• Ocean Systems Engineering
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• v.9 no.1
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• pp.1-19
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• 2019

Latching control was applied to a Wave Energy Converter (WEC) buoy with direct linear electric Power Take-Off (PTO) systems oscillating in heave direction in waves. The equation of the motion of the WEC buoy in the time-domain is characterized by the wave exciting, hydrostatic, radiation forces and by several damping forces (PTO, brake, and viscous). By applying numerical schemes, such as the semi-analytical and Newmark ${\beta}$ methods, the time series of the heave motion and velocity, and the corresponding extracted power may be obtained. The numerical prediction with the latching control is in accordance with the experimental results from the systematic 1:10-model test in a wave tank at Seoul National University. It was found that the extraction of wave energy may be improved by applying latching control to the WEC, which particularly affects waves longer than the resonant period.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.282-290
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• 2015

In this study, a latching control technology, proposed by Sheng et al.(2015), was applied in order to maximize the extraction efficiency of WEC (Wave Energy Converter), which is the heaving buoy coupled with linear electric generator. The latching control is the phase-control technique for improving the wave energy conversion with appropriate latching duration of keeping the buoy fixed. From the time-domain analysis in regular waves, the latching control technology can significantly improve the heave velocity and extracted power, even though the resonance condition is not satisfied. By using the latching control technology, the draft of buoy as well as the required PTO damping force can be significantly reduced along with increased extracted power, which is a big advantage in manufacturing the WEC.

• Perspectives in Nursing Science
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• v.10 no.2
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• pp.97-110
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• 2013

Purpose: This study sought to identify how initiating breastfeeding soon after birth affected breastfeeding practice. Methods: The subjects were mothers and newborns in Seoul's S. University Hospital maternity unit who elected to breastfeed. They were divided into an experimental group, which practiced an "early latching-on program" (latching-on within 30 minutes after birth), and a control group, which did not. Both groups' daily frequencies of breastfeeding and supplementary-glucose or bottle feeding were recorded. Results: The correlation between socio-demographic and medical characteristics and the breastfeeding rate was examined; 3 variables showed statistical significance: neonatal health anomaly, Apgar score after 1 minute, and Apgar score after 5 minutes. The difference in breastfeeding rates between the two groups was clear: the experimental group's rate was 1.93, while the control group's was 3.76 (t-statistic difference: 14.865), with the experimental group's rate during hospitalization being twice that of the control group (73.3% and 32.6%, respectively). Multiple regression analysis assessing the influence of the latching-on program yielded a t-statistic of -4.735 and a p-value of .000, indicating statistical significance. Conclusion: An early latching-on program's positive effect on the breastfeeding practice of mother's of newborns was demonstrated. Therefore, an early latching-on program could be a practical and effective nursing intervention for after mothers give birth.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.4
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• pp.291-297
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• 2015

The wave spectrum was generated from wave data measured at the Chagwi-do site in Jeju, where a 10MW class floating wave-offshore wind hybrid power generation system will be installed. The latching control technology (Sheng et al.[2015]) was applied in order to improve the extracted power from WEC (Wave Energy Converter), which is heaving in corresponding irregular waves. The peak period as a representative value of irregular waves was used when we determined the latching duration. From the numerical results in the time-domain analysis, the latching control technology can significantly improve the extracted power about 50%.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.86-101
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• 2021

This study examined the effects of buoy shape and Nonlinear Froude-Krylov force (NFK) on a heaving-buoy-type Wave Energy Converter (WEC). Based on the Maclaurin expansion, the theoretical solutions of the NFK were derived for three different buoy shapes; hemispheric buoy, circular vertical cylinder, and truncated conical cylinder. A hydraulic power take-off system was adopted, and the latching control strategy was applied to maximize the extracted power from the WEC. The nonlinear effects of the Froude-Krylov force and restoring force on the heaving point absorber were investigated by comparing the heave Response Amplitude Operator (RAO) and time-averaged power extraction. The results showed that the conventional linear analyses were overestimated by up to 50% under the high amplitude wave condition. The latching control strategy was the most effective when peak wave period of regular or irregular wave was 0.4-0.45 times the heave natural period of the buoy.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.56-64
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• 2011

In this paper, the characteristics of LCL set-up parameters for the satellite load distribution are analyzed under the electrical system environment, implemented the LCL circuits and evaluated the performance and its behaviour. Recently, it is implemented the load distribution circuit by latching current limiter(LCL) rather than conventional fuse and relay for the protection of the satellite power system from a fault load. The LCL circuit is composed of the electrical components, not mechanical parts with the fuse and relay. When detected the over current on a fault load, it is activated to maintain the trip-off level for set-up time and then cut-off the load power by the active control. It is more flexible and provided a chance to reuse of the load in case of temporarily event, but the fuse and relay can't be used again after activating due to the physical disconnection. However, for implementation of LCL circuit, it should be carefully considered the behavior of the LCL circuit under the worst electrical system environment and applied it to define the set-up parameters related with over-current inhibition.

• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.235-241
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• 2017

Purpose: It is to develop an agricultural three-directional dumping vehicle that can help farmers reduce intensive labor when carrying heavy loads and for easy dumping. In addition, a novel mechanism was applied for controlling the direction of the tilting cargo box by using a single hydraulic cylinder and simple apparatus. The overturning safety was analyzed to provide safe-use ground slope region of the vehicle to be used at upland fields and orchards. Methods: The developed three-directional dumping vehicle was constructed using a cargo box, vehicle frame, driving components, lifting components, and controller. The novel mechanism of controlling the dumping direction involves the operation of two latching bars, which selectively release or collapse the connecting edge between the vehicle frame and cargo box. A multibody dynamics analysis software (RecurDynV8R5) was used to determine the safe-use ground slope area when tilting the cargo box at slopes. A computer analysis was conducted by increasing the ground slope while rotating the vehicle when the cargo box comprised loads of 300 and 500 kg and stacking heights of 40 and 80 cm, respectively. Results: The three-directional dumping vehicle was successfully manufactured, and the cargo box was tilted at $37^{\circ}$ and $35^{\circ}$ for dumping forward and sideways. The latching bars were manually and selectively collapsed with the vehicle frame to control the dumping direction. When forward dumping, the safe-use ground slope was over $20^{\circ}$ in all vehicle directions and loaded conditions. Conclusions: A three-directional dumping vehicle was developed to reduce labor-intensive work in the farming environment. The user can easily control the dumping direction by using the control panel. The vehicle was safe to be used in most of the Korean upland fields and orchards (area over 96%) for the forward dumping.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2655-2657
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• 2005

When a fault relating to the urgent alarm occurs, we must prevent control rods from dropping and make one of two grippers in Control Rod Drive Mechanism (CRDM) grip the drive rod taking a control rod assembly. To enhance the reliability of holding control rods, we order two grippers to hold the drive rod. This action is called the double holding. In the middle of the movement of the drive rod, the latching of the drive rod can cause friction between a gripper and the drive rod. This state may give damage to both the gripper and the drive rod. In this paper, we have devised the method which can have two grippers hold the drive rod more stably, without damaging the equipment.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.294-298
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• 2001

Satellite propulsion system is employed for orbit transfer, orbit correction, and attitude control. The monopropellant feeding system in the low-earth-orbit satellite blowdowns fuel to the thrust chamber. The thrust produced by the thruster depends on fuel amount flowed into the combustion chamber. If the thruster valve be given on-off signal from on-board commander in the satellite, valve will be opened or closed. When the thrusters fire fuel flows through opened thruster valve. Instantaneous stoppage of flow in according to valve actuation produces transient pressure due to pressure wave. This paper describes transient pressure predictions of the KOMPSAT2 propulsion system resulting from latching valve and thrust control valve operations. The time-dependent set of the fluid mass and momentum equations are calculated by Method of Characteristics (MOC).

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.555-558
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• 2003

When a fault relating to the urgent alarm occurs, we must prevent control rods from dropping and make one of two grippers in Control Rod Drive Mechanism (CRDM) grip the drive rod laking a control rod assembly. If a gripper with any problem is ordered to grip the drive rod, the gripper which cannot latch the rod stably will fail to take the rod. On the purpose of escaping this bad case, we order two grippers to hold the drive rod and enhance the reliability of holding control rods. This action is called the double hold. In the middle of the movement of the drive rod, the latching of the drive rod can cause friction between a gripper and the drive rod. This state may give damage to both the gripper and the drive rod. In this paper, we have devised the method which can have two grippers hold the drive rod more stably, without damaging the equipment.