• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1479-1482
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• 2004

LMTT (Linear Motor-based Transfer Technology) is horizontal transfer system in the maritime container terminal for the port automation. The system is driven by PMLSM (Permanent Magnetic Linear Synchronous Motor) that is consists of stator modules on the rail and shuttle car. This paper investigates the effect of the drop height of container on impact reaction force of the Impact Absorber (IA) in shuttle car for LMTT. The results of this investigation are obtained from detailed finite element analysis for various parameters, such as the spring coefficient, the drop height of container.

• Physical Therapy Rehabilitation Science
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• 제5권2호
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• pp.89-94
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• 2016

Objective: This study was aimed to compare the thickness and pennation angle of gastrocnemius through ultrasonography during the heel-drop exercise on ankle dorsiflexion angle. Design: Cross-sectional study. Methods: Nineteen normal adults in their 20s had voluntarily participated in this study. All subjects performed the ankle heel-drop exercise with ankle dorsiflexed to $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$: heel-drop exercise with ankle dorsiflexed to $0^{\circ}$ was executed on floor-level, heel-drop exercise with ankle dorsiflexed to $10^{\circ}$ on a wooden-block of 2.3 cm in height, and heel-drop exercise with ankle dorsiflexed to $20^{\circ}$ on a wooden-block of 5.5 cm in height. In each regimen, the subjects completed a session of 100 heel-drop exercises (10 repetitions${\times}$10 sets; with 30 seconds rest following each set; with 24 hours rest following each exercise). Before and immediately after each heel-drop exercise, the thickness and pennation angle of gastrocnemius were measured using an ultrasonography. Results: After the performance of the heel drop exercises with ankle dorsiflexed to $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$, the thickness of the gastrocnemius was significantly higher than pre-exercise (p<0.05), and furthermore heel-drop exercise with ankle dorsiflexed to $10^{\circ}$ was significantly higher than exercise with the ankle dorsiflexed to $0^{\circ}$ (p<0.05). However, as for the pennation angle of the gastrocnemius, there were no significant changes after each heel-drop exercise. Conclusions: This finding suggest that the heel-drop exercise with ankle dorsiflexed to $0^{\circ}$, $10^{\circ}$, and $20^{\circ}$ is effective on the strengthening of the gastrocnemius. Furthermore, the heel-drop exercise with the ankle dorsiflexed to $10^{\circ}$ is more effective than with the ankle dorsiflexed to $0^{\circ}$.

• Geomechanics and Engineering
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• 제30권6호
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• pp.539-549
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• 2022

Accidental anchor drop can cause disturbances to seabed materials and pose significant threats to the safety and serviceability of submarine structures such as pipelines. In this study, a series of anchor drop tests was carried out to investigate the penetration mechanism of a Hall anchor in sand and clay. A special anchor drop apparatus was designed to model the inflight drop of a Hall anchor. Results indicate that Coriolis acceleration was the primary cause of large horizontal offsets in sand, and earth gravity had negligible impact on the lateral movement of dropped anchors. The indued final horizontal offset was shown to increase with the elevated drop height of an anchor, and the existence of water can slow down the landing velocity of an anchor. It is also observed that water conditions had a significant effect on the influence zone caused by anchors. The vertical influence depth was over 5 m, and the influence radius was more than 3 m if the anchor had a drop height of 25 m in dry sand. In comparison, the vertical influence depth and radius reduced to less than 3 m and 2 m, respectively, when the anchor was released from 10 m height and fell into the seabed with a water depth of 15 m. It is also found that the dynamically penetrating anchors could significantly influence the earth pressure in clay. There is a non-linear increase in the measured penetration depth with kinematic energy, and the resulted maximum earth pressure increased dramatically with an increase in kinematic energy. Results from centrifuge model tests in this study provide useful insights into the penetration mechanism of a dropped anchor, which provides valuable data for design and planning of future submarine structures.

• 대한물리의학회지
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• 제13권3호
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• pp.133-139
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• 2018

PURPOSE: Despite the abundant literature available regarding the activity of intrinsic muscles, few studies have investigated the muscle activity of extrinsic muscles. Therefore, the present study compared the muscle activity of the peroneus longus, tibialis anterior, and abductor hallucis during short foot exercise in subjects with and without flat feet. METHODS: Twelve subjects with and without pes planus participated in this study. During the short foot exercises, muscular activity of the tibialis anterior, fibularis longus, and abductor hallucis longus were measured in both groups. To identify the effects of short foot exercises, navicular drop height was also investigated in pre and post short foot exercises. RESULTS: In a symptomatic group, the navicular drop height was significantly reduced at post measurement compared with pre-measurement. During the short foot exercise, the pes planus group showed significantly lower activities of the fibularis longus than the control group (p<.05). CONCLUSION: Similar to previous studies and clinical literature, short foot exercise was effective for alleviating navicular drop for a population with pes planus. In addition, subjects with pes planus showed decreased muscular activities of the fibularis longus, which suggests that considering extrinsic muscles such as fibularis longus is also important for rehabilitation of pes planus patients.

• 한국의류학회지
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• 제24권3호
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• pp.335-344
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• 2000

The purpose of this study was to set up sizing system for knit trainning wears. Sample size was 198 females and their age range was from 15 to 24 years old. The body types for sizing system for knit trainning wears were divided by height and drop values. The results were as follows. 1. The height could be divided into three groups and they covered 97.5%. The Short(152cm) covered 27.8%, the Regular(160cm) 51.0% and the Tall(168cm) 18.7%. 2. The Medium hip(drop value 6) and the Large hip(drop value 12)had the high coverage rate of 45.5% and 46%, and the Small hip(drop value 0) had the low coverage rate of 8.6%. 3. For sizing system for knit trainning wears, the intervals of bust girth and hip girth were 5cm and 4cm. In the same size of bust girth, the intervals of hip high girth and waist girth were 1cm, the intervals of back waist length and sleeve length were 2cm and the interval of slacks length was 4∼5cm according to three height groups.

• Water Engineering Research
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• 제5권4호
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• pp.195-206
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• 2004

This paper deals with oxygen transfer by air entrainment and energy dissipations by flow characteristics at the stepped drop structure. Nappe flow occurred at low flow rates and for relatively large step height. Dominant flow features included an air pocket, a free-falling nappe impact and a subsequent hydraulic jump on the downstream step. Most energy was dissipated by nappe impact and in the downstream hydraulic jump. Skimming flow occurred at larger flow rates with formation of recirculating vortices between the main flow and the step comers. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number. It was more related to the flow discharge than to the Froude number. Energy dissipations in both cases of nappe flow and skimming flow were proportional to the step height and were inversely proportional to the overflow depth, and were not proportional to the step slope. The stepped drop structure was found to be efficient for water treatment associated with substantial air entrainment and for energy dissipation.

• 설비공학논문집
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• 제7권2호
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• pp.276-286
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• 1995

In this study, pressure drop and heat transfer coefficients were measured in tubes with three dimensional roughness. Dimples were made by rotating the saw-tooth shaped finning disc on the outer tube surface. Resultant dimple shape was oval. Friction and heat transfer tests were performed with a range of roughness variables-roughness height 'e', axial roughness pitch 'p', circumferential roughness pitch 'z'. Within the test range, tube with e=0.5mm, z=5mm, p=3mm performed best. The efficiency ratio(rati of the heat transfer improvement and the pressure drop increase) of the tube approached 1.0 at low Reynolds number, and it was higher than that of the two-dimensional roughess tube of the same roughness height. Test data were predicted by 'discrete element method'. Results show that discrete element method underpredicts the friction data by 2% to 32%, and overpredicts the heat transfer data by-12% to 113%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.865-868
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• 2002

This study investigated the shape deformation of ball projectile(5.56mn) under the low energy impact by the use of the drop weight impact tester. ball projectile(5.56mm) consisted of the copper face with a lead core. The impact conditions were changed with the variations of the mass and the drop height of the impact tup. Shape deformation of ball projectile(5.56mm) after low velocity impact was measured using a video microscope and CCD camera. The test result showed that impact energy by changing of drop height of the impact tup affected shape deformation of ball projectile(5.56mm). So, it is important to study the relativity between shape deformation of ball projectile(5.56mm) and ballistic protection of plate(such as hybrid composite laminates) under the high velocity impact.

• 한국방재안전학회논문집
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• 제14권1호
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• pp.1-8
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• 2021

주름관은 자체의 신축성으로 변형에 의한 파손에 대응하고 설비의 편리성으로 인해 소방장비, 스프링클러 배관 등에 널리 사용된다. 그러나 벽의 주름진 형상으로 인해 복잡한 내부 난류유동이 발생하게 되며, 파이프 유동에 중요한 설계인자인 압력강하의 예측이 어렵다. 주름관 내의 압력강하에는 그루브 높이, 길이, 피치 등 파이프 벽의 형상 인자가 영향을 준다. 기존의 연구에는 관 내의 사각형 그루브의 피치(P)와 높이(K)의 비가 5 보다 작은 D형관의 경우에 대하여 길이 변화에 따른 압력 강하에 관하여 연구한 사례가 있다. 본 연구에서는 길이와 높이 변화를 고려한 P/K가 2.8, 3.5, 4.67의 경우 유동의 Re 수가 55,000, 70,000, 85,000인 경우에 대해 압력강하에 대한 수치해석 연구를 수행하였고, 주름관 내의 압력강하는 P/K 가 작을수록 감소하는 것으로 해석되어 압력 강하가 그루브 가로 세로 비율의 변화에 영향을 받고, 그루브 높이가 증가하면 재순환 면적이 증가하기 때문에 영향을 받는다는 것을 보여주었으며, 레이놀즈 수가 클수록 압력 강하가 증가하는 결과를 얻었다.

• 한국농공학회논문집
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• 제56권3호
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• pp.39-45
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• 2014

Dust is mostly caused by human activity. The effect of natural factors on dust emission were studied in many research, but the little effort in researching artificial factors of dust emission. The object of study is to analysis dust emission characteristic by drop impact. Particle matter $10{\mu}m$ ($PM_{10}$) was measured by drop impact on paved soil with changing drop height, weight and drop size. Increasing drop height cause more $PM_{10}$ emission. Increasing drop weight cause more $PM_{10}$ emission but had limit weight for increasing dust emission. Because the exceed kinetic energy of drop weight penetrate the soil surface. The limit perimeter was exist that separating $PM_{10}$ emission aspect. Under limit perimeter, $PM_{10}$ emission was increasing while perimeter was increasing, but over limit perimeter showed the opposite aspect. Regression equations for estimating $PM_{10}$ with kinetic energy and perimeter were made under limit perimeter and over limit perimeter. The $R^2$ of those equations were 0.784, 0.743. The error has occurred between measured $PM_{10}$ and calculated $PM_{10}$ in the equation under limit perimeter. But using equation of case for over limit perimeter, PM10 can be estimated with kinetic energy and drop perimeter.