• 수산해양기술연구
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• 제60권1호
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• pp.27-36
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• 2024

The towing distance, which is speed over the ground, and the water flow quantity, which is speed through the water, were used when estimating the amount of Metapenaeus joyneri resources that rose to the surface at night using the swept area method in order to compare and analyze the difference. It was conducted using a shrimp dredge, trial fishing gear for catching Metapenaeus joyneri. Catch during the entire survey period was 188.9 kg. Monthly catch ranged from 3.1 to 109.2 kg, highest in June and lowest in September. The swept volume calculated using the speed over the ground was about 13% higher than using the speed through the water. Metapenaeus joyneri resources estimated using the towing distance ranged from 320.1 to 14,649.8 kg. Resources estimated using the water flow quantity ranged from 278.5 to 12,886.3 kg. Therefore, the amount of Metapenaeus joyneri resources estimated using the speed over the ground was about 14% higher than the method using the speed through the water, indicating that the amount of resources was overestimated.

• 대한조선학회 특별논문집
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• 대한조선학회 2015년도 특별논문집
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• pp.28-33
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• 2015

Speed log measurement has always been of utmost importance to the mariners. To date the most accurate maritime speed measurement comes from Doppler measurement, where speed may be measured relative to either water(speed through water) or seabed(speed over ground). Recently, a clarification has been issued by the International Maritime Organization (IMO) regarding the speed measuring devices, which could ultimately impact the final arrangement of these devices for ships being constructed after July 1, 2014. This paper will discuss the clarification in depth and necessary action which shall be taken by the owners and operators of the ships impacted.

• 해양환경안전학회지
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• 제28권2호
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• pp.254-261
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• 2022

모든 선박은 충돌을 피하기 위해 안전속력을 준수하여야 하고, 우리나라 영해 및 내수에서 속력의 제한규칙을 준수하여야 한다. 그리고 선박교통관제사는 선박이 안전속력과 속력의 제한규칙을 준수하도록 적절히 관제하여야 한다. 국제해상충돌예방규칙에서 안전속력은 선박이 명시적으로 몇 노트의 속력으로 항행하여야 하는지 규정하고 있지 않다. 반면에 국내법에서는 교통안전특정해역 등에서 제한속력을 지정하여 이를 준수하도록 하고 있다. 이 속력의 제한규칙은 주로 대지속력을 기준으로 하고 있으나, 대수속력을 기준으로 하는 곳도 있다. 이 논문은 최근 5년간 발생한 해양사고와 제한속력 위반율에 대해 분석하였고, 국제해상충돌예방규칙상 안전속력, 국내외법상 속력의 제한규칙 및 해양안전심판원 재결 중 안전속력을 준수하지 아니한 사례에 대해 살펴보았다. 그 결과, 이 논문에서는 국내법상 속력의 제한규칙이 선박에서 해양사고 예방을 위해 반드시 준수되어야 한다는 것과 선박이 이 규칙을 준수하기 쉽고, 선박교통관제사가 선박을 적절히 관제할 수 있도록 대수속력으로 규정된 속력의 제한규칙을 대지속력으로 개정할 필요가 있다는 것을 제시하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.60-64
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• 2013

Water injection pump produced the 1st oil well through the high pressure after the Deep water oil well drilling. After finish the work it is hard to produce only using itself pressure due to low pressure. Therefore it can be increased recovery factor through the injection seawater of high pressure. Is the key equipment used in the marine plant and it is developing at many industries. In this paper, Analyze changes in the natural frequency due to the stiffness of the bearing. Analyze the critical speed of the natural frequency due to the change of operation speed. And evaluate the Stability. And then analyze the displacement and clearance through the unbalance response this way has contributed to the reliability of the developing product. Through a mathematical analysis.

• Journal of information and communication convergence engineering
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• 제19권1호
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• pp.61-66
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• 2021

An underwater remotely operated vehicle (ROV) has been implemented. It can inspect foreign substances through a CCD camera while the ROV is running in water. The maximum thrust of the ROV's running thruster is 139.3 N, allowing the ROV to move forward and backward at a running speed of 1.03 m/s underwater. The structural strength of the guard frame was analyzed when the ROV collided with a wall while traveling at a speed of 1.03 m/s underwater, and found to be safe. The maximum running speed of the ROV is 1.08 m/s and the working speed is 0.2 m/s in a 5.8-m deep-water wave pool, which satisfies the target performance. As the ROV traveled underwater at a speed of 0.2 m/s, the inspection camera was able to read characters that were 3 mm in width at a depth of 1.5 m, which meant it could sufficiently identify foreign objects in the water.

• 한국가시화정보학회지
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• 제8권4호
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• pp.48-53
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• 2010

Water-uptake through roots, is an essential process of the water flow in plants. Its visualization is very useful for understanding sap flow dynamics at whole plant level. In this study, the tips of Arabidopsis' root hairs were excised and exposed to repeated dehydration and rehydration processes. The water-refilling through individual xylem vessels was visualized using the synchrotron X-ray micro-imaging technique. The high temporal resolution ($2\;{\mu}m$) and beam intensity of the X-ray source allowed to acquisition of consecutive X-ray images of the water-refilling process up to 10 frames/sec. Various flow patterns were observed and the ascending speed of the water-air interfaces was analyzed. The relation between the water-rising height and ascending speed was also analyzed. The present results would provide better alternative for investigating sap flows in roots.

• 대한조선학회논문집
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• 제45권3호
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• pp.280-287
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• 2008

In this paper, a mathematical model for a ship manoeuvring with low forward speed in shallow water was suggested. Based on the cross flow model with low forward speed in deep sea, hull, propeller and rudder models were modified to consider the shallow water effects. Static drift and PMM tests were performed to obtain the cross flow drag coefficients and hydrodynamic coefficients. To validate suggested mathematical model, numerical simulation results were compared with those of sea-trials. Through comparisons, it was concluded that suggested mathematical model could give proper estimation on turning test results.

• 대한조선학회논문집
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• 제61권1호
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• pp.1-7
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• 2024

Underwater sound speed is an important analysis parameter on an estimation of the underwater radiated noise (URN) emitted from vessels. This paper aims to present an underwater sound speed measurement procedure using a cross-correlation of time-domain acoustic signals and validate the procedure through an experiment in a reverberant water tank. For the purpose, time-domain acoustic signals transmitted by a Gaussian pulse excitation from an acoustic projector have been measured at 20 hydrophone positions in the reverberant water tank. Then, the sound speed in water has been calculated by a linear regression using 190 cross-correlation cases of distances and time lags between the received signals and the result has been compared with those estimated by the existing empirical formulae. From the result, it is regarded that the presented experimental procedure to measure an underwater sound speed is reliably applicable if the time resolution is sufficiently high in the measurement.

• 물과 미래
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• 제20권2호
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• pp.127-138
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• 1987

서해지역에서 해안구조물을 위한 설계파는 연안지상측후소의 과거 풍속자료로부터 해상풍의 설계풍속을 산정하고 지역별로 결정되는 취송역으로부터 파랑예측모델을 이용하여 결정하는 방법이 제안되었다. 서해에서 설계파를 지배하는 바람은 북서방향(W~N)의 동기계절풍과 남서(WSW~S) 방향의 하기계절풍 및 태풍이며 해상풍의 풍속은 U$\geq$20m/s의 탄풍에 대하여 연안의 지상풍속의 0.8~0.9배를 나타낸다. 서해의 해안지역은 그 위치여건에 따라 세 지역으로 구분할 수 있으며 각각의 지역에 대하여 설계파산정을 위한 취송역을 결정할 수 있다. 수정된 S.M.B. 법에 의하면 서해지역에서 100년빈도 설계파의 심해유의파고는 4.4m~8.3m, 주기는 8.9초~12.0초의 범위를 보인다.

• 한국물환경학회지
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• 제30권2호
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• pp.166-174
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• 2014

Velocity gradient, G, a measure of the average velocity gradient in the fluid has been applied for complete mixing of chemicals in mechanical mixing devices. G values were calculated by the power input transferred to fluid in turbulent and transient range. Chemical reactions occur so fast that total mass transfer time required for even distribution of the chemicals determine the overall reaction time. The total mass transfer time is composed of the time for complete mixing through the reactor and for diffusion of the chemicals into the eddy. Complete mixing time was calculated by CFD (computer fluid dynamics) and evaluated by tracer tests in 2 liter jars at different rotating speeds. Turbulent range, Reynolds number above 10,000 in regular 2 liter jars occurred at revolution speed above 100 rpm (revolution per minute), while laminar range occurred at revolution speed below 10 rpm. A typical range of rotating speed used in jar tests for water and wastewater treatment was between 10 and 300 rpm, which covered both transient and turbulent range. G values supplied from a commercial jar test apparatus showed big difference from those calculated with power number specially in turbulent range. Diffusion time through eddy decreased 1.5 power-law of rotating speed. Complete mixing time determined by pumping number decreased increases in rotating speed. Total mass transfer time, finally, decreases as rotating speed increases, and it becomes 1 sec at rotating speed of 1,000 rpm. Complete mixing times evaluated from tracer tests showed higher than those calculated by power number at higher rotating speed. Complete mixing times, however, calculated by CFD showed similar to those of experimentally evaluated ones.