조절형 인공수정체에서 전방깊이의 측정을 통한 조절력의 평가

류현욱,정성근.Hyun Wook Ryu. M.D.. Sung Kun Chung. M.D. 대한안과학회 2006 대한안과학회지 Vol.47 No.5

Purpose: To investigate the accommodating potency of the 1CU accommodative posterior chamber intraocular lens (PC IOL), according to pilocarpine-induced ciliary muscle contraction, near visual acuity, and distance-corrected near visual acuity after implantation of the IOL. Methods: In a prospective study, 9 eyes of 7 patients (mean age 48±14.9 years [range 23 to 71 years]) had phacoemulsification and PC IOL (1CU?, Humanoptics). Distance refraction, distance visual acuity (VA), distance-corrected VA (DCVA), near visual acuity (NVA), and distance-corrected near visual acuity (DCNVA) were determined at 2 week, 1, 2, 6, and 12 months after surgery. Anterior chamber depth (ACD) was measured 3 times with the Orbscan? (Orbtek, U.S.A.), and averaged. Then ACD was repeatedly measured within 90 minutes after administration of pilocarpine 2% eyedrops 3 times at 10 minutes interval. Results: At 2 weeks, 1, 2, 6 and 12 months after surgery, the mean DCNVA was 0.55±0.23, 0.37±0.14, 0.40±0.22, 0.51±0.20, and 0.56±0.20, respectively. The mean ACD decrease (mm) was 0.57±0.77, 0.91±0.69, 0.17±0.45, 0.35±0.40 and 0.59±0.31, respectively, using Orbscan? after pilocarpine 2% eyedrops. There was statistically significant correlation between the pilocarpine-induced IOL movement and DCNVA (r=0.439, P=0.012). Conclusions: 1CU accommodative PC IOL provided relatively good DCNVA and accommodating potency for up to 1 year. It is necessary to investigate accommodative change for a longer time period.

Sol-Precipitation법으로 제조된 WO₃ 나노분말을 이용한 후막 센서의 NO₂ 감지 특성

류현욱,박경희,김인천,홍광준,박진성,Ryu, Hyun-Wook,Park, Kyung-Hee,Kim, In-Chun,Hong, Kwang-Joon,Park, Jin-Seong 한국재료학회 2002 한국재료학회지 Vol.12 No.12

Nanosized $WO_3$ powders were synthesized by the sol-precipitation process using $WCl_{6}$ as the starting material, ethanol as a solvent and $NH_4$OH solution as a precipitant, followed by a washing-drying treatment and calcination. The effects on the powder crystallinity and microstructure of calcination temperature were investigated with XRD and FE-SEM. The $WO_3$ powders calcined at $500^{\circ}C$ and $700^{\circ}C$ showed good crystallinity and their mean particle size was 30nm and 70nm, respectively. These powders were used for the preparation of pastes which were printed as thick films on alumina substrates with comb-type Pt electrodes. The particle size strongly influenced the $NO_2$ gas sensing property of the thick films. A significant reduction in the $NO_2$ sensitivity was observed for the film prepared from larger particle size, having thus a larger grain size. For the film having a smaller grain size, on the other hand, the higher $NO_2$ sensitivity was observed and the sensitivity increased with $NO_2$ concentration.

플라즈마 가스와 RF 파워에 따른 NiO 박막의 우선배향성 및 표면형상 변화

류현욱,최광표,노효섭,박용주,권용,박진성,Ryu Hyun-Wook,Choi Gwang-Ryo,Noh Whyo-Sup,Park Yong-Ju,Kwon Yong,Park Jin-Seong 한국재료학회 2004 한국재료학회지 Vol.14 No.2

Nickel oxide (NiO) thin films were deposited on Si(100) substrates at room temperature by RF magnetron sputtering from a NiO target. The effects of plasma gas and RF power on the crystallographic orientation and surface morphology of the NiO films were investigated. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) were employed to characterize the deposited film. It was found that the type of plasma gases affected the crystallographic orientation, deposition rate, surface morphology, and crystallinity of NiO films. Highly crystalline NiO films with (100) orientation were obtained when it was deposited under Ar atmosphere. On the other hand, (l11)-oriented NiO films with poor crystallinity were deposited in $O_2$. Also, the increase in RF power resulted in not only higher deposition rate, larger grain size, and rougher surface but also higher crystallinity of NiO films.

도포-열분해법을 이용한 비대칭 세라믹 분리막 제조

류현욱,김병훈,Ryu, Hyun-Wook,Kim, Byung-Hoon 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.12

입도가 다른 두 가지 고순도 ${\alpha}-Al_2O_3$ 분말을 이용하여 slip casting법과 담금코팅(dip coating)법으로 다공질 알루미나 지지체와 중간층을 각각 제조하였으며, 그 위에 분리막인 산화티탄($Tio_2$)층을 Ti-naphthenate용액으로 screen printing한 후 열분해시켜 형성시킴으로써, 3층 구조의 비대칭성 세라믹 분리막을 제조하였다. 알루미나 지지체의 곡강도, 기공율 및 평균 기공크기는 각각 231 Kg/$cm^2$, 30.26%, 0.19 ${mu}m$였으며, 중간층은 두께가 약 30 ${mu}m$, 평균 기공크기가 0.063 ${mu}m$였다. 또한 최상층 $Tio_2$ 분리막은 그 두께가 약 0.5 ${mu}m$였으며 평균 약 20 nm 정도의 미세 기공들이 매우 균일하게 형성되어 있었다. The fabrication of a three-layered asymmetric ceramic membrane was performed by slip casting of the porous alumina support and dip coating of the alumina intermediate layer using high purity ${\alpha}-Al_2O_3$ powders that have different particle size, followed by screen printing-pyrolysis of the $Tio_2$ layer as an ultrafilteration membrane using Ti-naphthenate solution. The bending strength, porosity and mean pore size of the alumina support were 231 kg/$cm^2$s, 30.26% and 0.19 ${mu}m$, respectively. The thickness of the intermediate layer was 30 ${mu}m$ and the mean pore size of that was 0.063 ${mu}m$. Also, the top layer was 0.5 ${mu}m$ thick and micropores with about 20 nm size were formed uniformly.

하악골 결손부의 치조골 신장술을 이용한 임플란트 식립 증례보고

류현욱,Ryu, Hyun-Wook 대한악안면성형재건외과학회 2009 Maxillofacial Plastic Reconstructive Surgery Vol.31 No.4

Objective : This is to report the effectiveness of intraoral distraction osteogenesis, iliac bone graft for alveolar augmentation in the extremely atrophied alveolar defects after infected allobone grafted area. Subjects and Methods : Anterior segmental osteotomy was performed and the trans-oral alveolar distractors (Martin, Germany) were applied in patient with the severe acquired anterior mandibular and mandibular defect after ameloblastoma enucleation. Iliac bone grafts were performed in defect sites and distraction osteogenesis were treated. After latent period for 1 week, the osteomized alveolar segments were distracted by 0.75 mm a day (0.25 mm/1 turn) for 10 days The consolidation period was about 12 weeks. Thereafter, 2 titanium threaded implants were simultaneously installed with removal of distractor. For oral rehabilitiation, The implants were installed in maxilla, mandible. It was tested with clinically and radiographically. Results : Amounts of acquired alveolar bone were 10 mm with the increased width of the ridge crests and soft tissue expansion. Dental implants installated on the augmented alveolar ridges in 12 weeks after distraction were confirmed as in good osseointegration and in good function without any complications. Conclusion : Intraoral distraction osteogenesis can be a good option for alveolar ridge augmentation of the severely atrophied ridges and soft-tissue defects.

가격과 거래량의 관계에 대한 실증연구 -서울시 주택시장을 중심으로-

류현욱 ( Hyun Wook Ryu ),고성수 ( Sung Soo Koh ) 한국부동산분석학회 2012 不動産學硏究 Vol.18 No.3

Understanding market structure is meaningful, especially amid uncertainty swirling around market. In financial market, liquidity is an important determinant of the price. More recent studies attempt to figure out the positive correlation between price and trading volume from either capital market imperfection or decision theory. This study takes a step forward in analyzing Seoul residential real estate market by applying market liquidity to the relationship between price and trading volume. The primary contribution of this research is to provide answers to questions regarding how trading volume acts as an indicator of liquidity, moving the housing price. Vector Error Correction Model (VECM) analysis confirms; improved liquidity reduces negative factors affecting the value of house thus shifting the price upward. Policy implications of the exogenous variables are also discussed.

주택시장의 유동성효과에 관한 연구

류현욱(Hyun-Wook Ryu),고성수(Sung-Soo Koh) 한국주택학회 2013 주택연구 Vol.21 No.3

금융시장에서 유동성은 투자자에게 중요한 변수이고 위험에 대한 보상의 개념으로 할인되거나 웃돈의 개념으로 가감된다. 호황기에는 거래가 많아지고 풍부해진 유동성은 가격을 견인하는 요인으로 작용한다. 반대로 불황기에는 여러 가지 요인으로 말미암아 거래가 위축되고 낮아진 유동성이 가격을 더욱 하락시킨다. 주택시장의 경우 기존연구들이 가격변화에 대한 거래량효과가 있을 수 있음을 시사하고 있다. 본 연구는 경기상승기에 주택시장의 중심가치가 투자적양상을 보이는 현상에 주목하고 금융투자시장에서 연구되고 있는 거래량효과에 대해 분석하였다. 거래량효과는 거래비용을 낮추어 자산가치를 높이는 유동성에 따른 위험요인이 요구수익률에 반영되는 유동성효과의 관점에서 고찰하였다. 회귀분석결과 유동성효과는 경기변동에 비대칭적으로 나타나 시장수요의 변화에 따라 투자에서 실수요중심으로 재편됨을 확인할 수 있었다. 부동산이 갖는 정보의 불완전성(imperfection)과 비유동성(illiquidity)은 자본시장에서 해당자산에 대한 투자를 꺼리게 하는 대표적 요인임에도 불구하고 해당 분야에 대한 연구가 부족한 실정이다. 본 연구는 주택경기침체기에 가격안정화에 대한 고민이 깊어지는 정부에 참고할만한 시사점을 제시했다는 측면에서 연구의 의미를 찾을 수 있다. 그러나 짧은 시계열의 한계와 함께 세분화된 시장간 또는 시장에 대한 향후연구는 현실적 요구에 좀더 부합할거라 본다. In the financial sector, many studies have attempted to explore the causes of and the effects of market liqudity where trading volume plays certain roles shifting price. In real estate field, more studies have focused on housing price and the consequences of turnover. This study rather sheds lights on liquidity effects on the residential housing market as observed in financial markets. Utilizing a regression model, it predicts that an increase in trading volume results in an increase in liquidity premium leading to higher value response coefficients. The study has several empirical implications that could be tested in future research. Comparative analysis of regional and/or size-wise complexes within a city or district would be useful to see how liquidity effect works in micro-market wise.

전세서비스시장의 변화에 관한 연구

류현욱(Ryu, Hyun-Wook),고성수(Koh, Sung-Soo) 한국주거환경학회 2015 주거환경(한국주거환경학회논문집) Vol.13 No.1

Housing service can be viewed as a consumption good or investment good. This study reflects the views of decision-makers of potential homeowners in that their decisions can be made based upon the economic cycle where they rather stay in rental home during the downturn. This study is to show and test whether Chonsei value react to market situations, in other words, consumers" behavior. This study was based on literature review and statistical analysis. For the statistical varification, regression analysis was utilized to prove the results. The estimated result shows that Chonsei price is inversely related to investment market sentiments in which housing price expectation is used as alternative independent variable. The implications for the findings for policymakers and the housing rental market are important and possibly reassuring. The absence of strong evidence to suggest fundamental shifts in preference for homeownership following the economic downturn should assuage concerns that the investment sentiments has irreversibly changed in the last few years. It appears that demand for home; in other words, the drivers of homeownership preference, is related to market conditions in that lowered investment merit leads to wait-and-see attitude (staying in rental home). The theoretical model, Stock-Flow model, shows that lowered likelihood of buying stemming from external shocks to the market results in altering perceptions about the appeal of monthly renting over Chonsei. This would shifts the graph bringing about Chonsei price to increase. It is noted that homeowners" renting pattern exhibit strong associations with stated preferences for housing investment sentiments. The results provides usefulness in times of market downturn where tenants are suffering from increased rents.

SIR 정보 모형의 금융기관 적용방안에 관한 연구

류현욱(Hyun-Wook Ryu) 인문사회과학기술융합학회 2018 예술인문사회융합멀티미디어논문지 Vol.8 No.8

의학분야에서는 오래전부터 전염병의 전파경로를 예측할 수 있는 모형개발을 위해 연구해왔다. 소수의 감염자가 인구집단 내 다수를 감염시키는 과정에서 감염자의 수가 어떤 속도로 증가되고 회복되는지를 통해 주어진 변수에 따른 전파 경로 및 확산속도 등을 파악하는 데 기여한 바 있다. 이는 교통네트워크를 추정하는 이학분야에서 정보의 흐름을 감지하는 SNS 등 경영과학 분야에 까지 연구 된 바 있다. 자산관리분야에서 자기주도형 투자자가 증가하고 있는 상황에서 세분화된 고객층에 맞춤형 대응의 효과성을 살펴보기 위해 SIR 모형을 적용했다. 미분방정식 기반의 동모형을 통해 고객관계관리(CRM) 시스템의 시뮬레이션 모형을 설정했다. 본 연구에서는 확장형 모형인 SEI로 정보흐름과 의사결정구간을 추정했으며 구간별로 어떤 전략적 접근법이 적정할 수 있는지에 대해 고찰했다. 그 결과 자산관리로의 잠재적 고객(일정 자산 보유)은 범용의 접근전략 수준에 따라 특정 서비스에 노출되며, 구체적인 시스템적 접근 내지는 콘텐츠 수준에 따라 특정 상품을 거래하는 속도에 해당하는 계수값 베타에 영향을 준다. 이는 나아가 재투자 의사결정 수준에 까지 영향을 줄 수 있게 된다. 본 연구는 자산관리 비즈니스 환경 변화와 고객관리체계를 살펴보고 정보의 흐름이 투자 내지는 재투자로 이어지는 흐름을 연구모형을 통해 분석하고 전략적 방향을 도출한다. In the field of biological medicine, researchers have studied to develop epidemic spreading model since quite a while ago. The studies show how a contagious disease could spread; the speed to which small number of progressor infect many others in the group of the susceptible, and how fast those are recovered. The prediction contributes to figure out what variables lead to the greatest influence(s). Studies have been conducted on scientific engineering area such as estimating transportation network, and on management science area such as detecting information flow(s) in Social Network Services. With the number of self-directed investors increased in wealth management field, this paper applies SIR model to examine the effectiveness of information provided via CRM system. The differential equation-based model is utilized in order to project simulation out of decision making process via information flow(s). The model is customized to SEI where a potential client is exposed to particular firm in wealth management industry, and makes investment decision as the firm approaches and provides ‘proper contents’ in a timely manner. The model suggests that Beta parameter increases the rate of individuals moving from susceptible status to a firm’s management sight; the exposed. Injecting proper contents to the exposed makes the exposed clients decide particular investment(s), and further leads to re-investment. This study presents the changes in the recent business environment of wealth management, and presents whether an information leads to investment decision.

Evaluation of the radiopacity and cytotoxicity of resinous root canal sealers

김창규,류현욱,장훈상,이병도,민경산,홍찬의,Kim, Chang-Kyu,Ryu, Hyun-Wook,Chang, Hoon-Sang,Lee, Byung-Do,Min, Kyung-San,Hong, Chan-Ui The Korean Academy of Conservative Dentistry 2007 Restorative Dentistry & Endodontics Vol.32 No.5

본 연구의 목적은 세 가지 레진계 근관충전실러 (AH 26, EZ fill, AD Seal), 산화아연 유지놀계 근관충전실러(ZOB Seal) 그리고 수산화칼슘계 근관충전실러 (Sealapex)의 방사선 불투과성 및 세포독성을 평가한 것이다. 각 실러를 제조회사의 지시대로 혼합하여 직경 10 mm, 두께 1 mm로 시편을 제작한 후 ISO 6876/2001의 규격에 따라 교합필름을 이용하여 알루미늄 스텝웨지와 함께 방사선 촬영을 시행하였다. 방사선 사진을 디지털화하여 컴퓨터에 저장한 후 Scion image 프로그램을 이용하여 각 단계의 알루미늄 스텝웨지의 두께와 비교하였다. 각 재료의 세포 독성은 불멸화된 인간 치주인대세포 (immortalized human periodontal ligament cell, IPDL)에서 MTT 분석법을 이용하여 시행하였다. EZ fill이 가장 높은 방사선 불투과성을 나타내었고 Sealapex가 가장 낮은 방사선 불투과성을 나타내었다 (p < 0.05). AH 26, AD Seal, ZOB Seal은 중등도의 방사선 불투과성을 나타내었다. Sealapex를 제외한 모든 평가된 재료는 ISO 규격에 부합하는 방사선 불투과성을 보였다. 레진계 실러의 세포독성은 모든 실험 시간대에 걸쳐 다른 계통의 실러에 비해 낮게 나타났다 (p < 0.05) 아울러, EZ fill은 24및 48시간대에서는 AD Seal에 비해, 72 시간대에서는 다른 두 레진계 실러에 비해 높은 세포독성을 보였다. 그러나 레진계 실러에서 방사선 불투과성의 정도와 세포독성과의 관련성은 없었다 (p > 0.05). 이 실험 결과로 볼 때 레진계 실러는 다른 계통의 실러에 비해 방사선 불투과성 면에서 장점을 가지며 생체적합성면에서 우수하다고 사료된다. The aim of this study was to evaluate the radiopacity and cytotoxicity of three resin-based (AH 26, EZ fill and AD Seal), a zinc oxide-eugenol-based (ZOB Seal), and a calcium hydroxide-based (Sealapex) root canal sealers. Specimens, 10 mm in diameter and 1 mm in thickness, were radiographed simultaneously with an aluminum step wedge using occlusal films, according to ISO 6876/2001 standards. Radiographs were digitized, and the radiopacity of sealers was compared to the different thicknesses of the aluminum step wedge, using the Scion image software. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, the cytotoxicity of each material was determined in immortalized human periodontal ligament (IPDL) cells. The results demonstrated that EZ fill was the most radiopaque sealer, while Sealapex was the least radiopaque (p < 0.05). AH 26, AD Seal and ZOB Seal presented intermediate radiopacity values. All the materials evaluated, except for Sealapex, presented the minimum radiopacity required by ISO standards. The cell viabilities of resin-based root canal sealers were statistically higher than that of other type of root canal sealers through the all experimental time. Further, EZ fill showed statistically lower cell viability in 24 and 48 hours compared to AD Seal and in 72 hours compared to all other resin-based root canal sealers. However, there was no correlation between the radiopacity and cytotoxicity of three resin-based root canals sealers (p > 0.05). These results indicate that resin-based root canal sealer is more biocompatible and has advantage in terms of radiopacity.