• Archives of Plastic Surgery
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• v.48 no.2
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• pp.158-164
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• 2021

Background In lower lateral cartilage (LLC) surgery, cephalic trimming poses risks for the collapse of the internal and external nasal valves, pinched nose, and drooping deformity. The cephalic lateral crural advancement (CLCA) technique presented herein was aimed at using a flap to increase nasal tip rotation and support the lateral crus, in addition to the internal and external nasal valves, by avoiding grafts without performing excision. Methods This study included 32 patients (18 female and 14 male) and the follow-up period for patients having undergone primer open rhinoplasty was 12 months. The LLC was elevated from the vestibular skin using the CLCA flap. A cephalic incision was performed without cephalic trimming. Two independent flaps were formed while preserving the scroll ligament complex. The CLCA flap was advanced onto the lower lateral crus while leaving the scroll area intact. The obtained data were analyzed retrospectively. Results The mean age of the patients was 31.6 years (range, 20-51 years). The Rhinoplasty Outcome Examination scores after 12 months varied from 90 to100 points, and 93% of patients reported perfect satisfaction. At a 1-year follow-up, the patients' nasal patency (visual analogue scale) rose from 4.56±1.53 (out of 10) to 9.0±0.65 (P<0.001). Conclusions The CLCA flap led to better nasal tip definition by protecting the scroll area, increasing tip rotation, and supporting the internal and external nasal valves without cephalic excision.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.585-591
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• 2021

Liquefied hydrogen have advantage which reduces the volume by about 800 times or more compared to hydrogen gas, so it is possible to increase the storage density. However, liquefied hydrogen produced by cryogenic cooling of 20 K or less at normal pressure has a problem of maximizing the insulation effect that blocks heat introduced from the outside. Representative insulation technologies include vacuum insulation and multi-layer insulation materials and in general, heat blocking is attempted by combining insulation technologies. Therefore, in this study, the pressure of the internal vacuum layer was changed to 10^-1, 10^-2, 10^-3 and 10^-4 Torr to confirm the thermal insulation performance of the vacuum jacket valve for transporting liquefied hydrogen. As a result, it was confirmed that the insulation performance improved as the degree of vacuum increased.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.73-79
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• 2021

The objective of this study is to prevent or decrease condensation on the surface of aluminum butterfly valves used in high humidity air conditions. We proposed a new valve with an anti-condensation device, a heat resistance medium, instead of a conventional valve. We, then, compared the surface temperature distribution between the proposed and conventional valves using experimental and analytical methods. The size of the evaluated valve is 100A and fluid conditions are 35℃/RH 75% in the air outside the valve and 5℃ in the cooling water inside the valve. The experimental results show that the surface temperature of the proposed valve is 23~42% higher than that of a conventional valve, thereby exhibiting an anti-condensation effect. As a result, we observed the complete prevention of condensation on a gear box mounted to the proposed valve, showing surface temperature distribution above the dew point temperature of air. The analytical results are in agreement with the trends in experimental results.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.849-859
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• 2022

Feed-water valves (FWVs) are used to regulate the flow rate of water entering steam generators, which are very important devices in nuclear power plants. Due to the working environment of relatively high pressure and temperature, there is strength failure problem of valve body in some cases. Based on the thermo-fluid-solid coupling model, the valve body stress of the feed-water valve in the opening process is investigated. The flow field characteristics inside the valve and temperature change of the valve body with time are studied. The stress analysis of the valve body is carried out considering mechanical stress and thermal stress comprehensively. The results show that the area with relatively high-velocity area moves gradually from the bottom of the cross section to the top of the cross section with the increase of the opening degree. The whole valve body reaches the same temperature of 250 ℃ at the time of 1894 s. The maximum stress of the valve body meets the design requirements by stress assessment. This work can be referred for the design of FWVs and other similar valves.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4181-4194
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• 2022

Main steam safety valves are commonly used in nuclear power plants to provide final protections from overpressure events. Blowdown and dynamic stability are two critical characteristics of safety valves. However, due to the parameter sensitivity and multi-parameter features of safety valves, using traditional method to design and/or optimize them is generally difficult and/or inefficient. To overcome these problems, a surrogate model-based valve design optimization is carried out in this study, of particular interest are methods of valve surrogate modeling, valve parameters global sensitivity analysis and valve performance optimization. To construct the surrogate model, Design of Experiments (DoE) and Computational Fluid Dynamics (CFD) simulations of the safety valve were performed successively, thereby an ensemble surrogate model (E-AHF) was built for valve blowdown and stability predictions. With the developed E-AHF model, global sensitivity analysis (GSA) on the valve parameters was performed, thereby five primary parameters that affect valve performance were identified. Finally, the k-sigma method is used to conduct the robust optimization on the valve. After optimization, the valve remains stable, the minimum blowdown of the safety valve is reduced greatly from 13.30% to 2.70%, and the corresponding variance is reduced from 1.04 to 0.65 as well, confirming the feasibility and effectiveness of the optimization method proposed in this paper.

• Animal Systematics, Evolution and Diversity
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• v.38 no.1
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• pp.14-19
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• 2022

Leptochiton Gray, 1847 is one of the most ancient chiton groups which includes more than 130 species that occur in cold and deep waters worldwide. Due to their small-sized body, they are often confused as juveniles of other chiton species. Moreover, lack of morphological information makes species identification of this group very challenging. To date, only two Leptochiton species(L. fuliginatus and L. rugatus) have been reported from Korean waters. In this study, we found L. hakodatensis(Thiele, 1909) for the first time in Korea and described microscopic morphological characters of valves (tegmentum sculpture), girdle scale, and radula using a scanning electron microscopy (SEM). Leptochiton hakodatensis is morphologically similar to L. fuliginatus and L. rugatus, but differently characterized by having dorso-ventrally rounded (not carinated) intermediate valves, girdle (perinotum) scales sculptured with 4-7 longitudinal ribs, and bicuspid major lateral teeth of radula. In addition to morphological examination, we determined the partial mitochondrial cytochrome c oxidase subunit I(cox1) as a DNA barcode sequence information. This is the first report that describes microscopic characters (tegmentum of valves, girdle structure, and radula) of L. hakodatensis using a SEM. This study provides a morphological basis for describing Leptochiton species and discovery of a "hidden" species of this genus.

• Transactions of the Korean hydrogen and new energy society
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• v.35 no.1
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• pp.83-89
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• 2024

In order to confirm the safety against vibration of high-pressure fittings for mobile hydrogen charging devices, the natural frequency was confirmed through ANSYS, and vibration data occurring during driving was applied to utilize the vehicle's operating power spectral density data specified in MIL-STD-810H regulations. Fatigue analysis and resonance were confirmed, and as a result, it was confirmed that the sum of the pure phase ratios was less than 1 for the driving history presented in the standard, and there was no risk of resonance.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.74-81
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• 2018

The Korean Government has proceeded petroleum gas pipeline construction business since 2014 for rural districts. The operating pressure of petroleum gas pipeline are from 25kPa to 75kPa which are different from that of natural gas pipeline. Petroleum gas pipeline pressure is ten or forty times higher than natural gas operating pressure. For this reason, petroleum gas pipeline has higher probability of accident occurrence from massive gas leakage. Korea Gas Safety Corporation begins to development excess flow valves and their performance testing equipment since 2017. The excess flow valves stop the gas flow when a overflow happened in gas pipeline. The excess flow valves are generally not installed in main pipeline, because that may block massive gas supply. So, the valves are installed in starting points of branch pipes. According to the number of house and amount of gas use, a shut-off point of exxcess flow valve is determined called as Trip Flow. The trip point is the most important thing of excess flow valve, so, it is required a equipment testing the performances of excess flow valve as trip point.

• Journal of Chest Surgery
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• v.16 no.2
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• pp.139-146
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• 1983

Between 1974 and 1982, 31 patients from 7 to 15 years of age have undergone valve replacement for their acuqired cardiac valvular diseases at Seoul National University Hospital. Furteen patients (45.2%) had a definite history of rheumatic fever and only 4 patients (12.9%) had atrial fibrillation on their preoperative electrocardiograms. Characteristically, the valvular lesions were ones of insufficiency with or without associated stenosis in all patients except only one whose mitral valve was tightly stenotic. Thrity-seven valves were replaced in 31 patietns including a case of successful replacement of his failed xenogragt mitral valve : 4 mechanical valves were used in 3 patients and 33 xenograft valves were used in the remaining 28 patients. The size of the valves were not the major problem at the time of opertion because most of the patients had a dilated heart from disease. There were 3 diaths within 30 days of surgery (9.7% operative mortality rate) and 3 late deaths (9.7% late mortality rate) with an overall mortality rate of 19.4%. Twenty-eight early survivors were followed up for a total of 488 patient-months. Thromboembolic complications occurred in 5 patients with 2 deaths: cmbolic rate of 17.9% or the actuarial embolic incidence of 12.29%/patients-year. four xenograft tissue valves in 4 patients had failed during the period from 19 to 41 months of surgery with an overall valve failure rate of xenograft of 14.3% or the actuarial incidence of 9.84% failure/patient-year. One of these 4 patients had required replacement of his failed mitral xenograft valve which had severe calcification and tissue disruption with primary tissue failure rate of 3.6% or the actuarial incidence of 3.13% failure/patient-year. The actuarial survial including the operative morality was 50.0% at 5 years of surgery. /the actuarial incidence free from thromboembolism in bioprosthetic group was 85.4% at 42 months, while it was 33.4% in mechanicial group at 60 months after operation. The actuarial incidence free from overall valve failur of 100.0% until 18 months after surgery was followed by a rapid decrease during the next 2-year period, and it was only 17.8% at the follow-up end of 42 months after surgery. It was suggested that the major advantage of low thrombogenecity with xenograft valve should be balanced against the high incidence of accelerated valve failure when it is used in children whose age is younger than 15 years old. The possible role of recurrent rheumatic attacks to the early failure of xenograft tissue valve was also discussed.

• Water for future
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• v.30 no.5
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• pp.69-74
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• 1997