients (38%), body fractures in 17 patients (18%), and angle fractures in 25 patients (27%). The ratios of the dental roots to the total height of the mandibular bone in the treatment group were 30.35%, 39.75%, 39.53%, and 36.27% for symphysis, parasymphysis, body, and angle areas, respectively, whereas in the control group, they were 27.73%, 39.70%, 36.76%, and 35.48%. The ratios of the treatment group were significantly higher than those of the control group. Conclusion: The results show that the higher ratio of the dental root to the height of the mandibular bone increases the fracture risk.

• Korean Journal of Plant Taxonomy
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• v.48 no.4
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• pp.278-288
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• 2018

Polyploidization plays an important role in generating the current high diversity of plants. Studies of the distributional patterns of diploid and derivative polyploid races have provided important insights into the evolutionary process and cryptic speciation by polyploidization within and between closely related taxa defined on the basis of their morphology. Allium thunbergii and A. sacculiferum, occurring throughout eastern Russia, eastern China, Korea, and Japan, are examples of closely related species with unsolved taxonomic relationships. A total of 97 and 65 individuals from 26 and 13 populations of A. thunbergii (including var. thunbergii, var. deltoids, and var. teretifolium) and A. sacculiferum, respectively, were studied to determine their ploidy. The geographic structure and habitat differentiation of the cytotypes were also analyzed. The main cytotype of A. thunbergii was diploid (92.3% in total; the rest were tetraploids). In contrast, the majority of A. sacculiferum plants were tetraploids (69.2% of the total; the rest were diploids). No populations of the studied taxa harbored both cytotypes. Allium thunbergii was more often found at higher elevations than A. sacculiferum, and it tended to occur more frequently on rocky slopes and below forests in mountainous areas. On the other hand, A. sacculiferum occurred at forest margins and in lowland pastures. The cytotypes differed with respect to the elevation; diploids were found more frequently at higher elevations than tetraploids. The results of this study and additional biosystematics data indicate that the morphological characteristics of A. thunbergii and A. sacculiferum may be influenced by polyploidization and by their adaptation to various habitat conditions and that A. thunbergii and A. sacculiferum do not clearly fulfill the requirements of any species concept. Consequently, we propose that A. sacculiferum be considered as an additional synonym of A. thunbergii. Additionally, Allium thunbergii var. deltoides is unified into A. thunbergii var. thunbergii.

• International Journal of Industrial Entomology and Biomaterials
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• v.43 no.2
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• pp.67-77
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• 2021

Salurnis marginella Guérin-Méneville, 1829 (Hemiptera: Flatidae) is an invasive species first reported in 2003 in Iksan, which is located in the mid-western region of South Korea, and subsequently found in the nearby regions in 2005. However, molecular-perspective reports on their invasive characteristics are not yet available. In this study, population genetic characteristics of Korean S. marginella were evaluated using the mitochondrial COI region and sequencing 124 individual samples collected in 11 Korean localities. A total of 12 haplotypes were identified with a maximum sequence divergence of 1.368% (9 bp). Haplotype diversity was relatively higher than that of other insect species invaded into Korea, providing 2-6 haplotypes per populations, indicating that introduction to Korea may have happened rather extensively and consistently. Nucleotide diversity (π) was the highest in Iksan but owing to the limited sample size (three individuals) from this locality, additional studies are required for drawing conclusive inference regarding the place of entry to Korea. Ulsan, the easternmost population in the present study, revealed nearly the lowest diversity estimates, such as the lowest H and the second-lowest π; a unique haplogroup with a higher frequency; and an independent genetic cluster, suggesting that the introduction of S. marginella to Ulsan was an independent event. Further collection in Korea and neighboring countries, including the original distributional range is necessary to elucidate the invasive dynamics of S. marginella

• International Journal of Industrial Entomology and Biomaterials
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• v.47 no.2
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• pp.99-114
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• 2023

Patanga japonica Bolívar, 1898 (Orthoptera: Acrididae) is listed as a climate-sensitive indicator species in South Korea and is called southern group of insects in that the main distributional range is southern region of South Korea and Asian continent. In South Korea, thus, the species was distributed mainly in southern region of South Korea including southward a remote Jeju Island, but recently the species has often been detected in mid to northern region of South Korea, implying northward range expansion in response to climate change. Understanding the characteristics of the changes in genetic diversity during range expansion in response to climate change could be a foundation for the understanding of future biodiversity. Thus, in this study, we attempted to understand the changing pattern of the genetic diversity of the P. japonica in newly expanded regions. For the purpose of study, we collected 125 individuals from seven localities throughout South Korea including two newly distributed regions (Pyeongtaek and Yeongwol at ~37° N). These were sequenced for a segment of mitochondrial cytochrome oxidase subunit I (COI) and analyzed for genetic diversity, haplotype frequency, and population genetic structure among populations. Interestingly, northward range expansion accompanied only haplotypes, which are most abundant in the core populations, providing a significant reduction in haplotype diversity, compared to other populations. Moreover, genetic diversity was still lower in the expanded regions, but no genetic isolation was detected. These results suggest that further longer time would take to reach to the comparable genetic diversity of preexisting populations in the expanded regions. Probably, availability of qualified habitats at the newly expanded region could be pivotal for successful northward range expansion in response to climate change.

• KDI Journal of Economic Policy
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• v.34 no.1
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• pp.87-133
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• 2012

This paper consists of two parts. The first part introduces a simple endogenous growth model. It is based on Romer(1990), but extends the original model by incorporating individual workers skill heterogeneity. Based on the heterogeneity, the model has a labor allocation mechanism between skilled (research) and unskilled (production) sectors. Different from Romer(1990), the labor allocation is determined by both demand and supply conditions of the economy. The endogenous growth model presented in this paper shows how the shape of the distribution of human capital affects on the labor allocation, hence on the employment structure, wage profile and economic growth. The model can be extended to an open economy. With the heterogeneity, the extended model explains distributional effect as well as growth effect of the economic openness. The second part provides empirical evidence in support of the extension part of the model presented in the first part. Based on the endogenous growth framework as proposed by Romer(1990) and Rivera-Batiz and Romer(1991), the model explains how economic openness affects labor allocation between skilled and unskilled sectors. According to the model, economic openness can affect labor allocation through two channels; knowledge spillover and specialization. First, the openness promotes knowledge spillover and hence increases the productivity of workers in the skilled sectors. This makes the economy employs more workers in the skilled sector. On the other hand, the openness causes global specialization which leads more employment in the skilled sector for the developed countries but at the same time, leads less employment in the skilled sector for the developing countries since the developing countries have comparative advantages in the unskilled sector. The empirical results obtained using cross country panel data in this paper support these two effects of knowledge spillover and specialization.

• Korean Journal of Environment and Ecology
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• v.31 no.4
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• pp.365-380
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• 2017

Rapid changes in the flora of exotic species are ecological problems that cause the alteration of national and regional biota. The purpose of this study is to identify the reality of neophyte flora currently inhabiting in Korea. Having analyzed a total of 151 studies published up until 2016, we found the qualitative and quantitative gaps among the preceding studies due to the lack of rigorousness on the application of the spatial and temporal level of exotic species and academic terminology. In this study, the neophyte is defined as the flora introduced temporarily after the Enlightenment in Korea (late 19th century) and spatially in the Eastern Asiatic Province of the Takhtajan's floral region instead of a country boundary. A total of 326 taxa of 184 genera of 39 families were identified and analyzed for their distributional origin and habitat characteristics. Approximately 87% (285 taxa) was a component of the single-layered herb vegetation, and a total of 211 taxa originated from Europe and North America which are the same temperate biome as Korea. The wetland vegetation components were much fewer with 21 taxa, but they included a large number of invasive alien species that caused critical deterioration in the habitat structure and function of aquatic ecosystems. Ecological approaches to exotic species categories such as Ephemerophyten and Apophyten have emerged.

• Journal of Korea Water Resources Association
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• v.41 no.4
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• pp.379-394
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• 2008

Recently, extreme precipitation events beyond design capacity of hydraulic system have been occurred and this is the causes of failure of hydraulic structure for flood prevention and of severe flood damage. Therefore it is very important to understand temporal and spatial characteristics of extreme precipitation events as well as expected changes in extreme precipitation events and distributional characteristics during design period under future climate change. In this paper, climate change scenarios were used to assess the impacts of future climate change on extreme precipitation. Furthermore, analysis of future extreme precipitation characteristics and I-D-F analysis were carried out. This study used SRES B2 greenhouse gas scenario and YONU CGCM to simulate climatic conditions from 2031 to 2050 and statistical downscaling method was applied to establish weather data from each of observation sites operated by the Korean Meteorological Administration. Then quantile mapping of bias correction methods was carried out by comparing the simulated data with observations for bias correction. In addition Modified Bartlett Lewis Rectangular Pulse(MBLRP) model (Onof and Wheater, 1993; Onof 2000) and adjust method were applied to transform daily precipitation time series data into hourly time series data. Finally, rainfall intensity, duration, and frequency were calculated to draw I-D-F curve. Although there are 66 observation sites in Korea, we consider here the results from only Seoul, Daegu, Jeonju, and Gwangju sites in this paper. From the results we found that the rainfall intensity will be increased and the bigger intensity will be occurred for longer rainfall duration when we compare the climate conditions of 2030s with present conditions.

• Korean Journal of Construction Engineering and Management
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• v.13 no.2
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• pp.102-109
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• 2012

One of key success factors in PPI(Public Private Investment) is the structure of risk sharing between the public and the private, and the determination mechanism of fair return to private participants relative to the risk that private participants undertake. In Korea, two basic types of PPI exist. One is BTO and the other is BTL. In BTO, most risks are taken by the private whereas the opposite is the case in BTL. No intermediate form exists. As a result, BTO type projects had difficulty in attracting private participants because of the excessive risks. In this study, one intermediate form is studied where demand risk is shared between the public and the private. In the setting where the public authority takes all the project revenues and then pays ladder type payments to private participants depending upon the level of project revenues, appropriate level of fixed payments is endogenously derived using the real option pricing model. From the fixed payments, expected investment returns are calculated based upon a certain distributional assumption. The results of this study is expected to help introducing diverse forms of PPI in Korea.

• Korean Journal of Environment and Ecology
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• v.30 no.4
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• pp.658-675
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• 2016

The environmental characteristics of the habitats, the population structures, ecological niche, life traits and the population demography are used as an essential informations to the effective conservation plans about the target species. We first confirmed a total of 37 populations through 12 years of investigation on the extents, and investigated the environmental factors of habitats and the population structures of the 25 cohorts in 12 regions among them. And, we investigated the population dynamics targeting at 8 cohorts in the population of Daegwanryeong-myeon, Pyeongchang-gun, Gangwon-do. Along with this, we conducted 4 years of cultivation experiments and how pollinators affect the success of reproduction. The results shows that the Paeonia obovata Maxim. was found in a relatively wide range of habitats. For the population structures of the 25 cohorts, there were considerable differences among cohorts, including a case which showed relative stable structure and an extreme case in which only adults were found. The factor that affected the population dynamics during the investigation was thought as a forest gap created in the tree layer. In the cultivation experiment, seedlings grew well in a less soil organic matter. The seed setting rate and the number of seeds generated by visiting pollinators were higher trends. In conclusion, to understand the distribution of the Paeonia obovata Maxim., there needs to be investigated on the other factors that are involved in dispersal factors other than environmental factors, and thus we suggest the necessity of the research on the dispersal vectors. The current Paeonia obovata Maxim. population was thought as a process of expansion after the rapid reduction of the extents in the past. For the effective conservation of the Paeonia obovata Maxim., an endangered plant, we recommend to understand the species through the spatio-temporal expansion, and maintain the health of the ecosystem based on it.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.95-111
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• 2012

Relationship between plankton assemblage and environmental factors in a semi-closed Chunsu Bay was examined. Temporal changes in phytoplankton assemblage was rather drastic than those found in most Korean coastal area in the Yellow Sea primarily due to the seawater temperature (T) and nutrient input from the dikes nearby. Freshwater discharge seemed to cause winter time increase of Diatoms (February) and summer time increase of Dinoflagellates at surface (July to August). Structural change in cell size with time was also found in Diatom. Zooplankton community structure was also changed with season probably due to the food concentration, seawater temperature and salinity (S). From principal component analysis (PCA) of zooplankton distribution, it was postulated that seasonal environmental changes such as T and S could explain about 32% of variability in zooplankton distribution along with phytoplankton cell numbers, while freshwater discharge could explain about 17%. Comparing with past data of 1985-1986, 1991-1992, the distributional patterns and percent composition of major species, Acartia hongi, Paracalanus parvus sensu lato and Centropages abdominalis, were similar. However, the abundances have been increased more than three times. The composition of other taxa than copepods showed significant changes.