• Journal of Korean Society for Quality Management
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• v.50 no.3
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• pp.473-490
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• 2022

Purpose: The purpose of this study is to propose a new useful suggestion to monitor the stability of process by developing a stability ratio or index related to investigating how well the process is controlled or operated to the specified target. Methods: The proposed method to monitor the stability of process is building up a new measure index which is making up for the weakness of the existing index in terms of short or long term period of production. This new index is a combined one considering both stability and capability of process to the specification limits. We suppose that both process mean and process variation(or deviation) are changing on time period. Results: The results of this study are as follows: regarding the stability of process as well as capability of process, it was shown that two indices, called SI(stability index) and PI(performance index), can be expressed in two-dimensional X-Y graph simultaneously. This graph is categorized as 4 separated partitions, which are characterized by its numerical value intervals of SI and PI which are evaluated by test statistics. Conclusion: The new revised index is more robust than the existing one in investigating the stability of process in terms of short and long period of production, even in case both process mean and variation are changing.

• Korean Journal of Applied Biomechanics
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• v.20 no.1
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• pp.101-108
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• 2010

Recently, core and neuromuscular training(CNT) is emerging as a clinically relevant tool to improve neuromuscular control and to prevent sports injuries. The purpose of this study was to examine the effect of a 12 weeks CNT program on the dynamic stability after drop landing. The subjects attempted drop landing onto the force platform on single foot from a 40 cm height distance. The collected data was used to calculate the dynamic stability index. The Dynamic stability index was derived by measuring the medial-lateral stability index(MLSI), anterior-posterior stability index(APSI), and the vertical stability index(VSI). In comparison to the control group, the MLSI and APSI showed no difference, yet, it resulted in higher VSI. The results of this study suggest that CNT is worthwhile to be considered as a way to improve neuromuscular control and to prevent traumatic injuries. However, the results are taking into consideration to discuss the limitations of CNT and suggested future approaches.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.451-456
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• 2009

Through the development of phasor measurement units (PMU), various aspects of power system dynamic behavior could be monitored and diagnosed. Monitoring dynamic voltage stability has become one of the achievements we can obtain from PMUs. It is very important to select the most appropriate method for the Korea Electric Power Corporation (KEPCO) system since there are many voltage stability indices. In this paper, we propose an advanced WAVI (Wide Area Voltage Stability) that is well suited for the purposes of monitoring the dynamic voltage stability of KEPCO's PMU installation plan. The salient features of the proposed index are: i) it uses only PMU measurements without coupling with EMS data; ii) it is computationally unburdened and can be applied to real-time situations. The proposed index is applied to the KEPCO test system and the results show that it successfully predicts voltage instability through comparative studies.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.4
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• pp.532-539
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• 2009

When assailing some area, it is important to consider targeting power system. This paper describes effective method that power networks are incapacitated based on assessing TSI and VDI. For this, we compose realistic scenario and analyze the simulation results in a view of stability. The simulation results show the destruction effects when occur the contingency in the specified area. To perform this process, the simulation tool PSS/E and DSAT are used.

• East Asian Economic Review
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• v.28 no.2
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• pp.221-244
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• 2024

This study examines how the independence of monetary policy changes in situations where the interest rate differential between domestic and foreign rates inverts, utilizing the trilemma indices. For analysis, this paper uses the trilemma indices developed by Kim et al. (2017) to analyze the relationship between the monetary policy independence index and the other two trilemma indices, namely the capital account openness index and the exchange rate stability index, across 45 countries from 2002 to 2018. The analysis reveals that the trilemma's validity is contingent. In particular, no statistically significant negative correlation was found between the monetary policy independence index and exchange rate stability index during periods of interest rate differential inversion. A positive correlation emerges between exchange rate stability and the independence of monetary policy, particularly when the inverted interest rate differential exceeds a certain threshold. This situation, where the exchange rate remains stable despite low domestic interest rates, implies that the central bank is effectively managing monetary policy to appropriately respond to economic conditions, which is reflected in the monetary policy independence index.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.2
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• pp.35-45
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• 2015

PURPOSE: The aim of this study is to investigate how upper thoracic manipulation and cervical stability training affects cervical range of motion and neck disability index of patients with chronic mechanical neck pain. METHODS: 30 patients with chronic mechanical neck pain, and randomly divided into the upper thoracic manipulation and the cervical stability training group. Upper thoracic manipulation group was conducted to the upper thoracic manipulation, and cervical stability training was conducted to the cervical stability training. Intervention period was 6 weeks, and 3 sessions, each of which was run for 5~10 minutes. The subjects were measured neck range of motion before and after intervention by electro-goniometer. Neck disability index was used to measure neck disability index Korean version. RESULTS: Comparison within groups, there were significant difference in neck range of motion before and after intervention, and Neck disability index significantly reduced in the cervical stability training group. The comparison between groups, there were no significant difference in neck range of motion and neck disability index. CONCLUSION: Upper thoracic manipulation and cervical stability training to the patients with chronic neck pain was helpful to improve neck range of motion and cervical stability training was helpful to improve neck disability index.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.143-151
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• 2016

Objective: The purpose of this study was to investigate the effect of fatigue induction on ground reaction force (GRF) components, postural stability, and vertical jump performance in Taekwondo athletes. Method: Ten Taekwondo athletes (5 men, 5 women; mean age, $22.30{\pm}2.62years$; mean height, $174.21{\pm}9.20cm$; mean body weight, $67.28{\pm}12.56kg$) participated in this study. Fatigue was induced by a short period of strenuous exercise performed on a motorized treadmill. The analyzed variables included vertical jump performance, static stability (mediolateral [ML], center of pressure [COP], anteroposterior [AP] COP, ${\Delta}COPx$, ${\Delta}COPy$, and COP area), postural stability index values (ML stability index [MLSI], AP stability index [APSI], vertical stability index [VSI], dynamic postural stability index [DPSI]), and GRF components (ML force, AP force, peak vertical force [PVF], and loading rate). To analyze the variables measured in this study, PASW version 22.0 was used to calculate the mean and standard deviation, while a paired t-test was used to evaluate the pre- versus post-fatigue results. Pearson's correlation coefficients among variables were also analyzed. The statistical significance level was set at ${\alpha}$ = .05. Results: Vertical jump performance decreased significantly after the induction of fatigue, while AP COP, ${\Delta}COPx$, COP area, APSI, VSI, and DPSI increased significantly. PVF and loading rate increased significantly after the induction of fatigue, while the postural stability variables (AP COP, ${\Delta}COPy$, COP area, APSI, VSI, DPSI) were similarly correlated with GRF components (PVF, loading rate) after fatigue was achieved (r = .600, $R^2$ = 37%). Conclusion: These results suggest that the induction of fatigue can decrease postural stability and exercise performance of Taekwondo athletes during training and competition sessions.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.152-160
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• 1999

The weld quality of $CO_2$ arc welding is closely related to the arc stability. As the characteristics of the arc are excessively complex and nonlinear, it is not easy to make the arc model as mathematical form and to control the arc state to be stabilized. This paper was aimed to estimate the arc stability and to control for stabilizing the arc state in short circuit metal transfer mode of $CO_2$ arc welding. For these purposes, the behaviors of arc stability was investigated at different welding conditions using Mita's arc stability index, and the fuzzy control algorithm which uses the arc stability index as control imput and the arc voltage as control output was developed. In the control of the arc stability, the experiments of two cases were performed; the case of setting an initial welding voltage arbitrarily, the case of the step change in workpiece shape. Obtained results were as follows; Mita's arc stability index was able to be estimated qualitatively in the case of using the inverter type welding power source and the control performance for stabilizing the arc status was excellent in the case of existing step change disturbance.

• Journal of the Korean Society of Physical Medicine
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• v.6 no.1
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• pp.51-58
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• 2011

Purpose : This study was designed to identify the effects of carrying bag positions (None, left hand, right hand, left shoulder, right shoulder) on static balance. Methods : Fourteen healthy adult females participated in the this study. The exclusion criteria were orthopedic or neurologic disease, predominant left side. Measurements were performed initial effects. Results were evaluated by OSI, APSI, and MLSI in the biodex stability system. Results : There are among the three assessments (overall stability index(OSI), antero-posterior stability index (APSI), medio-lateral stability index(MLSI) significants difference for the carrying bags positions (None bag, left hand, right hand, left shoulder, right shoulder)(p<.05). The post-hoc test revealed a significant difference between none bag and both left hand and left shoulder in the OSI, APSI, MLSI (p<.05). Also, comparing the carrying positions significant difference between right hand and both left hand and left shoulder in the MLSI (p<.05). Conclusion : The results suggest that none dominant side with carrying bag improve more imbalance than none bag and right hand of dominant with carrying bag improve more balance than non dominant side. When comparing the four carrying bag conditions, right hand was more effective than another conditions in static balance.

• Journal of the Korean Society of Physical Medicine
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• v.4 no.2
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• pp.79-86
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• 2009

Purpose：The purpose of this study was to investigated the effect of stability on heel-heights of insole in healthy adults. Methods：Subjects of 39 males measured stability index of the Biodex Stability System(BSS) by wearing shoes of 2cm, 5cm insoles including bare feet. The BSS was consisted of a movable balance platform and the platform was interfaced with computer software that enables the device to serve as an assessment of balance performance. Stability index of the BSS included overall stability index(OSI), anteroposterior stability index(APSI), mediolateral stability index(MLSI). In the BSS, subjects were asked to step on to the platform of the BSS and assume a comfortable position while maintaining slight flexion in the knees, looking straight ahead. Subjects were trained for 10min for adaptation to the heel-height of insole and then they maintained double limb stance for 2min. Biodex platform set to convert Lv.8 into Lv.1 gradually. Results：There were statistically significant differences between heel-heights of insole and stability index of OSI, APSI, and MLSI(p<.05). The result of post-hoc test were as follows; 1)OSI had significant differences between bare feet and 2cm, 5cm. 2)APSI had significant differences between bare feet and 2cm, 5cm. 3)MLSI had significant differences between bare feet and 2cm, 5cm(p<.05). Conclusions：We found that the more heels of insole high, the more stability index increases. In particular, balance index of insole above 5cm more increased and we could acknowledge that the insole above 5cm more effected balance of healthy adults.