• 한국항공우주학회지
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• 제38권5호
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• pp.456-466
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• 2010

전형적인 하이브리드 모터의 연소 불안정 현상인 DC-Shift는 비선형적 특성을 갖는다. DC-Shift는 두 가지 형태로 나타나게 되는데, 압력이 급격하게 상승하는 양의 DC-shift와 연소 도중에 압력이 갑자기 감소하는 음의 DC-shift로 구분된다. 이 논문에서는 산화제 공급 유동 조건을 다양하게 변화시켜 음의 DC-shift 현상을 유도하고 산화제 공급 유동조건과 하이브리드 로켓이 갖고 있는 기본적인 주파수와 Helmholtz 주파수, 음향모드와의 공진을 유도하여 음의 DC-shift 현상의 발생 조건과 특징에 대하여 알아보았다. 실험 결과 연소 중 수백 Hz 대역의 압력 주파수 이동을 확인하였으며, 음의 DC-Shift가 연소로 발생하는 주파수와 유동의 흐름으로 인한 주파수간 위상이 상호 감쇠되어 발생한 것으로 나타났다. 향후 연소 중 나타나는 주파수의 변화에 따른 DC-Shift 현상에 대해서는 계속 연구되어야 한다.

• Safety and Health at Work
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• 제5권2호
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• pp.73-79
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• 2014

Background: The aim of this study was to investigate the burden experienced by nursing personnel working irregular shifts in Greece and to conduct the first test of a Greek version of the Standard Shiftwork Index (SSI). Methods: A cross-sectional survey was carried out. The SSI was completed by 365 nurses and nursing assistants working shifts, including nights. Results: Female nursing personnel and those suffering from a chronic disease were most affected by working rotating shifts as they had elevated scores on the majority of the SSI scales, such as sleep, chronic fatigue, digestive and cardiovascular problems, general health questionnaire, cognitive and somatic anxiety, shift time satisfaction, engagement and disengagement strategies, languidity, flexibility, and neurotisicm. Nurses with longer working experience and those with family responsibilities also scored higher on some of the SSI scales, such as the sleep, shift time satisfaction, social and domestic disruption, disengagement strategies, morningness, and languidity scales. Conclusion: Shiftwork affects female nurses, those with chronic disease, older age, and domestic responsibilities more severely. Therefore management should take these factors into account when designing work schedules to alleviate the burden caused by shiftwork.

• 대한한방부인과학회지
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• 제21권3호
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• pp.231-244
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• 2008

Purpose: The purpose of this study is to analyze body composition, obesity according to working pattern of working women. The subjects were workers in the automobile manufacturing industry. Methods: The subjects consisted of 514 industrial women workers who had received Korean oriental medicine health examination and submitted questionires about working pattern, during 8 months from April 2005 to November 2005. The body composition was measured by X-scan(Jawon medical, Seoul, Korea). We analyzed the relationship between body composition analysis, obesity and shift pattern with $X^2-test$ using the SPSS Ver. 12.0 Results: Regarding the realationship between body composition and working pattern, shift worker group had a significantly higher level of body weight, ratio of body fat, visceral fat and abdominal fat than normal worker. Conclusion: From this study, we can know that shift work can influence on working women's body composition and obesity.

• Safety and Health at Work
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• 제3권2호
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• pp.110-116
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• 2012

Establishing a causal relationship between factors at work and disease is difficult for occupational physicians and researchers. This paper seeks to provide arguments for the judgement of evidence of causality in observational studies that relate work factors to disease. I derived criteria for the judgement of evidence of causality from the following sources: the criteria list of Hill, the approach by Rothman, the methods used by International Agency for Research on Cancer (IARC), and methods used by epidemiologists. The criteria are applied to two cases of putative occupational diseases; breast cancer caused by shift work and aerotoxic syndrome. Only three of the Hill criteria can be applied to an actual study. Rothman stresses the importance of confounding and alternative explanations than the putative cause. IARC closely follows Hill, but they also incorporate other than epidemiological evidence. Applied to shift work and breast cancer, these results have found moderate evidence for a causal relationship, but applied to the aerotoxic syndrome, there is an absence of evidence of causality. There are no ready to use algorithms for judgement of evidence of causality. Criteria from different sources lead to similar results and can make a conclusion of causality more or less likely.

• 한국직업건강간호학회지
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• 제18권1호
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• pp.106-115
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• 2009

Purpose: Occupational stress is a determinant risk factor for cardiovascular disease and work disability. This study aims to describe occupational stress and identify its related factors among aged security guards. Methods: A random sample of 76 aged security guards were interviewed by three research assistants. The criteria of the subjects were as follows : 50 or older male with 40 or more working hours a week working with colleagues ranged from 3 to 50. The data were collected in September, 2007 and analyzed by multiple regression using SAS Version 9.1. Results: The mean score of occupational stress among aged security guards was 47.2. The mean scores of its sub-scales were 31.3(physical environment), 33.8(occupational demand), 80.8occupational control), 44.6(interpersonal conflict), 51.3 (occupational insecurity), 53.6(occupational system), 57.5(lack of reward), and 30.3(work environment). The scores of occupational control, interpersonal conflict, and occupational insecurity were higher than the scores of Korean average occupational stress sub-scales. Significant variables affecting occupational stress and its sub-scales were work place, work type, and employment type. Conclusion: In order to reduce occupational stress among security guards, sufficient occupational control and interpersonal conflict control, appropriate reward, and employment stability should be considered. Also long working hours and work shift should be improved.

• 한국산업보건학회지
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• 제29권3호
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• pp.368-374
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• 2019

Objectives: To examine the associations of borg's scale with actual heart rates of workers and energy consumption during their physical work. Methods: A total of 72 workers performing physical activities in postal service, ceramic manufacturing, and metal manufacturing participated in heart rate measurement for 1 work shift using the activity meter(A360) and responded to a borg's scale questionnaire. Results: In consistent with previous findings, we presented high correlation between borg's scale and energy consumption measures among workers performing physical activities(r=0.89) while post-work average heart rate showed nearly no correlation with post-work borg's scale (r=0.09). We proposed a set of adjustments when using borg's scale to estimate physical workload for those workers engaged in physical activities during the majority of their work shift. Conclusions: Our findings suggest that a caution should be paid to when using Borg's scale to estimate heart rates during physical activities as well as energy consumption as the product of heart rate measurements.

• 한국산업보건학회지
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• 제25권4호
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• pp.566-572
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• 2015

Objectives: The major objective of this study was to analyze insomnia after the change to consecutive day shift from day and night shift in a motor assembly factory. Materials: Data were collected at before and after shift system change through a survey conducted by a labor union. We analyzed transition of PSQI(Pittsburgh Sleep Quality Index) among 222 workers by separating the day shift week and night shift week. The cut-off point of insomnia was 8.5 on the PSQI. Results: Mean PSQI in the day shift week significantly did not decrease, going from $6.36{\pm}3.23$ to $6.46{\pm}3.00$(p=0.612 by paired t-test), Mean PSQI for night shift week significantly decreased from $8.31{\pm}3.36$ to $6.19{\pm}3.18$(p<0.001 by paired t-test). However, mean PSQI in the day shift week increased from $6.33{\pm}3.83$ to $7.11{\pm}2.86$ in ${\geq}50$ years(p=0.085, by repeated measured ANOVA). Mean PSQI score in the night shift week improved more in the married group(from $8.38{\pm}3.27$ to $6.12{\pm}3.18$) than in the non-married group(from $7.82{\pm}3.27$ to $6.12{\pm}3.18$)(p=0.038, by repeated measured ANOVA). Conclusions: The change to consecutive day shift improved insomnia in night shift. However, insomnia in the day shift week was worsened among those more than 50 years old.

• 한국화재소방학회논문지
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• 제28권2호
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• pp.98-104
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• 2014

소방공무원의 열악한 근무조건을 개선하기 위해서 2004. 6. 1. 소방 방재청 출범과 함께 3교대 근무체제가 제시되었다. 그러나 차일피일 미루어 오다 2008. 12. 행안부장관이 2012년까지 3교대 전면시행을 보고하면서 이듬해 2009년부터 3교대 근무가 시범 실시되었고, 이후 2013년 6월 현재 약 97%의 시행률을 보이고 있지만, 지방재정 열악 등으로 2014년에 완료되는 것으로 알려지고 있다. 한편, 소방공무원 3교대 근무형태에 관한 국내연구는 거의 전무한 실정으로 아주 초보적이고 유치한 수준으로 이제 시작에 불과한 단계라 할 수 있다. 따라서 본 연구는 그동안 시행해 오고 있는 3교대 근무 시행의 문제점과 선결과제 등을 살펴보고, 향후 3교대 근무제의 실효성 확보를 위한 몇 가지 정책적 제언을 하는데 그 목적이 있다.

• Bulletin of the Korean Chemical Society
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• 제5권2호
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• pp.55-60
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• 1984

The NMR shift arising from the electron angular momentum and electron spin dipolar-nuclear spin angular momentum interactions has been investigated for a $4d^1$system in a strong crystal field environment of tetragonal symmetry. A general formula for NMR shift is used to compute the NMR shifts along the (100), (010), (001), (110) and (111) axes. We find that from the computed results, the NMR shift along the (100) and (010) axes is consistent with each other in a strong crystal field environment of tetragonal symmetry, but the NMR shift along the (001) axis is about triply greater in magnitude than those along the (100) and (010) axes and is opposite in sign to those along (100) and (010) axes. In this work, we express the expansion coefficients $a_1^{(i)}$ and $b_1^{(i)}$ of $A_i$ and $B_i$ in terms of $g_m^{(i)}$ and $h_m^{(i)}$ and two matrices $c_{lm}$ and $d_{lm}$ of radial dependence. The NMR shift is also separated into the contributions of multipolar terms. We find that $1/R^3$ term contributes dominantly to the NMR shift along the (100), (010), (001) and (110) axes while along the (111) axis $1/R^5$ term dominantly contributes. However, the contribtions of the other terms may not be negligible.

• 인터넷정보학회논문지
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• 제17권1호
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• pp.35-45
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• 2016

인간의 생체리듬 조절에 관여하는 멜라토닌 호르몬은 빛의 특정 단파장 비율에 따라 민감하게 반응한다. 단파장 비율이 고정된 기존 조명 빛은 재실자 생체리듬 교란 및 수면장애 현상을 초래한다. 특히 교대근무자의 경우, 일정치 않은 근무시간과 항시 동일한 빛 환경으로 인해 생활패턴이 불규칙적으로 변화하여 집중력 저하로 사고 발생의 위험도가 높아지거나 퇴근 이후 숙면을 취하지 못하는 등 건강한 일상생활을 유지하는 데 부정적 영향을 초래한다. 본 논문에서는 교대근무자를 대상으로 근무 또는 퇴근 시점에 따라 각성 및 수면에 적합한 조명 빛을 손쉽게 계측 및 제어할 수 있는 스마트폰 기반의 파장 제어 가능한 LED 조명시스템을 제안한다. 먼저, LED 조명을 대상으로 조광제어비율에 따라 변화하는 조명 빛 특성을 스마트폰에 내장된 컬러센서 및 외부에 연동된 소형 스펙트로미터(Mini-Spectrometer)를 통해 계측한 후 데이터베이스에 저장하고, 저장된 광 특성 데이터를 기반으로 계측 모듈과 조명제어모듈을 구현한다. 교대근무자를 대상으로 시스템 처리 절차에 따라 '근무' 시간대에는 각성이 필요한 시점으로 파악하여 작업유형에 따라 분류한 목표조도를 고려하여 단파장 비율이 최대치인 제어비율로 서비스하고, '퇴근' 무렵에는 자연스럽게 수면 상태에 진입할 수 있도록 단파장 비율이 최소치인 제어비율로 조명 빛을 가변화한다.