• 대한조선학회논문집
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• 제28권2호
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• pp.28-39
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• 1991

조파저항과 마찰저항이 최소가 되는 선수형상을 구하기 위한 최적화문제에 관한 연구를 수행하였다. 선미부는 기존선형으로 고정하며 선수부만의 offsets을 설계변수로 하였다. 구하고자 하는 최적선형을 기존선형과 이에 대한 미소변화량으로 나누어 조파저항계산시 기존선형에는 Neumann-Kelvin 이론을 적용하고 미소변화량에는 thin ship 이론을 적용하였으며 마찰저항은 ITTC 1957 모형선-실선 상관곡선을 이용하였다. 선체표면을 모양함수(shape function)를 이용하여 근사시켰고, 이로부터 목적함수인 조파저항과 마찰저항은 offsets에 대한 2차식 형태로 표현되므로 선형구속조건을 적용하면 2차계획(quadratic programing)문제를 세울 수 있으며 complementary pivot method를 이용하여 해를 구하였다. 대상선형은 Series 60 $C_{B}$=0.6이고 Fn=0.289에서 최적화하였으며, 적절한 구속조건을 주어서 현실적인 최적선수형상을 구하고자 하였다. 본 방법으로 구한 최적선형은 thin ship 이론만을 이용하여 구한 선형과 비교할 때 설계속도 Fn=0.289에서 약간의 조파저항성능 개선(1.92%)를 가져왔다.

• 대한조선학회논문집
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• 제53권1호
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• pp.76-83
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• 2016

The various model tests are carried out to estimate and verify a ship performance in the design stage. But in view of the cost, the model test should be applied to every project vessel is very inefficient. Therefore, other methods of predicting the maneuverability with confined data are required at the initial design stage. The purpose of this study is to estimate the hydrodynamic derivatives by using the multiple regression analysis and PMM test data. The characteristics of the stern shape which has an important effect on the maneuverability are applied to the regression analysis in this study. The correlation analysis is performed to select the proper hull form coefficients and stern shape factors used as the variables in the regression analysis. The comparative analysis of estimate results and model test results is conducted on two ships to investigate the effectiveness of the maneuvering hydrodynamic derivatives estimation applied the stern shape. Through the present study, it is verified that the estimation using the stern shape factors as the variables are valid when the stern shape factors are located in the center of the database.

• 한국지능시스템학회논문지
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• 제17권2호
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• pp.154-159
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• 2007

프로펠러 회전면에서의 반류분포는 주로 모형시험에 의해서 규명되어 왔다. 이렇게 축적된 데이터베이스를 통해 선박의 기하학적 형상정보와 반류분포 사이의 입출력관계를 모델링할 수 있다면 선박 초기설계시 유사선종의 설계에 도움이 된다. 뉴로퍼지시스템은 예측, 분류, 진단 등의 매우 복잡한 문제를 해결하는 기법으로 다양한 공학분야에서 응용되고 있다. 본 연구에서는 이들 입출력 사이의 관계를 뉴로퍼지시스템으로 모델링하고 학습한 후 새로운 입력에 대한 출력값의 검토를 통해 그 유용성을 확인한다. 3차원 선미형상을 입력으로 하고 선체 모형시험으로 얻어진 프로펠러 회전면에서의 반류분포 값을 출력으로 사용하여 학습 및 추론을 해 보았다. 이를 통해 뉴로퍼지시스템을 초기 선박설계 단계에서 특히 선미형상을 결정할 때 유용한 것을 확인하였다.

• 대한간호학회지
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• 제23권4호
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• pp.678-693
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• 1993

The purposes of this study were to describe the level of vision and hearing impairments, depression and functional capacity, among Korean institutionalized elderly and to examine the relation-ship between sensory impairments, depression, and functional capacity in these people. The final pupose was to test the cognitive function path model using sensory competencies as predictors. A convenience sample of thirty nine male and 90 female subjects with a mean age of 80.5 were the subjects of this study. The subjects were tested for cognitive function, and vision and hearing impairments. Physical function and social function were measured by observation of designated task performance by the subjects. Their level of de-pression was measured using a Geriatric Depression Scale administered through an interview. Individual subjective ratings of hearing and vision were marked by the subjects, on a ladder scale. The results of the study showed that 48.8% of the subjects had a hearing impairment, 63.5% had a vision impairement, and 36.4% had both a vision and hearing impairement. The four sensory groups (no sensory impairement, hearing impairement, vision impairement, hearing and vision impairement) were tested for differences in depression, physical function, social behavior and cognitive function. The only significant difference that was found was in cognitive function, between the no sensory impairement group and the hearing and vision impairement group(F=3.25, P<.05), Subjective ratings of hearing showed a significant correlation with cognitive function(r=.34, p<.001) and with social behavior(r=.31, p<.001). There was no correlation between subjective vision ratings and cognitive function or social behavior. However there was a significant correlation between vision and hearing(r=.49, p<.001). There was also a significant negative correlation between age and vision(r=-.21, p<.01) and between age and hear-ing(r=-.34, p<.001). There was a significant correlation between depression and physical function (r=-.32, p<.001) but there was no correlation between depression and cognitive function or social behavior. Based on the literature review and the result, this study, a path model of sensory competence-> cognitive function- >social behavior was developed and tested : Perceived vision and perceived hearing were the exogenous variahles and cognitive function and social behavior were the endogeneous variables in the model. The path analysis result demonstrated an accept-able fit (GFI=.997, AGFI=.972, X$^2$=.72 (p=.396), RMSR=.019) between the data and the model. There was a significant direct effect($\beta$=.38) of perceived hearing on cognitive function. There was a significant direct effect ($\beta$=.32) of cognitive function on social behavior. The total effect of hearing on social behavior was $\beta$=.32 including the indirect effect ($\beta$=.12) . However perceived vsion had little effect ($\beta$=-.08) on cognitive function. The result of path analysis confirms that hearing levels influence cognitive function, and both hearing and cognitive function levels influence social behavior. However, vision has little effect on cognitive function or on social behavior. For the next study, a combined model of the pre viously developed environment - >depression- > physical and social function model, and the present cognitive function model, should be tested to further refine the functional capacity model. There also a need for longitudinal study of functional capacity and sencory competence in order to better understand how declining sensory competence influences functional capacity and how it effects in-creasing dependency and nursing needs in the elderly.

• 한국항해항만학회지
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• 제33권3호
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• pp.181-191
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• 2009

일반적으로 상선에서 해상운송 사고의 주된 원인은 원의 인적과실로 고려되고 있다. 본 논문에서는 선박에 승선 중인 선장, 1항사, 2항사 및 3항사를 포함하는 갑판사관들이 야기할 수 있는 사고 위기를 평가하기 위한 인적과실 모델(HEM)의 구축기법에 관해서 기술했다. 연구범위는 130척의 선박을 관리하는 회사에 소속된 542명의 갑판사관들을 대상으로 했다. 우선, 갑판사관들의 인적 데이터에 대한 통계적 분석과 전문가에 의한 브레인스토밍 과정을 통해서 KEM을 구축하고, 인적과실을 평가하기 위한 인적요소들의 변수 $\upsilon$와 $\upsilon$에 대한 평가등급 EP($\upsilon$) 및 가중치 $\alpha$, 갑판사관의 직책별 가중치 $\beta$ 등을 결정했다. 그리고 선박의 사고기록에 대한 통계분석 결과, 인적과실에 의한 사고원인 비율 ${\gamma}_H$와 외적과실에 의한 사고원인 비율 ${\gamma}_B$은 0.517(51.7%)과 0.483(48.3%)로 나타났다. $\upsilon$의 상관계수는 95%(p < 0.05) 신뢰구간에서 유의함을 확인하였고, 각 갑판사관의 위기수준 RL의 정규 확률분포 분석으로부터 HEM의 타당성을 검토했다.

• 한국전산유체공학회지
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• 제21권4호
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• pp.78-84
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• 2016

In this paper, turbulence models for considering roughness in the open source code(OpenFOAM) was investigated. Wall function in the RANS(Reynolds-averaged Navier - Stokes) turbulence model was modified considering roughness on the flat plate by using roughness function. Correlation between the first layer height in the CFD model and roughness height of the plate was observed, and the most proper roughness function, and the first layer height from the plate wall in the CFD analysis was suggested in this paper.

• 한국항만경제학회지
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• 제36권2호
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• pp.109-124
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• 2020

본 연구는 2015년 1월부터 2019년 12월까지의 건화물선 시장의 운임과 선가에 대한 패널 자료로부터 해운경기변동 특성을 분석한다. 분석은 두 가지 측면의 학술적 기여를 목표로 한다. 첫째, 기존연구가 전반적인 해운경기지표와 선박가격 지표를 대상으로 하는 반면 본 연구는 선종별로 세분화한 자료를 대상으로 해운경기지표와 선박 수급에 의한 가격변화의 관계를 분석한다. 둘째, 인과성 검정을 위한 VAR 모형을 계수에 대한 제약이 가능한 다차원 혼합 패널(heterogeneous mixed panel)모형으로 확장한다. 무엇보다도 패널 데이터 분석에서 주로 제기되는 계열상관 문제를 붓스트랩(bootstrap) 추정으로 제거하고 불안정한 자료에 대한 차분에 의한 정보손실 문제를 해결하여 추정한 정점이 존재한다. 해운시장에서 경기변동 요인과 선가 간의 인과관계에 대한 추정결과는 운임의 선가에 대한 영향이 1% 수준에서 통계적으로 유의한 것으로 나타났으나, 선박의 수급변화로 발생하는 선가의 변화가 해운경기에 미치는 영향은 존재하지 않는 것으로 드러났다. 이는 선박수급변화(선가변화)와 해운경기변화(운임변화) 간의 양방향(bilateral)의 인과관계보다는 해운경기변화(운임변화)의 선박수급변화(선가변화)에 대한 일방향(unilateral)의 인관관계가 존재함을 나타내는 실증분석 결과다.

• 대한조선학회지
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• 제12권2호
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• pp.59-66
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• 1975

Recently, as the dimensions of energy carriers increase, especially in draft, a reliable prediction of the ship motions at finite depths of water becomes necessary. The purpose of this paper is to probe the effect of finite water depth on the hydrodynamic forces and ship motions, particularly heave and pitch, in longitudinal regular head waves, by comparing the experimental value of Freakes and Keay with the author's theoretical value obtained by applying the modified strip theory to the Mariner class ship. It is confirmed that generally the hydrodynamic coefficients in the equations of motion increase with decreasing water depth, and the wave exciting forces and moments decrease with decreasing water depth. Amplitudes of heave and pitch in longitudinal regular head waves decrease as the water depth in the range where the length of the incident wave is comparatively long. The effects of Froude Number on the hydrodynamic coefficients increase with decreasing water depth and is more noticeable in the case of heave than pitch. In heave, generally the discrepancy between the experimental value and the theoretical value is relatively small in the case of $F_n=O$, but it is very large in the case of $F_n=0.2$. It is considered that the trend stems from the ignorance of the three dimensional effect and the other effects due to shallowness of water on the hydrodynamic coefficients in the theoretical calculation. An extension of methods for calculating the two dimensional hydrodynamic forces to included the effect of forward speed should be recommended. It is required that more experimental works in finite water depths will be carried out for correlation studies between the theoretical calculation, according tp modified strip theory, and model experiments.

• 한국음향학회지
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• 제38권3호
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• pp.328-333
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• 2019

본 논문은 선박 추진기의 캐비테이션 침식현상을 연구하기 위하여 추진기에서 발생하는 소음과 캐비테이션 격렬도의 연관성에 대하여 분석하였다. 캐비테이션 침식은 캐비테이션 붕괴의 빈도와 강도로 정의 할 수 있는 '캐비테이션 격렬도'와 밀접히 연관되어 있다. 캐비테이션 붕괴에 의해서 발생하는 압력파는 다양한 진폭과 지속시간의 연속적인 펄스의 형태로 나타나며 이를 캐비테이션 거동과 동조 분석하여 캐비테이션 붕괴에 따른 추진기 소음 연관성을 파악하였다. 이 기법을 경사축 추진기시험을 활용하여 추진기침식시험에 대한 정량적 평가방안을 제시하였다.

• 수산해양기술연구
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• 제60권1호
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• pp.57-70
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• 2024

In order to present a predictive drift model, Jeju National University's training ship was tested for about 11 hours and 40 minutes, and 81 samples that selected one of the entire samples at ten-minute intervals were subjected to regression analysis after verifying outliers and influence points. In the outlier and influence point analysis, although there is a part where the wind direction exceeds 1 in the DFBETAS (difference in Betas) value, the CV (cumulative variable) value is 6%, close to 1. Therefore, it was judged that there would be no problem in conducting multiple regression analyses on samples. The standard regression coefficient showed how much current and wind affect the dependent variable. It showed that current speed and direction were the most important variables for drift speed and direction, with values of 47.1% and 58.1%, respectively. The analysis showed that the statistical values indicated the fit of the model at the significance level of 0.05 for multiple regression analysis. The multiple correlation coefficients indicating the degree of influence on the dependent variable were 83.2% and 89.0%, respectively. The determination of coefficients were 69.3% and 79.3%, and the adjusted determination of coefficients were 67.6% and 78.3%, respectively. In this study, a more quantitative prediction model will be presented because it is performed after identifying outliers and influence points of sample data before multiple regression analysis. Therefore, many studies will be active in the future by combining them.