내동정맥루수술에 있어서 자가정맥과 인조혈관(PTFE)의 개존율 비교

유선경,권태원,한덕종,김석구 울산대학교 의과대학 1996 울산의대학술지 Vol.5 No.1

The internal arteriovenous fistula is essential treatment modality of end stage renal disease. The majority of the end stage renal disease patients depend on hemodialysis, including those waiting for kidney transplantation or those suffering from rejection after kidney transplantation to sustain their lives. The long team patency and low complication rate of internal arteriovenous fistula are important for the quality of patient's life. The aim of this study is to compare primary and secondary patency between native vein & polytetrafluoroethylene (PTFE) for internal arteriovenous fistula(AVF) for long - term hemodialysis. The influence of diabetes on the primary and secondary patency of internal arteriovenous fistula is also studied. All native vein & PTFE AVF constructed between June 1989 & December 1994 at Asan Medical Center were retrospectively reviewed. Wilcoxon test was used to compare the primary and secondary patency rates of native vein AVF(n:299) with PTFE AVF(n:154). The ratio of male to female was 318: 210(1.5:1). The diabetes patient was 184cases(34.8%). The primary patency rate of native vien showed no significant difference to that of PTFE AVF(p=0.0539). The secondary patency rate of native vein is superior to that of PTFE AVF(p=0.0428). Both of primary and secondary patency rate in internal arteriovenous fistula for non-DM patients were superior to DM patients(p=0.0008, p=0.0105). In conclusion, we can use the PTFE as an alternative choice of material for internal arteriovenous fistula if there is no suitable native veins. We could expect good patency rate under the appropriate indications. We must try salvage procedure first on the failing graft before making another internal arteriovenous fistula on the any other site, especially on the native vein cases. Diabetes is a negative factor on the primary and secondary patency of internal arteriovenous fistula.

Knowledge Asymmetry and Issuer Behavior : The Case of Retail Structured Equity Product

Won-Suk Liu,Young-Min Choi,Young-Sik Kim 한국재무학회 2012 한국재무학회 학술대회 Vol.2012 No.05

This paper investigates Korean retail structured products, uncovering evidence that issuers proteer by increasing product complexity. Using unique data, for which degree of complexity is measurable by the type or dimension of the underlying asset, we report monotonically increasing mark-up premia and J-shaped issue amounts in relation to complexity. The result with respect to mark-up premia may be explained in a rational framework considering hedging costs; however, this is not the case with respect to issue amounts, leading us to surmise a hidden issuer incentive. Accordingly, we introduce a simple model, allowing investors with imperfect knowledge, and attempt to reconcile the result with model implications. The model proves that knowledge asymmetry is the key condition for issuers to oer complex products and to enjoy higher excess prot, thus worsening allocative eciency. Further, we show that the model explains our empirical results well, when knowledge asymmetry is veried as a strictly increasing convex function of complexity.

스마트-베타 포트폴리오의 변동성관리에 관한 연구: 아시아-태평양 지역 주식시장을 중심으로

유원석(Won-Suk Liu) 강원대학교 경영경제연구소 2019 Asia-Pacific Journal of Business Vol.10 No.3

In this paper, we investigate the performance of anomaly factors in Asia-Pacific Stock market and show the higher Sharpe ratio of the volatility managed smart beta portfolio. The smart beta portfolio combines the benefit of passive strategy and active strategy. However, the smart beta portfolios are seems to be exposed to the risk of anomaly factors from the perspective of traditional financial equilibrium model. Therefore, the smart beta strategy may generate negatively skewed returns unappealing to investors having lower risk tolerance. Our empirical investigations find that the return of the Asia-Pacific region stock market is more volatile than other regions with the lower efficiency ratio. However, the value factor and the momentum factor of Asia-Pacific region both show good performances. More interestingly, we also find that managing the volatility of the momentum factor in Asia-Pacific stock market almost doubles the efficiency ratio.

경기변동에 따른 위험의 가변성이 포트폴리오 위험관리에 미치는 영향에 관한 연구

유원석(Liu, Won-Suk) 한국경영교육학회 2013 경영교육연구 Vol.28 No.5

기존 실증연구들은 많은 투자자들이 충분한 자산다각화를 하지 않고 있으며, 자산의 체계적 위험 및 고유한 비체계적 위험 또한 시간에 대한 가변성을 보인다는 결과를 제시하고 있다. 이는 투자자 입장에서 포트폴리오의 횡단면적 위험뿐만 아닌 시계열적인 위험을 파악하고 관리할 수 있어야 함을 의미한다. 본 연구는 경기변동(business cycle)에 따른 체계적 위험 및 비체계적 위험의 시가변성이 포트폴리오에 미칠 수 있는 영향에 대하여 분석하여, 위험 간 상관관계에 대한 이해와 활용의 의의를 제시하고자 하였다. Fama-French의 size/book-to-market 25개 포트폴리오의 체계적/비체계적 위험을 SUR (seemingly unrelated regression) 모형과 베이지안 방법을 이용하여 횡단면 및 시계열적으로 추정하여 분석한 결과, 체계적 위험의 경우 경기변동에 따라 유의한 변화가 관찰되는 포트폴리오와 그렇지 않은 포트폴리오가 존재하였으며 변화가 관찰되는 경우에도 그 양상은 포트폴리오에 따라 상이한 것으로 나타났다. 반면 비체계적 위험의 경우 경기가 침체국면으로 전환될 때 모든 포트폴리오에서 위험이 증가하는 모습이 나타났다. 또한 포트폴리오 구성 방법에 따른 위험 간 상관관계를 분석한 결과, 각 경기국면에서 상관계수가 음의 값부터 높은 양의 값까지 넓은 범위에 거쳐 분포하고 있음을 확인할 수 있었다. This study investigates the time-varying risk patterns of size/book-to-market sorted 25 portfolios over the period from 1954 to 2011. Through the extensive empirical analysis, we find that correlation between time varying risks may provide an effective way of managing the rime varying risk either in good times or in bad times. Estimating the SUR model leads us to find reliable evidence that larger size and higher book-to-market ratio decrease portfolio betas, and that time varying properties of beta and idiosyncratic risk show diverse aspects from portfolio to portfolio. From the perspective of investors, the result reveals the difficulty of managing portfolio risk arising from business cycle. However, using Bayesian method, we estimate a mean-reverting stochastic beta model to generate time series of beta and idiosyncratic risk, and obtaining 25 × 25 correlation matrix of time varying risk where correlations range from negative value to positive depending on a combination of portfolio. The results implies that an investor may control portfolio risk by selecting assets, of which time varying risks are properly correlated on his/her purpose.

복잡성, 지식격차, 그리고 독점적 경쟁: 구조화상품 공모시장 분석

유원석 ( Won Suk Liu ),최영민 ( Young Min Choi ) 한국파생상품학회(구 한국선물학회) 2013 선물연구 Vol.21 No.4

본 연구는 독점적 경쟁모형을 통해서 구조화상품 시장을 모형화하여 상품의 복잡성이 일반투자자에게 미치는 영향을 살펴보고, 실제 발행된 주가연계증권에 대한 분석결과를 통해서 모형을 실증적으로 뒷받침하고자 하였다. 먼저 이론적 연구결과에 따르면 상품의 복잡성으로 인하여 발생하는 지식격차(knowledge asymmetry)가 발행자들이 복잡한 상품을 개발하는 중요한 유인이며, 복잡한 상품에 대한 투자자의 수요가 큰 경우에 발행자들이 상품의 복잡성을 증가시켜 초과이윤을 획득하고자 하는 유인이 발생하는 것으로 나타났다. 이는 상품의 복잡성으로 인해 구조화상품 시장의 분배 효율성이 저하될 수 있음을 시사한다. 또한 국내 주가연계증권 자료를 이용한 실증분석 결과, 상품의 복잡성이 증가할 때 판매가격은 단조증가하나 발행량은 비단조적인 J-형태인 것으로 나타났다. 본 연구에서 제시한 모형에 따르면 이는 지식격차가 복잡성에 대한 지수함수 형태일 때 관찰되는 결과로, 향후 구조화상품 시장이 보다 복잡한 상품을 중심으로 발전할 수 있음을 시사한다. This paper introduces a monopolistic competition model containing retail investors with imperfect knowledge and issuers offering complex structured products. The model, for which we provide empirical evidences supporting the issuer`s profiteering by increasing the product complexity, can explain that knowledge asymmetry is the key for the issuer to offer complex product and to enjoy the higher excess profit, thus worsening allocative efficiency. Our empirical analysis reports monotonically increasing mark-up premia, and J-shaped issue amounts with respect to complexity: the former result could be explained in a rational framework considering issuer costs, however, the latter is not the case. Our model proves the empirical results are well explained when knowledge asymmetry between issuer and investors is a strictly increasing convex function of complexity.

특발성 척추측만증에서 척추경 나사 고정술과 갈고리 고정술의 흉추 후만 복원력의 비교

석세일,김진혁,김원중,이상민,유일,이창섭,정의룡,윤영식 대한척추외과학회 1998 대한척추외과학회지 Vol.5 No.2

Study design: This is a retrospective study. Objectives: To verify the advantage of segmental pedicle screw fixation in restoration of thoracic kyphosis in hypokyphotic patients. Summary of background data: Restoration of thoracic kyphosis is essential for a satisfactory three dimensional correction in thoracic AIS. However, with significant preoperative hypokyphosis, the result of multiple hook fixation was often unsatisfactory. Methods: Fifty-one patients with thoracic AIS treated by posterior instrumentation and followed up for more than 2 years were divided into 3 groups each comprising 17 patients. HypokyphosisHook(HH) group comprised patients with thoracic kyphosis less than 15° treated by multiple hooks. Hypokyphosis-Screw(HS) group comprised hypokyphotic patients treated by segmental pedicle screws. Normal kyphosis-Screw(NS) group comprised patients with kyphosis greater than 15° treated by segmental pedicle screws. Preoperative thoracic kyphosis was 4.1±8.6°, 8.1±5.6° and 27.3±9.8° in the HH, HS and NS group respectively. There was no significant difference between the HH and HS groups(p=0.39). Three groups were compared for restoration of thoracic kyphosis. Results: At the final follow up, the thoracic kyphosis was 14.5±10.2° 27.3±11.3° and 28.3±13.7° in the HH, HS group and NS group showing correction of 10.0±10.0°, 19.2±14.0° and 0.4±12.3° respectively. There was a significant difference between HH and HS group(p=0.0008). However there were no difference between the HS and the NS group(p=0.8). Conclusions: Segmental pedicle screw fixation was more effective than multiple hooks in restoring the thoracic kyphosis in AIS patients with hypokyphosis. The restored kyphosis was similar to that obtained in patients without hypokyphosis.

Electrochemical properties of Fe₂O₃ thin film fabricated by electrostatic spray deposition for lithium-ion batteries

Suk Ryu, Ho,Seon Kim, Jong,Guo, Zaiping,Liu, Huakun,Won Kim, Ki,Hyeon Ahn, Jou,Jun Ahn, Hyo Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139

<P> Fe<SUB>2</SUB>O<SUB>3</SUB> thin films are important for the fabrication of rechargeable lithium microbatteries. Thin films of Fe<SUB>2</SUB>O<SUB>3</SUB> were prepared by the electrostatic spray deposition (ESD) technique by using iron chloride as the precursor. The thin film electrodes, without inert additives such as polymer binder and conducting material, can deliver a first discharge capacity of 912 mA h g<SUP>−1</SUP> and retain a discharge capacity of 537 mA h g<SUP>−1</SUP> at a current density of 200 mA g<SUP>−1</SUP> to the 100th cycle. The coulombic efficiency of the Fe<SUB>2</SUB>O<SUB>3</SUB> thin-film electrode was over 96% after several cycles.</P>

후방도달척주절제술을 이용한 요천추 후만 변형의 교정 : 예비 보고 A preliminary report

석세일,김진혁,김원중,이상민,유일,정의룡,이창섭 대한척추외과학회 1998 대한척추외과학회지 Vol.5 No.2

Study design : This is a retrospective study evaluating the efficacy of new surgical technique for treatment of fixed lumbosacral kyphosis. Objectives : To report a new method of vertebral column resection and to determine its efficacy in the treatment of fixed lumbosacral kyphosis. Summary of Background data : The treatment of fixed severe spinal deformity is very difficult and only a few surgical methods are reported. The vertebral column resection from anterior and posterior is a radical method to treat the severe deformity but it has many problems with anterior and posterior approachs. Materials and methods : A new surgical method of vertebral column resection from posterior approach only(PVCR) was carried out in 5 patients of fixed lumbosacral Th kyphosis from October 1997 to March 1998. The mean age was 43.4 years(range 35-61 years), and four were female and one male. The average postoperative follow-up period was 5.5 months(ranged from 2 months to 12 months). An average of 2.6 vertebrae was resected. The degree of sagittal curves was measured using the Cobb technique preoperatively and postoperatively : the rejional lumbosacral kyphotic angle and compensatory thoracic curvature from T4 to T12. The sagittal imbalance was measured by distance from C7 plumb line to postero-superior corner of S1 using 14 × 36 inch standing lateral radiograph. Results : The sagittal deformities were corrected from an average of kyphosis 37.4 to lodosis 8.4 at lumbosacral level and from an average of lodosis 31.6 to lodosis 8.2 at thoracic level. The sagittal imbalance was improved from an average of +11.7㎝ to +2.2㎝, for a posterior immigration of 9.5 cm. The mean operating time was 334 minutes and with an average blood loss of 4338m1. Complication comprised of motor weakness with deep wound infection in one case and superficial wound infection in another case. The transient hip flexor weakness was seen in all the patients. The hip flexor power recovered in 3-4 weeks. The patient of motor weakness and deep infection showed partial motor improvement and complete wound healing at last 2 month follow-up. Conclusion : one-stage posterior vertebral column resection is a promising technique for treatment of the severe fixed lumbosacral kyphosis.

분절 척추경 나사 고정술 및 감염술을 이용한 King 제5형 청소년기형 특발성 척추측만증의 치료

석세일,김진혁,김원중,이상민,유일,이창섭,정의룡,고재근 대한척추외과학회 1998 대한척추외과학회지 Vol.5 No.2

Study design : This is a retrospective study. Objectives : To verify the efficacy of the separate curve derotation technique by segmental pedicle screw fixation in King type V adolescent idiopathic scoliosis(AIS). Summary of background data : King type V AIS is commonly treated by fusion of both the upper and the lower thoracic curve. However, both curves fusion often leads to undesirable shoulder asymmetry by relative overcorrection of the more flexible lower thoracic curve. Methods : Fourteen patients subjected to both curve fusion with segmental pedicle screw fixation by separate curve derotation were analyzed after a minimum follow-up of 2 years. The group comprised 11 females and 3 males with a mean age of 15.9 years. All patients had upper left thoracic and lower right thoracic curve pattern. The upper thoracic curve was 46.2±10.3° with a flexibility of 39.6%. The lower thoracic curve was 54.3±14.5° with a flexibility of 59.1 %. Preoperatively, shoulder was level in 4, left elevated in 8 and right elevated in 2 patients. Results : At the final follow up, the upper thoracic curve was corrected to 21.5±8.7° showing a correction of 52.8%. The lower thoracic curve was corrected to 20.0±0.6° showing a correction of 63.5 %. All the patients had improvement of shoulder height difference and trunk balance clinically and radiologically. Conclusions : Segmental pedicle screw fixation and separate derotation is an effective method of restoring shoulder symmetry and maintainig trunk balance in King type V AIS.

Growth Retardation of Plants Transformed by Overexpression of NtFtsZ1-2 in Tobacco

Jeong, Won Joong,Jeong, Suk Won,Min, Sung Ran,Yoo, Ook Joon,Liu, Jang Ryol 한국식물학회 2002 Journal of Plant Biology Vol.45 No.2

We transformed tobacco plants (Nicotiana tabacum L, Xanthi) by introducing a sense construct of NtFtsZ1-2. This tobacco nuclear gene encodes a chloroplast-localized homologue of FtsZ, the bacterial cell-division protein. The over-expressing plants contained enlarged chloroplasts in their leaf mesophyll cells. In the T_1 progeny, we observed three different phenotypes: 1) plants with cells containing many small chloroplasts, which was the same as for wild-type plants; 2) plants in which the cells contained one to three enlarged chloroplasts (severe type); and 3) plants whose cells contained a combination of many small chloroplasts and one to three enlarged chloroplasts (intermediate type). The outward appearance of the severe and intermediate types of transgenic plants did not differ noticeably from the wild-types. However, the severe-type plants were most retarded in their growth under both high- and low-light conditions, followed by the intermediate-types. Under medium levels of light, the two types of transgenic plants exhibited growth rates comparable to that of the wild types. Based on the overall results, we suggest that many small chloroplasts, rather than a few large chloroplasts, are required for efficient use of light energy in the mesophyll cells.