관 내 삽입 인젝터와 싸이클론을 이용한 공기 가습

김범준(Beom Jun Kim),김성일(Sung Il Kim),김민수(Min Soo Kim),김현유(Hyun Yoo Kim),권혁률(Hyuck Ryul Kwon) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

Humidification using water spray has been applied to humidification and cooling of air in a building. And there are many other applications. Recently, this method of humidification has been considered to be applicable to humidification in a fuel cell vehicle. Air in a fuel cell Vehicle should be humidified much higher than that in a building. In addition, a vehicle has limited space. so the volume of a humidification system should be small. In this study, the humidifier has an injector directly installed in a pipe of air supply to reduce the size of humidifier, and a reverse flow cyclone is used to remove water droplets. Thee types of injector of BETE company were used in these experiments. And by varying injection pressure, air flow rate, and injection direction, experiments were performed. Without any heat exchanger, only enthalpy of water and air is the source to provide latent heat for evaporation. As a result, to increase humidification performance, the amount of water was the most critical factor to increase humidification performance. With high pressure, we could obtain fine atomization, and this increased the humidification efficiency. Cyclone removed water droplets well. However at high air flow rate, re-entrainment occurred, because its conic lower part was short due to size limitation. To increase efficiency of droplet removal and for smaller size, a different type of cyclone like axial flow cyclone is applicable.

관 내 삽입 인젝터와 사이클론을 이용한 공기 가습

김범준(Beom Jun Kim),김성일(Sung Il Kim),변수영(Su Young Byun),김민수(Min Soo Kim),김현유(Hyun Yoo Kim),권혁률(Hyuck Ryul Kwon) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.5

연료전지 자동차는 성능과 수명 측면에서, 전해질막의 가습이 필요하며, 이를 위해 반응기체인 공기, 수소의 높은 가습이 요구된다. 본 연구에서는 내경 75 ㎜공기공급관 내에 직접 삽입된 인젝터(노즐)과 액적제거를 위한 사이클론을 통한 가습장치를 고안하여 실험을 수행하였다. 충돌형 노즐 3 종류를 이용하여 분사압력, 공기 유량, 분사방향각도를 달리하여 실험을 수행하였다. 가습 성능을 분석하기 위해, 가습효율이라는 개념을 정의하였다. 별도의 외부 열공급원 없이 분사되는 물과 공기의 엔탈피가 자체 기화열 공급원으로, 분사되는 물의 양이 가습에 가장 중요한 변수임을 볼 수 있었다. 사이클론은 높은 공기유량에서 재비산이 발생되는 것을 볼 수 있었다. 노즐타입 PJ24, 분사방향 각도 90도, 분사압력 1200 ㎪, 공기 유량 6000 nlpm에서 절대습도 21.29 kJ/㎏da , 가습 효율 86.57%를 얻을 수 있었다. Humidification of PEM fuel cells is necessary for enhancing their performance and lifetime. In this study, a humidification system was designed and tested; the system includes an air-supply tube (inner diameter: 75 ㎜) through which a nozzle can be directly inserted and a cyclonic separator for the removal of water droplets. Three types of nozzles were employed to study the influence of injection pressure, air flow rate, and spray direction on the humidification performance. To evaluate the humidification performance, the concept of humidification efficiency was defined. In the absence of an external heat source, latent heat for evaporation will be supplied by the own enthalpies of water and air. Thus, the amount of water sprayed from the nozzle is the most critical factor affecting the humidification efficiency. Water droplets were efficiently removed by a cyclonic separator, but re-entrainment occurred at high air flow rates. The absolute humidity and humidification efficiency were 21.29 kJ/㎏da and 86.57%, respectively, under the following conditions: nozzle type PJ24; spray direction angle 90°; injection pressure 1200 ㎪; air flow rate 6000 Nlpm.

외래품종과일 구매빈도에 영향을 미치는 요인 분석

김현유(Hyunyu Kim),강혜정(Hye-Jung Kang) 한국농업경제학회 2021 農業經濟硏究 Vol.62 No.2

This study investigates the factors affecting the purchase frequency of foreign-species fruits, using the panel data of ｢Food Consumption Behavior Survey｣ from Korea Rural Economic Research Institute for the period from 2017 to 2020. The recursive bivariate ordered probit model is applied to consider the dependent correlation between the purchase frequency of foreign-species fruits and the purchases frequency of common fruits in estimating the model. The results find that the higher the purchase frequency of fruits, the higher the purchase frequency of foreign-species fruits was statistically significant, indicating that households who consume more fruits also purchase more foreign-species fruits. It can be seen that consumers are young, high-educated and high-income groups. Also, the information provided through SNS has been shown to have a positive effect on the purchasing power of foreign-species fruits, suggesting the importance of social networks as a promotional method to expand consumption of fruits including foreign-species fruits.

초미립 분말 고성능 초속경 시멘트와 오염수 정화순환 시스템 장비를 이용한 시멘트 콘크리트 교면포장 보수공법(SRP-CON공법) (건설신기술 931호)

김현유(Hyun Yu Kim),이중범(Jung Bum Lee),강일환(Il Hwan Kang) 대한토목학회 2022 대한토목학회지 Vol.70 No.10

인젝터 누설량에 의한 시동성 영향에 대한 실험적 연구

김현유(Hyeongyoo Kim),유승묵(Seungmook You),양승욱(Seungwook Yang) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

The start-ability is one of the most important factors for developing a vehicle and is strongly dependent on the essential sensors and actuators such as an air flow meter and injectors. So far we've been making every effort to calibrate data related to start-ability according to the flow rate of an injector. But, we've not focused on the influence of the injector-leakage on start-ability. In this study, we made several combinations of injectors which have different leakage levels and then tested the start-ability with them. As a result of the experiments, the starting was delayed in some cases, and we conclude the relationship between the injector-leakage and the delay of starting. To resolve the start-delay problem caused by the injector-leakage, it is recommended to reduce the fuel quantities during engine starting, but this fuel reduction can also affect the start-ability using low RVP fuels of under the other conditions. And we found experimentally the specification of injector-leakage and the minimal reduction ratio of fuel needed to start an engine stably even with low RVP fuels and high leakage injectors.

용매 추출 재생 기반의 재생재 함량과 소재 조성비에 따른 ABS(Acrylonitrile Butadiene Styrene)의 장단기 물성 및 파단면 분석

김동욱(Donguk Kim),강병현(Byunghyun Kang),손주성(Joo Seong Sohn),박노철(Noh Cheol Park),김현유(Hyun Yoo Kim),박지권(Jeekwon Park),고영덕(Youngdeog Koh),최병호(Byoung-ho Choi) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11

외국인 관광객 리뷰데이터를 활용한 토픽모델링 기반의 공간분석: 대구광역시를 사례로

정지우,김서윤,김현유,윤주혁,장원준,김건욱,Jung, Ji-Woo,Kim, Seo-Yun,Kim, Hyeon-Yu,Yoon, Ju-Hyeok,Jang, Won-Jun,Kim, Keun-Wook 한국디지털정책학회 2021 디지털융복합연구 Vol.19 No.8

스마트폰 기반의 관광 플랫폼들이 활성화되면서 리뷰 데이터를 활용한 정책 수립 및 서비스 고도화가 다양한 분야에서 이루어지고 있다. 관광 리뷰 데이터를 활용한 선행연구들의 경우 국내 관광객 중심의 연구가 대다수 수행되었으며, 외국인 관광객 연구의 경우 일부 언어로 수집된 데이터와 텍스트 마이닝 기법에 한정하여 연구가 수행되었다. 이에 본 연구에서는 온라인 리뷰 사이트를 통해 '대구 명소' 키워드를 지정하여 외국인들이 작성한 리뷰 데이터 3,515건을 수집하였다. 그리고 LDA 기반의 토픽모델링을 수행하여 관광 토픽을 도출하였으며, 각 토픽별 전역 및 국지적 공간 분석을 수행한 점이 선행연구와 차별성이라 할 수 있다. 분석 결과 전역적 공간 자기상관이 존재하며, 외국인들이 주로 방문하는 관광지들이 국지적으로 결집되어 있음을 확인하였다. 또한 대다수 토픽에서 중구를 중심으로 핫스팟이 도출되었으며, 분석 결과를 바탕으로 지자체 외국인 관광정책 수립 및 토픽모델링 기반의 공간분석 연구의 기초연구로 활용되길 기대하며, 본 연구의 한계점 또한 제시하였다. As smartphone-based tourism platforms have become active, policy establishment and service enhancement using review data are being made in various fields. In the case of the preceding studies using tourism review data, most of the studies centered on domestic tourists were conducted, and in the case of foreign tourist studies, studies were conducted only on data collected in some languages and text mining techniques. In this study, 3,515 review data written by foreigners were collected by designating the "Daegu attractions" keyword through the online review site. And LDA-based topic modeling was performed to derive tourism topics. The spatial approach through global and local spatial autocorrelation analysis for each topic can be said to be different from previous studies. As a result of the analysis, it was confirmed that there is a global spatial autocorrelation, and that tourist destinations mainly visited by foreigners are concentrated locally. In addition, hot spots have been drawn around Jung-gu in most of the topics. Based on the analysis results, it is expected to be used as a basic research for spatial analysis based on local government foreign tourism policy establishment and topic modeling. And The limitations of this study were also presented.

단방향 링크를 지원하는 이동 Ad Hoc 라우팅 프로토콜

이광배,김현유,정근원,Lee, Kwang-Bae,Kim, Hyun-Ug,Jung, Kun-Won 한국전기전자학회 2001 전기전자학회논문지 Vol.5 No.1

본 논문에서는 단방향 링크를 포함하는 이동 Ad Hoc 망에 대해 비대칭 경로를 지원하는 동적 소스 라우팅 프로토콜을 제안하였다. 기존의 동적 소스 라우팅 프로토콜은 양방향 링크로 구성된 대칭경로만을 지원하도록 구현되어있다. 그러나 실제적인 무선환경에서는 단말의 비대칭성이나 무선환경 특성등에 기인한 단방향 링크가 존재할 수 있다. 따라서 본 논문에서는 좀 더 일반적인 무선환경에 맞는 이동 Ad Hoc 망 라우팅 프로토콜을 구현하기 위하여 단방향 링크를 지원하도록 하였다. 특히 이동성으로 인한 경로 실패를 인식한 경우, 신속한 경로 재설정을 수행하기 위해 다중경로유지 기법을 사용하였다. 성능평가는 평균 경로설정시간 및 평균 데이터수신율에 대해 수행하였으며, 그 값을 얻기 위해 경로 상에 중간노드캐쉬의 사용여부 및 서로 다른 이동성과 연결성을 제공하는 시나리오를 고려하여, 100초 단위로 900초까지 성능평가를 수행하였다. In this paper, we propose a dynamic source routing protocol supporting asymmetric paths for mobile Ad Hoc networks that contain unidirectional links. At present, the existing dynamic source routing protocol supports only symmetric paths that consist of bidirectional links for routing. However, in fact, there can exist unidirectional links due to asymmetric property of mobile terminals or current wireless environment. Thus, we implement a mobile Ad Hoc routing protocol supporting unidirectional links, which is fit for more general wireless environment. Especially, the proposed protocol uses an improved multipath maintenance method in order to perform rapid route reconfiguration when route error due to mobility is detected. For performance evaluation, we consider the following factors: average route discovery time and average data reception rate. In order to obtain the factors of the performance evaluation, we did simulation for 900 seconds in the step of 100 seconds with the following scenarios: usage of route cache in intermediate nodes on route path, and different mobility/connection patterns.

전자밀도함수이론을 이용한 세륨 산화물의 (111) 표면에서 일어나는 물 흡착 과정 분석

최혁,강은지,김현유,Choi, Hyuk,Kang, Eunji,Kim, Hyun You 한국재료학회 2020 한국재료학회지 Vol.30 No.5

Cerium oxide (ceria, CeO₂) is one of the most wide-spread oxide supporting materials for the precious metal nanoparticle class of heterogeneous catalysts. Because ceria can store and release oxygen ions, it is an essential catalytic component for various oxidation reactions such as CO oxidation (2CO + O₂ 2CO₂). Moreover, reduced ceria is known to be reactive for water activation, which is a critical step for activation of water-gas shift reaction (CO + H₂O → H₂ + CO₂). Here, we apply van der Waals-corrected density functional theory (DFT) calculations combined with U correction to study the mechanism of water chemisorption on CeO₂(111) surfaces. A stoichiometric CeO₂(111) and a defected CeO₂(111) surface showed different water adsorption chemistry, suggesting that defected CeO₂ surfaces with oxygen vacancies are responsible for water binding and activation. An appropriate level of water-ceria chemisorption energy is deduced by vdW-corrected non-local correlation coupled with the optB86b exchange functional, whereas the conventional PBE functional describes weaker water-ceria interactions, which are insufficient to stabilize (chemisorb) water on the ceria surfaces.

건식 환원 공정을 이용한 고순도 주석 회수

이상로,이만승,김현유,Lee, Sang-Ro,Lee, Man-Seung,Kim, Hyun You 한국자원리싸이클링학회 2015 資源 리싸이클링 Vol.24 No.3

주석을 함유한 폐기물에서 고순도 주석을 회수하는 기술을 개발하기 위해 주석오니의 환원 제련 및 전해정련에 대해 연구하였다. 2단계의 건식제련을 통해 주석오니에 함유된 주석산화물을 환원시켜 92.7%의 주석을 회수하였다. 또한 건식공정으로 회수한 조주석을 전해정련시켜 순도를 99.87%까지 증가시켰다. 본 연구결과는 국내에서 발생하는 폐자원으로부터 주석을 회수하여 국내 주석 소비량의 일부를 대체할 수 있는 상용화기술의 토대가 될 수 있다. In order to develop a technology for the recovery of pure tin from the Sn containing industrial wastes (SIWs), a process consisted of high temperature reduction and electrorefining was investigated. The tin which exists as oxide in SIWs was successfully reduced by two consecutive high temperature treatments and 92.7% of the tin was recovered. The purity of the tin thus obtained was increased to 99.87% by electrorefining. By applying the results obtained in this work, a commercial process can be developed to produce pure tin metals from domestic spent resources, which can reduce the amount of tin imported from abroad.