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대여장비의 신뢰도 기반 예방보전 정책을 통한 최적 의사결정 과정 개발
배기호(Kiho Bae),이주현(Juhyun Lee),박성환(Seonghwan Park),안선응(Suneung Ahn) 한국신뢰성학회 2017 신뢰성응용연구 Vol.17 No.3
Purpose: This study proposes the optimal PM (preventive maintenance) policy of leased equipment for lessee’s decision-making using two types of reliability condition. Methods: We consider reliability threshold based PM model. Equipment reliability is estimated and used as condition variable. The effect of repair for maintenance is imperfect and represented by age reduction factor. Results: We provide two PM policies. Policy 1 is focused on minimized total cost. This policy guarantees reliability threshold until last maintenance action. Policy 2 focus on maintaining reliability threshold during leased period. The proposed approach provides optimal reliability threshold under number of PM. Through result, we finally construct decision-making process for lessee using reliability threshold and end of reliability. Conclusion: This study provides two PM policy for lessee’s decision-making. Through numerical example, we get a result of optimal reliability threshold, number of PM, optimum alternative under lessee’s reliability condition.
반응가스 분압에 따른 박막 프로톤 전도성 고체산화물 연료전지의 구동 특성 분석 연구
배기호(Kiho Bae),장동영(Dong Young Jang),네오 케 체안(Ke Chean Neoh),구준모(Junmo Koo),박석원(Suk Won Park),손지원(Ji-Won Son),심준형(Joon Hyung Shim) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
According to partial pressure of reactant gases, electrochemical performance variation of thin film-protonic ceramic fuel cells (PCFCs) is investigated during fuel cell operation. Concentrations of hydrogen and air are changed from 100% to 50% at the anode and cathode sides, respectively, by controlling flow rates with nitrogen valance. Fuel cell performances were collected each partial pressure conditions at an operating temperature of 600 ℃. Ohmic and polarization resistances were estimated through electrochemical impedance spectroscopy analysis. From the performance comparison, a noticeable result is identified that PCFCs strongly depend on hydrogen partial pressure rather than oxygen partial pressure on it, which is opposite trend of the conventional solid oxide fuel cells.
이트륨이 도핑된 바륨지르코네이트 박막의 바륨 부족 현상에 대한 연구
배기호(Kiho Bae),장동영(Dong Young Jang),심준형(Joon Hyung Shim) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Composition analysis of as-deposited yttrium doped barium zirconate (BZY) films was conducted using X-ray photoelectron spectroscopy (XPS). The BZY films were prepared by pulsed laser deposition (PLD) with variations of target-to-substrate distance (T-S Dis.) and ambient oxygen pressure (PO<SUB>2,amb</SUB>). As a result, barium loss in the PLD was observed from all of the deposited BZY films even though a stoichiometric PLD BZY target was used. It is confirmed that the barium deficiency decreased with increasing the PO<SUB>2,amb..</SUB> The T-S Dis. effect on the barium deficiency was not discernible in the targeted range but the relation between the T-S Dis. and barium deficiency was confirmed from an expended experiment.
Eok-Cheon Kim(김억천),Kiho Bae(배기호),Han Sung Kim(김한성),Yeong-Min Yoo(유영민),Michael Gelinsky(겔린스키 미첼),Tack-Joong Kim(김택중) 한국생명과학회 2016 생명과학회지 Vol.26 No.1
혈관신생의 억제는 암과 같은 신생혈관형성 질환의 치료를 위해 유용한 접근법이다. 신생혈관형성의 핵심인자인 혈관내피세포성장인자는 신생혈관형성 질환의 치료를 위한 주요한 표적이다. 그러므로, 본 연구에서는 in vitro 분석과 ex vivo 동물 실험을 통해 황금 열수추출물의 신생혈관형성 억제효과를 연구했다. 본 연구결과에서 황금 열수추출물이 혈관내피세포성장인자에 의해 자극된 혈관내피세포에 있어 세포독성 없이 세포의 이동, 침투, 관형성을 농도 의존적으로 억제하였다. 더 나아가 황금 열수추출물은 혈관내피세포성장인자에 의해 유도된 흰쥐 대동맥 주변 미세혈관 발아를 예방하였다. 본 연구결과들은 황금 열수추출물이 신생혈관형성 억제작용이 있고, 이는 혈관내피세포성장인자에 의해 유도된 혈관신생을 억제 하는 잠재적 소재가 될 수 있음을 제안한다. Angiogenesis is essential for the pathophysiological processes of embryogenesis, tissue growth, diabetic retinopathy, psoriasis, wound healing, rheumatoid arthritis, cardiovascular diseases, and tumor growth. Inhibition of angiogenesis represents an attractive therapeutic approach for the treatment of angiogenic diseases such as cancer. However, uncontrolled angiogenesis is also necessary for tumor development and metastasis. Inhibition of vascular endothelial growth factor (VEGF) signaling, a critical factor in the induction of angiogenesis, cause robust and rapid changes in blood vessels of tumors and therefore VEGF constitutes a target for such anti-angiogenic therapy. Recently, since natural compounds pose significantly less risk of deleterious side effects than synthetic compounds, a great many natural resources have been assessed for useful substance for anti-angiogenic treatment. Here we evaluated the anti-angiogenic effects of a hot water extract of Scutellaria baicalensis (SBHWE) using in vitro assays and ex vivo animal experiments. Our results show that SBHWE dose-dependently abrogated vascular endothelial responses by inhibiting VEGF-stimulated migration and invasion as well as tube formation in a human umbilical vein endothelial cell (HUVEC) model, without cytotoxicity, as determined by a cell viability assay. Further study revealed that SBHWE prevented VEGF-induced neovascularization in a rat aortic ring sprouting model. Taken together, our findings reveal an anti-angiogenic activity of Scutellaria baicalensis and suggest that SBHWE is a novel candidate inhibitor of VEGF-induced angiogenesis.
YSZ 고체 산화물 연료전지 전해질의 ALD 박막 성장 및 특성 분석
손경식(Kyung Sik Son),배기호(Kiho Bae),심준형(Joon Hyung Shim),배민영(Min Yung Bae),하정숙(Jung Suk Ha) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10
In this study, we have synthesized yttria stabilized zirconia (YSZ) in nanoscale through atomic layer deposition (ALD). Composition of the films has been analyzed by the energy-dispersive spectroscopy and the auger electron spectroscopy. The compositional analysis confirmed that doping concentration of ALD YSZ can be controlled by adjusting zirconium and yttrium source pulsing cycles. The electrochemical ion spectroscopy analysis has been used for measurement of ionic conductivity of the ALD YSZ films.
Constructing a Competing Risks Model for the Combined Structure with Dependent Relations
Seonghwan Park(박성환),Jihyun Park(박지현),Kiho Bae(배기호),Suneung Ahn(안선응) 한국산업경영시스템학회 2017 한국산업경영시스템학회지 Vol.40 No.3
The rapid growth of engineering technology and the emergence of systemized and large-scale engineering systems have resulted in complexity and uncertainty throughout the lifecycle activities of engineering systems. This complex and large-scale engineering system consists of numerous components, but system failure can be caused by failure of any one of a number of components. There is a real difficulty in managing such a complex and large-scale system as a part. In order to efficiently manage the system and have high reliability, it is necessary to structure a system with a complex structure as a sub-system. Also, in the case of a system in which cause of failures exist at the same time, it is required to identify the correlation of the components lifetime and utilize it for the design policy or maintenance activities of the system. Competitive risk theory has been used as a theory based on this concept. In this study, we apply the competitive risk theory to the models with combined structure of series and parallel which is the basic structure of most complex engineering systems. We construct a competing risks model and propose a mathematical model of net lifetime and crude lifetime for each cause of failure, assuming that the components consisting a parallel system are mutually dependent. In addition, based on the constructed model, the correlation of cause of failure is mathematically analyzed and the hazard function is derived by dividing into net lifetime and crude lifetime.