• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.1
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• pp.46-56
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• 1995

Three Pressure type wave gauges were installed for about 10 days for the analysis of long wave agitations in Mukho Harbor. Helmholtz and second resonant periods of seiche in Mukho Harbor are shown to be approximately 10.0-14.3 and 3.3 minutes from the spectral analysis of measured wave data. Amplification ratio at Helmholtz period reaches about 6.8 and the wave amplitudes in the harbor were in the range of 5-10 cm during the measurement period. Helmholtz and second resonant periods of seiche in Mukho Harbor agree very well with those computed using Jeong dt al. (1993b)'s model. The model gives rise to the first and third resonant peaks at 7.5 and 1.9 minutes, respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.627-633
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• 2007

This paper describes position tracking system of a container trailer approaching to a gantry crane for loading or unloading a container into or from a ship, respectively. Proposed position tracking system informs the trailer driver of right position to stop the car under a gantry crane. To measure the location of a trailer, we used Cricket Mote modules which adopted RF and ultrasound technology. We present an elaborate method to improve position errors occurring at sensing and calculate three dimensional position by triangulation along with how to reduce location tracking interval for real-time monitoring. The location information was transmitted to a Personal Digital Assistant (PDA) periodically through Bluetooth communication for guidance of the trailer driver. In indoor and outdoor tests, position errors were less than 3 cm and location tracking interval was 0.5 second on average.

• Proceedings of the Korean Society of Computer Information Conference
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• 2019.01a
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• pp.189-190
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• 2019

본 연구에서는 명절이 소비자들의 제품 교체주기에 영향을 미치는지를 탐색하기 위해 중국 온라인 휴대폰 판매 데이터를 바탕으로 명절 시기별 구매간격 차이검증을 통해 실증적으로 분석하고자 하였다. 분석결과, 명절시점과 평상시점 간에 제품 구매간격의 차이가 있는 것으로 나타났다. 즉, 명절시점이 평상시점보다 제품 교체주기가 짧은 것으로 나타나 명절효과가 있음을 증명하였다. 한편, 춘절, 노동절, 국경절 등 명절유형 간 제품 구매간격의 차이는 나타나지 않았다. 이는 기업이 명절시점을 활용하여 교체 가능성이 높은 소비자를 선별적으로 공략한다면 더 높은 성과를 얻을 수 있음을 시사한다. 본 연구의 결과는 실무적으로 볼 때 기업으로 하여금 교체확률이 높은 시기에 마케팅을 집중할 수 있도록 할 수 있을 것이며, 학술적으로는 제품 구매 간격에 영향을 미치는 구매시점 효과 중 명절효과를 온라인상의 고관여 제품에 적용하여 탐구했다는 공헌점이 있다.

• Journal of Aerospace System Engineering
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• v.17 no.5
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• pp.1-10
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• 2023

This research sought to determine the optimal cycle of Planned Depot Maintenance (PDM) for Unmanned Aerial Vehicle (UAV), and PDM through Reliability and Maintainability-based simulation and Operating and Support (O&S) cost analysis using Reliability and Maintainability analysis results. The effectiveness of the PDM was verified economically, and the optimal PDM interval that balances UAV effective operations and sustaining engineering costs was presented.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.48-56
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• 2013

In this paper, the equivalent elastic properties of fiber reinforced plastic laminar are investigated using various homogenization schemes. Although there are several methods for predicting the equivalent elastic properties such as analytical formula or semi-empirical formula, most of them have some limitations or are not much accurate when handling new composite material consisting of various fiber, matrix and fiber-volume fraction ratio. To resolve the issues, computational homogenization scheme is adopted with a representative volume element (RVE) comprised of a set of finite elements. Finally, the equivalent elastic properties are obtained by applying periodic boundary conditions. The obtained results are compared with those by the existing methods and test results. Also its effect on structural analysis results of the composite satellite panel is investigated.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.53-61
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• 2007

This study investigates the effect of site class, post-yield stiffness ratio, damping ratio, yield-strength reduction factor, and natural period on inelastic displacement ratio of bilinear SDF systems located at the sites classified as NEHRP site class B,C,D. The previous studies developed inelastic displacement ratio using equal displacement rule in the intermediate and long period range. But, this approximation overestimates the inelastic displacement ratio. Furthermore, inelastic displacement ratio has not been developed for the systems having a damping ratio less than 5%. This study conducts nonlinear regression analysis for proposing equations for calculating median and deviation of the inelastic displacement ratio of the bilinear SDOF system having damping ratios ranging from 0 to 20%. Using median and deviation of the inelastic displacement ratio, probabilistic inelastic displacement ratio is estimated, which can be used for performance-based seismic evaluation.

• Journal of the Korean Geotechnical Society
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• v.36 no.6
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• pp.17-34
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• 2020

In response spectrum analysis of pile-supported structure, an amplified seismic wave should be used as the input ground acceleration through the site-response analysis. However, each design standard uses different input ground acceleration criteria, which leads to confusion in determining the appropriate input ground acceleration. In this study, the ground accelerations were calculated through dynamic centrifuge model test, and the response spectrum analysis was performed using the calculated ground acceleration. Then, the moments derived from the test and analysis were compared, and a method for determining the appropriate input ground acceleration in response spectrum analysis was presented. Comparison of the experimental and simulated results reveals that modeling of the ground using elastic springs allows proper simulation of the natural period of the structure, and the use of a seismic wave that is amplified at the ground surface as the input ground acceleration provided the most accurate results for the response analysis of pile-supported structures in sands.

• Journal of the Korea Convergence Society
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• v.12 no.3
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• pp.409-420
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• 2021

The study is a descriptive research to determine high school girls' the status of dysmenorrhea and to look into influencing factors about how relationships between variables: sleep disturbance, stress, anxiety, dietary habit have an effect on dysmenorrhea. Our collected data consisted of 160 high school girls living in B metropolitan city. The study period lasted four weeks, going from Oct 12 to Nov 6, 2020. The resulting data was analyzed with SPSS/WIN 21.0 version to analyze. As a result of this study, The correlated factors of dysmenorrhea included sleep disturbance(r=.531, p<.001), stress(r=.349, p<.001), anxiety(r=.300, p=.003) and dietary habit(r=-.205, p=.041). The prevalent factors influencing dysmenorrhea are sleep disturbance, menstrual periods, menstrual cycles, and anxiety. Therefore, it will be needed to improve the quality of sleep, reduce anxiety, try to regulate menstrual periods and menstrual cycle in order to relieve high school girls' dysmenorrhea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.4
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• pp.119-127
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• 2022

To investigate varying wave impact pressure exerting at the crest wall of rubble mound seawall, depending on breaking wave properties, regular waves with different wave periods were generated. Wave velocity fields and void fraction were measured using bubble image velocimetry and simple combined wave gauge system (Na and Son, 2021). For the waves with shorter wave period, maximum horizontal velocity was less reduced compared to incident wave speed while breaking-induced air entrainment was occurred intensely, leading to a significant reduction of wave impact pressure at the crest wall. For the waves with longer wave periods, less air wave entrained and the wave structure followed a flip-through mode (Cooker and Peregrine, 1991), resulting in an abrupt increase of the impact pressure.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.230-236
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• 2001

The numerical investigations on the wave-screening characteristics of floating breakwaters are presented. The fluid motion is idealized as linearized, two dimensional potential flow. A finite element model is adopted to analyze the performance of floating breakwaters. Numerical experiments are carried out for two type floating breakwater. One is a conventional pontoon type breakwater with rectangular cross-section, and the other is a side float breakwater which consists of two rectangular shaped floats connected to each other by a frame. To improve the performance of the floating breakwaters, especially for long-period wave conditions, numerical experiments are carried out for the cases attaching the thin plates at the bottom of folats in the vertical direction.