• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.104-108
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• 2018

Experimental studies have been done to examine the aging characteristics by regulator diaphragms of gas pressure, governor room of city gas. Various testing samples with different service periods were manufactured. The results of SEM observation indicated that the surface and thickness of the samples tested were slightly sensitive to the service periods. It was found that as the service periods increased, the tensile strength of diaphragm samples decreased. For samples over 25 years of service, the strength decreased to approximately 60 % of that of new diaphragms. It was also found that as the service periods increased, the elongation increased.

• Journal of applied mathematics & informatics
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• v.41 no.6
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• pp.1155-1171
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• 2023

This paper investigates a non Markovian M/G/1 queue with retrial policy, different kind of service rates as well as unsatisfied clients which is inspired by an example of a transmission medium access control in wireless communications. The server tends to work continuously until it finds at least one client in the system. The server will begin its maintenance tasks after serving all of the clients and if the system becomes empty. Provisioning periods in regular working periods and maintenance service periods should be evenly divided. Using supplementary variable technique, the amount of clients in the system as well as in the orbit were found. Further few performance measures of the system were demonstrated numerically.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1864-1870
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• 2007

The inspection periods for the metro EMU maintenances vary variously according to the countries and railway operators. And the inspection systems vary according to the safety, economical, technical aspects, and also the social environments like passengers and maintenance qualities, etc. Also, in economic point of view, maintenance requires the man power, facilities, equipments, purchasing of parts and the loss of not being in revenue service during the maintenance period. Recently, there is a tendency that the inspection periods are extended gradually owing to the increased reliabilities of the equipments and parts of EMUs. Even if it is the EMUs that are already be in service, once the inspection method is innovated, the inspection time can be reduced. The inspection management innovation scheme includes such methods as the complete module to module replacement when trouble shooting a faulty parts before putting the EMU back to revenue service, the replacements of parts in complete set unit for the heavy maintenance, the establishments of exchange periods for the wasting parts, modernization of inspection equipments, introduction of RAMS for the reliability improvement and computerization of EMU maintenance management, etc. I think it is possible to optimize the inspection scopes and periods per parts and equipments by the introduction of RAMS.

• Korean Journal of Veterinary Service
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• v.27 no.3
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• pp.249-256
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• 2004

The Korea chinese chives are a major edible vegetable and they are traditionally been used as a folk medicine. However recently studies on the Allium tuberosum are mainly on the morphological property and the chemical constituent. There are no reports concerning hematological changes in dogs administrated ethyl acetate extracts of Korea chinese chive. This experiment was conducted to investigate the hematological changes in dogs administrated ethyl acetate extracts of the Korea chinese chives($5m{\ell}/mg$) for 6 days. During administration blood samples were collected at 3h, 6h, 12h and then on daily basis until day 6. Blood samples were analyzed red blood cell(RBC), packed cell volume(PCV), hemoglobin concentration(Hb), mean corpuscular volume(MCV), mean corpuscularl hemoglobin concentration(MCHC), reduced glutathion(GSH), and met-hemoglobin concentration. The RBC count was significantly(p<0.01, p<0.05) decreased during experimental periods. Packed cell volume, hemoglobin concentration were not showed significantly difference during experimental periods. The MCV was significantly(p<0.01, p<0.05) increased from 3 hours after administration to day 4. The MCHC was significantly(p<0.05)decreased on day 6. GSH concentration was not showed significant difference during experimental periods and the met-hemoglobin concentration was significantly(p<0.05) increased on day 3.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.4
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• pp.336-344
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• 2007

A method is developed to evaluate partial safety factors for armor units, by which uncertainties of random variables in reliability function as well as wave height distribution with service periods could take into account straightforwardly. It is found that partial safety factors for resistance and wave height are correctly increased with improving target levels on failure of coastal structures at the same return and service periods. Therefore, it nay be possible to determine design variables through the same processes as those of deterministic method by using the partial safety factors for resistance and wave height evaluated in this paper, since uncertainties of random variables and the effects of service periods and target probability failure are directly considered in the processes of evaluation of partial safety factors.

• The Korean Journal of Food And Nutrition
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• v.27 no.1
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• pp.128-135
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• 2014

The purpose of this study is to analyze the gap in perceived importance-satisfaction rates of foreign Chinese students regarding the university foodservice selection attributes. All statistical analyses are conducted by the SPSS package program (ver 20.0). The results of the statistical analyses are as follows: The validity of the 22 food service selection attributes is being evaluated via the exploratory factor analysis and then five factors are extracted. The five factors are: 'Factor 1. Cleanness and service quality', 'Factor 2. Food quality and price', 'Factor 3. Physical environment', 'Factor 4. Convenience', and 'Factor 5. Service environment'. According to the results of one-way ANOVA, physical environment showed that significant differences across the periods of residence in Korea and the eating frequency at on campus foodservices. On the other hand, the food quality and price, convenience, and service environment showed that significant differences across the periods of residence in Korea. In addition, according to the Importance-Satisfaction Analysis results, 'ventilation of dining room' is the key aspect that university food service managers should reinforce. In conclusion, in order to increase the customer satisfaction rates, the food service managers should not only improve the quality of food and service but also the physical environments of the food service facility.

• Journal of the East Asian Society of Dietary Life
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• v.27 no.5
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• pp.529-539
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• 2017

The aim of this work was to make acorn bread containing natural antioxidants as healthy food. The amylographic characteristics, loaf volume, color, texture, and subjective preference of the acorn bread containing 5~25% of acorn flour were measured during storage at room temperature and in a freezer. The results were as follows: The loaf volume decreased with increasing the addition of acorn flour from 5% to 25%. The onset gelatinization temperature and the value at the peak point of the bread decreased according to the amount of acorn flour added. L-value decreased with the increase of acorn flour contents, but the a- and b- values increased. During the storage period at room temperature, the L, a, and b- value decreased, whereas in the freezer, the L-value decreased except for the bread containing 5~11% acorn flour. In sensory evaluation, color and taste achieved high scores at 18% addition, but low scores at 25% addition. The bitter aftertaste showed low scores according to the addition of acorn flour. The softness and chewiness decreased, but the overall acceptance increased according to the addition of acorn flour except for the bread added with 25% acorn flour. The textural measurements showed that the hardness, springiness, gumminess, and brittleness increased significantly during the storage periods. The cohesiveness, gumminess, and brittleness in room temperature storage decreased with the increase of acorn flour contents. In freezer storage, the addition of acorn flour resulted in the increase of hardness, springiness, gumminess, and brittleness during storage periods. On the other hands, the cohesiveness decreased with the addition of acorn flour. Moreover the addition of acorn flour increased significantly the hardness, gumminess, and brittleness during storage periods. As a result, the bread containing acorn flour showed reasonable textural properties during storage periods.

• Journal of Industrial Technology
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• v.30 no.A
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• pp.45-47
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• 2010

In legacy e-learning web service, as deployed contents are changed, web services should be changed together. In addition, it can not coordinate and manage the various e-learning services recently emerged. In this paper, an e-learning platform based on Service-Oriented Architecture (SOA) is proposed to solve these problems. We design and implement an e-learning system based on Service abstraction layer concepts. The implemented system can provide the new e-learning services within short development periods.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.2
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• pp.377-387
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• 2009

Digital signatures not only provide a way of guaranteeing the integrity of data but also establish the identity of the signer. However, basic digital signature format which contains only the signature of the signer does not guarantee the correctness of its creation time, and it can not remain valid over long periods. This paper proposes a system which integrates timestamp service into digital signatures. The system provides online services for the creation and verification of long term digital signatures which can give the guarantee of the correctness of their creation times and can be proved to be valid over long periods. The proposed system can be used in the various areas such as e-commerce contracts, document archival services, and invoice applications, which requires long term digital signatures. The proposed system is tested with the KRISS timestamp service system.

• Journal of Applied Reliability
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• v.17 no.1
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• pp.58-65
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• 2017

Different from general operating policies applied for various waiting line situations, two complementary dyadic operating policies are applied alternatingly to a single server maintenance service center model. That is, either of the two dyadic Min (N, T) or Max (N, T) policy is applied to operate such center first and the other operating policy should be applied later, and then the same sequence of both operating policies is followed repeatedly. This operating policy is denoted by the Minimax (N, T) policy. Purpose: Because of the newly introduced operating policy, important system characteristics of the considered service center model such as the expected busy and idle periods, the expected number of customers in the service center and so on should be derived to provide necessary information for determination of the optimal operating policy. Methods: Based on concepts of the newly introduced Minimax (N, T) policy, all necessary system characteristics should be redefined and then derived by constructing appropriate relations between complementary two dyadic operating policies. Results: Desired system characteristics are obtained successfully using simple procedures developed by utilizing peculiar structure of the Minimax (N, T) policy. Conclusion: Applying Minimax (N, T) operating policy is equivalent to applying the simple N and T operating policies alternatingly.