• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1848-1853
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• 2000

Cause and the elimination method for the chattering phenomena were investigated the check valve attached exit of the auxiliary cooling water pump at a korean nuclear powerplant. From the site experiment and numerical calculation the incident angle of the disk was so small that it was not able to produce the lifting force to overcome the component of disk weight. Moreover, it turned out that the installed position was not symmetric for the secondary vortical flow generated inside the elbow, so that the flow structure had strongly unstable flow characteristics. From this technical support, the tapping noise and the chattering phenomena were eliminated exactly by changing the incidence angle of the valve disk and installed position of the check valve.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.917-922
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• 2008

In order to reduce energy consumption, secondary controlled system has been applied to many types of equipments. In lifting equipments or press machines using hydraulic cylinder, a hydraulic transformer is used as a control component instead of a valve for motion control and a component for recovering potential energy of load. The transformer is combination of a variable displacement pump/motor as a secondary controlled element and a fixed displacement pump/motor. Based on the nominal model derived from mathematical model, the feedback type two-degree-of-freedom controller is designed and implemented. From simulation results, the disturbances including nonlinear friction torque, leakage flow and load force can be compensated and good positioning accuracy is obtained. It show that the proposed controller is effective.

• 수산해양기술연구
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• 제16권2호
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• pp.61-67
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• 1980

Previously, we had experimented on the model of stow net under the various combination including water velocity, spherical floats and elevating floats with the shearing hoods instead of the upper beam, however we couldn't concern with their characteristics. Spherical floats maintain their buoyancy at the same level when the speed increases, only the drag increases and effects some reduction in the fishing height. To eliminate this shortcoming, floats have to some hydrodynamic lifting force which increases with increasing speed. Phillips float with a dish-shaped metal plate welded on at the lower part and synthetic upthrusting float were used for the experiment to compare with their characteristics. Six kinds of model shearing hood depend on the angle of attack were used to test the characteristic of the shearing hood. According to their results, when the angle of attack is 30\ulcorner, the lift and drag coefficient reveal 1. 36, 0.84 respectively. And also experimented on the 5X8cm shearing hood to investigate the suitability for the model stow net.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2004년도 유체기계 연구개발 발표회 논문집
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• pp.492-500
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• 2004

The purpose of this study is localization of safety relief valves fur Nuclear Service through technical development with overall design, fabrication, inspection, capacity certification test and functional qualification test of safety relief valves in accordance with KEPIC MN Code(or ASME Sec.III ). The safely relief valve is the important equipment used to protect the pressure vessel, the steam generator and the other pressure facility from overpressure by discharging the operating medium when the pressure of system is reaching the design pressure of the system. But we're depending on technology of the other country up to the present time. Because we don't have our own technologies, we have been spent the great time and money on installing and repairing safety relief valve at nuclear power plant. Therefore we have to achieve the development of safety relief valves for Nuclear Service with our own technologies.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.177-184
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• 2017

The Coanda effect is the phenomenon of a fluid jet to stay attached to a curved surface; when a jet stream is applied tangentially to a convex surface, lift force is generated by increase in the circulation. The Coanda effect has great potential to be applied practically applied to marine hydrodynamics where various lifting surfaces are being widely used to control the behavior of ships and offshore structures. In the present study, Numerical simulations and corresponding experiments were performed to ascertain the applicability of the Coanda effect to a horn-type rudder. It was found that the Coanda jet increases the lift coefficient of the rudder by as much as 52% at a jet momentum coefficient of 0.1 and rudder angle of $10^{\circ}$.

• Ocean and Polar Research
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• 제41권1호
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• pp.19-34
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• 2019

The present study obtained universal mathematical models of all elements and characteristics regarding hook and line fishing systems. To describe the hook and line fishing systems on site we used three kinds of coordinate systems: the earth based coordinate system, natural coordinate system, and flow (velocity) coordinate system. Mathematical models presented in this article allow us to define the shape of the fishing gear, the tension of the rope at different points, hydrodynamic resistance, diameter of the hook's wire, immersion depth of the fishing hooks, distance from hooks to the ground and the required lifting force of the floats. These models allow for the performance of computer simulations regarding any kinds of hook and line gears in still water or water where flow occurs.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제27권4호
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• pp.232-244
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• 2023

The unsteady dynamics of the starting flow of a flat plate is studied by using a vortex shedding model. The model describes the body and separated vortex from the trailing edge of the plate by vortex sheets, retaining a singularity at the leading edge. The model is applied to simulate the flow of an accelerated plate for small angles of attack. For numerical computations, we take two representative cases of the translational velocity of a plate: impulsive translation and uniform acceleration. The model successfully demonstrates the formation of wakes shed from the plate. The wake behind the plate is stronger for a larger angle of attack. Predictions for the lifting force from the model are in agreement with results of Navier-Stokes simulations.

• 한국컴퓨터정보학회논문지
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• 제23권6호
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• pp.43-49
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• 2018

In this paper, we propose a taping therapy as effective intervention for patients with the back pain. The purpose of this study is to investigate the effects of taping intervention on the VAS evaluated score and he muscular activation degree among 119 paramedics with musculoskeletal injury. In order to achieve the purpose of the study, data was collected from 15 paramediecs in the paramedics department of 3 fire stations under J city's fire defense headquarters. The following results can be obtained by measuring the subjective, the back muscle strength and the buckling-anteflexion before and after the taping for 15 119 paramedics. Through the verification experiment of taping effect to paramedics during the stretcher lifting in this study the VAS evaluated score for the backache are $1.67{\pm}0.62$ before and $0.80{\pm}0.68$ after the application of taping which show statistically significant decrease(p<0.05). In the experimentof joint operation range the measured buckling anteflexion length are $14.62cm{\pm}4.89$ before and $16.41cm{\pm}4.11cm$ after the application of taping which show statistically meaningful difference(p<0.05). In the comparison of muscle activity about paramedics erector spinae(ES) shows the meaningful decrease and external obliques(EO) displays the significant increase. Erector spinae(ES) and internal obliques(IO) show the increasing trend in the muscle activity although they are not significant. the muscle activity for the erector spinae is lowered so that the contribution to the force required for the extensor during the stretcher lifting is resultingly reduced to have the effects of enhancing the activity of abdominal muscles.

• Safety and Health at Work
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• 제10권1호
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• pp.3-20
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• 2019

This review aimed to identify risk factors for occupational accidents and illnesses among young workers in the Nordic countries and to attain knowledge on specific vulnerable groups within the young working force that may need special attention. We conducted a systematic review from 1994 to 2014 using five online databases. Of the 12,528 retrieved articles, 54 met the review criteria and were quality assessed, in which data were extracted focusing on identifying occupational safety, health risk factors, and vulnerable groups among the young workers. The review shows that mechanical factors such as heavy lifting, psychosocial factors such as low control over work pace, and organizational factors such as safety climate are all associated with increased injury risk for young Nordic workers. Results show that exposures to chemical substances were associated with skin reactions, e.g., hand eczema. Heavy lifting and awkward postures were risk factors for low back pain, and high job demands were risk factors for mental health outcomes. The review identified young unskilled workers including school drop-out workers as particularly vulnerable groups when it comes to occupational accidents. In addition, apprentices and young skilled workers were found to be vulnerable to work-related illnesses. It is essential to avoid stereotyping young Nordic workers into one group using only age as a factor, as young workers are a heterogeneous group and their vulnerabilities to occupational safety and health risks are contextual. Politicians, researchers, and practitioners should account for this complexity in the education, training and organization of work, and workplace health and safety culture.

• 한국CDE학회논문집
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• 제15권5호
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• pp.383-392
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• 2010

The purpose of this study is to develop three Judo-doll systems for enhancement of Judo's performance. Traditional Judo training requires a human training partner. Unfortunately it is not always easy to find one. Multifunctional Judo-doll training system has therefore been developed, and is described here. The system consists of a dummy, a power generating mechanism, and kinematic links. The power-generating mechanism generates forces similar to those of a human, by adjusting deadweights and controlling powderbrake's forces. The powderbrake force is controlled by the microprocessor according to the exercise scenario. The kinetic links, which mimic a human training partner's motions, has been developed based on a $Vicon^{TM}$ system's analysis of the movement of human training partners. This mechanism whose name is "L link-wire" consists of L type links, wire, roller, and dead weight. This mechanism generates the force that leads the link to the neutral position regardless the link is pushed or pulled. The lifting mechanism that lifts the doll when the one-armed shoulder throw skill is applied is also developed. A 32-bit microprocessor controls the whole system; it reads the loadcell data, controls the electromagnetic force, and communicates with a PC via Bluetooth. The training history, including loadcell data, date, and training time, is stored in the PC for analysis. This training system can be used to enhance the Judo performance of any self training player.