• Smart Structures and Systems
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• v.29 no.6
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• Journal of Korean society of Dental Hygiene
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• v.19 no.5
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• pp.715-729
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• 2019

Objectives: This study aimed to validate the moderating effect of oral health on the relationship between perceived health status and health-related quality of life in the elderly and to use this information as primary data to suggest oral health policies for the aged society. Methods: This study included 3,707 subjects aged over 65 years who answered all the variables used in the study model and completed the health questionnaire and screening survey based on the sixth Korea National Health and Nutrition Examination Survey. Baron & Kenny's linear regression analysis using SPSS 22.0 and SPSS Macro Version 3.1 programs was performed to confirm the moderating effect of the number of remaining natural teeth, chewing difficulty, and cardiovascular disease on the relationship between perceived health status and healthrelated quality of life in the elderly. Results: The number of remaining natural teeth, chewing difficulties, and cardiovascular diseases affected the perceived health status of the elderly. As the number of remaining natural teeth increased, the effect of perceived health status on the quality of life in the elderly was buffered. The effect of perceived health status on the quality of life increased with chewing difficulties and the number of cardiovascular diseases. In particular, it was confirmed that chewing difficulties, rather than the number of cardiovascular diseases. had a greater effect on the quality of life in the elderly. Conclusions: Oral health policies and projects are required to ensure oral rehabilitation with dentures and implants and restore chewing function to improve the quality of life of the elderly in Korea.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1999.05a
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• pp.171-176
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• 1999

Nondestructive inspection and accompanying life analysis based on fracture mechanics were the major conventional methods for evaluating remaining life of critical high temperature components in power plants. By using these conventional methods, it has been difficult to perform in-service inspection for life prediction. Also, quantitative damage evaluation due to unexpected abrupt changes in operating temperature was almost impossible. Thus, many efforts have been made for evaluating remaining life during operation of the plants and predicting real-time life usage values based on the shape of structures, operating history, and material properties. In this study, a core software for on-line life monitoring system which carries out real-time life evaluation of a critical component in power boiler(high temperature steam headers) is developed. The software is capable of evaluating creep and fatigue life usage from the real-time stress data calculated by using temperature/stress transfer Green functions derived for the specific headers and by counting transient cycles. The major benefits of the developed software lie in determining future operating schedule, inspection interval, and replacement plan by monitoring real-time life usage based on prior operating history.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.21 no.1
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• pp.57-68
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• 2014

Purpose: Nurses' management of Nursing Home residents' remaining functional ability is phenomena emphasizing as the main practice focus in long term care and has specific meanings within the context of quality of life for fragile and disabled elderly people in nursing homes. This study was conducted to clarify and to conceptualize the phenomena of nurses' management of nursing home residents' remaining functional ability. Method: The Hybrid Model of concept development was applied to develop a concept of nurses' management of residents' remaining functional ability. Results: This concept of nurse' management emerged as a phenomenon having meanings in two different dimensions, deliberation and enactment for five types of residents: residents with declining function and dementia requiring nursing assistance, bed-ridden residents with moderate dementia, residents with advanced dementia and behavior problems, but good physical health, residents at the end of life stage, and bed-ridden residents with intact mental health. Conclusions: Results indicate that nurses' management of remaining functional ability of residents in nursing homes is a concept having types of needs that should be treated in specified ways. Interventions should have a positive impacts on practical applications in nursing homes and on enhancing residents' remaining function.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.637-640
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• 2002

The deterioration of RC deck slabs has been a serious problem and high portion of budget has been a spent for repair and strengthening of deck slab. The concrete deck slabs are subject to direct application of vehicle loading and accumulation of fatigue damage. Besides, various environmental causes. In this paper, an probabilistic study is carried out to predict exact load effects and structural capacity of deck slab during its service life, and estimate an appropriate remaining life of deck slab. To achieve this purpose the live load model is developed using by influence line including deterioration of deck slab, and deterioration model of bridge deck slab is developed. In addition, the fatigue life of reinforced concrete deck slabs considering corrosion of reinforcement are estimated based on experimental formula. This study will help rational decisions for the management and repair of reinforced concrete deck slabs.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.148-153
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• 2004

This paper represents that parts of a large generator operating in 1000 MW are affected by centrifugal forces due to high-speed rotation in 3600 rpm and 3D FEM Analyses are required to obtained the structural reliability of the generator. From these results, one would know the weakest locations and the stress distributions. The fatigue life is calculated in order to grasp the remaining life of generator. 2D and 3D analyses are performed to calculate stresses of the generator rotor and the retaining ring. From 2D results, we find the SCF at the slot and sub-slot of the rotor. 3D analysis is applied at the end part of generator rotor, which represents complex geometry, and rotor and retaining ring shrink thermally. With these results, designers of rotor and retaining ring can compare with the results of design code and verify the stress distributions of generator rotor and retaining ring, and then calculate the remaining life from the low-cycle fatigue data.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.69-80
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• 2000

This paper presents the prediction of remaining service life of the concrete due to steel corrosion caused by the following three cases; carbonation, using sea sand and using deicing salts. The assessment of initiation period was generalized considering the existing perdiction models in the literature, corrosion experiment and field assessment. To evaluate the prediction equation of rust growth, the corrosion accelerating experiments was performed. The polarization resistance was measured by potentiostat and the conversion coefficient of polarzation resistance to corrosion rate was determined by the measurement of real mass loss. Chloride content, carbonation, cover depth, relative humidity, water-cement ratio(W/C), and the use of deicing salts were taken into account and the resulting prediction equation of rust growth was proposed on the basis of these properties. The proposed equation is to predict the rust growth during any specified period of time and be effective in particular for predicting service life of concrete in the case of using sea sand.

• Journal of Korean society of Dental Hygiene
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• v.19 no.1
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• pp.55-64
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• 2019

Objectives: The purpose of this study was to compare the differences in oral health-related quality of life among elderly people aged over 65 years, in terms of physical, mental and oral health status and to analyze factors affecting their oral health-related quality of life. Methods: From May 9 to June 23, 2017, we randomly visited aged-care community centers in the metropolitan area, and recruited 222 elderly, aged 65 or older. First, each participant completed a questionnaire consisting of 4 general items: 1 systematic disease, and 3 subjective oral conditions. Afterwards, the researchers interviewed the participants to assess their mental status, using MMSE-DS and recorded the responses. Finally, an oral examination was performed to determine the number of remaining teeth. The average oral health-related quality of life according to each characteristic was analyzed by t-test and ANOVA. Hierarchical multiple regression analysis and Pearson's correlation coefficient analysis were used to analyze the correlations between factors and the factors affecting oral health-related quality of life. Results: The mean oral health-related quality of life was 4.15. Participants with 20 or more remaining teeth demonstrated better oral health-related quality of life than those with 19 or less teeth. Higher oral health-related quality of life was also found among elderly without gingival bleeding, self-reported halitosis and dry mouth. In addition, positive correlation with the number of remaining teeth and negative correlation with gingival bleeding, self-reported halitosis and dry mouth, were noted. Finally, the results of the hierarchical multiple regression analysis indicated that remaining teeth, gingival bleeding, self-reported halitosis and education were influential factors in determining the oral health-related quality of life among the elderly. Conclusions: The results of this study confirmed the necessity of better policy support, and the importance of implementing delivered, elderly-centered oral health education program by professionals to prevent tooth loss and manage periodontal diseases.

• Nuclear Engineering and Technology
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• v.52 no.9
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• pp.1998-2008
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• 2020

Solenoid operated valves (SOV) play important roles in industrial process to control the flow of fluids. Solenoid valves can be found in so many industries as well as the nuclear plant. The ability to be able to detect the presence of faults and predicting the remaining useful life (RUL) of the SOV is important in maintenance planning and also prevent unexpected interruptions in the flow of process fluids. This paper proposes a fault diagnosis method for the alternating current (AC) powered SOV. Previous research work have been focused on direct current (DC) powered SOV where the current waveform or vibrations are monitored. There are many features hidden in the AC waveform that require further signal analysis. The analysis of the AC powered SOV waveform was done in the time and frequency domain. A total of sixteen features were obtained and these were used to classify the different operating modes of the SOV by applying a machine learning technique for classification. Also, a deep neural network (DNN) was developed for the prediction of RUL based on the failure modes of the SOV. The results of this paper can be used to improve on the condition based monitoring of the SOV.

• Computers and Concrete
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• v.15 no.6
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• pp.879-902
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• 2015

The remaining service life (RSL) of buildings has been an important issue in the field of building and facility management, and its development is also one of the essential factors for achieving sustainable infrastructure. Since the estimation of RSL of buildings is heavily affected by the subjectivity of individual inspector or engineer, much effort has been placed in the development of a rational method that can estimate the RSL of existing buildings more quantitatively using objective measurement indices. Various uncertain factors contribute to the deterioration of the structural performance of buildings, and most of the common building structures are constructed not with a single structural member but with various types of structural components (e.g., beams, slabs, and columns) in multistory floors. Most existing RSL estimation methods, however, consider only an individual factor. In this study, an estimation method for RSL of concrete buildings is presented by utilizing a fuzzy theory to consider the effects of multiple influencing factors on the deterioration of durability (e.g., concrete carbonation, chloride attack, sulfate attack), as well as the current structural condition (or damage level) of buildings.