• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1436-1445
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• 2021

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

• Design & Manufacturing
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• v.16 no.4
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• pp.34-39
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• 2022

Sustained economic development around the world is accelerating resource depletion. Research and development of secondary batteries that can replace them is also being actively conducted. Secondary batteries are emerging as a key technology for carbon neutrality. The core of an electric vehicle is the battery (secondary battery). Therefore, in this study, the temperature change by the heat source of the hammer and the rotational speed (rpm) of the abrasive disc of the Classifier Separator Mill (CSM) was repeatedly calculated and analyzed using the heat flow simulation STAR-CCM+. As the rotational speed (rpm) of the abrasive disk increases, the convergence condition of the iteration increases. Under the condition that the inlet speed of the Classifier Separator Mill (CSM) and the heat source value of the disc hammer are the same, the disc rotation speed (rpm) and the hammer temperature are inversely proportional. As the rotational speed (rpm) of the disc increases, the hammer temperature decreases. However, since the wear rate of the secondary battery material increases due to the strong impact of the crushing rotational force, it is determined that an appropriate rpm setting is necessary. In CSM (Classifier Separator Mill), it is judged that the flow rate difference is not significantly different in the direction of the pressure outlet (Outlet 1) right above the classifier wheel with the fastest flow rate. Because the disc and hammer attachment technology is adhesive, the attachment point may deform when the temperature of the hammer rises. Therefore, it is considered necessary to develop high-performance adhesives and other adhesive technologies.

• Journal of The Korean Association For Science Education
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• v.29 no.5
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• pp.580-591
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• 2009

The purpose of this study is to get implications on teacher education curriculum according by analyzing pre-service secondary teachers' difficulties during student-teacher practice. Fifty-six pre-service secondary teachers were requested to write anecdotes about their student-teacher practice. Pre-service secondary teachers revealed that they had experienced the most difficulties relating to instruction teaching. They answered that they had especially comprehended inducing interest in diffcult learners, attention, appropriate composition of questions, and learners' understanding levels. Pre-service secondary teachers showed that they had tried to control students in experiment instruction. Also, they demonstrated that time for guidance counseling had been insufficient. They were dissatisfied with the content and level of counseling. Therefore, we need to improve teachers' college curriculum by performing student-teacher practice and feedback. We especially need to systematize teachers' college curriculum on the basis of developing standards of science teachers' expertise.

• 한국전기화학회:학술대회논문집
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• 2003.10a
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• pp.17-17
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• 2003

• Proceedings of the Korean Nuclear Society Conference
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• 2004.05a
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• pp.458-458
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• 2004

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.5
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• pp.31-36
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• 2010

SAI(Secondary Air Injection) system has been studied widely as one of the promising countermeasure for reducing HC emission at cold start. In this paper, in order to find out the optimal position of SAI, computational thermal fluid analysis on exhaust system adapted SAI system is performed using commercial 3-D CFD code, CFX. The present results showed that SAI position strongly affected the uniformity of air distribution in front of catalyst. And also through the decision process of optimal position of SAI, new index, uniformity of air distribution($U_{\phi}$) is proposed to define it quantitively. Because $U_{\phi}$ is very simple equation and similar with flow uniformity, it is very easy to figure out the physical meaning and to apply it to practices. Finally, we applied the index $U_{\phi}$ to the decision process of the optimal position of SAI, so that we could get the clear comparison results.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.225-233
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• 2001

Distortion of Secondary Ion Mass Spectrometry(SIMS) depth profile, which is usually observed when the analysis is made using oxygen flooding on the surface of Si with oxide on it, has been corrected. The origin of distortion has been attributed to depth calibration error due to sputter rate difference and concentration calibration error due to relative sensitivity factor(RSF) difference between $SiO_2$ and Si layers, In order to correct depth calibration error, artifact in analysis of sodium ion on oxide was used to define the interface in SIMS depth profile and oxide thickness was measured with SEM and XPS. The differences of sputter rate and RSF between two layers have been attributed to volume swelling of Si substrate occurred by oxygen flooding induced oxidation. The corrected SIMS depth profiles showed almost the same results with those obtained without oxygen flooding.

• Journal of Educational Research in Mathematics
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• v.21 no.1
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• pp.57-65
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• 2011

The conceptions of definition and proof radically change in the transition from secondary to tertiary mathematics. Specifically this paper analyses the historical development of the axiomatic method from Greek to modern mathematics. To understand Greek and modern axiomatic method, it is important to know the different characteristics of the primitive terms, constant and variable. Especially this matter of primitive terms explains the change of conceptions of definition, proof and mathematics. This historical analysis is useful for introducing the meaning of formal definition and proof.

• MALSORI
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• no.44
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• pp.1-14
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• 2002

Because the accuracy and the fluency are the essence in English speaking, both of them are very important in English trencher training and in-service English training programs. To get the accuracy and the fluency, the causes and the phenomena of the unnatural pronunciation have to be diagnosed. Consequently, the problematic and unnatural pronunciation of Korean elementary and secondary English teachers should be analyzed with using Acoustic Analyzing tools like CSL, Multi-speech and Praat. In addition, an attempt to Pinpoint what the causes of unnatural pronunciation was executed. Next a procedure and steps were proposed for in-service training programs that would cultivate the fluency and the accuracy. In case of elementary teachers, the unnatural pronunciation of segmental features and suprasegmental features were found much. therefore segmental features should be emphasized in the begging of pronunciation training courses and then suprasegmental features have to be emphasized. In case of secondary teachers, the unnatural pronunciation of suprasegmental features were found much. Therefore segmental and suprasegmental features have to be focused at the same time. In other words, features in word level should be focused first for elementary English teacher, and features in word level and beyond word level should be trained at the same time for secondary English teachers.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.26-32
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• 2016

In previous studies on LPG siting in Korea, the scope have not included the probability of the secondary events of adjacent LPG tanks or structures from an explosion source. Therefore, it is essential to first identify the phenomenon which can be caused by BLEVE and then, properly assess their effects to each target including secondary event. In this study, we calculated the effects from a potential BLEVE of 15 ton LPG tank causing damages of storage tanks (LPG), structures and human using Phast ver. 6.7 and then suggested three risk zones (Zone I, II, III) assuming the consequences such as overpressure, heat radiation and missile effect by fragments. Zone I and II are divided at the line of 50% occurrence of the secondary event. Zone II and III are divided by Individual Risk(IR). The zone approach in this study can be used for more effective and safer Land Use Planning (LUP) for the future.