• Safety and Health at Work
• /
• 제10권4호
• /
• pp.428-436
• /
• 2019

Background: Metalworking fluids (MWFs) are mixtures with inhalation exposures as mists, dusts, and vapors, and dermal exposure in the dispersed and bulk liquid phase. A quantitative risk assessment was performed for exposure to MWF and respiratory disease. Methods: Risks associated with MWF were derived from published studies and NIOSH Health Hazard Evaluations, and lifetime risks were calculated. The outcomes analyzed included adult onset asthma, hypersensitivity pneumonitis, pulmonary function impairment, and reported symptoms. Incidence rates were compiled or estimated, and annual proportional loss of respiratory capacity was derived from cross-sectional assessments. Results: A strong healthy worker survivor effect was present. New-onset asthma and hypersensitivity pneumonitis, at 0.1 mg/㎥ MWF under continuous outbreak conditions, had a lifetime risk of 45%; if the associated microbiological conditions occur with only 5% prevalence, then the lifetime risk would be about 3%. At 0.1 mg/㎥, the estimate of excess lifetime risk of attributable pulmonary impairment was 0.25%, which may have been underestimated by a factor of 5 or more by a strong healthy worker survivor effect. The symptom prevalence associated with respiratory impairment at 0.1 mg/㎥ MWF was estimated to be 5% (published studies) and 21% (Health Hazard Evaluations). Conclusion: Significant risks of impairment and chronic disease occurred at 0.1 mg/㎥ for MWFs in use mostly before 2000. Evolving MWFs contain new ingredients with uncharacterized long-term hazards.

• 한국진공학회지
• /
• 제8권1호
• /
• pp.31-35
• /
• 1999

본 연구에서는 반도체 소자에서 일렉트로마이그레이션에 기인하는 Al-1%Si 박막배선의 길이 변화에 따른 수명시간 의존도를 조사하였다. 사용된 Al-1%Si 박막배선은 표준 사진식각 공정(standard photolithography process)을 사용하여 제작된 직선형 패턴이다. 직선형 패턴은 100에서 1600 $mu extrm{m}$ 범위의 길이 변화를 갖도록 제작하였다. Ti underlayer가 없는 시편보다 Ti underlayer가 있는 시편에서 Al-1%Si 박막배선의 수명시간이 더 길게 나타났다. Ti underlayer를 갖는 시편에서 electromigration에 대한 저항성을 향상시키는 것으로 사료되어진다. Al-1%Si 박막배선의 길이에 의존하는 수명시간은 800$\mu\textrm{m}$ 이하에서 포화되는 경향을 나타내었다.

• 한국컴퓨터정보학회논문지
• /
• 제15권6호
• /
• pp.65-72
• /
• 2010

에드 혹 네트워크의 각 무선 단말기는 배터리 기반의 제한된 에너지로 동작하기 때문에 효율적인 에너지 사용에 관한 문제는 아주 중요하다. 시스템 수명을 연장하기 위해서는 단말 노드의 에너지 소비를 균형있게 유도하여 어느 특정 단말기의 에너지가 먼저 고갈되어 통신 단절을 초래하는 상황을 지연시켜야 한다. 또한 단말기 노드의 빈번한 이동 등으로 인해 신뢰성이 낮은 링크는 경로 설정시 고려해야 할 요소이다. 본 논문에서 제안하는 CMLR 방법은 잔여 에너지와 링크 에러율, 전송 소비 에너지를 고려한 새로운 비용 관계식을 이용하여 에너지 사용의 효율성을 증가시킨다. 이 방법은 전송 에너지 소모의 최소화와 노드 수명의 최대화 사이의 값을 절충하여 에너지 효율성을 높이고 균형있는 에너지 소비를 유도하여 네트워크 수명을 연장시키도록 하는 방법이다. 또한, 본 논문에서는 시뮬레이션을 통해 제안하는 CMLR의 성능을 검증하였으며, 네트워크 수명과 경로의 효율성 측면에서 볼 때 기존의 알고리즘보다 우수한 결과를 보여주었다.

• Journal of the Korean Data and Information Science Society
• /
• 제4권
• /
• pp.97-107
• /
• 1993

In this paper we propose a nonparametric estimator of the men residual life function (MRLF) on a coherent system under the condition that the component lifetimes are censored by system lifetime. It is shown that the proposed estimator, considered as a function of age t, converges weakly to a Gaussian process on a fixed interval. A consistent estimator of asymptotic variance of the proposed estimator is also given.

• Communications for Statistical Applications and Methods
• /
• 제7권1호
• /
• pp.233-244
• /
• 2000

Confidence intervals for survival function give useful information about the lifetime distribution. In this paper we develop Edgeworkth expansions as approximation to the true and bootstrap distributions of normalized nonparametric maximum likelihood estimator of survival function in the Koziol-Green model and then use these results to show that the bootstrap approximations have second order accuracy.

• 한국국방경영분석학회지
• /
• 제9권2호
• /
• pp.39-43
• /
• 1983

In this paper, we derive the likelihood function for the independent random order statistic whose underlying lifetime distribution is a two parameter Weibull form. For this purpose we first discuss the order statistic which represent a characteristic feature of most life and fatigue tests that they give rise to ordered observations. And, we describe the properties of the underlying Weibull model. The derived likelihood function is essential for establishing the statistical life test plans in the case of Weibull distribution using a likelihood ratio method.

• 인터넷정보학회논문지
• /
• 제10권2호
• /
• pp.153-160
• /
• 2009

무선 센서 네트워크를 위한 데이터 전송의 설계 중에서 가장 중요한 이슈 중 하나는 에너지 효율적인 측면이다. 이를 위해 최근 여러 연구들이 진행되고 있으며 그중에서 가장 대표적인 프로토콜은 SPMS이다. SPMS의 주요 특징 중 하나는 에너지 소비를 줄이기 위한 수단으로 최단경로를 사용한다는 것이다. 그러나 반복적인 최단 경로의 사용으로 인하여 네트워크 라이프타임의 최대화는 불가능하다. 본 논문에서는 에너지 잔존량과 거리를 메트릭으로 사용하는 확률 함수 기반의 데이터 전송 프로토콜을 제안한다. 시뮬레이션 결과, 제안 프로토콜은 에너지 효율적인 데이터 전송을 하며 SPMS보다 네트워크 라이프타임이 약 78%증가하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 D
• /
• pp.1888-1890
• /
• 1999

In this work, we have systematically studied the effects of filtration and the defect trend as a function of polished wafer count using various filters in Inter-Metal Dielectric(IMD) CMP. The filter Installation in CMP polisher makes defect reduced after IMD CMP. As a result of formation micro-scratches, it shows that slurry filter plays an important role in determining consumable pad lifetime. The filter lifetime is dominated by the defects. We have acknowledged slurry filter lifetime is fixed by the degree of generating defects.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.720-723
• /
• 2004

This study is intended to propose a systematic approach for determining optimum Life-Cycle Cost (LCC)-effective seismic design for continuous PSC bridges considering lifetime expected seismic risks. In the paper, a set of cost function for LCC analysis of bridges is proposed. The total LCC functions consist of initial cost and direct/indirect damage costs considering repair/replacement costs, human losses and property damage costs, road user costs, and indirect socio-economic losses. The damage costs are expressed in terms of Park-Ang median global damage indices (Park and Ang, 1985) and lifetime damage probabilities. The proposed approach is applied to model bridges of both moderate seismicity regions like Korea and high seismicity regions like Japan. Since, in case of bridges, a number of parameters may have an influence on optimal target reliability, various sensitivity analyses are performed in this study. It may be expected that the proposed approach can be effectively utilized for the development of cost-effective performance criteria for design and upgrading of various types of bridges as well as continuous PC bridges.

• 한국전기전자재료학회논문지
• /
• 제14권7호
• /
• pp.557-561
• /
• 2001

Chemical mechanical polishing (CMP) process has been widely used to planarize dielectric layers, which can be applied to the integraded circuits for sub-micron technology. Despite the increased use of CMP process, it is difficult to accomplish the global planarization of in the defect-free inter-level dielectrics (ILD). Especially, defects such as micro-scratch lead to severe circuit failure which affect yield. CMP slurries can contain particles exceeding 1㎛ in size, which could cause micro-scratch on the wafer surface. The large particles in these slurries may be caused by particles agglomeration in slurry supply line. To reduce these defects, slurry filtration method has been recommended in oxide CMP. In this work, we have studied the effects of filtration and the defect trend as a function of polished wafer count using various filters in inter-metal dielectrics(IMD)-CMP process. The filter installation in CMP polisher could reduce defects after IMD-CMP process. As a result of micro-scratch formation, it is shown that slurry filter plays an important role in determining consumable pad lifetime. The filter lifetime is dominated by the defects. We have concluded that slurry filter lifetime is fixed by the degree of generating defects.