• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.235-238
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• 2006

Interface formation between $12CaO{\cdot}7Al_2O_3(C12A7:e^-)$ and Alq3 was investigated using in-situ ultra-violet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). The work function and vacuum level shift of $C12A7:e^-$ were change by different surface treatment from 2.6eV to 4.2eV. Also vacuum level shift $(\Delta)$ at the interface were from +0.3eV to -0.3eV.

• Journal of the Korea Safety Management & Science
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• v.16 no.1
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• pp.45-52
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• 2014

The purpose of this study is to make sure what the stress causes of women's EMTs within the firehouse are, and is to suggest ideas (plans) that are possible to resolve this problem. The reasons are because of difficulties such as not only the overwork at one's tasks, the uncomfortable working environment and circumstances, women's pregnancy, but also shift work or the shift system. It's own ideas about the way to resolve these difficulties are as follows: a separate operation of first-aid department, environmental improvement within a fire house (fire station) via remodeling, activation of substitute man power, alterating women's EMT services into daywork system, mutual encouragement and solicitude among co-workers, reinforcement of the number of the working force to be mobilized, and adoption about the rest year system in employment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.2
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• pp.147-151
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• 2018

Phase-shift fullbridge (PSFB) converter detects the current in the primary side for operation of the peak current mode controller (PCMC). The PCMC must used the slope compensation to solve the problem when the effective duty is over 0.5. The voltage response of PSFB converters has slower than that of buck converter because of slew interval even if the voltage controllers of two converters have same bandwidth. To overcome these problems, this work proposes a compensating method of current reference considering slew interval and fast response in the PSFB converter. The effectiveness of the proposed method is proven using the PSIM simulation and experiment.

• Journal of Korean Institute of Industrial Engineers
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• v.19 no.4
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• pp.87-96
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• 1993

Spectrum analysis of surface electromyogram (FMG) signals is an effective approach to the study of localized muscular fatigue during isometric contraction. Many investigators have con firmed the frequency of the EMG signals being lowered during sustained contaction. In this study, the cyclic loading tasks were performed, and a comparison was made for the median power frequency shift pattern of the EMG signals with the sustained contraction of the same load. The median power frequency shift of the EMG signals for the cyclic loading task was found to be a part of that for the sustained contraction. Based on this result, a new muscle fatigue index was computed by normalizing the duration of the sustained contraction. A fatigue index was obtained as a function of exertion level and the work/rest schedule. With the proposed fatigue index, it is possible to evaluate or predict the degree of muscular fatigue for a physically demanding task.

• Research in Community and Public Health Nursing
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• v.30 no.3
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• pp.368-376
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• 2019

Purpose: In Korea, the prevalence of dementia patients has increased, which makes the care burden of nurses important. The purpose of this study is to identify factors affecting the care burden of nurses caring elderly patients with dementia. Methods: A cross-sectional design was conducted using a convenience sample of 127 nurses from two hospitals and a nursing home in Korea. Participants completed questionnaires on knowledge of and attitudes toward dementia, social support, self-esteem, dementia problematic behavior (DPB), and professional caregiver burden index. The data were analyzed by using the t-test, ANOVA, Pearson correlation, and multiple regression with the SPSS/windows version 21.0 program. Results: The influencing factors for nurse burden include day shift, DPB, self-esteem, social support, which explain 28.0% of care burden of nurses. Conclusion: To reduce the burden of the nurses, there needs to be an administrative system that focuses on enhancing their self-esteem and social support. Active institutional support may be necessary for the nurses taking care of elderly patients with dementia.

• Bulletin of the Korean Mathematical Society
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• v.59 no.2
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• pp.303-318
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• 2022

n-writhes denoted by J_n(K) are virtual knot invariants for n ≠ 0 and are closely associated with coefficients of some polynomial invariants of virtual knots. In this work, we investigate the variations of J_n(K) under arc shift move and conclude that n-writhes J_n(K) vary randomly in the sense that it may change by any random integer value under one arc shift move. Also, for each n ≠ 0 we provide an infinite family of virtual knots which can be distinguished by n-writhes J_n(K), whereas odd writhe J(K) fails to do so.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.6.1-6.12
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• 2022

Background: To date, little is known about the effects of factors linked to work-related fatigue on vibration-exposed workers. Thus, the purpose of this study was (1) to assess the effects of vibration exposure time per week and work-related fatigue on workers and (2) to identify factors associated with work-related fatigue caused by long-term exposure to occupational vibration. Methods: This study used data collected from the 5th Korean Working Conditions Survey. A total of 34,820 non-vibration-exposed and 10,776 vibration-exposed employees were selected from the data. The χ² and multiple logistic regression were used to determine the effect of vibration exposure time per week and the effects of factors of work-related fatigue on workers. Results: The prevalence of work-related fatigue in vibration-exposed workers (30.5%) was higher than that of non-exposed workers (15.9%). The prevalence of work-related fatigue was higher for female and workers with depression, anxiety, and shift work, and those with authority to control their work pace had statistically significantly higher odds than those who did not. The employees who had the authority to control their order of work (odds ratio [OR]: 0.88; 95% confidence interval [CI]: 0.81-0.95) and method of work (OR: 0.90; 95% CI: 0.82-0.98) had statistically significantly lower odds than those who did not. The OR of workrelated fatigue symptoms was highest among employees whose vibration exposure time per week were 30.0%-40.0% (OR: 2.36; 95% CI: 1.96-2.83). Lower OR was observed as vibration exposure time per week decreased. Conclusions: The results of the present study suggest an association between occupational vibration and work-related fatigue and longer vibration exposure time per week, causing an increased prevalence of work-related fatigue symptoms. Measures to protect workers exposed to occupational vibration from work-related fatigue must be taken.

• Safety and Health at Work
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• v.15 no.3
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• pp.360-367
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• 2024

Background: In the food manufacturing industry, exposure to inhalable aerosols contributes to respiratory illnesses such as occupational asthma and rhinitis. However, there is a lack of comprehensive exposure assessment studies. This study evaluated occupational exposure to inhalable aerosols in an instant powdered food manufacturing plant during work operations involving dried food and powders. Methods: In total, 50 workers from an instant powdered food manufacturing plant were recruited. Personal inhalable aerosol exposure measurements were taken for both full-shift and task-based activities. The concentrations of inhalable aerosols were analyzed to identify any variation within and across departments, as well as between seasons, handedness, and sex. Results: In total, 134 personal air samples were collected, and the particulate mass was determined gravimetrically. The concentrations of inhalable aerosols ranged from 0.1 to 27 mg/m³ for full-shift exposure measurements and 3.1 to 73 mg/m³ for task-based measurements. Statistically significant differences in mean aerosol concentrations were found across departments (A:B p < 0.001, A:C p < 0.05, B:C p < 0.001) and between seasons (p < 0.001). Conclusion: This study revealed high exposure to inhalable aerosols among workers, particularly those involved in manual weighing, mixing, and adding powders. The significant differences between departments highlight the specific activities contributing to increased inhalable aerosol concentrations. Seasonal variations were also evident, with autumn showing higher concentrations of inhalable aerosols in all departments compared with summer. These findings emphasize the importance of understanding the distribution of aerosol concentrations across different work tasks and departments, particularly during different seasons.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.2
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• pp.167-173
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• 1998

Many workers like welders work in squatting postures with the object on the ground during an entire work shift. It is suspected that such prolonged squatting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to examine the physical stress caused by the prolonged squatting and to recommend a safe work/rest schedule for a welding task with squatting posture based on the lab experiments. In this study, 8 healthy student subjects participated in the experiment. They maintained a squatting work posture for 16 minutes with 4 different stool height conditions: no stool; 10cm height; 15cm height; and 20cm height. Every 2 minutes, the discomfort was subjectively assessed with the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort ratings, we found that a 10cm height stool relieved the workload most. Discomfort rating results also indicated that a 20cm height stool showed the highest workload, and the there were no difference in workload between a 15cm height stool and no stool. We recommend to use low height stools and to maintain such working postures no longer than 6 minutes for prolonged squatting tasks.