• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.5
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• pp.524-531
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• 2004

To investigate relevance of the definition of the reference stress to estimate J and $C^{*}$ for surface crack problems, this paper compares FE J and $C^{*}$ results for surface cracked pipes with those estimated according to the reference stress approach using various definitions of the reference stress. Pipes with part circumferential inner surface crack and finite internal axial crack are considered, subject to internal pressure and global bending. The crack depth and aspect ratio are systematically varied. The reference stress is defined in four different ways using (i) the local limit load, (ii) the global limit load, (iii) the global limit load determined from the FE limit analysis, and (iv) the optimized reference load. It is found that the reference stress based on the local limit load gives overall excessively conservative estimates of J and $^{*}$. Use of the global limit load clearly reduces the conservatism, compared to that of the local limit load, although it can provide sometimes non-conservative estimates of J and $^{*}$. The use of the FE global limit load gives overall non-conservative estimates of J and $^{*}$. The reference stress based on the optimised reference load gives overall accurate estimates of J and $^{*}$, compared to other definitions of the reference stress. Based on the present finding, general guidance on the choice of the reference stress for surface crack problems is given.

• Journal of The Korean Astronomical Society
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• v.54 no.4
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• pp.129-137
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• 2021

It has been established that the acoustic mode parameters of the Sun and Sun-like stars vary over activity cycles. Since the observed variations are not consistent with an activity-related origin, even Sun-like stars showing out-of-phase changes of mode frequencies and amplitudes need to be carefully studied using other observational quantities. In order to test whether the presumed relations between the global seismic parameters are a signature of the stellar activity cycle, we analyze the photometric light curve of HD 49933 for which the first direct detection of an asteroseismic signature for activity-induced variations in a Sun-like star was made, using observations by the CoRoT space telescope. We find that the amplitude of the envelope significantly anti-correlates with both the maximum frequency of the envelope and the width of the envelope unless superflare-like events completely contaminate the light curve. However, even though the photometric proxy for stellar magnetic activity appears to show relations with the global asteroseismic parameters, they are statistically insignificant. Therefore, we conclude that the global asteroseismic parameters can be utilized in cross-checking asteroseismic detections of activity-related variations in Sun-like stars, and that it is probably less secure and effective to construct a photometric magnetic activity proxy to indirectly correlate the global asteroseismic parameters. Finally, we seismically estimate the mass of HD 49933 based on our determination of the large separation of HD 49933 with evolutionary tracks computed by the MESA code and find a value of about 1.2M_☉ and a sub-solar metallicity of Z = 0.008, which agrees with the current consensus and with asteroseismic and non-asteroseismic data.

• Journal of Korea Trade
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• v.23 no.8
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• pp.89-109
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• 2019

Purpose - We perform an empirical analysis of the effects of global consumer culture positioning (GCCP) in TV advertisements on consumer's brand evaluations (perceived quality, perceived price, and brand prestige) and attitude toward brand. Also, we analyze the moderating roles of consumer characteristics (ethnocentrism and level of product knowledge) in those effects. Design/methodology - This research is based on a survey of 210 randomly-selected university students in Seoul, Korea. The participants in the survey were shown a total of 8 TV advertisements of consumer goods of nondurable goods (fast food and carbonated drinks), and durable goods (sports shoes and digital camera), which included two advertisements for each product where one uses GCCP strategy while another uses LCCP strategy. We estimate the structural model using the AMOS 18.0 computer program. Findings - We find that GCCP has more positive effects on consumers' brand evaluations and attitude toward brand than LCCP in TV advertising. We also find that GCCP has stronger effects on brand evaluation and attitude toward brand in consumers with weak ethnocentrism and in those with a low level of product knowledge. Practical implications - Using GCCP in an advertisement is an effective way of improving consumer's evaluation of the brand and attitude toward the brand mainly when cosmopolitan consumers and consumers with low knowledge levels are segmented as targets. Originality/value - The study contributes to identify how and for what consumer groups' global brand positioning strategies in TV advertisements affect consumers' brand evaluations and their attitudes toward brands.

• Journal of The Korean Society of Agricultural Engineers
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• v.66 no.1
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• pp.25-37
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• 2024

As the agricultural land use shifts from paddy to upland, ensuring reservoir water supply stability for upland crop irrigation becomes essential. The objectives of this study were to estimate the irrigation water requirements considering the upland irrigation scenario and to evaluate the reliability of the water supply from the agricultural reservoir using resilience indexes. Two study sites, Sinheung and Hwajeong, were selected, and soybean and red peppers, the most water-intensive crops, were selected as study crops, respectively. For the irrigation scenario, two irrigation methods of traditional scheduling (which irrigates all sites at once) and rotational scheduling (which distributes irrigation by districts), along with the upland conversion rate, were considered. The net irrigation requirement was estimated through a water balance analysis. The stability of the reservoir was evaluated using resilience indexes based on the simulated 10-years reservoir water levels and drought criterion. Overall, the water supply of the reservoir was evaluated as stable during the simulated 10 years, except for the one year. Compared to the two irrigation methods, rotational scheduling resulted in lower irrigation water usage in both sites, with reductions of 1.6%, and 0.3%, respectively. As the upland conversion rate increases, the water deficit could be intensified in Hwajeong with a conversion rate exceeding 50%, showing the number of deficit(ND) over the one and a rapid increase in the deficit ratio(DR). It was confirmed that the reservoir operation criteria can be enhanced by incorporating resilience indicators along with crop growth information, thus, this will be a further study.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.5
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• pp.495-505
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• 2005

This study is to estimate source contribution by air pollutantion types (point, area, line) over Seoul metropolitan area. The Air Pollution Model (TAPM) and the highly resolved anthropogenic and biogenic gridded emissions ($1km{\times}1km$) were applied to simulate $SO_2,\;NO_2,\;O_3\;and\;PM_{10}$ concentrations by seasons and contribution was estimated by their source types (point, area, line). The results showed that the simulated concentrations of secondary pollutant agreed well with observed values with an index of agreement (IOA) over 0.4, whereas IOAs over 0.3 were observed for most primary pollutants. The contributions of each source types by seasons were similar. The point source contribution was the highest for $SO_2$ at medium level ranged from $55.1\%\;to\;61.5\%$. But the contribution from area source during for the spring and summer increased as the concentration level increased. The line source contribution was the highest for $NO_2$ at all levels ranged from $68.3\%\;to\;93.1\%$. The results indicate that $SO_2$ emissions should be mainly controlled from point source, as well as area source at higher level concentration. Also, $NO_2\;and\;PM_{10}$ to from line source should be controlled.

• Proceedings of the IEEK Conference
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• 2009.05a
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• pp.76-78
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• 2009

This paper considers the problem of global adaptive regulation for a class of nonlinear systems which have multiple unknown virtual control coefficient. By using a new parameter estimator and backstepping technique, we design a smooth state feedback control law, parameter update laws that estimate the unknown virtual control coefficients, and a continuously differentiable Lyapunov function which is positive definite and proper.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.569-572
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• 1999

In this paper we present a color image segmentation algorithm based on statistical models. A novel deterministic annealing Expectation Maximization(EM) formula is derived to estimate the parameters of the Gaussian Mixture Model(GMM) which represents the multi-colored objects statistically. The experimental results show that the proposed deterministic annealing EM is a global optimal solution for the ML parameter estimation and the image field is segmented efficiently by using the parameter estimates.

• Korean Journal of Mathematics
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• v.13 no.2
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• pp.139-148
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• 2005

In this paper we extend the mixed finite element method and its $L_2$-error estimate for postprocessed solutions by using Crank-Nicolson time-discretization method. Global $O(h^2+({\Delta}t)^2)$-superconvergence for the lowest order Raviart-Thomas element ($Q_0-Q_{1,0}{\times}Q_{0,1}$) are obtained. Numerical examples are presented to confirm superconvergence phenomena.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.4
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• pp.31-42
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• 2015

The objective of this study is to estimate the flood flow of inaccessible regions using satellite-derived rainfall and global geographic data. This study focuses on Dongsingun, an area located upstream of the Cheongcheon River in North Korea. The IFAS model was used to estimate flood flow. The model was calibrated in the Gap Stream watershed in South Korea and verified for the Byeongsung Stream watershed in the Nakdong River basin. Satellite-derived rainfalls for North Korea was revised using ground gauge data. Analysis results using CMORPH and GSMaP_NRT showed $4,886m^3/s$ and $5,718m^3/s$ respectively. In future studies, hydrological analysis in unmeasured and inaccessible regions will be carried out by applying more rainfall events.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.198-204
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• 2020

This paper designs a electromagnetic-log (EM-Log) aided navigation filter for maritime environment without global navigation satellite system (GNSS). When navigation is performed for a long time, Inertial navigation system (INS)'s error gradually diverges. Therefore, an integrated navigation method is used to solve this problem. EM-Log sensor measures the velocity of the vehicle. However, since the measured velocity from EM-Log contains the speed of the sea current, the aided navigation filter is required to estimate the sea current. This paper proposes a single model filter and interacting multiple (IMM) model filter methods to estimate the sea current and analyzes the influence of the sea current model on the filter. The performance of the designed aided navigation filter is verified using a simulation and the improvement rate of the filter compared to the pure navigation is analyzed. The performance of single model filter is improved when the sea current model is correct. However, when the sea current model is incorrect, the performance decreases. On the other hands, IMM model filter methods show the stable performance compared to the single model.