• The Journal of the Acoustical Society of Korea
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• v.40 no.1
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• pp.1-9
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• 2021

High-frequency bistatic sea surface scattering channels according to sea state were measured at an experimental site of Geoje bay in April 2020, and compared with predictions based on scattering theory. A linear frequency-modulated signal with a center frequency of 128 kHz and a bandwidth of 32 kHz was used for the acoustic measurements. Sea surface wavenumber spectrum was calculated from surface roughness data measured by a wave buoy, and bistatic scattering cross-section of Small Slope Approximation (SSA) based on the wavenumber spectrum was estimated. In addition, scattering from near-surface bubbles using wind speed measured during experiments was considered. Surface scattering channel intensity impulse responses were simulated using the scattering cross-section and the simulation results were compared and analyzed with the field data.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.607-612
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• 2020

In this paper, we deal with the stability of linear discrete systems with time-varying delays and unstructured uncertainty. Stability conditions are derived based on Lyapunov stability theory, and can include the effect of uncertainty. The unstructured uncertainty in the papaer which can not be figured out its exact characteristics and only can be expreesed by its magnitude is considered. Compared with the previous results on the stability, the new results can expand the applicable systems and alleviate the stability conditions which are more effective and powerful. The proposed stability condition is expressed in the form of an simple inequality, and includes the both effects of the uncertainties and time-varying delay. We present the results comparing the new stability condition with the existing results, and verify the effectiveness and the superiority of the proposed results through numerical example.

• Ocean Systems Engineering
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• v.11 no.1
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• pp.17-42
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• 2021

Articulated loading platforms (ALPs) belongs to a class of offshore structures known as compliant. ALP motions have time periods falling in the wind excitation frequency range due to their compliant behaviour. This paper deals with the dynamic behavior of a double hinged ALP subjected to low-frequency wind forces with random waves. Nonlinear effects due to variable submergence, fluctuating buoyancy, variable added mass, and hydrodynamic forces are considered in the analysis. The random sea state is characterized by the Pierson-Moskowitz (P-M) spectrum. The wave forces on the submerged elements of the platform's shaft are calculated using Morison's Equation with Airy's linear wave theory ignoring diffraction effects. The fluctuating wind load has been estimated using Ochi and Shin wind velocity spectrum for offshore structures. The nonlinear dynamic equation of motion is solved in the time domain by the Wilson-θ method. The wind-structure interactions, along with the effect of various other parameters on the platform response, are investigated. The effect of offset of aerodynamic center (A.C.) with the center of gravity (C.G.) of platform superstructure has also been investigated. The outcome of the analyses indicates that low-frequency wind forces affect the response of ALP to a large extent, which otherwise is not enhanced in the presence of only waves. The mean wind modifies the mean position of the platform surge response to the positive side, causing an offset. Various power spectral densities (PSDs) under high and moderate sea states show that apart from the significant peak occurring at the two natural frequencies, other prominent peaks also appear at very low frequencies showing the influence of wind on the response.

• Journal of Distribution Science
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• v.20 no.8
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• pp.93-103
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• 2022

Purpose: Online shopping festivals have quickly become the newest trend in online shopping worldwide due to the COVID-19 pandemic. This has led to marketing distribution channels that traditionally emphasized traditional techniques having turned to electronic commerce platforms. Although the pandemic scenario encourages online purchasing, other factors, such as the influence of participation intention to shop during the Online Shopping Festival, must also be considered. Research design, data and methodology: Multiple linear regression analysis was used to test the hypothesis based on data from 121 respondents who are actively involved with online shopping activities in Klang Valley, Selangor. Results: The results of this study show that promotion categories and the perceived influence of mass participation have a significant influence on participation intention. Meanwhile, the perceived temptation of price promotion and perceived fun promotional activities did not significantly influence participation intention. Conclusions: Theoretically, this study contributes to the literature by using the Theory of Planned Behavior and Stimulus-Response models to explain the factors that drive participation intention for online shopping. In practice, this study attracts and encourages customers to shop during the festival day because various attractive promotions are offered by sellers in Malaysia.

• Smart Media Journal
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• v.11 no.8
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• pp.21-28
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• 2022

Currently, as we enter the 21st century, the level and interest of society, culture, economy, and science are rapidly developing, but science education is still struggling. In order to increase the efficiency of science education, it is most important to focus on elementary education based on basic science. Therefore, this study aims to analyze the main causes of Korea's science museum's regression as a museum focusing on experience, interest, and fun such as simple science experience centers and science theme parks. To this end, the influencing factors were identified by applying the algorithm of the actor-based model based on the data on the exhibition space and the exhibition movement of the science museum completed and operated in Korea over the past 5 years, and the problem of the visitor movement in the exhibition space was analyzed through the space system. In this study, it was confirmed that the exhibition environment was the best when the linear plot movement system and the picalesque plot were applied simultaneously in the museum's exhibition narrative theory, and the arrangement of major exhibition spaces, width of exhibition spaces, and separation of spaces for exhibition purposes were derived.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.93-99
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• 2022

Analytical solutions for regular waves generated by bottom wave makers in a 3-dimensional wave basin were derived in this study. Bottom wave makers which have triangular, rectangular and combination of two shapes were adopted. The 3-dimensional velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions in a wave basin. Then, analytical solutions of 3-dimensional particle velocities and free surface displacement were derived from the velocity potential. The solutions showed physically valid results for regular waves generated by bottom wave makers in a wave basin. The analytical solution for obliquely propagating wave generation from bottom wave maker which works like a snake was also derived. Numerical results of the solution agree well with theoretically predicted results.

• Journal of Nutrition and Health
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• v.56 no.1
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• pp.112-121
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• 2023

Purpose: Eating behaviors are influenced by food environments, such as availability and/or accessibility of healthy food options. In this study, we examined the relationship between healthy eating-out options and the intention to eat healthily in adults residing in Daqing, China, using an extended theory of planned behavior (TPB). Methods: Data were collected via an online survey conducted from April to May 2021 using a previously validated questionnaire in Daqing. A total number of 308 subjects aged 18-64, either Daqing oilfield workers or their family members were eligible and finally included in the analysis. The relationships among the attributes and the quality of healthy eating-out options, the three major constructs of TPB, and the intentions of healthy eating were examined using multiple linear regression analyses. Results: Subjective norms (p = 0.049) and perceived behavioral control (PBC) (p = 0.000) were significantly related to the healthy eating intention. The quality and attributes of the food served statistically significantly explained the intention to eat healthily. After controlling for age, sex, and body mass index, not the quality but the attributes of food served (p = 0.037), subjective norms (p = 0.016), and PBC (p = 0.000) had a significant relationship with the intention to eat healthily. The model explained 83.7% of the variance. Conclusion: The healthy eating-out choices, along with subjective norms and PBC of TPB, may be a potential determinant of healthy eating intention among Chinese adults living in Daqing, China. Policy implications have highlighted that not only the personal intention to eat healthy foods, but also the available healthy food environment may be important for the choice of healthy options by the population of interest. Therefore, building an environment for healthy eating choices and campaigns aimed at increasing consumer awareness of healthy eating are equally important for a smart eating choice.

• Journal of applied mathematics & informatics
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• v.41 no.1
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• pp.51-70
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• 2023

The flow of an incompressible Ellis fluid in an inclined asymmetric channel, driven by peristaltic waves was studied under low Reynolds number and long wavelength assumptions. The wave on each side of the channel are assumed to be an infinite train of sinusoidal waves, both having the same constant wave speed and wavelength however, they vary in wave amplitude, channel half width and phase angle. We derived expressions for the axial and transverse velocities, volume flow rate, pressure rise per unit wavelength and streamlines. The effects of varying the wave amplitudes, the phase angle, the channel width, the angle of inclination of the channel as well as the fluid parameters on the flow were analyzed. Trapping conditions were determined and the presence of reflux highlighted using the streamlines for the necessary channel and fluid conditions. By varying the fluid parameters, changes in the fluid that deviated from the Newtonian case resulted in a reduction in the axial velocity in the neighborhood of the center of the channel and a simultaneous increase in the velocity at the periphery of the channel. A nonlinear relation was observed with the pressure rise and the volume flow rate. This nonlinear relation is more pronounced with an increase in the absolute value of the volume flow rate. For Newtonian fluids a linear relation exists between these two variables. The fluid parameters had little effects on the streamlines. However, variations of the wave amplitudes, volume flow, channel width and phase angle had greater effects on the streamlines and hence the trapped region.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.65-73
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• 2009

Large scale model tests and numerical analyses are performed to investigate the stress distribution of pillar due to surface loading nearby two-arch tunnel which is constructed in the regularly jointed rocks. It is observed that the influence of discontinuities on the stress distribution in the discontinuous rock mass and the underground stresses induced by surface loading are greater than those of linear elastic theory. Especially, lines of equal stresses are developed to the direction of inclination according to the inclined grade. In cases of discontinuities imbedded in parallel with or vertical to the ground, the pressure bulbs are formed symmetrically, however, the inclined ones result in stress distribution in parallel with and vertical to the planes of discontinuities. Results indicated that stress distribution is seriously affected by the angle of discontinuity. When stresses propagating to the pillar need to be estimated, relative location of surface loading, grade of discontinuous plane, and location of two-arch tunnel should be carefully considered.

• Journal of the Korean Geotechnical Society
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• v.24 no.7
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• pp.17-24
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• 2008

In this study, the triaxial behaviour of an unsaturated soil was analyzed by Bishop stress descriptions. $K_0$ stress paths and those final values were independent of matric suctions after describing by the Bishop stress. The failure criteria could be defined uniquely by the Bishop stress and were also independent of matric suctions. In the low level of matric suctions the failure criteria have a linear relationship and the estimated criterion fits the measured accurately. The variable ${\chi}$ for describing the Bishop stress was a constant theoretically under the low level of matric suctions. The suction stress could be defined at zero deviatoric stress in the failure criteria and increased linearly with respect to matric suctions in both the theory and the experiments.