• 대한수학회지
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• 제35권1호
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• pp.207-224
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• 1998

After the review of known results on the connections between selfsimilar processes with independent increments (processes of class L) and selfdecomposable distributions and between semi-selfsimilar processes with independent increments and semi-selfdecomposable distributions, dichotomy of those processes into transient and recurrent is discussed. Due to the lack of stationarity of the increments, transience and recurrence are not expressed by finiteness and infiniteness of mean sojourn times on bound sets. Comparison in transience-recurrence of the Levy process and the process of class L associated with a common distribution of class L is made.

• 지질공학
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• 제29권4호
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• pp.367-381
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• 2019

We investigate pore pressure conditions and reservoir compaction associated with oil and gas production using 3 different permeability models, which are all based on one-dimensional radial flow diffusion model, but differ in considering permeability evolution during production. Model 1 assumes the most simplistic constant and invariable permeability regardless of production; Model 2 considers permeability reduction associated with reservoir compaction only due to pore pressure drawdown during production; Model 3 also considers permeability reduction but due to the effects of both pore pressure drawdown and coupled pore pressure-stress process. We first derive a unified stress-permeability relation that can be used for various sandstones. We then apply this equation to calculate pore pressure and permeability changes in the reservoir due to fluid extraction using the three permeability models. All the three models yield pore pressure profiles in the form of pressure funnel with different amounts of drawdown. Model 1, assuming constant permeability, obviously predicts the least amount of drawdown with pore pressure condition highest among the three models investigated. Model 2 estimates the largest amount of drawdown and lowest pore pressure condition. Model 3 shows slightly higher pore pressure condition than Model 2 because stress-pore pressure coupling process reduces the effective stress increase due to pore pressure depletion. We compare field data of production rate with the results of the three models. While models 1 and 2 respectively overestimates and underestimates the production rate, Model 3 estimates the field data fairly well. Our result affirms that coupling process between stress and pore pressure occurs during production, and that it is important to incorporate the coupling process in the permeability modeling, especially for tight reservoir having low permeability.

• 한국전자거래학회지
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• 제15권1호
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• pp.89-101
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• 2010

치열한 글로벌 경쟁에서 기업의 경쟁력이 제품 측면에서 점차 서비스 측면으로 옮겨가고 있다. 이는 치열한 경쟁 상황 등으로 인해 제품 생산 비용이나 제품의 품질에서 차별화를 확보하기 힘들어지고 수요의 불확실성과 동적인 시장 상황으로 인해 점차 유연성과 대응성 등 서비스 측면이 차별화 요인으로 대두되고 있기 때문이다. 기업의 유연성과 대응성은 기업의 판매주문처리를 통해 다른 기업들에게 평가된다. 따라서 기업은 판매주문처리에 관심을 가져야 한다. 그러나 기존의 판매주문처리 관련 연구들은 주로 생산 비용을 최소화하기 위한 납기 결정과 생산 일정 수립 및 납기 준수를 위한 리드타임 결정에 비중을 두고 있다. 이는 지금까지 판매주문처리 관련 연구들이 대상으로 하는 목적함수가 비용 관련 요소에 비중을 두고 있었으며, 유연성과 대응성 향상을 위한 고객과의 유연하면서 긴밀한 연결 비용과 실시간 주문 관련 정보 취득 비용이 높았기 때문이다. 그러나 정보 기술(IT)과 유비쿼터스 기술(UT)의 발전으로 점차 연결성과 가시성 확보와 관련한 비용이 줄었으며 기술적으로 구현 가능해지고 있다. 본 연구에서는 정보 기술과 유비쿼터스 기술의 발전으로 인해 변화된 기업의 판매주문관리에서의 유연성과 대응성 향상을 위해 납기를 재협의하는 프로세스와 이를 지원하기 위해 로제타넷 PIP(Partner Interface Process) 기반의 비즈니스 통합 모델을 제안하고자 한다.

• 한국콘텐츠학회논문지
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• 제19권9호
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• pp.376-387
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• 2019

도시화에 따른 인구 집중으로 지방 분권 및 지역균형발전의 역할이 중요해지며 지자체에 관광 콘텐츠 개발도 활발히 시도되고 있지만, 이러한 시도는 대다수 양적인 성장에 치우쳐 지역적 특색을 살리고 차별화된 경험을 제공하는 관광 콘텐츠를 효과적으로 제시하고 있지 못한 실정이다. 결국, 지역 특색을 가꾸어 지역의 정체성을 강조하고 차별화된 이미지를 구축할 수 있는 프로그램과 콘텐츠를 개발하는 것이 중요하지만 특징적 자원 발굴이 어려운 대부분의 소규모 지역은 상대적으로 적은 개발기회와 재정적 제약으로 인해 차별화된 프로그램과 콘텐츠 개발이 어렵다는 문제가 있었다. 본 연구에서는 이러한 소규모 지역의 특징적 콘텐츠 발굴은 지역의 특징을 분석하고 보유한 자산을 최대한 이용하는 것이 효과적이라고 보고, 대안적 측면에서 지역 생태 자산을 이용한 지역 활성화 방안 중 하나인 생태관광을 효과적으로 지원하는 서비스디자인 프로세스를 제안하였다. 그 과정에서 벤 다이어그램 포지션, 콘텍스트 맵 방법론을 개발하여 수통골 자연관찰로를 통해 검증하였다.

• 한국기계가공학회지
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• 제19권10호
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• pp.68-73
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• 2020

The proportion of airline accidents caused by human factors is steadily increasing. The aviation industry has made considerable progress in reducing the accident rate; however, since the early 1980s, the accident rate has remained constant. Due to airspace congestion, the safety margins of these existing safety promotion methods are gradually decreasing; thus, new methods to prevent accidents and quasi-accidents must be devised. Causative factors of aviation accidents include increased air traffic due to increased air demand, increased cumulative working hours due to long-distance flights, and complicated flight environments. Accidents often occur when several small errors accumulate in the normal course of operation, rather than after a single error. Accordingly, in this study, the impacts on air navigation due to human error by aviation maintenance personnel and varying international standards (i.e., KOCA vs. F.A.A vs. EASA) analyzed, and the relationship between human decision-making and behavior was investigated. The resulting safety analysis and alternatives were presented to prevent aviation maintenance accidents and cognitive ergonomics errors.

• 사회복지연구
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• 제42권4호
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• pp.239-262
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• 2011

본 논문에서는 우리 헌법에서 수용하고 있는 적법절차원칙에 비추어, 현행 국민기초생활보장법에서 급여변경 및 중지시 적용되는 절차의 적정성을 고찰한다. 동법에서는 사후적인 이의신청절차만을 명시하고 있으며, 분쟁을 심사하는 심판자의 독립성을 보장하는 장치가 마련되지 않은 한계가 있다. 그 결과 수급자는 행정기관의 일방적인 조치에 의해 급여가 박탈되어 즉각적인 생계위협을 겪고, 구제절차에서도 공정한 심판을 받지 못하는 불이익을 당하기 쉽다. 급여의 변경 및 중지는 수급자의 헌법적 또는 법률적 권리를 제한하는 행정작용으로서 적법절차원칙에 따라 절차의 공정성과 합리성이 요구된다고 본다. 급여 변경 및 중지의 경우 적법절차를 만족하기 위해서는, 이의신청 기회가 해당 조치 시행 전에 마련되어야 하며, 심판자의 독립성이 적절한 수준에서 보장되고, 이 때 수급자가 심판자 앞에서 구두로 의견을 표현할 기회가 제공되는 등 절차적 보호장치가 마련되어야 한다. 이를 위해 행정절차법상의 청문절차를 적용하는 것이 적합하다고 보며, 이에 급여변경 또는 중지시 수급자의 청문에의 기회를 권리로서 보장하도록 국민기초생활보장법을 개정해야 한다고 주장한다.

• 산업경영시스템학회지
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• 제43권3호
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• pp.95-100
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• 2020

Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. The representative type of the degeneration is wear of tool or machine. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore a periodic preventive resetting the process is necessary. The total cost consists of three items: adjustment cost (or replacement cost), non-conforming cost due to product out of upper or lower limit specification, and quality loss cost due to difference from the process target value and the product characteristic value among the conforming products. In this case, the problem of determining the adjustment period or wear limit that minimizes the total cost is called the 'process mean shift' problem. It is assumed that both specifications are set and the wear level can be observed directly. In this study, we propose a new model integrating the quality loss cost, process variance, and production volume, which has been conducted in different fields in previous studies. In particular, for the change in production volume according to the increasing in wear level, we propose a generalized production quantity function g(w). This function can be applied to most processes and we fitted the g(w) to the model. The objective equation of this model is the total cost per unit wear, and the determining variables are the wear limit and initial process setting position that minimize the objective equation.

• 산업경영시스템학회지
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• 제44권1호
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• pp.45-50
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• 2021

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point. The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the 'process mean shift problem'. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권4호
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• pp.273-285
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• 2013

Because process variations have direct influence on yield rate in process industry, it is very important to understand process variations that occur accidentally. In process industry, quality variation due to the activities of process improvement and maintenance and chance effect such as change of work environment and difference in staffs' craftsmanship are mixed with each other, therefore it is difficult to actually detect minute process variations. In this study, objective and rational methods of detection that can detect minute process variations in process industry were designed referring to various methodologies of process management, and they were verified through similar examples.

• Membrane and Water Treatment
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• 제9권5호
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• pp.335-342
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• 2018

Micelle-Enhanced Ultrafiltration (MEUF) is a membrane separation processes that improving ultrafiltration process with the formation of micelles of the surface active agents. Surface active agents are widely used to improve membrane processes due to the ability to trap organic compounds and metals in the treatment of industrial waste water. In this study, surface active agents are used to improve micelle-enhanced ultrafiltration (MEUF) to reduce chemical oxygen demand (COD), total dissolved solid (TDS), turbidity and clogging the membrane in dairy wastewater treatment. Three important operational factors (anionic surface active agent concentration, pressure and pH) and these interactions were investigated by using response surface methodology (RSM) and Box-Behnken design. Results show that due to the concentration polarization layer and increase the number of Micelles; the anionic surface active agent concentration has a negative effect on the flux and has a positive effect on the elimination of contamination indices. pH, and the pressure have the greatest effect on flux. On the other hand, it could be stated that these percentages of separation are in the percentages range of Nano-filtration (NF). While MEUF process has higher flux than NF process. The results have been achieved at lower pressure while NF process needs high pressure, thus making MEUF is the replacement for the NF process.