http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
저온 외기조건에서 케스케이드 급탕열펌프의 성능특성에 관한 해석적 연구
송재현(Jaehyun Song),정해원(Haewon Jung),박재우(JaeWoo Park),강훈(Hoon Kang),김용찬(Yongchan Kim) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.5
Heat pump systems have been widely adopted in buildings for cooling and heating, due to their higher energy efficiency. Recently, the demand for hot water supply from the heat pump system has been increasing. To increase the water supply temperature with higher system efficiency and reliability, a heat pump water heater adopting cascade cycle was investigated in this study. The cascade heat pump water heater consisted of a low-stage cycle using R410A, and a high-stage cycle using R134a. A simulation program for the cascade heat pump water heater was developed, and verified by comparison with experimental data. The performance of the cascade heat pump water heater was optimized, by varying the compressor rotating speeds of the low- and high-stage cycles. At low ambient temperatures, the performance of the cascade cycle was compared with that of the single-stage cycle. The system efficiency of the cascade cycle was higher than that of the single-stage cycle, showing a lower compression ratio and compressor discharge temperature.
백종석,김치영,이기성,강현웅,송재현,Baek, Jongseok,Kim, Chiyoung,Lee, Kisung,Kang, Hyunwoong,Song, Jaehyun 한국수자원학회 2020 한국수자원학회논문집 Vol.53 No.12
For integrated water management, it is essential to secure basic data such as the amount of agricultural water intake. The river water intake through the intake weir is carried out through the agricultural irrigation canal, and a method for measuring the quantity of water intake is required to suit the characteristics of the measuring points. In this study, the accuracy of the calculated flow data was determined by applying a microwave water surface current meter. The microwave water surface current meter is a method of calculating surface velocity using doppler effect, which is mainly used in high-velocities situations such as flood. Surface velocity is difficult to represent the average velocity of the entire section at low dicharges or high wind speeds, it is considered to be low in continuous utilization throughout the year, and it is necessary to verify whether the measurement using an microwave water surface curren meter is appropriate in agricultural irrigation canal. The data measured with an microwave water surface curren meter were compared with the actual flow data to calculate the intake data in agricultural irrigation canal. In agricultural irrigation canal, the low-level discharge calculated using an microwave water surface current meter at a minimum velocity of about 0.3 m/s and a minimum discharge of about 1.0 m3/s or higher was found to have a high tendency and accuracy compared to the standard discharge, especially when the high discharge was high. Although effective results can be obtained in terms of quantity at low discharge, it is deemed that subsequent studies are needed to calculate the average discharge of the cross section at low discharge, given that the trend of data is unstable. Through this study, it is suggested that it is appropriate to calculate the amount of water intake through the microwave water surface current meter in artificial waterways with a certain discharge or higher, so it is expected to be widely distributed as a method for measuring river water intake.
하천수 사용량 계측을 위한 개수로에서의 직접 계측방법 비교 연구
백종석,김치영,이기성,강현웅,송재현,Baek, Jongseok,Kim, Chiyoung,Lee, Kisung,Kang, Hyunwoong,Song, Jaehyun 한국방재안전학회 2020 한국방재안전학회 논문집 Vol.13 No.4
Continuous and accurate instrument of river water usage is needed for sustainable river water management. Although the instrument methods applicable to each point of use of river water are different, more precise direct instrument methods are required at the point of major open channel. Users of river water should select appropriate direct instrument methods to measure usage, but there is a lack of standards and verification research. In this study, the H-Q rating curve method, ultrasonic method, and microwave method were applied directly to the test basin in the upper basin of Mangyeong river, and the accuracy of measurement data was evaluated by comparing absolute error between discharge data calculated by instrument method. When comparing the calculated discharge of point units, the ultrasonic method showed the best results of the actual measurement. Through continuous instrument, the sum of the daily and monthly units was compared, and the ultrasonic and microwave methods were shown to be highly accurate. Based on the results of this study, it is hoped that the appropriate direct measurement method can be selected according to the importance of the river water use facility, considering that the ultrasonic method and the microwave method are relatively costly compared to the water level-flow relationship method. 지속가능한 하천수 관리를 위해서는 연속적이고 정확한 하천수 사용량 계측자료가 필요하다. 하천수 사용지점별로 적용가능한 계측 방법이 상이하나, 일정규모 이상의 주요 개수로 지점에서는 보다 정밀한 직접 계측방법이 요구된다. 하천수 사용자는 사용량 계측을 위해 적정한 직접 계측방법을 선정해야 하는데, 이에 대한 표준 및 검증 연구가 부족한 실정이다. 본 연구에서는 만경강 상류의 시험유역에 직접 계측방법인 수위-유량관계법, 초음파법, 전자파법을 적용하였고, 계측방법별로 산정된 유량자료간의 절대오차 비교를 통해 계측자료의 정확도를 비교 평가하였다. 점단위 산정유량 비교시 초음파법이 실측값에 가장 근사한 결과를 보였다. 연속적인 계측을 통해 일단위와 월단위의 총량을 비교하였고, 초음파법과 전자파법이 정확도가 높은 것으로 나타났다. 본 연구의 결과를 토대로 초음파법과 전자파법이 수위-유량관계법에 비해 비교적 높은 비용이 투입되는 것을 감안하여 하천수 사용시설의 중요도에 따라 적정한 직접 계측방법을 선정할 수 있기를 기대한다.
김양선(Yangson Kim),송재현(Jaehyun Song),이은혜(Eunhye Lee) 한국교육재정경제학회 2011 敎育財政 經濟硏究 Vol.20 No.3
이 연구는 대학의 내부자원과 국제화 전략에 근거하여 대학을 유형화하고 각 유형별로 국제화 성과에 차이가 있는지 탐색하는 것을 목적으로 한다. 이를 위해 181개 4년제 대학 본교 중 164개 대학을 분석 대상으로 선정하고 해당 대학의 2009년 대학알리미 자료를 활용하였다. 대학별 전략을 유형화하고 대학 간 차이를 살펴보기 위해 키워드분석과 일원배치 분산분석(ANOVA) 및 Kruskal-Wallis 분석을 실시하였다. 그 결과 대학이 추진하는 국제화 전략은 그들이 보유한 물적, 재정, 인적, 조직의 네 가지 내부 자원에 따라 분류할 수 있었으며, 그 중 인적 자원과 조직 자원에 기반한 국제화 전략이 가장 일반적이었다. 또한 각 대학의 내부 자원과 관련전략 유무에 근거하여 대학을 분류하고 그들 간의 국제화 성과를 비교하였을 때, 집단 간의 차이를 발견하였다. 이후 사후 검증을 통해서 자원에 기반한 전략의 유무보다는 자원 확보 그 자체가 국제화 성과에 더 큰 차이를 가져온다는 것을 확인하였다. 이러한 연구 결과는 대학의 성공적인 국제화를 위해서는 무엇보다 필요한 자원을 우선적으로 확보하는 것이 중요하며, 각 대학의 특성과 현실에 맞는 전략 추구가 필요하다는 점을 시사한다. The purpose of this article is to categorize Korean universities based on their internationalization strategies and to explore whether there are differences in internationalization performance by types. To achieve this purpose, 164 out of 181 four-year universities were analyzed with the data published by the center for Higher Educational Information Disclosure. This study classified the strategies for internationalization into the four categories according to the four types of the internal resources that the universities have - physical, financial, human, and organizational resources - and found that the strategies related to the human and organizational resources are the most common among the four categories of the strategies. In this study, the universities are also categorized into the four groups based on the two standards - the levels of the internal resources that each university has and the existence of the strategies pertinent to the resource types. It is found from analyses of one-way ANOVA and Kruskal-Wallis that the internationalization performance of the four groups are different . The result of the posteriori test indicates that the internal resources that universities hold have more impacts on the internationalization performance than the strategies for internationalization. It implies that securing the resources needed for internationalization should be a priority and universities need to develop the realistic strategies for internationalization considering their resources and features.