• Fire Science and Engineering
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• v.29 no.3
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• pp.6-12
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• 2015

Indoor hydrant facilities are used to fight initial fires before more intense fire extinguishing activities. Fire extinguishing facilities should ensure good fire extinguishing performance and the safety of users. Indoor hydrant facilities are mostly installed in buildings and facilities, and users must manipulate valves, hoses, and nozzles manually. When the discharge pressure is higher than 0.70 MPa, there is a high possibility that problems with manipulation and hose breakdown can occur. To prevent these problems, a method to attach orifice-type decompression valves to the angle valves of indoor hydrant discharge outlets has frequently been used for decompression methods. However, the decompression performance was reduced due to structural problems of the decompression valves over time. Accordingly, based on three-stage initial pressures, applicable pressure ranges were selected by measuring the decompression performance according to the diameter of the decompression orifices. Based on the data, stable decompression valve models are proposed. These models have the lowest decrease in decompression performance, regardless of time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.175-181
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• 2019

In the case of a conventional single stage decompression regulator used for large depressurization in the hydrogen fuel cell system of a fuel cell electric vehicle (FCEV), problems can arise, such as pulsation, slow response, hydrogen brittleness, leakage, high weight, and high cost due to high decompression. Most of these problems can be overcome easily using two decompression mechanisms (two-stage structures). In addition, a wide outlet-pressure control range can be secured if an electronic solenoid is applied to the second decompression. Accordingly, it is necessary to improve the precision of the outlet pressure of a two-stage pressure-reducing regulator and develop techniques, such as leakage prevention, durability, light weight, and price reduction. Therefore, to improve the outlet pressure accuracy and prevent leakage, the structural part before and after decompression to improve the air tightness were divided and the analysis was carried out assuming that the valve part was closed (open ratio: 0%) after each initial internal pressure application.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.9-14
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• 2011

The expansion work that is wasted through the irreversible expansion through the PC valve of decompression process of the natural gas governor station can be recovered by replacing the process by an isentropic expansion. The energy and exergy analyses for the two decompression process models of power producing and current decompression process model are presented. Analysis results showed that the exergy by gas supply is 56.29%, the exergy by producing power is 32.12 % in case of preheating system and 22.52% in case of non-preheating system. The dead exergy at the PCV is generated much more network. As these results, the usefulness of exergy analysis is verified.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.12
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• pp.31-39
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• 1999

Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.45-50
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• 2013

Closed-loop J-T (Joule-Thomson) refrigeration cycle is advantageous compared to common open loop $N_2$ decompression system in terms of nitrogen consumption. In this study, two closed-loop pure $N_2$ J-T refrigeration systems with sub-atmospheric device for cooling High Temperature Superconductor (HTS) power cable are investigated. J-T cooling systems include 2-stage compressor, 2-stage precooling cycle, J-T valve and a cold compressor or an auxiliary vacuum pump at the room temperature. The cold compressor and the vacuum pump are installed after the J-T valve to create sub-atmospheric condition. The temperature of 67 K is possible by lowering the pressure up to 24 kPa at the cold part. The optimized hydrocarbon mixed refrigerant (MR) J-T system is applied for precooling stage. The cold head of precooling MR J-T have the temperature from 120 K to 150 K. The various characteristics of cold compressor are invstigated and applied to design parameter of the cold compressor. The Carnot efficiency of cold compressor system is calculated as 16.7% and that of vacuum pump system as 16.4%. The efficiency difference between the cold compressor system and the vacuum pump system is due to difference of enthalpy change at cryogenic temperature, enthalpy change at room temperature and different work load at the pre-cooling cycle. The efficiency of neon-nitrogen MR J-T system is also presented for comparison with the sub-atmospheric devices. These systems have several pros and cons in comparison to typical MR J-T systems such as vacuum line maintainability, system's COP and etc. In this paper, the detailed design of the subcooled $N_2$ J-T systems are examined and some practical issues of the sub-atmospheric devices are discussed.

• Journal of ILASS-Korea
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• v.13 no.4
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• pp.212-219
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• 2008

To develop the twin-fluid atomizer having the excellent performance of painting, the spray characteristics of how a wide area can be painted efficiently by one time spraying were studied in this paper. Spray phenomena are affected by the many factors determining the spray field such as the spraying pressure of gas, the spraying pressure and viscosity of liquid paints, the opening duration of needle valve, the design dimension of nozzle, and so on. As the results of experiments, these factors affecting on spray characteristics were suggested as followings; 1) The optimum spraying pressure of gas was $0.015{\sim}0.02\;kPa$, and the appropriate spraying pressure of liquid paint was 0.01kPa, In these situations, the setting up pressures must be compensated as much as the losing amount of pressure because a decompression occurred when operating valves. 2) The duration of opening the needle valve must be sustained for $1{\sim}2$ seconds to inject gas after spraying the liquid paint. This operating of the needle valve was necessary to avoid the affect on the changing of liquid column length, and to prevent the droplet deposit at the initial time of spraying. 3) The spray tip penetration was gained form the experimental equation, and the effective spraying angle was $85^{\circ}{\pm}5^{\circ}$ just at he appropriate spraying pressure of gas. The distribution of the area sprayed had the variation in $350{\pm}50\;mm$ because of the spraying pressure of gas, the its distance from the spray tip, and the lift of the needle valve.

• Clinics in Shoulder and Elbow
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• v.13 no.1
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• pp.111-116
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• 2010

Purpose: There are many known treatment modalities for spinoglenoid ganglion cyst accompanied by suprascapular nerve palsy. However, to the author's knowledge, there is no report on the follow-up outcomes focused on remnant cysts. Materials and Methods: Six (n=6) patients with spinoglenoid ganglion cyst accompanied by suprascapular nerve palsy, with a mean follow-up of 15 months (12-23months) following arthroscopic cyst decompression and superior labral repair, were enrolled. Residual cyst was investigated by ultrasonography and MRI. Results: Immediate postoperative ultrasonography revealed complete remission of ganglion cyst in one patient and reduced ganglion cyst size in five patients. Three-month follow-up ultrasonography showed spontaneous complete remission of the residual cysts in all patients. No recurrence on MRI was seen at one-year follow-up. Conclusion: Residual spinoglenoid ganglion cyst remaining after arthroscopic decompression and superior labral repair tends to resolve spontaneously within 3 months of surgery.

• Journal of Korean Neurosurgical Society
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• v.57 no.5
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• pp.371-375
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• 2015

Spontaneous spinal subdural hematoma is reported at a rare level of incidence, and is frequently associated with underlying coagulopathy or those receiving anticoagulant or antiplatelet agents; some cases accompany concomitant intracranial hemorrhage. The spontaneous development of spinal subdural hemorrhage (SDH) is a neurological emergency; therefore, early diagnosis, the discontinuation of anticoagulant, and urgent surgical decompression are required to enable neurological recovery. In this report, we present a simultaneous spinal subdural hematoma and cranial subarachnoid hemorrhage, which mimicked an aneurysmal origin in a female patient who had been taking warfarin due to aortic valve replacement surgery.

• Journal of Chest Surgery
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• v.29 no.10
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• pp.1152-1156
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• 1996

Cardiac tamponade Is an acute, life-threatening emergency, requiring immediate decompression by a safe and simple method. The most effective method of drainage has been controversial. We experienced successful outcome for the treatment of cardiac tamponade with drainage using the Seldinger technique. The causes of the cardiac tamponade were hemopericardium after mitral and aortic valve replacement and malignant pericardial effusion due to primary lung cancer. They were treated with emergency rainage by the Seldinger technique without procedure-related complications. We believe that this technique is simple, safe for the treatment of cardiac tamponade.

• Analytical Science and Technology
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• v.34 no.1
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• pp.23-35
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• 2021

In order to measure the volatile organic compounds (VOCs) of a sample which is too large to use commercially available chamber, a stainless steel vacuum chamber (VC) (with an internal diameter of 205 mm and a height of 50 mm) was manufactured and the temperature of the chamber was controlled using an oven. After concentrating the volatiles of the sample in the chamber by helium gas, it was made possible to remove residual volatile substances present in the chamber under reduced pressure ((2 ± 1) × 10-2 mmHg). The chamber was connected to a purge & trap (P&T) using a 6 port valve to concentrate the VOCs, which were analyzed by gas chromatography-mass spectrometry (GC-MS) after thermal desorption (VC-P&T-GC-MS). Using toluene, the toluene recovery rate of this device was 85 ± 2 %, reproducibility was 5 ± 2 %, and the detection limit was 0.01 ng L-1. The method of removing VOCs remaining in the chamber with helium and the method of removing those with reduced pressure was compared using Korean drinking water regulation (KDWR) VOC Mix A (5 μL of 100 ㎍ mL-1) and butylated hydroxytoluene (BHT, 2 μL of 500 ㎍ mL-1). In case of using helium, which requires a large amount of gas and time, reduced pressure ((2 ± 1) × 10-2 mmHg) only during the GC-MS running time, could remove VOCs and BHT to less than 0.1 % of the original injection concentration. As a result of analyzing volatile substances using VC-P&T-GC-MS of six types of cell phone case, BHT was detected in four types and quantitatively analyzed. Maintaining the chamber at reduced pressure during the GC-MS analysis time eliminated memory effect and did not affect the next sample analysis. The volatile substances in a cell phone case were also analyzed by dynamic headspace (HT3) and GC-MS, and the results of the analysis were compared with those of VC-P&T-GC-MS. Considering the chamber volume and sample weight, the VC-P&T configuration was able to collect volatile substances more efficiently than the HT3. The VC-P&T-GC-MS system is believed to be useful for VOCs measurement of inhomogeneous large sample or devices used inside clean rooms.