• Journal of the Korean Mathematical Society
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• v.35 no.1
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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.

• The Journal of Engineering Geology
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• v.29 no.4
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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.

• The Journal of Society for e-Business Studies
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• v.15 no.1
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• pp.89-101
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• 2010

In some industries, manufacturing firms' distinctive competences include not only product superiority but also service excellence. For example, in a highly volatile and dynamic market, flexibility and responsiveness are more valued than just the product cost. And sales order processing, in that respect is a very important process. However, previous studies on sale order processing have considered only due-date assignments or dealt with production scheduling to minimize production cost or delivery lead time. Due to recent advances in information technology, a new approach is possible in dealing with sales order processing. For example, RFID(Radio Frequency IDentification) and ubiquitous computing technology adds real time visibility and traceability to supply chain. In this study, we develop a new due-date re-negotiation process for sales order management and propose a new business integration model to support the re-negotiation process based on RFID, ubiquitous computing technology and RosettaNet's PIPs.

• The Journal of the Korea Contents Association
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• v.19 no.9
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• pp.376-387
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• 2019

The role of local decentralization and balanced regional development becomes important due to the concentration of population due to urbanization, and the development of tourism contents in local governments is actively being attempted. However, this is largely due to quantitative growth, and it does not offer tourist content that offers a different experience while utilizing regional characteristics. This means that it is important to develop programs and contents that emphasize the identity of the region by cultivating local characteristics and build a different image. However, most of the small regions where characteristic resources are difficult to find have a problem that it is difficult to develop different programs and contents due to relatively few development opportunities and financial constraints. In this study, it was considered that it is effective to analyze characteristic features of the region and utilize the possessed assets as much as possible. Therefore, we propose a service design process that effectively supports ecotourism, one of the regional revitalization plan using local eco - assets. In the process, Venn Diagram Position and Context Map methodology was developed and verified through Sutonggol Observation Path.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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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.

• Korean Journal of Social Welfare Studies
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• v.42 no.4
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• pp.239-262
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• 2011

The Korean government's recent large-scale termination and modification of welfare benefits revealed a procedural problem under the National Basic Living Security Act. Under the Act, welfare recipients have a legal right to make complaints only after the termination or modification is enforced; the Act fails to provide the recipients with an opportunity for a hearing before termination or modification, and this creates serious threats to the recipients, whose livelihoods are dependent on welfare benefits. Korean jurisprudence has adopted the due process of law principle. The principle originated from the due process in US jurisprudence, and Korea has applied it broadly to any government actions that restrict individuals' constitutional or legal rights. This paper reviews the termination or modification procedure under the Act with the lens of the due process principle and criticizes that the current law is not in compliance with the principle. In supporting that such termination and modification procedure infringes on welfare recipients' protected rights, this paper discusses two theories as to what rights are protected. First, termination or modification of welfare benefits can be considered as deprivation of property. The 'property' theory may be weak under Korean jurisprudence, because the concept of property under the Korean Constitution is narrowly construed. Second, this paper relies on the constitutional provision that recognizes "the right to a life worthy of human beings," which requires the State to guarantee minimum standard of living for all. As welfare recipients are deemed to receive benefits as a right under the Constitution, any deviation from the minimum requirement would constitute a violation of constitutional rights. In any case, termination or modification of welfare benefits that are concretized under the Act should be protected under the due process principle, because the principle would cover any government actions that restrict established legal rights. This paper argues that the procedural due process requires the recipients be guaranteed an opportunity to have a hearing before the termination or modification is enforced. An independent decision-maker should hear the proceedings, and the recipients should have an option to orally present their opinions in front of the decision-maker. The hearing process under the Administrative Procedures Act of Korea offers elements that would satisfy these procedural requirements. Thus, this paper concludes that the National Basic Living Security Act should be amended to adopt the hearing process under the Administrative Procedures Act in its termination and modification procedure.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.3
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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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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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.

• Journal of Applied Reliability
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• v.13 no.4
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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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• v.9 no.5
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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.