• Smart Structures and Systems
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• v.30 no.1
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• pp.17-34
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• 2022

For steel structures, fatigue cracks are critical damage induced by long-term cycle loading and distortion effects. Vision-based crack detection can be a solution to ensure structural integrity and performance by continuous monitoring and non-destructive assessment. A critical issue is to distinguish cracks from other features in captured images which possibly consist of complex backgrounds such as handwritings and marks, which were made to record crack patterns and lengths during periodic visual inspections. This study presents a parametric study on image-based crack identification for orthotropic steel bridge decks using captured images with complicated backgrounds. Firstly, a framework for vision-based crack segmentation using the atrous convolution-based Deeplapv3+ network (ACDN) is designed. Secondly, features on crack images are labeled to build three databanks by consideration of objects in the backgrounds. Thirdly, evaluation metrics computed from the trained ACDN models are utilized to evaluate the effects of obstacles on crack detection results. Finally, various training parameters, including image sizes, hyper-parameters, and the number of training images, are optimized for the ACDN model of crack detection. The result demonstrated that fatigue cracks could be identified by the trained ACDN models, and the accuracy of the crack-detection result was improved by optimizing the training parameters. It enables the applicability of the vision-based technique for early detecting tiny fatigue cracks in steel structures.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.52-57
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• 2018

This paper presents the design and cold flow test results of oxidizer-rich preburner injectors for a 9 tonf-class staged combustion engine cycle. Three types of coaxial swirl injectors were designed, and 12 injectors were designed for each type. The diameters of the fuel tangential holes are identical. The diameters of the oxidizer tangential holes were varied to investigate the influence of combustion in the oxidizer-rich preburner according to the momentum ratio of the gas oxidizer generated from combustion in the injector chamber and liquid oxidizer through the cooling channel. It will be verified through a powerpack and combustion test using an oxidizer-rich preburner. In the cold flow test, the fuel flow rate and oxidizer tangential hole flow rate reached the target value based on the designed differential pressure.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.107-113
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• 2008

As it recently appears that LCC (Life Cycle Cost) analysis may be considered as an essential method for economic evaluation of infrastructures. Many researches have been made to assess LCC of each facility based on reasonable methods. However, expected maintenance repair cost must be reasonably estimated to enhance the reliability of LCC analysis through systematic and rational methods. This study is intended to propose a rational approach to reliability-based LCC analysis of high-speed railway steel bridges considering lifetime corrosion and fatigue damage. However in Korea, since high speed railway steel bridges are only recently constructed, no direct statistical data are available for the account of the maintenance cost and thus their maintenance characteristics are not clear yet. In this paper, for the assessment of expected maintenance/repair cost, the fatigue system reliability analysis incorporating the corrosion effect is proposed by considering the corrosion and fatigue damage using measured data of high speed railway steel bridges. A model proposed by Rahgozar, of at for fatigue notch factor considering the corrosion effect is used in order to incorporate the corrosion effect into the fatigue strength reduction and S-N curve. Finally, the effectiveness of LCC model proposed for high-speed railway steel bridges is demonstrated by a numerical example.

• The Journal of Korea Robotics Society
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• v.17 no.3
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• pp.296-302
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• 2022

This paper proposes a center of plantar foot pressure (CoP) trajectory estimation method based on Gaussian process regression, with the aim to show robust results regardless of the regions and numbers of FSRs of the insole sensor. This method can bring an interpolation between the measurement points inside the wearable insole sensor, and two experiments are conducted for performance evaluation. For this purpose, the input data used in the experiment are generated in three types (13 FSRs, 8 FSRs, 5 FSRs) according to the regions and numbers of FSRs. First, the estimation results of the CoP trajectory are compared using Gaussian process regression and weighted mean. As a result of each method, the estimation results of the two methods were similar in the case of 13 FSRs data. On the other hand, in the case of the 8 and 5 FSRs data, the weighted mean varies depending on the regions and numbers of FSRs, but the estimation results of Gaussian process regression showed similar results in spite of reducing the regions and numbers. Second, the estimation results of the CoP trajectory based on Gaussian process regression during several gait cycles are analyzed. In five gait cycles, the previous cycle and the current estimation results are compared, and it was confirmed that similar trajectories appeared in all. In this way, the method of estimating the CoP trajectory based on Gaussian process regression showed robust results, and stability was confirmed by yielding similar results in several gait cycles.

• Journal of Korean Home Economics Education Association
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• v.31 no.3
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• pp.23-39
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• 2019

The purpose of the study was to analyze the home economics education experts' and teachers' perception of ways to align instruction with evaluation, based on the 2015 revised technology and home economics curriculum for the purpose of developing the independent living competencies, and to provide examples of alignment in practice. The analysis is based on the data from a Delphi study (10 experts) and a survey of technology and home economics teachers(n=422). The results of survey indicated that experts and teachers perceived the instruction-assessment alignment to be most appropriate for project learning-project assessment, followed by project learning-portfolio assessment, problem solving learning-portfolio assessment, and problem solving learning-project assessment, in order. Based on the survey results, a model of instruction-assessment alignment and a teaching-learing plan were presented, based on 'Development task of life cycle and Life plan' unit. This was considered to be a proper method of instructional alignment for the purpose of developing 'independent living competence' with project-learning/project-assessment. The model focuses on consistency between instruction and evaluation, unity in methods, and the availablility of feedbacks of assessment for the improvement of independent living competencies. In conclusion, this study contributes as foundational information for teaching and learning-assessment alignment. Diverse methods of instruction-evaluation alignment is expected for future research.

• Journal of Korean Society of Forest Science
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• v.100 no.4
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• pp.672-680
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• 2011

The purpose of this study has been carried to develop a criterion for the selection of evaluation factors on Forest Carbon Cycle Community(F.C.C.C) based on the result of survey of 96 participants who were operation managers on mountain eco village(31), relevant experts(33), and officers of local government(32). For analysis of the results of survey, DHP(Delphi Hierarchy Process) method was used which is a combination of Delphi method and AHP(Analytic Hierarchy Process) method. The key factors on selection of a suitable area to launch F.C.C.C. project of Korea Forest Service was selected under three hierarchical classes. Class 1 comprises 3 indices(Physical resource index, Human resource index, Vision index), and Class 2 which contains 10 indices (Existing resource, Surroundings resource, Forest biomass resource, Humanities Social quality, Local resident participation, Leader's ability, External support, Planning of operation, Capability of operation, and Effect of operation). Class 3 is sub-level class of class which possess 38 indices. From the results of analysis, Consistency Index(C.I) of each index in the 3 classes was used as evaluation factor. In Class 1, index 'human resources' showed highest Consistency Index(0.454). In Class 2, index 'forest biomass resources' was the highest Consistency Index(0.376) in 'physical resources' of Class 1, index 'leader's ability' was the highest Consistency Index(0.326) in 'human resources' of Class 1, and index 'planning of operation' was the highest Consistency Index(0.346) in 'vision' of Class 1. In Class 3, relative importance of 38 index including 'Joint ownership land security(C.I.-0.266)' was evaluated. Based on the result of this study, a criterion for the selection of evaluation factors for F.C.C.C was developed and the evaluation criterion is expected to be use to select of a suitable area to launch F.C.C.C. project since 2011.

• Women's Health Nursing
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• v.22 no.2
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• pp.104-115
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• 2016

Purpose: The purpose of this study was to develop a web-based sexual health program for women undergoing treatment for gynecologic cancer and their partners, and to evaluate the validity of the developed program. Methods: A web-based sexual health program was developed and evaluated: analysis (needs assessment on 23 patients and content analysis through literature review and web search), design, development, implementation, and evaluation. Results: The web-based sexual health program for women undergoing treatment for gynecologic cancer and their partners was structured with sexual life, sexual response cycle, change of sexual function, sexual dysfunction related to treatment, and useful method for sexual dysfunction. This program included a video to improve for understanding and a bulletin board to promote bi-directional interactions between program users and providers. Experts and users rated this program in terms of efficacy, convenience, design, relevance, and usefulness. This program contents were found appropriate and satisfactory to both experts and users. Conclusion: This web-based sexual health program for women undergoing treatment for gynecologic cancer and their partners would contribute to sexual health promotion for gynecologic cancer women and their partners.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.198-204
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• 2013

Acoustic emission(AE) signal was detected during charge and discharge of lithium ion battery to investigate relationships among cumulative count, discharge capacity, and microdamages. AE signal was received during accelerated charge/discharge cycle test of a coin-type commercial battery. A number of AE signals were successfully detected during charge and discharge, respectively. With increasing number of cycle, discharge capacity was decreased and AE cumulative count was observed to increase. Microstructural observation of the decomposed battery after cycle test revealed mechanical damages such as interface delamination and microcracking of the electrodes. These damages were attributed to sources of the detected AE signals. Based on a linear correlation between discharge capacity and cumulative count, feasibility of AE technique for evaluation of battery degradation was suggested.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.3
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• pp.220-226
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• 2019

Magnesium hydride has a high hydrogen storage capacity (7.6 wt.%), and is cheap and lightweight, thus advantageous as a hydrogen storage alloy. However, Mg-based hydrides undergo hydrogenation/dehydrogenation at high temperature and pressure due to their thermodynamic stability and high oxidation reactivity. MWCNTs exhibit prominent catalytic effect on the hydrogen storage properties of $MgH_2$, weakening the interaction between Mg and H atoms and reducing the activation energy for nucleation of the metal phase by co-milling Mg with carbon nanotubes. Therefore, it is suggested that combining transition metals with carbon nanotubes as mixed dopants has a significant catalytic effect on the hydrogen storage properties of $MgH_2$. In this study, Material life cycle evaluation was performed to analyze the environmental impact characteristics of Mg-CaO-10 wt.% MWCNTs composites manufacturing process. The software of material life cycle assessment (MLCA) was Gabi 6. Through this, environmental impact assessment was performed for each process.

• Journal of Animal Environmental Science
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• v.17 no.sup
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• pp.61-68
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• 2011

To assess the total cost with all stages of facilities, the feasibility of Life Cycle Cost (LCC) analysis was examined in this study to estimate the livestock manure treatment system and optimal decision making process. For the economic evaluation, the plant/equipment investment and annual operation cost of four Public Livestock Recycling Facilities, whose treatment capacity is 100 ton piggery manure per day, was compared. The initial cost was in the range of 2,699 million won to 3,202 million won, where T and E methods were highest and lowest, respectively. The annual operation cost was in the level of 378 million to 498 million won, which decreased in the following order : T method > J method > E method > B method. For the LCC analysis, 4.7% of interest rate, 3.13% of inflation rate, and 1.52% of net discount rate was considered by the data received from Bank of Korea and Statics Korea in the period of 2000 to 2009. Also, for the calculation of present value factor, the durable years of civil engineering & construction, machinery and electric instrument was 30 years, 10 years and 15 years, respectively. Based on these consideration, operation cost was in the range of 17,570 won/ton to 20,661 won/ton, and E method (17,570 won/ton) was economical and B method (20,661 won/ton) was non-economical. Though initial cost of T method was higher than that of B method, LCC analysis of T method was lower than that of T method due to the lower operation cost. Therefore, LCC analysis, which considers both initial cost and operation cost, is more reasonable evaluation method than either initial cost or annual operation cost. For the change of LCC analysis according to the uncertainty, the sensitivity analysis was carried out using fluctuation magnitude of discount rate in the period of 2000 to 2009. As a result, LCC analysis evaluated by discount rate was stable for the uncertain factors since the cost leadership did not change even though the sensitivity analysis varied. In summary, the economic evaluation using LCC analysis could be an efficient reference to choose the suitable livestock manure treatment plants. Furthermore, standardization of statement calculation for the actual cost analysis should be conducted and more detailed study is necessary to validate this summary. Therefore, the application of comprehensive technology evaluation, which considers LCC analysis, should contribute in obtaining objectivity and enhancing reliability for the 'Evaluation of Livestock Manure Treatment System and its Technology'.