• 한국경영과학회지
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• 제35권4호
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• pp.55-79
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• 2010

This study deals with a model for platform competition in a two-sided market. We suppose there are both direct and indirect network externalities between suppliers and users of each platform. Moreover, we suppose that both users and suppliers are distributed in their relative affinity for each platform type. That is, each user [supplier] has his/her own preferential position toward each platform, and users [suppliers] are horizontally differentiated over [0, 1]. And for analytical tractability, some parameters like direct and indirect network externalities are the same across the markets. Given the parameters and the pricing profile, users and suppliers conduct subscription game, where participants select the platform that gives them the highest payoffs. This game proceeds according to a replicator dynamics of the evolutionary game, which is simplified by properly defining gains from participant's strategy in the subscription game. We find that depending on the strength of these network effects, there might either be multiple stable equilibria, at which users and suppliers distribute across both platforms, or one unstable interior equilibrium corresponding to the market tipping in favor of either platform. In both cases, we also consider the pricing power of competing platform providers under the framework of the Stackelberg game. In particular, our study examines the possible effects of the type of competition between platform providers, which may constrain the equilibrium selection in the subscription game.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.441-442
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• 2006

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.713-714
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• 2007

• 대한의용생체공학회:의공학회지
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• 제28권3호
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• pp.410-416
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• 2007

This paper presents quantitative analysis of a training system based on an unstable platform and a visual interactive system for improving sense of equilibrium. The training system consists of an unstable platform, a force plate, a safety harness, a monitoring device, and a personal-computer. To confirm the effects of the training system, fifteen young volunteers and five elderly volunteers went through a series of balance training using the system. During the training, we measured relevant parameters such as the time a subject maintain his or her center of pressure on a target, the time a subject moves his or her center of pressure to the target, and the mean absolute deviation of the trace before and after training with this system and training programs to evaluate the effects of the training. The results showed that the training system can successfully assess the gradual improvement of the postural control capability of the subject in the system and showed a possibility of improving balance of the subject. Moreover, the significant improvement in the postural capability of the elderly subject suggests that elderly subjects can benefit more from the training using the system for the improvement of sense of equilibrium.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.206-210
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• 2004

This paper proposes a new training system for equilibrium sense using unstable platform. This training system for equilibrium sense consists of an unstable platform, a computer interface circuit and software program. Postural instability changes the weighting of different types of sensory information and the state of the equilibrium maintenance system. In order to improve the equilibrium sense, we developed software program such as a block game, sine curve training (SCT) and pingpong game using Visual C++. Using this system and training programs, we performed an experiment to train the equilibrium sense of a subject. To evaluate the effects of balance training, the time maintained on the target and the moving time to the target are measured. As a result, the moving time to the target and time to maintain cursor on the target improved through repeating equilibrium sense training. It was concluded that this system was reliable in the evaluation of equilibrium sense. We expect that this system might be applied to clinical use as an effective balance training system.

• 대한의용생체공학회:의공학회지
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• 제25권6호
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• pp.465-469
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• 2004

본 논문에서는 불안정판(unstable platform)을 이용한 새로운 인체 평형감각 증진용 훈련 시스템을 제안하였다. 본 시스템은 불안정판, 컴퓨터 인터페이스, 다양한 소프트웨어로 구성되어 있다. 불안정판은 기울기 센서와 무선 모듈을 내장한 타원형의 단순한 구조이다. 균형 훈련의 효과를 평가하기 위해 표적으로의 이동시간(moving time to the target)과 표적 내 유지시간(duration time in the target)과 같은 파라미터(parameter)를 측정하였다. 균형 훈련은 2주간 행해졌고, 훈련 프로그램에 따라 피험자를 두 그룹으로 나누었다. 그 결과, sine curve trace (SCT)와 block game의 훈련 프로그램을 이용한 반복적인 훈련을 통해 이동시간은 짧아졌고, 유지시간은 길어졌다 특히, 피험자가 균형을 유지하기 어려웠던 방향에서의 개선이 두드러졌다. 이로써 본 시스템은 훈련 후 피험자의 평형감각을 향상시킬 수 있었고, 효과적인 평형감각 훈련시스템으로써 임상에의 적용 가능성을 확인할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.688-698
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• 2019

If heave motion in the platform causes horizontal parametric vibration of a Compliant Vertical Access Riser (CVAR), the riser may become unstable. A combination of riser parameters lies in the unstable region aggravates vibrational damage to the riser. Change of axial tensile stress in the riser combined with its natural frequency and mode shape change results in mode coupling. In accordance with the state transition matrices of the riser in the coupled and uncoupled states, the stable and unstable regions were obtained by Floquet theory, and the vibration response under different conditions was obtained. The parametric excitation of the CVAR is shown to occur mainly in first-order unstable regions. Mode coupling may cause parametric excitation in the least stable regions. Damping reduces the extent of unstable regions to a certain extent.

• 한국안전학회지
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• 제26권3호
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• pp.47-51
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• 2011

Work platform is temporary material that many workers use in construction field, but many workers construct and use the work platform without considering safety standards, workers who have not the knowledge of safety standards construct the work platform in weakness and use the work platform in unstable, According to the statistics in 2009, 1230 people were injured at the work platform. Among them, victims by falling account for about 77% and mostly lead to fatal injuries. we have studied and survey about the safety or danger of the work platform(set limits to duble scaffold) in construction field and about how many workers observe safety standards of the work platform. According to the result of this survey, 24%~100%(average : 68%) of the work platform in survey is not observe the safety standards.

• 한국전문물리치료학회지
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• 제3권3호
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• pp.1-11
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• 1996

The purpose of this study were to evaluate and compare the balance ability at different conditions in normal 20 to 29 years old on unstable platform, KAT 2000(Breg, Inc., Vista, CA. 1994). Static and dynamic BI(balance index) were measured 3psi and 5psi surface conditions. Static tests were done on right and left leg separately, then both legs together with the feet apart 20cm with the eyes opened and closed. Dynamic tests were done on both legs together with apart 20cm with the eyes opened. A dynamic test was performed in which the subject moved platform in a circular manner to chase a moving object on a computer screen. Seventy healthy students(average 21.6 years, male, female) were tested. In this study applied the paired t-test and correlation to determine the statistical significance of result. The results were as follow: 1) The mean static balance index of the Rt leg was $119.9{\pm}75.72$ on 3psi surface condition with the eyes opened, and that of the Lt leg was $224.3{\pm}121.16$. 2) The mean static balance index of the Rt leg was $93.1{\pm}24.16$ on 5psi surface condition with the eyes opened, and that of the Lt leg was $180.5{\pm}61.76$. 3) The mean static and dynamic balance index of both legs were $76.4{\pm}31.86$, $2187.6{\pm}696.99$ on 3psi with the eyes opened, and $68.3{\pm}14.82$, $1938.7{\pm}525.41$ on 5psi respectively. 4) The mean static balance index of the Rt leg was $517.8{\pm}220.87$ on 3psi surface condition with the eyes closed, and that of the Lt leg was $588.6{\pm}204.81$. 5) The mean static balance index of the Rt leg was $271.9{\pm}192.151$ on 5psi surface condition with the eyes closed, and that of the Lt leg was $363.4{\pm}98.97$. 6) The mean static balance index of both legs was $332.6{\pm}137.31$ on 3psi surface condition with the eyes closed, and that of the 5psi was $288.5{\pm}133.07$. 7) The balance index on 3psi surface condition was significantly higher than that of 5psi (p<0.05, p<0.01). 8) The balance index with the eyes closed was significantly higher than that of the eyes opened (p<0.05). 9) The balance index on the left leg was significantly higher than that of the right leg (p<0.05, p<0.01). 10) There was no correlation between static balance index and dynamic balance index. 11) Therewas no correlation between weight or height and balance index.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.899-900
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• 2008