• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.877-887
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• 2015

Rapid development of cities with constant increasing load and deregulation in electricity market had forced the transmission lines to operate near their threshold capacity and can easily lead to voltage instability and caused system breakdown. To prevent such catastrophe from happening, accurate readings of voltage stability condition is required so that preventive equipment and operators can execute security procedures to restore system condition to normal. This paper introduced Enhanced Hybrid Particle Swarm Optimization algorithm to estimate the voltage stability condition which utilized Fast Voltage Stability Index (FVSI) to indicate how far or close is the power system network to the collapse point when the reactive load in the system increases because reactive load gives the highest impact to the stability of the system as it varies. Particle Swarm Optimization (PSO) had been combined with the ANN to form the Enhanced Hybrid PSO-ANN (EHPSO-ANN) algorithm that worked accurately as a prediction algorithm. The proposed algorithm reduced serious local minima convergence of ANN but also maintaining the fast convergence speed of PSO. The results show that the hybrid algorithm has greater prediction accuracy than those comparing algorithms. High generalization ability was found in the proposed algorithm.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.387-392
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• 2005

The research was performed to predict the potential landslide with roughness index. It was known that fractal dimension and surface area index can be represented the topography, specially when the natural slopes were rough or rugged. A test site was selected and fractal dimension and surface area index were calculated from the irregular triangle network. Fractal dimension were ranged between $2.016{\sim}2.046$ and surface area index $1.56E+07{\sim}2.59E+07$. Surface area index increased as fractal dimension increased. Slope stability was calculated by infinite slope stability analysis model and was compared to slope stability by fractal and surface area index. In the result, unsafe zones where slope stability is under 1.1 were $5.11{\sim}6.25%$ for the test site. It can be said that fractal dimension and surface area index are a good index to evaluate the slope stability because when fractal dimension and surface area index are greater, then stability of the site is more unsafe.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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• pp.427-432
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• 2016

Objective: The goal of this study was to systematically investigate the postural stability of dancers by providing unexpected perturbations. Method: Six female dancers and college students participated in this study. Unpredictable wait-pull balance perturbations in the anterior direction were provided to the participants during standing. Three different perturbation intensities (low, moderate, and high intensity) were used by increasing perturbation forces. Spatial and temporal stability of postural control were measured by using margin of stability (MoS) and time to contact (TtC), respectively. Results: Both MoS and TtC at moderate intensity were significantly greater in the dancer group than in the control group, but no significant differences were found at low and high intensities between the groups. Conclusion: The present study showed spatial and temporal stability of dynamic postural control in dancers. We found that the dancers were more spatially and temporally stable than the ordinary participants in response to unexpected external perturbation when the perturbation intensity was moderate at two extreme intensity levels (low and high).

• Journal of Korean Academy of Nursing
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• v.30 no.5
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• pp.1318-1332
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• 2000

The purpose of this study was to determine the effect of walk training on leg strength, flexibility, postural stability, balance and gait in home bound elderly women. Eighteen elderly women of the experimental group aged between 70 and 90 years image who have normal vision, hearing and Romberg test. They participated in the 12 week walk training. The subjects of the experimental group practiced walk training 3 times a week for during 12 weeks. During the 40 minute workout, the subjects practiced 5 minutes of warming-up exercises, 30 minutes of conditioning exercises and 10 minutes of a cool-down exercise. The intensity for the conditioning phase was determined by subject' heart rates, which ranged from 60% to 70% of age-adjusted maximum heart rates. The body composition, leg strength, flexibility, postural stability, balance and gait were measured prior to and after the experimental treatment. The body fat, lean body mass, leg strength (ankle dorsiflexor, plantarflexor, inversor and eversir, knee flexor, extensior), flexibility (range of motion of ankle dorsiflexion, plantarflexion, inversion and eversion), and postural stability of the experimental group were significantly greater than those of the control group. Duration of standing on the right foot and that of standing on the left foot of the experimental group was greater than that of the control group. Total balance scores of the experimental group were significantly higher than those of the control group. Among 13 items for balance, the scores of experimental group in balance with eyes closes, turning balance, sternal nudge, neck turning, one leg standing balance and back extension were higher than those of the control group. Total scores of gait of the experimental group were significantly higher than those of the control group following the walking training. Scores of experimental group in step height, step length and walk stance while walking among 9 items for gait were significantly higher than those of the control group. The results suggest that walk training can improve physical fitness for prevention in home bound elderly women.

• Wind and Structures
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• v.38 no.6
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• pp.427-443
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• 2024

By using a computational program of three-dimensional aerostatic and aerodynamic stability analysis of long-span bridges under skew wind, the dynamic characteristics and structural stability(including the aerostatic and aerodynamic stability) of a three-tower cable-stayed-suspension hybrid bridge with main span of 1 400 meters are investigated numerically under skew wind, and the skew wind and aerostatic effects on the aerostatic and aerodynamic stability of three-tower cable-stayedsuspension hybrid bridge are ascertained. The results show that the three-tower cable-stayed-suspension hybrid bridge is a longspan structure with greater flexibility, and it is more susceptible to the wind action. The aerostatic instability of three-tower cable-stayed-suspension hybrid bridges is characterized by the coupling of vertical bending and torsion of the girder, and the skew wind does not affect the aerostatic instability mode. The skew wind has positive or negative effects on the aerostatic stability of the bridge, the influence is between -5.38% and 4.64%, and in most cases, it reduces the aerostatic stability of the bridge. With the increase of wind yaw angle, the critical wind speed of aerostatic instability does not vary as the cosine rule as proposed by the skew wind decomposition method, the skew wind decomposition method may overestimate the aerostatic stability, and the maximum overestimation is 16.7%. The flutter critical wind speed fluctuates with the increase of wind yaw angle, and it may reach to the minimum value under the skew wind. The skew wind has limited effect on the aerodynamic stability of three-tower cable-stayed-suspension hybrid bridge, however the aerostatic effect significantly reduces the aerodynamic stability of the bridge under skew wind, the reduction is between 3.66% and 21.86%, with an overall average drop of 11.59%. The combined effect of skew and static winds further reduces the critical flutter wind speed, the decrease is between 7.91% and 19.37%, with an overall average decrease of 11.85%. Therefore, the effects of skew and static winds must be comprehensively considered in the aerostatic and aerodynamic stability analysis of three-tower cable-stayed-suspension hybrid bridges.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.3
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• pp.124-131
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• 2016

In this study, a physical experiment was performed to investigate the change in the stability coefficient, defined by Hudson equation, for the tetrapod of different specific densities. The experiment was carried out once (with no repetition) for a rubble mound breakwater with 1:1.5 slope. In this experiment, the stability coefficient for the high-density tetrapod was greater than that for the normal-density tetrapod. This indicates variability of the stability coefficient according to change in the density of tetrapod. Further experiments and detailed analysis are required to investigate the effect of the density on the stability coefficient of tetrapod.

• Wind and Structures
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• v.13 no.5
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• pp.471-485
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• 2010

In comparison with the common two-tower suspension bridge, due to the lack of effective longitudinal restraint of the center tower, the three-tower suspension bridge becomes a structural system with greater flexibility, and more susceptible to the wind action. By taking a three-tower suspension bridge-the Taizhou Bridge over the Yangtze River with two main spans of 1080 m as example, effects of structural parameters including the cable sag to span ratio, the side to main span ratio, the deck's dead load, the deck's bearing system, longitudinal structural form of the center tower and the cable system on the aerodynamic stability of the bridge are investigated numerically by 3D nonlinear aerodynamic stability analysis, the favorable structural system of three-tower suspension bridge with good wind stability is discussed. The results show that good aerodynamic stability can be obtained for three-tower suspension bridge as the cable sag to span ratio is assumed ranging from 1/10 to 1/11, the central buckle are provided between main cables and the deck at midpoint of main spans, the longitudinal bending stiffness of the center tower is strengthened, and the spatial cable system or double cable system is employed.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.4
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• pp.516-530
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• 1999

The current clinical technique for occlusal vertical dimension recording is based on marking the skin reference points on the patient's face and measuring between these points using caliper-like device. And it is difficult to achieve reliable measurements by this technique because of movable soft tissue. The purpose of this study is to reveal the stability of skin reference points by comparing the relative movement between extra-oral skin reference points and intra-oral reference points using X-ray fluoroscope. 10 test subjects were divided into 2 groups : Group I (natural dentition) and Group II (denture-wearer whose vertical dimension was lost) and Group III consists of identical test subjects to Group II with their upper denture removed and record base inserted. Attaching the 3 mm diameter steel ball to nose tip, lower lip, chin and to existing denture (or record base), fluoroscopic examination and recording were taken during 2 jaw opening and closing movements. After subsequent digitization using personal computer, 1219 still pictures with 0.1 second interval were made. Using the 2 dimensional graphic software, measurements between reference points were executed. Dividing the entire jaw movement into 3 ranges (total, 1st half opening, 2nd half opening), rate of movement and relative movement between extra-oral and intra-oral reference points were calculated and statistically analyzed. The results of this study are as follows. 1 Within the same experimental group, no statistical difference was found in the stability of skin reference between lower lip point and chin point during total range of jaw opening and closing movement (p>.05) 2. In the first half range of jaw opening, statistical difference was found between Group I (natural dentition) and Group II (denture wearer) (p<.05) Group I has greater skin reference stability than Group II. 3. In the first half range of jaw opening, statistical difference was found between Group I and Group III (record base wearer) (p<.05). Group I has greater skin reference stability than Group III. 4. In the first half range of jaw opening, no statistical difference was found in the stability of skin reference between Group II and Group III (p>.05). 5. In the second half range of jaw opening, no statistical difference was found in the stability of skin reference between any experimental groups (p>.05). 6. In patients with their occlusal vertical dimension lost, employing other measuring references rather than skin is recommended because of low stability.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.128-130
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• 1964

Fluorinated acid chlorides in the C$_3$ to C$_9$ range were reacted with diols prepared from terpene diacids to give good yields of potentially useful esters. These esters were shown to be of greater stability and low temperature properties than those prepared from fluorinated alcohols and corresponding terpene diacids by direct esterification.

• The Academic Congress of Korean Shoulder and Elbow Society
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• 1997.05a
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• pp.112-120
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• 1997

1) The superior labrum-biceps complex contributes to shoulder stability. 2) Injuries to the superior labrum Decrease torsional rigidity Place a greater strain on the IGHL 3) Arthroscopy enables diagnosis and treatment of superior labrum lesions.