• Composites Research
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• v.19 no.2
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• pp.1-6
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• 2006

The civilian and military agencies require the use of statistic-based allowable to design aerospace vehicles with composite materials. In order to comply this regulation, it is necessary to establish relatively large amount of database, which increases test costs and time. Recently NASA/FAA developed the new method which can satisfy the regulation with smaller test matrix through AGATE(Advanced General Aviation Transport Experiments) program. Especially the concept of material equivalency is very useful when the material has been certified in previous program, and it allows the engineer to use the database with the addition of small test matrix. This paper summarizes the material equivalency and acceptance test methodology so that composite material database can be shared and improve the credibility of the material quality. As a demonstration, the material design allowable of the high temperature carbon/epoxy composite developed domestically was determined with this methodology.

• Journal of Korean Association for Spatial Structures
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• v.14 no.3
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• pp.93-100
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• 2014

Ethylene Tetrafluoroethylene (ETFE) has been widely used in long-span buildings because of its light weight and high transparency. This paper studies the short and long term creep behaviour of ETFE foil. A series of short-term creep and recovery tests were performed, in which the residual strain was observed. A long-term creep test of the ETFE foil was also performed over 110 days. A viscoelastic-plastic model was then established to describe the short-term creep and recovery behaviour. The model contains a traditional multi-Kelvin part and an added steady-flow component to represent the viscoelastic and viscoplastic behaviour, respectively. The model successfully fit the data for three stresses and six temperatures. Additionally, time-temperature equivalency was adopted to predict the long-term creep behaviour of ETFE foil. Horizontal shifting factors were determined from the process of shifting creep-curves at six temperatures. The long-term creep behaviours at three temperatures were predicted. Finally, the long-term creep test showed that the short-term creep test at identical temperatures insufficiently predicted additional creep behaviour, and the long-term test verified the horizontal shifting factors derived from the time-temperature equivalency.

• Journal of the Korean Geosynthetics Society
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• v.5 no.4
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• pp.49-58
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• 2006

Recently, geosynthetic clay liners (GCLs) have increasingly been used to replace compacted clay liners (CCLs) in composite liner systems. Since the introduction of GCLs to waste containment facilities, one of the major concerns about their use has been the hydraulic equivalency to CCLs as required by regulations. Laboratory test results and more recently field observations show that the thickness, or mass per unit area, of hydrated bentonite in a GCL can decrease under normal stress, especially around zones of stress concentration or nonuniform stresses, such as a rock or roughness in the subgrade, a leachate sump, or wrinkles in an overlying geomembrane. This paper presents field case histories that confirm the laboratory observations of bentonite migration and the effect of bentonite migration on hydraulic equivalency and contaminant transport through a GCL.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.103-110
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• 2016

This study shows the statistical properties of the domestic composite material prepregs test result. During the last three years(2012.5~2015.6) the prepreg specimen tests have been performed by referring to NCAMP developed test procedure which was approved by FAA. The database of (1) Carbon Tape, (2) Glass Fabric, and (3) Carbon Fabric composite material prepregs' characteristics have been established for certified aircraft structures. This qualified materials can be used for aircraft structural design through proper material equivalency procedures.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.5
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• pp.571-575
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• 2010

Mutation testing is known as a very useful technique for measuring the effectiveness of a test data set and finding weak points of the test set. An equivalent mutant degrades the effectiveness of mutation testing. Elimination of equivalent mutants is a very important problem in mutation testing.In this paper, we proposed kinds of methods for detecting class-level equivalent mutants. These methods judge the equivalency of mutants through structural informations and behavioral information of the original program and mutants using static analysis. We found that our approach can detect not a few of equivalent mutants and expected that the cost of mutation testing can be saved considerably.

• Structural Engineering and Mechanics
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• v.21 no.6
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• pp.737-765
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• 2005

This paper presents a theoretical model for the behavior of partially confined axi-symmetric reinforced concrete members subjected to axial load. The analysis uses the theories of elasticity and plasticity to cover the full range of the concrete behavior. Analysis of the elastic range of the problem involves boundary conditions that are defined along a relatively simple geometry. However, extending the analysis into the plastic range involves difficulties that arise from the irregular geometry of the boundary between the plastic zone and the elastic zone, a boundary which is also changing as the axial load increases. The solution is derived by replacing the discrete steel ties with an equivalent tube of thickness $t_{eq}$ and by analyzing the concrete cylinder, which is uniformly confined by the equivalent tube. The equivalency criterion initiates from a theoretical analysis of the problem in its elastic range where further finite element analysis shows that this criterion is valid also for the plastic range of the cylinder material. According to the proposed model, the efficiency of the lateral reinforcement can be evaluated by the equivalent thickness $t_{eq}$. Comparison with published test results of confined reinforced concrete stress-strain curves shows good agreement between the test and the analytical results.

• Journal of Oral Medicine and Pain
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• v.43 no.2
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• pp.34-40
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• 2018

Purpose: The aim of this study was to translate the original English version of tampa scale for kinesiophobia for temporomandibular disorders (TSK-TMDs) for cultural equivalency into Korean language and to evaluate the reliability of the Korean version of the TSK-TMD among symptom free subjects. Methods: The original version of TSK-TMD was translated and cross-culturally adapted following international guidelines. A total 90 subjects (50 women, 40 men) were participated to fill out the questionnaire. The internal consistency and test-retest reliability with a one- or two-week time interval were evaluated. Results: The internal consistency of TSK-TMD of the original and the modified 12-item TSK-TMD were 0.866, and 0.858, respectively using the Cronbach's alpha coefficient. And the internal consistency of activity avoidance (AA) and somatic focus (SF) subscale were 0.838 and 0.807 assessed with Cronbach's alpha indicating excellent reliability. Test-retest reliability of the original TSK-TMD measured by the intra-class correlation coefficient (ICC) was 0.764, and coefficients value of the 12-question TSK-TMD was 0.752. Test-retest reliability of AA subscale was 0.722 and SF subscale was 0.677 measured by ICC. Conclusions: The Korean version of the TSK-TMD questionnaire was found to be a reliable instrument and successfully translated to Korean language. There are no significant differences between overall and modified version of TSK-TMD. It can be used as a valuable instrument for the analyses of the psychosocial aspects of the TMD patients in Korea.

• Journal of Korean Academy of Nursing
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• v.38 no.2
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• pp.344-352
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• 2008

Purpose: This study was to test the reliability and validity of a Drinking Refusal Self-Efficacy Questionnaire-Revised (DRSEQ-R) in Korean college students, Methods: The DRSEQ-R was designed to assess an individual's belief in their ability to refuse drinking alcohol by Oei et al. (2005) and consisted of three factors (social pressure, opportunity, and emotional relief). A methodological study design with an exploratory factor analysis for validity and correlation coefficients for reliability was used. DRSEQ-R was translated into Korean and a translation equivalency was obtained. DRSEQ-R was tested with a sample of 201 college students in Korea. The subjects consisted of 106 males and 95 females. Principal component factor analysis was used for construct validity and Cronbach's alpha was used to evaluate for internal consistency of the instrument. Results: The factor analysis showed three factors explaining 66.3% of total variance and the corresponding factors were emotional relief (48.01%), drinking contextual opportunity (11.18%), and social pressure (7.14%). The internal consistency was acceptable (Cronbach's alpha=.937). All three factors of DRSEQ-R negatively correlated with alcohol dependency and a heavy drinker showed a lower DRSEQ-R than a moderate drinker. Conclusion: Based on the findings, DRSEQ-R is a reliable and valid instrument to measure for drinking refusal self-efficacy in Korean college students.

• Child Health Nursing Research
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• v.18 no.2
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• pp.53-59
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• 2012

Purpose: This study was done to verify the reliability and validity of the Korean version of DMCI in Korean adolescents. Methods: A methodological study design was used with Cronbach's ${\alpha}$ for reliability, and an exploratory factor analysis and contrasted groups approach for construct validity. DMCI was translated into Korean and tested with a sample of 406 adolescents in Korea. The data were analyzed using Cronbach's ${\alpha}$, item correlation with total, principal component factor analysis, and t-test. Results: The translated content of the DMCI was validated by nursing faculty members and translation equivalency was obtained. The Cronbach's ${\alpha}$ of the DMCI simplified with 18 items was .78. The factor analysis revealed three factors explaining 41.5% of total variance and the corresponding factors were self-observation (21.6%), self-judgement (11.4%), and self-confidence (8.6%). The mean score for the DMCI in the aggression group was significantly lower than the non-aggression group. Conclusion: Results of this study suggest that the Korean version of DMCI can used as a reliable and valid measure to assess decision making competency in Korean adolescents.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.35-41
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• 2022

UAM (Urban Air Mobility) is a new safe, secure, and more sustainable air transportation system for passengers and cargo in urban environments. Commercial operations of UAM are expected to start in 2025. Since production rates of UAM are expected to be closer to cars than conventional aircraft, the airworthiness methodology for UAM must be prepared for mass production. Composite materials are expected to be mainly used for UAM structures to reduce weight. In this paper, the composite material qualification method was derived and the materials were applied for small aircraft application. It is expected to reduce the airworthiness certification time by applying composite material qualification system and its database.