• Journal of the Ergonomics Society of Korea
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• v.28 no.3
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• pp.41-47
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• 2009

The purpose of this study, during the lifting task was researching the difference and a relationship between the ground reaction force and the grip strength by change of position. After grip strength has measured in symmetry position and asymmetry position at 45cm and 75cm of height of hand, ground reaction force was measured by same attitude lifting wooden box. We analyzed the difference of grip strength and ground reaction force in each position change. The results of grip strength, the grip strength of both hand were significant difference that in study subject symmetry and asymmetry position (p<0.01). The results of symmetry lifting task, the study subjects was significant difference of the ground reaction force difference by height (p<0.05). Asymmetry lifting task was significant difference of ground reaction force difference by direction of rotation was changed (p<0.01). The result of it will rotate with non-dominant hand side of lifting tasks from height 75cm where it easily maintains a balance possibility and decreasing the load of the hand. Therefore, from the workshop in the work people, it will be between the height 75cm and non-dominant hand side of trunk rotatory direction in the lifting tasks. Future study is necessary researched about the change of grip strength when the height of the hand is higher, and the difference of the ground reaction force when the change of weight.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.3
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• pp.13-21
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• 2004

This paper deals with a theoretical and experimental method for the design of a biased asymmetric pre-swirl stator propulsion system which is an energy saving device by recovering a propeller rotational energy. In the case of slow-speed ships, the upward flow is generated along the afterbody hull form at the propeller plane. The generated upward flow cancels the rotating flow of the propeller at the starboard part while it increases at port part. The present biased asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency and the experimental results for the compound propulsion system.

• International Journal of Safety
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• v.11 no.1
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• pp.22-25
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• 2012

Scoliosis can be biomechanically described as a three dimensional deformity of the spine, with deviations from the physiologic curves in the sagittal and frontal planes, usually combined with intervertebral rotation. Various factors are suspected such as genetic defects, uneven growth of the vertebrae, hormonal effects, abnormal muscular activity, postural problems, or a mix of some of these elements, but its initial cause is known in only 15-20% cases. The screening test for diagnosing scoliosis is called the Adams Forward Bend Test. During the experiment, the subjects were asked to bend over, with arms dangling, until a curve could be observed. The Scoliometer was placed on the back of the subjects and used to measure the difference between the left and right apex of the curve in the thoracic, thoracolumbar and lumbar area. Then, the subjects were asked to perform Maximum Voluntary Contractions (MVCs) using the digital back muscle dynamometer in three different postures: (1) 0o (sagittally symmetric); (2) 30o from the mid-sagittal plane (clockwise); and (3) 30o from the mid-sagittal plane (counterclockwise). In addition to the experimental data, subject-dependent variables including Body Mass Index (BMI), percentage of body fat and muscle mass of left/right arms and legs were employed to reveal the cause of difference among three MVC conditions. All those variables were tested using statistical methods.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.32-36
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• 2003

This paper deals with a theoretical method for the design of a biased asymmetric preswirl stator propulsion system which has been used to increase efficiency by the recovery of a propeller slipstream rotational energy by the counter rotating flow of a stator. In the case of full slow-speed ship, the upward flow is generated at the propeller plane by the after body hull form. The generated upward flow cancells the rotating flow of the propeller at the starboard part while it increases at port part. A biased asymmetric preswirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency. The model tests for the designed compound propulsion system will be carried out later.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.2
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• pp.266-273
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• 1999

The maximum work capacity at various shoulder angles was estimated in terms of joint moment through maximum voluntary contraction (MVC) measurement, and the result was compared to workload computed from 3-D static lifting model (3DSSPP) based upon national institute of safety and health (NIOSH) lifting guideline (1991). The electromyography (EMG) of anterior/posterior deltoid and trapezius muscle was also recorded to study the function of individual muscle during asymmetric shoulder lifting. Psychophysical workload was measured to observe the difference from MVC or biomechanical estimation. An apparatus was constructed for the study and twenty five trials including five flexion angles and five add/abduction angles were performed isometrically. Results indicated that MVC at 30 degree of flexion was the strongest whereas MVC at 120 degree was the weakest. In case of add/abduction, MVC decreased to 77 to 89 % during add/abduction compared to the MVC at neutral position. Regarding the normalized EMG value, a substantial increase was observed at 30 and 60 degree abduction. More importantly, the shoulder moment computed from maximum permissible limit (MPL) was greater than the moment at MVC condition during 30 degree adduction. Current result can be used as a reference information for a safe workplace design to prevent the shoulder from an excessive work load in industry.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.1031-1038
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• 2002

In this paper the erection method of the Seohae Bridge starter is presented. The erection method of starter for cable stayed bridge was changed from conventional bracket supported erection to heavy lifting supported directly by stays. There was the need to reduce the erection time drastically. The cost saving was obtained as a bonus.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.2
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• pp.30-36
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• 2012

This study is aimed to show that an asymmetric load in the frontal plane leads to an increase in low back loading and fatigue in comparison with a symmetric load when workers lift an external weight by investigating previous studies and verifying the phenomenon with an experiment. Ten male subjects are required to lift and hold an given external load at 70cm height during 50sec, then the EMG amplitude and median frequency on bilateral low back muscle groups (Longissimus, Iliocostalis, and Multifidus) are recorded and analyzed. Independent variables are two-level load weight (13kg, 20kg) and three-level LCG (Center, 6.5cm to the right, and 13cm to the right), and dependent variables are EMG amplitude average, difference, and Fatigue Index (FI). Results show that load weight increases significantly amplitude average and FI, but LCG does significantly amplitude difference and FI significantly (P-value < 0.05). Also the correlation coefficient between amplitude difference and FI is over 0.99. These implies that trunk loading should be explained by not EMG amplitude but muscle fatigue aspect since the association between an external load and amplitude is linear, but the relationship between an external load and median frequency as muscle fatigue index is almost exponential.

• Journal of the Society of Naval Architects of Korea
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• v.30 no.1
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• pp.30-44
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• 1993

This paper deals with both experimental and theoretical methods for performance prediction of asymmetric stater propulsion systems which have been used for the purpose of recovery of a propeller slipstream rotational energy due to a stator located in front of the propeller. Using the developed computer code based on the lifting surface theory, theortical investigation on the interaction between the stator and the propeller is provided in order to obtain general insight on the performance characteristics of the propulsion systems in uniform and non-uniform flow. Such theoretical calculations have end agreements with model Inset results. The asymmetric stator would give an efficiency gain of about 6% to the compound propulsor system compared with the single propeller system.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.10a
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• pp.57-78
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• 2005

The vehicle routing problem (VRP) is to determine a set of feasible vehicle routes, one for each vehicle, such that each customer is visited exactly once and the total distance travelled by the vehicles is minimized. A feasible route is defined as a simple circuit including the depot such that the total demand of the customers in the route does not exceed the vehicle capacity. While there have been significant advances recently in exact solution methodology, the VRP is not a well solved problem. We find most approaches still relying on the branch and bound method. These approaches employ various methodologies to compute a lower bound on the optimal value. We introduce a new modelling approach, termed route-splitting, for the VRP that allows us to address problems whose size is beyond the current computational range of set-partitioning models. The route-splitting model splits each vehicle route into segments, and results in more tractable subproblems. Lifting much of the burden of solving combinatorially hard subproblems, the route-splitting approach puts more weight on the LP master problem, Recent breakthroughs in solving LP problems (Nemhauser, 1994) bode well for our approach. Lower bounds are computed on five symmetric VRPs with up to 199 customers, and eight asymmetric VRPs with up to 70 customers. while it is said that the exact methods developed for asymmetric instances have in general a poor performance when applied to symmetric ones (Toth and Vigo, 2002), the route splitting approach shows a competent performance of 93.5% on average in the symmetric VRPs. For the asymmetric ones, the approach comes up with lower bounds of 97.6% on average. The route-splitting model can deal with asymmetric cost matrices and non-identical vehicles. Given the ability of the route-splitting model to address a wider range of applications and its good performance on asymmetric instances, we find the model promising and valuable for further research.

• Proceedings of the ESK Conference
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• 1993.10a
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• pp.223-235
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• 1993

요통(Lowback Pain)을 유발하는 주요원인으로 알려져있는 MMH(Manual Materials Handling) 작업에 있어서 작업조건의 변화가 근육의 활동과 피로도에 미치는 영향을 평가하기 위해 4가지 서로 다른 작업조건하에서 몸통부위(Trunk)의 주요근육에 대한 EMG 파형분석을 실시 하였다. 본 연구에서의 분석대항작업은 실제 작업조건과 유사하레 설계된 120분간의 단속적인 인양(Lifting)/하역(Lowering) 작업으로서 작업중량은 작업자의 MVIS(Maximum Voluntary Isometric Strength)를 기준으로 설정되었으며, 매 10분 간격으로 EMG 측정이 이루어졌다. 작업물이 작업자의 정면에 위치한 대칭형(Symmetric) 작업의 경우 배면부(Dorsal) 근육인 천극근(Erector Spinae)과 활배근(Latissimus Dorsi)이 활동근(Active Muscle)인 것으로 나타났으며, 정중면(Medial Plane)을 중심으로 좌우측 근육이 동일한 근력을 발휘하였다. 작업물이 작업자의 한쪽 측면에 위치한 90도 비대칭형(Asymmetric) 작업의 경우 천극근과 활배근외에 작업물과 반대쪽 외사근(External Oblique)이 활동근으로 추가되었으며, 작업물과 반대쪽의 근육들이 더욱 큰 근력을 발휘하였다. 작업의 반복에 따른 근육의 피로도를 평가하기 위해 실시한 EMG 파형의 Spectral Analysis 결과, 비대칭형 작업시 작업물과 반대쪽의 천극근에서 작업시간의 경과에 따라 중위주파수(Median Power Frequency)가 저주 파수대로 천이(Lower Shift)하는 현상이 나타났으며, 일정한 작업량이라도 작업중량을 줄이고 작업 빈도를 높여서 작업할 경우에 이러한 현상이 더욱 두드러졌다. 작업시간의 경과에 따른 MVIS의 감소 현상은 작업빈도가 높고 비대칭형 작업일 때 가장 크게 나타났다. 총손실을 줄이고, 상대적 비용절감효과를 갖게할 수 있다고 하였다. 따라서 본 연구에서는 성인 여성기성복의 치수적합성을 높이기위하여 출산 후 중년에 접어 들면서 체형이 변화되는 것을 고려하여 연령을 분류하고(18세-34세, 30세-51세), 각 연령 집단에 따른 체형을 각각 3가지로 분류하였다. 이에 따라 의복 생산시의 총손실을 줄이기위한 상의, 하의생산시 필요한 부위별 최적규격치 간격을 제시하였다.적인 기능으로 보여지는 것에 좁혀서 작업능력의 연령증가 변화에 대하여다원적 평가를 하는 것이 실제적이라고 할 수 있다. 따라서 본 연구에서는 인간이 가지고 있는 다수의 기능중에서 수지교 치성과 연령증가와의 관계를 조사한다. 만약 연령증가 만으로 수지교치성을 평가 할 수 없는 경우에는 어떠한 요인이 수지기민성의 변화에 영향을 미치는가를 검토한다.t list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스템에 대한 시뮬레이션 구현과 시스템 분석의 예를 보인다._3$", chain segment, with the activation energy of carriers from the shallow trap with 0.4[eV], in he amorphous regions.의 증발산율은 우기의 기상자료를 이용하여 구한 결과 0.05 - 0.10 mm/hr 의 범위로서 이로 인한 강우손실량은 큰 의미가 없음을 알았다.재발이 나타난 3례의 환자를 제외한 9례 (75%)에서는 현재까지 재발소견을 보이지 않고 있다. 이러한 결과는 다른 보고자들과 유사한 결과를