• 한국음향학회지
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• 제38권3호
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• pp.344-351
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• 2019

본 연구에서는 수축 및 팽창 소음 발생 메커니즘을 분석하고, 냉장고 운전 중에 소음발생 빈도를 줄이기 위한 효과적인 방법을 제안하였다. 냉장고의 수축팽창음 발생 시에 제품의 품질비용 상승에 영향을 주기 때문에 저감이 필요하다. 먼저, 무향실에서 측정된 음압 신호를 이용하여 주파수 스펙트럼 분석을 수행하여 소음의 특성과 발생 빈도를 분석하였다. 둘째, 열변형 해석을 수행하여 소음원의 위치를 예측했다. 분석결과에서 가장 큰 열변형은 냉동실의 왼쪽 내부 케이스의 중간에서 발생하였다. 또한 음원 위치의 가속도 레벨을 평가한 결과, 소음을 발생시키는 내부 부품이 냉동실의 세 번째 선반임을 알 수 있었다. 냉장고의 중앙 ABS(Acrylonitrile Butadiene Styrene) 두께 증가에 의한 열변형 저감을 통하여 수축팽창음을 저감할 수 있는 방법을 제안하였다.

• 한국응용곤충학회지
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• 제55권4호
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• pp.431-437
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• 2016

시설딸기에 발생하는 해충 종류와 피해를 구명하기 위하여 2013년부터 2016년까지 제주지역의 농가포장에서 조사한 결과 8목 31종이 발생되고 있었다. 그중에서 발생과 피해가 큰 해충은 점박이응애(Tetranychus urticae), 꽃노랑총채벌레(Frankliniella occidentalis), 목화진딧물(Aphis gossypii) 3종이었다. 그 외에 딸기가루이와 괴테애매미충은 일부 조사포장에서 피해가 나타났으나 발생과 피해가 점차 증가하고 있었다. 나방류 중에서는 담배거세미나방(Spodoptera litura)의 발생빈도와 피해가 가장 컸으며, 왕담배나방(Helicoverpa armigera)은 조사기간 중 발생빈도는 적었으나 피해는 심했다. 조사 해충 중 황색끈끈이트랩으로 발생밀도를 예찰할 수 있는 꽃노랑총채벌레와 목화진딧물 유시충, 딸기가루이, 괴테애매미충에 대한 시기별 발생특성에 대하여 고찰하였다.

• 융합경영연구
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• 제11권5호
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• pp.45-55
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• 2023

Purpose: As one of the continuous studies on the offline distribution industry, the purpose of this study is to find ways for offline stores to respond to the growth of online shopping by identifying research trends on department stores. Research design, data and methodology: To this end, this study conducted word frequency analysis, word co-occurrence frequency analysis, BERTopic, LDA, and dynamic topic modeling using Python 3.7 on a total of 551 English abstracts searched with the keyword 'department store' in scienceON as of October 10, 2022. Results: The results of word frequency analysis and co-occurrence frequency analysis revealed that research related to department stores frequently focuses on factors such as customers, consumers, products, satisfaction, services, and quality. BERTopic and LDA analyses identified five topics, including 'store image,' with 'shopping information' showing relatively high interest, while 'sales systems' were observed to have relatively lower interest. Conclusions: Based on the results of this study, it was concluded that research related to department stores has so far been conducted in a limited scope, and it is insufficient to provide clues for department stores to secure competitiveness against online platforms. Therefore, it is suggested that additional research be conducted on topics such as the true role of department stores in the retail industry, consumer reinterpretation, customer value and lifetime value, department stores as future retail spaces, ethical management, and transparent ESG management.

• 융합경영연구
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• 제11권4호
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• pp.53-63
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• 2023

Purpose: The purpose of this study is to examine the research trends in the papers published by Korean researchers related to traditional markets, to check what topics have been studied, and to make various suggestions for research directions and effective ways to revitalize traditional markets. Research design, data and methodology: To this end, this study conducted word frequency analysis, co-occurrence frequency analysis, BERTopic, LDA, dynamic topic modeling and OLS regression analysis using Python 3.7 on the English abstracts of a total of 502 papers extracted through ScienceON. Results: As a result of word frequency analysis and co-occurrence frequency analysis, it was found that studies related to traditional markets have been conducted not only on factors related to customers, but also on traditional market merchants and government policies, and the degree of service, quality, and satisfaction perceived by customers using traditional markets. Through BERTopic and LDA, three topics such as 'Traditional market safety management' were identified, and among them, it was found that 'Traditional market safety management' is relatively less attention by researchers. Conclusions: The results of this study suggest that future research on the revitalization of traditional markets should be conducted from a specific consulting perspective along with the establishment of various data, a causal model study from various perspectives such as the characteristics of merchants as well as consumers, and an integrated and convergent approach to policy formulation by the government and local governments.

• 치위생과학회지
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• 제23권4호
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• pp.255-263
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• 2023

Background: This study used text mining techniques to determine public perceptions of dental fear, extracted keywords related to dental fear, identified the connection between the keywords, and categorized and visualized perceptions related to dental fear. Methods: Keywords in texts posted on Internet portal sites (NAVER and Google) between 1 January, 2000, and 31 December, 2022, were collected. The four stages of analysis were used to explore the keywords: frequency analysis, term frequency-inverse document frequency (TF-IDF), centrality analysis and co-occurrence analysis, and convergent correlations. Results: In the top ten keywords based on frequency analysis, the most frequently used keyword was 'treatment,' followed by 'fear,' 'dental implant,' 'conscious sedation,' 'pain,' 'dental fear,' 'comfort,' 'taking medication,' 'experience,' and 'tooth.' In the TF-IDF analysis, the top three keywords were dental implant, conscious sedation, and dental fear. The co-occurrence analysis was used to explore keywords that appear together and showed that 'fear and treatment' and 'treatment and pain' appeared the most frequently. Conclusion: Texts collected via unstructured big data were analyzed to identify general perceptions related to dental fear, and this study is valuable as a source data for understanding public perceptions of dental fear by grouping associated keywords. The results of this study will be helpful to understand dental fear and used as factors affecting oral health in the future.

• 아시안잔디학회지
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• 제13권2호
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• pp.79-90
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• 1999

This study was conducted to provide basic understandings for proper management of zoysiagrass fairways. Mowing intervals of 2, 4 and 6-days, with and without aeration were compared at two fertility levels. Turfgrass quality, growth and pest infestation were evaluated. Turf density, number of tillers, leaf width and resiliency were significantly affected by mowing frequency. Turfgrass plots mowed every 2-day had greater density, tillering, and resiliency but had narrower leaf width compared to other mowing treatments. Clipping dry weight with every 2-day mowing increased in the early stage of mowing treatment regardless of fertilizer application rates but gradually decreased in the later stage of mowing treatment compared to every 4 or 6-day mowings. The dry weight of above-ground part was not affected by mowing frequency, but that of underground part was significantly higher for every 6-day mowing frequency(3.3kg/day/m2) compared to every 2 or 4-day mowings. The organic mater content in soil was not different among mowing treatments but it was significantly reduced by the core aerification treatment, indicating significant effect of core aerification on thatch decomposition. Occurrences of weeds such as annual bluegrass and crabgrass according to mowing frequency were greater in every 2-day mowing treatment, while plots mowed every 6 days had less weed occurrence. Occurrence of rusts significantly increased in high fertility plots and frequently mowed turfgrasses.

• Earthquakes and Structures
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• 제4권5호
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• pp.557-585
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• 2013

The recent huge earthquake ground motion records in Japan result in the reconsideration of seismic design forces for nuclear power stations from the view point of seismological research. In addition, the seismic design force should be defined also from the view point of structural engineering. In this paper it is shown that one of the occurrence mechanisms of such large acceleration in recent seismic records (recorded in or near massive structures and not free-field ground motions) is due to the interaction between a massive building and its surrounding soil which induces amplification of local mode in the surface soil. Furthermore on-site investigation after earthquakes in the nuclear power stations reveals some damages of soil around the building (cracks, settlement and sand boiling). The influence of plastic behavior of soil is investigated in the context of interaction between the structure and the surrounding soil. Moreover the amplification property of the surface soil is investigated from the seismic records of the Suruga-gulf earthquake in 2009 and the 2011 off the Pacific coast of Tohoku earthquake in 2011. Two methods are introduced for the analysis of the non-stationary process of ground motions. It is shown that the non-stationary Fourier spectra can detect the temporal change of frequency contents of ground motions and the displacement profile integrated from its acceleration profile is useful to evaluate the seismic behavior of the building and the surrounding soil.

• 한국농공학회지
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• 제38권5호
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• pp.64-73
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• 1996

When typhoon occurs, the meteorological conditions get worse and can cause a large damage from storm and flood . This damage, however, can be minimized if a precise analysis of the runoff characteristics by typhoon tracks is used in the flood contorl This paper aims at the analysis of storm occurrence and runoff characteristics by typhoon tracks in Nakdong river basin. Therefore, the data of 14 typhoons which invaded Nakdong river basin during the period from 1975 to 1991 were collected, analyzed, and studied. The major results of this study are as followings; 1) The frequency of the typhoon occurrence here in Korea was affected by the storms three times a year on the average. The highest-recorded frequency was during the months of July to September. 2) The survey of the track characteristics depending on the forms of the storm in the Nakdong river basin showed that typhoon storm advanced from the south of the basin to the north, while the frontal type storm was most likely to advanced from the west to the north. 3) Typhoon tracks are classified into three categories, 6 predictors with high correlation coefficient are finally selected, and stepwise multiple regression method are used to establish typhoon strom forecasting models. 4) The riview on the directions of progress of the storm made it clear that the storm moving downstream from upstream of the basin could develop into peak discharge for ca short time and lead to more flood damage than in any other direction.

• 한국환경과학회지
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• 제12권4호
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• pp.419-426
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• 2003

This study was performed to research ozone concentration related to airmass thunderstorm using 12 years meteorological data(1990~2001) at Busan. The occurrence frequency of thunderstorm during 12 years was 156 days(annual mean 13days). The airmass thunderstorm frequency was 14 days, most of those occurrence at summertime(59%). In case August 4, 1996, increase of ozone concentration was simultaneous with the decrease of temperature and increase of relative humidity, In case July 23, 1997, ozone concentration of western site at Busan increased, while its of eastern site decreased as airmass thunderstorm occurred(about 1500LST). It is supposed that these ozone increases are the effect of ozone rich air that is brought down by cumulus downdrafts from height levels where the ozone mixing ratio is larger. Thunderstorms can cause downward transport of ozone from the reservoir layer in the upper troposphere into planeta교 boundary layer(PBL). This complex interaction of source and sink processes can result in large variability fer vertical and horizontal ozone distributions. Thus a variety of meteorological precesses can act to enhance vertical mixing between the earth's surface and the atmospheric in the manner described fer thunderstorm.

• 생태와환경
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• 제56권2호
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• pp.172-186
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• 2023

불안정한 천이양상을 보이는 소형 호소는 대형 호소에 비해 동물플랑크톤 군집 동태 연구가 미진한 상황이다. 최근 지역 생물다양성 보전의 측면에서 소형 호소의 존재 가치가 부각되면서 생물 군집 동태 대한 이해의 필요성이 강조되고 있다. 본 연구는 세 소형 호소의 출현 동물플랑크톤을 월별로 채집하여 계절별 군집 동태를 분석하였다. 소형 호소의 복잡한 동물플랑크톤 군집 동태를 파악하기 위해 종 출현 패턴을 기반, 4개의 그룹(LALF Group, Low Abundance Low Frequency; LAHF Group, Low Abundance High Frequency; HALF Group, High Abundance Low Frequency; HAHF Group, High Abundance High Frequency)으로 그룹화하였다. 그룹 간 계절적 패턴을 비교하였으며, 각 그룹의 시간적 베타 다양성 기여도를 기반으로 한 다양성을 산출했다. 분석 결과 같은 출현량 경향을 보이지만 상반된 출현 빈도를 보이는 그룹 간의 관계가 있는 것으로 나타났으며, Nauplius가 세 호소공통으로 높은 출현량과 빈도를 보이는 종으로 나타났다. 적은 개체수를 보이면서 출현 빈도 역시 드물게 나오는 종들이 포함된 그룹인 LALF 그룹에 속한 종이 월별 천이와 다양도에 핵심인 것으로 분석되었으며 해당 그룹에는 Anuraeopsis fissa, Hexarthra mira 및 Lecane luna가 포함되었다. 한편 연중 특정 시기에만 출현하여 수체를 우점하는 종들이 포함된 그룹인 HALF 그룹이 호소 공통적으로 시간적 다양성을 저해하는 것으로 분석되었다. 본 연구의 결과를 통해 종 특이적인 출현 패턴이 연내 군집의 생물다양성에 기여하는 종을 분석하는 데 있어서 핵심적으로 작용할 수 있음을 제안한다.