• 한국신뢰성학회지:신뢰성응용연구
• /
• 제11권4호
• /
• pp.409-417
• /
• 2011

In this paper, we consider a replacement model following the expiration of warranty. In other words, this paper proposes the optimal replacement policy for a repairable system following the expiration of payable renewing replacement-non-renewing minimal repair warranty. The expected cost rate per unit time from the user's perspective is used to determine the optimality of the replacement policy. Thus, we derive the expressions for the expected cycle length and the expected total cost to obtain the expected cost rate per unit time. Finally, the numerical examples are presented for illustrative purpose.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.2205-2210
• /
• 2003

The 1st stage bucket of the 170MW simple cycle gas turbine is one of the components that is normally run in exposed state at the highest thermally stressful environment while the turbine is operating. After certain period operation, various type of damages are easily found and the damages are identified as due to the turbine operating mode of which the demand of the electricity power is very peaking and cyclic. Since this trend is more evident at some part of power plants in Korea and it has caused higher scrap rate of the bucket at the first repair interval than other country. Therefore, demand for the higher capability and alternative technologies which allow salvaging more buckets and preventing from severe damages is always high. In this study, a review and estimation of the repair technologies for the past 5 years to present have been conducted and show results.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제13권2호
• /
• pp.77-86
• /
• 2013

Recently, an extended warranty of a system following the expiration of the basic warranty is becoming increasingly popular to the user. In this respect, we suggest a replacement model following the expiration of extended warranty with minimal repair warranty from the user's point of view in this paper. Under extended warranty, the failed system is minimally repaired by the manufacturer at no cost to the user during the original extended warranty period. As a criterion of the optimality, we utilize the expected cost rate per unit time during the life cycle from the user's perspective and suggest the optimal replacement period after extended warranty. Finally, a few numerical examples are given for illustrative purpose.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
• /
• pp.305-312
• /
• 1999

This study is intended to propose a systematic and practical life cycle cost(LCC) model for the development of the reliability-based seismic safety and cost-effective performance criteria for design and upgrading of long-span PC bridges. The LCC models consist of five cost functions such as initial cost, repair/replacement cost, human losses, road user cost, and indirect losses of regional economy. The proposed model Is successfully expressed in temrs of Park-Ang damage indices and life cycle damage probability obtained from SMART-DRAIN-2DX which is an existing algorithm for nonlinear time history analysis. The proposed LCC model is successfully applied to a viaduct constructed by PSM, in Seoul. Based on the observations, the proposed systematic procedure for the formulation of LCC model may be useful for the development of the reliability-based seismic safety and cost-effective performance criteria for design and upgrading of long-span PC bridges.

• 한국태양에너지학회 논문집
• /
• 제31권1호
• /
• pp.23-30
• /
• 2011

International cooperation to reduce greenhouse gas emissions is expected to provide a big crisis and a great opportunity at the same time for our industry that heavily consumes energy. To cope actively with the international environmental regulation, such as the Framework Convention on Climate Change, quantitative measurement of the volume of greenhouse gases emitted by various industries and quantitative prediction of the greenhouse gas emissions of the future are becoming more important than anything else at the national level. This study aims to propose the calculation process of carbon dioxide($CO_2$) emission for building in life cycle. This paper describes and compares 9 different tool for environmental load estimation with LCA. This study proposed the calculation process for quantitatively predicting and assessing $CO_2$ emissions during the life cycle of buildings based on the life cycle assessment(LCA). The life cycle steps of buildings were divided into the design/supervision, new construction, repair, renovation, use of operating energy in buildings, maintenance, and reconstruction stage in the life cycle inventory analysis and the method of assessing the environmental load in each stage was proposed.

• Smart Structures and Systems
• /
• 제30권6호
• /
• pp.571-582
• /
• 2022

Optimal life-cycle management is a challenging issue for deteriorating regional bridges. Due to the complexity of regional bridge structural conditions and a large number of inspection and maintenance actions, decision-makers generally choose traditional passive management strategies. They are less efficiency and cost-effectiveness. This paper suggests a deep reinforcement learning framework employing double-deep Q-networks (DDQNs) to improve the life-cycle management of deteriorating regional bridges to tackle these problems. It could produce optimal maintenance plans considering restrictions to maximize maintenance cost-effectiveness to the greatest extent possible. DDQNs method could handle the problem of the overestimation of Q-values in the Nature DQNs. This study also identifies regional bridge deterioration characteristics and the consequence of scheduled maintenance from years of inspection data. To validate the proposed method, a case study containing hundreds of bridges is used to develop optimal life-cycle management strategies. The optimization solutions recommend fewer replacement actions and prefer preventative repair actions when bridges are damaged or are expected to be damaged. By employing the optimal life-cycle regional maintenance strategies, the conditions of bridges can be controlled to a good level. Compared to the nature DQNs, DDQNs offer an optimized scheme containing fewer low-condition bridges and a more costeffective life-cycle management plan.

• 대한의생명과학회지
• /
• 제29권4호
• /
• pp.287-295
• /
• 2023

Amifostine was developed to protect cells, but it is known to induce cytotoxicity and apoptosis, and the exact mechanism is unknown. In this study, we investigated how the DNA mismatch repair (MMR) system interacts with p53 to prevent apoptosis, cell cycle arrest, and cytoprotective effects induced by amifostine. HCT116 colon cancer cells sublines HCT116/p53+,HCT116/p53+, HCT116/p53-, HCT116/E6 and HCT116+ch3/E6 cells were used for evaluation. Amifostine induced G1 arrest and increased toxicity two-fold in p53- cells regardless of MMR expression. Both G1 cell cycle arrest and induction of p53 protein peaked at 24 h after the start of amifostine exposure. Both G1 cell cycle arrest and induction of p53 protein peaked at 24 h after the start of amifostine exposure. Amifostine induced the expression of p21 protein in both p53+ and p53- cells. As for apoptosis, compared to p53- cells, p53+ cells showed 3.5~4.2 times resistance to amifostine-induced apoptosis. HCT116+E6 with both p53 and MMR loss showed maximum apoptosis at 48 h, and HCT116+ch3/E6HCT116+ch3/E6 with p53 loss showed maximum apoptosis at 24 h. As a result, it was confirmed through in vitro experiments that amifostine-induced G1 cell cycle arrest and apoptosis are mediated through a pathway dependent on MMR and p53 protein.

• 한국전산구조공학회논문집
• /
• 제18권4호통권70호
• /
• pp.445-452
• /
• 2005

본 논문에서는 강박스 거더의 생애주기비용을 최소화하기 위한 방법을 제시하였다. 본 논문에서 고려된 강박스 거더의 생애주기비용은 초기비용, 유지관리비용 및 보수비용으로 구성되었다. 강재 주형의 상태등급곡선과 안전진단 결과 측정된 내하력을 바탕으로 내하력곡선을 추정하였으며, 이 곡선을 이용하여 생애주비용을 고려한 강박스 거더의 최적설계를 수행하였다. 또한 내하력곡선을 통해 강박스 거더의 공용수명과 보수 보강 시기 및 횟수를 결정하고 초기 내하력에 따른 생애주기 동안 발생하는 연간비용을 비교, 분석하였다. 본 논문에서 제안한 생애주기비용을 고려한 강박스 거더의 최적설계를 통하여 기존의 설계에 비해 보다 경제적이며 안전한 설계를 유도할 수 있으리라 판단된다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권17호
• /
• pp.7043-7048
• /
• 2014

Inhibition of heat shock protein 90 (Hsp90) leads to inappropriate processing of proteins involved in DNA damage repair pathways after DNA damage and may enhance tumor cell radio- and chemotherapy sensitivity. To investigate the potentiation of antitumor efficacy of lidamycin (LDM), an enediyne agent by the Hsp90 inhibitorgeldanamycin (GDM), and possible mechanisms, we have determined effects on ovarian cancer SKOV-3, hepatoma Bel-7402 and HepG2 cells by MTT assay, apoptosis assay, and cell cycle analysis. DNA damage was investigated with H2AX C-terminal phosphorylation (${\gamma}H2AX$) assays. We found that GDM synergistically sensitized SKOV-3 and Bel-7402 cells to the enediyne LDM, and this was accompanied by increased apoptosis. GDM pretreatment resulted in a greater LDM-induced DNA damage and reduced DNA repair as compared with LDM alone. However, in HepG2 cells GDM did not show significant sensitizing effects both in MTT assay and in DNA damage repair. Abrogation of LDM-induced $G_2/M$ arrest by GDM was found in SKOV-3 but not in HepG2 cells. Furthermore, the expression of ATM, related to DNA damage repair responses, was also decreased by GDM in SKOV-3 and Bel-7402 cells but not in HepG2 cells. These results demonstrate that Hsp90 inhibitors may potentiate the antitumor efficacy of LDM, possibly by reducing the repair of LDM-induced DNA damage.

• 한국시뮬레이션학회논문지
• /
• 제20권3호
• /
• pp.119-127
• /
• 2011

전면정비란 일정기간동안 사용한 장비(기계, 설비 등)를 부품 단위로 분해하여 부품별로 수리를 한 후 재조립하는 과정을 의미다. 전면정비는 주로 항공기, 선박, 철도차량, 무기체계, 중장비 등과 같이 수명이 길고 고가인 장비를 운영하는 과정에서 발생한다. 이러한 정비 사업에서는 리드타임(Lead Time)을 단축시키는 것이 중요하며, 납기에 맞추어 정비를 완료할 수 있도록 생산시스템을 설계하는 것이 주요 관심사이다. 본 논문에서는 전면정비를 하는 정비 공장을 대상으로 3D시뮬레이션 도구인 $QUEST^{TM}$를 이용하여 시뮬레이션을 수행한 사례를 소개한다. 먼저 전면정비 공장의 공정특성과 시뮬레이션 모델 구축시 고려해야 하는 사항들을 중점적으로 설명하였다. 그리고 흐름생산방식과 셀생산방식 등 두 가지 해체작업 방식을 포함한 다양한 시뮬레이션 시나리오에 대해 시뮬레이션 실험을 통한 분석결과를 제시하였다.