• Safety and Health at Work
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• 제12권1호
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• pp.102-107
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• 2021

Background: This study was conducted to identify the association between sleep duration and suicidal ideation among farmers in Korea. Methods: We used Safety for Agricultural Injuries of Farmers cohort data collected from September 2015 to June 2018, which was an agricultural survey on the health and behaviors of adult farmers in Jeju island, Korea. Results: A total of 964 participants were included in the analysis, and 3.7% of them were identified with having suicidal ideation. The frequencies of average daily sleep duration of <6 h (short sleep), 6-8 h (normal sleep), and >8 h (long sleep) were 24.4%, 70%, and 5.6%, respectively. Multivariate analyses revealed that short sleep duration was significantly associated with suicidal ideation compared with normal sleep duration (odds ratio = 2.49, 95% confidence interval = 1.07-5.77). Conclusion: Our findings suggest that short sleep duration in farmers result in higher suicidal ideation. Because individuals who have suicidal ideation often commit suicide, careful monitoring is required to prevent suicide in farmers with short sleep duration.

• Journal of Preventive Medicine and Public Health
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• 제56권5호
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• pp.458-466
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• 2023

Objectives: The association between long sleep duration and mortality is frequently attributed to the confounding influence of comorbidities. Nevertheless, past efforts to account for comorbidities have yielded inconsistent outcomes. The objective of this study was to evaluate this relationship using a large prospective cohort in Korea. Methods: The study included 114 205 participants from the Health Examinees Study, who were followed for a median of 9.1 years. A composite comorbidity score was developed to summarize the effects of 21 diseases. Using Cox proportional hazards regression, hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause, cancer, and cardiovascular mortality associated with sleep duration were estimated. These estimates were adjusted for socio-demographic factors, lifestyle factors, body mass index, and comorbidity score. Additionally, a stratified analysis by subgroups with and without comorbidities was conducted. Results: Throughout the follow-up period, 2675 deaths were recorded. After all adjustments, an association was observed between a sleep duration of 8 hours or more and all-cause mortality (HR, 1.10; 95% CI, 1.01 to 1.20). However, no such association was detected in the stratified analysis for the subgroups based on comorbidity status. Conclusions: Long sleep duration was found to be associated with all-cause mortality among Koreans, even after adjusting for comorbidities. Additional studies are required to explore the mechanism underlying the association between sleep duration and major causes of mortality.

• 한국자동차공학회논문집
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• 제9권6호
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• pp.40-46
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• 2001

An experimental investigation is proceeded to study on the relationship between spark ignition characteristics and the performances of an S. I. engine. The ignition parameters examined in this study are the ignition energy and discharging duration. The combustion pressure and exhaust gas are measured during the experiment. From the measured data of cylinder pressure, the heat release rate, the mass fraction burned, and the COV of IMEP are calculated. The dwell time and the injection time are varied. A single cylinder engine and a 30kW dynamometer are employed. Four different kinds of ignition systems are assembled, and one commercial ignition system is adopted. The experimental results show that the ignition energy is increased as the dwell time extended until the ignition energy is saturated. The higher ignition energy is effective in achieving the laster burning velocity and less producing HC emission. However, when the amount of ignition energy is similar, while the discharge duration becomes longer, the burning velocity is reduced but the engine operation becomes stable in terms of the COV of IMEP.

• 한국기계기술학회지
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• 제20권6호
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• pp.783-789
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• 2018

This paper investigates the relationship of voltage and current waveform between normal piezo injector and deterioration abnormal piezo injector. The experimental methods using Pico oscilloscope and GDS scan tool are employed to measure current and voltage waveform and fuel pressure of piezo injector. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) In case of normal injector, the fluctuation of duration time of piezo injector was linearly and regularly decreased with increasing engine speed, but the that of deterioration piezo injector was irregularly decreased with increasing engine speed. 2) In main injection, the peak value of the current waveform of abnormal injector was larger than that of normal injector, the duration time of deteriorated abnormal injector was less than that of normal injector at 800rpm and 1500rpm, but the duration time of deteriorated abnormal injector was larger than that of normal injector at 2000rpm and 3000rpm. This irregularity appears to be caused by the deterioration of the injector.

• 말소리와 음성과학
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• 제15권3호
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• pp.9-16
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• 2023

The current study investigated the influence of age of L2 acquisition (AOA) and length of residence (LOR) in the L2 setting country on the production of voicing-conditioned vowel duration and spectral qualities in English by Korean learners. The primary aim was to explore the ways in which the language-specific phonetic features are acquired by the age of onset and L2 experience. Analyses of the archived corpus data produced by 45 native speakers of Korean showed that, regardless of AOA or LOR, absolute vowel duration was used as a salient correlate of voicing contrast in English for Korean learners. The accuracy of relative vowel duration was influenced more by onset age than by L2 experience, suggesting that being exposed to English at an early age may benefit the acquisition of temporal dimension. On the other hand, the spectral characteristics of English vowels were more consistently influenced by L2 experience, indicating that immersive experience in the L2 speaking environment are likely to improve the accurate production of vowel quality. The distinct influence of the onset age and L2 experience on the specific phonetic cues in L2 vowel production provides insight into the intricate relationship between the two factors on the manifestation of L2 phonological knowledge.

• 한국유통학회지:유통연구
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• 제10권2호
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• pp.99-120
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• 2005

이 연구에서는 기존 연구의 검토를 통해 인터넷 쇼핑몰의 서비스품질 차원으로 환경적 품직, 고객-기업간의 일반적인 상호작용, 고객-기업간의 개인화된 상호작용, 고객간의 상호작용 및 결과적 품질을 도출하였다. 먼저 인터넷 쇼핑몰 서비스품질의 각 차원이 고객관계의 질을 구성하는 만족, 신뢰, 몰입에 미치는 영향을 실증하였다. 이들의 관계를 이용기간으로 측정한 관계지속기간이 조절하는지의 여부를 검토하였다. 만족과 신뢰 및 몰입 간의 관계를 분석하였다. 또한 관계의 질을 구성하는 세 요인과 관계지속에 대한 미래의도의 관계를 실증하였다. 기존 연구들에 바탕을 두고 구성한 측정척도들로 구성된 설문지를 이용하여 대학생 및 일반 성인을 대상으로 수집한 유효설문지를 349부를 이용하여 회귀분석을 실시하였다. 환경적 품질과 만족, 개인화된 상호작용과 신뢰를 제외한 서비스 품질 차원과 관계의 질 구성요소 사이의 관계는 통계적으로 유의한 결과를 얻었다. 관계의 강도는 차원마다 다른것도 확인하였다. 이용기간의 조절효과는 일반적인 상호작용과 신뢰의 관계에서만 확인할 수 있었다. 만족은 신뢰와 몰입과, 그리고 신뢰는 몰입과 정의 상관관계를 갖는 것으로 나타났다. 신뢰와 몰입은 관계지속에 대한 미래의도에 영향을 미치는 것으로 나타났지만, 만족과 미래의도 사이에는 직접적인 관계를 확인할 수 없었다. 이상의 연구결과를 토대로 시사점과 향후 연구과제를 제시하였다.

• 한국식생활문화학회지
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• 제28권5호
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• pp.539-546
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• 2013

The aim of this study was to investigate the effect of sleep duration on dietary habits and body composition of university students. Sleep duration has recently been added to the list of risk factors for obesity. However, studies on this topic are fairly limited particularly in Korea. We studied the relationship between the duration of sleep and obesity principally based on body mass index and %body fat in university students. For this purpose, a survey was conducted on a total of 312 university students. The subjects enrolled for this study were divided into two groups: (1) those with sleep duration of <7 hours (148 students) and (2) those with sleep duration of >7 hours (164 students). Based on a self-reporting method, the participants filled up the questionnaires for more than 20 minutes. Based on the overall data obtained, we observed that most students (52.88%) skipped breakfast. This was mainly due to shortage of time (60.58%). We also observed that self-reporting dietary preferences included eating irregular meals (49.04%), overeating (19.55%), imbalanced diet (16.35%), and skipping meals (9.94%). It was found that cookies were the favorite snacks in the majority of the participants (50%). Our data reveal that the body mass index, fat mass, visceral fat, and subcutaneous fat, respectively of the shorter sleep duration group (<7 h/day) were 23.78 $kg/m^2$, 19.13 kg, 2.23 kg, and 11.15 kg. In contrast, in those of the control group (7 h/day), these values were found to be 21.84 $kg/m^2$, 13.88 kg, 1.56 kg, and 12.11 kg. We also observed that there were significant correlations of sleep duration with body mass index (p<0.05), fat mass (p<0.01), visceral fat (p<0.01), and beck depression score (p<0.01). Our data suggest that the body mass index in the shorter sleep duration group was higher than that of the control group; however, %fat, visceral fat, and subcutaneous fat in the shorter sleep duration group were found to be higher than those of the control group. The data obtained through our study suggest that short sleep duration is clearly associated with a modest increase in general and abdominal obesity particularly in university students.

• 한국수정란이식학회지
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• 제23권3호
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• pp.141-145
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• 2008

The objective of this study was to investigate the relationship between behavioral signs and duration of estrous in Hanwoo and Holstein cattle for the prediction of optical insemination. Fifty two of 58 and 71 of 89 in Hanwoo and Holstein cows or heifers showed estrous exhibition within 72 h after 2 days following $PGF_{2}\alpha$ administration, respectively. The number of mounting and standing heat were 54.2 and 57.6, 59.4 and 53.5, 42.0 and 30.8 and 16.2 and 10.7 times in Hanwoo cows, Hanwoo heifers, Holstein cows and Holstein heifers, respectively. Duration of mounting were no significantly difference for Hanwoo cows ($21.2\pm11.3$), Hanwoo heifers ($19.9\pm11.4$), Holstein cows ($8.7\pm4.4$) and Holstein heifers ($16.9\pm8.0$). Duration of standing heat were significantly (p<0.05) shorter for Holstein cows ($5.4\pm3.4$) than for Hanwoo cows ($17.1\pm9.6$), Hanwoo heifers ($16.5\pm6.3$) and Holstein heifers ($15.0\pm7.2$). Time until mounting after injection of $PGF_{2}\alpha$ were significantly (p<0.05) longer for Holstein cows ($56.3\pm11.45$) than for Hanwoo cows ($42.71\pm10.44$), Hanwoo heifers ($36.6\pm8.21$) and Holstein heifers ($40.70\pm6.15$). Time until standing heat after injection of $PGF_{2}\alpha$ were significantly (p<0.05) longer for Holstein cows ($61.6\pm8.92$) than for Hanwoo cows ($46.2\pm11.49$), Hanwoo heifers ($42.7\pm6.06$) and Holstein heifers ($44.1\pm6.72$). In the results of this study, duration of standing heat was the shortest in Holstein cows ($5.4\pm3.4$). The estimation of estrous with Holstein cows has more difficulty because to significantly shorter duration of standing heat than for Hanwoo cows, Hanwoo heifers and Holstein heifers. The standing heat can be a good predictor for time of ovulation but it is concluded that mounting behavior could be the best predictor for time of ovulation.

• 대한간호학회지
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• 제45권3호
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• pp.420-428
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• 2015

Purpose: Purpose was to explore associations between sleep duration and metabolic syndrome (MS) risks, and to determine factors associated with self-rated health (SRH) of adults with MS compared to other adults. Methods: This is a secondary data analysis based on the Fifth Korea National Health and Nutrition Examination Survey KNHANES V (N=12662). Study instruments included sleep duration, MS risk factors, SRH and health-related quality of life (HRQoL). Results: Mean age of participants was $43.68{\pm}12.26years$. Fifty-eight percent were women, and 18.3% were identified as having MS. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and SRH were significantly different according to sleep duration (p <.05) among all participants. In the non MS group, male gender, younger age (19~30 and 41~50 age brackets) upper income level, sufficient sleep duration, and high density lipoprotein (HDL) were positively associated with SRH, whereas, lower education levels (${\leq}$ middle school), glucose level, and waist circumference were negatively associated with SRH (p <.05). In the MS group, lower income, lower education levels (${\leq}$ middle school), glucose level, and waist circumference were negatively associated with SRH, whereas, having an occupation was positively associated with SRH (p <.05). Conclusion: Results suggest that tailored approaches are required for prevention and control of MS and sleep duration of each individual should be considered rather than applying standardized guidelines. However, as sleep quality was not included in the analysis, further investigations regarding influence of sleep quality on MS and SRH and controlling for other lifestyle and health behavior factors are required.

• Wind and Structures
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• 제19권3호
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• pp.339-352
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• 2014

This paper discusses the appropriate duration for basic gust wind speeds in wind loading codes and standards, and in wind engineering generally. Although various proposed definitions are discussed, the 'moving average' gust duration has been widely accepted internationally. The commonly-specified gust duration of 3-seconds, however, is shown to have a significant effect on the high-frequency end of the spectrum of turbulence, and may not be ideally suited for wind engineering purposes. The effective gust durations measured by commonly-used anemometer types are discussed; these are typically considerably shorter than the 'standard' duration of 3 seconds. Using stationary random process theory, the paper gives expected peak factors, $g_u$, as a function of the non-dimensional parameter ($T/{\tau}$), where T is the sample, or reference, time, and ${\tau}$ is the gust duration, and a non-dimensional mean wind speed, $\bar{U}.T/L_u$, where $\bar{U}$ is a mean wind speed, and $L_u$ is the integral length scale of turbulence. The commonly-used Durst relationship, relating gusts of various durations, is shown to correspond to a particular value of turbulence intensity $I_u$, of 16.5%, and is therefore applicable to particular terrain and height situations, and hence should not be applied universally. The effective frontal areas associated with peak gusts of various durations are discussed; this indicates that a gust of 3 seconds has an equivalent frontal area equal to that of a tall building. Finally a generalized gust response factor format, accounting for fluctuating and resonant along-wind loading of structures, applicable to any code is presented.