난류 모델별 수치해석을 이용한 업윈드형 소형 풍력터빈의 성능 연구

유창환 ( Chang-hwan Yu ),김성환 ( Seong-hwan Kim ) 조선대학교 공학기술연구원 2020 공학기술논문지 Vol.13 No.4

In the field of renewable energy, there is growing interest in wind energy to cope with climate change. Research is needed on small residential facilities or stand-alone small wind turbines for microgrid power generation. This study is for commercialization of a small horizontal wind turbine of a 2,600 mm diameter upwind type and is a thesis for a design and performance check on performance. A blade was designed and flow analysis was performed with ANSYS CFX to verify the performance of the generator. As analysis conditions, numerical analysis was performed on the κ-ε, κ-ω , and SST turbulence models, and the torque for each condition was calculated to determine the output from the wind turbine. From the results of the numerical analysis, the maximum torque was calculated in the order of SST, κ-ω, andκ-εand the output was calculated in the order of SST, κ-ω, and κ-ε. The coefficient of power value was calculated as 0.225 for κ-ε, 0.236 forκ-ω, and 0.240 for SST. From the results of the numerical analysis, it was confirmed that all three conditions provided 700 W class output at a 10 ㎧ wind speed condition.

일개 보건지소에 내원한 급성기 후 코로나-19 환자들의 특성 및 한의 치료 효과 분석: 사례군 연구

유창환,김관일,정희재,이범준,Chang-hwan Yu,Kwan-Il Kim,Hee-Jae Jung,Beom-joon Lee 대한한의학회 2023 대한한의학회지 Vol.44 No.2

Objectives: The purpose of this study is to determine the clinical features of post-acute COVID-19 syndrome and the effectiveness and safety of Korean medicine treatment at the Public health center. Methods: The study was conducted among 11 patients with post-acute COVID-19 syndrome who attended a single public health center from January to December 2022. We retrospectively analyzed the charts of 11 patients and collected clinical characteristics, previous treatments, Korean medicine treatments, outcome variables (Numeral Rating Scale (NRS), Leicester Cough Questionnaire (LCQ), Visual Analog Scale (VAS)), adverse events, etc. Results: Of the 11 patients, six were women, and the average age of all patients was 68.27±12.31 years. The most common symptom were cough(n=9, 81.82%) and sore throat(n=9, 81.82%), followed by sputum, fatigue, rhinorrhea, and loss of appetite, etc. All 11 patients were treated with herbal medicine, with Samso-eum(n=6, 54.55%), Yeonkyopaedok-san(n=5, 45.45%), and Haengso-tang(n=3, 27.27%) being the most commonly used. After herbal medicine treatment, the median cough NRS decreased from 5 to 1, and the median sore throat NRS decreased from 4 to 1, both of which were statistically significant. One patient reported adverse event of dyspepsia and heartburn, but it was mild. Conclusions: The study presented the clinical features of the post-acute COVID-19 syndrome and suggested that Korean medicine treatment at public health centers may be effective and safe in alleviating associated symptoms.

단경기 사과 구매결정 요인의 중요도 분석

유창환(Chang Hwan Yu),김윤호(Yun Ho Kim) 한국농식품정책학회 2016 농업경영정책연구 Vol.43 No.4

This study aims to help growers cultivate apples and establish marketing plan to compete with imported apples, and help consumers increase purchase availability by buying preferable apples through survey and analysis on apple consumers’ purchasing status and their preferences. For the above purpose, purchasing pattern, factors affecting consumers’ preference, purchase price of apples, and purchase decision of apple consumers during off-season were analysed by surveying on 800 consumer panels living in Seoul and Gyeonggi Province. First of all, result of the purchasing pattern analysis showed that ratio of household purchasing apples during summer were 5.4% on June and 3.9% on July. Given that the average off-season purchase price of apples was higher than minimum purchase price (November, ￦2,927), it could be found that purchasing ratio of apples would increase in off-season. Moreover, binary probit model, ordered probit model, and conjoint model were used to analyze factors affecting consumer purchase and preference regarding apples during off-season. The result of conjoint analysis showed that consumers were most sensitive on ‘mouthfeel’, while considering ‘price’, ‘safety’, and ‘package’ as other critical factors. By considering the above factors, it s expected that both of growers and consumers will get better availability on cultivation and distribution of apples.

국내 외식업소 김치 소비 실태조사

유창환 ( Chang-hwan Yu ) 한국식품유통학회 2020 한국식품유통학회 학술대회 Vol.- No.하계

김치는 대한민국 식품을 대표하는 산업으로 다양한 농산물 이용에 따른 지역경제 후방 연쇄효과가 크며, 지역 농산물의 안정적 수요처 제공, 농가소득 안정화 및 증대, 지역경제 활성화 등의 효과를 기대할 수 있다. 또한 김치 수출은 국가의 역사와 문화 전달을 통한 간접적인 경제적 파급효과도 매우 큰 것으로 인식되고 있다. 현재 우리나라의 김치 제조업은 소비자의 식생활 패턴 변화, 1인당 소비량 감소, 외국산 김치 수입량 증가 등으로 연평균 가동률이 떨어지고 수익성이 악화되는 등 큰 어려움을 겪고 있다. 또한 지속적인 소비처인 외식업체들의 수요를 충족시켜주지 못해 발생하는 문제점들의 효과적인 해결과 공통의 후생 증진을 위해서 외식업체의 김치소비량, 생산 및 구입현황 등을 조사하여 김치 관련 산업의 발전과 마케팅 전략 수립을 도모할 수 있다. 본 연구는 통계청의 도소매업 및 서비스업 총 조사를 활용하여 전국 업종별 층화추출 된 요식업체 900개소를 대상으로 방문조사방식에 의해 실시되었다. 업종은 지역별로 1~4명, 5~9명, 10~19명으로 종사하는 한식, 중식, 일식, 서양식, 기타 외국음식점, 김밥 및 기타간이음식점으로 구분하고 직접 담금, 프랜차이즈 조달 현황, 유통업체 구매 등으로 나누어 조사하였다. 조사업체들은 대부분 유통업체에서 김치를 구입(63.2%)하고 다음으로 자가 제조(27.6%)하여 공급하고 있다. 그중 중식(91%)과 서양식 음식점(81%)이 유통업체 구입의존도가 높고 한식음식점은 자가 제조율(50.4%)이 높게 나타났으며 대부분의 음식점들은 수시로 김치를 담가 제공(95.2%)하고 있었다. 대체로 소비량이 많은 김치는 포기김치(74.1%), 맛김치(42.2%), 깍두기(31.8%), 열무김치(15.1%) 순으로 나타났으며, 1일 김치 소비량은 약 5kg으로 조사되었다. 계절별 김치 소비를 살펴보면 봄 맛 김치(25.8%), 여름 열무김치(63%), 가을 깍두기(28%), 겨울 총각김치(37%)가 높으며, 외식업체 김치제조시 통배추(67.5%)의 사용이 가장 많고 수입산 부재료의 사용은 고춧가루(37.2%)가 가장 높게 나타났다. 프랜차이즈 업체는 주 2회/10kg 제공, 1회 소비기간은 약 5일, 평균금액은 20,188원/10kg, 국산 제공율(51%)이 조금 높게 나타났으며, 본사 김치를 구입하는 이유는 계약 체결로 인한 사유로 조사되었다. 유통업체 구입 업체는 주 1회/9kg, 소비기간은 약 7일, 대부분 수입산 배추김치(80.9%)를 사용하고 있으며, 평균금액은 15,426원/10kg이다. 주 구입처는 대형 식자재 업체(배달)에서 수시로 구입하며, 구입이유는 직접 담그기 번거로워서(28%), 맛이 좋아서 (25%), 가격이 저렴해서(24%)로 조사되었다.

사과 농가의 위험태도 및 최적출하시기 추정 : 월별도매가격과 저장비용 중심으로

유창환 ( Chang-hwan Yu ),김민주 ( Min-ju Kim ),이상래 ( Sang-lae Lee ) 한국식품유통학회 2016 食品流通硏究 Vol.33 No.2

This study aims to prepare plans to decide safe and efficient shipping dates for apple growers, and preserve the incomes of agri-businesses by estimating absolute risk aversion coefficient of apple growers and deducing appropriate shipping dates for each risk aversion pattern using wholesale prices. In this study, for the above purpose, risk aversion pattern, optimum shipping dates for each risk aversion pattern etc. were organized by surveying on farms located in Daegu-Gyeongbuk Province which is the chief producing place of apples. The result showed that the ratios of risk aversion farms, risk neutral farms, and risk favoring farms were 62.6%, 20.5%, and 16.8% respectively and the ratio of risk aversion farms was the highest. In addition, simulation analysis and optimum shipping dates for each risk aversion farm were deduced using Kernel Density Function. It was assumed that the optimum shipping dates to receive the best sales availability were from the harvest season to the next Feb. for risk aversion farms, and from Aug. till using up the stock after shipping some on early post-harvest period for risk favoring farms. Reflected the study result on farm-training and agriculture development policy, farms would be efficiently managed such as income preservation, optimum shipping dates, and sales availability, etc.

저온저장 사과의 출하시기에 대한 실태조사 연구

유창환(Chang-Hwan Yu),김윤호(Yun-Ho Kim) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.7

본 연구의 목적은 저온저장 사과의 시장동향, 저장실태 및 출하시기 조사를 통하여 사과재배 농가들이 최적의 사과출하 시기를 결정할 수 있도록 지원하기 위한 것이다. 사과 주산지인 경상북도 대구지역의 사과재배 농가 300개소를 대상으로 설문을 실시하여 재배품종, 재배면적, 저장 및 출하실태 등을 조사하였다. 주요 연구결과는 다음과 같다. 생육시기에 따른 사과재배 비율을 조사한 결과, 조생종, 중생종 및 만생종 사과의 재배비율은 각각 78.3%, 63.7%, 96.0%였다. 또한, 조사대상 농가 중 48.7%가 저온저장시설을 보유하고 있었다. 박스(15kg) 당 평균 저장비용은 자가 저장 시에 978.3원이었으며, 위탁시에는 1,771.8원으로 나타났다. 11월부터 4월까지 6개월에 걸쳐 전체 저온저장 사과의 91.6%가 출하되고 있었다. 일반 저장 창고에 저장된 사과를 포함한 연간 사과출하량은 744.4박스였으며, 저온 저장된 사과의 연간 출하량은 616박스였다. 저장사과는 ‘도매시장’으로 출하되는 비율이 가장 높았으며, ‘산지수집상’과 ‘대형마트’가 그 뒤를 이었다. 사과의 수송방법은 일반 트럭을 이용하는 비율이 가장 높았으며, 저온탑차와 택배의 비율이 그 뒤를 이었다. 시기별 사과출하를 결정하는 요인을 분석한 결과, 오프시즌(5~월)에는 저장비용, 감모율, 관행출하 등의 영향을 받았다. 한편, 일반출하기(11~월)의 사과출하 결정요인들은 미래 기대가격, 저장비용 및 선도농가의 의사 변수가 통계적으로 유의적이었다. 일반출하의 비중이 높은 농가들의 사과 출하 결정요인은 미래에 받을 가격에 대한 기대, 저장비용, 고소득에 대한 기대, 선도농가의 의사결정에 영향을 받고 있는 것으로 나타났다. The purpose of this study is to assist farmers in determining the optimal time for the shipment of stored apples by investigating the market trends, storage status and release dates of low-temperature stored apples. We surveyed 300 apple cultivation farms in Daegu, Gyeongbuk Province, which is the main producer of apples, and examined the cultivars, cultivation areas, storage conditions, and shipment status of apples. The main results are as follows: the proportion of apples cultivatedat different ripening times was surveyed. According to the results, the proportions of early, middle and late varieties were 78.3%, 63.7% and 96.0%, respectively. Also, 48.7% of the farm households surveyed had cold storage facilities. The average storage cost per apple box(15kg) was 978.3 won for self-storage and 1,771.8 won for consignment storage. For the six(6) months between November and April, the proportion of shipped apples was 91.6% of the total stored apples. The (average total?)annual apple shipment, including apples stored in general storage warehouses, was744.4 boxes. The (average total?) annual shipment of cold storage apples was 616 boxes. The stored apples were mainly shipped to "wholesale markets", which havethe highest sales share, followed by "production site collectors" and then "supermarkets". The most common shipping method of the apples was by general trucks, followed by low-temperature trucks, and finally by delivery services. The analysis of the factors influencing the decision to release apples by period showed that it was affected by the storage cost, loss rate, and customary shipping in the off-season(from May to August). On the other hand, in the general release season(from November to April), the statistically significant decision factors forthe release of appleswere the future expected price, storage cost and decision of the leading famer groups. For farmers with a high share of general shipment, the deciding factors for the release of apples were the future expected price, storage cost, high income expectation, and decision by leading farmers.

선택실험법을 이용한 대중국 수출용 쌀 유기인증의 가치추정 - 중국 서북권역 중심으로 -

유창환 ( Yu Chang-hwan ),김태균 ( Kim Tae-kyun ),이병서 ( Lee Byong-seo ) 한국식품유통학회 2017 食品流通硏究 Vol.34 No.4

The objectives of this study are to analyze the preference of Korean rice by attribute in northwestern China consumers(Xian) by the Choice Experiment(CE) method, to identify factors that can induce the consumers to select the Korean rice, and to suggest plan for maximizing the effect of export strategy. For the purpose, of this study, We conducted consumer surveys of 701 northwestern Chinese consumers. When comparing rice from korea, China and japan, there was a statistically significant difference in the level of organic certification in the coefficient of price. However, there was no significant difference in the country of origin and the type of packaging. These results suggest that rice consumers in the northwestern region of China consider safety and price as important factors rather then their origin and type of packaging. As a result of the analysis of additional Willingness To Pay(WTP) amount based on the certification level using the conditional logit model estimation coefficient, 51 yuan / 2kg was the additional WTP with the Chinese rice certified as organic. The additional WTP with the Korean(Japanese) rice certified as organic 42 yuan / 2kg(45 yuan / 2kg), respectively. Furthermore, the additional WTP is 64 yuan / 2kg in the case the Korean rice is certified as organic by Korea and China. In the case the Japanese rice is certified by Japan and China, the additional WTP is 67 yuan / 2kg. It is considered that the organic certification of the Chinese is the most important compared to that of two others, since the additional WTP of the Chinese organic certification is higher. In addition, when Korean organic certification is added to Chinese organic certification, consumers' satisfaction of the double certification is higher than that of the single. However, the purchase intention decreases as the price increases, since the price coefficient is negative(-). As Chinese consumers regard food safety as important, it is necessary to meet their demand for safety through obtaining various certificates. Export maximization deserves much consideration by developing high-value rice products(rice processed products, functional rice, etc).

국내 절임배추 산업 현황 및 연구 개발 동향

유창환(Chang Hwan Yu),정영배(Young Bae Chung),박현석(Hyeon Seok Park),박성훈(Sung Hoon Park) 한국원예학회 2019 한국원예학회 학술발표요지 Vol.2019 No.5

국내 외 · 급식업소의 김치 소비 실태조사

유창환(Chang Hwan Yu),정영배(Young Bae Chung),박현석(Hyeon Seok Park),박성훈(Sung Hoon Park) 한국원예학회 2019 한국원예학회 학술발표요지 Vol.2019 No.5

CFD 모형을 이용한 횡월류 위어 수리특성 분석

유창환(Chang hwan Yu),주성식(Sung sik Joo),원창연(Chang yeon Won),이승오(Seung Oh Lee) 대한토목학회 2012 대한토목학회 학술대회 Vol.2012 No.10