• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.101-104
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• 2010

A bulkhead-type pulse separation device has been developed for the multi-pulse rocket motor. The design parameters of the pulse separation device were the shape of the rupture disc slit, welding conditions, and the implementation of the seal disc. The pneumatic tests of the fabricated pulse separation devices showed that the rupture pressure increased as the quantity of the rupture disc slit and welding strength increased and the seal disc was implemented.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.245-248
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• 2011

A multi pulse rocket motor(MPRM) has several advantages compared to the single one. The range and the terminal velocity of the guided missile can be remarkably increased by the application of the pulse separation device(PSD) to the solid rocket motor which resulted in appropriate thrust distribution. In this study, the full scale heavy type dual pulse rocket motor with the bulkhead type PSD was designed, manufactured, and fire-tested. The bursting time and pressure of PSD were analyzed by the pressure, thrust and vibration results of static fire tests. As a result, the design requirement was verified that bursting pressure is lower than 30% of 2nd pulse operating pressure.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.49-56
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• 2012

Rupture disks are a kind of safety device in high pressure equipment and they are used to control rupture pressure in the solid rocket motor. In this paper, a series of rupture experiments was performed using rupture disks made of AISI 316L and rupture pressure of rupture disks was calculated through various assumptions in relation between elasto-plastic material properties and true stress-strain curve. Experiment and FEA indicated rupture pressure is determined by size of rupture disks. As a result of elasto-plastic analysis, only multi-linear stress-strain curve was able to calculate meaningful estimations. Experimental results also showed rupture location are decided by the size of rupture disks. Experimental and FEA results will be applied to control rupture pressure of disks.

• Current Industrial and Technological Trends in Aerospace
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• v.5 no.2
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• pp.87-97
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• 2007

오늘날 항공기 설계와 제작은 다국적인 산업의 형태로 이루어지고 있다. 즉 항공기 서브시스템은 세계 각국에서 독립적으로 설계, 제작 및 시험한 후 한 곳으로 납품되어 조립 제작되는 데 이 때 중요한 것이 표준화이다. 항공전자장비의 낙뢰 간접영향에 대한 인증의 경우 RTCA DO-160E, Section 22 Lightning Induced Transient Susceptibility(낙뢰 유도 과도현상 적응성)로 표준화 되어 있다. 이 Section 22는 낙뢰 간접영향에 대한 항공전자장비 단위 즉, LRU (Line Replaceable Units)와 같은 부품단위의 시험 요건을 규정하고 있으며 이 규격은 현재 전 세계적으로 통용이 되고 있다. 1980년대 초 상용 수송기에 디지털 "Fly by Wire" 비행 시스템과 엔진제어시스템(EEC, Electronic Engine Control)의 도입 이후, 항공기 시스템이 낙뢰 환경에서 운용시 신뢰성을 보증할 필요성이 대두되었다. 데이터 처리를 통하여 제어되는 각종 항공전자장비에는 다중타격(MS)과 다중파열(MB) 기법에 의한 시험 사항이 최근 추가 되었다. 실제 낙뢰 환경과 유사한 시험실 모사를 위해 계속적인 연구가 진행 중이며 신규 시험 규격서가 새로이 출간되고 있다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.24-27
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• 2012

In this study, the full scale flight type Dual-Pulse Rocket Motor(DPRM) with the bulkhead type Pulse Separation Device(PSD) was designed, manufactured, and fire-tested. The bursting time and pressure of PSD were analyzed by the pressure, thrust and vibration results of static fire tests and ablation of PSD was measured with 3-D coordinate measuring machine. As a result, PSD requirements, bursting conditions and thermal safety, were satisfied.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.52-65
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• 2021

In this study, authors analyzed the vapor cloud explosion induced by propane leak at the PEMIX Terminal, which is the propane storage facility outside of Mexico City. TNT equivalence mass for the leaked 4750 kg propane was estimated to be 9398 kg. Blast parameters such as peak overpressure, positive phase duration, and impact at 40-400 (m) away from the center of the explosion were calculated by applying TNT Equivalency Method and Multi-Energy Method. The probability of damage due to lung damage, eardrum rupture, head impact, and whole-body displacement impact by applying the probit function obtained using blast parameters was evaluated. The peak overpressure obtained using Multi-Energy Method was found to be greater than the peak overpressure obtained by applying the TNT Equivalency Method at all distances considered, but it was evaluated that there was no significant difference from the points above 200 m. The peak overpressure obtained by Multi-Energy Method was computed to assess the extent of damage to the structure, and it was shown that structures within 100 m of the explosion center would collapse completely, and that the glasses of the structures 400 m away would be almost broken. The probability of death due to lung damage was shown to vary depending on a human body's position located in the propagating direction of shock wave, and if there is a reflecting surface in the immediate surroundings of a human body, the probability of death was estimated to be the greatest. The impact of shock wave on lung damage, eardrum rupture, head impact, and whole-body displacement impact was evaluated and found to affect whole-body impact < lung damage < eardrum rupture

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.187-190
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• 2009

A multiple pulse rocket motor distributes the thrust energy more effectively compared to typical rocket motor as providing subsequent thrusts by the pulse motors of the missile. The pulse rocket motor is the advanced technology to improve an end game capability of the missile by increasing the range and final velocity. A pulse separation device is the core part of the pulse motor. The pulse separation device of bulkhead type was designed and developed. The elastic-plastic structural analysis of the bulkhead and rupture disc was conducted. Several air tests were also conducted to confirm the structural safety and acceptability about the design concept. Test results were compared with the analysis results, which showed reasonable agreements.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.5
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• pp.356-361
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• 2014

The eddy current testing performance directly affects the results of a steam generator tube integrity assessment because the integrity assessment of defected tubes is conducted based on eddy current testing results. This means that it may not be possible to accurately discriminate between adjacent flaws. This paper presents an investigation on the resolution of rotating pancake coils with multiple cracks and the effects on the structural integrity assessment of steam generator tubes.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.115-125
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• 2009

Purpose: The purpose of the study is to evaluate the usefulness of CT arthrography (CTA) by conducting a comparative study of CTA and MR arthrography (MRA) with the arthroscopic findings in the same patients. Materials and methods: Forty nine patients who suffered from shoulder disease underwent MRA and CTA concurrently. The sensitivity and specificity of CTA was evaluated, as compared to MRA, in the case of four types of shoulder pathological lesions. The accuracy of CTA was evaluated by analyzing the arthroscopic findings of thirty four patients. Results: Compared to MRA, CTA showed a sensitivity of 90% and a specificity of 100% for diagnosing supraspinatus tendon (SST) full thickness tear, and CTA showed a sensitivity of 100% and a specificity of 97.5% for making the diagnosis of superior labrum anterior to posterior (SLAP) lesion. For diagnosing partial articular side supraspinatus avulsion (PASTA) lesion, some studies have shown the usefulness of CTA with a sensitivity of 71.4% and a specificity of 97.7%. However, for diagnosing SST bursal side partial tear, the sensitivity of CTA was as low as 10%. CTA has been shown to be relatively accurate when the diagnoses were verified with the arthroscopic findings; diagnosing SST full thickness tear and SLAP lesion with CTA has shown an accuracy of 100% and87.5% respectively, and CTA showed 71.4% diagnostic accuracy for PASTA lesion. Conclusion: CTA was a useful tool and it was equivalent to MRA for the assessment of SST full thickness tear, SLAP lesion and PASTA lesion, but not bursal side partial tear. Thus, it may be used preferably to diagnose shoulder pathology and for follow up as an inexpensive tool after operation.

• Journal of the Korean Arthroscopy Society
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• v.13 no.2
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• pp.155-160
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• 2009

Purpose: The purpose of this study was to evaluate the pain recovery pattern according to the integrity and to analyze the factors affecting the progress and level of pain postoperatively. Materials and Methods: We examined 153 patients, who were treated with arthroscopic rotator cuff repair. 101 rotator cuff tears were full-thickness tear and 52 were partial tear. The mean follow up duration was 20 months (12~30 months). We evaluated the visual analogue scale, range of motion, ASES (American Shoulder and Elbow Surgeons), and UCLA (University of California at Los Angeles) scores preoperatively and postoperatively. We analyzed the pain recovery pattern between partial and full thickness tear using Student T-test and the factors affecting the progress and level of postoperative pain using multiple regression analysis. Results: The change patterns of visual analogue scale after arthroscpoic repair were similar regardless of the tear integrity. The VAS showed a continuous decreasing pattern, but increased at first 3 weeks postoperatively and at 7 weeks postoperatively, and then, decreased thereafter. The average VAS was ${\leqq}2$ points by postoperative 3 months. The factor affecting the pain score at 3 months was related to the preoperative limitation in forward flexion ($r^2=0.377$, p=0.021). Conclusion: There was no differences of the pain recovery pattern according to the integrity, and the factor affecting the progress of postoperative pain was preoperative angle of forward elevation. So, the appropriate preoperative rehabilitation protocol that can improve motions of the shoulder joint would help to improve the level of postoperative pain and functional recovery.