• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.146-151
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• 2003

Reduced Activation Ferritic/Martenstic (RAFs) are leading candidates for structural materials of D-T fusion reactor. One of The RAFs, JLF-1 (9Cr-2W-V, Ta) has been developed and proved to have good resistance against high-fluency neutrino irradiation and good phase stability. Recently, in order to clarify the strengthening mechanical at high temperature, a new scheme to improve high temperature mechanical properties is desired. Therefore, the creep properties and creep life prediction by Larson-Miller Parameter method for JLF-1 to be used for fusion reactor materials or other high temperature components were presented at the elevated temperatures of $500^{\circ}C$, $550^{\circ}C$, $600^{\circ}C$, $650^{\circ}C$ and $704^{\circ}C$. It was confirmed experimentally and quantitatively that a creep life predictive e벼ation at such various high temperatures was well derived by LMP.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.58-63
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• 2004

Reduced Activation Ferritic/Martensitic Steels (RAFs) are leading candidntes for structural materials of a D-T fusion reactor. One of the RAFs, JLF-l (9Cr-2W-V, Ta) has been developed and has shown to have good resistance against high-fluency neutrino irradiation and good phase stability. Recently, in order to clarify the strengthening mechanisms at high temperatures, a new scheme to improve high temperature mechanical properties is desired. Therefore, the test technique development of high temperature creep behaviors for this material is very important. In this paper, the creep properties and creep life prediction, using the Larson-Miler parameter method for JLF-l to be used for fusion reactor materials or other high temperature components, are presented at the elevated temperatures of 50$0^{\circ}C$, 55$0^{\circ}C$, $600^{\circ}C$, $650^{\circ}C$ and 704$^{\circ}C$. It was confirmed, experimentally and quantitatively, that a creep life predictive equation, at such various high temperatures, is well derived mr the LMP method.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.13-18
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• 2004

The objective of this study is to investigate fracture toughness and fatigue crack propagation behavior in the Reduced Activation Ferritic Steel (RAFs) JLF-I. The fracture toughness tests were performed with various size(plane size and thickness) and various side groove of specimens. The fatigue crack propagation behavior of the JLF-I steel was investigated by the constant-amplitude loading test for the stress ratios R=O.I, 0.3 and 0.5 respectively. The effects of stress ratios and specimen size on the fatigue crack growth behaviors for JLF-I steel were discussed within the Paris law. The test results showed the standard CT specimen with the side groove of 40 % represented a valid fracture toughness. The fracture resistance curve increased with increasing plane size and decreased with increasing thickness. However, the fracture resistance curve of half size specimen was similar to that of the standard specimen. The fatigue crack propagation rate of a half size specimen was similar to that of a full size specimen at the stress ratios of 0.1, 0.3 and 0.5 respectively. The fatigue crack propagation behavior of this material were evaluated by using a half size specimen.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.319-319
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• 2023

Flows of water in the environment (e.g. in a river or estuary) generally occur in complex conditions. This complexity can hinder a general understanding of flows and their related sedimentary processes, such as erosion and deposition. To gain insight in simplified, controlled conditions, hydraulic flumes are a popular type of laboratory research equipment. Linear flumes use pumps to recirculation water. This isn't appropriate for the investigation of cohesive sediments as pumps can break fragile cohesive sediment flocs. To overcome this limitation, the rotating annular flume (RAF) was developed. While not having pumps, a side-effect is that unwanted secondary circulations can occur. To counteract this, the top and bottom lid rotate in opposite directions. Furthermore, a larger flume is considered better as it has less curvature and secondary circulation. While only a few RAFs exist, they are important for theoretical research which often underlies numerical models. Many of the first-generation of RAFs have come into disrepair. As new measurement techniques and models become available, there is still a need to research cohesive sediment erosion and deposition in facilities such as a RAF. New RAFs also can have the advantage of being automatic instead of manually operated, thus improving data quality. To further advance our understanding of cohesive sediment erosion and deposition processes, a large, automatic RAF (1.72 m radius, 0.495 m channel depth, 0.275 m channel width) has been constructed at the Hydraulic Laboratory at Chungnam National University (CNU), Korea. The RAF has the ability to simulate both unidirectional (river) and bidirectional (tide) flows with supporting instrumentation for measuring turbulence, bed shear stress, suspended sediment concentraiton, floc size, bed level, and bed density. Here we present the current status and future prospect of the CNU RAF. In the future, calibration of the rotation rate with bed shear stress and experiments with unidirectional and bidirectional flow using cohesive kaolinite are expected. Preliminary results indicate that the CNU RAF is a valuable tool for fundamental cohesive sediment transport research.

• Nuclear Engineering and Technology
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• v.37 no.5
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• pp.423-432
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• 2005

Japanese activities on fusion structural materials R&D have been well organized under the coordination of university programs and JAERI/NIMS programs more than two decades. Where, two categories of structural materials have been studied, those are; reduced activation martensitic/ferritic steels (RAFs) as reference material and vanadium alloys and SiC/SiC composite materials as advanced materials. The R&D histories of these candidate materials and the present status in Japan are reviewed with the emphasis on materials behavior under radiation damage. The importance of IFMIF and technology development for blanket R&D including ITER-TBRG activity is emphasized and the current status of those activities in Japan is also presented.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.42-48
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• 2015

Reduced activation ferritic/martensitic steels are recognized as the primary candidate structural materials for fusion blanket systems. Welding is an inevitable for breeding blanket for pressure tightness and radioisotope confinement. Especially, TIG welding was chosen for sealing because it has the largest gap allowance compared to the other welding methods, and its properties are controllable by feed wire and welding conditions. In this study, the low cycle fatigue test using two-type gage such as extensometer and strain gage was applied to the TIG welded joint of F82H steel, for evaluating fatigue damage accumulation behavior of the HAZs. As the result, the over-tempered HAZ have shown a higher fatigue damage accumulation compared with other materials at all the testing conditions.

• Journal of Home Health Care Nursing
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• v.12 no.2
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• pp.1-15
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• 2005

Purpose: This study was conducted to assess the fall risk factors. Method: The subjects were 87 persons who were older than 65 years living at 28 nursing home in Seoul and Gyunggi province. Subjects were interviewed using RAFS II for intrinsic factor and the environmental factor were assessed using a structured questionnaire from Oct. to Dec. in 2004. The data were analyzed by SPSS(ver. 12.0) programs, using descriptive statistics, $x^2$-test, and t-test. Result: The 37.9% of the subjects experienced the fall, and its average number is $1.94\pm1.75$. The Women's experience of the fall was higher than that of the men, but it was no significant difference with gender. There was no significant difference with the age and duration of living. The mean of the intrinsic risk factor was 13.38 in total score 39 points marks on the RAFS II scales. The intrinsic risk factor score of the fallen group 15.71 was significantly higher than the non-fallen group 12.10. The variables of recent fall experience(t=4.72, p=0.000) and urinary dysfunction(t=2.64, p=0.010) was significantly higher than the non-fallen group. The highest variable of the intrinsic factor was the age and the variables of drug intake, balance, chronic disease, recent fall experience, urinary dysfunction were followed in order. The mean of the environmental risk factor was 0.24 points. No significant differences were shown in environmental risk factor between the fallen and the non-fallen groups. To the fallen group, the place of entrance was the highest risky environmental factor. To see in area dimension, the floor surfaces was the highest risky environmental factor and equipment and illumination factor was the following risky elements in order. In the total score of environmental risk factors based on the ares, the fallen group was 0.26 and the non-fallen group was 0.24, but there were no significant differences between the groups. Conclusion: This results suggested that visual protection strategy, set up the safety device in the place of entrance and inner stairway, bathroom and nonskid mat in the nursing home would be contribute to the prevention of the fall for the elderly.

• Research in Community and Public Health Nursing
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• v.12 no.3
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• pp.600-608
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• 2001

Accidents are the fourth-leading causal factor of death among the elderly, and fall is a major type of accident (53.17%). Many cases of falls in the elderly result in delayed discovery and loss of quality of life. As the number of the elderly grows, falls will be a more important health problem. Most previous research on falls investigated prevalence. mortality, and the related factors. There are many studies proving the effect of rhythmic movements. But few researches considered linking risk factors of fall with rhythmic movements. Purpose: We want to show the changes after performing rhythmic movement program, in risk factors of falls and mobility such as flexibility, balance, muscle power and persistency in the elderly, in order to provide basic information needed for the development of fall injury prevention program for the elderly. Method: The design of this study is quasi-experimental, the equivalent control group, pretest-posttest. The subjects consist of 124 people who lived in Do-Bong-Qu. Seoul, agreed to participate in this study, and were able to follow this rhythmic movement program. About 93 % of them are from 65 to 84 years (Mean${\pm}$sd: $73.7{\pm}5.7$): 64% are female. The rhythmic movement program was designed. and performed by two community health nurses working in the Do-Bong-Gu Public Health Center, regularly twice a week from May, 4 to December, 17. in 10 senior citizens' community centers. Risk factors of fall were measured with RAFS- II (Risk Assessment for Falls Scale II) by asking about each item: mobility was measured by observing their specific movements asked by investigators. Results: 1. After performing the program during 7 months, risk factors score of falls were decreased significantly (paired-t = 4.77. p<0.01). 2. After performing the program during 7 months, flexibility (paired-t = 2.26. p=0.03) and mobility were improved (paired-t = 4.98. p<0.01). but muscle power and persistency did not change (paired-t = 0.33. p=0.74). Overall, mobility affecting the occurrence of falls was improved significantly (paired-t = 5.15. p<0.01). Conclusions: A regular rhythmic movement program can be helpful in preventing falls in the elderly. Further. we can develop a fall injury prevention program using rhythmic movement.