• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.4
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• pp.348-357
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• 2015

The main purpose of this study is to understand the potential geographic distribution of P. koraiensis, which is known to be one of major economic tree species, based on the RCP (Representative Concentration Pathway) 8.5 scenarios and current geographic distribution from National Forest Inventory(NFI) data using ecological niche modeling. P. koraiensis abundance data extracted from NFI were utilized to estimate current geographic distribution. Also, GARP (Genetic Algorithm for Rule-set Production) model, one of the ecological niche models, was applied to estimate potential geographic distribution and to project future changes. Environmental explanatory variables showing Area Under Curve (AUC) value bigger than 0.6 were selected and constructed into the final model by running the model for each of the 27 variables. The results of the model validation which was performed based on confusion matrix statistics, showed quite high suitability. Currently P. koraiensis is distributed widely from 300m to 1,200m in altitude and from south to north as a result of national greening project in 1970s although major populations are found in elevated and northern area. The results of this study were successful in showing the current distribution of P. koraiensis and projecting their future changes. Future model for P. koraiensis suggest large areas predicted under current climate conditions may be contracted by 2090s showing dramatic habitat loss. Considering the increasing status of atmospheric $CO_2$ and air temperature in Korea, P. koraiensis seems to experience the significant decrease of potential distribution range in the future. The final model in this study may be used to identify climate change impacts on distribution of P. koraiensis in Korea, and a deeper understanding of its correlation may be helpful when planning afforestation strategies.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.781-795
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• 2008

This paper focuses on effects that IPTV will have on domestic broadcasting market in the point of view of customers. The purpose of the paper is to present the future landscape of competitive media market when IPTV is launched, and to research how IPTV will have impact on terrestrial broadcasting, cable TV and satellite broadcasting industry. The paper integrates two known theories, such as the niche-gratification model and the value-expectancy model, to analyze competitive media market. The value expected model makes it possible to overcome the weakness of the niche-gratification model and to forecast competitiveness more accurately. According to this research, competitive power will be in the order of Cable TV, IPTV, and satellite broadcasting. Terrestrial broadcasting does not show strong competitive relationships with others statistically. As a result, Cable TV will be the most competitive medium in the future. IPTV will be stuck in the middle and can rapidly substitute for existing broadcasting services. While IPTV will severely threaten the satellite broadcasting company which has a relatively small number of subscribers, cable TV will be in a superior position to IPTV.

• 한국해양학회지
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• v.30 no.5
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• pp.442-457
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• 1995

The relationships of environmental factors to the distribution patterns of the three species of ophiuroids, Ophiura kinbergi, O. sarsi and ). sarsi vadicola from Yellow Sea southeast seas and East Sea of Korea were studied to characterize their habitual niches. These three species chosen for study illustrated distinct niche and patterns according to their various preferences mainly for bottom water temperature, bottom water salinity and depth from seven environmental variables which were depth, bottom water temperature and salinity, density, bottom water oxygen content, grain size of the surface sediment, and sediment sorting coefficient. The results of habitat niche study mainly dealing with O. sarsi vadicola suggested that the optimum habitat rages were approximately 6$^{\circ}C$∼10$^{\circ}C$ in bottom temperature and 31%∼33.5% in bottom water salinity which also corresponded with the characteristic ranges of Yellow Sea Bottom Cold Water and higher probabilities of occurrence (more than 70%) were found in depth ranging from 100 to 200 m. In addition, the habitats of O. kinbergi and O. sarsi were compared with that of O. sarsi vadicola. Their ranges of habitat niches were found to have different niches in physical space of bottom water temperature, bottom water salinity and depth. Based on the distribution pattern of O. sarsi vadicola in the Yellow Sea, the ecological barrier which confined the distribution of benthic macro-invertebrates in southern Yellow Sea was determined to be the Yellow Sea Warm Current (approximately 34% < and 18$^{\circ}C$ in December) which occurs between 33$^{\circ}$ and 34$^{\circ}$N of southern Yellow Sea in winter time.

• Journal of Korean Society of Forest Science
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• v.82 no.2
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• pp.176-187
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• 1993

Based on the analysis of ecomorphological characters for 84 tree and shrub species, climax indices were estimated so as to interpret the position of the successional sere for the species in the natural deciduous forest. Nineteen ecomorphological characters, considered to be associated with successional gradient in the forest, were selected for the study. One of 2 to 4 steps per character for each species was given on a standardized scale of increasing climaxness, and the index was computed by percent of the sum of the scoring values for total score. Calculated mean value of 54.2 for all indices. Carpinus laxiflora had the highest index value of 83.3, and Populus davidiana recorded the lowest of 18.8. The most climax group, greater than 70 of the index, contained only 9 species, intermediate group, between 40 to 70 of the index, had 58 species, and the most pioneer group, less than 40 of the index comprised 17 species. The result has noticed that the large number of species would take advantage of most diverse resource and niche in the intermediate stage of the sere in the forest. The three components, i.e., light absorption, reproduction, and wood quality were used as axes for a 3-dimensional projection of the relative position for 44 species by principal component analysis. Along the similar ecomorphological characters, four recognized species group were classified by cluster analysis. The distribution pattern of plant families on the index gradient showed that the Betulaceae and Aceraceae had the widest seral amplitude, and the Salicaceae was a family typified as pioneer. There were no families specializing entirely with climax niche.

• Journal of Science Education
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• v.41 no.2
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• pp.195-212
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• 2017

Small group learning is an educational approach to allow students to solve the problems and to achieve a common goal. Especially, small group learning in science education is one of the most important educational approaches and effective to ensure understanding of a topic. Small group learning consisting of three students in science education maximize student understanding and learning efficiency. However, It is reported that the effects of small group learning on achievement show different results, corresponding to different grouping methods(homogeneous/heterogeneous). This study investigated the effects of grouping method on difference of ecological niche of photosynthesis concepts. To achieve this, 1107 7th students were composed of homogeneous and heterogeneous groups classified into top, middle, and bottom levels. The photosynthesis units were divided into four categories: the photosynthesizing place, the substances of photosynthesis, required materials for the photosynthesizing, and environmental factors affecting photosynthesis. A questionnaire was composed by selecting concepts having a frequency of 4% or more based on prior studies on the change of the ecological status of photosynthesis. The questionnaire was scored in terms of relativity and understanding on each of the proposed concepts in the four categories. The result of this study is as set forth below. 1) There was an enhancement of learning the concept of science in small group classes consisting of 3 students. 2) To enhance the average upon composing of a group, it is proposed that the group should be formed homogeneously, and to reduce the deviation between the members, it is proposed that the group should be formed heterogeneously. Through this study, it is expected that specific studies verifying the difference or effect on the duplicity of results are conducted based on the composition of groups.

• Journal of Wetlands Research
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• v.13 no.2
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• pp.355-362
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• 2011

Bog bean (Menyanthes trifoliata L.) is an endangered species in Korea and a perennial macrophyte with long rhizome, inhabiting in oligotrophic fen or edges of montane lakes. To decide appropriate substrate type for restoration of this plant, we investigated the effect of substrates (e.g. water, Sphagnum mat, paddy soil) on growth of bog bean. There were two water conditions on paddy soils: saturated and flooded. We planted 10cm rhizome in mesocosms and measured coverage, leaf area, leaf number and rhizome biomass. Bog bean growed until August in water and Sphagnum mat and until October in paddy soil. Rhizome biomass at the end of November were 49, 77, 239, and 312g in water, Sphagnum mat, paddy soil with water saturated, and paddy soil with water flooded conditions, respectively. The results indicate that bog bean can grow better in paddy soil which have higher nutrient than water or Sphagnum mat which represents natural habitat condition of bog bean. This reveals that actual ecological niche of bog bean is different from fundamental ecological niche in substrate. For successful restoration of bog bean in nutrient rich area, it is necessary to know the competitiveness of bog bean in various substrate conditions.

• Korean Journal of Ecology and Environment
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• v.54 no.4
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• pp.363-373
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• 2021

An ecological niche is defined as the specific role of a species influenced by time, space, and other resources. By investigating overlaps between ecological niches of different species, we could estimate the degrees of interspecific competition. Such studies often use geographic information systems (GIS) to discover niche overlaps between species. In this study, we used GIS to estimate the spatial niches of two Korean frog species(Pelophylax nigromaculatus and P. chosenicus). This enabled us to predict their geographic distributions in order to identify their coexistence regions and distribution patterns. The results confirmed that altitude was an important variable for predicting their distribution, with a correlation with their climatic range. Spatial distributions of the two frog species were highly overlapped, as the distribution range for P. nigromaculatus included most of the range of P. chosenicus, showing a sympatric distribution pattern. Within the coexisting regions, however, the presence sites for the two species did not overlap, implying weak competition. To confirm the principal factors influencing their competitive relationship and reasons for their sympatric distribution pattern, we need more detailed in-depth studies on the diverse environmental variables within the regions where the two species coexist. By doing so, we would be able to identify various mechanisms for avoiding competition in sympatric frog species.

• Journal of Internet Computing and Services
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• v.22 no.2
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• pp.89-107
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• 2021

This paper explores the empirically analyzes the competitive nature of the five social media by analyzing the proper SNS service such as Facebook, Instagram, YouTube, Pinterest, and Twitter. In this study, we surveyed the use and satisfaction of social media for SNS users by using the proper theory. A total of 224 users were selected for analysis. Based on the results of the questionnaire, factor analysis was carried out to extract common factors such as relationship, sociality, convenience, daily life, and entertainment. As a result of the research using proper analysis, Facebook showed the widest narrowness in sociality (.627) and convenience (.636) in the first place, and YouTube showed the lowest in daily life (.670) and entertainment (.615) In the relationship (.520), the Instagram was the widest. In terms of five factors, Facebook and YouTube have the greatest overlap in relationship (1.826) and sociality (2.696), while Pinterest and Twitter are the most common in daily life (1.937) and entertainment (2.263) There is redundancy, and for convenience (2.583), YouTube and Twitter have the most redundancy. Facebook, Instagram, and YouTube have a competitive advantage over Pinterest in terms of relationships, sociality, convenience, routine, and entertainment, and are competitive across all factors except Facebook, Instagram, and YouTube Twitter It is possible to confirm that it is superior.

• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.360-367
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• 2022

Research on food sources through DNA metabarcoding is being used for various organisms based on high resolution and reproducibility. In the study, we investigated the difference in food sources between pre and post-starving in the three bivalve species (Anemina acaeformis, Anodonta woodiana, and Unio douglasiae) through DNA metabarcoding using 18S rRNA V9 primer. The food source of pre-starving appeared in 87 genera, 71 families, 51 orders, 35 classes, and 22 phyla. The primary food sources were the zoo and phytoplankton, including Chlamydomonadales, Euglenales, Ploima, Sphaeropleales, and Stephanodiscales. However, all zoo and phytoplankton were not observed after starving except Schizopyrenida and Rotifera. In Levin's niche breadth analysis, the Bi index of A. woodiana is 0.3, which was higher than A. acaeformis(0.14) and U. douglasiae (0.21), indicating that they feed on various food sources. The niche overlap of A. acaeformis was measured as 0.78 in A. woodiana, 0.7 in U. douglasiae showing a relative high value compared to other bivalves. The trophic level of A. acaeformis, A. woodiana, and U. douglasiae based on the food source information were investigated as 2.0, 2.0, and 2.5, respectively. The results of the previous study on the trophic level using stable isotopes showed 1.8 to 2.4 values were similar to the results of this study. These results suggest that DNA metabarcoding can be an effective analyzing tool for the gut content in the bivalves.

• Journal of Wetlands Research
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• v.25 no.2
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• pp.159-165
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• 2023

This study measured the ecological niche overlap between two deciduous oak species(Quercus acutissmia and Q. dentata) according to the change in growth responses after treating with the moisture and nutrient contents of the soil at four gradients, and interpreted the degree of competition between the two oak species by ordination method. In the moisture environment gradient, the ecological niche overlap of the two species was high in the photosynthesis-related leaf organs and low in plant architecture such as shoot length. In addition, in case of competition between two oaks, Q. dentata was remarkably dominant in soil moisture gradient, but Q. acutissimia slightly was slightly advantageous over Q. dentata in the soil nutrient gradient. These results show that even in a similar taxonomical group growing in a similar habitat, the response to the organ system of the plant varies depending on the type of environment factor, resulting in different competitive differences among plants.