• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.5
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• pp.472-481
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• 2008

In this study hydraulic experiment was carried out to investigate the flow characteristics in the submerged outlet structure of Boryeong power plant and the efficiency of bubble reduction by installing horizontal porous plate in the outlet structure. The cross-sectional mean velocity in the submerged outlet structure was smaller than 1 m/s, the target value at the design stage to prevent bubble outflow to the open sea area. In addition, it was found that the maximum depth of bubble penetration is reduced 30 to 50% by installing the horizontal porous plate at the second falling location in the submerged outlet structure. It is expected that the total bubble amount entrained in the water will be most efficiently reduced by installing square-hole-shape porous plate of 20 cm hole size and making its central section as non-porous structure to dissipate the energy of falling water.

• The Korean Journal of Physiology
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• v.9 no.2
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• pp.17-22
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• 1975

Adult nonpregnant female rabbits were subjected to the study of the effects of carbon monoxide inhalation on the uterine motility. Animals were anesthetized with intravenous injection of nembutal, 35 mg/kg, and the uteri were exposed. Polyethylene tubing which had a small hole near the blind tip was inserted in the loop and normal saline was infused at a constant rate of 1.5 ml/min. On the other end of the loop, an outlet of fluid was made. When a peristaltic wave proceeded to the hole, a rise of the pressure was ensued and it was transmitted to the pressure transducer, making an upward deflection of the recording pen on the physiograph. Carbon monoxide, 1,000 ppm in the concentration, was inhaled through a tracheal cannula for 30 minutes, following fresh air for 30 minutes. In some cases, pure oxygen was also supplemented for another 30 minutes. Uterine motility was expressed in terms of the impulse that was the time integral of the pressure and of the frequency of the peristaltic waves. The results obtained were as follows. 1. When 1,000 ppm carbon monoxide was inhaled for 30 minutes, the impulse dropped to $72{\pm}16.5%$ and the frequency to $75{\pm}22.7%$ of the values obtained before the gas administration. 2. By fresh air for 30 minutes, the impulse and the frequency restored to $77{\pm}25.7%$ and $92{\pm}21.1%$, respectively. 3. By the supplement of pure oxygen for 30 minutes, no remarkable improvement were revealed, showing $89{\pm}35.2%$ in the impulse and $91{\pm}10.8%$ in the frequency, respectively. 4. There was an appreciable discrepancy in the recovery courses of the impulse and the frequency, suggesting different mechanisms attributable to the alteration by carbon monoxide inhalation.

• The Journal of the Korea Contents Association
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• v.7 no.4
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• pp.30-38
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• 2007

In this paper, UHF band RFID reader antenna using filbert curve fractal structure and adding the partially grounded plane at the bottom of antenna, which has a resonant frequency at 910MHz, is proposed. Input impedance of antenna is matched with the feed line of 50ohm by varying the length and width of line segment making up the antenna, and by moving the position of via hole. The gain and directivity of antenna is enhanced as varying the dimension of the partially grounded plane and adding the line segment. The size of fabricated antenna is $68mm\times68mm$. The impedance band width(VSWR<2) is $882\sim942MHz$. The return loss and the gain of fabricated antenna are -18.2dB, 5.3dBi at 910MHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.681-686
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• 1999

In this study, the gain characteristics of the strained structures for SOA were calculated numerically and the optimized strained quantum well for the polarization-insensitive SOA was obtained. The structures used in this calculation were consisted of one, two, and three GaAs Delta layers respectively in the GaInAs(160 $\AA$) well. Moreover the third one was calculated by changing from one mono-layer to three mono-layers in the thichless of GaAs delta layers. This structure enhances the TM mode gain coefficient with good efficiency because the light-hole band is lifted up whereas the heavy-hole band is lowered down. Additionally, The structure of the 3 GaAs delta layers(1 mono layer thickness) shows 3dB gain bandwidth of 85nm in 1.55um wavelength system. This study is expected to be used in making a wide band and polarization-independent semiconductor optical amplifier practically.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.340-344
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• 2008

The importance of the more efficient cogeneration system is emphasized. Also the more clean energy is needed at recent energy system. The cogeneration system using Lean burn engine is more preferred to the system using Rich burn engine because of the electrical efficiency. Although the cogeneration system using Lean burn engine is economically preferred, because of the NOx emission level, the system using Rich burn engine with 3-way catalyst can only be used in Korea. The NOx regulation level is 50ppm at oxygen level 13%. The cogeneration hybrid system using Lean burn engine is up to be optimized because of the large amount of the extra-fuel at the after-burner system. The after-burner system at different concept was applied. The reduction time for the activation temperature of the DeNOx catalyst was achieved by making a hole between the combustor and boiler. Because of the lowered fuel consumption, the lowered temperature level was optimized by blocking the hole of the boiler The optimized cogeneration hybrid system consumes $76Nm^3/h$ LNG to produce 150kW electricity compared to before optimization $103Nm^3/h$ LNG. The system was accurately evaluated and the result is following ; 90% total efficiency, below 10 ppm NOx, 50ppm CO, 25ppm HC. The cogeneration hybrid system can meet the current NOx level and exhaust gas regulation. It can achieve the clean combustion gas and efficient cogeneration system.

• Journal of the Korean institute of surface engineering
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• v.45 no.5
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• pp.181-187
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• 2012

The Friction Stir Welding (FSW) has mainly been used for making butt joints in Al alloys. The development of Friction Stir Lap Welding (FSLW) would expand the number of applications. In this study, microstructures and mechanical properties of FSLW in A5052 alloy were investigated under varying rotating speed and probe length. Investigating the characteristics as FSLWed conditions were as below ; Failure Maximum load by shear fracture was increased proportional to the width of joint area, which was increased by input heat, stirring intensity in the case of 2.3 mm probe length. Tensile fracture occurred, and maximum load was determined due to side worm hole of joint area and softening of microstructure in the case of 3.0 mm probe length. In the case of 3.7 mm probe length, material hook and bottom worm hole were appeared at the end interface of joint area. The most sound FSLW condition with no defects was 3.0 mm probe length and 1500 rpm-100 mm/min. No defects were showed in 1500 rpm-100 mm/min and 1800 rpm-100 mm/min, but Vickers microhardness distribution in TMAZ/HAZ which was fracture zone was lower in 1800 rpm-100 mm/min than in 1500 rpm-100 mm/min. In this condition highest tensile strength, 215 MPa (allowable rate 78% of joint efficient) was obtained.

• The Journal of Korean Physical Therapy
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• v.30 no.6
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• pp.234-238
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• 2018

Purpose: Aim of this study was to investigate whether there are ipsilateral motor deficits for visuospatial accuracy and fine movements by making a comparison between stroke patients and healthy subjects. We examined whether ipsilateral motor deficits are influenced by the level of functional movements and muscle strength of the upper and lower extremities of the affected side. Methods: Thirty post-stroke subjects and 20 normal aged matched subjects were recruited. Outcome measures for less-affected side were the tracking task and nine-hole pegboard test. Fugl-Meyer test and motricity index were applied for the measurement of functional movements and muscle strength of affected side. Results: Tracking task and nine-hole pegboard test was significantly different between control and experimental group. In terms of accuracy index according to tracking, the experimental group showed a lower accuracy index in the MCP joint than the control group. However, there were no significant difference relation between the level of motor function of the affected side and the motor deficit level of ipsilateral side. Conclusion: Ipsilateral motor deficits may have significant clinical implications. It needs to be noted that although many patients, families, and medical staff are focused only on motor deficits of the affected side, motor deficits of the sound side can cause difficulties in daily living movements requiring delicate movements. In addition, there was no significant correlation between the level of motor function of the affected side and motor deficits of the sound side.

• Steel and Composite Structures
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• v.44 no.2
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• pp.199-210
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• 2022

This study build finite element analysis (FEA) models describing the bending events of coiled tubing (CT) at the wellhead and trips into the hole, accurately provide the state of stress and strain while the CT is in service. The bending moment and axial force history curves are used as loads and boundary conditions in the diametrical growth models to ensure consistency with the actual working conditions in field operations. The simulation diametrical growth results in this study are more accurate and reasonable. Analysis the factors influencing fatigue and diametrical growth shows that the internal pressure has a first-order influence on fatigue, followed by the radius of the guide arch, reel and the CT diameter. As the number of trip cycles increase, fatigue damage, residual stress and strain cumulatively increase, until CT failure occurs. Significant residual stresses remain in the CT cross-section, and the CT exhibits a residual curvature, the initial residual bending configuration of CT under wellbore constraints, after running into the hole, is sinusoidal. The residual stresses and residual bending configuration significantly decrease the buckling load, making the buckling and buckling release of CT in the downhole an elastic-plastic process, exacerbating the helical lockup. The conclusions drawn in this study will improve CT models and contribute to the operational and economic success of CT services.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.4
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• pp.21-31
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• 2001

When an oil-spilling accident occurs at sea, it is of the primary importance to predict the amount of oil leakage for the swift response and decision-making. The simplest method of oil-leakage estimation is based on the hydrostatic pressure balance between oil inside the tank and seawater outside of leakage hole, that is the so-called Torricelli equilibrium relation. However, there exists discrepancy between the reality and the Torricelli relation, since the latter is obtained from the quasi-steady treatment of Bernoulli equation ignoring viscous friction. A preliminary experiment has been performed to find out the oil-leaking speed and shape. Soy-bean oil inside the inner tank was ejected into water of the outer tank through four different leakage holes to record the amount of oil leakage. Furthermore, a CFD (Computational Fluid Dynamics) method was utilized to simulate the experimental situation. The Wavier-Stokes equations were solved for two-density flow of oil and water. VOF method was employed to capture the shape of their interface. It is found that the oil-leaking speed varies due to the frictional resistance of the leakage hole passage dependent on its aspect ratio. The Torricelli factor relating the speed predicted by using the hydrostatic balance and the real leakage speed is assessed. For the present experimental setup, Torricelli factors were in the range of 35%~55% depending on the aspect ratio of leakage holes. On the other hand, CFD results predicted that Torricelli factor could be 52% regardless of the aspect ratio of the leakage holes, when the frictional resistance of leakage hole passage was neglected.

• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.168-178
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• 2017

In order to prevent major and chemical accidents, some of the plants which would like to install and operate hazard chemicals handling facilities must submit Off-site Consequence Analysis due to recent arisen leak accidents since 2015. A lot of chemical industrials choose gas detectors as mitigation equipment to early detect gas vapor. The way of placement of gas detectors has two methods; Code-based Design(CBD) and Performance-based Design. The CBD has principles for gas detectors to be installed with consideration for the place that is expected to accumulate gas, and the leak locations according to legal standards and technical guidelines, and has a possibility to be unable to detect by these rules to locate gas detectors by vapor density information. The PBD has two methods; a Geographic Method and Scenario based Method. The Scenario-based Method has been suggested to make up for the Geographic Coverage Method. This Scenario-based Method draw the best optimum placement of gas detectors by considering leak locations, leak speed information, leak directions and etc. However, the domestic placement guidelines just refers to the CBD. Therefore, this study is to compare existing placement location of gas detectors by the domestic CBD with placement locations, coverages and the number of gas detectors in accordance with the Scenario-based Method. Also this study has measures for early detecting interest of Vapor Cloud and suitable placement of gas detectors to prevent chemical accidents. The Phast software was selected to simulate vapor cloud dispersion to predict the consequence. There are two cases; an accident hole size of leak(8 mm) from API which is the highst accident hole size less than 24.5 mm, and a normal leak hole size from KOSHA Guide (1.8 mm). Detect3D was also selected to locate gas detectors efficiently and compare CBD results and PBD results. Currently, domestic methods of gas detectors do not consider any risk, but just depend on domestic code methods which lead to placement of gas detectors not to make personnels recognize tolerable or intolerable risks. The results of the Scenario-based Method, however, analyze the leak estimated range by simulating leak dispersion, and then it is able to tell tolerable risks. Thus it is considered that individuals will be able to place gas detectors reasonably by making objectives and roles flexibly according to situations in a specific plant.