• 한국HCI학회논문지
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• 제9권2호
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• pp.13-21
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• 2014

줄넘기 운동은 간단하면서도 매우 효과적인 운동 효과를 갖고 있지만, 높은 강도의 단조로운 운동 패턴으로 인해 지속적으로 운동을 시행하기 어려운 단점이 있다. 한편 줄넘기를 할 때 수반되는 운동에너지로부터 전기에너지를 생성하는 자가발전이 가능하며, 이전 연구에서 자가발전이 가능한 에너지 자립형 줄넘기로써 그 가능성을 확인한 바 있다. 본 연구에서는 에너지 자립형 줄넘기의 내부에 자체 생산된 전력으로 구동되는 초소형 임베디드 시스템을 내장하여, 줄넘기 운동 중의 가속도를 측정하고 스마트폰으로 무선 전송하도록 하였다. 스마트폰에서는 전용 앱을 통해 전송받은 가속도 데이터로부터 사용자의 점프를 감지하여 음악 줄넘기를 접목한 게임 콘텐츠와 실시간 연동할 수 있도록 하였다. 개발된 스마트 줄넘기 프로토타입은 사용자 테스트를 통해 줄넘기 운동의 지속적인 동기부여 방법으로써 유용함을 확인 할 수 있었으며, 축적된 운동 데이터를 기반으로 사용자에게 체계적인 피드백을 제공함으로써 줄넘기 운동의 효과를 보다 높일 수 있을 것으로 기대한다. 아울러 건전지 교체가 불필요한 에너지 자립 특성은 비용 절감과 더불어 사용성과 지속가능성 향상에도 크게 기여할 수 있을 것이다.

• 대한물리치료과학회지
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• 제24권1호
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• pp.29-37
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• 2017

Purpose : The purpose of this study was to examine the effect of rope-skipping exercise on body composition and basic physical fitness in healthy subjects: a randomized control trial. Method : Twenty two subjects were randomly allocated to two groups: rope-skipping group (n=11) and control group (n=11). The rope-skipping group participated in rope-skipping exercise for 30 minutes a day, three days a week for four weeks. Body composition was measured using the subjects' weight, body mass index (BMI), and waistline. Basic Physical fitness was measured flexibility and agility. Result : The rope-skipping showed significant differences in waistline and agility. The control group showed no significant differences. There were significant difference in agility between the rope-skipping and the control group. Conclusion : The rope-skipping exercise increased waistline and agility in healthy subjects. Additional research on rope-skipping exercise for improving body composition and basic physical fitness is need.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• 한국항해항만학회지
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• 제32권7호
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• pp.537-542
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• 2008

A lot of cargo accidents occurred due to insufficient securing in the case of marine transportation. If the residual tension of securing rope can be predicted, it will be very useful in the handling of cargo securing work of operators. It was confirmed in the previous study that the fluctuation tension cf securing rope by oscillation could be predicted. In this paper, in order to the prediction of residual tension of securing rope, the experiments were carried out to measure the residual tension of securing rope under the oscillation and cyclic loadings. The residual tensions of two tests were in good agreement with each other. It can be predicted through the cyclic loading test in the estimated fluctuation tension without oscillation test by ship motion simulator.

• 한국소음진동공학회논문집
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• 제24권4호
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• pp.317-323
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• 2014

This study is concerned with the free vibration analysis of an inextensible uniform rope with a spring-mass system at the tip. The rope is hanged vertically in a gravitational field. This problem is related to the free vibration of an elevator rope connected to an elevator cage. The equation of motion and the corresponding boundary conditions are derived by using the Hamilton's principle. The general solution of the governing equation of motion is expressed in terms of Bessel functions. The characteristic equation was derived by applying the boundary conditions. The characteristic values which are in fact non-dimensionalized natural frequencies were obtained numerically. The effects of mass and spring constant were investigated. The numerical results show how the tip mass and spring affect the natural frequencies of the rope.

• 한국공작기계학회논문집
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• 제14권1호
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• pp.101-107
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• 2005

The objective of this study is structural analysis and optimum shape of rope brake. The finite element model was implemented to compute the stress, strain and friction force for rope brake. The ANSYS code was used for this analysis. Structural analysis are effected by position and height of reinforcement figure. The structural safety was examined by an establishment angle of the rope brakes which made apply to housing of the most suitable shape. The optimum shape of the rope brake was decided after stress and strain results were compared and examined.

• 품질경영학회지
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• 제43권3호
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• pp.409-420
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• 2015

Purpose: This study is to estimate the life of elevator wire rope by using the accelerated degradation test with two accelerating variables of applied load and corrosion. Methods: Linear regression method is used to find the pseudo life of elevator wire rope at each combination of accelerating variables and the median life of elevator wire rope at use condition is estimated under the assumption that the life of elevator wire rope follows lognormal distribution. Results: The particular case study demonstrated that the results of the elevator wire life estimation by using the proposed method can provide the better solutions than existing methods. Conclusion: It can be economical to use accelerated degradation model for estimating the life of elevator wire rope.

• 한국안전학회지
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• 제18권4호
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• pp.35-38
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• 2003

The wire rope, one of the component of the elevator, is extremely important for the sage operation of the elevator. That is why the wire rope is replaced at a specific interval regradless of the operating conditions or the degree of damage to prevent the breakage of the wire rope. This is the waste of resources, causing economic and environmental loss. This paper has surveyed and analyzed and analyzed the status of replacing wire-rope by buildings that use elevators, in order to compare the replacement cycles of the wire rope under each operating conditions.

• 헤리티지:역사와 과학
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• 제35권
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• pp.82-99
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• 2002

This is to study about the saddle rope from Cheonmachong Tomb in Gyeongju. Saddle rope was made by leather on 5-6th century in Korea, there was excavated in 1973 but reported yet. At that time the analysis was tried about burials, but this remains was omitted. In recent times this remains is confirmed newly. This is important thing to restruction of harness. The working methods of saddle rope is not simple, but complicated-double up, sewing and double fasten with precessed leather. The saddle rope is restructed with no-decorated and simple leather line to recent times. Now, restruction of ancient saddle rope must be used by this way.

• 한국CDE학회논문집
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• 제17권5호
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• pp.324-332
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• 2012

In this paper, a method for calculating the contact force and the frictional force caused by contacts between the wire rope and the rigid body is introduced based on multibody dynamics. And the method is applied to a simulation of contacts between the wire rope and the shell plate of a block that can occur during shipbuilding. The wire rope is composed of a number of lumped masses and the wire rope segments that connect the masses. After calculating the position of interference, we inserted a contact node into the wire rope. We then derived the equations of motion of the wire rope and the rigid body using augmented formulation based on multibody dynamics taking into account the constraints between the contact node and the rigid body. Using the equations, we were able to obtain the constraint force between the contact node and the rigid body, and calculate the contact force and the frictional force, based on which the position of the contact node was corrected. Finally, we applied our results to perform simulation of contacts between the wire rope and the shell plate of a block in order to verify the efficacy of the method proposed in this paper.