• 유통과학연구
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• 제17권3호
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• pp.69-83
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• 2019

Purpose - This paper investigates the long term impact of RFID investment on firm value in Korea. We wand to find out why the long term performance of some firm's RFID investment is better than others. To understand the dynamics of the long term returns from RFID investment announcements, we divide our events into groups for each of the independent firm characteristic variable such as investment time period, kind of markets, industries, solvency and growth potential. We composed portfolios based on the RFID investment announcement date for each group and evaluate the monthly abnormal excess returns. Research design, data, and methodology - Based on these calendar-time portfolios, we measure the long term returns from 86 RFID investment announcements of 46 firms from 2003 to 2017. We construct the calendar-time portfolio for 3, 6, 9, 12 months of holding periods. Using the weighted least squares method, we regress the raw monthly returns of the portfolios on the Fama-French model and Carhart(1997) model. As a result, we can get the estimated risk adjusted mean monthly abnormal excess return α_P for each of the calendar-time portfolio. Results - We found that early adopters, large firms, non-manufacturing firms have very significant excess returns. We also found modestly significant excess returns for financially stable firms and slow growing firms. Put together, top managers of the firms which plan to invest RFID should understand the strategic role of RFID adoption and the generalized business process of distribution information technology investment in Korea. Moreover, the findings of this paper provide useful trading strategies to the managers of large funds who are considering on investing in RFID adopting firms. Conclusions - Put together, the results of this paper give us a new insight into how the RFID and IT technology in general and other characteristic factors' interactions affect the long term performance of firms. Using the unbiased estimates of long term returns of the calendar-time portfolios, this paper extends the understandings on short term impact of RFID adoption of existing studies. This paper also extends the current understandings of firm characteristics that affect the long term performance of RFID adopting firms.

• The International Journal of Costume Culture
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• 제2권1호
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• pp.31-42
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• 1999

The category killer that has been rapidly growing mainly in advanced countries since early 1990's, is a mew distribution model which aims for obtaining market controlling power by surpassing competing businesses in a specific area of products. The domestic situation of category killers is very different from that of advanced ones abroad since it has just been introduced into the Korean market. At the moment, there are only 10 or so companies operating in the market : Geopyung's , Taeheng's , Midopa's , of Sinsegye Department store, adn of Yerim International. The purpose of this study is to examine problems of domestic companies in the present market by analysing the operation status of category killers in domestic markets as well as foreign ones, and to suggest a counter-strategy of category killers for the distribution environment of the 21st century to improve the competitiveness of Korean distribution industry. The competitiveness of category killers lies above all in products lines. Category killers are equipped with the greatest number of products lines among those of competing businesses due to maximized product selections in an limited range. Another source of competitiveness may be found in balanced strategy positioning. That is to say, category killers are in a position where they can adjust policies towards any of the three purposes while aiming at them altogether : prices of discount stores, products range of specialty stores, and customer service level of department stores. It is also necessary for efficient store operation to use information technology such as electronic data interchange (EDI), electronic pose system(EPOS) and electronic funds transfer (EFTPOS). As for the cost structure, category killers can gain an advantage over other business since operating cost of various sections can be saved. There are, however, certain risks that category killers with strong competitiveness may influence on other businesses a great deal and even facilitate their decline. Yet it seems that the growth of category killers will be more viciously restrained by continuous challenges from other businesses. The distribution industry is supposed to develop through such competition and restraint.

• 한국수산과학회지
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• 제27권5호
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• pp.659-672
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• 1994

진해만의 저서동물 군집에 대해 Sanders(1968)의 희박법(Rarefaction method), Warwick(1986)의 개체수-생물량 비교법(Abundance-Biomass Comparison method), Gray(1979)의 대수-정규분포 응용법 (Log-Normal Distribution method) 및 Frontier(1985)의 순위-빈도 곡선법 (Rank-Frequency Diagram method) 등의 환경 평가 기법을 이용하여 진해만의 오염정도를 평가하였다. 이 방법들 가운데 개체수-생물량 비교법은 오염해역에 개체당 생물량이 큰 이매패류인 Periglypta cf. puerpera와 Macoma tokyoensis와 다모류인 Nectoneanthes multignatha가 출현함으로서 이 방법의 원리에서 요구하는 전제 조건을 잘 반영하지 못하였다. 그러나 나머지 3가지 방법은 진해만의 환경을 잘 반영하고 있었으며, 가장 내만에 위치한 Group-I이 가장 오염된 해역으로 나타났으며 진해만 중앙부 해역인 Group-II도 상당히 오염이 진행된 것으로 나타났다. 그러나 진해만 입구인 Group-III과 VI는 내만 해역에 비해 상대적으로 오염의 영향이 적은 것으로 나타났다. 이러한 방법들 가운데 종별 개체수 자료만을 필요로 하는 대수-정규 분포 응용법이 오염을 평가하는데 가장 편리하고 적합한 것으로 판단되며, 그 밖의 희박법 및 순위-빈도 곡선도 상대적 평가 방법으로는 유익한 수단이 된다. 우리나라의 다른 해역에서의 오염평가도 저서동물의 분포특성을 이용한 이러한 다양한 환경평가 기법을 시도해 보는 것이 바람직할 것으로 생각된다.

• 한국환경생태학회지
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• 제21권1호
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• pp.74-81
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• 2007

본 연구는 한국 갯기름나물의 지형적 분포와 해식애 군집구조의 기초자료로 제공하기 위하여 해안과 지형별 종조성 및 생육양상을 조사한 바 이의 결과를 요약하면 다음과 같다. 갯기름나물과 동반 출현하는 식물은 57과 130속에 속한 170 분류군이었으며, 과별로는 국화과가 30 분류군으로 가장 많았다. 출현빈도가 가장 높은 식물은 해국(54.1%)이었고, 해안별로는 동해안과 서해안에서 해국, 남해안에서 억새의 출현빈도가 가장 높았다. 해안별 공통종은 서해안과 남해안간이 35.6%(47 분류군)로서 가장 높았고 다음으로 동해안과 서해안(30.4%), 동해안과 남해안(26.4%)순이었다. 갯기름나물이 출현하는 해안지형은 경사도 $17.4^{\circ}$의 해식애 암석해안, 평탄면, 암괴원, 수평절리, 수직절리, 요철지형이었고 지형 별 분포지역은 암석해안이 61 지역으로 가장 많았다. 군도에 따른 갯기름나물의 생육양상은 군도계급 3이 83지역(54.6%)으로서 가장 많았다.

• 한국수자원학회논문집
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• 제43권4호
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• pp.337-351
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• 2010

극치사상을 예측하기 위한 기존의 빈도분석 결과의 이용에 대한 많은 문제점들이 부각되고 있다. 특히, 통계적 모형을 이용하기 위해서 흔히 사용되는 점근적 모형 (asymptotic model)의 합리적인 검토 없는 외삽 (extrapolation)은 산정된 확률 값을 과대 또는 과소평가하는 문제를 일으켜, 예측결과에 대한 불확실성을 과다하게 산정함으로써 불확실성에 대한 신뢰도를 감소시키는 문제가 있다. 그러므로 본 연구에서는 국내에서 극치강우사상을 포함한 강우자료의 빈도분석에 대한 연구사례를 제공하고 점근적 모형을 사용하는 경우 발생되는 불확실성을 감소시키기 위한 방법론을 제시하였다. 이를 위하여 본 연구에서는 극치강우사상의 빈도분석을 수행하는 데 있어서 최근 들어 여러 분야에서 다양하게 적용되고 있는 Bayesian MCMC (Markov Chain Monte Carlo) 방법을 사용하였으며, 그 결과를 최우추정방법 (Maximum likelihood estimation method)과 비교하였다. 특히 강우사상의 점 빈도분석에 흔히 이용되는 확률밀도함수로 GEV (Generalized Extreme Value) 분포와 Gumbel 분포를 모두 고려하여 두 분포의 결과를 비교하였으며, 이 과정에서 각각의 산정결과 및 불확실성은 근사식을 이용한 최우추정방법과 Bayesian 방법을 이용하여 각각 비교 및 분석되었다.

• 한국환경복원기술학회지
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• 제17권1호
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• pp.111-122
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• 2014

The provided habitat of many services from natural capital is important. But because most ecosystem services tools qualitatively evaluated biodiversity or habitat quality, this study quantitatively analyzed those aspects using the species distribution model (MaxEnt). This study used location point data of the goat(Naemorhedus caudatus), marten(Martes flavigula), leopard cat(Prionailurus bengalensis), flying squirrel(Pteromys volans aluco) and otter(Lutra lutra) from the 3rd National Ecosystem Survey. Input data utilized DEM, landcover classification maps, Forest-types map and digital topographic maps. This study generated the MaxEnt model, randomly setting 70% of the presences as training data, with the remaining 30% used as test data, and ran five cross-validated replicates for each model. The threshold indicating maximum training sensitivity plus specificity was considered as a more robust approach, so this study used it to conduct the distribution into presence(1)-absence(0) predictions and totalled up a value of 5 times for uncertainty reduction. The test data's ROC curve of endangered mammals was as follows: growing down goat(0.896), otter(0.857), flying squirrel(0.738), marten(0.725), and leopard cat(0.629). This study was divided into two groups based on habitat: the first group consisted of the goat, marten, leopard cat and flying squirrel in the forest; and the second group consisted of the otter in the river. More than 60 percent of endangered mammals' distribution probability were 56.9% in the forest and 12.7% in the river. A future study is needed to conduct other species' distribution modeling exclusive of mammals and to develop a collection method of field survey data.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2019년도 학술발표회
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• pp.160-160
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• 2019

Water is a limited source that needs to be properly managed and distributed to the ever-growing population of the world. Rapid urbanization and development have increased the overall water demand of the world drastically. However, there is loss of billions of liters of water every year due to leakages in water distribution systems. Such water loss means significant financial loss for the utilities as well. World bank estimates a loss of $14 billion annually from wasted water. To address these issues and for the development of efficient and reliable leakage management techniques, high efforts have been made by the researchers and engineers. Over the past decade, various techniques and technologies have been developed for leakage management and leak detection. These include ideas such as pressure management in water distribution networks, use of Advanced Metering Infrastructure, use of machine learning algorithms, etc. For leakage detection, techniques such as acoustic technique, and in recent yeats transient test-based techniques have become popular. Smart Water Grid uses two-way real time network monitoring by utilizing sensors and devices in the water distribution system. Hence, valuable real time data of the water distribution network can be collected. Best results and outcomes may be produced by proper utilization of the collected data in unison with advanced detection and management techniques. Long term reduction in Non Revenue Water can be achieved by detecting, localizing and repairing leakages as quickly and as efficiently as possible. However, there are still numerous challenges to be met and future research works to be conducted in this field.

• 농업생명과학연구
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• 제53권2호
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• pp.65-75
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• 2019

Stem and root of elm trees have used as traditional medical materials, but there is little information on the distribution and resources of habitats. Korean native growing Ulmus spp. (U. davidiana var. Japonica, U. parvifolia, U. davidiana, and U. macrocarpa) genetic resources studied through The National Forest Inventory of Korea data and field survey. The distributions of U. davidiana var. japonica according to elevation distributed evenly. Both U. parvifolia and U. davidiana were inhabited mostly at less than 200 m of altitude. Each Ulmaceae species widely were distributed nationwide, but a dominant species was different depending on locals. It observed that Ulmaceae inhabits mainly in steep slopes of 31-45 degrees. Most of the habitats regenerated by natural seeding and the most abundant species were a codominant tree. Distribution of trees in U davidiana var. japonica was 7 m-13 m, and in young U. parvifolia and U. macrocarpa, more than 25% of young trees less than 7 m observed. The distribution of the diameter of breast height of the U. davidiana var. japonica was 46.4% for 11-20 cm, 52.6% for 11-20 cm in U. parvifolia. The average T/R ratio was 0.83, and the mean weight ratio of root bark was 62%. As the results of this study, the domestic Ulmaceae biomassare very small. It is difficult to harvest in that the habitat on the slope. Thus, it is too hard to develop functional materials using biomass at present. Therefore, it is necessary to develop technology for the selection and propagation of elite trees of Ulmaceae.

• 한국전기전자재료학회논문지
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• 제35권5호
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• pp.504-508
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• 2022

Single crystal gallium oxide (Ga₂O₃) has been an emerging material for power semiconductor applications. However, the defect distribution of Ga₂O₃ substrates needs to be carefully characterized to improve crystal quality during crystal growth. We analyzed the type and the distribution of defects on commercial (-201) Ga₂O₃ substrates to get a basic standard prior to growing Ga₂O₃ crystals. Etch pit technique was employed to expose the type of defects on the Ga₂O₃ substrates. Synchrotron white beam X-ray topography was also utilized to observe the defect distribution by a nondestructive manner. We expect that the observation of defect distribution with three-dimensional geometry will also be useful for other crystal planes of Ga₂O₃ single crystals.

• 한국농림기상학회지
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• 제12권4호
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• pp.225-231
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• 2010

강원도 주요 복숭아 재배지의 2010년 1월 7일의 일 최저기온 분포는 $-18{\sim}-29^{\circ}C$로서, 평년보다 $10^{\circ}C$ 이상 낮았으며 복숭아의 동해온도로 설정된 $-18^{\circ}C$보다 낮았다. 이로 인한 저온 피해 면적은 원주 144ha, 춘천 89ha, 영월 33ha, 횡성 22ha, 양구 17ha, 홍천 16ha 등이었다. 금후 강원 지역의 복숭아 동해에 대한 대책을 수립하는 데 기초 자료를 제공하고자 실제 동해 면적율과 휴면심도를 바탕으로 한 동해위험지수를 비교하였다. 자동기상측정장치가 설치된 지역의 일 최고기온과 일 최저기온, 기준온도를 바탕으로 계산한 장호원황도의 휴면심도는 -62 ~ -90였다. 휴면심도와 일 최저기온으로부터 계산된 동해위험지수는 51% 이상이었고, 이 동해위험지수는 실제 피해 면적 비율과 통계적으로 유의한 선형 관계를 나타내었다. 장호원황도의 휴면심도를 바탕으로 한 동해위험지수로 정확한 저온 피해 예측에는 어느 정도 한계가 있으나, 과수농가에서 복숭아의 동해를 대비하는 데 유용하게 활용할 수 있을 것으로 판단된다.