• Proceedings of the KWS Conference
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• 2002.10a
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• pp.675-680
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• 2002

Cracking and bulging in welded and internally lined pressure vessels that work in thermal-mechanical cycling service have been well known problems in the petrochemical, power and nuclear industries. However, published literature and industry surveys show that similar problems have been occurring during the last 50 years. A better understanding of the causes of cracking and bulging causes is needed to improve the reliability of these pressure vessels. This study attempts to add information required for increasing the knowledge and fundamental understanding required. Typical examples of this problem are the coke drums in the delayed coking units refinery process. This case was selected for experimental work, field study and results comparison. Delayed coking units are among the refinery units that have higher economical yields. To shut down these units represents a high negative economical impact in refinery operations. Also, the maintenance costs associated with repairs are commonly very high. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. To design and operate more robust coke drums with fewer problems, an improved metallurgical understanding of the cracking and bulging mechanisms is required. A methodology that is based field experience revision and metallurgical analyses for the screening of the most important variables, and subsequent finite element analyses to verify hypotheses and to rank the variables according to their impact on the coke drum lives has been developed. This indicated approach provides useful information for increasing coke drum reliability. The results of this work not only order the most important variables according to their impact in the life of the vessels, but also permit estimation of the life spans of coke drums. In conclusion, the current work shows that coke drums may fail as a combination of thermal fatigue and other degradation mechanisms such as: corrosion at high and low temperatures, detrimental metallurgical transformations and plastic deformation. It was also found that FEA is a very valuable tool for understanding cracking and bulging mechanisms in these services and for ranking the design, fabrication, operation and maintenance variables that affect coke drum reliability.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.14
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• pp.5655-5661
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• 2015

Purpose: To assess the role of two adjuvant chemotherapy regimens, anthracycline-based and CMF on disease free survival and overall survival breast cancer patients by meta-analysis approach in Eastern Mediterranean and Asian countries to determine which is more effective and evaluate the appropriateness and efficiency of two different proposed statistical models. Materials and Methods: Survival curves were digitized and the survival proportions and times were extracted and modeled to appropriate covariates by two multivariate mixed effects models. Studies which reported disease free survival and overall survival curves for anthracycline-based or CMF as adjuvant chemotherapy that were published in English in the Eastern Mediterranean region and Asia were included in this systematic review. The two transformations of survival probabilities (Ln (-Ln(S)) and Ln(S/ (1-S))) as dependent variables were modeled by a multivariate mixed model to same covariates in order to have precise estimations with high power and appropriate interpretation of covariate effects. The analysis was carried out with SAS Proc MIXED and STATA software. Results: A total of 32 studies from the published literature were analysed, covering 4,092 patients who received anthracycline-based and 2,501 treated with CMF for the disease free survival and in order to analyze the overall survival, 13 studies reported the overall survival curves in which 2,050 cases were treated with anthracycline-based and 1,282 with CMF regimens. Conclusions: The findings illustrated that the model with dependent variable Ln (-Ln(S)) had more precise estimations of the covariate effects and showed significant difference between the effects of two adjuvant chemotherapy regimens. Anthracycline-based treatment gave better disease free survival and overall survival. As an IPD meta-analysis in the Italy the results of Angelo et al in 2011 also confirmed that anthracycline-based regimens were more effective for survival of breast cancer patients. The findings of Zare et al 2012 on disease free survival curves in Asia also provided similar evidence.

• Journal of the Korean Geographical Society
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• v.42 no.2 s.119
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• pp.218-242
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• 2007

This paper is to consider the developmental process of Korean geography on the context of socio-spatial transformations of Korea, and then to suggest briefly its alternative visions. The development of knowledge including geography seems to be made under imperatives of social functions and structure in a given period, and knowledge in turn gives power for a further development of society. Modem geography in Korea has progressed on the context of capitalist development of Korean society which can be divided into two phases, that is, the period of developmentalism and that of neoliberalism. Korean geography has been developed under influence of ideologies of developmentalism and neoliberalism, and in turn has made some contributions to socio-spatial policies. Korean geography in the future, it can be suggested, should go beyond both developmentalism and neoliberalism, and put socio-spatial welfare, civil society or community, and environmental justice into its central issues.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.207-212
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• 2004

Eddy current (EC) testing methods are widely used in a variety of applications including the inspection of steam generator tubes in nuclear power plants, aircraft parts and airframes. A key factor that affects the EC signal is lift-off which means the physical distance between a sensor and a specimen in the testing. In practice, it is difficult to keep track of the actual value of the lift -off during a specific experiment, simulation or testing in the field, which is essential for accurate interpretation of the signal to be used in the following steps. Hence it is necessary to have a scheme to render the EC signal invariant to the effects of lift-off in spite of the changes in the real world. This paper describes a new method for compensating EC signals for variations in lift-off by acquiring an invariance feature using a homomorphic operator and neural network techniques. The signals from various lift-offs are transformed to obtain a zero lift-off equivalent signal that can be subsequently used for defect characterization in the next step.

• Education of Primary School Mathematics
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• v.16 no.3
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• pp.251-266
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• 2013

With elementary school students who have learned the primary concepts of the four arithmetic operations as its subjects, this study has investigated in depth how schema and transformed schema are composed by recognition of the correct concepts and connection of concepts, that is to say, what schema learners form along with transformed schema with the primary concepts of the four arithmetic operations to understand the secondary concepts when power and mixed calculations are taken into contents. It has also investigated how the subjects use the schema they have formed for themselves and the transformed schema to approach problem solving, and how their composition of concepts and schema in problem solving ability achieve transformations. As a result, we can tell that the recognition of precise primary concepts and transformed schema work as important factors in the development from the primary to the secondary concepts. Here, we can also see learn that the formation of the schema created due to the connection among the primary concepts and the recognition of them and of the transformed schema play more important roles in the development toward the secondary concepts and the solution of arithmetic problems than any other factors.

• Fire Science and Engineering
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• v.31 no.5
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• pp.53-62
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• 2017

Electric power which is the energy source of economy and industries requires long distance transportation due to regional difference between its production and consumption, and it is supplied through the multi-loop transmission and distribution system. Prior to its actual use, electric power flows through several transformations by voltage transformers in substations depending on the characteristics of each usage, and a transformer has the structure consisting of the main body, winding wire, insulating oil and bushings. A transformer fire that breaks out in substations entails the primary damage that interrupts the power supply to houses and commercial facilities and causes various safety accidents as well as the secondary economic losses. It is considered that causes of such fire include the leak of insulating oil resulting from the destruction of bottom part of bushings, and the chain reaction of fire due to insulating oil that reaches its ignition point within 1 second. The smoke detector and automatic fire extinguishing system are established in order to minimize fire damage, but a difficulty in securing golden time for extinguishing fire due to delay in the operation of detector and release of gas from the extinguishing system has become a problem. Accordingly, this study was carried out according to needs of active mechanism to prevent the spread of fire and block the leak of insulating oil, in accordance with the importance of securing golden time in extinguishing a fire in its early stage. A bushings fireproof structure was developed by applying the high temperature shape retention materials, which are expanded by flame, and mechanical flame cutoff devices. The bushings fireproof structure was installed on the transformer model produced by applying the actual standards of bushings and flange, and the full scale fire test was carried out. It was confirmed that the bushings fireproof structure operated at accurate position and height within 3 seconds from the flame initiation. It is considered that it could block the spread of flame effectively in the event of actual transformer fire.

• Journal of the Korean Geographical Society
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• v.50 no.3
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• pp.289-303
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• 2015

This paper is an introductory research to theorize women migrants' positionality in the era of globalization and the feminization of migration. It particularly examines three recent theoretical approaches within feminist studies and their application to the feminist migration study. Migration means a process of continuous negotiations of one's social and material positions within ever changing relations and situations through crossing various borders including national boundaries. Women migrants face multifaceted oppressions due to gendered relation and greater challenges to transform their identities. They embody politics of location through migration. The paper revolves around theories that explore a potential of feminist subjectivation of marginalized women such as female migrants through their identity negotiation and transformation. The theories in questions are Borderlands and the New Mestiza introduced by Gloria $Anzald{\acute{u}}a$, Intersectionality of oppressions, and Transpositions and the Nomadic Subjects by Rosi Braidotti who borrowed the theories of Deleuze and Guattari through feminist critiques. These theories all represent power relations and subject transformations through spatial metaphors. rough spatialized understandings, the paper proposes interlocking relations among space, gender and migration, and explores conceptual tools as well as epistemological insights for Korean migration study.