• Proceedings of the KSME Conference
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• 2007.05a
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• pp.566-571
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• 2007

In this study, it is investigated the thermal post-buckling characteristics of step-formed FG panel under the heat and supersonic flow. Material properties are assumed to be temperature dependent as well as continuously varying in the thickness direction of the panel according to a simple power law distribution in terms of the volume fraction of the constituent. First-order shear deformation theory(FSDT) of plate is applied to model the panel, and the von Karman strain-displacement relations are adopted to consider the geometric nonlinearity due to large deformation. Also, the first-order piston theory is used to model the supersonic aerodynamic load acting on a panel. Numerical results are summarized to reveal the thermal post-buckling behaviors of FG panels with various volume fractions, temperature conditions and aerodynamic pressures in detail.

• Journal of KSNVE
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• v.9 no.4
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• pp.785-794
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• 1999

The panel contribution analysis to reduce interior booming noise of a passenger car is carried out using both experimental method and numerical one. The accelerations of panels are measured on the outer surface of car body during operation. The acoustic characteristic of cavity is represented by two different ways. One is the acoustic transfer function obtained by experiment with reciprocal manner. The other is the boundary element model and numerical results of the model are calculated using SYSNOISE. The results from numerical method show more good agreement with measured sound pressure levels than the experimental one. Contributions of panels for interior noise are ranked and structure of the car is reinforced according to the results, which shows that the panel contribution analysis is a powerful tool to lessen structure-borne noise of passenger vehicle.

• Journal of Korean Association for Spatial Structures
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• v.6 no.2 s.20
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• pp.85-92
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• 2006

Precast large panel structures have various connection system such as the horizontal slab-to-wall connection, the vertical wall to wall connection, horizontal slab-to-slab connection, etc. Horizontal connection is connected by vertical tie bars, and vertical joint is connected loop bars and shear keys. The basic function is equalized deformations on later forces and the entire wall panel assembly acts as monolithic actions. Under lateral load some slip occurs in almost vertical connections. The shape and detail of precast connections are very important to the monolithic behavior of overall structures. The paper is a study on the design method and new elasto-plastic analysis of the connections by rigid-bodies spring model.

• Structural Engineering and Mechanics
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• v.82 no.6
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• pp.691-699
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• 2022

This paper is devoted to the presentation of a numerical study on vibration behavior of composite panels reinforced by glass fibres and carbon nanotubes (CNTs) subjected to thermal environments. The effect of temperature variation has been included as thermal load acting on in-plane direction of the panel. To model the composite material, a micromechanical model which contains random dispersion of nanotubes and single-direction fibers has been selected. The geometry of the panel has been considered to have a single curveture along its width. Based on the above assumptions, the governing equations have been derived by using thin shell theory capturing the panel curveture and also nonlinear deflections. Finally, the panel dependence on various factors such as the curveture, nanotube amount, fiber volume, fiber direction and temperature variation has been researched.

• Asia-Pacific Journal of Business
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• v.15 no.2
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• pp.207-222
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• 2024

Purpose - This study investigates whether the lagged price difference ratio between preferred and common stocks is related to the return and closing price of the preferred stock using three panel models. Design/methodology/approach - As a first step, we use a two-way fixed effect panel model with stationary preferred stock returns as a dependent variable. For robustness, we then apply the autoregressive distributed lag model (ARDL) and error correction model (ECM) with nonstationary closing prices of the preferred stocks as a dependent variable and compare the results of each model. The ARDL and ECM models provide an advantage of estimating a long-run equilibrium equation together if a long-run relationship exists between the two time-series variables compared to the fixed effect model. Findings - Our sample consists of 107 preferred stocks with at least four years of daily observations as of the end of December 2023. The coefficients of the error correction terms in the ARDL and ECM models are highly statistically significant, approximately -0.08. This indicates that the disequilibrium between the closing prices of common and preferred stocks adjusts by about 8% per day toward equilibrium. In all three models, the price difference ratio on day t-1 was statistically significant in explaining the preferred stock returns or closing prices on day t, implying that trading based on the previous day's price difference ratio is effective for one day. Research implications or Originality - Furthermore, the returns on preferred stocks are higher for firms with a lower proportion of foreign investors or a lower foreign market capitalization of preferred stocks. This suggests that foreign investors with informational advantages do not actively engage in profit-taking by trading preferred stocks, thus not narrowing the price difference. In summary, the recent surge in preferred stock prices is likely driven mainly by the irrational behavior of retail investors.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.356-363
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• 2016

Purpose: The purpose of this study is to propose efficiency of equipment testing the luminance degradation of OLED. Methods: The degradation model of Exponential model and Stretched exponential model is analyzed by goodness of fit test using calculated R-square. The degradation model having the higher R-square is finally selected. Scale parameter and Shape parameter using the selected degradation model is estimated. The activation energy and current density n using peck model among the accelerated model is estimated. the estimated parameters are analyzed by t-test. Results: The results of t-test show that the estimated parameters on chamber and hotplate are equal statistically. we can know the similarity of the luminance degradation rate and degradation pattern on chamber and hotplate. Conclusion: The result of the degradation test on chamber and hotplate is similar. when the accelerated degradation test on the panel of the OLED TV is performed, hotplate is requiring less samples, time and cost than chamber. so the accelerated degradation test on the panel of the OLED TV using the hoplate is efficient of time and cost.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.131-134
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• 2001

The three-dimensional precision measurement technology for industry product of middle and/or large scale has been developed. Theodolite measurement system which is one of the technology is widely used in aerospace industry. This paper describes measurement method and results for spacecraft structure test model by using the measurement system. And structural stability for STM is desribed through the comparison between design values and measured values.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.2
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• pp.1-13
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• 2022

Agrivoltaic facility is the composite system that the solar panel is installed above the farmland, and it enables crop and electricity production simultaneously. Solar panels of the agrivoltaic facilities can block and reduce the amount of solar irradiance arriving at the farmland, but it can help the crop growth by preventing excessive solar irradiance. Therefore, to clarify how the agrivoltaic facilities affect the crop growth, precise solar irradiance distribution under the solar panel should be modeled. In this study, PAR (photosynthetically active radiation), radiation from 400 to 700 nm, which crops usually use to grow, was extracted from the total irradiance and its distribution model under various conditions was developed. Monthly irradiance distributions varied because the elevation of the sun was changed over time, which made the position changed that the local maximum and minimum irradiance appear. The higher panel height did not cause any significant difference in the amount of irradiance reaching below the solar panel, but its distribution became more uniform. Furthermore, the panel angles with the most irradiance arriving below the solar panel were different by month, but its difference was up to 2%p between the irradiance with 30° angle which is usually recommended in Korea. Finally, the interval between panels was adjusted; when the ratio of the length of the panel to the empty space was 1:2, the irradiance of 0.719 times was reached compared to when there was no panel, 0.579 times for 1:1 and 0.442 times for 2:1.

• International Area Studies Review
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• v.16 no.1
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• pp.3-27
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• 2012

This paper adopts recently developed panel unit root test that is cross-sectionally robust. Cointegration test is also used to find whether regional house prices are in line with gross regional domestic production (GRDP) in the long run in Korea during 1989-2009. Based on the panel VECM and the panel ARDL models, we examine causal relationships among the variables and estimate the long-run elasticity. We find evidence of cointegration and bidirectional causal relationships between regional house prices and GRDP. The results of long-run estimates, using both fixed effect and ARDL models, show that house prices positively and significantly influence on the GRDP and vice versa. Together with these results, the findings of ARDL-ECM imply that there exists a long-run equilibrium relationship between house prices and regional economic variables even if there is a possibility of short-run deviation from its long-run path.

• The Journal of Korean Association of Computer Education
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• v.17 no.6
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• pp.103-113
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• 2014

This study designed and implemented a query model for consecutive analyses of dynamic multivariate graph data. First, the query model consists of two procedures; setting the discriminant function, and determining an alteration method. Second, the query model was implemented as a query system that consists of a query panel, a graph visualization panel, and a property panel. A Node-Link Diagram and the Force-Directed Graph Drawing algorithm were used for the visualization of the graph. The results of the queries are visually presented through the graph visualization panel. Finally, this study used the data of worldwide import & export data of small arms to verify our model. The significance of this research is in the fact that, through the model which is able to conduct consecutive analyses on dynamic graph data, it helps overcome the limitations of previous models which can only perform discrete analysis on dynamic data. This research is expected to contribute to future studies such as online decision making and complex network analysis, that use dynamic graph models.