• 대한조선학회논문집
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• 제41권1호
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• pp.15-22
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• 2004

Twin-skeg type stern shapes are recently adopted for very large commercial ships. However it is difficult to apply a CFD system to a hull form having twin-skeg, since grid topology around a twin-skeg type stern is more complicated than that of a conventional single-screw ship, or of an open-shaft type twin-screw ship with center-skeg. In the present study a surface mesh generator and a multi-block field grid generation program have been developed for twin-skeg type stern. Furthermore, multi-block flow solvers are utilized for potential and viscous flow analysis around a twin-skeg type stern The present computational system is applied to a 15,000TEU container ship with twin-skeg to prove the applicability. Wave profiles and wake distribution are calculated using the developed flow analysis tools and the results are compared with towing tank measurements.

• 한국산업융합학회 논문집
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• 제26권3호
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• pp.401-409
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• 2023

Oscillating water column (OWC) type wave power generator system is a power generation system that uses wave energy, a sustainable and renewable energy source. Irregular cycles and wave heights act as factors that make it difficult to secure generation efficiency of the wave power generator system. Recently, research for improving power generation efficiency is being conducted by applying digital twin technology to OWC type wave energy converter system. However, digital twin using sensor data can predict erroneous performance due to uncertainty in the sensor data. Therefore, this study proposes an uncertainty analysis method for sensor data which is used in digital twin to secure the reliability of digital twin prediction results. Uncertainty quantification considering sensor data characteristics and future uncertainty information according to uncertainty propagation were derived mathematically, and confidence interval estimation was performed based on the proposed method.

• 대한조선학회논문집
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• 제49권6호
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• pp.491-497
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• 2012

A hull-form for a 32,000G/T class Ro-Pax ferry has developed in accordance with a need of ferry operators to reduce fuel oil consumption(FOC) due to the drastic increase in oil prices recently and strengthening of environmental rules and regulations such as CO2 emission. A twin-skeg type is applied as the hull-form in lieu of an open-shaft type in order to improve propulsion performance. In order to achieve this object, flow control devices are installed to reduce a propeller induced vibration which is a main reason to obstruct the application of twin-skeg type passenger vessels owing to an uncomfortable vibration level. Numerical simulation by using an in-house code and a commercial code (Fluent) has performed to find out an optimum design of the flow control devices and to check an improvement in cavity volume. Model tests in Samsung Ship Model Basin are carried out to evaluate propulsion performance with the developed twin-skeg type hull and a reference hull of open-shaft type. In conclusion, it is shown that the twin-skeg type hull is better than the open-shaft in FOC by around 7% and in cavity volume by 20% as well.

• 한국분무공학회지
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• 제8권4호
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• pp.1-8
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• 2003

The objective of this study is to investigate experimentally atomization characteristics for differently made an ultrasonic twin-fluid nozzle. A spray system, an ultrasonic system, and three different type(Nozzle type, Tube type, Conventional type)are made and tested by applied with ultrasonic energy. In this investigation, the measurement and calculation of spray droplet are to analyze the effects of ultrasonic energy on the agricultural atomization system. Through the measurement of suray angle, spray column using, high speed camera and PDA, it is found that nozzle type is highest efficiency than that of tube type and conventional type. It was found that the ultrasonic energy increased the atomization efficiency of spray droplets about 9% respectively and spray angle was wide spray.

• Applied Microscopy
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• 제44권1호
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• pp.34-39
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• 2014

Electron backscatter diffraction (EBSD) is widely used for quantitative microstructural analysis of the crystallographic nature of variety of materials such as metals, minerals, and ceramics. EBSD can provide a wide range of information on materials including grain size, grain orientation, texture, and phase identity. In the case of metallic alloys, EBSD now has become an essential technique to analyze the texture, particularly when severe deformation is applied to the alloys. In addition, EBSD can be one of the very useful tools in identification of twin, particularly in Mg alloys. In Mg alloys different type of twin can occur depending on the c/a ratio and stacking fault energy on the twinning plane. Such an occurrence of different type of twin can be most effectively analyzed using EBSD technique. In this article, the recent development of Mg alloys and occurrence of twin in Mg are reviewed. Then, recently published example for identification of tension and compression twins in AZ31 and ZX31 is introduced to explain how EBSD can be used for identification of twin in Mg.

• 한국해양공학회지
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• 제12권1호
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• pp.128-134
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• 1998

This study is carried out the theoretical studies on wave transmission and motions in waves of twin hull type floating breakwaters with the vertical and horizontal plate. The method of calculation is based on the three dimensional singularity distribution method. The results show that wave transmission is affected by heave motion. Twin hull type is designed by the use of the theoretical method and good performance of the developed floating breakwater is confirmed for longer wave period.

• 한국분무공학회지
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• 제16권1호
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• pp.27-36
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• 2011

The impact force on the single and overlap region of twin spray was experimentally evaluated using visualization method in full cone type swirl nozzle spray. Visualization of spray was conducted to obtain the spray angle and breakup process. The photography/imaging technique, based on Particle Image Velocimetry (PIV) using high-speed camera, was adopted for the direct observation of droplet motion and axial velocity measurement, respectively. Droplet size was measured by Particle Motion Analyze System (PMAS). The purpose of this study is to provide fundamental information of spray characteristics, such as impact force, for higher etching factor in the practical wet etching system. It was found that the spray angle, axial velocity and impact force were increased with increasing the nozzle pressure while droplet size decreased with increasing the nozzle pressure. Droplet size increased as the distance from nozzle tip was decreased. The impact force of twin spray in the overlap region was about 63.29, 67.02, 52.41% higher than that of single spray at 40, 50 and 60 mm of nozzle pitch, respectively. Also, the nozzle pitch was one of the important factors in the twin spray characteristics.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.445-446
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• 2012

• 한국철도학회논문집
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• 제12권5호
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• pp.800-805
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• 2009

이 연구에서는 선로구축물을 최소화 할 수 있어 도시형 자기부상철도로 적합한 LIM 방식 자기부상철도의 궤도시스템을 개발 제안하였다. 도심지에 건설될 경우 많은 사치적 비용을 초래하므로 공사기간을 단축할 수 있도록 프리캐스트 바닥판을 사용하는 상부구조 형식을 채택하였으며 바닥판 시공시 침목이 함께 설치 될 수 있는 트윈블록 침목 궤도시스템을 개발하였다. 제안한 트윈블록 침목 궤도시스템에 대해 유한요소해석과 실험을 통해 구조적 안전성을 검증하였으며 모의시공시험 및 기계연구원 시험선 시공을 통해 그 시공성을 확인하였다.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.252-259
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• 2020

Wheatgrass is a type of young grass that contains a lot of vitamins, minerals, and protein even compared to grain products produced from its mature cereal plants. In the context of product development and increasing product sales value, a study on the use of wheatgrass extract as an ingredient of fermented beverage was conducted. In this study wheatgrass used was self-grown using a tray in the Laboratory. The variation of wheatgrass extracts used was obtained from the twin-gear type extractor, slow-squeeze type extractor, and chopped wheatgrass. In the extraction process, the performances of the process: density, extract yield, processing capacity, and the rate of production, were analyzed. For another analysis, the physicochemical properties both of wheatgrass extracts and fermented beverages were also analyzed. The physicochemical properties analyzed included TSS, pH, acidity, and others content. The results of extraction performance analysis and physicochemical characteristics of wheatgrass extract planted at 10-20℃ based on this research gave the best results using the twin-gear extractor. The twin-gear type of extractor used in this study. All of these results were also in accordance with the statistical analysis conducted in this study.