• 한국전문물리치료학회지
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• 제19권3호
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• pp.61-71
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• 2012

In daily activities, people often perform two or more tasks simultaneously. This is referred to as dual-tasking or multi-tasking. The purpose of this study was to examine the effects of performing dual tasks while using a mobile phone on static and dynamic postural stability. Twenty-four subjects were asked to stand on a force plate and then instructed to perform a balance task only (BT), a balance task while listening to music (BTL), a balance task while talking on the mobile phone (BTT), and a balance task while sending text messages (BTS). We used the BioRescue$^{(R)}$ to measure postural sway and limit of stability for static and dynamic postural stability. Also the star excursion balance test (SEBT) was used to measure dynamic postural stability. A one-way ANOVA with repeated measures was used to compare the effects of the BT, BTL, BTT, and BTS. The Bonferroni's post hoc test was used to determine the differences among four tasks. Carrying out the BTS significantly decreased the limit of stability compared with carrying out the BT, BTL, and BTT (p<.05). In limit of stability, total surface area of BTT was more significantly decreased than that of BT and total surface area of BTS was more decreased than that of BT, BTL and BTT (p<.05). In the SEBT, the BTS displayed significantly smaller reach distance values compared with the BT or BTL (p<.05). These findings suggest that performing the balance task while sending text message on the mobile phone decreases dynamic postural stability, whereas performing the same task while listening to music using the mobile phone does not. Therefore, it requires more attention to maintain dynamic balance while sending text messages.

• 대한물리의학회지
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• 제12권1호
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• pp.67-74
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• 2017

PURPOSE: The purpose of this study was to determine the effect of action observation with observation type on the limits of stability and dynamic gait ability in stroke patients. METHODS: The 20 stroke patients who participated in this study were randomly divided into two experimental groups who underwent training three times a week for 4 weeks. Their balance was tested as the limit of stability with Biorescue. Their Dynamic gait ability was tested with the Dynamic Gait Index (DGI) before the intervention, and after 4 weeks. Independent and paired t-tests were used to analyze the results. RESULTS: The results confirmed the limit of stability on the moving areas of the paralyzed and non-paralyzed sides. The limit of stability and dynamic gait index measurements confirmed that the moving area showed a significant difference after the intervention in the whole movement observation group (p<.05), but the partial movement observation group showed no significant difference (p>.05). A significant difference was also noted for the comparison between the both groups after the interventions (p<.05). The functional walking ability showed a significant difference when compared to the ability before the intervention, as determined by the changes in scores obtained for the dynamic gait index (p<.05). CONCLUSION: Interventions utilizing whole movement confirm that training improves stability and functional walking ability in stroke patients with disabilities in balance and walking ability.

• 대한기계학회논문집
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• 제19권6호
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• pp.1469-1478
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• 1995

PWM control is a kind of nonlinear control. The merits of PWM control of hydraulic equipment are the robustness of the high speed on-off valve and its low price. And it is easily implemented to hydraulic equipments with microcomputer. The high speed on-off valve is directly digitally controlled without any D/A converter. The objectives of this study is to analyze the limit cycle which regularly appear in the position control system using high speed on-off valve, and to give a criterion for the stability of this system. To do this, the nonlinear characteristics of PWM and cylinder friction of this system are described by harmonic linearization and the effects of parameter variations to the system stability are examined theoretically and experimentally. Consequently, the availability of the proposed method is confirmed well.

• Structural Engineering and Mechanics
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• 제41권3호
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• pp.339-348
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• 2012

The slope stability analysis is usually done using the methods of calculation to rupture. The problem lies in determining the critical failure surface and the corresponding factor of safety (FOS). To evaluate the slope stability by a method of limit equilibrium, there are linear and nonlinear methods. The linear methods are direct methods of calculation of FOS but nonlinear methods require an iterative process. The nonlinear simplified Bishop method's is popular because it can quickly calculate FOS for different slopes. This paper concerns the use of inverse analysis by genetic algorithm (GA) to find out the factor of safety for the slopes using the Bishop simplified method. The analysis is formulated to solve the nonlinear equilibrium equation and find the critical failure surface and the corresponding safety factor. The results obtained by this approach compared with those available in literature illustrate the effectiveness of this inverse method.

• Geomechanics and Engineering
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• 제6권6호
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• pp.545-560
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• 2014

For slope stability analysis, an alternative to the classical limit equilibrium method (LEM) of slices is the shear strength reduction method (SRM), which can be integrated into finite element analysis or finite difference analysis. Recently, probabilistic analysis of earth slopes has been very attractive because it is capable to take the soil uncertainty into account. However, the SRM is less commonly extended to probabilistic framework compared to a variety of probabilistic LEM analysis of earth slopes. To overcome some limitations that hinder the development of probabilistic SRM stability analysis, a new procedure based on recursive algorithm FORM with sensitivity analysis in the space of original variables is proposed. It can be used to deal with correlated non-normal variables subjected to implicit limit state surface. Using the proposed approach, a probabilistic finite element analysis of the stability of an existing earth dam is carried out in this paper.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.167-174
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• 2000

Profiles of discontinuities through scanline method were investigated for the analysis of rock slope stability. Lower hemispheric projection method was used to evaluate the geometric stability and failure potential of these discontinuities. Also, safety factor was evaluated for the discontinuities of failure potential using by limit equilibrium analysis. Then, displacements of rock block due to the discontinuities were displayed by using the program UDEC(Universal Distinct Element Code) which applied the Distinct Element Method. When we determine the cut-slope in design, the characteristics of discontinuities is not represented only by strength parameters of intact rock. Therefore it is more reasonable method in assuring stability that first, construction would be preceded by the cut-slope of preliminary design, and then, cut-slope would be redetermined by elaborate site investigation in processing construction.

• 한국지반공학회논문집
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• 제20권8호
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• pp.97-102
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• 2004

본 논문은 기존의 한계 평형법 보다 사면의 파괴거동을 잘 묘사할 수 있는 유한요소법에 의한 사면의 안전율을 결정하는 방법에 대하여 기술하였다. 특히, 지하수위를 고려하는 사면의 파괴거동을 강도감소법에 의한 유한요소법으로 산정하였다. 그 결과, 강도 감소법을 이용한 FEM해석방법이 사면의 안정해석에 대하여 파괴거동과 안전율을 구하는데 유효한 수단임을 보여 주었다. 그리고 지하수 상승경우와 지하수 급강하 사면의 경우에 대하여 자세히 분석하였으며, 한계평형법인 Bishop간편법 해석결과와 비교, 검토하였다.

• Geomechanics and Engineering
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• 제13권2호
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• pp.237-254
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• 2017

Estimation of slope stability is a very important task in geotechnical engineering. However, its estimation using conventional and soft computing methods has several drawbacks. Use of conventional limit equilibrium methods for the evaluation of slope stability is very tedious and time consuming, while the use of soft computing approaches like Artificial Neural Networks and Fuzzy Logic are black box approaches. Multiple Regression (MR) analysis provides an alternative to conventional and soft computing methods, for the evaluation of slope stability. MR models provide a simplified equation, which can be used to calculate critical factor of safety of slopes without adopting any iterative procedure, thereby reducing the time and complexity involved in the evaluation of slope stability. In the present study, a multiple regression model has been developed and tested its accuracy in the estimation of slope stability using real field data. Here, two separate multiple regression models have been developed for dry and wet slopes. Further, the accuracy of these developed models have been compared and validated with respect to conventional limit equilibrium methods in terms of Mean Square Error (MSE) & Coefficient of determination ($R^2$). As the developed MR models here are not based on any region specific data and covers wide range of parametric variations, they can be directly applied to any real slopes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.507-507
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• 2000

In this paper, a kind of limit cycle of an inverted pendulum system is discussed. We propose a stabilization control law for such a limit cycle of an inverted pendulum system that the pendulum rotates periodically. Besides, the stabilization control law is extended so as to ensure not only stability of the limit cycle but also an L$_2$-gain disturbance attenuation in the presence of modeling error and viscosity friction.

• 대한수학회논문집
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• 제37권4호
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• pp.1249-1258
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• 2022

In this study, we show that the strong exponential limit shadowing property (SELmSP, for short), which has been recently introduced, exists on a neighborhood of a hyperbolic set of a diffeomorphism. We also prove that Ω-stable diffeomorphisms and 𝓛-hyperbolic homeomorphisms have this type of shadowing property. By giving examples, it is shown that this type of shadowing is different from the other shadowings, and the chain transitivity and chain mixing are not necessary for it. Furthermore, we extend this type of shadowing property to positively expansive maps with the shadowing property.