• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 춘계 학술대회논문집
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• pp.159-165
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• 2000

In this paper, numerical study has been done for the improvement of the superdetonative ram accelerator performance and for the design optimization of the system. The objective function to optimize the premixture composition is the ram tube length required to accelerate projectile from initial velocity $V_o$ to target velocity $V_e$. The premixture is composed of $H_2,\;O_2,\;N_2$ and the mole numbers of these species are selected at design variables. RSM(Response Surface Methodology) which is widely used for the complex optimization problems is selected as the optimization technique. In particular, to improve the non-linearity of the response and to consider the accuracy and efficiency of the solution, design space stretching technique has been applied. Separate sub-optimization routine is introduced to determine the stretching position and clustering parameters which construct the optimum regression model. Two step optimization technique has been applied to obtain the optimal system. With the application of stretching technique, we can perform system optimization with a small number of experimental points, and construct precise regression model for highly non-linear domain. The error to compared with analysis result is only $0.01\%$ and it is demonstrated that present method can be applied more practical design optimization problems with many design variables.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1675-1682
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• 2012

경량화는 대기오염과 자원고갈의 측면에서 매우 중요하게 인식되고 있어, 많은 자동차용 부품이 Al 및 Mg 합금으로 대체되었으며, 관련 연구가 지속적으로 증가하고 있다. 그러나 Mg 합금은 Al 합금에 비해 높은 재료비와 난성형성으로 인한 낮은 생산성 때문에 제한적으로 적용되고 있다. 본 연구에서는 FEA를 이용하여 자동차 범퍼 백 빔용 관재에 대한 공정조건을 분석하였으며, 생산성을 향상시킬 수 있는 방법을 확립하였다. 물성치 확보를 위해 물성시험을 수행하였으며, 소성변형 중 발생하는 열 관련 물성을 정의하기 위하여 단순형상에 대한 실험과 해석을 수행하였다. 이후 온도조건 및 램 속도를 고려하여 제품에 대한 해석을 수행하였다. 이를 통하여 압출공정조건을 확립하였으며, 표면결함이 없는 제품을 성형하는데 성공하였다.

• 한국추진공학회지
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• 제1권1호
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• pp.8-23
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• 1997

스탠포드 대학의 expansion tube 장치를 이용한 램 가속기의 유동장의 실험적 연구와 비교를 위하여 정상 및 비정상 상태의 수치모사를 수행하였다. 수소/공기 연소에 대하여 9 화학종 19 반응 단계를 가지는 Jachimowski의 화학반응 모델을 이용하여 화학 반응 유동에 대한 Navier-Stokes 방정식을 시간 정확도를 가지는 완전 내재적수치 기법을 이용하여 해석하였다. 정상 상태 가정을 이용한 수치해석은 $2H_2$＋$O_2$＋$17N_2$에 대하여 쉴리렌 및 OH PLIF 을 이용하여 실험적으로 얻어진 영상과 부합하는 좋은 결과를 보였으나 $2H_2$＋$O_2$＋$12N_2$ 혼합기에 대해서는 충격파 교차점 후방의 연소 영역을 모사하지 못하였다. 따라서 이 경우에 대하여 비정상 수치 모사를 수행하였으며 자세한 유동 안정화 과정을 보여 주었다. 비정상 수치 모사의 결과로부터 실험적으로 얻어진 영상은 유동 안정화 단계의 일시적 상태의 결과로 보인다. 충격파 교차점 후방의 연소 영역은 유동이 안정화되는 초기 단계에 존재하는 강한 경사 충격파가 교차하여 발생하는 수직 폭굉파의 결과이다. 최종 단계에서 충격파 교차점 이후의 연소 영역은 사라지며 정상 상태의 결과가 얻어진다. 램 가속기 모델 내부의 화학반응 유동이 안정화되는데 필요한 시간은 실험적인 시험 시간과 비교하여 매우 긴 것으로 보인다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.415-415
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• 2012

ZnO nanostructures were synthesized by a vapor phase transport process in a single-zone furnace within a horizontal quartz tube with an inner diameter of 38 mm and a length of 485 mm. The ZnO nanostructures were grown on Au-catalyzed Si(100) substrates by using a mixture of zinc oxide and graphite powders. The growth of ZnO nanostructures was conducted at $800^{\circ}C$ for 30 min. High-purity Ar and $O_2$ gases were pushed through the quartz tube during the process at a flow rate of 100 and 10 sccm, respectively. The sequence of ON/OFF cycles of the Ar gas flow was repeated, while the $O_2$ flow is kept constant during the growth time. The Ar gas flow was ON for 1 min/cycle and that was OFF for 2 min/cycle. The structure and optical properties of the ZnO nanostructures were investigated by field-emission scanning electron microscope, X-ray diffraction, temperature-dependent photoluminescence. The preferred orientation of the ZnO nanostructures was along c-axis with hexagonal wurtzite structure.

• 융합정보논문지
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• 제12권2호
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• pp.198-205
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• 2022

본 연구의 목적은 20대 남녀의 뷰티 트렌드 정보를 바탕으로 성별에 따른 뷰티 상업광고의 영향력을 파악하고, 일종의 마케팅 수단으로 쓰이는 뷰티 상업광고의 효과를 확인하고자 한다. 이를 위해 외모에 대한 관심과 SNS 사용이 가장 높은 20대 남녀를 대상으로 설문조사를 진행하였다. 여성은 접근성, 신뢰성 정보성이 가장 높은 광고로 모두 유튜브 광고를 택했고 남성은 각각 인스타그램 광고, TV 광고, 유튜브 광고를 택했으며 그 결과 20대 여성에게 가장 영향력 있는 광고는 유튜브 광고, 남성에게 가장 영향력 있는 광고는 접근성이 높은 인스타그램 광고라는 점을 확인하였다. 이러한 결과는 앞으로의 뷰티 시장에서 서비스 및 마케팅 분야에 새로운 전략을 구축하는 데에 활용될 수 있다.

• Journal of Chest Surgery
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• 제13권4호
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• pp.496-496
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• 1980

A 37 year old male patient was suffered from severe labored breathing caused by post tracheostomy stenosis, which was localized at the mediastinal trachea [cuffed tracheal stenosis] and ranged 1.5 cm in length and approximately 3 ram. in diameter on tracheogram. After dilation of tracheal stenosis with dilator, endotracheal intubation was tried for induction of anesthesia and control of respiration during operation. A tube was placed just beyond the tracheal stenosis without respiratory difficulty. Under the endotracheal anesthesia, circumferential resection of the mediastinal trachea containing the stenosis, approximately 2 cm in length [4 tracheal rings}, was carried out and primary direct end to end anastomosis was performed with interrupted submucosal sutures [3-0 Dexon] and mobilization of trachea Postoperative tracheostomy was not performed. The patient was completely relieved from dyspnea immediately after operation. Post-operative convalescence was entirely uneventful and at present, about 3 months after operation, he is now conducting a usual life. From the literature and our experience, the etiology and treatment of post-tracheostomy stenosis were discussed.

• Journal of Chest Surgery
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• 제13권4호
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• pp.503-506
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• 1980

A 37 year old male patient was suffered from severe labored breathing caused by post tracheostomy stenosis, which was localized at the mediastinal trachea [cuffed tracheal stenosis] and ranged 1.5 cm in length and approximately 3 ram. in diameter on tracheogram. After dilation of tracheal stenosis with dilator, endotracheal intubation was tried for induction of anesthesia and control of respiration during operation. A tube was placed just beyond the tracheal stenosis without respiratory difficulty. Under the endotracheal anesthesia, circumferential resection of the mediastinal trachea containing the stenosis, approximately 2 cm in length [4 tracheal rings}, was carried out and primary direct end to end anastomosis was performed with interrupted submucosal sutures [3-0 Dexon] and mobilization of trachea Postoperative tracheostomy was not performed. The patient was completely relieved from dyspnea immediately after operation. Post-operative convalescence was entirely uneventful and at present, about 3 months after operation, he is now conducting a usual life. From the literature and our experience, the etiology and treatment of post-tracheostomy stenosis were discussed.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.305-308
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• 2006

For controlling micro-flows inside a LOC (lab-on-a-chip) a syringe pump or an electronic device for EOF(electro-osmotic flow) have been used in general. However, these devices are so large and heavy that they are burdensome in the development of a portable micro-TAS (total analysis system). In this study, a new flow control system employing pressure chambers, digital switches and speed controllers was developed. This system could effectively control the micro-scale flows inside a LOC without any mechanical actuators or electronic devices We also checked the feasibility of this new control system by applying it to a LOC of micro-mixer type. Performance tests show that the developed control system has very good performance. Because the flow rate in LOC is controlled easily by throttling the speed controller, the flows in complicate microchannels network can be also controlled precisely.

• Journal of Chest Surgery
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• 제13권4호
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• pp.495-502
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• 1980

A 37 year old male patient was suffered from severe labored breathing caused by post tracheostomy stenosis, which was localized at the mediastinal trachea [cuffed tracheal stenosis] and ranged 1.5 cm in length and approximately 3 ram. in diameter on tracheogram. After dilation of tracheal stenosis with dilator, endotracheal intubation was tried for induction of anesthesia and control of respiration during operation. A tube was placed just beyond the tracheal stenosis without respiratory difficulty. Under the endotracheal anesthesia, circumferential resection of the mediastinal trachea containing the stenosis, approximately 2 cm in length [4 tracheal rings}, was carried out and primary direct end to end anastomosis was performed with interrupted submucosal sutures [3-0 Dexon] and mobilization of trachea Postoperative tracheostomy was not performed. The patient was completely relieved from dyspnea immediately after operation. Post-operative convalescence was entirely uneventful and at present, about 3 months after operation, he is now conducting a usual life. From the literature and our experience, the etiology and treatment of post-tracheostomy stenosis were discussed.

• 한국정밀공학회지
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• 제29권1호
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• pp.96-102
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• 2012

The current establishment of car engineering plastic piping polyethylene (PE) tube used as bonding state or part of the health or safety of fusion is very important. A part of these fusion methods to determine the soundness of the short-term trials and long-term tests can be largely classified. Typical tests included short-term strength, tensile strength, impact strength, compressive strength, resiliency and compression. Polyethylene (PE) pipes installed in the domestic terms of overall penetration rate of 45% has been used. However, polyethylene (PE) pipes have reliability problems, and these occurs mostly in part by defective welding. Therefore, the test is necessary for safety. Non-destructive methods (ultrasonic testing) are difficult to be used. Therefore, Polyethylene (PE) pipe are used. Fusion of thses materilas is necessary in these field however, its technical, and basic research has not been studied well. In this research, short-term strength of welding parts, its tensile strength, hardness, fatigue, and microstructure have been analyzed to find the optimum process conditions to improve mechanical properties.