• 대한인간공학회지
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• 제26권2호
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• pp.35-44
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• 2007

Work-related musculoskeletal disorders (WMSDs) are a major problem in industries in which manual materials handling is performed by workers. To prevent these WMSDs, it is necessary to understand the muscular strength capability and use this knowledge to design job and selection and assignment of workers. Even though two-hands lifting activity of manual materials handling tasks are prevalent at the industrial site, many manual materials handling tasks which require the worker to perform one-hand lifting are also very common at the industrial site and forestry and farming. However, a few researches have been done for one-hand lifting activity of manual materials handling tasks. The objective of this study is to compare one-hand and two-hands lifting strength in terms of static and dynamic strength of the lifting activity for the ranging from the height of knuckle to elbow. It is shown in this study that the isometric lifting strength of one-hand is ranging from 54.7 to 63.3% of the one of two-hands. However, it is found that there is no significant difference between a person's isometric lifting strength for left-hand and right-hand. It is also shown that there is no significant difference between the peak force under the dynamic sub-maximal loading with one-hand and two-hands lifting activity. Similar results were obtained for the peak acceleration and peak velocity under the dynamic sub-maximal loading with one-hand and two-hands lifting activity. Isometric lifting strength at the height of knuckle was ranging from 2 to 3 times of the dynamic peak force during sub-maximal lifting. It is concluded that the dynamic peak forces under the sub-maximal loading are not highly correlated with the isometric lifting strength in similar postures.

• 한국산학기술학회논문지
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• 제16권6호
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• pp.3680-3684
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• 2015

조선소에서 데크 크레인은 지상에 설치된 타워 크레인이나 해상 크레인을 사용하여 리프팅 설치 방법에 의해 선박에 탑재된다. 데크 크레인의 두 점 리프팅 설치 작업 시에는 임시 고정 지그 등을 사용하는데, 안전한 리프팅 작업을 위해서는 고정 지그의 형상 및 설치 위치를 고려한 리프팅 안전성 평가가 선행되어야 한다. 본 연구에서는 데크 크레인 및 고정 지그에 해당하는 유한요소해석 모델을 각각 생성하고, 리프팅 반력 및 경계 조건을 적용한 구조 해석을 수행하여 리프팅 설치 작업에 대한 안전성을 평가하였다. 본 연구에서 제시한 안전성 평가 방법은 다양한 데크 크레인의 리프팅 설치 작업 시에 보다 안전한 리프팅 작업 가이드를 제공할 수 있는 해석적 툴로 활용될 수 있다.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.183-192
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• 2004

본 논문에서는 수직으로 시추된 해양 파일에 대한 새로운 동적 해석절차가 제안되고 전형적 설계문제에 의하여 검증된다. 해수에 잠긴 파일의 구조는 물론 해양파도와 조류에 의한 힘도 유한요소법에 의해서 정식화되고 모델링된다. 유한요소 방정식에 적합한 파력을 구하기 위해서 여러 가지 파도이론 가운데서도 Airy의 파도이론이 시험되고 선정되었다. 조류의 후방와류에 기인한 횡방향 양력은 Strouhal 진동수와 적절한 양력계수를 가진 간단한 조화함수에 기초한다 파일에 대한 고유진동수 해석과 주파수 응답해석은 정식화 결과를 NASTRAN에 입력하여 계산되었다. 여기서 제안된 절차에 의해 얻어진 동적 변위와 응력의 결과는 기본설계해석 단계로서 해양파일의 파력과 조류 양력에 의한 동적거동을 구할 수 있으며 설계에 응용될 수 있음을 보여준다

• 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.

• 한국해양공학회지
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• 제25권4호
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• pp.1-6
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• 2011

The installation of a topside structure can be categorized into the following stages: start, pre-lifting, lifting, lifted, rotating, positioning, lowering, mating, and end of installation. The transfer of the module onto the floating spar hull occurs in the last three stages, from lowering to the end. The coupled multi-body motions are calculated in both calm water and in irregular waves with a significant wave height (1.52m). The effects of the hydrodynamic interactions between the heavy lifting vessel and the spar hull during the lowering and mating stages are considered. The internal forces caused by the load transfer and ballasting are derived for the mating phases. The results of the internal forces for the calm water condition are compared with those in the irregular sea condition. Although the effect of the pitch motion on the relative vertical motion between the deck of the floating structure and the topside module is significant in the mating phases, the internal force induced pitch motion is too small to have this influence. However, the effect of the internal force on the wave-induced heave responses in the mating phases is noticeable in the irregular sea condition because transfer mass-induced draught changes for the floating structure are observed to have higher amplitudes than the external force induced responses. The impacts of the module on the spar hull in the mating phase are investigated.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1374-1378
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• 2005

Appropriate upward force is crucial for the pantograph on high speed train to collect current from the catenery system without separation. However, at high speed, large aerodynamic lifting force is generated by the contact plate and the arms of pantograph, which may cause wear of the contact wire. In this study, to confirm the interface performance of the pantograph on Korea High Speed Train, a method to measure the contact force of the pantograph was proposed and the related measurement system was developed. The forces acting on the pantograph were clarified and a procedure to calculate the aerodynamic lifting force was proposed. A special device was invented and applied to measure the lifting force. Measured contact forces were displayed by the developed system and evaluated according to the criteria. Countermeasures were also taken to reduce the contact force based on the results.

• 턱관절균형의학회지
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• 제1권1호
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• pp.13-18
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• 2011

Objectives: We investigated muscle force from the upper limb lifting resistance test to conform the objectivity in manual muscle test. Methods: We made standard method in upper limb lifting resistance test to compare with experiment method switching the lower limb position left & right. And resistance forces of upper limb of subject were checked to inspector with closing eyes. Results: 1. The lifting resistance of right upper limb was stronger when the lower limb of right and left were abducted. 2. The lifting resistance of right upper limb was weaken when the lower limb of right and left were adducted. 3. The lifting resistance of right upper limb was weaken when the lower limb of right and left were elevated. Conclusions: As the above results, the deltoid muscle force checked in the upper limb lifting resistance test is affected by the location of lower limbs, it suggested that the muscle force of some part in the body will be affected by the other parts. It will be useful to understand the symmetry principle of body in muscle function.

• Korean Journal of Acupuncture
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• 제35권3호
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• pp.149-158
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• 2018

Objectives : In this study, we quantitatively evaluated the needle forces using needle insertion-measurement system and compared the needle sensation of each acupuncture practical model. Methods : After inserting acupuncture with a sensor to six models, a lifting-thrusting motion was implemented using the needle insertion-measurement system. The needle force was measured repeatedly, and the measurement was analyzed based on the modified Karnopp friction model for a comparison of friction coefficients. After the insertion, practitioners did lifting-thrusting manipulations. They quantified the similarity of needle sensation with VAS (Visual Analogue Scale). Results : When friction force and coefficients of friction in five different models were compared with a porcine shank model, all five models were significantly different from a porcine shank model, cotton and apple showing the closest frictional values to that of a porcine shank model. In the Cp and Cn values of cotton and in the Cp values of IM injection pad, there was no statistically significant difference. The similarity of the needle sensation between the porcine shank and five models was the highest in the apple, and overlapping papers was the lowest. Conclusions : This study quantitatively compared the physical forces in the practical model when implementing lifting-thrusting manipulations, using a needle insertion-measurement system. We suggest that a reproducible exercise model that reflects the characteristics of various human tissues, such as viscoelasticity or strength, needs to be further developed. This will contribute to establishing standardized acupuncture practice training.

• 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.

• 농업과학연구
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• 제43권3호
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• pp.450-458
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• 2016

High performance small and mid-sized tractors are required for dryland and orchard operations. A power transmission system is the most important issue for the design of high performance tractors. Many operations, such as loading and lifting, use hydraulic power. In the present study, a hydraulic power transmission system for the 3-point hitch of a 50 kW narrow tractor was developed and its performance was evaluated. First, major components were designed based on target design parameters. Target operations were spraying, weeding, and transportation. Main design parameters were determined through mathematical calculation and computer simulation. The capacity of the hydraulic cylinder was calculated taking the lifting force required for the weight of the implements into consideration. Then, a prototype was fabricated. Major components were the lifting valve, hydraulic cylinder, and 3-point hitch. Finally, performance was evaluated through laboratory tests. Tests were conducted using load weights, lift arm sensor, and lift arm height from the ground. Test results showed that the lifting force was in the range of 23.5 - 29.4 kN. This force was greater than lifting forces of competing foreign tractors by 3.9 - 4.9 kN. These results satisfied the design target value of 20.6 kN, determined by survey of advanced foreign products. The prototype will be commercialized after revision based on various field tests. Improvement of reliability should be also achieved.