• 한국해양공학회지
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• 제37권4호
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• pp.158-163
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• 2023

Objects adrift can cause considerable damage to coastal infrastructure and property during tsunami and storm surge events. Despite the potential for harm, the drifting behavior of these objects remains poorly understood, thereby hindering effective prediction and mitigation of collision damage. To address this gap, this study employed a motion analysis program to track a drifting container's location using images from an existing laboratory experiment. The container's trajectory and velocity were calculated based on the positions of five markers strategically placed at its four corners and center. Our findings indicate that the container's maximum drift velocity and distance are directly influenced by the scale of the solitary wave and inversely related to the container's weight. Specifically, heavier containers are less likely to be displaced by solitary waves, while larger waves can damage coastal structures more. This study offers new insights into container drift behavior induced by solitary waves, with implications for enhancing coastal infrastructure design and devising mitigation strategies to minimize the risk of collision damage.

• 한국해양생명과학회지
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• 제9권1호
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• pp.47-52
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• 2024

Light is a major external environmental factor that influences the circadian rhythm of photosynthetic organisms and various physiological phenomena, such as growth, maturation, and behavior. The number of light-reaching organisms changes depending on the season and atmospheric conditions, and the intensity and wavelength of light differ depending on the organisms inhabiting the environment. Altered light changes the circadian rhythm of fish, which is controlled by clock genes, such as period 2 (Per2), cryptochrome 1 (Cry1), and melatonin. In this study, we set the zeitgeber time (ZT; 14 light-10 dark, LD) based on the actual sunrise and sunset times and examined Per2 and Cry1 activities, levels of aralkylamine N-acetyltransferase (AANAT), and melatonin in Pholis nebulosa, a drifting seaweed species exposed to irregular light. Per2 and Cry1 levels increased during the daytime and decreased after sunset. The AANAT levels decreased during the daytime and increased during the night. Melatonin concentration was highest around midnight (ZT21, 23:30), but exhibited similar concentrations during the daytime. While the activity of Per2, Cry1, and AANAT levels exhibited a typical circadian rhythm observed in most vertebrates, melatonin concentrations did not show a significant difference between the daytime and nighttime. These findings provide insights into the circadian rhythm patterns of organisms exposed to irregular light environments, such as P. nebulosa, which differ from those of typical fish species.

• 한국환경농학회지
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• 제8권1호
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• pp.17-29
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• 1989

본 연구는 삼림환경내에 살포된 살충제 cyfluthrin과 trichlorfon의 물에서의 잔류 및 동태 와 수서생물에 미치는 영향을 비교, 분석하기 위하여 수행하였다. 농약은 오리나무 잎벌레(Agelastica coerulea B.)를 구제하기 위하여 2회 항공살포 (살포량 : cyfluthrin 25g ai/ha, trichlorfon 536g ai/ha)하였으며, 아울러 수서곤충에 대한 영향을 비교하기 위하여 야외 소하천에서 모의실험을 실시한 바, 그 결과는 다음과 같다. 물에서 cyfluthrin은 살포직후에는 $0.62{\mu}g/L$ (1차) $78{\mu}g/L$(2차)이나 토양, 저질등에 흡착되어 1차 살포의 경우는 1일후에 검출되지 않았고, 2차 살포의 경우에는 4시간 이후에 $1{\mu}g/L$이하로 떨어져 급격히 소실됨을 알 수 있었다. Trichlorfon은 강우에 의한 영향을 크게 받아 농약 살포후 22일까지 농도의 증감이 계속되었다. 수서생물에 대한 영향을 보면, cyfluthrin은 어류와 동물성 플랑크톤에 대한 영향은 없었으나, 수서곤충에 대해서는 38-73배(항공살포), 1200-2000배(모의실험)의 표류량이 관찰되었다. Trichlofon은 어류에 대한 영향은 없었으나, 동물성 플랑크톤 중 Copepoda와 Cladocera에 대한 영향이 관찰되었으나 수서곤충에 대해서는 큰 영향이 없었다. 수서곤충의 목별 감수성 은 cyfluthrin의 경우 하루살이목, 딱정벌레목, 파리목의 순서로 감수성이 낮고, trichlorfon은 파리목이 비교적 민감하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.38-52
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• 2016

This paper describes the nonlinear dynamic motion behavior of a ship equipped with a portable dynamic positioning (DP) control system, under external forces. The waves, current, wind, and drifting forces were considered in the calculations. A self-tuning controller based on a neuro-fuzzy algorithm was used to control the rotation speed of the outboard thrusters for the optimal adjustment of the ship position and heading and for path tracking. Time-domain simulations for ship motion with six degrees of freedom with the DP system were performed using the fourth-order RungeeKutta method. The results showed that the path and heading deviations were within acceptable ranges for the control method used. The portable DP system is a practical alternative for ships lacking professional DP facilities.

• Ocean Systems Engineering
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• 제5권3호
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• pp.199-220
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• 2015

The paper described the nonlinear dynamic motion behavior of a barge equipped with the portable outboard Dynamic Positioning(DP) control system in short-crested waves. The DP system based on the fuzzy theory is applied to control the thrusters to optimally adjust the ship position and heading in waves. In addition to the short-crested waves, the current, wind and nonlinear drifting force are also included in the calculations. The time domain simulations for the six degrees of freedom motions of the barge with the DP system are solved by the $4^{th}$ order Runge-Kutta method. The results show that the position and heading deviations are limited within acceptable ranges based on the present control method. When the dynamic positioning missions are needed, the technique of the alternative portable DP system developed here can serve as a practical tool to assist those ships without equipping with the DP facility.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.385-392
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• 2018

This paper presents 2D numerical modeling to calculate ship-ice interactions that occur when an icebreaker advances into ice-covered water. The numerical model calculates repeated icebreaking of an ice plate and removal of small ice floes. The icebreaking of the ice plate is calculated using a ship-ice contact detection technique and fluid-structural interaction of ice plate bending behavior. The ship-ice interactions in small ice floes are calculated using a physically based modeling with 3DOF rigid body equations. The ice plate is broken in crushing, bending, and splitting mode. The ice floes drift by wind or current and by the force induced by the ship-ice interaction. The time history of ice force and ice floe distribution when an icebreaker advances into the ice-covered water are obtained numerically. Numerical results demonstrate that the time history of ice force and distribution of ice floes (ice channel width) depend on the ice floe size, ship motion and ice drifting by wind or current. It is shown that the numerical model of ship maneuvering in realistic ice conditions is necessary to obtain precise information about the ship in ice-covered water. The proposed numerical model can be useful to provide data of a ship operating in ice-covered water.

• 한국게임학회 논문지
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• 제11권1호
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• pp.121-129
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• 2011

온라인 게임에서 오토 프로그램 또는 봇 프로그램으로 인하여 다양한 게임 서비스 피해사례가 발생하고 있다. 특히, 게임 머니 및 아이템의 비정상적인 수집은 게임이 가지는 본연의 재미를 잃어버리게 되고, 궁극적으로 게임 생명주기에 결정적 악영향을 미치게 된다. 본 논문은 게임 봇 감지를 위해 게임 행위 변화 패턴을 수집하고 분석하여 봇 탐지 방법에 적용한다. 인간의 게임 행위 변화 정보와 봇의 게임 행위 변화 정보를 이용하여 유사정도를 측정하고, 봇 탐지 기법에 활용하는 것이다. 실험에서는 서비스 중인 온라인 게임을 이용하여 사용자와 봇의 모델을 생성하고 유사성을 판별하였으며 적절한 결과를 확인하였다.

• Wind and Structures
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• 제32권5호
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• pp.453-469
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• 2021

Snow accumulation on the road frequently induces a big traffic problem in the cold snowy region. Accurate prediction on snow distribution is fundamental for solving drifting snow disasters on roads. The present study adopts the transient method to simulate the wind-induced snow distribution on embankment based on the mixture multiphase model and dynamic mesh technique. The simulation and field measurement are compared to confirm the applicability of the simulation. Furthermore, the process of snow accumulation is revealed. The effects of friction velocity and snow concentration on snow accumulation are analyzed to clarify its mechanism. The results show that the simulation agrees well with the field measurement in trends. Moreover, the snow accumulation on the embankment can be approximately divided into three stages with time, the snow firstly deposited on the windward side, then, accumulation occurs on the leeward side which induced by the wake vortex, finally, the snow distribution reaches an equilibrium state with the slope of approximately 7°. The friction velocity and duration have a significant influence on the snow accumulation, and the vortex scale directly affected the snow deposition range on the embankment leeward side.

• 한국동물생명공학회지
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• 제35권3호
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• pp.245-257
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• 2020

Behavioral response to a diel photoperiodicity (500 lx for 16 h, 5 lx for 4 h and < 0.5 lx for 4 h) and phototactic characteristics in dark conditions were examined with Siberian sturgeon Acipenser baerii (Chondrostei, Actinopterygii) prelarvae. Siberian sturgeon prelarvae represented both qualitative and quantitative changes in their behavioral patterns according to different light intensities in a diel photoperiodicity. Under daylight conditions (500 lx), prelarvae displayed saltatory changes of behavioral features with ages (Day 0-Day 9) in a general order of swimming-up/drifting, swimming in the upper water column, benthic swimming with rheotaxis, schooling and post-schooling behavior. Compared to daylight conditions, prelarvae tended to show more benthic performances and quantitative reductions of schooling and post-schooling behaviors under dimlight conditions (5 lx). Under dark conditions (< 0.5 lx), prelarvae exhibited a fairly uniform behavioral pattern characterized by the benthic swimming across the bottom of the tank. From phototaxis tests under dark conditions, navigational responses of prelarvae to a spotlight illumination were quantitatively changed as their ages increased. The phototactic responses reached the peak on Day 2, continued until Day 4, and then gradually decreased until Day 8. A partial recovery of positive phototaxis was observed on Day 9. Data from this study suggest that the diel light cycle as well as the light intensity of each interval in the cycle should be considered as important components of a practical guide for evaluating fitness and developmental states of artificially propagated Siberian sturgeon prelarvae.

• Smart Structures and Systems
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• 제16권2호
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• pp.295-328
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• 2015

In recent years the monitoring of structural behavior through acquisition of vibrational data has become common practice. In addition, recent advances in sensor development have made the collection of diverse dynamic information feasible. Other than the commonly collected acceleration information, Global Position System (GPS) receivers and non-contact, optical techniques have also allowed for the synchronous collection of highly accurate displacement data. The fusion of this heterogeneous information is crucial for the successful monitoring and control of structural systems especially when aiming at real-time estimation. This task is not a straightforward one as measurements are inevitably corrupted with some percentage of noise, often leading to imprecise estimation. Quite commonly, the presence of noise in acceleration signals results in drifting estimates of displacement states, as a result of numerical integration. In this study, a new approach based on a time domain identification method, namely the Unscented Kalman Filter (UKF), is proposed for correcting the "drift effect" in displacement or rotation estimates in an online manner, i.e., on the fly as data is attained. The method relies on the introduction of artificial white noise (WN) observations into the filter equations, which is shown to achieve an online correction of the drift issue, thus yielding highly accurate motion data. The proposed approach is demonstrated for two cases; firstly, the illustrative example of a single degree of freedom linear oscillator is examined, where availability of acceleration measurements is exclusively assumed. Secondly, a field inspired implementation is presented for the torsional identification of a tall tower structure, where acceleration measurements are obtained at a high sampling rate and non-collocated GPS displacement measurements are assumed available at a lower sampling rate. A multi-rate Kalman Filter is incorporated into the analysis in order to successfully fuse data sampled at different rates.