• KIEE International Transactions on Power Engineering
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• v.11A no.4
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• pp.15-20
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• 2001

Power system stability is correlated with system structure, disturbances and operating conditions, and power flows on transmission lines are closely related with those conditions. This paper proposes a methodology to identify correlative power flows for power system transient and small-signal stability prediction. In transient stability sense, the Critical Clearing Time is used to select some dominant contingencies, and Transient Stability Prediction index is proposed for the quantitative comparison. For small-signal stability discusses a methodology to identify crucial transmission lines for stability prediction by introducing a sensitivity factor based on eigenvalue sensitivity technique. On-line monitoring of the selected lines enables to predict system stability in real-time. Also, a procedure to make a priority list of monitored transmission lines is proposed. The procedure is applied to a test system, and it shows capabilities of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.5
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• pp.271-278
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• 2003

Power system stability is correlated with system structure, disturbances and operating conditions, and power flows on transmission lines are closely related with those conditions. This paper proposes a methodology to identify correlative power flows for power system transient and small-signal stability prediction. In transient stability sense, the Critical Clearing Time is used to select some dominant contingencies, and Transient Stability Prediction index is proposed for the quantitative comparison. For small-signal stability, this paper discusses a methodology to identify crucial transmission lines for stability Prediction by introducing a sensitivity factor based on eigenvalue sensitivity technique. On-line monitoring of the selected lines enables to predict system stability in real-time. Also, a Procedure to make a priority list of monitored transmission lines is proposed. The procedure is applied to a test system and the KEPCO systems in the year of 2003 and it shows capabilities of the proposed method

• Journal of Auto-vehicle Safety Association
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• v.9 no.2
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• pp.26-32
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• 2017

This paper presents the lateral stability criteria for integrated chassis control. To determine the intervention timing of chassis control system, the lateral stability criteria is needed. The proposed lateral stability criteria is based on velocity-yawrate gain domain to determine whether vehicle is stable. If the yawrate gain violates the proposed criteria, the stability of the vehicle is considered as unstable. Characteristic velocity and critical velocity are employed to distinguish lateral stability criteria. The inside of the two boundaries is stable and the outside is unstable. If yawrate gain of vehicle violates the lateral stability criteria, the chassis control begin to intervene. To validate the lateral stability criteria, both computer simulations and vehicle test are conducted with respect to circular turn scenario. The proposed lateral stability criteria makes it possible to reduce intervention of chassis control system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.98-105
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• 2005

This paper presents the result of the aeroelastic stability test of the small-scaled hingeless hub system with composite paddle blades in hover and forward flight conditions. Excitation tests of hingeless hub system installed in GSRTS(General Small-scale Rotor Test System) at KARI(Korea Aerospace Research Institute) were carried out to get lead-lag damping ratio of blades with flexures as hub flexure. MBA(Moving Block Analysis) technique was used for the estimation of lead-lag damping ratio. First, blades with metal flexures, then with composite flexures of the same dynamic properties of rotor system as metal one were tested. Tests were done on the ground and in the wind tunnel according to the test conditions of hover and forward flight, respectively. Composite flexures were found to have better damping characteristics over metal ones in the non-rotating vibration test, and it was confirmed that the use of composite flexures would give observable improvement in aeroelastic stability compared to metal ones in all test conditions.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.423-433
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• 2005

For the design of spread foundation and the stability evaluation, we compared and analyzed it for theoretical, empirical bearing capacity formulas, and various settlement computation formulas, by conducting the plate bearing test at the site of A and B, which consisted of gneiss weathered soil. In addition, we considered the effective method of stability evaluation by carrying out the plate bearing test carried out on the ground consisted of weathering soil of gneiss. Consequently, it was found out that the allowablebearing capacity by the theoretical formula of Terzaghi was too excessive in comparison with the result of the plate bearing test and the Terzaghi-Peck method, which was used widely domestically in designing the spread foundation. It was more effective for a stable design. As a result of the plate bearing test carried out, on the ground consisted of weathering soil. It was found that reviewing the stability by the bearing capacity calculated with load-settlement curve. It is evaluated in a safer side than the point of view of the settlement.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.2
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• pp.160-168
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• 2003

Statement of problem : Direct denture reline resins tend to discolor during service in the oral environment by intrinsic and extrinsic factor. Purpose : This study was designed to evaluate the color stability of direct denture reline resins. Material and methods : Mild Rebaron(GC Corp., Japan), Meta Base M(Sun medical Co., Japan), Mild Rebaron LC(GC Corp., Japan) and as a control group, Vertex SC(Dentimex Zeist, Holland) were chosen for this study. Ten specimens of each direct denture reline resins were fabricated. Treatment methods designed for this study were the coffee staining test(7days) and the accelerated aging test(100hours). The color changes before and after treatment were measured by Tristimulous colorimeter(Yasuda seiki seisakusho, Ltd. Japan) and analyzed. Results All the direct denture reline resins subjected to the coffee staining test and the accelerated aging test showed noticible difference in color change. After coffee staining test, Meta Base M showed the highest color change followed by Vertex SC. Mild Rebaron LC and Mild Rebaron. There were no statistical differences between Meta Base M and Vertex SC and between Mild Rebaron LC and Mild Rebaron(p>0.05). After accelerated aging test. Mild Rebaron LC showed the highest color change followed by Vertex SC, Meta Base M and Mild Rebaron. There were no statistical differences only between Mild Rebaron and Mata Base M(p>0.05) but among the others, there were statistical differences(p<0.05). Conclusion : Within the limitation of this study, all the direct denture reline resins subjected to the extrinsic and intrinsic factors showed noticible difference in color change, and there were differences among manufacturers.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.5
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• pp.1-11
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• 2023

Due to climate change and aging of reservoirs, damage to embankment slopes is increasing. However, the safety diagnosis of the reservoir slope is mainly conducted by visual observation, and the time and economic cost are formidable to apply soil mechanical tests and slope stability analysis. Accordingly, this study presented a predicting method for the compaction and strength characteristics of the reservoir embankment soil using a portable static cone penetration test. The predicted items consisted of dry density, cohesion, and internal friction angle, which are the main factors of slope stability analysis. Portable static cone penetration tests were performed at 19 reservoir sites, and prediction equations were constructed from the correlation between penetration resistance data and test results of soil samples. The predicted dry density and strength parameters showed a correlation with test results between R² 0.40 and 0.93, and it was found to replace the test results well when used as input data for slope stability analysis (R² 0.8134 or more, RMSE 0.0320 or less). In addition, the prediction equations for the minimum safety factor of the slope were presented using the penetration resistance and gradient. As a result of comparing the predicted safety factor with the analysis results, R² 0.5125, RMSE 0.0382 in coarse-grained soil, R² 0.4182 and RMSE 0.0628 in fine-grained soil. The results of this study can be used as a way to improve the existing slope safety diagnosis method, and are expected to be used to predict the characteristics of various soils and inspect slopes.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.305-317
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• 2011

This paper presents an overview on flutter boundary prediction in tests which is principally based on a system stability measure, named Jury's stability criterion, defined in the discrete-time domain, accompanied with the use of autoregressive moving-average (AR-MA) representation of a sampled sequence of wing responses excited by continuous air turbulences. Stability parameters applicable to two-, three- and multi-mode systems, that is, the flutter margin for discrete-time systems derived from Jury's criterion are also described. Actual applications of these measures to flutter tests performed in subsonic, transonic and supersonic wind tunnels, not only stationary flutter tests but also a nonstationary one in which the dynamic pressure increased in a fixed rate, are presented. An extension of the concept of nonstationary process approach to an analysis of flutter prediction of a morphing wing for which the instability takes place during the process of structural morphing will also be mentioned. Another extension of analytical approach to a multi-mode aeroelastic system is presented, too. Comparisons between the prediction based on the digital techniques mentioned above and the traditional damping method are given. A future possible application of the system stability approach to flight test will be finally discussed.

• Journal of Aerospace System Engineering
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• v.7 no.2
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• pp.23-28
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• 2013

This is a research on the method of how to improve lateral stability for the small general aviation airplane to meet the FAR part 23 requirements. This research is based on the experience of certification flight tests of KC-100 airplane for Korea first type certification. KAS/FAR Part 23.177 is the static lateral and directional stability requirement. And, 23.177(b) requires to show the tendency to raise the low wing in steady heading side slip maneuver. However, it is very difficult for the low wing to be raised at the low speed during the steady heading side slip maneuver. So, the requirement allows not be negative at the $1.2V_{S1}$ speed and takeoff configuration. (static stability requirement requires low wing picked up at any speed except $1.2V_{S1}$ speed and takeoff configuration) In this paper, the static lateral stability requirements and the lessons & learned of KC-100 airplane certification flight test results are shown.

• Korean Journal of Child Studies
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• v.27 no.1
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• pp.153-166
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• 2006

Stability of the Korean Bayley Scale of Infant Development-II was tested in 305 infants by two measurements of varying intervals over a span of 5-36 months. Stability of K-BSID-II performance was r=.62(p<.01), r=.08(p<.18), r=.69(p<.01), r=.18(p<.01) for mental scale raw scores, mental scale index scores (MDI), psycho-motor scale raw scores and psycho-motor scale index scores(PDI), respectively. Stability was higher for the shorter test-retest interval group. Correlations between raw scores among infants with retest intervals of more than 2 years were stable on both mental and psycho-motor scales. MDI showed higher stability among high-risk infants than normal infants while PDI showed higher stability among normal infants. Testers and researchers should use both raw scores and index scores for better interpretations.