• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 한국항해항만학회 2006년도 추계학술대회 논문집(제2권)
• /
• pp.51-54
• /
• 2006

최근 국내 중형급 조선소에서는 케미컬 탱커선을 주력선종으로 건조하고 있다. 하지만 선형개발 기술이 미비하여 저항감소 선형개발에 소홀하였다. 또한 기존 대형선박의 선형을 그대로 사용하기 때문에 추진효율이 떨어지고 많은 선수저항이 발생하여 선속에 큰 영향을 미치게 된다. 이에 본 연구에서는 CFD이론 해석을 통해 선형특성을 파악하고 저항감소 및 추진 효율 향상을 위해 실적선과 개발대상선의 모형시험을 통하여 선수저항 성능을 비교, 분석하여 저항감소 선수선형을 개발하였다.

• Journal of the Korean Society for Marine Environment & Energy
• /
• 제16권3호
• /
• pp.211-216
• /
• 2013

Most of hull resistance prediction methods which are used to calculate the towing force of disabled ships are very simple and old-fashioned. In particular, in cases of barge ships, a method similar to the US Navy Towing Manual is being used. This paper reviewed the US Navy Towing Manual and the notification method of Korea Ministry of Oceans and Fisheries and proved that these prediction methods are irrational and inaccurate. Furthermore, a new Modified-Yamagata-Barge method is introduced as a more rational and accurate resistance prediction method which can be applied in case of barge ships.

• Journal of the Korean Society of Marine Environment & Safety
• /
• 제20권4호
• /
• pp.405-411
• /
• 2014

It needed the calculation of the required tugboat's power to move the damaged vessel to the safe area for reducing the additional damages. In this paper, it was verified the theoretical calculation method on the required power of tugboat through the 93m real ship tests. From the experiments, it was considered that the theoretical calculation method was sufficient to estimate the required power of tugboat. The resistance of the locked propeller was relatively big portions compared with other static resistances such as air resistance, frictional resistance and residual resistance. And dynamic resistance induced by swing movement and yawing was continuously occurred and it also was great effects on the total resistance. In the future, the safety factor will be considered and the exact prediction of ship's resistance will enhance the efficiency of tugboat because of the minimization of safety factor.

• The Journal of Information Technology
• /
• 제5권4호
• /
• pp.145-154
• /
• 2002

The Extension of Base is a fundamental Method to expend the moduli in RNS(Residue Number System). RNS has the benefit of parallelism and no carry propagation at each moduli, but division , extension of base and etc. is the problem of RNS in case of the operation speed.Generally this method is applied to system using Mixed Radix Conversion. it appears to decrease the size of Arithmetic Unit, but increasing the time of operation. So in this paper, the Improved Extension of Base is proposed using Chinese Remainder Theorem. it has the comparative small size and Improved speed.

• Composites Research
• /
• 제34권3호
• /
• pp.148-154
• /
• 2021

Carbon/epoxy composite bipolar plate (BP) is a BP that is likely to replace existing graphite bipolar plate of vanadium redox flow cell (VRFB) due to its high mechanical properties and productivity. Multi-functional carbon/epoxy composite BP requires graphite coating or additional surface treatment to reduce interfacial contact resistance (ICR). However, the expanded graphite coating has the disadvantage of having low durability under VRFB operating conditions, and the surface treatments incur additional costs. In this work, an excessive resin absorption method is developed, which uniformly removes the resin rich area on the surface of the BP to expose carbon fibers by applying polyester fabric. This method not only reduces ICR by exposing carbon fibers to BP surfaces, but also forms a unique ditch pattern that can effectively hold carbon felt electrodes in place. The acidic environmental durability, mechanical properties, and gas permeability of the developed carbon/epoxy composite BP are experimentally verified.

• Journal of the Society of Naval Architects of Korea
• /
• 제57권6호
• /
• pp.312-321
• /
• 2020

In this study, machine learning techniques were applied to predict the residual resistance coefficient (Cr) of low-speed full ships. The used machine learning methods are Ridge regression, support vector regression, random forest, neural network and their ensemble model. 19 hull form variables were used as input variables for machine learning methods. The hull form variables and Cr data obtained from 139 hull forms of KRISO database were used in analysis. 80 % of the total data were used as training models and the rest as validation. Some non-linear models showed the overfitted results and the ensemble model showed better results than others.

• Journal of the Society of Naval Architects of Korea
• /
• 제59권4호
• /
• pp.243-250
• /
• 2022

In the design stage of hull forms, a fast prediction method of resistance performance is needed. In these days, large test matrix of candidate hull forms is tested using Computational Fluid Dynamics (CFD) in order to choose the best hull form before the model test. This process requires large computing times and resources. If there is a fast and reliable prediction method for hull form performance, it can be used as the first filter before applying CFD. In this paper, we suggest the offset-based performance prediction method. The hull form geometry information is applied in the form of 2D offset (non-dimensionalized by breadth and draft), and it is studied using Convolutional Neural Network (CNN) and adapted to the model test results (Residual Resistance Coefficient; C_R). Some additional variables which are not included in the offset data such as main dimensions are merged with the offset data in the process. The present model shows better performance comparing with the simple regression models.

• Journal of the Korean Society of Marine Environment & Safety
• /
• 제20권5호
• /
• pp.552-557
• /
• 2014

The objective of the This study is to access the speed performance employing the sea trial test and CFD with the our own designed and manufactured one-man boat. The overall design process including hull form design was explained. The sea trial was carried out with a manufactured boat in the clam sea. Brake power at the design speed of a boat through the sea trial was measured as 1680 W. The flow computation was conducted considering free surface and dynamic trim using a commercial CFD code(STAR-CCM+). The result of computation provided the information that residual resistance is bigger than fraction's at design speed. The total efficiency were predicted based on the sea trial and CFD. The Total efficiency was divided into shaft efficiency and quasi-propulsive efficiency. By using quasi-propulsive efficiency, it becomes possible to predict speed performance of boat in future. The results can provide information regarding hull form design, performance analysis and development of a boat in future.

• Journal of the korean academy of Pediatric Dentistry
• /
• 제30권1호
• /
• pp.124-131
• /
• 2003

The concentration of nitrous oxide in dental environment has increased especially in pediatric department. In pediatric department frequently met the behavior disordered patients who need the deep sedation. As the deeply sedated patients could not respond well to verbal command, the amount of mouth breathing would be increased especially with mouth prop which backward transposition of mandible. Inhalation of low concentration of nitrous oxide for a long duration has caused various side effects such as spontaneous abortion and inhibition of methionine synthetase activity which is harmful to DNA synthesis. For evaluation of factors of mouth breathing during deep sedation. The author measured the concentration of nitrous oxide in breathing zone by the change of the scavenging methods. One is drain the gas through the tail part of reservoir bag of Jackson Ree's system naturally. Another is scavenge from tail portion of reservoir bag with negative pressure. Last one is scavenge from nasal mask with negative pressure. The nitrous oxide concentration in breathing zone was the lowest in nasal part drainage but high above the recommended concentration of NIOSH. The order of nitrous concentration in breathing zone was: natural drainage, tail part with negative pressure, nasal part with negative pressure. This would reflect the order of resistance of nasal airway and showed the amount of mouth breathing. From the above experiment, the resistance of nasal airway by the increment of gas flow in corrugating tube and reservoir bag would be one of the causative factors of mouth breathing in deeply sedated patients.

• Proceedings of the Korean Vacuum Society Conference
• /
• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
• /
• pp.334.1-334.1
• /
• 2014

태양전지, 터치센서와 같이 투명한 전극(TCO: Transparent conducting oxide)이 필요로 하는 곳에는 금속 산화물 형태의 ITO, ZnO, FTO와 같은 투명 전극이 사용된다. 그중에서 FTO는 저렴한 가격과 높은 투과율, 낮은 저항으로 주목을 받고 있다. 뿐만아니라 FTO 박막은 다른 산화물 전도체에 비해 구부림에 강한 저항성을 보여 주고 있다. FTO 박막의 캐리어 전하 생성 원리는 F 원자가 O 원자의 자리를 치환하게 되면서 잉여 전자의 발생으로 전기가 흐를 수 있다. 아직까지는 화학적 조성비에 유리한 CVD를 이용한 증착 방법이 많이 사용되고 있다. 스퍼터 장비 역시 공정 가스에 따라 화학적 조성비 변화가 가능하고 CVD와 비교하여 공정이 간단하며 연속 공정이 쉽고 대면적 적용이 가능하다. 본 실험은 본사에서 R&D용으로 제작한 Daon-1000 S 장비를 사용하였으며 DaON-1000 S는 3개의 2" sputter gun이 장착 되어 있어 co-sputtering이 가능한 장비이다.