• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.14.1-14.10
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• 2023

Background: Shift work is known to cause changes in the circadian rhythm of the human body and adversely affect not only physical health but also mental health. Some studies have demonstrated the correlation between shift work and thyroid stimulating hormone (TSH), a hormone that changes according to the diurnal rhythm, but few studies have reported the different TSH levels according to the shift work type. This study aimed to investigate changes in TSH according to the shift work type. Methods: This study included 1,318 female workers who had a medical checkup at a university hospital in Changwon from 2015 to 2019. Shift work types were classified as non-shift work, regular 2 shifts, and irregular three shifts, and a TSH ≥ 4.2 mIU/L was defined as abnormal. A general linear model (GLM) was used to compare the TSH levels and the risk of subclinical hypothyroidism in each year, and a binary logistic analysis was performed using a generalized estimation equation (GEE) to compare the risk of subclinical hypothyroidism over the 5-year period. Results: Of the 1,318 participants included in this study, 363, 711, and 244 were non-shift, two-shift, and irregular three-shift workers, respectively. In the GEE analysis, after adjusting for age, body mass index, smoking, and alcohol consumption, the odds ratios (ORs) were 1.81 (95% confidence interval [CI]: 1.15-2.86; p = 0.011) in 2 shifts and 2.02 (95% CI: 1.23-3.32; p = 0.006) in irregular three shifts, compared to non-shift. Conclusions: Our results showed that shift work had a higher risk of subclinical hypothyroidism than non-shift work and that there was a significant difference in the risk of subclinical hypothyroidism according to the shift work type. These findings suggest that the shift work type can be considered in future thyroid function tests and evaluations.

• Journal of Korean Academy of Nursing
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• v.50 no.4
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• pp.631-640
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• 2020

Purpose: This study aimed to examine premenstrual symptoms (PMS) of shift nurses and identify the association between PMS, sleep, and occupational stress. Methods: This study was conducted with a secondary data analysis that used data from the Shift Work Nurse's Health and Turnover study. The participants were 258 nurses who were working in shifts including night shifts. PMS, sleep patterns (sleep time and sleep time variability), sleep quality, and the occupational stress of each participant were measured using the Moos Menstrual Distress Questionnaire, a sleep diary, an actigraph, the Insomnia Severity Index, and the Korean Occupational Stress Scale, respectively. Data were analyzed using SPSS 23 and STATA 15.1 to obtain descriptive statistics, Pearson's correlation coefficients, multiple linear regression with generalized estimating equations (GEE) and Baron and Kenny's mediating analysis. Results: The average PMS score, average sleep time, average sleep time variability, average sleep quality score, and average occupational stress score of the participants was 53.95 ± 40.45, 7.52 ± 0.89 hours, 32.84 ± 8.43%, 12.34 ± 5.95, and 49.89 ± 8.98, respectively. A multiple linear regression analysis with GEE indicated that sleep time variability (B = 0.86, p = .001), and sleep quality (B = 2.36, p < .001) had negative effects on nurses' PMS. We also found that sleep quality had a complete mediating effect in the relationship between occupational stress and PMS. Conclusion: These findings indicate that both sleep time variability and sleep quality are important factors associated with PMS among shift work nurses. To improve shift nurses' PMS status, strategies are urgently needed to decrease sleep time variability and increase sleep quality.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.264-271
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• 2021

Raman spectroscopy is an equipment that is widely used for classifying chemicals in chemical defense operations. However, the classification performance of Raman spectrum may deteriorate due to dark current noise, background noise, spectral shift by vibration of equipment, spectral shift by pressure change, etc. In this paper, we compare the classification accuracy of various machine learning algorithms including k-nearest neighbor, decision tree, linear discriminant analysis, linear support vector machine, nonlinear support vector machine, and convolutional neural network under noisy and spectral shifted conditions. Experimental results show that convolutional neural network maintains a high classification accuracy of over 95 % despite noise and spectral shift. This implies that convolutional neural network can be an ideal classification algorithm in a real combat situation where there is a lot of noise and spectral shift.

• Journal of Korean Biological Nursing Science
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• v.22 no.4
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• pp.308-316
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• 2020

Purpose: This study aimed to explore the knowledge and performance of sleep hygiene among nurses with shift work schedules and examine the influence on sleep disturbance. Methods: A total of 199 shift-work nurses from a tertiary hospital were included in the study. To examine the knowledge and performance of sleep hygiene, the participants were asked to respond to a self-reported survey. To assess sleep disturbance, the General Sleep Disturbance Scale was used. Descriptive statistics and multiple linear regression were applied using the SPSS/WIN 21.0 program to analyze the data. Results: Both the knowledge and performance of sleep hygiene among nurses with shift work schedules were measured at a moderate level. Nurses' knowledge and the performance of sleep hygiene was not significantly associated with sleep disturbance, whereas age, experience with shift-working, and perceived health status were significantly associated. Conclusion: Strategies for providing more accurate information and motivating better sleep hygiene would help to enhance sleep hygiene in nurses with shift work schedules. Further studies examining the association of knowledge and the performance of sleep hygiene with sleep disturbances in nurses with shift work schedules are needed.

• Safety and Health at Work
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• v.15 no.1
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• pp.102-109
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• 2024

Background: In today's modern world, longer working hours, shift work, and working at night have become major causes of the disruption of our natural circadian rhythms. This study aimed to investigate the effects of the type of shift work (rotating vs. fixed day), duty period (on-duty vs. off-duty), and working period within each shift (nighttime vs. daytime) on the circadian rhythm characteristics of nurses who provide direct patient care. Methods: This cross-sectional study used a purposive sampling method. Cosinor analysis was applied to analyze the actigraphy data of nurses providing direct patient care for seven consecutive days. The linear mixed effects model was then used to determine any variances between shift type, duty period, and working period within each shift for the nurses. Results: The mesor value did not differ according to nurses' shift type, duty period, and working period within each shift. The amplitude was statistically higher in on-duty nurses and in daytime working hours. The acrophase was significantly delayed in nighttime working hours. As well as nurses in rotating shift had experience. Conclusion: Our findings revealed that the peak activity of nurses occurs significantly later at night while working and nurses working during nighttime hours may have a weaker or less distinct circadian rhythm. Thus, this study suggests that limits be placed on the number of rotating nighttime shifts for nurses.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.355-362
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• 2006

Several techniques of MK test, Spearman's Rho test, Linear Regression test, CUSUM test, Cumulative Deviation, Worsley Likelihood Ratio test, Rank Sum test, and Students' t test were applied to detect the trends of slope and shift which exist in hydrologic and climate time series. The time series of annual rainfall, inflow, tree ring index, and southern oscillation index (SOI) were used and the trends of these series were compared in the study. From the results, it can be found that the data could be classified into two categories such as linear trend and shift. 4 series data of 8 rainfall series which reveal the trend show the shift and 8 series data of 18 tree ring index and March and April series of monthly SOI data show shift. Moreover, ADF test and BDS test were used to test stationarity and non-linearity of the data. In conclusion, through the study, various trend analysis techniques were compared and 6 kinds of characteristics which can exist in hydrologic time series were identified.

• Journal of Korean Biological Nursing Science
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• v.13 no.3
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• pp.229-237
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• 2011

Purpose: The objective of this study was to investigate the relationships between sleep quality, fatigue, depression and health promoting behavior by shift-work patterns in university hospital nurses. Methods: A cross-sectional, descriptive survey was conducted using a convenient sample. The self-administered questionnaires were given to 165 nurses (shift workers 91, non-shift workers 74) employed in two university hospital located in Seoul and Gyeunggi-do. Data were collected from February to March, 2010. Results: The shift workers showed significantly lower sleep quality and health promoting behavior, and higher fatigue than non-shift workers. There were significant correlations between fatigue, depression and health promoting behavior in shift workers. There were significant correlations between sleep quality, fatigue, depression and health promoting behavior in non-shift workers. In multiple linear regression analysis, after controlling for total work experiences, predictor of health promoting behavior in shift workers was only fatigue (${\beta}$=-.29, p<.001). Predictors of health promotion behavior in non-shift workers were depression (${\beta}$=-.37, p=.002) and fatigue (${\beta}$=-.27, p=.023). Conclusion: This study failed to provide a clear explanation why sleep quality does not have a comparable effect on health promotion behaviors of shift-workers as well as non-shift workers. However, future research is needed to determine the various risk factors influencing on health promotion behaviors by which shift-work pattern exacerbates fatigue.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.575-585
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• 2006

In Orthogonal Frequency Division Multiple Access (OFDMA) systems, timing synchronization in uplink is accomplished by an initial uplink synchronization called an initial ranging process. The Base Station's receiver synchronizes the symbol timing to specific user's symbol and the other user's symbols have some Symbol Timing Offset (STO). Linear phase shift is occurred by each user's STO in an OFDMA symbol. The Multiple Access Interference (MAI) caused by the summation of each user's linear phase shift degrades the performance of ranging code detection. In this paper, we propose an initial ranging symbol structure with common ranging code for phase shift estimation and compensation. We car estimate the average of phase shift that is generated by each user's STO and compensate this phase shift by using common ranging code. This scheme will suppress the MAI and provide better detection performance than conventional process.

• Korean Journal of Mathematics
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• v.11 no.1
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• pp.1-7
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• 2003

In this paper, we introduce two types of algebraic operations on fuzzy numbers using piecewise linear functions and then show that the Zadeh implication is smaller than the Diense-Rescher implication, which is smaller than the Lukasiewicz implication. If ($f$, *) is an available pair, then $A*_mB{\leq}A*_pB{\leq}A*_jB$.

• Journal of the Korean Data and Information Science Society
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• v.15 no.1
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• pp.129-139
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• 2004

We consider the problem of testing for outliers in generalized linear model. We proceed by first specifying a mean shift outlier model, assuming the suspect set of ourliers is known. Given this model, we discuss standard approaches to obtaining score test for outliers as an alternative to the likelihood ratio test.