• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.918-927
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• 2020

Flows induced by hybrid CRP pod propulsion systems (CRP-POD) are fundamentally characterized by unsteadiness. This work presents a numerical study on the unsteady flow of a CRP-POD at behind-hull condition based on CFD (Computational Fluid Dynamics). Unsteady RANS method is adopted, coupled with SST k-u turbulence model and sliding mesh method. The propeller thrusts and torques obtained by CFD is validated by model tests and acceptable agreements are obtained. The time histories of shingle-blade loads and pressures near the hull surface are recorded for the analysis of unsteady flow features. The cases of forward propeller alone and aft propeller alone are also computed to distinguish the hull-propeller interaction and propeller-propeller interaction. The results show the blade loads of both forward and aft propellers strongly fluctuate with phase angles. For the forward propeller, the blade load fluctuation is mainly governed by the hull-propeller interaction, while the aft blade load is remarkably affected by the propeller-propeller interaction in terms of the load average and fluctuation pattern. The fields of pressure, vorticity and velocity are also analyzed to reveal the unsteady flow features.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권1호
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• pp.6-11
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• 2015

Maintenance plays an important role in keeping product availability, reliability and quality at an appropriate level. In this paper, two-types of maintenance policies are studied following the expiration of two-dimensional (2D) free replacement warranty. Both the fixed-maintenance-period policy and the variable-maintenance-period policy are based on a specified region of the warranty defined in terms of age and usage where all failures are minimally repaired. An accelerating failure time (AFT) model is used to allow for the effect of usage rate on product degradation. The maintenance model that arises following the expiration of 2D warranty is discussed. The expected cost rates per unit time from the user's point of view are formulated and the optimal maintenance policies are determined to minimize the expected cost rate to the user. Finally numerical examples are given to illustrate the optimal maintenance polices.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.723-732
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• 2020

A theoretical calculation model for ship stern bearings with large hull deformation is established and validated theoretically and experimentally. A hull simulation model is established to calculate hull deformations corresponding to the reaction force of stern bearings under multi-factor and multi-operating conditions. The results show that in the condition of wave load, hull deformation shows randomness; the aft stern tube bearing load obeys the Gaussian distribution and its value increases significantly compared with the load under static, and the probability of aft stern tube bearing load greater than 1 is 65.7%. The influence laws and levels between hull deformation and bearing reaction force are revealed, and suggestions for ship stern bearing specifications are proffered accordingly.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.470-473
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• 2004

In the yeast Saccharomyces cerevisiae, iron can be toxic. Because of this phenomenon, its metabolism of iron is strictly regulated. We have constructed a model system in which cell growth is defected during periods of iron over-load. When $Aft1-1^{up}$ protein was overexpressed with Ga110 promoter, a galactose inducible promoter, cell growth was defected and levels of CLN2 transcript decreased. However transcript levels of AFT1 and FET3 genes increased over time in a consistent manner throughout the course of $AFT1-1^{up}$ overexpression. We have screened to find genes to suppress cell growth defect by iron overload with YEp-derived high copy yeast genomic DNA library and found that high copy of Rmelp suppressed cell growth defects. Rme1p has been known as an activator protein of CLN2 gene expression. Taking these results together, we suggest that the yeast cell cycle is arrested at the $G_1$, phase by iron overload via Cln2p.

• 한국산업정보학회논문지
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• 제29권2호
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• pp.119-131
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• 2024

2019년 금융위원회의 온라인 대출 중개 서비스 도입 허용에 따라 핀다와 토스같은 핀테크 대출중개 플랫폼들이 가파르게 성장하였다. 하지만 대출중개 플랫폼으로 대출을 받은 고객들은 기존의 모집법인을 통해 대출을 받은 고객들보다 채무불이행 위험도가 더 높은 것으로 보고되었다. 본 연구는 생존분석 기법을 통해 신용대출을 받기 위해 대출중개 플랫폼을 통해 대출을 받은 고객들과 모집법인을 통해 대출을 받은 고객들의 채무불이행 위험도를 비교하고 각 대출중개 플랫폼별로 고객들의 채무불이행에 영향을 주는 특성들을 비교하였다. 분석을 위해 국내 캐피털사의 고객 데이터를 활용하였으며 카플란-마이어 분석 및 AFT 모형을 활용하였다. 모집법인을 통해 대출을 받은 고객들에 비해 대출중개 플랫폼을 통해 대출을 받은 고객들은 개인사업자보다 일반 대출자의 비중이 높고 부동산을 소유하고 있을 확률이 높았으며 대출진행기간이 더 짧았다. 또한 대출진행기간 중앙값(385일)을 기준으로 채무불이행 발생 비율이 더 높았다. AFT 모형을 통해 채무불이행 발생 시기를 분석한 결과 대출중개 플랫폼은 모두 모집법인에 비해 채무불이행 발생 확률이 높은 것으로 나타났다. 또한 대출중개 플랫폼을 통해 대출을 받은 고객의 특성들이 채무불이행 발생 시기에 주는 영향은 플랫폼별로 상이하게 나타났다. 이 결과는 대출중개 플랫폼별로 고객의 리스크 차이를 고려한 맞춤형 전략이 필요함을 보여준다.

• 설비공학논문집
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• 제15권9호
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• pp.751-761
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• 2003

We performed the numerical analysis on the airflow characteristics in the two type of cleanroom systems, which are the axial fan type (AFT) and the fan filter unit (FFU). A computational fluid dynamic model was applied to investigate and compare the nonuniformity, the deflection angle and the air ventilation effectiveness of the two designs of cleanrooms when dampers are adjusted and not adjusted. And the flow-resistance models of the various components were used in this simulation. We know that the airflow characteristics of the cleanrooms are largely affected by damper adjusting And we also find out that the FFU system is superior to the AFT system through the comparison of the cleanroom performance indices.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.595-609
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• 2015

The wake characteristics of Contra-Rotating Propeller (CRP) were investigated using numerical simulation and flow measurement. The numerical simulation was carried out with a commercial CFD code based on a Reynolds Averaged Navier-Stokes (RANS) equations solver, and the flow measurement was performed with Stereoscopic Particle Image Velocimetry (SPIV) system. The simulation results were validated through the comparison with the experiment results measured around the leading edge of rudder to investigate the effect of propeller operation under the conditions without propeller, with forward propeller alone, and with both forward and aft propellers. The evolution of CRP wake was analyzed through velocity and vorticity contours on three transverse planes and one longitudinal plane based on CFD results. The trajectories of propeller tip vortex core in the cases with and without aft propeller were also compared, and larger wake contraction with CRP was confirmed.

• 품질경영학회지
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• 제35권1호
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• pp.136-141
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• 2007

For many products failures depend on age and usage and, in this case, failures are random points in a two-dimensional plane with the two axes representing age and usage. Models play an important role in decision-making. In this research, an accelerate failure test (AFT) model is proposed to deal with the two-dimensional data. The parameters are proposed to be estimated through maximum likelihood estimators.

• 수산해양기술연구
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• 제27권3호
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• pp.193-210
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• 1991

For the deckhouse or superstructure, attention is directed to the reduction of vibration from a human susceptibility point of view. The two basic requirements for obtaining a low vibration level in the accommodation are to ensure that excitation forces from propeller and/or main engine are small and to avoid resonance excitation of the hull and superstructure. In recent years increased attention has been directed towards the problems of vibration and noise in deckhouse, which have caused major problems with regard to the environmental quality in the living quarters for crews. Accordingly, in this paper, the characteristic of the vibration of deckhouse of fishing boat, of which the length/height ratio is also relatively high, are studied systematically with regard to the shape and modelling of deckhouse based on finite element method of 1-dimensional, 2-dimensional and 3-dimensional model. This study is divided into 4-part. 1st part is the global deckhouse vibration, 2nd part is the local deckhouse vibration, 3rd part consists of the estimation for stiffness of foundational support and 4th part is the application to TUNA LONG LINER of 416 ton class. For the global vibration analysis, the severity of the vibration depends on the longitudinal shear and bending stiffness of the deckhouse, on the vertical deckhouse support(fore, aft and sides). However, even if the design is technically sound, vibration problems may arise due to vertical or longitudinal hull girder or afterbody resonances. Author applied the method of this study to the analysis of, deep-sea fishing vessel of G.T. 416 ton class with relatively low height and long deckhouse, and investigated the vibrational characteristic of the fishing vessel with earlier structural feature. According to this investigation, the vibration, response of above vessel was confirmed of which main hull and deckhouse behave as one body. It is at the bottom of vibrational trouble which a accommodation part of the fishing vessel is raised, that is the local vibration for side wall, fore-aft wall and deck plate of deckhouse rather than thief fect of fore-aft vibration of deckhouse for above fishing vessel. and the resonance of main hull, deckhouse and driving system such as the main engine, propeller in exciting source is mainly brought up as the trouble.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.336-340
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• 2014

The noise and vibration have been evaluated by using the finite element model in the vehicle developing stage. The sound pressure of the vehicle compartment is predicted by the acoustic cavity model coupled with the body structure. In general, the structural model has been focused to study in the improvement of the noise. It is not easy to treat the structural model, instead the acoustic cavity model is relatively simple and aids in root cause analysis of vibro-acoustic issues. Therefore, the acoustic transfer function of the cavity is more efficient for finding out the main contribution parts of the vehicle booming noise. And examples about the run-up booming noise demonstrate the validity of the AFT analysis for improving the vibro-acoustic sensitivity.