• Journal of Korea Water Resources Association
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• v.46 no.2
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• pp.205-218
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• 2013

The likelihood of rip current at Haeundae beach according to wave parameters, such as wave height, period, direction, and tidal elevation, was estimated by using numerical simulations with a Boussinesq model, FUNWAVE. To examine the estimation, the rip current occurred on 12th June, 2011 at Haeundae beach was simulated based on observations. For the estimation, the following procedure was carried out. First, extensive numerical simulations of nearshore circulations are performed under various random sea conditions according to the wave parameters. Second, from the numerical results, cross shore components of two-wave-period averaged velocities over the nearshore area were computed, and their seawardly maximum was defined as rip current velocity of the area. Third, using time series of the rip current velocity, we computed the ratio of the simulation time and the time period in which the rip current velocity exceed a threshold velocity for rip-current accidents, and thus the ratio was quantified as the likelihood of rip current at Haeundae beach for the input wave parameters. From the resultant estimations, it was found that the rip current likelihood increases as wave height and period increase, and tidal elevation decreases.

• Journal of Korea Water Resources Association
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• v.46 no.5
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• pp.477-490
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• 2013

A rip-current warning index function, which is estimated from the likelihood of rip current quantified based on numerical simulations under various sea environments and is varied according to real-time buoy-observations, was studied to help protect against rip current accidents at Haeundae beach. For the quantification, the definition of likelihood of rip current, which proposed by Choi et al. (2011, 2012b), was employed and estimated based on Boussinesq modelling. The distribution of likelihood of rip current was evaluated by using various simulations according to scenarios established based on physical quantities(i.e., wave parameters) of buoy-observations. To index the likelihood of rip current, empirical functions were derived based on the distribution and adjusted to observational environments. In this study, the observations from June to September in 2011 at Haeundae beach were applied to the rip-current index functions, and its applications into the real events found based on CCTV images were presented and investigated. In addition, limitations and improvements of the rip-current index function were discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.485-492
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• 2019

The observation system has been developed to investigate the rip currents at Haeundae beach using X-band marine radar. X-band radar system can observe shape, size, and velocity of rip currents, which is difficult to obtain through field observation by conventional device. Algorithms which automatically detect locations, shapes, and magnitudes of rip currents were developed using time averaged X-band radar sea clutter images. X-band sea clutter images are transformed through 3D FFT into 2D wave number spectrum and frequency spectrum. Rip current velocities were estimated using differences in wave-number spectra and wave frequency spectra due to Doppler shift. The algorithm was verified by drift experiments. At Haeundae beach, the radar system exactly located the rip currents and found to be sustained for 1-2 days at fixed locations.

• Journal of Ocean Engineering and Technology
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• v.30 no.4
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• pp.320-326
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• 2016

Rip current forecasts, based on intensity, are marked in four levels—notice, watch, warning, and danger. However, numerical results are represented by current vectors, whose magnitudes are then converted into predictive levels. In the present study, the rose diagram is adapted as a determinative forecasting index and examined for the case of an ideal rip channel consisting of surface, bottom, and averaged currents. Further, it is employed in the sensitivity analysis of wave-induced currents generated by wave conditions at the Haeundae Beach. The simulation of surface onshore and bottom undertow currents is accomplished by including a mass flux term in the wave-averaged continuity equation.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1059-1062
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• 2008

최근 유비쿼터스 시대에 고품질의 빠른 서비스를 제공하기 위한 에이전트 시스템의 연구가 활발히 진행 중이다. 멀티 에이전트 시스템은 플랫폼 위의 에이전트들이 서로 메시지를 전송하며 자율적이고 지능적으로 일을 처리하는 시스템이다. 에이전트간 메시지 전송을 최적화 하기 위해서는 전체 에이전트와, 네트워크 토폴로지에 대한 정보 공유가 필요하다. RIP 는 전체 네트워크 상태를 공유하는 라우팅 프로토콜로서 에이전트 메시지 전송 성능 개선에 적합한 기법이다. 하지만 RIP 라우팅 프로토콜은 여러 취약점이 있다. 에이전트 메시지 전송 성능 개선을 위한 에이전트의 운용은 위같은 문제를 해결하고 효과적인 메시지 전송을 가능하게 할 것이다.

• Korean Journal of Mathematics
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• v.31 no.4
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• pp.405-417
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• 2023

The RIP of rings was introduced by Kwak and Lee as a generalization of the one-sided idempotent-reflexivity property. In this study, we focus on rings in which all one-sided semicentral idempotents are central, and we refer to them as quasi-Abelian rings, extending the concept introduced by RIP. We establish that quasi-Abelianity extends to various types of rings, including polynomial rings, power series rings, Laurent series rings, matrices, and certain subrings of triangular matrix rings. Furthermore, we provide comprehensive proofs for several results that hold for RIP and are also satisfied by the quasi-Abelian property. Additionally, we investigate the structural properties of minimal non-Abelian quasi-Abelian rings.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.238-245
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• 2015

Recently, Choi et al.(2015) showed that a numerical simulation of the SandyDuck experiment under a directional random wave environment agreed well with the experimental data including the wave height distribution of the random waves, the well-developed longshore current and its energetic fluctuation. Based on the Boussinesq modeling, this study investigates the effect of the alongshore variations, which are induced by not only the field topography but also the phase interaction of multidirectional random waves in the surf zone wave field, on the rip currents. As a result, transient rip currents as well as topographical rip currents cause the complicated surfzone circulation and mixing process due to their interactions in a multi-directional random wave condition while the topographical rip currents are dominant in a monochromatic wave condition.

• Research in Community and Public Health Nursing
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• v.30 no.4
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• pp.460-470
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• 2019

Purpose: This study was to identify the factors influencing the practice of respiratory infection prevention (RIP) for the elderly residing in rural areas. Methods: The data were collected from 188 residents aged 65 years or older residing in the jurisdictions of four public health clinics in rural areas of C city, using a structured questionnaire for the period from December 1, 2018 to February 28, 2019. The collected data were analyzed with independent t-test, one-way ANOVA, Pearson's correlation coefficients, and hierarchical multiple regression analysis using SPSS/WIN 25.0 program. Results: The score on knowledge of RIP was 8.82±1.36, while it was 4.53±0.47 for attitude, 3.78±0.66 for practice, and 3.78±0.69 for social capital. It was observed that the factors influencing the practice of RIP were attitude of RIP (β=.38, p<.001), social capital (β=.29, p<.001), family type (β=-.19, p=.002), and subjective health status (β=.15, p=.035), while the explanatory power of the model was 47%. Conclusion: Consequently, to enhance the practice of RIP for the elderly residing in rural areas, it is necessary to develop programs considering social and environmental characteristics of rural areas based on their attitude of RIP, social capital, family type and subjective health status.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.276-284
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• 2011

The rip current occurred at Haeundae beach was numerically investigated under directional random wave environment. The numerical simulation was performed using a fully nonlinear Boussinesq equation model, FUNWAVE which is capable of simulating nearshore circulation since it includes the effect of wave-induced momentum flux and horizontal turbulent mixing. The results of numerical simulation show the time-dependent evolution of the wave-induced nearshore circulation system (including rip current) that are caused by nonlinear transformation of directional irregular waves due to unique topography of Haeundae. From the results, it was found that rip current is well generated and developed where relatively lower wave height and relatively deeper water depth along the longshore direction, and sudden and strong events of rip current were observed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.6
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• pp.411-419
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• 2020

The experiment of unsteady rip current generated at the successive ends of breaking wave crests of honeycomb pattern waves was conducted in a laboratory wave basin, and its time-varying evolution was observed by using ortho-rectified images. The present experiment utilized the generation of a quasi nodal line of the honeycomb-pattern waves formed by out-of-phase motion of two piston-type wavemakers arranged in the transverse direction, instead of the original honeycomb pattern waves which are generated when two wave trains propagate with slightly different wave directions. The velocities of rip current were measured by using the LSPIV (Large-Scale Particle Image Velocimetry) technique. As a result, the unsteady rip current was generated between successive ends of wave crests, and evolved with its shear fluctuations in this experiment. Also, the time series of LSPIV velocity of the unsteady rip current showd its short component due to waves and its long component due to wave-induced currents.