• Journal of Electrical Engineering and Technology
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• 제7권6호
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• pp.814-823
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• 2012

Electric power transmission utilities make an effort to maximize profit by reducing their electricity supply and operation costs while maintaining their reliability. The development of maintenance strategies for aged components is one of the more effective ways to achieve this goal. The reliability centered approach is a key method in providing optimal maintenance strategies. It considers the tradeoffs between the upfront maintenance costs and the potential costs incurred by reliability losses. This paper discusses the application of the Particle Swarm Optimization (PSO) technique used to find the optimal maintenance strategy for a transmission component in order to achieve the minimum total expected cost composed of Generation Cost (GC), Maintenance Cost (MC), Repair Cost (RC) and Outage Cost (OC). Three components of a transmission system are considered: overhead lines, underground cables and insulators are considered. In regards to aged and aging component, a component state model that uses a modified Markov chain is proposed. A simulation has been performed on an IEEE 9-bus system. The results from this simulation are quite encouraging, and then the proposed approach will be useful in practical maintenance scheduling.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 한국지능정보시스템학회 2005년도 공동추계학술대회
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• pp.516-525
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• 2005

Case-based reasoning (CBR) has been widely used in various areas due to its convenience and strength in complex problem solving. Generally, in order to obtain successful results from CBR, effective retrieval of useful prior cases for the given problem is essential. However, designing a good matching and retrieval mechanism for CBR systems is still a controversial research issue. Most prior studies have tried to optimize the weights of the features or selection process of appropriate instances. But, these approaches have been performed independently until now. Simultaneous optimization of these components may lead to better performance than in naive models. In particular, there have been few attempts to simultaneously optimize the weight of the features and selection of the instances for CBR. Here we suggest a simultaneous optimization model of these components using a genetic algorithm (GA). We apply it to a customer classification model which utilizes demographic characteristics of customers as inputs to predict their buying behavior for a specific product. Experimental results show that simultaneously optimized CBR may improve the classification accuracy and outperform various optimized models of CBR as well as other classification models including logistic regression, multiple discriminant analysis, artificial neural networks and support vector machines.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국해양정보통신학회 2006년도 춘계종합학술대회
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• pp.565-568
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• 2006

In the luminance and chrominance signal, luminance signal creates gray images, and is capable of making each color component compatible with monochrome system. And color components of luminance and chrominance signals are useful to encode or convert the signal because they have low correlation. Each color signal has low correlation statistically, but they are not independent of one another. Therefore, this paper proposes the watermark inserting algorithm for luminance and chrominance signal in the domain of frequency founded on wavelet, considering the interdependent characteristics of color components. Therefore, it can guarantee the robustness and invisible of digital watermark.

• The KIPS Transactions:PartD
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• 제9D권3호
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• pp.417-426
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• 2002

Components are stored in a component repository for later reuse. Effective search and retrieval of desired components in a component repository is a very important issue. It usually takes a lot of time and efforts to gather information about a component, and its availability is essential to implement a repository. Software Component Descriptor proposed in CORBA 3 contains information about a component using an XML vocabulary. In this paper we extend Software Component Descriptor to be useful for the search of a component repository. We use a facet scheme as a search method of a component repository. And our new retrieval method supports queries connected with logical operators such as AND, OR, NOT, which were not supported with existing facet retrieval methods. Also we reduce the search complexity considerably.

• Journal of the Korean Society for Precision Engineering
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• 제26권9호
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• pp.58-63
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• 2009

Silicon carbide (SiC) has been used for many engineering applications because of their high strength at high temperatures and high resistances to chemical degradation. SiC is very useful especially for a glass lens mold whose components demanded to the machining with good surface finish and low surface damage. The performance and reliability of optical components are strongly influenced by the surface damage of SiC during grinding process. Therefore, the severe process condition optimization shall be necessary for the highly qualified SiC glass lens mold. Usually the major form of damage in grinding of SiC is a crack occurs at surface and subsurface. The energy introduced in the layers close to the surface leads to the formation of these cracks. The experimental studies have been carried out to get optimum conditions for grinding of silicon carbide. To get the required qualified surface finish in grinding of SiC, the selection of type of the wheel is also important. Grinding processes of sintered SiC work-pieces is carried out with varying wheel type, depth of cut and feed using diamond wheel. The machining result of the surface roughness and the number of flaws, have been analyzed by use of surface profilers and SEM.

• Journal of the Korea Safety Management & Science
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• 제17권3호
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• pp.185-193
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• 2015

There are so many definition of good work but generally job quality can be useful to analyze the good work. Good work may include some factors about health or working environment. This paper was planned to investigate the level of job quality in Korean employees. Especially comparison of health status between low an high job quality can be analyzed. Korean Working Conditions Survey was used. The various job characteristics were categorized into 6 component of job quality using factor analysis. Statistically mean difference test and cross-tabulation analysis were used to identify the difference of health status and distribution of the level of job quality. The result has shown the different distribution of the level of job quality by the economic sectors and occupations statistically significant. The positive cases of all of six components of job quality was 2.1% of Korean employees and the negative cases of all six components of job quality was 1.5%. The subjective general health status was correlated with job quality but work-related stress was negatively correlated with the level of job quality. This study was heuristic one, more depth analysis will be needed to identify the relationship and causation of job quality and health status.

• YAKHAK HOEJI
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• 제41권4호
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• pp.439-443
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• 1997

From the root bark of Broussonetia kazinoki (Moraceae) two antioxidant components were identified. Their structures were determined as kazinol A (1) and kazinol E (2) (is oprenylated flavan and isoprenylated 1,3-diphenyl propan derivatives) by comparing NMR data with those of the reported compounds from relative plants. The antioxidant activity of 1 and 2 were monitored by the method of DPPH radical scavenging activity, whose $SC_{50}$ values were $41.4{\mu}M\;and\;33.4{\mu}M$, respectively. These compounds also exhibited inhibitory activity against tyrosinase, which is the sole key enzyme for the melanin biosynthesis and play a role in conversion of tyrosine to dopa, and dopa to dopaquinone. The antioxidant effect and the suppression of melanin biosynthesis are useful for anti-aging, increasing vitality in the incidence of major degenerative diseases, and cosmetic products in relation to hyperpigmentation.

• Journal of Korea Trade
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• 제25권2호
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• pp.1-21
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• 2021

Purpose - The purpose of this research is to develop two medical tourism system models which explain medical tourism phenomenon with a systemic approach. Design/methodology - This research was conducted by using a qualitative data analysis which mainly refers to previous references of medical tourism in the areas of tourism and medicine. Leiper's tourism system model was utilized as a conceptual framework. In-depth interviews with experts in the field were conducted in order to pretest the models. Findings - This research suggests a medical tourism system framework and a medical service provision framework. The first model presents medical tourism components and their relationships within a framework presented in a diagram. The second model shows the relationships among medical services required by medical tourists, the service providers, and service human resources along with movements of medical tourists. Originality/value - The first model presents a spatial composition of medical tourism components and their relationships, whereas the second model shows the linkage among medical services, the service providers, and relevant service human resources along with time sequential steps of medical tourists. These two models are complementary and may be used as useful tools to observe medical tourism phenomenon with a systemic and holistic approach. These two models may enable stake holders avoid unnecessary confusions and conflicts that result in duplication of government policies and a waste of budget and human resources.

• The Korean Journal of Blood Transfusion
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• 제29권3호
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• pp.240-252
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• 2018

Viscoelastic coagulation tests provide simultaneous measurements of multiple aspects of whole-blood coagulation, including interactions between the plasma components and cellular components of the coagulation cascade. This can be carried out immediately using a point of care technique. Viscoelastic tests could predict the patient's outcome, including mortality, and detect coagulopathy more sensitively, resulted in reduced blood loss. The transfusion strategy based on the viscoelastic parameters rather than a conventional coagulation test has been shown to reduce the transfusion requirements. Although there are concerns about the reliability and accuracy of this method, viscoelastic tests, including ROTEM, would be a useful method to guide patient blood management strategies.

• Journal of radiological science and technology
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• 제42권4호
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• pp.285-290
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• 2019

Magnetic resonance imaging is a technique specialized in soft tissue imaging with high contrast resolution without in vivo ionization and has been widely used in various clinical settings. In particular, the recent increase in social stress factors has been used in the diagnosis of pituitary adenoma, the incidence increases rapidly. Recently, due to the development of magnetic resonance imaging, it is possible to diagnose micro pituitary adenoma, but despite the use of contrast medium, there has been a difficulty in diagnosing the pituitary adenoma due to its small size and noise. In order to solve this problem, a proposed method of separating signal components image and noise components image from a measured image is applied, and the improvement of diagnostic efficiency is attempted by removing noise. As a result, it was confirmed that the image quality was improved as a whole by applying SNR for 30 subjects data. It is expected that this study will be useful as a pre-processing method for improving the image quality and developing diagnostic indicators of pituitary adenoma.