• Wind and Structures
• /
• v.35 no.5
• /
• pp.337-351
• /
• 2022

As central-slotted box decks usually have excellent flutter performance, studies on this type of deck mostly focus on the vortex-induced vibration (VIV) control. Yet with the increasing span lengths, cable-supported bridges may have critical wind speeds of wind-induced static instability lower than that of the flutter. This is especially likely for bridges with a central-slotted box deck. As a result, the overall aerodynamic performance of such a bridge will depend on its wind-induced static stability. Taking a 1400 m-main-span cable-stayed bridge as an example, this study investigates the influence of a series of deck shape parameters on both static and flutter instabilities. Some crucial shape parameters, like the height ratio of wind fairing and the angle of the inner-lower web, show opposite influences on the two kinds of instabilities. The aerodynamic shape optimization conducted for both static and flutter instabilities on the deck based on parameter-sensitivity studies raises the static critical wind speed by about 10%, and the overall critical wind speed by about 8%. Effective VIV countermeasures for this type of bridge deck have also been proposed.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.2
• /
• pp.137-147
• /
• 2015

Hypersonic vehicles exhibit distinct dynamic and static characteristics, such as unstable dynamics, strict altitude angle limitation, large control bandwidth, and unconventional system sensitivity. In this study, compromise relations between the dynamic features and static performances for hypersonic vehicles are investigated. A compromise optimal design for hypersonic vehicles is discussed. A parametric model for analyzing the dynamic and static characteristics is established, and then the optimal performance indices are provided according to the different design goals. A compromise optimization method to balance the dynamic and static characteristics is also discussed. The feasibility of this method for hypersonic vehicles is demonstrated.

• KIEE International Transactions on Power Engineering
• /
• v.4A no.3
• /
• pp.141-145
• /
• 2004

FACTS devices, such as the Thyristor Controlled Series Compensator (TCSC) and Static Var Compensators (SVC), can help increase system load margin to improve static voltage stability. In power systems, because of the high cost and the effect value, the optimal placement for FACTS devices must be determined. This paper investigates the use of the series device (SVC) and the parallel device (TCSC) from the point of load margin to increase voltage stability. It considers the sensitivity of load margin to the line reactance and eigenvector of the collapse. The study has been carried out on the IEEE 14 Bus Test System to verify the validity and efficiency of the method. It reveals that incorporation of FACTS devices significantly enhance load margin as well as system stability.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.325-327
• /
• 1997

TFT2DS was developed to provide the usability as an analytic and design tool. The static characteristics of a-Si TFTs demonstrated a good agreement between simulated and measured data. This paper shows that WDS can optimize the physical parameters of a-Si through sensitivity simulations and compute the static characteristics of a-Si TFTs.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.708-710
• /
• 2003

This paper presents design sensitivity analysis for the electromagnetic force and torque obtained from Coulomb's virtual work method using the adjoint variable method. And virtual displacement field is calculated from a static structural analysis. Derived equations are verified by comparison with finite different method. And topology optimization for a c-core is given as a verification example.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.9
• /
• pp.1314-1319
• /
• 2004

In this study, parameter optimization of micro-static mixer with a cantilever beam was accomplished for maximizing the mixing efficiency by using successive response surface approximations. Variables were chosen as the length of cantilever beam and the angle between horizontal and the cantilever beam. Sequential approximate optimization method was used to deal with both highly nonlinear and non-smooth characteristics of flow field in a micro-static mixer. Shape optimization problem of a micro-static mixer can be divided into a series of simple subproblems. Approximation to solve the subproblems was performed by response surface approximation, which does not require the sensitivity analysis. To verify the reliability of approximated objective function and the accuracy of it, ANOVA analysis and variables selection method were implemented, respectively. It was verified that successive response surface approximation worked very well and the mixing efficiency was improved very much comparing with the initial shape of a micro-static mixer.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2001.10a
• /
• pp.250-254
• /
• 2001

The resolution of analog sensor is determined by its sensitivity and amplitude of noise. This paper presents modeling of inductive gap sensor base on equivalent magnetic circuit and analysis of sensitivity. We can simulate static characteristic of inductive gap sensor using this model. Computer simulation show that sensor's sensitivity is affected by magnetic flux's leakage and fringing, and that they are affected by shape of sensor probe. Base on this, we designed shape of inductive position sensor probe.

• Journal of Welding and Joining
• /
• v.16 no.4
• /
• pp.73-82
• /
• 1998

This paper is especially concerned with the weldment between support beam and square bar that plays important roles in control box of Expansion Joint as a brdige structure. Fatigue strength ({TEX}$$\sigma$_{ult}${/TEX}) of the weldment is dependent on notch factor ({TEX}$K_{f}${/TEX}) become important factors to predict fatigue life. The fatigue notch sensitivity (η) for metals can be divided into two types ; high and low notch sensitivity. In this work, the Expansion Joint weldment was found to have low notch sensitivity. The maximum strain distribution during static loading is similar to the FEM analysis. Fatigue test of real structure was performed up to {TEX}$10^{6}${/TEX} cycles to be compared with predicted endurance limit.

• Journal of Convergence for Information Technology
• /
• v.9 no.9
• /
• pp.78-86
• /
• 2019

In the study, the moral sensitivity, moral distress, and biomedical ethics awareness levels of hospital nurses are examined, and the mediating effect of biomedical ethics awareness in the relationship between moral sensitivity and moral distress is verified. As the study subjects, 153 hospital nurses were selected from both university hospitals and general hospitals in S city and J city. Using the SPSS WIN 21.0 system, data analysis was conducted via t-tests, the Sheffe test, correlation analysis, multiple regression analyses, Sobel test. The average level of moral sensitivity experienced by the hospital nurses was 4.70(out of 7), moral distress was 62.80(out of 336), and biomedical ethics awareness was 2.21(out of 4). Moral distress had a static correlation with moral sensitivity and biochemical ethics awareness, and moral sensitivity had a static correlation with biomedical ethics awareness. Finally, biomedical ethics awareness showed a partial mediating effect in the relationship between moral sensitivity and moral distress. It is important to develop a biomedical ethics education program that can help hospital nurses to resolve moral issues, thereby improving moral sensitivity and diminishing their moral distress.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.4
• /
• pp.47-56
• /
• 2005

In GPS/INS/barometer navigation system for UAV, vertical channel damping loop was introduced to suppress divergence of the vertical axis error of INS, which could be reduced to the level of accuracy of pressure altitude measured by a pitot-static tube. Because static pressure measured by the pitot-static tube depends on the speed and attitude of the vehicle, static pressure error models, based on aerodynamic data from wind tunnel test, CFD analysis, and flight test, were applied to reduce the error of pressure altitude. Through flight tests and sensitivity analyses, the error model using the ratio of differential pressure and static pressure turned out to be superior to the model using only differential pressure, especially in case of high altitude flight. Both models were proposed to compensate the effect of vehicle speed change and used differential and static pressure which could be obtained directly from the output of pressure transducer.