• Journal of the Korean Institute of Gas
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• v.15 no.5
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• pp.1-6
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• 2011

It is required to construct the pipelines to eliminate pressure drop at the end of transmission line under limitation of maximum operation pressure of 6.86 MPa, however, it highly costs to build the pipelines and takes time-consuming job. Higher operation pressure compared to current operating pressure has been considered to resolve the problem of pressure drop without modification of the existing pipelines and facilities. As a result of the integrity evaluation, the existing pipelines can be operated up to 7.85 MPa in terms of wall thickness and have higher Charpy impact energy than required value in the ASME B31.8. However, Increment of operation pressure gives rise to increase potential impact area if the pipelines burst due to third party damages.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.04a
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• pp.83-86
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• 1996

In this paper we study the problem of augmenting a physical network to improve the topology for new survivable network architectures. We are given a graph G=(V,E,F), where V is a set of nodes that represents transmission systems which be interconnected by physical links, and E is a collection of edges that represent the possible pairs of nodes between which a direct transmission link can be placed. F, a subset of E is defined as a set of the existing direct links, and E/F is defined as a set of edges for the possible new connection. The cost of establishing network $N_{H}$=(V,H,F) is defined by the sum of the costs of the individual links contained in new link set H. We call that $N_{H}$=(V,H,F) is feasible if certain connectivity constrints can be satisfied in $N_{H}$=(V,H,F). The computational goal for the suggested model is to find a minimum cost network among the feasible solutions. For a k edge (node) connected component S .subeq. F, we charactrize some optimality conditions with respect to S. By this characterization we can find part of the network that formed by only F-edges. We do not need to augment E/F edges for these components in an optimal solution. Hence we shrink the related component into a node. We study some good primal heuristics by considering construction and exchange ideas. For the construction heuristics, we use some greedy methods and relaxation methods. For the improvement heuristics we generalize known exchange heuristics such as two-optimal cycle, three-optimal cycle, pretzel, quezel and one-optimal heuristics. Some computational experiments show that our heuristic is more efficient than some well known heuristics.stics.

• Progress in Medical Physics
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• v.4 no.2
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• pp.59-67
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• 1993

In this paper, we present a result of our study on how to construct a HIMCS(hospital image management and communication system) based on Windows system. The proposed HIMCS is composed of image acquisition units, image archiving and processing units, display units, and all units are interfaced with LAN. We construct high speed image transmission system for distributed database and retrieval of various medical pictures in ward through image transmission system and realize integrated image diagnosis. Hospital image management and communication systems(HIMCS) have been proposed as a way to meet the challenge presented by the growing volume of medical imaging data. These systems are based on the concept of handing images in digital form, there by marking use of advances in computer-based technology. A HIMCS offers a wide spectrum of advantages over filmbased imaging. Digital acquisition of images eliminates the need for film processing and associated costs in both time and materials.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.539-546
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• 2014

PURPOSE. Silk fibroin (SF) is a new degradable barrier membrane for guided bone regeneration (GBR) that can reduce the risk of pathogen transmission and the high costs associated with the use of collagen membranes. This study compared the efficacy of SF membranes on GBR with collagen membranes (Bio-$Gide^{(R)}$) using a rat calvarial defect model. MATERIALS AND METHODS. Thirty-six male Sprague Dawley rats with two 5 mm-sized circular defects in the calvarial bone were prepared (n=72). The study groups were divided into a control group (no membrane) and two experimental groups (SF membrane and Bio-$Gide^{(R)}$). Each group of 24 samples was subdivided at 2, 4, and 8 weeks after implantation. New bone formation was evaluated using microcomputerized tomography and histological examination. RESULTS. Bone regeneration was observed in the SF and Bio-$Gide^{(R)}$-treated groups to a greater extent than in the control group (mean volume of new bone was $5.49{\pm}1.48mm^3$ at 8 weeks). There were different patterns of bone regeneration between the SF membrane and the Bio-$Gide^{(R)}$ samples. However, the absolute volume of new bone in the SF membrane-treated group was not significantly different from that in the collagen membrane-treated group at 8 weeks ($8.75{\pm}0.80$ vs. $8.47{\pm}0.75mm^3$, respectively, P=.592). CONCLUSION. SF membranes successfully enhanced comparable volumes of bone regeneration in calvarial bone defects compared with collagen membranes. Considering the lower cost and lesser risk of infectious transmission from animal tissue, SF membranes are a viable alternative to collagen membranes for GBR.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.372-378
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• 2018

Life management technology is required as the failure risk of aged power transformers increases. Asset management technology is developed to evaluate the remaining life, establish the replacement strategies, and decide the optimal investment based on the reliability and economy of power transformers. The remaining life assessment uses data such as installation, operation, maintenance, refurbishment, and failure of power transformers. The optimal investment also uses data such as maintenance, outage, and social costs. To develop the asset management system for power transformers, determining the degradation parameters related to the aging of power transformers and evaluating the condition of power transformers using these parameters are important. In this study, since 1983, 110,000 Dissolved Gas Analysis (DGA) data have been analyzed to determine the degradation parameters related to the aging of power transformers. The alarm rates of combustible gases ($H_2$, $C_2H_2$, $C_2H_4$, $CH_4$, and $C_2H_6$), TCG, CO, and $CO_2$ were analyzed. The end of life and failure rate (bathtub curve) of power transformers were also calculated based on the failure data from 1981 to 2014. The DGA gases related to discharge, overheating, and insulation degradation were determined based on alarm and failure rates. $C_2H_2$, $C_2H_6$, and $CO_2$ were discharge, oxidation, and insulation degradation parameters related to the aging of power transformers.

• Pediatric Infection and Vaccine
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• v.28 no.2
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• pp.57-65
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• 2021

School closures during the coronavirus disease 2019 (COVID-19) pandemic have been outlined in studies from different disciplines, including economics, sociology, mathematical modeling, epidemiology, and public health. In this review, we discuss the implications of school closures in the context of the current COVID-19 pandemic. Modeling studies of the effects of school closures, largely derived from the pandemic influenza model, on severe acute respiratory syndrome coronavirus 2 produced conflicting results. Earlier studies assessed the risk of school reopening by modeling transmission across schools and communities; however, it remains unclear whether the risk is due to increased transmission in adults or children. The empirical findings of the impact of school closures on COVID-19 outbreaks suggest no clear effect, likely because of heterogeneity in community infection pressure, differences in school closure strategies, or the use of multiple interventions. The benefits of school closings are unclear and not readily quantifiable; however, they must be weighed against the potential high social costs, which can also negatively affect the health of this generation.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.2
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• pp.8-15
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• 2009

The need for ASP(Application Service Provider) has evolved from the increasing costs of specialized software that have far exceeded the price rage of small to medium sized businesses. There are a lot of technologies that make ASP possible, and software streaming service is one of them Software streaming is a method for overlapping transmission and execution of stream-enabled software. The stream-enabled software is able to run on a device even while the transmission/streaming of the software may still be in progress. Thus, a user does not have to wait for the completion of the software's download prior to starting to execute the software. In this paper, we suggest the new concept of software streaming system implement using the PageFault Interrupt Routine Hooking. As it is able to efficiently manage application, we do not have to install the entire software. In addition, we can save hardware resources by using it because we load basic binaries without occupying the storage space of the hardware.

• ETRI Journal
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• v.37 no.2
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• pp.295-305
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• 2015

The purpose of this paper is to a develop model for generation expansion planning that can support diverse environmental policies for the reduction of greenhouse gases (GHGs) of South Korea. South Korea is required to reduce its GHG emissions by 30% from the BAU level by 2020. The Wien Automatic System Planning Package currently used in South Korea has limitations in terms of the application of renewable energy policies and GHG targets; this paper proposes the use of an equipment planning model named generation and transmission expansion program, which has been developed to resolve such limitations. For verification of the model, a case study on the 6th Basic Plan of Long-Term Electricity Supply and Demand has been conducted. The results show that for the year 2020 South Korea's annual GHG emissions will be 36.6% more than the GHG Target Management System (GHG TMS) target set for the same year (30%). To achieve the GHG TMS target, the costs involved amount to about 72 trillion KRW (70 billion USD). Consequently, the South Korean government needs to review the performability of this target.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.11
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• pp.612-620
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• 2017

Power consumption in Southeast Asia is steadily increasing due to industrialization and the effects of hot and humid climates. However, there are not enough energy generation facilities and infrastructures to meet the growing demand because it is difficult to secure the construction and operation costs of the transmission and distribution systems. This study aims to develop a gas engine driven heat pump system that supplies heating, cooling and electric power to buildings. This system, besides its normal function to produce heat, has the capacity to generate electricity on a household level. This paper investigates similar cases overseas before developing the system. Through the investigation of commercialized similar systems, the level of technology and market trend of development system were identified. Features and specifications of commercial and industrial systems will be used for system development.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.8
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• pp.1269-1277
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• 2008

Ships at sea cannot exchange data among them easily so far. Basically voice-oriented communication systems are the main methods, some of them utilize the HF radio systems at lower bit rates, and for higher bit rates, the Inmarsat or VSAT are adopted. None of them are used widely because of lower qualities and higher costs. There exist many technical and economical limits to have the Internet service just like on land such as the WWW service. In order to achieve the improved transmission rates of the maritime communication networks at farther sea, MANET(Mobile Ad Hoc Network) is one of the most practical models. In this paper, a new routing protocol named EZR (Expansive Search Zone Routing Protocol) is proposed, which is based on SANET (Ship Ad Hoc Network) model that has some different features from MANET and VANET (Vehicular Ad Hoc Network). The search zone for the shortest path is firstly found by EZR. If no path is searched in the zone, the zone is expanded according to the rule of EZR. The zone-expanding and path-searching procedures are repeated until the path is found out. The performance of EZR is evaluated and compared with LAR protocol which is one of the most typical routing protocols based on geographical information. The simulated results show that EZR is much better than LAR at sea environments in terms of routing success rate, route optimality, and a single index of performance combined the previous two metrics.