• 한국안전학회지
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• 제20권2호
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• pp.158-161
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• 2005

액화석유가스 용기용 과류차단 밸브의 개발에 관한 연구이다. 이 밸브는 베르누이 방정식과 뉴턴의 법칙을 응용하여 개발하였다. 이것은 기존의 밸브 하단에 모듈을 삽입함으로써 과류가 발생하면 모듈이 상승하여 모듈상단의 헤드에 부착된 차단변이 가스의 통로를 폐쇄함으로써 작동된다. 최근 가스 사용이 증가됨으로써 이에 따라 가스사고가 많이 발생되고 있다. 따라서 한국에서는 과류밸브의 사용을 의무화하고 있지만 아직 개발되지 않고 있다. 본 연구는 LP가스 용기용 밸브의 과류 발생시 자동 차단되는 밸브이다. 본 밸브가 채택된다면 많은 가스 사고로부터 벗어 날 수 있을 것이다.

• 한국가스학회지
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• 제9권2호
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• pp.38-42
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• 2005

본 연구는 LP가스 용기용 밸브의 개발에 관한 것으로 안전밸브의 개념을 도입했다. LP가스 용기는 사용의 편리성 때문에 많이 이용되고 있지만 많은 사고가 발생되고 있다. 특히 자해나 남을 해할 목적으로 이용되기도 하며 때때로 시위도구로 사용되기도 한다. 정부에서는 이와같은 사고를 줄이기 위하여 과류밸브를 사용하도록 의무화하고 있지만 제품개발이 뒤따르지 못하고 있는 실정이다. 본 연구에서는 과류밸브보다 근원적 안전개념을 도입한 안전밸브의 개념을 소개한다. 이것은 기존의 밸브에 모듈을 삽입하는 방법으로 개발되었으며 밸브에 호스나 조정기가 연결되지 않은 상태에서는 가스의 흐름이 억제된다. 또한 정상 사용중이더라도 호스가 절단되거나 과류가 발생되면 즉시 가스의 흐름은 차단된다.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.49-55
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• 2015

In this study, among in various scenarios of the duration degradation of the fuel cell, countermeasures for the cathode carbon carrier oxidation and the deactivation of catalyst by hydrogen / air interface formation have been studied. so the system was applied to the air cutoff valve. In terms of the component, the cold start performance, electrical stability, the airtight performance were mainly designed and their performance was confirmed. And in terms of the system, the air electrode flow is blocked off, so the oxygen concentration drops when system is powered off, As a result, By reducing unit cell voltage which affect the durability of the fuel cell reached up to 0.8V, the improved durability of the fuel cell was confirmed.

• 한국자동차공학회논문집
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• 제9권2호
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• pp.130-136
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• 2001

This paper presents an of a brake pressure restriction valve to a motorcycle anti-lock brake system(ABS). In the conventional anti-lock brake system of automobiles, slip ratio as a control variable is actively controlled, which requires wheel speed sensors, ECU, and a pressure modulator. In the ABS valve that has been developed for use in motorcycles, however, the brake pressure that is close to the wheel locking pressure is preset by simple exercises and then the valve just allows to pass the wheel locking pressure and cutoff the remaining pressure. Simulation studies with a single wheel braking dynamics and lumped chassis model show that the pressure restriction valve has basic ABS functions as well as some robustness properties for the uncertain load and road conditions as well as various initial braking speeds. Field tests also show that the pressure restriction valve avoids the wheel locking effectively.

• International Journal of Safety
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• 제11권2호
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• pp.10-14
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• 2012

Recently, the combined power plants are refocused rapidly as a replaceable energy system of the nuclear power plant. The large turbine is revolved highly at 1800~3600 rpm. Thus, the turbine speed should be monitored with mechanical and electrical method for a safety. The electrical cutoff valve which blocks the flow channel with the electrical signal is with a built in. The aim of this study is to develop a manufacturing technology through by the localization of a solenoid actuated directional control valve. Especially the results show performances of the solenoid valve by the experiments and modeling and the reliability estimation. Applied load port pressure was changed rapidly on the form of a quadratic curve over time. And in the cases of square waveform when 0~100 V and 20~120 V input voltage, it was driven on a stable state until 13.4 Hz and 16.6 Hz, respectively. We think that this study will give useful data for the electricity safety system of the combined power plant gas turbine.

• 한국임상수의학회지
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• 제40권1호
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• pp.31-37
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• 2023

Vertebral left atrial size (VLAS) is an important indicator to predict myxomatous mitral valve degeneration (MMVD) in dogs. When the caudal margin of cardiac silhouette and the dorsal margin of caudal vena cava (CdVC) could not be seen exactly, another way to evaluate VLAS is needed. The objective of this study was to assess whether a new modified VLAS (m-VLAS) could be used as an indicator to predict MMVD in 57 small breed dogs with MMVD. The m-VLAS was also used to classify American College of Veterinary Internal Medicine staging groups and left heart enlargement confirmed with echocardiograph (EchoLHE) groups. The m-VLAS was measured as the distance from the ventral aspect of the carina to the dorsal aspect of the intersection of the cardiac silhouette and the farthest LA caudal margin, not the CdVC, followed by drawing the same line beginning at the cranial edge of T4. Based on VLAS values and m-VLAS values measured for dogs with MMVD, correlations between these values and left heart enlargement groups were then evaluated. There were significant differences in both the VLAS and the m-VLAS between EchoLHE groups. The AUC of the ROC curve of the m-VLAS to detect EchoLHE was higher than that of the VLAS. The optimal cutoff value for the m-VLAS was >2.7, which had a higher specificity (86.84%) than the VLAS specificity (71.05%). This study reveals that a new m-VLAS is a more specific indicator than the VLAS for predicting left side heart enlargement in small breed dogs. Therefore, the m-VLAS can be used as a clinically useful radiographic measurement alternative to or better than the VLAS.

• 한국위험물학회지
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• 제2권1호
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• pp.31-37
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• 2014

Since the unprecedented hydrogen fluoride leak accident in 2012, there has been growing demand for customized technical information for rapid response and chemical accident management agencies including the Ministry of Environment, the National Emergency Management Agency, and the National Police Agency need more information on chemicals and accident management. In this regard, this study aims to provide reliable technical data and guidelines to initial response agencies, similar to accident management technical reports of the US and Canada. In this study, we conducted a questionnaire survey and interviews on initial response agencies like fire stations, police stations, and local governments to identify new information items for appropriate initial response and improvements of current guidelines. We also collected and reviewed the Canada's TIPS, US EPA's hydrogen fluoride documents, domestic and foreign literature on applicability tests of control chemicals, and interview data, and then produced items to be listed in the technical guidelines. In addition, to establish database of on-site technical information, we carried out applicability tests for accident control data including ① emergency shut down devide, safety guard, shut down valve, ground connection, dyke, transfer pipe, scrubber, and sensor; ② literature and field survey on distribution type and transportation/storage characteristics (container identification, valve, ground connection, etc.); ③ classification and identification of storage/transportation facilities and emergency management methodslike leak prevention, chemicals control, and cutoff or bypass of rain drainage; ④ domestic/foreign analysis methods and environmental standards including portable detection methods, test standards, and exposure limits; and ⑤ comparison/evaluation of neutralization efficiency of control chemicals on toxic substances.

• 대한기계학회논문집
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• 제18권4호
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• pp.920-932
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• 1994

The combustion phenomena of a reciprocating engine is one of the most important processes affecting performance and emissions. One effective way to improve the engine combustion is to control the motion of the charge inside a cylinder by means of optimum induction system design, because the flame speed is mainly determined by the turbulence at compression(TDC) process in S.I. engine. It is believed that the tumble and swirl motion generated during intake breaks down into small-scale turbulence in the compression stroke of the cycle. However, the exact nature of their relationship is not well known. This paper describes cycle resolved LDV measurement of turbulent flow inside the cylinder of a 4-valve engine under motoring(non-firing) conditions, and studies the effect of intake port configurations on the turbulence characteristics using following parameters ; Eulerian temporal autocorrelation coefficient, turbulence energy spectral density function, Taylor micro time scale, integral time scale, and integral length scale.

• 대한토목학회논문집
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• 제38권4호
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• pp.555-565
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• 2018

최근 임시 지보, 보강 및 지하수 차수와 같은 다양한 지질공학분야에서 차수 및 지반보강 공법으로 인공동결공법(artificial ground freezing method)이 적용되고 있다. 인공동결공법은 지중에 매설된 동결관 내로 냉매를 순환시켜 대상 지반에 차수벽 및 지지체의 역할을 할 수 있는 동결벽체(frozen wall)를 형성한다. 본 연구에서는 해성 점토지반(marine clay)에 대한 인공동결공법 현장실증시험을 수행함으로서 인공동결공법에 따른 해성 점토지반에서의 동결속도(freezing rate)를 평가하였다. 현장실증시험은 지중에 3.2m 깊이로 매설된 동결관 내로 초저온 냉매인 액화질소를 순환시키는 방법으로 단일공 시험과 동결벽체 형성 시험을 수행하였다. 자동밸브를 통해 유출되는 액화질소의 온도를 일정하게 유지시켰으며, 동결과정에서 동결관 외벽 및 지중의 온도변화를 측정하였다. 시험결과, 단일공 시험은 부피가 약 $2.12m^3$인 원기둥 모양의 동결체를 형성하는데 총 3.5일 동안 약 11.9ton의 액화질소가 소요되었고, 동결벽체 형성 시험은 부피 약 $7.04m^3$의 동결벽체를 형성하는데 총 4.1일 동안 약 18ton의 액화질소가 소요된 것으로 산정되었다. 임의의 깊이에서 동결면적이 동결반경의 제곱에 비례하기 때문에 동결반경이 증가할수록 방사방향 1차원 동결속도가 감소하였고, 이를 바탕으로 방사방향 1차원 동결속도 예측식을 제시하였다.

• Korean Circulation Journal
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• 제52권3호
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• pp.205-217
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• 2022

Background and Objectives: The prognostic value of left atrial (LA) function in terms of long-term clinical outcomes after mitral regurgitation (MR) surgery remains unclear. Therefore, we investigated the impact of preoperative LA global longitudinal strain (LAGLS) on the long-term postoperative clinical outcomes in chronic severe MR patients who underwent mitral valve (MV) repair surgery. Methods: From January 2012 to December 2017, we analyzed 338 patients (mean age, 51.9±12.5 years; 218 males [64.5%]) treated with MV repair surgery for severe MR. The primary outcome was cardiovascular events, defined as the composite of all-cause death, newly developed atrial fibrillation (AF), and re-hospitalization for cardiovascular causes. Results: During a median follow-up of 45 months (interquartile range, 26-65), 30 (8.9%) cardiovascular events, 5 (1.5%) all-cause death, 8 (2.4%) newly developed AF, and 26 (7.7%) re-hospitalizations occurred. On multivariable analysis, baseline LAGLS was an independent predictor of cardiovascular events (adjusted hazard ratio [HR], 0.91; 95% confidential interval [CI], 0.85-0.97; p=0.004) and re-hospitalization (adjusted HR, 0.93; 95% CI, 0.86-1.00; p=0.037). According to the optimal cutoff value of LAGLS, patients with low LAGLS (<23.6%) had a significantly higher risk of cardiovascular events (adjusted HR, 2.70; 95% CI, 1.04-7.00; p=0.041) than those with high LAGLS (≥23.6%). In a subgroup analysis, patients with high LAGLS had better clinical outcomes regardless of whether the patient had a LA volume index <60 mL/m². Conclusions: In patients with chronic severe MR who received successful MV repair surgery, preoperative LAGLS is an independent predictor of long-term postoperative outcomes.