• Journal of Integrative Natural Science
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• v.8 no.3
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• pp.221-232
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• 2015

In this study, the vertical characteristics of wind were analyzed using the horizontal wind, vertical wind, and vertical wind shear, which are generated from a wind profiler during concentrated heavy rain, and the quantitative characteristics of concentrated heavy rain were analyzed using CAPE, SWEAT, and SRH, among the stability indexes. The analysis of the horizontal wind showed that 9 cases out of 10 had a low level jet of 25 kts at altitudes lower than 1.5 km, and that the precipitation varied according to the altitude and distribution of the low-level jet. The analysis of the vertical wind showed that it ascended up to about 3 km before precipitation. The analysis of the vertical wind shear showed that it increased up to a 1 km altitude before precipitation and had a strong value near 3 km during heavy rains. In the stability index analysis, CAPE, which represents thermal buoyancy, and SRH, which represents dynamic vorticity, were used for the interpretation of the period of heavy rain. As SWEAT contains dynamic upper level wind and thermal energy, it had a high correlation coefficient with concentrated-heavy-rain analysis. Through the case studies conducted on August 12-13, 2012, it was confirmed that the interpretation of the prediction of the period of heavy rain was possible when using the intensive observation data from a wind profiler and the stability 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.

• 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.

• Structural Engineering and Mechanics
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• v.49 no.3
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• pp.311-327
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• 2014

The safety relating to leakage of water and pitch instability of ship chambers of the full balanced hoist vertical shiplifts has been the focus of adoption of the type of vertical shiplifts. This paper aims to remove the doubts through theoretical and engineering researches. The leakage and pitch stability of ship chambers of full balanced hoist vertical ship lifts are investigated on the basis of theoretical analysis and exploration of engineering measures. Regarding the issue of leakage of ship chambers, a mathematical model on leaking process is built and corresponding formula and coping measures are obtained which can be applied in control program of ship lifts by linking with monitoring. The concept of safety grade is put forward to seek the best technical and economic index and the corresponding technical measures are for different grades of ship lift is suggested. For the issue of pitch instability, a methodology of combining theoretical deduction and summary of achievements of design and operation of the type of the full balanced hoist shiplifts is adopted, and the formula for design about pitch stability of ship chambers is derived.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.135-141
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• 2018

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.168-178
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• 2022

In this study, the resistance test, the vertical static angle of the attack test and VPMM test will be conducted to estimate the maneuverability of underwater vehicles with ahead propeller. The vertical static test will be conducted within the range of -40deg to 40deg, to investigate the cross-flow drag at high incidence angles. The tests will be conducted by dividing the propeller rotation into a case in which the propeller rotates at a specific rpm, and a case in which the propeller rotates naturally, according to the towing speed. Hydrodynamic coefficients of vertical direction will be estimated by the captive model tests. Additionally, the vertical dynamic stability index based on estimated hydrodynamic coefficients will be calculated and the impact of the propeller revolution state on the index will be investigated. The results are expected to be used as reference test data for underwater vehicles with ahead propeller.

• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.85-94
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• 2015

Purpose : The purpose of this study was to investigate the influence on the ground reaction force parameters according to wearing positions of backpack for during stair ascending and descending. Methods : Participants selected as subject were consisted of young female(n=10) and performed stairs walks(ascending and descending) with 2 types of wearing position(front of trunk[FT], rear of trunk[RT]). Passive(Fz 1) and active(Fz 2) forces of the vertical GRF were determined from time function and frequency domain. Also shear forces(Fx, Fy 1, Fy 2), dynamic postural stability index(MLSI, APSI, VSI, DPSI), loading rate and center of pressure (${\Delta}COPx$, ${\Delta}COPy$, COP area) were calculated from time function and frequency domain. Results : Fx, Fy 1, Fy 2, and Fz 1 in GRF didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher forces than that of stair ascending. Particularly, Fz 2 of stair ascending showed higher forces than that of stair descending(p<.001), RT types showed higher than that of FT types(p<.05). MLSI, APSI, VSI, and DPSI of stair descending showed the increased stability index than that of stair ascending(p<.05), MLSI of RT types showed the decreased stability index than that of FT types(p<.05). Loading rate didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher loading rate than that of stair ascending(p<.001). Also, ${\Delta}COPx$ in stair descending showed the increased movement than that of stair ascending(p<.05). Conclusions : A backpack of 10 kg(10 kg(ratio of body weights $17.61{\pm}1.17%$) showed significantly change GRF parameters according to wearing positions during stair ascending and descending. If possible, we suggest that the dynamic stability, in case of stairs walking with a smaller weights can be further improved.

• The Journal of Korean Physical Therapy
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• v.33 no.6
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• pp.286-291
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• 2021

Purpose: This study aims to measure the improvement of balanced ability and rapid response of 30 healthy adults by performing dynamic stretching, static stretching, and sargent jump. Methods: The sample 30 peoples without any musculoskeletal disease who volunteered to be the subject of the study. We measured all subjects on following metrics to evaluate the function and stability under the normal condition, with dynamic stretching (DS) group, static stretching (SS) group: vertical jump height and reaching distance Anterior, Posteromedial, Posterolateral and NO (Normal eye open), NC (Normal eye close), PO (Pillow with eye open), and PC (Pillow with close eye) were evaluated. All measures were analyzed using independent t-test and One-way repeated Anova. Results: There was a significant increase in SJH (Sargent jump) in both groups (p<0.05). In Y-balance test, there was a significant increase in both groups except for the ANT (Anterior) direction, and there was a significant increase only in the SS group in the ANT (Anterior) direction (p<0.05). There was no significant difference between the DS group and the SS group (p>0.05). There was no significant improvement in ST (Stability Index) and WDI (Weight Distribution Index) in both groups (p>0.05). Conclusion: Both DS and SS showed significant improvement in SJH and Y-balance tests, which are dynamic functions, but had no significant effect on static balance ability.

• Geomechanics and Engineering
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• v.14 no.5
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• pp.439-451
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• 2018

The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

• Korean Journal of Applied Biomechanics
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• v.24 no.2
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• pp.151-160
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• 2014

The purpose of this study was to investigate the GRF(ground reaction force) parameters according to the shoes's heel heights and ground landing distances during downward stairs on bus. Participants selected as subject were consisted of young and healthy women(n=9, mean age: $21.30{\pm}0.48$ yrs, mean height: $164.00{\pm}3.05cm$, mean body mass: $55.04{\pm}4.41kg$, mean BMI: $20.47{\pm}1.76kg/m^2$, mean foot length: $238.00{\pm}5.37mm$). They were divided into 2-types of shoe's heel heights(0 cm/bare foot, 9 cm) and also were divides into downward stairs with 3 types of landing distance(20 cm, 35 cm, 50 cm). A one force-plate was used to collect the GRF(AMTI, USA) data from the sampling rate of 1000 Hz. The GRF parameters analyzed were consisted of the medial-lateral GRF, anterior-posterior GRF, vertical GRF, loading rate, Center of Pressure(${\Delta}COPx$, ${\Delta}COPy$, COP area) and Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) during downward stairs on bus. Medial-lateral GRF and vertical GRF didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 9 cm shoes heel showed higher vertical GRF than that of 0 cm bare foot in landing distance of 50 cm. Also anterior-posterior GRF didn't show significant difference statistically according to the shoe's heel heights, but landing distance of 20 cm showed higher than that of landing distances of 35 cm and 50 cm in anterior-posterior GRF. Loading rate didn't show significant difference statistically according to the landing distance, but 9 cm shoe's heel showed higher than that of 0 cm bare foot during downward stairs. The ${\Delta}COPy$ and COP area didn't show significant differences statistically according to the shoe's heel heights and landing distance, but 0 cm bare foot showed higher than that of 9 cm shoe's heel in ${\Delta}COPx$. Dynamic Postural Stability Index(MLSI, APSI, VSI, DPSI) didn't show significant differences statistically according to the landing distance, but 9 cm shoe's heel showed decreased value than that of 0 cm bare foot in dynamics balance. Considering the above, parameters of GRF showed different characteristics according to the shoe's heel heights and ground landing distances during downward stairs on bus.