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      • KCI등재

        Photoresponsive Azobenzene-cored Dendrons with Terminal Vinyl Groups

        최대옥,Ji-hye Lee,Kyong-ha Shin,신은주 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.6

        Azobenzene-cored dendrons having the photoisomerizable azobenzene core and terminal vinyl groups have been prepared. Absorption bands of azobenzene-cored dendrons are similar except more intense 280nm band in higher generation azobenzene dendron. All three azobenzene-cored dendrons show reversible photoisomerization similar to simple azobenzene, irrespective of the generation of dendron. On 350nm irradiation, absorption band around 344nm decreases and 436nm band increases. Photoisomerization reactions are very fast for all three azobenzene-cored dendron and the reaction efficiency is dependent of its generation and solvent. In the dark, slow thermal reversion to original absorption spectrum is observed.

      • KCI등재

        Porphyrin-Cored Arylether Dendrimers with Vinyl Groups in the Periphery

        최대옥,신은주,So-yeon Lim 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.7

        Benzyl arylether dendrimers with zinc porphyrin core and terminal vinyl groups have been synthesized and their photophysical properties and the influence of dendritic environments were investigated. Free base porphyrin-cored benzyl arylether dendrimers 1a-1c and 3a-3c, and their zinc derivatives 2a-2c and 4a-4c have been prepared. Absorption spectra are similar for all porphyrin-cored benzyl arylether dendrimers, except that absorption intensity at 280 nm increases in the higher generation of dendrimer. Fluorescence spectra are similar with two bands for all free base porphyrin dendrimers 1a-1c and 3a-3c, although fluorescence intensity ratio of shorter wavelength emission band to longer wavelength band varies with the generation of dendrimer. Emission efficiencies of 1a-1c and 3a-3c are lower than that of TTP. Emission efficiencies of 2a-2c and 4a-4c are higher than that of ZnTTP. Absorption and emission properties of 1a-1c, 2a-2c, 3a-3c, and 4a-4c were affected negligibly with dendritic environments.

      • SCOPUSKCI등재
      • KCI등재

        이중관으로 연결된 자연치와 임플랜트의 악골 내응력분포에 관한 3차원 유한요소분석

        이수,최대,권긍록,우이형,Lee, Su-Ok,Choi, Dae-Gyun,Kwon, Kung-Rock,Woo, Yi-Hyung 대한치과보철학회 2008 대한치과보철학회지 Vol.46 No.4

        서론: 임플랜트와 자연치가 혼재하는 증례에 있어서 보철물의 연결여부와 그 결과에 대해 논쟁이 많이 있어왔다. 본 연구에서는 임플랜트와 자연치를 이중관으로 연결했을 경우에 치조골 내에서 임플랜트 주변 조직의 하중에 대한 응력의 양상을 분석하여 자연 치와 임플랜트를 연결하는 보철물의 방식으로 이중관의 사용가능성을 비교 분석하고자 하였다. 연구재료 및 방법: 실험군으로서는 한 개의 자연치아와 한 개의 임플랜트를 이중관으로 연결한 모델을 사용하고, 대조군으로 두 개의 임플랜트를 이중관으로 연결한 모델을 사용하여 응력분포의 차이를 비교분석하였다. 임플랜트와 자연치 각각 통상적인 금합금을 사용하여 내,외관을 모델링한 후 각각의 외관을 연결한 구조를 형성한다. 내관과 외관은 $6^{\circ}$의 경사도 (taper)로 형성하고 내외관 사이의 공간을 인정하여, 하중을 가했을 경우 내외관 사이에 합금의 마찰력과 변위를 계산하여, 그 결과가 골내 임플랜트의 응력 분포에 영향을 줄 수 있도록 실험모델을 형성하였다. 하중은 일반적인 저작력의 크기로 임플랜트 부위와 자연치 부위에 각각 부여하여 응력의 차이를 비교하였으며, 최종적으로 대조군과의 차이를 비교하고자 하였다. 하중 조건은 임플랜트와 자연치아 사이, 임플랜트 후방, 전방부 자연치아의 사이에 하중을 가하였으며, Load case 1, 2, 3로 분류하였다. 실험을 위해서 ANSYS Version 8.1을 사용하여 3차원 유한 요소 분석을 시행하였다. 연구성적: 지대주에 가해지는 응력 - 최대 응력은 실험군이 대조군에 비해 각각 2.4 (Load Case1), 1.02 (Load Case2), 0.46 (Load Case3)배 높게 나타났으며,Load Case3의 경우 대조군의 최대응력이 더욱 높게 나타났는데, 이것은 전치부 치아의 경우 하중을 효과적으로 분산하기 때문인 것으로 보인다. 악골내에 가해지는 응력 - 악골내에서 최대 응력은 실험군이 대조군에 비해 각각 1.69 (Load Case1), 1.26 (Load Case2), 1.93 (Load Case3) 배 크게 나타났다 결론: 임플랜트와 자연치아가 혼재된 경우, 이중관으로 상부 보철물을 연결한 경우, 임플랜트만으로 구성된 대조군에 비해, 임플랜트 및 임플랜트 식립 부위의 악골에 가해지는 최대 응력은 1.02 에서 2.4배 가량 높게 나타났다. 자연치아의 움직임이 임플랜트의 경부 및 악골 내에 응력을 집중시킨 것으로 보이며, 자연치아가 있는 악골부위에서는 응력이 거의 발생하지 않았다. 본 실험의 경우 자연치아와 임플랜트에서 모든 하중을 받는 것으로 계산하였고, 실제 가철성 의치에서 나타나는 점막의 영향을 배제하였기 때문에, 실제 임상에서는 후방 임플랜트에 미치는 최대 응력의 크기는 2.4배 이하일 것으로 추정할 수 있다. 앞으로, 실제 임상에 적용하였을 경우, 임플랜트에 미치는 영향 및 자연치아에 미치는 결과에 대한 연구가 필요할 것이다. Purpoose: For decades dental implants have been used widely in the field of prosthetic dentistry. However there is confusion when establishing treatment plans in cases where some teeth are remained but an insufficient number of implants can be used due to limited anatomical status and ecomomical problems. Many clinicians have tried to connect natural teeth and implants, and it still has controversy. But, there have been few studies on mechanical analysis of connecting natural teeth and implants with konus telescopic removable partial dentures. The purpose of this study was to analyze the stress distribution of prosthesis, abutment and alveolar bone when teeth and implants were connected with the konus telescopic denture, by means of 3-dimensional finite element analysis. Material and methods: The assumption of this study was that there were 2 mandibular canine (11 mm in length, 4 mm in diameter) and 2 implants(10 mm in length, 4 mm in diameter) which are located in the second premolar region. The mandible, teeth, implants, abutments, and connectors are modeled, and analyzed with the commercial software, ANSYS Version 8.1(Swanson, Inc., USA). The control group used implants instead of natural teeth. 21038 elements, 23544 nodes were used in experimental group and 107595 elements, 21963 nodes were used in control group, Stress distribution was evaluated under 150 N vertical load on 3 experimental conditions - between teeth and implants (Load case 1), posterior to implants (Load case 2), between natural teeth (Load case 3). Results: 1. In all load cases, higher von mises stress value was observed in the experimental group. 2. Maximum von miss stress observed in all load cases and all locations were as follows ; a. 929.44 Mpa in the experimental group, 640.044 Mpa in the control group in outer crown and connector - The experimental group showed 1.45 times high value compared with the control group. b. 145,051 Mpa in the experimental group, 142.338 Mpa in the control group in abutment - The experimental group showed 1.02times high value compared with the control group. c. 32.489 Mpa in the experimental group, 25.765 Mpa in the control group in alveolar bone - The experimental group showed 1.26times higher value compared with the control group. 3. All maximum von mises stress was observed in load case 2, and maxim von mises stress in alveolar bone was 32.489 Mpa at which implant failure cannot occur. 4. If maximum von mises stress is compared between two groups, the value of the experimental group is 1.02 times higher than the control group in abutment, 1.26 times higher than the control group in alveolar bone. Conclusion: If natural teeth and implants are connected with the konus telescopic denture, maximum stress will be similar in abutment, 1.26 times higher in alveolar bone than the control group. With this result, there may be possible to make to avoid konus telescopic dentures where natural teeth and implants exist together.

      • SCOPUSKCI등재
      • KCI등재

        수요 예측 평가를 위한 가중절대누적오차지표의 개발

        최대일(Dea-Il Choi)창수(Chang-Soo Ok) 한국산업경영시스템학회 2015 한국산업경영시스템학회지 Vol.38 No.3

        Aggregate Production Planning determines levels of production, human resources, inventory to maximize company’s profits and fulfill customer's demands based on demand forecasts. Since performance of aggregate production planning heavily depends on accuracy of given forecasting demands, choosing an accurate forecasting method should be antecedent for achieving a good aggregate production planning. Generally, typical forecasting error metrics such as MSE (Mean Squared Error), MAD (Mean Absolute Deviation), MAPE (Mean Absolute Percentage Error), and CFE (Cumulated Forecast Error) are utilized to choose a proper forecasting method for an aggregate production planning. However, these metrics are designed only to measure a difference between real and forecast demands and they are not able to consider any results such as increasing cost or decreasing profit caused by forecasting error. Consequently, the traditional metrics fail to give enough explanation to select a good forecasting method in aggregate production planning. To overcome this limitation of typical metrics for forecasting method this study suggests a new metric, WACFE (Weighted Absolute and Cumulative Forecast Error), to evaluate forecasting methods. Basically, the WACFE is designed to consider not only forecasting errors but also costs which the errors might cause in for Aggregate Production Planning. The WACFE is a product sum of cumulative forecasting error and weight factors for backorder and inventory costs. We demonstrate the effectiveness of the proposed metric by conducting intensive experiments with demand data sets from M3-competition. Finally, we showed that the WACFE provides a higher correlation with the total cost than other metrics and, consequently, is a better performance in selection of forecasting methods for aggregate production planning.

      • KCI등재후보

        금속하부구조물이 도재의 색조에 미치는 영향에 대한 분광측색분석

        이수,우이형,최대,권긍록,Lee Su-Ok,Woo Yi-Hyung,Choi Dae-Gyun,Kwon Keung-Rok 대한치과보철학회 2003 대한치과보철학회지 Vol.41 No.2

        Statement of problem Metal-ceramic restorations have been used extensively by dental clinicians for nearly 40 years. Strength an functional ability of metal-ceramic restorations are proved to be satisfying, However esthetics and biocompatibility of metal alloy which is used in metal-ceramic restoration is not ideal. Using pure gold as an alternative, have advantage of esthetics, biocompatibility over conventional metal alloy. But there had been little article which studied on the color effect of pure gold on fual porcelain color. Purpose The purpose of this study was to spectrophotometrically evaluate the difference between color of metal alloy(Au-Pt, Ni-Cr) and pure gold, during color masking procedure with opaque porcelain and to analyze the differences, Material and Methods Three types of metal - base metal(Ni-Cr), high gold alloy(Au-Pt), pure gold(GES) - specimen were fabricated 1cm in diameter. Four steps were established - after finishing, after pre-coditioning, after application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness)- and tested color with spectrophotometer every each steps and analyzed with $CIEL^*a^*b^*$ color order system. One-Way ANOVA test was used to and out if there were significant differences between groups tested and Shaffe multiple comparison was used to identify where the differences were. Results 1. After finishing and pre-conditioning, pure gold(GES) group showed most high values in $L^*,a^*,b^*$. 2. After application of first opaque porcelain(0.08mm in thickness), after application of second opaque porcelain(0.15mm in thickness), pure gold(GES) group showed the least difference in $L^*,a^*,b^*$ values and the lowest ${\Delta}E$ value(${\Delta}E$=0.63). 3. After application of first opaque porcelain and after application of second opaque porcelain differences that were significant (P<0.05) between groups were found only in $a^*$ values. 4. Base metal alloy group showed the lowest $a^*$ value in test after application of first opaque porcelain and the highest value in test after application of first opaque porcelain Conclusion Pure gold group and high gold group showed higher $a^*$ values than base metal group when tested after 0.08mm thickness of opaque porcelain was applied and pure gold group showed much similar $L^*,a^*,b^*$ values between 0.08mm thickness and 0.15mm thickness of opaque porcelain. This meant that pure gold was more easily masked by opaque porcelain than the other two groups.

      • Synthesis and Pharmacological Evaluation of N-Benzyl 2-Substituted-2-acetamidoacetamides for Peripheral Nervous System Disorders

        Choi, Daeock 순천대학교 기초과학연구소 1997 基礎科學硏究誌 Vol.8 No.-

        Functionalized amino acid derivatives (2) were studied whether these can serve as new agents for the treatment of peripheral nervous system (PNS) disorders. Recently evidence has been presented that the commercial antiepileptic agent, phenytoin, was effective in pharmacological tests designed to model PNS diseases.^4 Accordingly, polar derivatives of 2 were synthesized and then evaluated both for central nervous system (CNS) and PNS activity using the MES-seizure and the acetic acid writhing tests, respectively. In this study, it was reasoned that polar derivatives of 2 might be selective to the PNS since they would be unlikely to cross the blood-brain barrier.

      • KCI등재

        수요 예측 평가를 위한 가중절대누적오차지표의 개발

        최대,창수 한국산업경영시스템학회 2015 한국산업경영시스템학회지 Vol.38 No.3

        Aggregate Production Planning determines levels of production, human resources, inventory to maximize company’s profits and fulfill customer's demands based on demand forecasts. Since performance of aggregate production planning heavily depends on accuracy of given forecasting demands, choosing an accurate forecasting method should be antecedent for achieving a good aggregate production planning. Generally, typical forecasting error metrics such as MSE (Mean Squared Error), MAD (Mean Absolute Deviation), MAPE (Mean Absolute Percentage Error), and CFE (Cumulated Forecast Error) are utilized to choose a proper forecasting method for an aggregate production planning. However, these metrics are designed only to measure a difference between real and forecast demands and they are not able to consider any results such as increasing cost or decreasing profit caused by forecasting error. Consequently, the traditional metrics fail to give enough explanation to select a good forecasting method in aggregate production planning. To overcome this limitation of typical metrics for forecasting method this study suggests a new metric, WACFE (Weighted Absolute and Cumulative Forecast Error), to evaluate forecasting methods. Basically, the WACFE is designed to consider not only forecasting errors but also costs which the errors might cause in for Aggregate Production Planning. The WACFE is a product sum of cumulative forecasting error and weight factors for backorder and inventory costs. We demonstrate the effectiveness of the proposed metric by conducting intensive experiments with demand data sets from M3-competition. Finally, we showed that the WACFE provides a higher correlation with the total cost than other metrics and, consequently, is a better performance in selection of forecasting methods for aggregate production planning.

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