• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1511-1516
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• 2020

The Korea Research Institute of Standards and Science (KRISS) established a new standard of the absorbed dose to water in LINAC X-ray beams. To confirm the equivalence of the new standard with other national metrology institutes (NMIs), a bilateral comparison study of the absorbed dose to water in high energy X-ray beams was performed between the KRISS and the National Metrology Institute of Japan (NMIJ). The comparison was made in-directly. Three transfer chambers were calibrated in the high energy X-ray beams by both laboratories and the calibration coefficients were compared. The average ratios of the calibration coefficients of the three transfer chambers obtained by the KRISS to those obtained by the NMIJ were 1.004, 1.006, 1.006, 1.007 for 6, 10, 15 and 18 MV X-ray beams, respectively. The calibration coefficients obtained at the KRISS were higher than those at the NMIJ but they were in good agreement within the expanded uncertainty of 1.0% (k = 2). The results of this study will be used as the evidence for the KRISS standard being comparable with those of other NMIs, temporarily, in the interim period up to finalizing a key comparison study, BIPM.RI(I)-K6 managed by the Consultative Committee for Ionizing Radiation.

• The KSFM Journal of Fluid Machinery
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• v.19 no.5
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• pp.50-60
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• 2016

A design methodology of the modeled test facility to conserve an injection performance of a passive safety injection system is proposed. This safety injection system is composed of a core makeup tank and a safety injection tank. Individual tanks are connected with pressure balance line on the top side and injection line on the bottom side. It is important to conserve the scaled initial injection flow rate and total injection time since this system can be operated by small gravity head without any active pumps. Differential pressure distribution of the injection line induced by the gravity head is determined by the vertical length and elevation of each tank. However, the total injection time is adjustable by the flow resistance coefficient of the injection line. The scaling methodology for the tank and flow resistance coefficient is suggested. A key point of this test facility design is a scaling analysis for the flow resistance coefficient. The scaling analysis proposed on this paper is based on the volume scaling law with the same vertical length to the prototype and can be extended to a model with a reduced vertical length. A set of passive injection test were performed for the tanks with the same volume and the different length. The test results on the initial flow rate and total injection time showed the almost same injection characteristics and they were in good agreement with the design values.

• Strategy21
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• s.43
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• pp.175-199
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• 2018

Recent marine territorial disputes in the East China Sea and the South China Sea have come to us as a great threat. China, which has recently established the China Coast Guard and has rapidly developed maritime security forces, is trying to overcome the various conflict countries with its power. Japan is also strengthening intensively its maritime security forces. Since Korea, China, and Japan are geographically neighboring and sharing maritime space in Northeast Asia, there is no conflict between maritime jurisdiction and territorial rights among the countries. The struggle for initiative in the ocean is fierce among the three coastal nations in Northeast Asia. therefore, Korea needs more thorough preparation and response to protect the marine sovereignty. As the superpowers of China and Japan are confronted and the United States is involved in the balance of power in strategic purposes, the East Asian sea area is a place where tension and conflict environment exist. China's illegal fishing boats are constantly invading our waters, and they even threaten the lives of our police officers. The issue of delimiting maritime boundaries between Korea and China has yet to be solved, and is underway in both countries, and there is a possibility that the exploration activities of the continental shelf resources may collide as the agreement on the continental shelf will expire between Korea and Japan. On the other hand, conflicts in the maritime jurisdictions of the three countries in Korea, China and Japan are leading to the enhancement of maritime security forces to secure deterrence rather than military confrontation. In the situation where the unresolved sovereignty and jurisdiction conflicts of Korea, China and Japan continue, and the competition for the strengthening of the maritime powers of China and Japan becomes fierce, there is a urgent need for stabilization and enhancement of the maritime forces in our country. It is necessary to establish a new long-term strategy for enhancing the maritime security force and to carry out it. It is expected that the Korean Coast Guard, which once said that it was a model for the establishment of China's Coast Guard as a powerful force for the enforcement of the maritime law, firmly establishes itself as a key force to protect our oceans with the Navy and keeps our maritime sovereignty firmly.

• Journal of The Korean Astronomical Society
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• v.46 no.3
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• pp.133-140
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• 2013

The empirical mass discrepancy-acceleration (MDA) relation of disk galaxies provides a key test for models of galactic dynamics. In terms of modified laws of gravity and/or inertia, the MDA relation quantifies the transition from Newtonian to modified dynamics at low centripetal accelerations $a_c{\lesssim}10^{-10}ms^{-2}$. As yet, neither dynamical models based on dark matter nor proposed modifications of the laws of gravity/inertia have predicted the functional form of the MDA relation. In this work, I revisit the MDA data and compare them to four different theoretical scaling laws. Three of these scaling laws are entirely empirical; the fourth one - the "simple ${\mu}$" function of Modified Newtonian Dynamics - derives from a toy model of gravity based on massive gravitons (the "graviton picture"). All theoretical MDA relations comprise one free parameter of the dimension of an acceleration, Milgrom's constant aM. I find that the "simple ${\mu}$" function provides a good fit to the data free of notable systematic residuals and provides the best fit among the four scaling laws tested. The best-fit value of Milgrom's constant is $a_M=(1.06{\pm}0.05){\times}10^{-10}ms^{-2}$. Given the successful prediction of the functional form of the MDA relation, plus an overall agreement with the observed kinematics of stellar systems spanning eight orders of magnitude in size and 14 orders of magnitude in mass, I conclude that the "graviton picture" is sufficient (albeit probably not a necessary nor unique approach) to describe galactic dynamics on all scales well beyond the scale of the solar system. This suggests that, at least on galactic scales, gravity behaves as if it was mediated by massive particles.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.269-274
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• 2011

A CFD analysis was performed to examine the inner channel blockage of dual-cooled fuel which has being developed for the power uprate of a pressurized water reactor (PWR). The dual-cooled fuel consists of an annular fuel pellet($UO_2$) and dual claddings as well as internal and external cooling channels. The dual-cooled annular fuel is different from a conventional solid 려el by employing an internal cooling channel for each fuel pellet as well as an external cooling channel. One of the key issues is the hypothetical event of inner channel blockage because the inner channel is an isolated flow channel without the coolant mixing between the neighboring flow channels. The inner channel blockage could cause the Departure from Nucleate Boiling (DNB) in the inner channel that eventually causes a fuel failure. This paper presents the CFD simulation of the flow through the side holes of the bottom end plug for the complete entrance blockage of the inner channel. Since the amount of coolant supply to the inner channel depends on largely the pressure loss at the side hole, the pressure loss coefficient of the side hole was estimated by the CFD analysis. The CFD prediction of the loss coefficient showed a reasonable agreement with an experimental data for the complete blockage of both the inner channel entrance and the outer channel. The CFD predictions also showed the decrease of the loss coefficient as the outer channel blockage increases.

• Steel and Composite Structures
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• v.26 no.1
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• pp.79-87
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• 2018

In order to study the natural vibration characteristics of steel-concrete composite truss beam (SCCTB), the influence of multiple factors such as interface slip, shear deformation and moment of inertia are considered. Afterwards, based on the Hamilton principle the vibration control differential equation and natural boundary conditions of SCCTB are deduced. By solving SCCTB differential equations of vibration control, an analytical calculation method is proposed for analyzing the natural vibration characteristics of SCCTB. The natural frequencies of SCCTBs with different degrees of shear connection and effective lengths are calculated by using the analytical method, and the results are compared against those obtained from ANSYS finite element numerical calculation method. The results show that the analytical method considering the influence factors such as interface slip, shear deformation and moment of inertia are in good agreement with those obtained from ANSYS finite element numerical calculation method. This evidences the correctness of the analytical method and show that the method proposed exhibits improvement over the previously developed theories for the natural vibration characteristics of SCCTB. Finally, based on the analytical method, the influence factors of SCCTB natural vibration characteristics are analyzed. The results indicate that the influence of interface slip stiffness on SCCTB's natural frequency is more than 10% and therefore cannot be neglected. Moreover, shear deformation has an effect of more than 35% on SCCTB's natural frequency and the effect cannot be ignored either in this case too.

• Steel and Composite Structures
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• v.26 no.6
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• pp.793-808
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• 2018

In this study, the seismic performance of the connections between L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) and H-beams used in high-rise steel frame structures was investigated. Seven full-scale specimens were tested under quasi-static cyclic loading. The variables studied in the tests included the joint type, the axial compression ratio, the presence of concrete, the width-to-thickness ratio and the internal extension length of the side plates. The hysteretic response, strength degradation, stiffness degradation, ductility, plastic rotation capacity, energy dissipation capacity and the strain distribution were evaluated at different load cycles. The test results indicated that both the corner and exterior joint specimens failed due to local buckling and crack within the beam flange adjacent to the end of the side plates. However, the failure modes of the interior joint specimens primarily included local buckling and crack at the end plates and curved corners of the beam flange. A design method was proposed for the flexural capacity of the end plate connection in the interior joint. Good agreement was observed between the theoretical and test results of both the yield and ultimate flexural capacity of the end plate connection.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.588-596
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• 2017

Although many policy makers and scholars argue that foreign direct investment is crucial to the economic growth of developing countries, there is no universal agreement on the positive relationship between foreign direct investment inflows and economic growth. Using a cross-country analysis based on data from 88 countries for the years 1990-2015, this paper empirically explores the impact of FDI on economic growth. To this end, several versions of the neoclassical growth models, explicitly including FDI, are estimated. Subject to the appropriate caveats, the results provide further support for several key conclusions of former studies, including the inference that investment in physical capital, population growth, and human capital are important in accounting for economic growth across countries. The results show that FDI significantly contributes to economic growth in developing countries.

• Journal of Korean Academy of Nursing
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• v.37 no.3
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• pp.381-390
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• 2007

Purpose: The purpose of this study was to understand the experiences of mental health hospital workers. Methods: Participants in the study were a total of 8 mental health hospital workers who consisted of nurses, social welfare workers and health managers. To prevent them from being omitted, the interviews were all recorded under the participants prior agreement. The method was analysis using the phenomenological method proposed by Colaizzi(1978). Results: The experiences of the participants of this study were classified into 15 significant areas, from which 10 subjects hard work, conflicts, heavy feeling, irritability, getting familiar, changes of recognition, aptitude determination, feeling of achievement and sense of pride were drawn out. These subjects were then grouped into 5 themes. These five themes were finally grouped into 5 categories, negative emotion, depressive emotion, changes of thinking, delight and value discovery. Conclusions: The study tried to analyze the experiences of key informants like nurses, social welfare workers and health managers all of whom were serving at mental health hospitals, contribute to social recognition about the special medical establishment, promote qualitative mental health nursing and further provide educational information necessary for understanding mental health hospital workers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3C
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• pp.426-435
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• 2004

The DIAMETER protocol provides Authentication, Authorization, and Accounting (AAA) transactions across the Internet. SIP(Session Initiation Protocol) will be used for new types of signaling, such as instant messaging and application level mobility across networks. And SIP will be a major signaling protocol for next generation wireless networks. But the Digest authentication scheme is not using a secure method of user authentication in SIP, and it is vulnerable to man-in-the-middle attacks or dictionary attacks. This study focused on designing a SIP proxy for interworking with AAA server with respect to user authentication and security analysis. We compared and analyzed the security aspects of the scenarios and propose two proposals that a response which include the user address and password-based mutual authentication and key agreement protocol. It is claimed to be more secure against common attacks than current scenarios.