• 대한안전경영과학회지
• /
• 제7권2호
• /
• pp.141-151
• /
• 2005

EPC seeks to minimize variability by transferring the output variable to a related process input(controllable) variable, while SPC seeks to reduce variability by detecting and eliminating assignable causes of variation. In the case of product control, a very reasonable objective is to try to minimize the variance of the output deviations from the target or set point. We consider an alternative EPC model with second-order autoregressive disturbance. We compare three control systems; EPC, EPC combined with EWMA. This paper shows through simulation that tlhe performance of the integrated model of EPC and EWMA is more preferable than that of EPC.

• 산업경영시스템학회지
• /
• 제33권3호
• /
• pp.146-153
• /
• 2010

When the production run is short and process parameters change frequently, it is difficult to monitor the process using traditional control charts. In such a case, the coefficient of variation (CV) is very useful for monitoring the process variability. The CV control chart is an effective tool to control the mean and variability of process simultaneously. The CV control chart, however, is not sensitive at small shifts in the magnitude of CV. The CV-EWMA(exponentially weighted moving average) control chart which was developed recently is effective in detecting a small shifts of CV. Since the CV-EWMA control chart scheme can be viewed as a weighted average of all past and current CV values, it is very sensitive to small change of mean and variability of the process. In this paper, we propose an FIR(Fast initial response) CV-EWMA control chart to improve the sensitivity of a CV-EWMA scheme at process start-up or out-of-control process. Moreover, we suggest the values of design parameters and show the results of the performance study of FIR CV-EWMA control chart by the use of average run length(ARL). Also, we compared the performance of FIR CV-EWMA control chart with that of the CV-EWMA control chart and we found that the CV-EWMA control chart gives longer in-control ARL and much shorter out-of-control ARL.

• 산업경영시스템학회지
• /
• 제31권4호
• /
• pp.114-120
• /
• 2008

The control chart is widely used statistical process control(SPC) tool that searches for assignable cause of variation and detects any change of process. Generally, ${\bar{X}}-R$ control chart and ${\bar{X}}-S$ are most frequently used. When the production run is short and process parameter changes frequently, it is difficult to monitor the process using traditional control charts. In such a case, the coefficient of variation (CV) is very useful for monitoring the process variability. The CV control chart is an effective tool to control the mean and variability of process simultaneously. The CV control chart, however, is not sensitive at small shift in the magnitude of CV. In this paper, we propose an CV-EWMA (exponentially weighted moving average) control chart which is effective in detecting a small shift of CV. Since the CV-EWMA control chart scheme can be viewed as a weighted average of all past and current CV values, it is very sensitive to small change of mean and variability of the process. We suggest the values of design parameters and show the results of the performance study of CV-EWMA control chart by the use of average run length (ARL). When we compared the performance of CV-EWMA control chart with that of the CV control chart, we found that the CV-EWMA control chart gives longer in-control ARL and much shorter out-of-control ARL.

• 정보처리학회논문지D
• /
• 제15D권5호
• /
• pp.621-628
• /
• 2008

오늘날 대부분의 기업들은 외부상황에 신속하게 비즈니스를 바꿀 수 있도록 하는 온디맨드 비즈니스 (On-demand business)를 구현하기 위해 IT 시스템의 유연성을 필요로 한다. 서비스 지향 아키텍처(Service Oriented Architecture: SOA)는 온디맨드 운영환경에서의 비즈니스 유연성을 가능하게 하는 인프라스트럭처 (infrastructure)를 제공한다. 오늘날의 이러한 요구사항을 충족시키기 위하여 SOA 애플리케이션 개발에 맞게 비즈니스 프로세스의 유연성을 확보하고 재사용을 증진시키기 위한 접근법이 필요하다. 그러므로 본 논문에서는 소프트웨어 프로덕트 라인 방법의 가변성 분석 기법을 사용하여 비즈니스 프로세스 패밀리 (family)에서 나타날 수 있는 가변성을 분석하고 이를 명시적으로 비즈니스 프로세스 패밀리 모델 (Business Process Family Model: BPFM)로 표현하는 방법을 제시한다. 또한 이 방법의 사용을 지원하기 위해 개발한 도구에 대해 설명한다. 이는 BPFM을 모델링하고 BPFM으로부터 가변성 결정과 가지치기 과정을 거쳐 자동 비즈니스 프로세스 모델 (Business Process Model: BPM)을 생성하는 기능들을 가지고 있다. 본 논문에서 제시하는 비즈니스 프로세스 패밀리의 가변성 분석을 통하여 비즈니스와 이를 지원하는 IT 시스템은 비즈니스 환경의 변화에 신속하게 대응할 수 있게 된다.

• 한국정보과학회논문지:소프트웨어및응용
• /
• 제36권5호
• /
• pp.386-395
• /
• 2009

다계층 구조로 설계된 현대의 분산 애플리케이션 아키텍처에서 비즈니스 엔티티는 모든 서비스 로직 컴포넌트들을 관통하는 일종의 횡단관심사(Crosscutting Concerns)이다. 그러므로 비즈니스 엔티티가 변화하면 이와 관련된 서비스 컴포넌트들은 비록 애플리케이션 프레임워크의 공통적인 기능을 구현한 서비스 로직 컴포넌트라 할지라도 새로운 비즈니스 엔티티를 다를 수 있도록 수정되어야 한다. 본 논문에서는 비즈니스 엔티티, 즉 외부화(externalized)된 데이터에 대한 가변성(variability)을 처리하는 DTT 컴포넌트 모델(Data Type-Tolerant Component Model)을 제시한다. DTT 컴포넌트 모델은 SCDT(Self-Contained Data Type)와 가변점(Variation Point) 인터페이스를 통해 프로덕트 라인의 데이터 가변성을 구현 수준에서 구체적으로 표현하고, 서비스 컴포넌트 코드 수정대신 비즈니스 엔티티와 SCDT간 타입 변환을 지원하는 데이터 타입 컨버터를 도입함으로써 애플리케이션 엔지니어링 효율을 향상시킨다. 서비스 컴포넌트가 외부화된 비즈니스 엔티티를 직접 다루지 않고 SCDT 만을 다루게 함으로써 데이터와 함수의 커플링을 다시 컴포넌트 수준에서 로컬화했다는 점이 DTT 컴포넌트 모델의 의의라 할 수 있다.

• 환경영향평가
• /
• 제9권3호
• /
• pp.185-202
• /
• 2000

Uncertainty and variability in Life Cycle Assessment(LCA) have been significant key issues in LCA methodology with techniques in other research area such as social and political science. Variability is understood as stemming from inherent variations in the real world, while uncertainty comes from inaccurate measurements, lack of data, model assumptions, etc. Related articles in this issues were reviewed for classification, distinguish and elaboration of probabilistic/stochastic health risk analysis application in LCA. Concept of focal zone, streamlining technique, scenario modelling and Monte Carlo/Latin Hypercube risk analysis were applied to the uncertainty/variability analysis of health risk in LCA. These results show that this general framework of multi-disciplinary methodology between probabilistic health risk assessment and LCA was of benefit to decision making process by suppling information about input/output data sensitivity, health effect priority and health risk distribution. There should be further research needs for case study using this methodology.

• Journal of Astronomy and Space Sciences
• /
• 제36권3호
• /
• pp.149-157
• /
• 2019

In this study, we investigate the associations between the solar variability and teleconnection indices, which influence atmospheric circulation and subsequently, the spatial distribution of the global pressure system. A study of the link between the Sun and a large-scale mode of climate variability, which may indirectly affect the Earth's climate and weather, is crucial because the feedbacks of solar variability to an autogenic or internal process should be considered with due care. We have calculated the normalized cross-correlations of the total sunspot area, the total sunspot number, and the solar North-South asymmetry with teleconnection indices. We have found that the Southern Oscillation Index (SOI) index is anti-correlated with both solar activity and the solar North-South asymmetry, with a ~3-year lag. This finding not only agrees with the fact that El $Ni{\tilde{n}}o$ episodes are likely to occur around the solar maximum, but also explains why tropical cyclones occurring in the solar maximum periods and in El $Ni{\tilde{n}}o$ periods appear similar. Conversely, other teleconnection indices, such as the Arctic Oscillation (AO) index, the Antarctic Oscillation (AAO) index, and the Pacific-North American (PNA) index, are weakly or only slightly correlated with solar activity, which emphasizes that response of terrestrial climate and weather to solar variability are local in space. It is also found that correlations between teleconnection indices and solar activity are as good as correlations resulting from the teleconnection indices themselves.

• 대한산업공학회지
• /
• 제38권2호
• /
• pp.89-97
• /
• 2012

This paper considers a manufacturer with a two-station make-to-stock and make-to-order serial production system. The MTS facility produces a single type of component and provides components for the MTO facility that produces customized products. In addition to the internal demand from the MTO facility, the MTS facility faces demands from the spot market with the option of to accept or reject each incoming demand. This paper addresses a joint component inventory rationing and batch production control which maximizes the manufacturer's profit. Using the Markov decision process model, we investigate the structural properties of the optimal inventory rationing and batch production policy, and present two types of heuristics. We implement a numerical experiment to compare the performance of the optimal and heuristic policies and a simulation study to examine the impact of the stochastic process variability on the inventory rationing and batch production control.

• 한국경영과학회지
• /
• 제29권3호
• /
• pp.111-127
• /
• 2004

We consider a supply chain model with a make-to-order production facility and a single supplier. The model we treat here is a special case of a two-echelon inventory model. Unlike classical two-echelon systems, the demand process at the supplier is affected by production process at the production facility as well as customer order arrival process. In this paper, we address that how the demand variability impacts on the optimal replenishment policy. To this end, we incorporate Erlang and phase-type demand distributions into the model. Formulating the model as a Markov decision problem, we investigate the structure of the optimal replenishment policy. We also implement a sensitivity analysis on the optimal policy and establish its monotonicity with respect to system cost parameters.

• 한국건설관리학회:학술대회논문집
• /
• 한국건설관리학회 2007년도 정기학술발표대회 논문집
• /
• pp.353-357
• /
• 2007

경제수준 및 주거수준 향상에 따른 생활양식의 변화로 공동주택 입주자의 가족 구성과 주거 선호도가 다변화되고 있다. 이에 따라 라이프 싸이클 및 라이프 스타일 만족을 위한 리모델링과 조기 재건축이 늘어나고 있으며, 공동주택 주거 계획의 핵심요소로써 오픈 하우징의 개념인 "가변성"이 강조되고 있다. 주거공간에 공간 가변성을 채택한 공동주택들은 점진적으로 증가하고 있지만, 구조 안정성, 경제성 및 거주자 사용성을 만족시키는 최적의 공간 가변형 복합구조시스템은 개발되지 못한 실정이다. 따라서 본 논문은 기존 공간 가변형 공동주택의 복합구조시스템 개발과정 및 특성을 분석하여 시스템 평가요소를 도출하고, 이것을 기준으로 각 시스템을 비교${\cdot}$분석하여 국내 실정에 맞는 모듈화된 시스템 개발을 위한 현행 가변형 구조시스템의 개선 방향을 제시하였다.