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- 저자 : 이승학(Lee, Seung-Hak) (검색결과 108 건)
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수송모형이론에 의한 토공 운반 최적화 모델 및 프로그램 개발
이승학,손재호,편재호,이승현,Lee, Seunghak,Son, Jaeho,Pyeon, Jaeho,Lee, Seunghyun 한국건설관리학회 2016 한국건설관리학회 논문집 Vol.17 No.1
도로공사 토공사 작업현장에서 수행되는 운반계획의 주요 목적은 절토량과 성토량 간의 균형을 맞추는 것과 운반비용, 운반거리를 최소화 하는 것이다. 토공사의 합리적인 운반계획은 공사비 및 공사기간에 직접적인 영향을 미치나, 기존의 토공사 운반계획은 현장관리자의 경험적 지식을 기반으로 토공 운반계획을 수립하는 실정이다. 이에 본 연구에서는 도로공사 토공사 작업현장의 토공물량 운반계획의 효율성 향상을 위해 활용할 수 있는 최적화 모델 개발 하였으며, 사례구간을 통해 본 연구를 적용시킨 결과 공사기간은 약 19%, 공사비는 약 11% 감소시킨 것으로 확인되었다. During road construction, minimizing haul and return distances as well as keeping a balance between cut and fill quantities are two of the key tasks for earthmoving operation planning. The result of the earthwork planning has a significant impact on the construction cost and duration. Although there have been research efforts regarding optimized earthwork planning using linear programming, the current practice of selecting earthwork planning methods typically depends on a field manager's intuitive and/or experimental knowledge. Furthermore, there is no system considering earthwork influential field factors including the transportation distance, the earthwork quantity, and the recycling ratio of earth volume. Therefore, this research focuses on the development of such a model for planning the optimized earthwork to increase the efficiency of a road construction. The proposed model is developed based upon the transportation problem method which is a part of Linear Programming. The application result of optimization model on a case study shows that the duration and cost for earthwork ha sbeen reduced approximately 19% and 11% respectively
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이승학,김문경,한용해,심창구,Lee, Sung-Hack,Kim, Moon-Kyoung,Han, Yong-Hae,Shim, Chang-Koo 한국약제학회 1994 Journal of Pharmaceutical Investigation Vol.24 No.3
In the present study, quantitative and qualitative histology was used to assess the effects of ibuprofen suppositories with various treatments on the rectal mucosa of rats. Two suppositories were prepared with Witepsol W35 and compared with two commercial ibuprofen suppositories Reference I (Showa Pharm.ind., Tokyo, Japan), Reference II (P.Pharm., Seoul, Korea). Single and multiple dose(dosing interval 4 hr, n=4) studies were conducted. All suppositories significantly increased epithelial cell loss, but the extent of rectal irritation was variable. These studies showed that the incorporation of ibuprofen into the suppository bases increases the morphological change in rectal tissue both for the single and multiple administrations of suppositories, but which was significantly recovered within 24 hr although the interanimal variability in scores was very substantial. Multiple administration of ibuprofen suppositories caused significant damage to rectal mucosa, but it must be considered that these were under the severe condition, that is, interval of administration (4 hr) was three times shorter than normal interval of administration and dose was fifteen times larger than usual human dose. Aluminum oxide $(Al_2O_3)$, a dispersing agent, slightly increased the irritation of rectal mucosa in rats at 5 hr and 24 hr after multiple administration, but it was possible to ignore the difference of irritation in the data at 5hr and 24hr after single administration. Finally, it was concluded that Witepsol W35 and ibuprofen had a slight rectal mucosa-irritating effect on the usual human dose, and ibuprofen suppositories prepared with Witepsol W35 or Witepsol W35, $Al_2O_3$ showed almost similar extent of rectal irritation with commercial ibuprofen products.
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벤처캐피탈 유형별 IPO 보증역할: 독립벤처캐피탈과 사내벤처캐피탈 비교
이승학 ( Seunghak Lee ),윤병섭 ( Byungseop Yoon ) 한국중소기업학회 2018 기업가정신과 벤처연구 Vol.21 No.3
본 연구는 2008년 1월 1일부터 2017년 12월 31일까지 10년 연구기간 동안 코스닥시장에 IPO한 기업 중 CVC가 투자한 기업 87개, IVC가 투자한 기업 74개를 표본으로 CVC와 IVC 사이 투자지분율, 공모비율 등의 분석을 통해 보증역할의 차별성을 논의하였다. 첫째, 벤처캐피탈을 IVC와 CVC로 양분하고 양 집단 사이 어느 유형이 저가발행을 완화하는 데 보다 더 공헌을 하는지 분석한 결과 AR(1.1), CAR(1.3), CAR(1.7) 구간에서 CVC가 IVC보다 초과수익률과 누적초과수익률에 체계적으로 유의한 음(-)의 영향을 미치고 있었다. 이는 전략적 목적의 투자를 선호하는 CVC가 재무적 목적의 투자수익률을 추구하는 IVC보다 보증역할을 더 충실히 한다고 판단할 수 있다. 둘째, 벤처기업이 IPO할 때 벤처기업에 투자한 벤처캐피탈의 투자지분율에 따라 초과수익률의 변화를 분석한 결과 CVC 지분율이 높을수록 IVC 지분율이 높을 때 보다 초과수익률이 낮게 나타나 CVC가 IVC보다 보증역할이 더 우월함을 보여주고 있다. 셋째, 벤처기업이 IPO할 때 공모비율에 따라 초과수익률이 어떻게 나타나는지 분석한 결과 CVC 공모비율이 높을수록 ICV 공모비율이 높을 때 보다 초과수익률이 낮게 나타나 CVC가 IVC보다 보증역할이 더 우월함을 보여주고 있으며, AR(1.1), CAR(1.3) 구간에서 나타나는 유의한 음(-)의 영향이 이를 증명하고 있다. 이는 Wang and Wan(2013)의 연구를 지지한다. This study analyzed that which types of groups contribute more to mitigating low-cost issuance after dividing venture capital into IVC and CVC. This study discussed the differentiation of the certification role through analysis of investment share and public offering ratio between CVC and IVC on the sample of 87 companies invested by CVC and 74 companies invested by IVC among the KOSDAQ market during 10-year research period from January 1, 2008 to December 31, 2017. The results are as follows. First, an analysis of which type more contributes to the mitigation of low-cost issuance between the two groups showed that CVC had a systematically significant negative (-) effect on abnormal return and cumulative abnormal return than IVC at section AR (1.1), CAR (1.3), CAR (1.7). This can be judged that CVC, which prefers investment for strategic purposes, is more faithful to its certification role than IVC, which pursues return on investment for financial purposes. Second, the analysis of whether the investment share of venture capital invested in venture business shows low abnormal return when venture business do IPOs. showed a significant difference between each section AR (1.1), CAR (1.3), CAR (1.7), CAR (1.30). The higher the share of venture capital investments invested in venture business in each segment, the more systematically significant negative impact on abnormal return of venture IPOs. The higher the share of the CVC invested in venture business, the more likely it can be accepted as the certification role of CVC to mitigate the low-cost issue of the venture IPO. Third, an analysis of whether the abnormal return is low for venture business’ IPO according to the public offering ratio found that the higher public offering ratio, the more significant negative (-) effect was found in the interval AR (1.1), CAR (1.3). This can be seen as a certification role of venture capital, which distributes risks and increases efficiency of operation, while reducing low-cost issuance of IPO. Therefore, it can be judged that the higher the public offering ratio, the more closely the IPO price is decided to market value, demonstrating the certification role of venture capital that mitigates the low-cost issuance of IPO. However, there is a need to identify the certification role of venture capital by dividing the target companies according to the level of the CVC and IVC investment share and revealing the portion of the investment share that shows a slightly lower abnormal return.
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