• International Journal of Internet, Broadcasting and Communication
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• 제16권2호
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• pp.169-178
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• 2024

This study aimed to investigate the effects of water depth and speed on the activation of lower muscles during squat exercises, utilizing electromyography(EMG). It involved ten male participants in there. Participants performed 30 squats over a minute at a speed of 60bpm and maximum speed squats until exhaustion within a minute. The Integrated electromyography(iEMG) readings for the rectus femoris showed statistically significant differences due to water depth and speed, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the biceps femoris also showed statistically significant differences, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the gastrocnemius showed statistically significant differences according to water depth and speed. However, the interaction effect of water depth and speed during squat exercises did not show a statistically significant difference. In contrast, the iEMG readings for the tibialis anterior demonstrated statistically significant differences, with a statistically significant interaction effect during squats. These findings suggest that water depth and speed positively influence the activation patterns of lower muscles. Therefore, appropriately tailored aquatic exercises based on water depth for individuals with musculoskeletal discomfort, including the elderly or those with physical impairments, can effectively reduce physical strain and enhance balance, as well as physical and perceptual aspects. It is concluded that such exercises could provide a safer and more effective method of exercise compared to ground-based alternatives.

• 한국유체기계학회 논문집
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• 제11권6호
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• pp.38-45
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• 2008

Development of high efficiency turbine with good performance is one of the main topics in the field of developing wave energy converter. For the development and improvement of the turbine performance, the effect of wave condition on the turbine performance should be considered in detail. Also, water depth is an important factor because incident wave power to the turbine is considerably influenced by the wave particle amplitude of motion and the amplitude is closely related with the water depth. Therefore, in this study, the effect of water depth on the performance of a direct drive turbine(DDT) for wave energy converter is investigated using the DDT which is installed in two types of wave channel. The experimental results show that the DDT captures more wave energy under the condition of relatively shallow water depth. When the water depth is shallow, the horizontal water particle amplitude of motion becomes wider and thus, the water power toward the turbine becomes larger.

• Ocean Systems Engineering
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• 제6권4호
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• pp.305-324
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• 2016

Wave load prediction at zero forward speed using finite depth Green function is a well-established method regularly used in the offshore and marine industry. The forward speed approximation in deep water condition, although with limitations, is also found to be quite useful for engineering applications. However, analysis of vessels with forward speed in finite water depth still requires efficient computing methods. In this paper, a method for analysis of wave induced forces and corresponding motion on freely floating three-dimensional bodies with low to moderate forward speed is presented. A finite depth Green function is developed and incorporated in a 3D frequency domain potential flow based tool to allow consideration of finite (or shallow) water depth conditions. First order forces and moments and mean second order forces and moments in six degree of freedom are obtained. The effect of hull flare angle in predicting added resistance is incorporated. This implementation provides the unique capability of predicting added resistance in finite water depth with flare angle effect using a Green function approach. The results are validated using a half immersed sphere and S-175 ship. Finally, the effect of finite depth on a tanker with forward speed is presented.

• 상하수도학회지
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• 제27권2호
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• pp.177-184
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• 2013

This study analyzed the hydraulic characteristics of a venturi flume with a circular cone using a 3-D numerical model which uses RANS(Reynolds-Averaged Navier-Stokes Equation) as the governing equation. The venturi flume with the circular cone efficiently measures the discharge in the low-flow to high-flow range and offers the advantage of accurate discharge measurements in the case of a low flow. With no influence of the tail-water depth, the stage-discharge relationship and the flow behaviors were analyzed to verify the numerical simulation results. Additionally, this study reviewed the effect of the tail-water depth on the flow. The stage-discharge relationship resulting from a numerical simulation in the absence of an effect by the tail-water depth showed a maximum margin of error of 4 % in comparison to the result of a hydraulic experiment. The simulation results reproduced the overall flow behaviors observed in the hydraulic experiment well. The flow starts to become influenced by the tail-water depth when the ratio of the tail-water depth to the total head exceeds approximately 0.7. As the ratio increases, the effect on the flow tends to grow dramatically. As shown in this study, a numerical simulation is effective for identifying the stage-discharge relationship of a venturi flume with various types of venturi bodies, including a venturi flume with a circular cone.

• 한국터널지하공간학회 논문집
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• 제10권1호
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• pp.49-57
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• 2008

라이닝 작용수압과 유입량은 지하수 수위 아래 혹은 하 해저터널 설계시 중요하게 고려되어야할 수리요소이다. 이 요소들은 수심, 심도, 수리경계조건의 영향을 받는다. 본 논문에서는 각 설계요소가 라이닝하중과 유입량에 미치는 영향을 수치해석적 도구를 이용하여 살펴보았다. 수심영향해석은 심도 30 m에 건설된 마제형 터널에 대하여 수심과 라이닝/지반 상대투수계수 비를 다양하게 변화시켜 조사하였고, 심도영향 해석은 수심 60 m의 터널에 대하여 심도 및 라이닝/지반 상대투수계수 비를 변화시켜 해석하였다. 해석결과 수리경계조건과 상관없이 수심 및 심도가 증가함에 따라 지반하중이 증가하였다. 이는 배수터널은 침투력의 영향으로, 비배수 터널은 정수압의 영향으로 수두가 증가함에 따라 지반하중이 증가함을 보여준 것이다. 수심, 심도의 증가에 따라 유입량은 선형적으로 증가하였으며, 라이닝/지반 상대투수계수비와 유입량관계는 펼쳐진 S자 곡선(stretched S-curve)형태로 나타남을 확인하였다.

• 한국농공학회지
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• 제45권4호
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• pp.55-65
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• 2003

Pilot study was conducted to examine the effects of ponded-water depth and reclaimed wastewater irrigation on paddy rice culture. For the ponded-water depth effect, three treatments of shallow, traditional, and deep water depths were applied, and each treatment was triplicated. The irrigation water for the treatment pots was an effluent from constructed wetland system for sewage treatment, while the control pot was irrigated with tap water kept traditional ponded-water depth. Irrigation water quantity varied with ponded-water depth as expected and drainage water quantity also varied similarly, which implies that shallow irrigation might save irrigation water and also reduce environmental impacts on downstream water quality. Rice growth and production were not significantly affected by ponded-water depth within the experimental condition, instead there was an indication of increased production in shallow and deep ponded-water depths compared to the traditional practice. Raising drainage outlet to the adequate height in paddy dike might be beneficial to save water resources within the paddy field. There was no adverse effect observed in reclaimed wastewater irrigation on the rice production, and mean yield was even greater than the control pots with tap water irrigation although statistically not significant. Water-saving irrigation by shallow ponded-water depth, raising the outlet height in diked rice paddy fields, minimizing forced surface drainage by well-planned irrigation, and reclaimed wastewater irrigation are suggested to save water and protect water quality. However, deviation from traditional farming practices might affect rice growth in long term, and therefore, further investigations are recommended before full scale application.

• 대한조선학회논문집
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• 제59권6호
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• pp.345-354
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• 2022

It is easy for a ship passing through confined waters to be exposed in dangers of collisions and grounding due to different hydrodynamic responses. Since marine accidents can cause significant impacts on environments, global economy, and human lives, it is necessary to study the effect of shallow water on hydrodynamic performance of a ship. In this paper, the effect of water depth on resistance performance was investigated using CFD analysis as an initial study for improving navigational safety of a large container ship under confined waters. After a CFD set-up for deep water condition was validated and verified by comparing CFD analysis with model test results, CFD calculations according to ship speed and water depth were conducted. The features were investigated in terms of tendency and physical knowledge related to resistance performance. The increase of resistance due to shallow water effect was reviewed with empirical formula suggested from SWABE JIP. Speed loss due to shallow water effect was additionally reviewed from estimated delivered power according to ship speed and water depth.

• 대한조선학회지
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• 제13권1호
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• pp.11-16
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• 1976

The effect of the bow shape on the ship motion response in longitudinal regular waves of water of finite depth is investigated by employing the strip theory. The two-dimensional hydrodynamic forces(added mass and damping) were calculated by close-fit method for water of finite depth. The models for investigation are U and V bow ship forms of block coefficient 0.8 with constant after body which were used by Yourkov [2] and recently by Kim [3] for their deep water investigations. The following results are obtained by the present numerical experiments. (1) It is confirmed that the damping coefficient of the V-bow ship is greater than that of U-bow ship and in consquence the amplitude of heave and pitch of V-bow ship is smaller than that of U-bow ship among longitudinal regular head waves in water of finite depth (2) The merit of the V-bow ship on the motion damping is more significant in heave than in pitch, and is decreasing with the shallowness of water depth. (3) The change of bow form gives little effect on the wave exciting force and moment compared with the motion responce.

• 대한조선학회지
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• 제12권2호
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• pp.59-66
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• 1975

Recently, as the dimensions of energy carriers increase, especially in draft, a reliable prediction of the ship motions at finite depths of water becomes necessary. The purpose of this paper is to probe the effect of finite water depth on the hydrodynamic forces and ship motions, particularly heave and pitch, in longitudinal regular head waves, by comparing the experimental value of Freakes and Keay with the author's theoretical value obtained by applying the modified strip theory to the Mariner class ship. It is confirmed that generally the hydrodynamic coefficients in the equations of motion increase with decreasing water depth, and the wave exciting forces and moments decrease with decreasing water depth. Amplitudes of heave and pitch in longitudinal regular head waves decrease as the water depth in the range where the length of the incident wave is comparatively long. The effects of Froude Number on the hydrodynamic coefficients increase with decreasing water depth and is more noticeable in the case of heave than pitch. In heave, generally the discrepancy between the experimental value and the theoretical value is relatively small in the case of $F_n=O$, but it is very large in the case of $F_n=0.2$. It is considered that the trend stems from the ignorance of the three dimensional effect and the other effects due to shallowness of water on the hydrodynamic coefficients in the theoretical calculation. An extension of methods for calculating the two dimensional hydrodynamic forces to included the effect of forward speed should be recommended. It is required that more experimental works in finite water depths will be carried out for correlation studies between the theoretical calculation, according tp modified strip theory, and model experiments.

• 한국방재학회 논문집
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• 제9권3호
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• pp.107-115
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• 2009

일반적으로 래버린스 위어는 월류부의 평면형상을 변화시켜 월류 길이를 증가시킨 위어이다. 래버린스 위어는 월류량 증대 및 수심유지에 활용될 수 있으며, 수질개선에도 효과가 있다. 그러나 수공구조물로써 기능 및 설계조건을 고려할 수 있는 수심유지 효과에 관한 연구는 상대적으로 부족한 실정이다. 본 연구의 목적은 삼각형 래버린스 위어의 수심유지효과 범위를 제시하여 보다 효율적인 삼각형 래버린스 위어 설계가 가능토록 하는데 있다. 또한, 수심유지 효과는 수리모형실험 및 3차원 수치모형인 FLOW-3D를 이용하여 분석하였다. 이러한 결과, 본 연구에서는 삼각형 래버린스 위어는 시점부까지 전 범위에서 수심유지효과가 나타났으며, 위어 종점부까지 수심이 유지되는 범위($H_t/P=0.08\sim0.27$)를 정량적으로 제시하여 효율적인 설계가 가능하도록 하였다.