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이정운,이기효,문옥륜,Lee, Jung-Un,Lee, Ki-Hyo,Moon, Ok-Ryun 대한예방의학회 1991 예방의학회지 Vol.24 No.3
The purpose of this paper is to identify factors affecting the optimum mix of required inputs and other relevant factors which account for the variation in physician's productivity in general hospitals, and to find out their implications for the efficient health planning and management. An extended version of Cobb-Douglas production function and cross sectional data of one day patient census from all general hospitals in Korea in 1988 were used in the analysis. Main results of the analysis and their implications could be summarized as follows : (1) The production function for physician's inpatient service shows the evidence of economies of scale, but the production function for physician's outpatient and adjusted-patient service, which combines both out- and in-patient service, shows that of dis-economies of scale. (2) The physician's role for production for all service is smaller than auxiliary personnel's, which imply that more intensive utilization of nurses, nursing aides and other auxiliary personnel is desirable for improving general hospital productivity (3) In case of physician's inpatient and adjusted-patient service, nurses' role is greater than nursing aides'. Therefore, more extensive utilization of nurses is recommended for the efficient operation of general hospitals. (4) The factor of hospital beds plays the leading role among required inputs in the production for physician's in- and adjusted-patient service. (5) The physician's productivity of general hospitals in rural area is lower than that in urban area. And the productivity of teaching hospitals is lower than that of the other hospitals. Further analysis was made in physician production function based upon the size of hospitals, namely those hospitals below 250 beds and those above. Explained variances by the factor of hospital beds was significantly increased in the case of those hospitals above 250. A more detailed and thorough investigation is needed for verifying factors influencing physician's productivity in general hospitals in Korea.
한국형발사체 3단 과산화수소 추력기시스템 제어장치 아날로그 데이터 취득 스케줄링 변경을 통한 노이즈 측정오류 개선
이상현(Sang-Hyun Lee),송우근(Woo-Keun Song),오현명(Hyun-Myung Oh),이정운(Jung-Un Lee),이종철(Jong-Cheol Lee),박상준(Sang-Joon Park),이상빈(Sang-Bin Lee),이희중(Hee-Joong Lee),오상관(Sang-Gwan Oh),민병주(Byeong-Joo Min) 한국항공우주학회 2020 한국항공우주학회 학술발표회 논문집 Vol.2020 No.11
분체공학,유동층,고분자,재료(무기, 유기) : 졸-겔법으로 제조된 복합 알루미나 미분체의 첨가제에 의한 구조적 특성 비교
이정운 ( Jung Woon Lee ),윤호성 ( Ho Sung Yoon ),채의석 ( U Suk Chae ),박한진 ( Han Jin Park ),황운연 ( Un Yeon Hwang ),박형상 ( Hyung Sang Park ),박달령 ( Dal Ryung Park ),유승준 ( Seung Joon Yoo ) 한국화학공학회 2005 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.43 No.4
황운연(Un Yeon Hwang),이승구(Seung Gu Lee),최진훈(Jin Hoon Choi),이정운(Jung Woon Lee),박형상(Hyung Sang Park),유승준(Seung Joon Yoo),윤호성(Ho Sung Yoon),김용렬(Young Ryul Kim) 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.5
In this study, spherical pre-mullite powders of three composition were prepared by partial hydrolysis on the TEOS and mixed solvent method. From the FC-IR analysis of pre-mullite powders, the structure could be interpreted that SiO₂ tetrahedron and AlO_6 octahedron are bonded randomly by sharing oxygen atom. By the DTA analysis, the amount increase of Al₂O₃composition in the pre-mullite caused the shift of first exotherm to low temperature. As a result of XRD analysis on the pre-mullite and leached sample calcined from 1,200 ℃ to 1,600 ℃, only mullite phase was created in the range from 70.5 wt% to 74.0 wt% alumina, which was identical with the Aksay`s range. The first exotherm at about 990 ℃ during the calcination of pre-mullite has been attributed to the formation of Al-O-Si spinet due to the liberation of amorphous silica. By means of the leaching experiment on the silica which coexisted with the spinet phase and the mullitization of leached sample, the amorphous silica liberated at about 990℃ was very essential for the mullitization. Insufficient or lack of amorphous silica can cause the formation of a-alumina with the O-Mullite by the calcination at about 1,400℃.
졸 - 겔법에 의한 γ-Al2O3 입자 제조시 수반된 해교반응에 관한 연구
유승준,이정운,황운연,윤호성,박형상( Seung Joon Yoo,Jung Woon Lee,Un Yeon Hwang,Ho Sung Yoon,Hyung Sang Park ) 한국화학공학회 1998 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.36 No.5
In the previous study[1], we showee that the, microstructure of γ-AlO(OH) andγ-Al₂O₃, particles was affected by aging stage in tate γ-AlO(OH) sol preparation process. We investigated the effects of peptization as a continuous process after aging in γ-AlO(OH) sol preparation process on characterization of γ-Al₂O₃ particles in this study. From the results, we found that there was no crystallinity and microstructure changes of γ-Al₂O₃ particles as well as γ-AlO(OH) particles according to peptization. Rut there was a decrease of average pore diameter in γ-AlO(OH) particles at the beginning of the peptization. It shows that the adsorbed H₂O molecules on agglomerated γ-AlO(OH) particles were replaced by H₃O^+ of added peptization agent and then γ-AlO(OH) particles were repulsed against each other. As the result, the macropores within γ-AlO(OH) particles disappeared. Here, the peptization phenomenon occurred since agglomerated particles binded hydrogen bands and olation bonds have been broken their bonds by the added H₃O^+, there was happened to be peptization phenomenon. In summary, we concluded that microstructure of γ-Al₂O₃particles was controlled by aging stage in sol preparation process and peptization was the process of finely suspended γ-AlO(OH) sol preparation
분체공학 , 유동층 , 재료 ( 무기 , 유기 , 고분자 ) : 혼합용매법에 의한 구형 TiO2-SiO2 미분체의 제조 및 이소프로판올 분해 특성에 관한 연구
황운연(Un Yeon Hwang),서진석(Jin Seok Seo),이정운(Jung Woon Lee),최진훈(Jin Hoon Choi),박형상(Hyung Sang Park),김용렬(Yong Ryul Kim),유승준(Seung Joon Yoo),윤호성(Ho Sung Yoon) 한국화학공학회 2001 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.39 No.1
The physical properties which affect on the activity of photocatalysts are active site number and surface area, etc. Recently, to control these properties, `Sol-Gel` methods are used to synthesize photocatalysts. In this study, we synthesized spherical TiO₂-SiO₂ photocatalysts by mixed solvent method, and analyzed the changes in morphology of the catalysts with synthesis conditions by SEM and the changes in physical properties of the particles and the variation of the crystal structure with Ti concentration and calcination temperature by TGA, BET, FT-IR and XRD. Then we investigated the effects of the physical properties and [Ti]/[Si] ratio on phobocatalytic degradation of iso-propanol. The particle size was demeaned with increasing HPC concentration and decreasing Ti concentration. The surface area of the catalysts was decreased by increasing Ti concentration and calcination temperature. As Ti concentration was increased, Ti-O-Si bond number was increased, and by calcination, the number was increased until 400 ℃, then decreased with increasing calcination temperature. The extent of photodegradation of isopropanol was higher as photocatalysts have more Ti, but the turnover frequency of the Ti was higher as the catalysts have less Ti. Because (Ti^(3+)-O^-) number and the surface area of the photocatalysts are decreased by increasing calcination temperature, the photodegradation of organic material is decreased.
황운연(Un Yeon Hwang),이승구(Seung Gu Lee),이정운(Jung Woon Lee),박형상(Hyung Sang Park),유승준(Seung Joon Yoo),윤호성(Ho Sung Yoon),김용렬(Yong Ryul Kim) 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.6
In this study, transparent yttria stabilized zirconia(YSZ)-gel and ZrO₂-gel were prepared by the alkoxide-acetylacetone chelation method of Zirconium-n-propoxide. Transparent ZrO₂-gel.could be prepared through 1 hour reaction and three hours aging in the condition of 0.4 S [Acac]/[Zr-n-p]=R S 0.6. The gelation time was increased with increasing the molar ratio R. The molar ratio R had an important effect upon the inner structures of gel and the crystallization process. YSZ-gel of the four kinds of composition was prepared in the condition of [Acac]/[Zr-n-p] = 0.5. Crystallization behavior of these gels depended upon the concentration of Y₂O₃. All samples dried at 60℃ for 24 hr were amorphous by XRD analysis, and the first crystalline phase obtained beyond 450℃ from the dried samples was the cubic one. The 2.SYSZ and 4.5YSZ samples passed through the cubic phase were transformed into the tetragonal phase was at arround 600℃ and 1,000℃, respectively. For 6.5YSZ and 8.5YSZ, cubic structure was developed continuously without transformation of crystal structure by 1,000 ℃. An exothermic peak around 450 ℃ on DTA analysis associated with the crystallization to cubic phase and the formation of ZrOCO₃(lattice), H₂O, and CO₂. The third exotherm (about 850 ℃) during the calcination was attributed to the liberation of CO₃^(2-) .