• 한국지능시스템학회논문지
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• 제23권5호
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• pp.436-443
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• 2013

본 논문에서는 중량물을 들어 올리는 작업자를 돕기 위한 와이어 구동식 권양 시스템의 제어기와 제어기 설계를 위한 작업자 모델링을 제시한다. 와이어 구동식 중량물 권양 시스템은 사람이 전체 제어루프에 포함된 인간지원시스템의 일종이다. 사람의 제어 특성 모델과 물건을 들어 올리는 작업자의 힘을 덜어주어야 하는 요구조건을 고려한 퍼지제어기 설계 방식을 제안한다. 또한 권양 초기 구간에서 중량물의 무게를 자체적으로 측정하여 구동될 수 있는 방식도 소개한다. 마지막으로 성능 검증을 위해 실험을 통하여 제어기의 무게 측정의 정확도를 분석하고 중량물을 작업자가 작은 힘으로 편하게 들어 올릴 수 있는지 그 결과를 분석한다.

• 한국안전학회지
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• 제26권1호
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• pp.58-64
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• 2011

This study evaluated the effects of the handle width(shoulder width, 1.25${\times}$shoulder width, 1.5${\times}$shoulder width), height(3 levels : knee, medium, knuckle) and horizontal angle($0^{\circ}$, $10^{\circ}$) on the pushing, lifting, and twisting strengths which were required for carrying single or two wheel barrows. Twelve healthy college students(male) participated in the experiment. In each experimental condition($3{\times}3{\times}2$=18), the subjects exerted three forces(pushing, lifting, and twisting clockwise). The experimental conditions and three forces were tested in random order, and a minimum 2 minutes of rest was provided between exertions. Results showed that the mean and maximum pushing forces showed greater values when the horizontal angle was $0^{\circ}$ than $10^{\circ}$(p=0.016). However, the three independent variables had no statistically significant effects on the lifting forces(p>0.1). The mean and maximum twisting forces increased as the handle width became larger(p<0.05). Also, there was a marginal effect of the horizontal angle(p=0.065) on the twisting force. From the results of this study, the horizontal angle of $0^{\circ}$ and the wider handle width were suggested for the design of single-wheel barrows.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.648-654
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• 2018

본 노면에 설치되어있는 맨홀의 지속적인 관리를 위해서는 맨홀의 개폐가 쉬워야 한다. 가혹한 조건하에 있는 맨홀은 틀과 커버가 고착되어 개폐가 어렵기 때문에 맨홀을 열 때 부양이 가능한 맨홀이 요구된다. 본 연구에서는 잠금식 맨홀을 부양식 맨홀로 개선하기 위한 부양 기구의 설계를 진행하였다. 잠금식 맨홀의 기구는 중앙에 위치한 볼트를 돌리면 볼트와 연결된 허브가 하강하고, 허브와 연결되어 있는 후크를 회전시키게 된다. 후크의 끝단이 맨홀 틀에 걸리도록 되어있다. 본 연구에서는 맨홀의 부양이 가능하도록 후크에 보조장치를 설치하도록 하였다. 부양 기능을 수행할 후크의 항복응력의 70%를 기준으로 약 300kg의 부양력을 지지할 수 있도록 구조를 설계하였다. 유한요소법을 이용한 구조해석을 통하여 형상 설계를 수행하였다. 우선 단순화된 2차원 모델로 1차 기초설계를 수행하고, 3차원 모델을 통하여 부착위치와 형상을 설계하였다. 설계된 형상에 대하여 구조적 문제점을 찾아보기 위하여 3D 프린팅을 통하여 축소 모델을 출력하였고, 기능이 작동함을 확인하였다. 최종적으로 가공을 통하여 부양 기구를 제작하여 기존의 잠금식 맨홀에 적용한 결과 평균 6.1 mm 정도의 부양이 가능함을 확인하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.160-176
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• 2017

The interaction of focused wave groups with a vertical wall is investigated based on the second order potential theory. The NewWave theory, which represents the most probable surface elevation under a large crest, is adopted. The analytical solutions of the surface elevation, velocity potential and wave force exerted on the vertical wall are derived, up to the second order. Then, a parametric study is made on the interaction between nonlinear focused wave groups and a vertical wall by considering the effects of angles of incidence, wave steepness, focal positions, water depth, frequency bandwidth and the peak lifting factor. Results show that the wave force on the vertical wall for obliquely-incident wave groups is larger than that for normally-incident waves. The normalized peak crest of wave forces reduces with the increase of wave steepness. With the increase of the distance of focal positions from the vertical wall, the peak crest of surface elevation, although fluctuates, decreases gradually. Both the normalized peak crest and adjacent crest and trough of wave forces become larger for shallower water depth. For focused wave groups reflected by a vertical wall, the frequency bandwidth has little effects on the peak crest of wave elevation or forces, but the adjacent crest and trough become smaller for larger frequency bandwidth. There is no significant change of the peak crest and adjacent trough of surface elevation and wave forces for variation of the peak lifting factor. However, the adjacent crest increases with the increase of the peak lifting factor.

• Journal of Ship and Ocean Technology
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• 제10권4호
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• pp.1-11
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• 2006

The finite volume based multi-block RANS code, WAVIS developed at MOERI is applied to the numerical self-propulsion test. WAVIS uses the cell-centered finite volume method for discretization of the governing equations. The realizable $k-{\epsilon}$ turbulence model with a wall function is employed for the turbulence closure. The free surface is captured with the two-phase level set method and body forces are used to model the effects of a propeller without resolving the detail blade flow. The propeller forces are obtained using an unsteady lifting surface method based on potential flow theory. The numerical procedure followed the self-propulsion model experiment based on the 1978 ITTC performance prediction method. The self-propulsion point is obtained iteratively through balancing the propeller thrust, the ship hull resistance and towing force that is correction for Reynolds number difference between the model and full scale. The unsteady lifting surface code is also iterated until the propeller induced velocity is converged in order to obtain the propeller force. The self-propulsion characteristics such as thrust deduction, wake fraction, propeller efficiency, and hull efficiency are compared with the experimental data of the practical container ship. The present paper shows that hybrid RANS and potential flow based numerical method is promising to predict the self-propulsion parameters of practical ships as a useful tool for the hull form and propeller design.

• 한국해양공학회지
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• 제23권5호
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• pp.39-44
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• 2009

The hydrostatic slipper bearing is generally used in high pressure axial piston pumps to support the load generated from two surfaces which are sliding relatively at low speed. The object of the bearing is to remove the possibility of direct contact by maintenance of an adequate oil film thickness between two metal surfaces. Because the bearing performance is influenced by the bearing deformation, it is highly dependent on the injection pressure, the bearing surface profile and so on. In this study, the deformation characteristics of a hydrostatic slipper bearing is investigated according to the injection pressure by the finite element analysis. In the analysis, the special boundary condition to take the fluid-structure interaction (FSI) into account is used on the interactive surface. The results, such as bearing deformation, stress and lifting force, obtained from the fully coupled analysis are compared with those from the single step sequential method.

• 대한조선학회논문집
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• 제47권4호
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• pp.533-542
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• 2010

For a long times it has been believed that the Magnus effect of the rotating cylinder could be utilized for the lifting devices applicable to marine practices. It has been reported that the rotating cylinder installed on upper deck of commercial vessel could play a energy saving role however the idea might be applicable in a very rare case in ship building practices. In this study special high lift rudder system equipped with the trailing edge rotor has been suggested in correspondence with the increasing requirement of greater rudder force. Through the numerical simulation it is cleared that the trailing edge rotor could play a role in enhancement of circulation and refinement of boundary layer of the rudder system. At the same time it is found out that the lift force of the rudder system without rotation of trailing edge rotor could be doubled when the circumferential velocity of the trailing edge rotor is equal to twice of the inflow velocity.

• Journal of Ship and Ocean Technology
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• 제12권2호
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• pp.41-52
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• 2008

The development of a high-lift rudder is needed because low speed full ships such as the VLCC(Very Large Crude oil Carrier) have difficulty for obtaining enough lifting force from a common rudder. The rudder of a ship is generally positioned behind the hull and propeller. Therefore, rudder design should consider the interactions between hull, propeller, and rudder. In the present study, the FLUENT code and body fitted mesh systems generated by the GRIDGEN program are adopted for the numerical simulations of flow characteristics around a rudder that is interacting with hull and propeller. Sliding mesh model(SMM) is adopted to analyze the interaction between propeller rotation and wake flow behind hull. Several numerical simulations are performed to compare the interactions such as hull-rudder, propeller-rudder, and hull-propeller-rudder. Also, we consider relationships between the interactions. The results of present numerical simulations show the variation of flow characteristics by the interaction between hull, propeller, and rudder, and these results are compared with an existing experimental result. The present study demonstrates that numerical simulations can be used effectively in the design of high-lift rudder behind low speed full ship.

• 한국산업정보학회논문지
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• 제5권2호
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• pp.1-8
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• 2000

인력물자취급(MMH)작업은 작업현장에서 육체적 상해와 요통(LBP)을 발생시키는 주요 원인 중에 하나이며 이러한 산업재해는 점점 증가하고 있는 실정이다. 특히 좋지 않은 작업환경 즉, 비탈진 경사면에 위치한 농장이나 과수원, 항만부두의 하역작업, 경사진 벌목장 작업, 광산의 막장에서의 작업은 많은 재해의 위험성을 초래하며, 신체균형의 상실은 근골격계(musculoskeletal System)의 부상을 초래하게 된다. 본 연구는 경사면에서의 들기작업시 작업자의 근육의 force information과 근피로도를 측정하기 위해 EMG 시스템을 이용하였다. 측정결과 AEMG의 경우 모든 조건에서 일반적으로 multifidus 근육에 걸리는 부하가 다른 근육에서보다 많은 것으로 나타났고, 15$^{\circ}$, 20$^{\circ}$인 경우 neck extensors의 사용이 많은 것으로 나타났다. MPF천이 결과 공통적으로 multifidus부위 근육의 천이정도가 가장 많은 것으로 나타났다. 근육별 부하(%)에 대한 결과는 deep spinal 근육인 multifidus, erectorspinae부위가 상대적으로 많은 것으로 나타났고 neck extensor부위는 근육분담이 적은 것으로 나타났다.

• 한국해양공학회지
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• 제25권6호
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• pp.86-90
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• 2011

The mining of imitated manganese noodles in 1000 m of seawater is planned for 2012. Thus, it is necessary to prepare the lifting pipes to be used for the test. Because of storage and expense constraints, flexible and economic HDPE pipe is being considered, making it necessary to test the structural safety. Material, pressure-chamber tests and finite element analysis of HDPE pipe for the 1000-m depth were performed. The tangential stiffness of HDPE was obtained through tension and three-point bending material tests and used for a structural analysis. FEA results show that the current sample pipe segment is safe for 1000 m of water pressure, and the stress result is also within the safe value. From the current results, the HDPE pipe seems to be acceptable only for the currently suggested constraints. However, more numerical and pressure tests need to be considered by applying additional physical conditions such as gravitational and hydrodynamic loads, external and internal fluid pressure, axial force induced ship motion, and heavy pump pressure to determine future usage.