• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.45-52
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• 2018

In this study, 398 city gas pipe systems installed on the bridges were surveyed and analyzed classified characteristics about the ages, length, and remote isolation devices installed or not. As a result of analysis, 43.0% pipes have been used more than 20 years and 89.4% do not have remote cut-off devices, so this study suggest safety management ways for the issues. Chosen 76 pipes were researched stress strain characteristics by CAESAR-II which is a specialized program for stress analysis. And, when a loop is installed on the bridge pipe, effect on code stress by the location and size of the loop was performed. This study can help to improve safety level by revising criteria of new installation, inspection and diagnostic.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.3
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• pp.263-269
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• 2003

Magnetic flux leakage (MFL) signals were used for corrosion inspection of buried oil and gas pipeline. 3D finite element analysis was used to examine the effects of far and near-side pit depth and tensile stress on MFL signals. Anisotropci materials were used, and the effects of simulated tensile stress on MFL were investigated. The axial and radial MFL signals depended on far and near-side single pit depth and on the bulk stress, but the circumferential MFL signal did not depend on them. The axial and radial MFL signals increased with increasing pit depth and the bulk stress, but the circumferential MFL signal was scarcely changed.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.76-89
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• 2018

The distribution of the combined heat and power system is active as a solution to the instability of energy supply and environmental pollution caused by continuous industrial development. In Korea, the safety standards for combined heat and power system using a gas engine are insufficient therefore the study on this is needed. In this study, the safety performance and structural/material assessment items of domestic and international standards applied to the combined heat and power system were analyzed to carry out a standardization study on safety performance applicable to 20 kW gas engine combined heat and power system. In addition, the safety performance assessment (plan) of the gas engine combined heat and power system was derived by performing risk analysis and risk assessment using HAZOP. Assessment items include engine ignition systems related to safety performance, piping tight performance, watering and temperature rise performance, combustion performance, electrical efficiency, thermal efficiency, overall efficiency and humidity performance. Gas and water pipes, gas control and shut-off valves, durability, heat resistance, and cold resistance of metal or non-metallic materials related to the structure and materials of the gas engine combined heat and power systems.

• Journal of the Korean Institute of Gas
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• v.21 no.6
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• pp.8-14
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• 2017

One of the main causes of gas pipeline accidents is mechanical impact(third party damage). The majority of high pressure gas pipelines buried in major domestic industrial complexes are old pipes which have being operated over 20 years. Therefore, if an accident occurs, there will be a full scale accident because there is no additional inspection and reinforcement time. In this study, the defects on the piping during the mechanical impact were studied through the third party damage(excavation) experiments. Experiments were carried out using the 21 ton excavator which is operated in the actual excavation work and the type of pipe to be struck are ASTM A106 Grade.B and ASTM A53 Grade.B. As a result, when the bucket used during excavator operation is a sawtooth bucket, the defect is more bigger. And the smaller the diameter of the pipe, the smaller the depth and length of the defect. Also, it was confirmed that the impact height had no effect on the defects on the buried pipe, during the excavation work.

• Journal of the Korean Magnetics Society
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• v.15 no.6
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• pp.325-331
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• 2005

The magnetic Hut leakage (MFL) type nondestructive testing (NDT) method is widely used to detect corrosion and defects, mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Because of the strong magnetic field enough to saturate the pipe, there could be distortion of the sensing signals because of the magnetization of the pipeline itself, To detect the defects precisely, the sensing signals are need to be compensated to eliminate the distortions coming from the media hysteresis. In this paper, the magnetizations of the pipeline in MFL type NDT are analyzed by Preisach model and 3D FEM. The distortions of the sensing signals are analyzed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.31-31
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• 1998

위성체의 보조추진시스템은 임구궤도까지의 궤도진입 및 임무궤도상에서의 속도 또는 자세제어에 필요한 임펄스를 제공한다. 단일하이드라진 추력기는 하이드라진(H$_2$H$_4$)과 자발적 촉매(Shell 405)의 발열 및 흡열 열분해 반응에 의해 발생하는 질소($N_2$), 수소(H$_2$), 암모니아(NH$_3$), 혼합가스를 노즐을 통해 방출하므로써 요구되는 impulse를 얻는다. 단일하이드라진 추력기 설계는 주입기, 촉매대, 노즐과 기타 설계 형태에 따른 다지관, 링, 스크린, 지지판 등의 부수적인 부품으로 구성된다. 추력기 제작 과정은 크게 piece-parts 기계가공, HEA(Head End Assembly)와 TCA(Thrust Chamber Assembly)로 구성되고 각 세부공정마다 전수시험 및 검사를 가진다. 연소시험설비는 최소 모사진 공 수준이 고도 100,000 ft(8.4 torr)를 만족시킬 수 있는 진공설비, 시험제어부, 성능변수 측정 및 처리부, 추진제 가압 공급부, 기타 환경 안전 및 부대 설비로 구성된다. 추력기 연소성능시험 절차는 추진제 충전 및 오염 여부 표본 검사, 가압 및 공급 라인 이상여부 확인, 추력기 장착, 추진제 가압 및 공급, 시험장치 보정, 진공 모사 및 연소성능시험, data 처리 등으로 구성된다.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.879-881
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• 2002

배관의 PIG시스템은 비파괴검사로써 배관내부에 삽입되어 내부 매체에 의하여 추진되는 장치로서 영구자석을 이용한 자기회로를 형성하여 결함이 있을 때 누선자속을 검출하여 이를 해석하여 배관내의 결함의 크기와 깊이를 검출할 수 있다. 그러나 실제 검출신호는 PIG가 이동시 이동속도에 따른 와전류 문제와 가스관의 착자에 따른 히스테리시스특성에 따른 신호들이 실제 결함에 의한 신호를 왜곡시키게 된다. 본 연구에서는 PIG 의 이동에 따른 이동속도에 따른 와전류 문제와 히스테리시스특성이 검출신호를 왜곡하는 현상에 대하여 연구 하였다.

• Tuberculosis and Respiratory Diseases
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• v.43 no.6
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• pp.976-986
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• 1996

BACKGROUND : Dyspnea is common among patients with cardiopulmonary disease, and "daily disability" is defined as a functional impairment resulting from exercise intolerance. The maximal oxygen uptake(VO2max) during exhausting work is not only the best single physical indicator of the capacity of a man for sustaining hard muscular work, but also the most objective method by which one can determine the physical fitness of an individual as reflected by his cardiovascular system. However, the expense, time and personnel requirements make this procedure prohibitive for testing large group. The walking test is well-known type of exercise and it cost nothing to perform and have good reproducibility. Thus we performed the walking test and investigated correlations with spirometry, ABG and exercise test. METHOD: We observed the walking test and exercise test by cycle ergometer in 37 patients who visited our hospital because of dyspnea. Arterial blood gas analysis and spiromety, dyspnea index were performed, too. RESULT : (1) The VO2max was significantly lower in patients with COPD and cardiovascular disease than asthma and dyspnea on exertion group(p<0.05). The walking test distance was also lower in former. (2) The 12 minute walking test was significantly correlated with VO2max, PaCO2, FVC(%), FEV1(%) in all patients(p<0.05), and the walking test was only conelated with VO2max in patients with COPD(p<0.05). (3) In COPD patients, the VO2max was best correlated with FEV1(%) and FVC(%) and significantly correlated with walking test. But there was no correlation between walking test and FEV1(%) & FVC(%). (4) The 6 minute walking test was well correlated with 12 minute walking test(r=0.92. p<0.01). CONCLUSION : The walking test is the simple method for assessing exercise performance in patient with cardiopulmonary disease and a reliable indicator for VO2max. And the walking test is practical method for assessing on everyday disability rather than maximal exercise capacity. The 6 minute walking test is highly correlated with 12 minute walking test and a less exhausting for the patients and a time-saving for the investigator.

• Clinical and Experimental Pediatrics
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• v.49 no.3
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• pp.273-277
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• 2006

Purpose : The prevalence of Reye syndrome has decreased since late 1980's. But we report that recently there were concentrative attacks of Reye syndrome after acute enteritis during the neonatal period. Methods : Clinical symptoms and laboratory results(quantitative organic acid analysis, routine chemistry, arterial blood gas analysis, serum ammonia) of seven patients admitted at the Samsung Medical Center, Sanggye Paik Hospital, Wonju Christian Hospital and Chuncheon Sacred Heart Hospital, referred from Jan. 2005 to Apr. 2005, were analysed retrospectively. The major clinical symptoms were derived from the patients' clinical records sended with urine samples and quantification of organic acids were done with gas chromatography and mass spectrometry. Results : The mean age of seven cases is 18 days and the major preceding symptoms were gastrointestinal symptoms(vomiting, diarrhea, refusal to feeding). The major clinical symptoms were clouded conciousness, repiratory difficulty, vomiting, seizures, and diarrhea. One patient died; that patient's serum ammonia was twenty times higher than normal. Conclusion : The seven patients were neonates. Reye syndrome has been known to be closely related with upper respiratory infections as a preceding disease and to internal use of aspirin, but in our study, the major preceding disease of the seven cases was gastrointestinal infection and none of these used aspirin.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.30 no.4
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• pp.56-60
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• 2001

경험에 의하면 앞에서 언급한 장비의 사용, 규율, 규제된 용제의 사용, 기름 페인트 사용의 억제, 그리고 엄격한 페인트 과정을 따르는 것에 의해 잠수함내의 탄화수소 농도를 100만분의 1 또는 2 수준으로 유지할 수 있다. 예방책으로는 세심한 관찰, 선체내로 들여오는 모든 물질의 기록 그리고 규제된 물질의 사용 시간, 장소 및 양의 제어이다. 이러한 점들은 잠수함 내부를 안전하고 건강한 환경으로 설계하기 위하여 활용될 수 있는 자료들이다. 잠수함 내의 공기질은 적외선 분광 광도계, 질량 분광계, 상자성(paramagnetics), 열전도율, 광이온화 그리고 열량 검사에 의해 분석될 수 있다. 분석된 결과는 과거의 데이터와 비교되어 활성탄충의 교체등을 포함하여 유지 관리의 자료로 활용된다. 이러한 원리를 이용한 다양한 계측기가 선체 내의 대기 상태를 분석하기 위하여 사용된다. 중앙 대기 측정기, 추적 가스 분석기, 수소 탐지기, 이동형 대기 모니터, 이동형 산소 분석기, 탄광 안전 지시계, 열량 분석관, 탐지 펌프 시험기가 사용된다. 이러한 계측기는 잠수 전 또는 후에 사용된다. 계측기는 화재 발생시 영향을 받지 않은 공간 또는 냉매가 충전되는 장소에 사용된다. 오늘날 여러 종류의 특별한 잠수함이 존재한다. 정찰 업무를 통해 세계 평화를 유지하고 특별한 임무를 수행하는 것보다 덜 복잡한 목적을 지닌 잠수함도 있다. 그러나 선원들이 안전한 내부 환경 속에서 바다 속을 항해하고 계속 그 응용 범위를 확장하기 위하여 앞에서 언급한 장비들 또는 그 변형들이 사용되어야 한다.