• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
• /
• pp.162-165
• /
• 2004

고성능 액체로켓엔진 개발을 위하여 터보펌프를 사용하는 재생냉각형 액체로켓엔진시스템의 배치안을 마련하였다 엔진시스템을 구성하는 부품들에 대하여 각각의 특성을 고려하고 현실적으로 제작 및 조립이 가능하도록 3차원 디지털 모형을 제작하여 검증하였다. 1단 엔진시스템은 1축 김발링을 하며 4개의 엔진 조립체로 클러스터링 할 수 있도록 설계하였다. 2단용 엔진시스템은 2축 김발링을 하며 1개의 엔진 조립체로 구성하였다. 1단 및 2단 엔진시스템의 조릴 및 분해 공정 그리고 관련 프로그램 또한 개발하였다. 그리고 엔진시스템의 조져 및 분해 공정을 효율적으로 수행하기 위하여 여러 형태의 전용 치/공구 또한 개발하였다.

• Journal of Ceramic Processing Research
• /
• 제20권1호
• /
• pp.48-53
• /
• 2019

Carbon fiber reinforced SiC composites (C/SiC) have high-temperature stability and excellent thermal shock resistance, and are currently being applied in extreme environments, for example, as aerospace propulsion parts or in high-performance brake systems. However, their low thermal conductivity, compared to metallic materials, are an obstacle to energy efficiency improvements via utilization of regenerative cooling systems. In order to solve this problem, the present study investigated the bonding strength between carbon fiber and matrix material within ceramic matrix composite (CMC) materials, demonstrating the relation between the microstructure and bonding, and showing that the mechanical properties and thermal conductivity may be improved by treatment of the carbon fibers. When fiber surface was treated with a nitric acid solution, the observed segment crack areas within the subsequently generated CMC increased from 6 to 10%; moreover, it was possible to enhance the thermal conductivity from 10.5 to 14 W/m·K, via the same approach. However, fiber surface treatment tends to cause mechanical damage of the final composite material by fiber etching.

• 대한기관윤리심의기구협의회지
• /
• 제4권2호
• /
• pp.30-35
• /
• 2022

The Human Research Protection Program (HRPP) includes all subject protection activities and entities involved in the process of planning, reviewing, and conducting clinical research and it ultimately aims that research can be conducted ethically and scientifically while protecting the rights and welfare of research subjects. At the beginning of its introduction in Korea, it was settled down by adopting the United States HRPP, especially the form of AAHRPP element and regulations. However, regulations and operating forms of HRPP have been changed according to the Korean domestic research environment. Actually, all the Korean institutions are adopted the Korean HRPP guidelines that have been officially announced by the Ministry of Food and Drug Safety in Korea. Recently, Korean domestic laws such as the "Advanced Regenerative Biology Act" or "In Vitro Diagnostic Medical Device Act" have been dramatically innovated and our research environment becomes to be more complicated. Therefore, the development of a suitable Korean HRPP model considering the Korean research environment is strongly demanded. For the early settle down of the Korean HRPP model, the positive incentive method should be applied, when the HRPP is operated and/ or properly operated. These improvements in the Korean HRPP environment will eventually lead to the appropriate protection of subjects who are participating in human clinical research and the quality improvement of clinical research.

• 영어영문학
• /
• 제57권5호
• /
• pp.701-725
• /
• 2011

This paper attempts to read "The Nightingale" as an experimental proponent of Lyrical Ballads of 1798, one that inaugurated British Romanticism. It is never accidental for this poem to come to replace "Lewti" at the last moment of publication and to be tied to the poetic principles manifested in the "Advertisement" of the 1798 volume. The speaker of this poem, for example, is an ordinary man, who presents himself as a friend and a loving father. Opting for conversational styles rather than blindly copying literary conceits, he even incorporates an evening episode he happens to recall into a legitimate subject matter. The notion of "conversation," which appears in the subtitle, offers a key to figuring out the ideal of poetic language, the figure of the poet, and compositional procedures Coleridge and Wordsworth proposed in their collaborative project. "The Nightingale" can be a dubious, if not totally failed, poetical journey to subverting an incidence of misnaming acts. He finally reaches the limits of poetic figuration in a process of textualizing nature. The leitmotif of "In nature there is nothing melancholy" testifies to the fact that the bird nightingale, which the narrator is hard at work to rename as a joyous bird, is nothing but a poetic metaphor. "The Nightingale" is more likely to be a revisional, regenerative performance based on the strategy of conversation than an embodiment of a daring novelty.

• 한국항해항만학회지
• /
• 제48권2호
• /
• pp.125-136
• /
• 2024

This research presents an innovative integrated ethanol solid oxide fuel cell (SOFC) system designed for applications in marine vessels. The system incorporates an exhaust gas heat recovery mechanism. The high-temperature exhaust gas produced by the SOFC is efficiently recovered through a sequential process involving a gas turbine (GT), a regenerative system, steam Rankine cycles, and a waste heat boiler (WHB). A comprehensive thermodynamic analysis of this integrated SOFC-GT-SRC-WHB system was performed. A simulation of this proposed system was conducted using Aspen Hysys V12.1, and a genetic algorithm was employed to optimize the system parameters. Thermodynamic equations based on the first and second laws of thermodynamics were utilized to assess the system's performance. Additionally, the exergy destruction within the crucial system components was examined. The system is projected to achieve an energy efficiency of 58.44% and an exergy efficiency of 29.43%. Notably, the integrated high-temperature exhaust gas recovery systems contribute significantly, generating 1129.1 kW, which accounts for 22.9% of the total power generated. Furthermore, the waste heat boiler was designed to produce 900.8 kg/h of superheated vapor at 170 ℃ and 405 kP a, serving various onboard ship purposes, such as heating fuel oil and accommodations for seafarers and equipment.

• 치위생과학회지
• /
• 제16권4호
• /
• pp.317-322
• /
• 2016

최근 성장 중인 아동에서 치근의 성장이 계속됨에 따라 치수가 괴사되어 치근의 병변이 있는 미성숙 영구치에서도 치수의 재혈관화(revascularization)가 실제로 일어날 수 있다는 가능성이 제시되고 있다. 소아치과영역에서 자주 접하게 되는 미성숙 영구치의 치근단 형성술의 목적은 열린 치근단에서 세균 침입을 제한하고 치근단 장벽 형성을 촉진하는 것이다. 미성숙 치아의 근관 치료에서 기존의 수산화칼슘을 이용한 치근단 형성술은 빈번한 내원과 장기간 소요되는 치료 기간, 환자협조 요구, 최종 처치의 지연, 장기간의 수산화칼슘 적용 이후 치아 파절 가능성의 증가 등의 단점이 보고되었다. 기존의 수산화칼슘 치근단형성술의 대체방법으로 MTA를 이용한 1-visit 치근단형성술을 시행하고 있다. MTA는 1990년대 초반 근관치료 분야에서 다양한 적용을 위해 개발되었다. MTA의 우수한 임상적 성질에 힘입어 국내에서도 OrthoMTA 및 Endo CEM 등의 mineral aggregate 제품이 출시되어 있다. 따라서 본 증례에서는 우리나라의 청소년에서 MTA 적용한 사례를 보고하는 데 있다. 이 연구를 통해 MTA를 이용하여 진료하는 임상가에게 소개하고자 한다. 이 연구는 11~12세의 파절이 된 치아에 MTA를 적용하여 근관 치료를 하였다. 치료 받은 환자의 치아 상태를 12개월 동안 추적 관찰하였고, 국내에서 개발된 OrthoMTA를 이용한 치근단형성술을 시행한 후 임상적 및 방사선학적 관찰 결과를 통해 근관치료재생술(REP)에 관한 만족할 만한 결과를 얻었으며, 치수괴사가 생긴 경우에서도 성공적으로 치수재생술을 적용할 수 있다는 정보를 제공하고 그 결과를 공유하기 위함이다.

• 한국임상수의학회지
• /
• 제40권2호
• /
• pp.93-103
• /
• 2023

The tendon is a dense connective tissue that connects muscle to bone and plays an essential role in joint motion. The injured tendon heals slowly owing to its low cellularity and vascularity. This study aimed to evaluate and compare the effects of regenerative injection therapy (RIT), 20 % dextrose prolotherapy (DP), and platelet-rich plasma (PRP) injections that can promote tendon healing. Twenty-one New Zealand white rabbits were divided into the control, DP, and PRP treatment groups. The superficial digital flexor tendon (SDFT) of the right hindlimb of each rabbit was used. A round defect of 2 mm was induced. Approximately 0.2 mL of 20% dextrose and autologous PRP were injected into the proximal and distal ends of the SDFT mass. Radiographic and ultrasonographic examination and cross-sectional area (CSA) calculations were performed pre-operatively and at 2, 4, and 8 weeks. The SDFT of both limbs was transected for biomechanical and histomorphometric evaluations. The SDFT of the left limb was transected for intact control. Semi-quantitative analysis was performed to evaluate the histomorphometric properties. Additional analysis was performed using H&E, Masson's trichrome, and immunohistochemical staining. The biomechanical evaluation showed that the treatment groups had higher tensile strength compared to the defect control group, while the PRP group had higher tensile strength than the DP group. On histological examination, the treatment groups appeared to be relatively closer to the remodeling phase of the healing process than the defect control group; the characteristics of the PRP group were closer to the remodeling phase than those of the DP group. The ultrasonographic examination showed different tendencies. Increased values in the CSA were observed during the early period in the treatment groups. This study suggests that PRP and DP can promote the healing of tendon injury, and these effects were superior with PRP than that with DP.

• 한국전자파학회논문지
• /
• 제20권10호
• /
• pp.1107-1113
• /
• 2009

본 논문에서는 K-Band에서 동작하는 1/2 주파수 분배기를 130 nm CMOS 공정을 이용하여 설계하고 제작한 결과를 보인다. 피드백 방식의 밀러 주파수 분배기는 20~25 GHz에서 동작하며 바이어스 전압 1.2 V에서 7.2 mW의 전력을 소모하고 코어 회로의 레이아웃 크기는 $315{\times}246\;um^2$이다. 밀러 주파수 분배기의 출력 신호를 2분 주시키기 위한 CML(Current Mode Logic) 주파수 분배기는 8.5~13 GHz에서 동작하며 5.7 mW의 전력을 소모하고, 코어 회로의 레이아웃 크기는 $91{\times}98\;um^2$이다. 또한 두 주파수 분배기를 결합하여 20~25 GHz의 입력 신호가 4분주되어 출력됨을 확인하였다.

• 대한공업교육학회지
• /
• 제32권2호
• /
• pp.171-187
• /
• 2007

이 연구의 목적은 선삭 가공시 발생하는 채터 진동을 계측하기 위하여 일반적인 가속도계가 가진 단점을 보완한 페브리-페롯형(Fabry-Prtot) 광섬유 간섭계 센서를 공구에 직접 부착하여 채터 진동을 측정하고 이것의 유용성을 확인하는 것이다. 측정된 주파수 스펙트럼과 이론해석 상의 리셉턴스 곡선과 비교하였는데 공구진동이 클수록 가진 주파수 이동이 생성되며 이는 공구의 날 끝에 질량효과가 더해짐을 의미함을 알 수 있었다. 질량효과가 더해지면 진동 주파수는 저주파 쪽으로 이동한다. 진동 주파수의 저주파 영역의 이동은 일반적인 재생형 채터에서 흔히 일어나는 현상이다. 또한 측정한 채터 주파수는 고유진동수가 아닌 외부 가진 주파수인 것으로 확인 됐으며 측정 결과와 같이 본 실험에 사용된 광섬유 센서는 외부 진동 주파수를 잘 계측 하였으며 페브리-페롯 센서는 특히 공구진동의 측정에 유용함을 보았다. 본 연구를 통하여 적용분야로 간섭계형 광섬유 센서를 공구 표면에 직접 설치하고 공구 진동을 관찰하는 교육목적의 실험에도 응용할 수 있다. 본 실험과 같은 페브리-페롯 간섭계 센서의 공구 직접 접촉식 방법에 대한 연구는 국내외 적으로 그 사례를 찾아보기 힘든 독창적인 방법인 것으로 추정된다. 본 연구결과는 또한 향후 공구진동과 마멸을 연구하는데 기초 자료로 활용할 수 있을 것으로 판단된다.

• The Korean Journal of Physiology and Pharmacology
• /
• 제27권4호
• /
• pp.407-416
• /
• 2023

The regeneration of myocardium following acute circulatory events remains a challenge, despite numerous efforts. Mesenchymal stem cells (MSCs) present a promising cell therapy option, but their differentiation into cardiomyocytes is a time-consuming process. Although it has been demonstrated that PSME4 degrades acetyl-YAP1, the role of PSME4 in the cardiac commitment of MSCs has not been fully elucidated. Here we reported the novel role of PSME4 in MSCs cardiac commitment. It was found that overnight treatment with apicidin in primary-cultured mouse MSCs led to rapid cardiac commitment, while MSCs from PSME4 knock-out mice did not undergo this process. Cardiac commitment was also observed using lentivirus-mediated PSME4 knockdown in immortalized human MSCs. Immunofluorescence and Western blot experiments revealed that YAP1 persisted in the nucleus of PSME4 knockdown cells even after apicidin treatment. To investigate the importance of YAP1 removal, MSCs were treated with shYAP1 and apicidin simultaneously. This combined treatment resulted in rapid YAP1 elimination and accelerated cardiac commitment. However, overexpression of acetylation-resistant YAP1 in apicidin-treated MSCs impeded cardiac commitment. In addition to apicidin, the universal effect of histone deacetylase (HDAC) inhibition on cardiac commitment was confirmed using tubastatin A and HDAC6 siRNA. Collectively, this study demonstrates that PSME4 is crucial for promoting the cardiac commitment of MSCs. HDAC inhibition acetylates YAP1 and facilitates its translocation to the nucleus, where it is removed by PSME4, promoting cardiac commitment. The failure of YAP1 to translocate or be eliminated from the nucleus results in the MSCs' inability to undergo cardiac commitment.