Effects of Fouling Reduction by Intermittent Aeration in Membrane Bioreactors

최영근,김현철,노수홍,Choi, Youngkeun,Kim, Hyun-Chul,Noh, Soohong The Membrane Society of Korea 2015 멤브레인 Vol.25 No.3

The effects of relaxation and backwashing on fouling in ultrafiltration were investigated using full-scale membrane bioreactors (MBRs) which operated at a constant flux of 30 LMH. This paper also estimated the feasibility of using intermittent aeration strategies for minimizing the hydraulic resistance to filtration in comparison with the continuous aeration for running MBRs. Multiple cycles of filtration (14.5 min each) and relaxation (0.5 min each) were repeated. Similarly, a backwash was conducted by replacing a relaxation after each filtration cycle for the comparative performance test. The attached cake thickness on the membrane rapidly increased, caused by subsequent no aeration leading to easier combining with gel layer and the formation of heterogeneous layer on the membrane surface. During periodic backwashing, it is expected that gel and thin cake layer might sufficiently be removed by heterogeneous layer. After periodic backwashing, subsequent cake layer formation during time of no aeration was rapid than frequent no aeration, acting as a prefilter and preventing further irreversible fouling. Based on the Pearson correlation analysis, overall period fouling (dTMP/min) and average of all cycles (dTMP/min) were strongly correlated with the on-off period of aeration for operating MBRs.

Liquid Velocity and Local Fouling in Coagulation-submerged Microfiltration Module for Drinking Water Treatment

최영근,김현철,노수홍,Choi, Youngkeun,Kim, Hyun-Chul,Noh, Soohong The Membrane Society of Korea 2015 멤브레인 Vol.25 No.3

침지식 분리막 모듈에서 공기강도에 따른 분리막 위치에 대한 오염을 조사하였다. 분리막의 충진밀도가 낮은 곳에서 높은 유체 유속을 나타내었으며, 유체 속도는 기-액 주입률에 비례하였다. 전단응력은 기-액 주입률 및 유체 유속에 비례하였다. 비가역오염($R_{ir}$)은 흡입 압력이 가까운 부분에서 가장 높게 나타났다(position 1). 비가역오염에 대한 저항과 분리막 고유 저항의 비($R_{ir}/R_m$) 및 비가역오염에 대한 저항과 가역오염의 저항의 비($R_{ir}/R_r$)도 position 1에서 가장 높게 조사되었다. 비가역오염($R_{ir}$)은 흡입 압력이 높은 곳인 position 1에 오염물질이 축적되어진 결과이다. 분리막 위치에 따른 오염현상은 모듈 디자인 최적화에 중요한 인자임을 알았다.

Effect of Step-aeration on Inorganic Particle Mixtures Filtration in a Submerged Hollow Fiber Microfiltration Membrane

최영근,김현철,노수홍,Choi, Youngkeun,Kim, Hyun-Chul,Noh, Soohong The Membrane Society of Korea 2015 멤브레인 Vol.25 No.3

The goal is to compare two different aeration strategies for a pilot scale operation of submerged microfiltration with respect to the minimization of membrane fouling. A constant aeration (65 L/min) was examined parallel with a step-wise increase in airflow rate (40 to 65 L/min). The airflow rate was stepped to a higher rate every 5 min and the step-aeration cycles were repeated at regular intervals of 15 min. The comparative filtration runs were conducted with synthetic water containing powdered activated carbon (~10 g/L) and/or kaolin (~20 g/L) at a constant flux of 80 LMH. The extent and mechanisms of fouling in the microfiltration were identified by determining hydraulic resistance to filtration and the fouling reversibility after cleaning. Results showed that the step-aeration effectively alleviated fouling in the microfiltration of synthetic water compared to when using constant aeration. A substantial decrease in fouling was achieved by combining with coagulation using aluminum salts regardless of the aeration strategies. The constant aeration resulted in increased pore blocking likely due to increased accumulation of particles on the surface of membrane.

기독교대학의 정체성 변화과정에 관한 연구 - 미국 아그네스스캇대학(Agnes Scott College)의 사례 연구-

최영근 ( Youngkeun Choi ) 한국대학선교학회 2020 대학과 선교 Vol.43 No.-

This paper deals with a case of Agnes Scott College established in 1889 by the Presbyterian Church (U.S.A.) to investigate the ways in which the Christian identity has been maintained and changed in a long period of time when a Christian university has developed. As a historical study it reviews primary sources of the college including historical narratives, annual reports, catalogues, magazines, and other documents as well as secondary materials. Seeking a high-level Christian liberal arts college for women, Agnes Scott College has strived to unite the Christian faith and academic excellence, and developed into a scholarly open-minded Christian but not sectarian college: accepting students with no regard to their religious traditions or non-religious belief; employing the faculty and staff members under conditions they would consent to the Christian identity of the college; and inviting various persons from outside Presbyterian or Christian religion to board of trustees. Although a strong Christian identity diluted so far, the college in pluralistic culture is still struggling to keep and apply the Christian values to its academic and spiritual life, and their efforts will give a precedent lesson to the Christian universities in Korea as well.

일제강점기 미국 남장로회 교육선교에 관한 연구 - 군산과 전주스테이션의 인돈(William A. Linton)을 중심으로, 1912-1940 -

최영근 ( Youngkeun Choi ) 한국대학선교학회 2021 대학과 선교 Vol.50 No.-

This research focuses on William A. Linton’s educational missions at Gunsan and Jeonju from 1912 to 1940, displaying the historical meaning and Christian legacy of the educational work of the Southern Presbyterian mission in Korea under Japanese colonialism. A particular attention is paid on the ways in which the Southern Presbyterian mission had been maintaining the consistent purpose of their educational work and responded to the changes of the Japanese colonial educational policy: dialectical relations with the Japanese showing conformity and resistance as well as having cooperation and conflict. Linton regarded Christian education as the best duty of the Protestant missions to Korea and considered the educational work the best way to evangelism. For this regard, he endeavored to improve school equipment and educational level to make mission schools competitive with Japanese government schools. However, he took an uncompromising stand against the Shinto-shrine worship enforced to mission schools by the Japanese government and carried out the closing of all the Southern Presbyterian mission schools. The efforts of the Southern Presbyterian mission to keep the purpose of educational work under the Japanese colonial educational system will set the pattern for the Christian university, whose Christian identity has been challenged under the public educational system calling for religious freedom. They teach a way of response for maintaining the goal of the Christian education as well as meeting the demands of the times.

민족주의에 대한 비판적 성찰을 통한 한국 기독교와 민족주의 접합에 관한 소고

최영근(CHOI Youngkeun) 장로회신학대학교 기독교사상과 문화연구원 2017 장신논단 Vol.49 No.1

신기술 기반 벤처기업에서 창업자의 인적 자본 특성과 기업공개 소요 기간과의 관계에서 벤처캐피탈 투자의 매개효과

최영근(Choi, Youngkeun),정승화(Chung, Seungwha),임지선(Lim, Ji Sun) 한국인사관리학회 2011 조직과 인사관리연구 Vol.35 No.3

본 연구의 목적은 신기술 기반 벤처기업에서 창업자의 인적 자본 특성들이 자원 보유자인 벤처캐피탈의 투자 결정에 미치는 영향과 이를 매개로 기업공개 소요 기간이 단축되는지를 실증적으로 규명하는 것이다. 기존 연구들은 주로 제3자의 사회적 인정 또는 특허 등이 외부 자원을 유인하는 신호로 작용하여 필요한 자원을 보충할 수 있기 때문에 기업공개 소요 기간이 단축될 수 있다고 주장하고 있다. 그러나 이러한 신호들로 인해 자원 보유자들이 자신들의 자원 공급을 실제로 결정하는지를 보여주지 못하고 있다. 이에 본 연구는 신기술 기반 벤처기업에서 창업자의 인적 자본 특성이 대표적인 자원 보유자인 벤처캐피탈의 투자를 유인하는지를 실증적으로 규명하고, 벤처캐피탈 투자의 매개효과를 검증하였다. 실증 분석 결과, 창업자의 나이가 젊을수록, 명문 대학 출신인 경우, 기능적 배경이 아웃풋인 경우, 관련 업종 경험이 있을 경우 벤처캐피탈의 투자를 유치할 가능성이 높으며 이를 매개로 기업공개 소요 기간이 짧아지는 것을 발견하였다. 반면 창업자의 교육 수준은 유의한 관계를 보이지 않았다. The purpose of this study is to investigate the signaling effect of founders’ human capitals in new technology based ventures which attract venture capitals’ investment and the mediating effect of venture capitals’ investment on the relationship between founders’ human capital and time to IPO. Previous studies present the endorsement by third parties as a signaling factor which attract external resources from resource-holder and ventures can acquire the requisite resource, which in turn they can shorten time to IPO. But they do not show actually if resource holders make decision to provide their resources by the signals. This study examine empirically that founders’ human capitals in new technology based ventures lure the venture capitals’ investment and the mediating role of venture capitals. In the results, we found that four factors attract the venture capitals’ investment: the younger founders are and when the founders graduate from elite school, possess output function background, and experience relevant industry and they shorten time to IPO mediated by venture capitals’ investment. However, educational level showed no significance.

일제강점기 유화례(Florence E. Root)의 전도활동, 1927-1942

최영근 ( Choi Youngkeun ) 한국교회사학회 2022 韓國敎會史學會誌 Vol.63 No.-

This paper examines the significance of the evangelical work by Florence E. Root, a single woman missionary for the Southern Presbyterian mission. Focusing on her evangelism from 1927 to 1942 until its discontinuation under the threat of the Japanese wartime system, her awareness of Korean church and society, the consciousness of evangelism and education for women, and the attitude toward the Japanese colonial rule over Korea is investigated. This research on the evangelism of Root shows that she neither agreed nor blamed the fall of the Korean church into a patriotic institution for war mobilization under the threat of the Japanese but consoled and encouraged them while maintaining the principle and purpose of her mission to Korea undauntedly under pressure and disturbance by the authorities. She visited women in the backcountry and conducted evangelism, providing basic educational opportunities to the unschooled. She trained women into active leaders through Bible education for women centered in Bible classes as well as Bible institutes and schools run by the Southern Presbyterian mission, contributing to the growth of the Korean church. This is one of the major evangelical methods of the mission for the development of the church, and her evangelical work as a case displayed the entire process. She initially regarded evangelism as a way of cultural improvement, leading an uncivilized society to a modern civilization, as well as the light of the gospel. Later encouraged by a revival experience, she acknowledged the remarkable commitment of the Koreans to the gospel despite difficulties as well as the Japanese suppression, thus changing her view of the mission. She concentrated on the soul of the people and became enrooted in Korea. Root and the Korean church under the Japanese threat tied together with mutual support and care, which encouraged her to stay in Kora and perform evangelism.

일중독과 직무열의의 결과변수에 대한 비교 연구

최영근(Youngkeun Choi),김규배(Jyubae Kim) 대한경영학회 2012 대한경영학회 학술발표대회 발표논문집 Vol.2012 No.2

본 연구는 일중독과 직무열의의 통합모형을 통해서 개념적 및 실증적으로 두 변수의 차이를 입증하고자 하였다. 이를 위해 두 개념의 결과변수들을 비교하여 분석하였다. 일중독과 직무열의는 오랜 시간 일한다는 공통적인 특성을 보이고 있어 외견적으로 구별하는데 어려움이 있다. 이로 인해 학문적으로도 일중독에 관해 연구결과가 일관성을 보이고 있지 않은 것이 현실이다. 기존 연구들은 두 개념과 관련하여 별도의 결과변수 또는 동일한 결과변수들을 각 개념의 독립된 연구모형에서 제시하고 있다. 이에 본 연구에서는 두 개념의 차이를 구별하기 위해서 동일한 결과변수에서 다른 관계성을 보이고 있음을 이론적 및 실증적으로 입증하였다. 연구 결과는 다음과 같다. 첫째, 일중독이 심할수록 구성원의 직무만족도는 떨어지는 반면 직무열의는 높을수록 직무만족도는 증가하였다. 둘째, 일중독이 심할 수록 일-가정 갈등이 심해지는 반면 직무열의는 높을 수록 일-가정 갈등이 감소하였다. 셋째, 일중독이 심할수록 구성원의 조직시민행동은 감소하는 반면 직무열의는 높아질수록 조직시민행동은 증가하였다. 넷째, 일중독 성향이 높은 구성원이나 직무열의가 높은 구성원 모두 이직의도가 낮은 것으로 나타났다. This study is to investigate the difference between wokaholism and job engagement throuth the integral research model conceptually and empirically. To do this, we compare and annalize the dependent variables of these concepts. It is difficult to distinguish workaholism from job engagement, for both of the concepts have the common characteristics of long-time working. Therefore, the results of study of workaholism are not consistent. The existing studies suggest the its own research model respectively. To distinguish the difference between these two concepts, we suggest the integral research model and verify that they show the different relationships with the same dependent variables. The results are followings. First, workaholism has negative ralationship with job satisfaction, while job engagement has positive one. Second, the more workaholism a employee has, the more work-family conflict he or she suffer from, while the more job engagement he or she has, the less work-family conflict he or she does. Third, workaholism decreases the organization citizenship behavior of a employee, while job engagement increase it. Finally, both of workaholism and job engagement show the low level of turnover intention.

미국 남장로회 선교사 김기수(Keith R. Crim)의 한국선교: 대전스테이션 활동(1954 -1965)을 중심으로

최영근(Youngkeun Choi) 연세대학교 신과대학(연합신학대학원) 2020 신학논단 Vol.100 No.-

This paper investigates the missionary work of Keith R. Crim at the Daejeon Station of the Korea Mission of the Presbyterian Church in the United States (the Southern Presbyterian Church) by examining primary sources such as the minutes of the Korea Mission, missionary letters, and other historical materials. It aims at reviewing his role in establishing the Daejeon Station and his educational work at the Taejon Presbyterian College while clarifying his mission theology. This paper historically reconsiders the significances of the missionary work of the Korea Mission of the Southern Presbyterian church in the 1950s and the 1960s while reviewing Crim’s distinctive theological positions – accepting historical criticism of the Bible, avoiding theological fundamentalism, and emphasizing ecumenical movements – within a theologically conservative tradition of the Southern Presbyterian mission. It seeks to interpret the significance and limitation of the Southern Presbyterian missionary works to the Korean church and society in the 1950s and the 1960s – at the time of a radical social change of Korea and the great schism in the Presbyterian church. Keith R. Crim emphasized the necessity of evangelical work comforting and caring for laborers suffered from the poor working conditions in the rapid industrial development of Korea. For the Korean Church, he highlighted a scholarly interpretation of the Bible while avoiding the fundamentalist literalism, and emphasized the biblical inspiration as well as staying away from theological liberalism. He prescribed ecumenicalism to treat the great schism of the Korean Presbyterian Church while maintaining love and unity in Christ.