• 대한수학회논문집
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• 제23권3호
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• pp.371-376
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• 2008

In this paper, it is shown that if f satisfies the following functional inequality (0.1) $${\parallel}\sum\limits_{i,j=1}^3\;f{(xi,yj)}{\parallel}{\leq}{\parallel}f(x_1+x_2+x_3,\;y_1+y_2+y_3){\parallel}$$ then f is a bi-additive mapping. We moreover prove that if f satisfies the following functional inequality (0.2) $${\parallel}2\sum\limits_{j=1}^3\;f{(x_j,\;z)}+2\sum\limits_{j=1}^3\;f{(x_j,\;w)-f(\sum\limits_{j=1}^3\;xj,\;z-w)}{\parallel}{\leq}f(\sum\limits_{j=1}^3\;xj,\;z+w){\parallel}$$ then f is an additive-quadratic mapping.

• Nonlinear Functional Analysis and Applications
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• 제28권3호
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• pp.671-684
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• 2023

In this paper, we prove the generalized Hyers-Ulam stability of a general quintic functional equation, $\sum\limits_{k=0}^{6}(-1)^k{_6}C_kf(x+(3-k)y)=0$, by using the fixed point method.

• 한국전문물리치료학회지
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• 제6권3호
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• pp.11-21
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• 1999

Human balance is maintained through a complex process involving sensory detection of body motions, integration of sensorimotor information within the central nervous system, and execution of appropriate musculoskeletal responses. The basic task of balance is to position the body center of gravity (COG) over some portion of the support base. When the COG extends beyond the base of support, the person has exceeded the limits of stability (LOS). At this point, a step or stumble is required to prevent a fall. Automatic postural responses operate to keep the COG over the base of support. They are a set of functionally organized, long-loop responses that act to keep the body in a state of equilibrium. There are four commonly identified automatic postural responses, or strategies. These are ankle strategy, hip strategy, suspensory (knee) strategy, and stepping strategy. Thus, the purpose of this study was to evaluate the LOS using various knee strategies. Forty subjects participated in this study. The subjects were comprised of 20 males and 20 females who were without neurologic, orthopaedic or balance performance impairments. The LOS was measured with a Balance Performance Monitor (BPM) Dataprint Software Version 5.3. The results of this study were as follows: 1) Knee joint angle which is to increase stability of standing balance with using knee strategy was at mid-range. 2) There were statistically significant differences in anteroposterior LOSs according to the knee strategy. 3) There were no statistically significant differences in mediolateral LOSs according to the knee strategy. 4) There were statistically significant differences of anteroposterior LOSs with using knee strategy according to gender. 5) There were no statistically significant differences in mediolateral LOSs with using knee strategy according to gender.

• 충청수학회지
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• 제21권3호
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• pp.377-384
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• 2008

In this paper, we prove the stability of the functional equation $$\sum\limits_{i=0}^{3}3Ci(-1)^{3-i}f(ix+y)-3!f(x)=0$$ in the sense of P. $G{\breve{a}}vruta$ on the punctured domain. Also, we investigate the superstability of the functional equation.

• 대한수학회보
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• 제45권2호
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• pp.397-403
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• 2008

In this paper, we modify L. $C\breve{a}dariu$ and V. Radu's result for the stability of the monomial functional equation $\sum\limits_{n=0}^{n}n\;C_i(-1)^{n-i}f(ix+y)-n!f(x)=0$ in the sense of Th. M. Rassias. Also, we investigate the superstability of the monomial functional equation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.33-35
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• 1993

This paper presents a new optimal VAR planning algorithm considering voltage stability margin. The characteristic of this method is to make it possible to formulate VAR planning for the dual purpose of maintaining voltage profiles within specified limits, and increasing the voltage stability margin of anticipated operating conditions with respect to voltage collapse. The IEEE-30 bus system is used to demonstrate the capability of the proposed algorithm.

• 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.

• The Journal of Korean Physical Therapy
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• 제11권2호
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• pp.139-147
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• 1999

The purpose of this study was to evaluate and compare the limits of stability(LOS) data obtained from aged 20 to 69 years. In addition, this study was carried out to know correlation between age and LOS. 150 adults without neurosurgical and orthopedic disability from 20 to 69 years of age participared in this study. The LOS was measured at Two Feet Forceplate with BPM(Balance Performance Monitor) Dataprint Software Version 5.3. In this study applied the independent t-test, one-way ANOVA, and correlation analysis to determine the statistical significance of results at 0.05 level of significance. The results of this study were as follows: 1. The anteroposterior LOS significantly differented from 40 age group to 60 age group. 2. The mediolateral LOS significantly differencted from 50 age group to 60 age group. 3. There were statistically significant differences in anteroposterior LOS according to age increasing.

• 한국정밀공학회지
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• 제10권4호
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• pp.216-226
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• 1993

Three dimensional cutting is considered as an equivalent orthogonal cutting through the plane containing both the cutting velocity vector and the chip flow velocity vector in dynamic cutting process. An analytical expression of dynamic cutting force is obtained from the cutting parameters determined by the static cutting. Particular attention is paid to the energy supplied to the vibratory system of cutting tool with two degree of freedom. In this approach, the phase lag of the horizontal vibration of the tool behind the vertical vibration and the direction angle of the fluctuating cutting force is considered in point of stability limits. Chatter vibration can be effectively suppressed by relatively increasing the spring constant and the damping coefficient of the cutting system in the vertical cutting force direction. A good agreement is found between the stability limits predicted by theoretical value and experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.31-35
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• 2001

Three dimensional dynamic cutting can be postulated as an equivalent orthogonal dynamic cutting through the plane containing both the cutting vector and the chip flow velocity vector in cutting process. An analytical expression of dynamic cutting force is obtained from the cutting parameters determined by the static three dimensional cutting experiments. Particular attention is paid to the energy supplied to the vibration of the tool behind the vertical vibration and the direction. The phase lag of the horizontal vibration of the tool behind the vertical vibration and the direction angel of the fluctuating cutting force must be regarded in point of stability limits. Chatter vibration can effectively be suppressed by enlarging the dynamic rigidity of the cutting system in the vertical cutting force direction. A good agreement is found between the stability limits predicted by theory and the critical width of cut determined by experiments.