정전분무 열분해법에 의한 나노분말의 제조 및 하이드록시 아파타이트 형성능력 평가

이영환,전경옥,전영선,이지창,황규석,Lee, Young-Hwan,Jeon, Kyung-Ok,Jeon, Young-Sun,Lee, Ji-Chang,Hwang, Kyu-Seog 한국결정성장학회 2006 韓國結晶成長學會誌 Vol.16 No.6

본 연구에서는 새로운 나노 분말 제조방법 중의 하나인 정전분무 열분해법을 이용하여 칼슘 포스페이트 나노분말을 제조하였다. 정전 분무된 분말은 공기 중에서 $400^{\circ}C$로 30분간 열처리하여 고상화하였다. 결정화된 분말의 하이드록시 아파타이트 형성능력을 평가하기 위하여 Eagle's minimum essential medium solution(MEM)을 사용하였으며, MEM 용액에 침전된 후의 분말의 특성평가를 위하여 X-선 회절 분석법, 전계 방사 주사형 전자 현미경, 에너지 분산 X-선 분광계 및 퓨리에 변환 적외선 분광계를 사용하여 분석을 행하였다. 비정질 구조를 가진 나노 분말은 MEM 용액에 15일 침전 후, 분말의 표면에 유도된 하이드록시 아파타이트 결정을 확인할 수 있었다. Electrostatic spray pyrolysis, a novel fabrication technique, has been used in this study to prepare calcium phosphate nano powders. Final annealing was done at $400^{\circ}C$ for 30min in air. The hydroxyapatite - forming ability of the annealed powder has been evaluated in Eagle's minimum essential medium solution (MEM). X-ray diffraction analysis, field emission - scanning electron microscope, energy dispersive X-ray spectroscope, and Fourier transform infrared spectroscope were used to characterized the annealed powders after immersion in MEM. The powder with an amorphous structure induced hydroxyapatite formation on their surfaces after immersion fer 15 days.

E-commerce Architecture Evaluation Through Web Stress Test

이영환,박종순,Lee, Young-Hwan,Park, Jong-Soon 한국경영정보학회 2001 Information systems review Vol.3 No.2

Of critical importance to the success of any e-commerce site are the two factors: rapid application development and quick response time. A three-tier architecture composed of presentation layer, business layer, and data access layer emerges to allow rapid changes in user interface, business logic, and database structures. Too often, such a logical three-tier architecture is considered as requiring a three-tier physical architecture: Web server, application server, and database server running on separate computers. Contrary to the common belief, a Web stress test reveals that the three-tier logical architecture implemented on a two-tier physical platform guarantees a quicker response time due to the reduction in cross-machine communications. This would lead business firms to economize their spending on e-commerce: increasing the number of physical servers to expedite transaction is not necessarily the best solution. Before selecting a particular hardware configuration, a Web stress test needs to be conducted to compare the relative merits of alternative physical architectures. Together with capacity planning, Web stress test emerges as a powerful tool to build robust, yet economical e-commerce sites.

미술관에 간 의학자

이영환,Lee, Young Hwan 연세대학교 의과대학 2019 의학교육논단 Vol.21 No.3

'전문직업성'을 넘어 '전문직 정체성 형성'으로

이영환,Lee, Young Hwan 연세대학교 의과대학 2021 의학교육논단 Vol.23 No.2

유기발광 소자에서 유기층의 두께 및 증착속도 변화에 따른 전기적 특성

이영환,김원종,양재훈,신종열,김태완,홍진웅,Lee, Young-Hwan,Kim, Weon-Jong,Yang, Jae-Hoon,Shin, Jong-Yeol,Kim, Tae-Wan,Hong, Jin-Woong 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.4

OLEDs(Organic Light Emitting Diodes) are attractive as alternative display components because of their relative merits of being self-emitting, having large intrinsic viewing angle and fast switching speed. But because of their relatively short history of development, much remains to be studied in terms of their basic device physics and design, manufacturing techniques, stability and so on. We investigated electrical properties of N, N-diphenyl-N, N bis (3-methyphenyl-l,1'-biphenyl-4,4'-diamine (TPD) and tris-8-hydroxyquinoline aluminum$(Alq_3)$ when their thicknesses were changed variedly from 3:7 to 5:5 of their thickness ratios. And we also studied properties of OLED depend on their deposition rate between $0.05{\sim}0.2$ nm/s.

전문직업성 배양을 위한 의학교육

이영환,Lee, Young-Hwan 연세대학교 의과대학 2012 의학교육논단 Vol.14 No.1

The purpose of this article is to discuss the enhancement of medical professionalism and the artisan spirit proposed by Yu and to suggest curriculum content and methods to improve medical professionalism. Professionals are those who can share their knowledge with others and proceed under self-reflection on moral values and social expectations. The goal of medical education is to cultivate students to be good as well as to do well. To achieve this goal, educators should foster students to be good doctors for 99% of patients, rather than to be high performers for 1% of patients. There are two types of curriculum for medical professionalism: hidden and formative curricula. In these curricula, we doctors may be good role models for medical students. The curriculum contents and the methods for implementation that are based on accumulated experience can be embedded into education on professionalism. In addition, as suggested by Miller, how to evaluate medical professionalism based on a framework of clinical assessment must be discussed. Finally, it is suggested that the process of education on medical professionalism should be a kind of cultural movement to raise good doctors.

젓갈에서 분리한 Lactobacillus spp.로 제조한 요구르트의 이화학적 특성

이영환,나한주,이용규,신승이,김종현,Rhee, Young-Hwan,Na, Han-Ju,Lee, Yong-Kyu,Shin, Seung-Yee,Kim, Jong-Hyun 한국응용생명화학회 1997 Applied Biological Chemistry (Appl Biol Chem) Vol.43 No.1

젓갈류로 부터 Lactobacillus cases 2주와 L. pentosus 1주를 분리, 동정한 후 이들 유산균의 요구르트 제조 Starter로서의 이용 가능성을 고찰하고자, 이들 균주를 Starter로 이용하여 요구르트를 제조한 결과 요구르트 고유의 pH값은 $4.03{\sim}4.26$, 산도는 $1.049{\sim}1.217%$, 점도는 $1,772{\sim}2,232\;cps$, 그리고 생균수는 $1.4{\times}10^9{\sim}1.6{\times}10^9\;cfu/ml$였다. 요구르트의 완충능은 (요구르트 100 ml 기준) 1.0N HCl의 경우 12.50 ml 부터 14.06 ml 소모 되었고 1.0N NaOH는 9.46 ml 부터 13.06 ml 소모 되었다. 한편, 요구르트 제조시 균주 첨가 후 24시간 부터 72시간 동안 경시적으로 ${\beta}-galactosidase$ 활성도를 조사한 결과 48시간에 최고의 효소활성을 보였으며 이후에는 감소하였다. 또한 산성조건에서 2시간 동안 경시적으로 ${\beta}-galactosidase$ 활성도와 유산균 생존율을 측정한 결과 pH 3.5에서 2시간 후에는 $20{\sim}60%$ 정도 효소활성이 감소하였으며 pH 2.5와 pH 1.5에서 효소활성은 거의 없었다. 한편, 유산균의 생존율은 pH 3.5에서 2시간 후 거의 변화가 없었으나 pH 2.5와 pH 1.5에서는 각각 $1.9{\times}10^6{\sim}1.8{\times}10^8,\;1.0{\times}10^3{\sim}2.4{\times}10^5\;cfu/ml$ 수준이었다. Three strains of lactic acid bacteria were isolated from fish and shrimp pickles. Two strains were identified as Lactobacillus casei, and one strain as L. Pentosus, respectively. All three strains were used as starters in producing yogurts. The physico-chemical characteristics of yogurts were examined. The original pH, titratable acidity, visicosity and viable cell counts of the yogurts were $4.03{\sim}4.26,\;1.049{\sim}l.217%,\;1,772{\sim}2,232\;cps\;and\;1.4{\times}10^9{\sim}1.6{\times}10^9\;cfu/ml$, respectively. In evaluating buffer capacity, $12.50{\sim}14.06\;ml$ 1.0N HCl was consumed to titrate 100 ml of yogurt to pH value 2 units below the original pH value and $9.46{\sim}13.06\;ml$ of 1.0N NaOH was consumed to pH value 4 units above the original pH value. The ${\beta}-galactosidase$ activity reached maximum at 48 hrs, and reduced gradually during fermantation. After 2 hr incubation of yogurts at $37^{\circ}C$ under different pH conditions, ${\beta}-galactosidase$ activities of three strains were reduced to 50% at pH 3.5, but there were no remaining activities neither at pH 2.5 nor at pH 1.5. Under the same pH conditions the number of viable cells decreased to $1.9{\times}10^6{\sim}1.8{\times}10^8\;cfu/ml$ at pH 2.5 and $1.0{\times}10^3{\sim}2.4{\times}10^5$ at pH 1.5, respectively. However, no significant difference was found at pH 3.5.

동자개 Pseudobagrus fulvidraco (경골어강, 메기목, 동자개과)의 정자의 미세구조

이영환,Lee, Young-Hwan Korean Society of Electron Microscopy 1998 Applied microscopy Vol.28 No.1

동자개 정자는 구형의 두부와 짧은 중편 및 긴 편모를 가지고 있으며 비교적 그 구조가 단순하고 그 길이는 $76{\mu}m$이다. 대부분의 경골어류에서와 같이 첨체를 가지고 있지 않으며, $1.67{\mu}m$의 직경을 가진 핵에는 $1.0{\mu}m$ 정도로 깊이 함입된 핵와가 있고 그 속에 기부 및 말단 중심립이 들어있었다. 두 중심립은 서로 약 $160^{\circ}$의 각도로 배열되어 있으며, 말단부 중심립의 삼중미세소관과 핵 기부에 있는 축사의 이중미세소관 각각으로부터 부수체가 핵막을 항해 접선방향으로 배열되어 있었다. 약 20개 정도의 미토콘드리아가 중편 세포질에 2층 또는 3층으로 배열되어 있으며 축사와는 세포질관에 의해 분리되어 그 주위를 둘러싸고 있었다. 축사의 이중미세소관의 A소관에는 디네인 외완이 관찰되지 않았다. 한 쌍의 lateral fins는 중심미세소관의 축에 평행하게 측면으로 돌출되어 있는데 이것은 동자개 정자 꼬리의 특징으로서 다른 메기류에서는 보고되지 않았다. The spermatozoa of bagrid catfish, Pseudobagrus fulvidraco are approximately $76{\mu}m$ in length, and a relatively simple and elongated cell composed of a spherical head, a short middle piece and a tail. The ultrastructure of spermatozoa of P. fulvidraco is characterized by the following features. The acrosome is absent as in most teleost. The round nucleus measuring about $1.67{\mu}m$ in length and diameter is depressed with a deep nuclear fossa. The nuclear fossa, the length of which is about three-fifths of the nuclear diameter, contains the proximal and distal contrioles. The two centrioles are oriented approximately $160^{\circ}$ to each other. The filamentous materials give rise to satellite appendages arranged tangentially from the triplets of the distal centriole and the doublets of the anterior end of the axoneme toward the nuclear envelope. The mitochondria are not fused and their number is 20 or more. They are arranged in two or three layers and two rings within the cytoplasmic collar and surround the axoneme. They are separated from the axoneme by the cytoplasmic canal. The axoneme is of the 9+2 microtubular pattern and has inner but no outer dynein arms. The two lateral fins are in the same plane with the two central microtubules, the doublets 3 and 8, which are ultrastructural characteristics of the sperm tail unlike other siluroids lacking the lateral fins.

식물(植物) 병원성(病源性) 미생물(微生物)에 미치는 Pseudomonas fluorescens, KR-164의 영향(影響)

이영환,김영일,이재평,김용웅,김용재,이재와,Rhee, Young-Hwan,Kim, Yeong-Yil,Lee, Jae-Pyeong,Kim, Yong-Wong,Kim, Yong-Jae,Lee, Jae-Wha 한국토양비료학회 1990 한국토양비료학회지 Vol.23 No.1

The antagonistic fluorescent pseudomonas, which was isolated from continuous cropping rhizosphere of pepper and cucumber, was identified as Pseudomonas fluorescens (P.f.). For further study, transformant was derived from the isolated P.f. after spontaneous mutation to give antibiotic resistance to nalidixic acid and rifampicin as marked strain. Both P.f. and transformant strains were used for this study and the results obtained were summarized as follows. 1. One of the most effective antagonistic strain, KR164, was selected against F. solani, F. oxysporum, R. solani and this strain was identified and classified as Pseudomonas fluorescens biotype IV. 2. Transformant, KR1641, was derived from strain KR164 and both strains had the same biological and biochemical characteristics. 3, Mycelial lysis and abnormal mycelia of plant pathogenic fungi were microscopically observed after simultaneous culture of fungus and given bacterial strain. 4. The length of chinese cabbage to the autolyzed became longer with given bacterial strain in dark culture. 5. Percentage of germination, number of leaves, length of height, and length of root in chinese cabbage in pot experiment were improved by inoculation of given bacterial strain. 6. The number of given bacterial strain kept generally stable until 34 days after inoculation of itself in pot experiment. Inoculation of given bacterial strain did affect the number of plant disease fungi to be decreased but did not affect the number of other bacteria, Bacillus, in pot experiment. 고추, 오이 등의 시설원예(施設園藝) 연작토양(連作土壤)에서 토양전염성(土壤傳染性) 식물병원균(植物病院菌)에 길항력(拮抗力)을 갖는 Pseudomonas fluorescens를 분리(分離), 동정(同定)하고 이 균주(菌株)를 nalidixic acid와 rifampicin에 내성을 갖는 spontaneus multant를 유도(誘導)하여 표식균주(標識菌株)를 만들었다. 이들 표식균주(標識菌株)와 모균주(母菌株)의 생화학적 특성(特性), 병원성 사장균(絲狀菌)에 대한 길항력(拮抗力), 암소배양(暗所培養), 작물(作物) pot 실험(實驗) 결과(結果)를 요약(要約)하면 다음과 같다. 1. 고추, 오이 등의 시설원예(施設園藝) 연작지(連作地) 토양(土壤)에서 형광성(螢光性) Pseudomonas를 분리(分離)하여 Rhizoctonia solani, Fusrium oxysporum, Fusarium solani에 생육(生育) 저해력(沮害力)이 우수한 KR-164를 선발(選拔)하고 이들의 분류학적(分類學的) 성질(性質)을 검토(檢討)한 결과(結果) Pseudomonas fluorescens biotype IV로 분류(分類), 동정(同定)하였다. 2. KR-164에서 표식균주(標識菌株)인 KR-1641 변이주(變異株)를 유도하였고, 이들 표식균주(標識菌株)와 모균주(母菌株)의 생화학적(生化學的) 성질(性質)은 동일(同一)하였다. 3. 분리균주(分離菌株)와 식물(植物) 병원성 사장균(絲狀菌)을 대치배양(對置培養)하여 검경한 결과(結果) 여러 형태(形態)의 균사이장(異狀)이 관찰(觀察)되었다. 4. 분리균주(分離菌株)를 배추 암소배양(暗所培養)에 처리(處理)한 결과(結果) 무처리구(無處理區)에 비해 생육기간(生育其間)이 현저하게 연장(延長) 되었다. 5. 분리균주(分離菌株)의 접종(接種)이 대조구(對照區)와 사장균(絲狀菌) 접종구(接種區)에 비해 배추의 발아율(發芽率) 및 엽수, 초장, 근장 등의 생육(生育)을 향상(向上)시켰다. 6. 토양(土壤)에 접종(接種)된 표식균주(標識菌株)는 접종(接種) 35일까지 안정(安定)하였으나 병원성 사장균(絲狀菌)은 현저하게 감소(減少)하였고, 표식균주(標識菌株)는 근권(根圈) 유용미생물(有用微生物)의 생육(生育)에 뚜렷한 영향(影響)을 미치지 않았다.

Friedrich von Hayek 에 있어 개인주의 사상과 시장질서

이영환,소병희 ( Young Hwan Lee,Byung Hee Soh ) 한국경제학회 1994 經濟學硏究 Vol.41 No.3