새 정부에 바란다 - '신성장동력을 중심으로'

박철우,Park, Cheol-Woo 한국과학기술단체총연합회 2013 과학과 기술 Vol.526 No.-

다양한 온도조건과 flux 첨가량에 따른 단결정 성장용 YAG : Er³⁺ 분말 제조

박철우,강석현,박재화,김현미,최재상,강효상,심광보,Park, Cheol Woo,Kang, Suk Hyun,Park, Jae Hwa,Kim, Hyun Mi,Choi, Jae Sang,Kang, Hyo Sang,Shim, Kwang Bo 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.4

본 연구에서는 고상법 및 flux를 이용하여 $Y_3Al_5O_{12}:Er^{3+}\;(YAG:Er^{3+})$ 분말을 저온에서 성공적으로 합성하였다. 분말의 합성 여부와 분말 하소 시 온도에 따른 결정성을 분석하기 위하여 X-ray diffraction(XRD)를 측정하였다. 순수한 YAG는 일반적인 고상법으로 합성할 경우, $1400^{\circ}C$에서 12시간 동안 하소하여 순수한 YAG 상을 얻을 수 있었고, 반면에 $BaF_2$를 첨가한 결과는 상대적으로 낮은 온도($1000^{\circ}C$)에서 합성되었다. 즉, 합성온도를 약 $400^{\circ}C$ 가량 낮출 수 있는 것으로 나타났다. 또한, $BaF_2$의 최적의 농도를 찾아 첨가 후, 열처리 온도에 따라 $BaF_2$로 인한 입자의 형태 및 크기를 조사하였으며 그에 따른 발광강도에 대하여 논의하였다. In this study, using solid-state and flux, $Y_3Al_5O_{12}:Er^{3+}\;(YAG:Er^{3+})$ powders were successfully synthesized at low temperatures. To analyze the crystallinity of powders according to the synthesis or non-synthesis of powders and powder calcination temperatures, X-ray diffraction (XRD) was measured. In the case of pure YAG, when YAG was analyzed using the general solid-phase method, it was calcined for 12 hours at $1400^{\circ}C$ and pure YAG phase could be obtained. But when $BaF_2$ was added to YAG, YAG was synthesized at lower temperature (1000^{\circ}C$). It was thus found that the synthesis temperature could be lowered by about $400^{\circ}C$. Also, when BaF2 with an optimal concentration was added to $YAG:Er^{3+}$, the particle shape and size according to synthesis temperatures were surveyed, and corresponding luminous intensity was discussed.

하악 편측 유리단 가철성 국소의치의 설계에 따른 광탄성 응력 분석

박철우,계기성,Park, Cheol-Woo,Kay, Kee-Sung 대한치과보철학회 2009 대한치과보철학회지 Vol.47 No.2

연구목적: 하악 우측 제1, 2 대구치가 결손된 Kennedy 분류 II급 증례에서 임상적으로 적용할 수 있는 편측 유리단 가철성 국소의치의 종류에 따른 응력 분포 양상을 비교하는 것이다. 연구 재료 및 방법: Kennedy 분류 II급 증례의 광탄성 모형에서 클라스프를 이용한 국소의치, 코너스 치관을 이용한 국소의치, 완압형 어태치먼트를 이용한 국소의치, 탄성 레진을 이용한 국소의치를 편측성으로 제작하였다. 응력 동결로에서 응력 주기에 맞춰 각 국소의치의 제1 대구치 중심와에 6 kg의 수직하중을 가하면서 응력을 동결하였다. 광탄성 모형을 절단하여 만든 시편을 광탄성 실험 장치로 광탄성 등색선의 흑백 무늬를 관찰하고 디지털 카메라로 촬영하였다. 촬영된 사진에서 8개의 측정점을 정하여 육안으로 무늬차수를 계측하고 비교하였다. 결과: 각 절단 시편의 최대 무늬차수와 하중점 직하방의 잔존 치조제에 발생한 무늬차수는 탄성 레진을 이용한 국소의치, 클라스프를 이용한 국소의치, 완압형 어태치먼트를 이용한 국소의치, 코너스 치관을 이용한 국소의치 순으로 높게 관찰되었다. 제2 소구치 치근단에 발생한 무늬차수는 클라스프를 이용한 국소의치, 탄성 레진을 이용한 국소의치, 코너스 치관을 이용한 국소의치, 완압형 어태치먼트를 이용한 국소의치 순으로 높게 관찰되었다. 결론: 코너스 치관을 이용한 국소의치가 수직하중시 지대치 주위 치조골과 잔존 치조제에 대하여 응력을 가장 균형있게 분산시켰고, 탄성 레진을 이용한 국소의치는 지대치보다 잔존 치조제의 상태가 더 양호한 경우에 적용 가능할 것이다. Statement of problem: There are common clinical cases in which the mandibular first and second molars are missing unilaterally. Purpose: This study was designed to compare and evaluate the magnitude and distribution of stress produced by four kinds of mandibular unilateral free-end removable partial dentures that could be applied clinically in Kennedy class II cases. Material and methods: Four unilateral free-end removable partial dentures using clasp, Konus crown, resilient attachment, and flexible resin were fabricated on the photoelastic models of the Kennedy class II cases. The vertical load of 6㎏ was applied on the central fossa of the first molar of every removable partial denture in the stress freezing furnace and the photoelastic models were frozen according to the stress freezing cycle. After these models were sliced mesio-distally to a thickness of 6mm, the photoelastic isochromatic white and black lines of the sliced specimens were examined with the transparent photoelastic experiment device and photographs were taken with a digital camera. The fringe order numbers at eight measuring points in the photograph were measured with the naked eye. Results: The maximum fringe order number of each sliced specimen and the fringe order number at the residual ridge just below the loading point were in the decreasing order of the unilateral removable partial dentures using flexible resin followed by clasp, resilient attachment, and Konus crown. The fringe order number at the root apex of the second premolar was in the decreasing order of the unilateral removable partial dentures using clasp followed by flexible resin, Konus crown, and resilient attachment. Conclusion: The removable partial denture using Konus crown showed the most equalized stress distribution to the supporting alveolar bone of abutment teeth and residual ridge under the vertical loads. The removable partial denture using flexible resin can be applied to the case that has a better state of residual ridge than abutment teeth.

국내 무연탄회의 화학조성 및 용융특성에 관한 연구

박철우,이시훈,손응권,Park, Cheol-Woo,Lee, See-Hoon,Shon, Eung-Kwon 한국분석과학회 1992 분석과학 Vol.5 No.4

국내의 23개 무연탄을 대상으로 석탄회의 화학분석 및 용융특성분석을 수행하여 석탄회의 화학조성과 용융온도와의 상관성을 고찰하였다. 또한 이들 무연탄을 미분탄 연소의 연료로 사용시 야기될 수 있는 slagging, fouling성을 예측하여 보았다. 국내 무연탄회는 대부분 $SiO_2$와 $Al_2O_3$를 80% 이상 함유하고 있는 반면 1% 이하의 적은 양의 $Na_2O$를 함유하고 있으며, 또한 비교적 높은 용융온도를 갖는다. 따라서 이 무연탄들을 미분탄 연소의 연료로 사용시 slagging 및 fouling 발생 가능성은 낮을 것으로 예측되었다. 국내 무연탄회의 용융특성은 base/acid ratio와 비교적 높은 상관성을 갖는 것으로 나타났다. Chemical composition and fusibility of coal ash were measured for 23 Korean anthracite coals. The relationship between chemical properties and fusion temperature of coal ash was investigated. The slagging and fouling in firing the pulverized coal for boiler was assessed for the coal samples. It was found that most ashes contained more than 80% of $SiO_2$ and $Al_2O_3$ whereas less than 1% of $Na_2O$. And also fusion temperature of ashes occured relatively higher for Korean coals. Therefore it can be predictable that the slagging and fouling formation has a little problem in a pulverized coal firing system. A base/acid ratio did show a good correlation with fusion temperature for these coal ashes.

하악 제1대구치 단일 수복을 위한 발치 즉시 임플란트의 임상증례

박철우,Park, Cheol-Woo 대한심미치과학회 2021 Journal of the Korean Academy of Esthetic Dentistr Vol.30 No.1

Immediate implantation is widely applied as it is recognized as a useful implant treatment in dental clinic due to its various advantages as well as being able to shorten the treatment period. Immediate implant treatment was performed on 5 patients who needed extraction of the mandibular first molar for various reasons, shortening the overall treatment period, and obtaining satisfactory results. Immediate implantation after extraction is a high-level treatment that requires proper initial fixation at the exact location of the extraction socket and the surrounding soft tissues, but is considered to be a clinically very useful prosthetic restoration method 발치 즉시 임플란트는 치료 기간을 단축할 수 있을 뿐만 아니라 여러 가지 장점으로 인해서 치과임상에서 유용한 임플란트 치료법으로 인식되면서 널리 적용되고 있다. 다양한 이유로 인해서 하악 제1대구치의 발치가 필요한 5명의 환자에게 발치 즉시 임플란트 치료를 진행하여 전체 치료 기간을 단축하면서 만족스러운 결과를 얻었다. 발치 즉시 임플란트는 발치와 내 정확한 위치에 적절한 초기고정을 얻어야 하고 주위 연조직도 개선해야 하는 고난도 치료법이지만 임상적으로 매우 유용한 보철 수복 방법이라고 판단된다.

AlN 단결정의 품질평가를 위한 molten KOH/NaOH eutectic alloy의 화학적 습식에칭

박철우,박재화,홍윤표,오동근,최봉근,이성국,심광보,Park, Cheol Woo,Park, Jae Hwa,Hong, Yoon Pyo,Oh, Dong Keun,Choi, Bong Geun,Lee, Seong Kuk,Shim, Kwang Bo 한국결정성장학회 2014 한국결정성장학회지 Vol.24 No.6

본 연구에서는 상용화되는 AlN 웨이퍼(wafer)를 이용하여 molten KOH/NaOH 화학적 습식 에칭(Wet Chemical Etching)에 따른 표면변화 특성 및 최적의 에칭 조건을 조사하였다. AlN 웨이퍼를 $350^{\circ}C$에서 5분간 에칭 시 Al-face, N-face는 서로 다른 관찰되었다. 특히, Al-face는 에치핏의 형상을 파악하여 결함특성을 관찰하였고, 이로부터 결함 밀도를 계산하여 $2{\times}10^6/cm^2{\sim}10^{10}/cm^2$의 결과를 얻었다. N-face의 경우 육각 뿔(hexagonal pyramids) 형태의 격자결함이 형성되었다. 또한 AlN 웨이퍼의 성장 시 배향을 관찰하기 위해 XRD(X-Ray Diffraction, Rigaku, JAPAN)를 이용하여 분석한 결과 육방정 AlN의 C축 방향에 해당되는 (0002) 및 (0004) 면으로 배향된 상태임을 알 수 있었고, DC-XRD(Double Crystal X-ray Diffraction, bruker, Germany)를 이용하여 rocking curve의 위치에 따라 곡률 반경을 측정했을 때 1.6~17 m의 곡률을 가지고 있는 것으로 나타났다. We investigated the optimal etching conditions and properties of the surface change due to molten KOH/NaOH chemical wet etching using an AlN wafer which has been put to practical use in the present study. Results were observed using a scanning electron microscope after 5 minutes etching at $350^{\circ}C$, was found to have a surface form of the respective other Al-face, the N-face. In particular, etch-pit in the form of a hexagon, which is observed in the Al-face appeared, It was calculated at $2{\times}10^6/cm^2{\sim}10^{10}/cm^2$ dislocation density. In the case of N-face, lattice defects in the form of the hexagonal pyramids is formed. It was discovered that in order to observe the orientation of the wafer, which corresponds to the C-axis direction of the resulting hexagonal AlN which was analyzed using XRD (0002) and is a state of being oriented in the (0004) plane. The Radius of curvature of AlN wafer was 1.6~17 m measured by DC-XRD rocking curve position.

생태계교란 생물 미국가재(Procambarus clarkii)의 국내 서식과 분포 연구

박철우,김종욱,조윤정,김재구,이민지,김수환,Park, Cheol Woo,Kim, Jong Wook,Cho, Yun Jeong,Kim, Jae Goo,Lee, Min Ji,Kim, Su Hwan 한국하천호수학회 2020 생태와 환경 Vol.53 No.4

미국가재는 멕시코 북동부 및 미국 중남부가 원산지로, 전 세계에 유입되어 서식처 파괴와 토착종과의 경쟁 등 많은 문제를 야기하고 있다. 본 조사에서 영산강 6개 지점, 만경강 5개 지점, 섬진강 2개 지점 금강 1개 지점에서 확인되었으며, 주요 수계에서 정착 서식하는 것으로 나타났다. 완주군 서봉리와 함평군 모산리는 20개체 이상이 확인되어 비교적 큰 개체군을 형성하고 있을 것으로 추정된다. 높은 이동성과 환경적응력으로 보아 확인된 지점에서 타수계로의 유입 가능성이 매우 높을 것으로 생각되며, 이에 지속적인 확산 현황 파악과 생태계 피해 예방을 위한 지속적 제거 노력이 필요하다. The red swamp crawfish (Procambarus clarkii) is native to northeastern Mexico and south-central United States. But the species has been introduced to other parts of the world, and cause ecological problems including habitat destruction and competition with indigenous species. In this study, we identified the distribution of P. clarkii in the freshwater system in Korea. P. clarkii were collected in the field sampling and it is assumed that they have settled in major domestic water systems of Korea including six points in the Yeongsangang River, five points in the Mangyeonggang River, two points in the Seomjingang River, and one point in the Geumgang River. In particular, more than 20 individuals were found in Seobongri, Wanjugun and Mosanri, Hampyeonggun, which are believed to form a relatively large population. Considering high mobility and environmental adaptability of the species, the possibility of their dispersal to other water systems is very high. Therefore, continuous monitoring and assessment of their distribution and potential spread are required and effective management to remove them policy is needed to prevent damage in the Korean ecosystem.

상악 전치부 즉시하중 임플란트의 식립 깊이에 따른 삼차원 유한요소 분석

박철우,김성훈,여인성,윤형인,한중석,Park, Cheol-Woo,Kim, Sung-Hun,Yeo, In-Sung,Yoon, Hyung-In,Han, Jung-Suk 대한치과보철학회 2018 대한치과보철학회지 Vol.56 No.2

Purpose: The purpose of this study was to investigate the effects of the insertion depth of an immediately loaded implant on the stress distribution of the surrounding bone and the micromovement of the implant using the three-dimensional finite element analysis. Materials and methods: A total of five bone models were constructed such that the implant platform was positioned at the levels of 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, and 1.00 mm depth from the crest of the cortical bone. A frictional coefficient of 0.3 and the insertion torque of 35 Ncm were simulated on the interface between the implant and surrounding bone. A static load of 178 N was applied to the provisional prosthesis with a vertical load in the axial direction and an oblique load at $30^{\circ}$ with respect to the central axis of the implant, then a finite element analysis was performed. Results: The implant insertion depth significantly affected the stress distribution on the surrounding bone. The largest micromovement value of the implant was $39.34{\mu}m$. The oblique load contributed significantly to the stress distribution and micromovement in comparison to the vertical load. Conclusion: Increasing the implant insertion depth was advantageous in dispersing the concentrated stress in the cortical bone and did not significantly affect the micromovement associated with early osseointegration failure. 목적: 삼차원 유한요소분석을 이용하여 상악 전치부 즉시하중 임플란트의 식립 깊이가 주위 골의 응력 분포와 임플란트의 미세움직임에 미치는 영향을 알아보고자 하였다. 재료 및 방법: 임플란트 상단이 치조정 피질골 상연을 기준으로 0.00 mm, 0.25 mm, 0.50 mm, 0.75 mm, 1.00 mm 깊게 위치되도록 총 5개 골모형을 제작하였다. 고정체와 주위 골 계면에 마찰접촉과 35 Ncm의 식립 토크를 재현하였다. 임시 보철물에 178 N의 정하중을 고정체의 중심축에 대하여 축방향의 수직하중과 $30^{\circ}$의 경사하중으로 가하고 유한요소 분석을 시행하였다. 결과: 임플란트의 식립 깊이가 주위 골의 응력 분포에 상당한 영향을 주었다. 임플란트의 가장 큰 미세움직임이 $39.34{\mu}m$로 나타났다. 경사하중이 수직하중에 비해서 응력 분포와 미세움직임의 변화에 크게 기여하였다. 결론: 임플란트 식립 깊이의 증가는 피질골에 집중된 응력을 분산시키는데 유리하였으며, 초기 골유착 실패와 관련이 있는 미세움직임에는 크게 영향을 주지 않았다.

방사선치료 암 환자의 대체요법 경험실태 조사연구

박철우,박태진,Park Cheol Woo,Park Tae-Jin 대한방사선치료학회 2001 大韓放射線治療技術學會誌 Vol.13 No.1

Although it is presumed that cancer patients take various alternative therapies, the present status is not well recognized. The purpose of this study is to survey alternative therapies used by cancer patients receiving radiation therapy and then, find associated factors of taking alternative therapies. The study subjects were composed of those who receiving radiation therapy in the department of radiation oncology in 5 hospitals located at Extended Busan city and who were on follow-up after medical cure. They were 394 male and female patients over 20 years old. The mean age of the subjects was 53.2 years old and the age ranged from 23 to 83 years old. 188 patients($47.7\%$) used alternative therapies. Total 68 different kinds of alterative therapies were used, average 7.3 kinds per patient were experienced, and average total cost expenditure was 2,830,000 won. Among the alternative therapies, black bean($38.8\%$) was the most commonly used and brown rice($38.3\%$), ganoderm lucidum($37.8\%$), elm tree($33.5\%$), and phellinus linteus($30.8\%$) were followed in order of frequency. However in considering the time, cost and effort spent, phellinus linteus was the first. In terms of cost, phellinus linteus was the highest with average expenditure of 2,740,000 won. Among the motivation of using alternative therapies, expecting auxiliary help for the hospital therapy was the highest ($31.4\%$). About half of users($56.9\%$) of alternative therapies were recommended by their relatives to use alternative therapies. In comparing the characteristics of experienced and unexperienced groups, alternative therapy was experienced significantly more in patients of younger age(p=0.001), in patient of higher educational level(p=0.001), and in patients of higher income(p=0.030) The proportion of using alternative therapies was significantly higher in the group treated with chemotherapy(p=0.005), and in the patients who did not satisfy with radiation therapy(p=0.001). The frequency of drinking was significantly higher tendency in the inexperienced group(p=0.046), There was no significant difference in marital status, job, religion, other disease, surgical operation of the cancer and smoking staus between the two groups. Among the unexperienced group, $34.0\%$ of the patients did not take the alternative therapies because they did not have know]edge for the alternatives, and $22.3\%$ worried about negative effects on hospital-based therapy $58.7\%$ of them were willing to take the alternative therapies if the effects and safety were proven by the government or research institutes. $21.9\%$ of the patients wanted to take the alternatives if they were affordable. $72.3\%$ of the patients was willing to take them if their families recommend, but $27.2\%$ responded they would not take them in any situation. Conclusively, various kinds of alternative therapies which were not proved medically were exposed to patients, In these circumstances, it is required to investigate, study and evaluate the medical effects and safety of the alternative therapies.

대기경계층 내에 놓인 실린더의 자유단 형상변화가 후류유동에 미치는 영향에 관한 연구

박철우,이상준,Park, Cheol-Woo,Lee, Sang-Joon 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.1

The flow structure around the free end of a finite circular cylinder (FC) embedded in an atmospheric boundary layer (ABL) over open terrain was investigated experimentally with varying the free end shape. The experiments were carried out in a closed-return type subsonic wind tunnel. A finite cylinder with an aspect ratio (L/D) of 6 was mounted vertically on a long flat plate. The Reynolds number based on the cylinder diameter is about Re=7,500. The velocity fields near the FC free end were measured using the single-frame double-exposure PIV method. As a result, for the FC with a right-angled free end, there is a peculiar vortical structure, showing counter-rotating twin vortices near the FC free end. It is caused by the interaction between the entrained irrotational fluids from both sides of FC and the downwash flow from the FC free-end.