• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• 가정간호학회지
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• 제26권3호
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• pp.288-299
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• 2019

Purpose: This study was conducted to identify factors influencing asthma, with a focus on obesity and systemic inflammation, in Korean adults. Methods: This study was a secondary analysis of data from the sixth Korea National Health and Nutrition Examination Survey (2015). A total of 3,693 individuals aged ≥19 years were included. The prevalence of asthma was 1.6% in the normal weight group (n=23), 1.4% in the overweight group (n=13), and 2.9% in the obese group (n=39). Data included markers associated with systemic inflammation such as high sensitivity C-reactive protein level, leukocyte count, hemoglobin level, and hematocrit value based on previous studies. The results were analyzed using a complex sampling design analysis and by multiple logistic regression analysis with SPSS WIN 24.0 program. Results: In the obese group, age between 50 and 59 years (adjusted odds ratio [AOR]=14.06, 95% confidence interval [CI]=1.84-27.14); age between 60 and 69 years (AOR=3.30, 95% CI=1.34-8.14); age ≥70 years (AOR=3.22, 95% CI=1.31-7.93); female gender (AOR=2.32, 95% CI=1.12-4.78); leukocyte count (AOR=1.18, 95% CI=1.01-1.38), and hemoglobin levels (AOR=0.60, 95% CI=0.45-0.81) were identified as factors influencing asthma. Conclusion: The results can be used to develop nursing interventions to prevent asthma associated with obesity in hospitals or home-based healthcare settings.

• Journal of Biosystems Engineering
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• 제36권1호
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• pp.33-39
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• 2011

An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applied to investigate the potential of reflectance sensing in estimating soil properties for Korean paddy fields. Soil cores up to a 65-cm depth were collected from 42 paddy fields representing 14 distinct soil series that account for 74% of the total Korean paddy field area. These were analyzed in the laboratory for several important physical and chemical properties. Using air-dried, sieved soil samples, reflectance data were obtained from 350 to 2500 nm on a 3 nm sampling interval with a laboratory spectrometer. Calibrations were developed using partial least squares (PLS) regression, and wavelength bands important for estimating the measured soil properties were identified. PLS regression provided good estimations of Mg ($R^2$ = 0.80), Ca ($R^2$ = 0.77), and total C ($R^2$ = 0.92); fair estimations of pH, EC, $P_2O_5$, K, Na, sand, silt, and clay ($R^2$ = 0.59 to 0.72); and poor estimation of total N. Many wavelengths selected for estimation of the soil properties were identical or similar for multiple soil properties. More important wavelengths were selected in the visible-short NIR range (350-1000 nm) and the long NIR range (1800-2500 nm) than in the intermediate NIR range (1000-1800 nm). These results will be useful for design and application of in-situ close range sensors for paddy field soil properties.

• 생물정신의학
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• 제27권1호
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• pp.9-17
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• 2020

Objectives The purpose of this study is to investigate the interest level, perception and attitude of suicide high-risk group toward the media's suicide report, and also to provide the fundamental data in order to strengthen both the standard and the recommendation of media coverage in Korea. Methods We analyzed the data from the 2013 The Korea National Suicide Survey. The study included 1500 participants aged between 19 and 75 years. The participants were selected through the regional multi-layer stratification method using the sampling frame of the 2010 Census. One-on-one face-to-face interviews investigated the interest level, opinions, and attitudes toward suicide reports and collected data on past suicide history and demographic data. The collected data were evaluated using multiple logistic regression analysis. A probability level of p < 0.05 was considered statistically significant. Results The suicide high risk groups with histories of suicidal ideations or attempts showed more interest in suicidal reports [suicidal thought odds ratio (OR) = 1.81, 95% confidence interval (CI) = 1.40-2.34 ; suicidal attempt OR = 3.21, 95% Cl = 1.52-6.78]. However, there was no difference among the groups in thought that suicide reports incite suicide (suicidal thought OR = 1.26, 95% Cl = 0.92-1.73 ; suicidal attempt OR = 0.96, 95% Cl = 0.44-2.09). The suicide high risk groups showed a positive attitude toward suicide reports, but it was not statistically significant (suicidal thought OR = 1.10, 95% Cl = 0.41-2.92 ; suicidal attempt OR = 1.10, 95% Cl = 0.76-1.59). Conclusions We suggest the need of careful attitude of media suicidal reports not to bring about copycat suicides. and also we offer suicide prevention campaign based on media leverage.

• 보건교육건강증진학회지
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• 제20권4호
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• pp.13-26
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• 2003

Objectives： The aim of the present study was to determine the prevalence depressive symptoms, and the correlates of depressive symptoms, and to propose countermeasures for individual depression risk factors among college students. Methods： One university and three colleges in Jeju-do were selected as the study population and a total of 1000 students were selected by multiphasic cluster sampling to represent each department and year within each college. Of the 945 total respondents, 421 were men and 524 were women. The Beck Depression Inventory was used to evaluate depression and the BDI STEN score was used to assess depressive symptoms. Multiple logistic regression analysis was performed for comparisons. Results： 1. The prevalence of depressive symptoms among men was 14.4%, while among women the level rose to 26.8%. 2. Those with poor life satisfaction scores were significantly more likely to have depressive symptoms than those with good life satisfaction (odds ratio (OR) ＝ 2.62； (95% confidence interval (95%CI), 1.483-4.629). 3. Students over 23 years old were significantly more likely to have low levels of depressive symptoms than those under 18 (OR ＝ 0.439； 95%CI, 0.247-0.779). 4. Groups with poor body image satisfaction had higher levels of depressive symptoms when compared to respondents who had good body image (OR = 2.847; 95%CI, 1.341-6.045). 5. Students with poor perceived health status were significantly more likely to have high levels of depressive symptoms than those with good perceived health status (OR ＝ 2.029； 95%CI, 1.157-3.557). Conclusion： Universities and colleges should provide education programs, such as health education that facilitates the development of a healthy body image. In addition, they should focus on various scholarships that could improve satisfaction with student life, especially for alienated students. Furthermore, colleges should help direct students towards engagement in more productive work, and lead social policies away from the dominance of appearance.

• Safety and Health at Work
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• 제10권1호
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• pp.80-86
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• 2019

Background: Emigration of health-care workers is a problem within global health systems which affects many countries, including Peru. Several factors have caused health-care workers to emigrate, including burnout syndrome (BS). This study aims to identify the association between BS and its dimensions with the intention of physicians and nurses to emigrate from Peru in 2014. Methods: A cross-sectional study, based on a secondary analysis of the National Survey of Health Users (ENSUSALUD - 2014) was conducted. Sampling was probabilistic, considering the 24 departments of Peru. We include the questionnaire for physicians and nurses, accounting for 5062 workers. BS was measured by the Maslach Burnout Inventory-Human Services Survey. Adjusted odds ratio (OR) was calculated using multiple logistic regression. Results: Of the study population, 44.1% were physicians, 37.7% males, and 23.1% were working in Lima. It was found that 2.8% [95% confidence interval (CI): 2.19-3.45] of health-care workers had BS. The overall prevalence of intention to emigrate among health-care workers was 7.4% (95% CI: 6.36-8.40). Association was found between BS and intention to emigrate in Peruvian health-care workers (OR = 2.15; 95% CI: 1.05-4.40). Emotional exhaustion was the BS dimension most associated with intention to emigrate (OR = 1.80; 95% CI: 1.16-2.78). Conclusion: Physicians and nurses from Peru who suffered from BS were more likely to have intention to emigrate. Policies should be established to reduce BS as a strategy to control "brain drain" from health-care workers of Peru.

• 대한간호학회지
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• 제51권4호
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• pp.489-504
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• 2021

Purpose: This study was investigated the mediating effect of coping behaviors in the relationship between the second victim experiences after patient safety incidents and the nursing practice changes. Methods: A cross-sectional survey was performed using structured questionnaires. Participants were 218 clinical nurses in general tertiary hospitals in South Korea. Data were collected through an online survey and snowball sampling from August 11 to September 6 2020. Data were analyzed using SPSS 23.0 program. A mediation analysis was performed using multiple regression and a simple mediation model applying the PROCESS macro with 95% bias-corrected bootstrap confidence interval. Results: The mean scores of second victim experiences was 3.41/5. Approach coping (β = .55, p < .001) and the avoidant coping (β = - .23, p = .001) showed mediation effects in the relationship between second victim experiences and constructive change in nursing practice. Avoidant coping (β = .29, p < .001) showed a mediation effect in the relationship between second victim experiences and defensive change in nursing practice. Conclusion: Coping behaviors has a mediating effect on the relationship between second victim experiences and nursing practice changes. To ensure that nurses do not experience second victim, medical institutions should have a culture of patient safety that employs a systematic approach rather than blame individuals. They also need to develop strategies that enhance approach coping and reducing avoidant coping to induce nurses' constructive practice changes in clinical nurses in experiencing second victims due to patient safety incidents.

• Journal of Nutrition and Health
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• 제56권5호
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• pp.523-536
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• 2023

Purpose: This study investigated the association between sleep problems and food allergies (FAs) in Chinese preschoolers and assessed whether there is a difference in this association among children with/without siblings. Methods: A cluster-stratified sampling approach was employed to select four districts in Chongqing based on demographic considerations. A total of 16 kindergartens (n = 966 parents) participated in this study. Parents completed the Children's Sleep Habits Questionnaire (CSHQ) and a standard FAs questionnaire. Analysis of covariance and multiple logistic regression were used to assess the associations between sleep problems and FAs after adjusting for relevant confounders. Results: The study found that 16.3% of children had FAs, with eggs, shellfish, and fruit being the most common allergenic foods. The prevalence of FAs was significantly higher in single children (20.63%) than in children with siblings (13.36%). A total of 70.39% of children had CSHQ scores above the clinical cut-off for sleep disorder. Factor analysis revealed five underlying dimensions from the CSHQ. Factor scores, except for the 'difficulty morning waking' factor, were not significantly different between the two groups. Remarkably, the factor scores of 'parasomnias' and 'sleep anxiety' were significantly higher when children had both siblings and FAs. For all subjects, the odds ratios (ORs) of FAs significantly increased with the presence of sleep disorder (OR, 2.35; 95% confidence interval [CI],1.50-3.68) and 'difficulty falling asleep' (OR, 1.34; 95% CI, 1.22-1.48). The subgroup analysis showed that the probability of FAs significantly increased with the 'difficulty falling asleep' (OR, 1.32 vs. 1.38) and sleep disorder (OR, 2.48 vs. 2.14) in children with and without siblings, respectively. The 'parasomnias' was positively associated only with children with siblings. Conclusion: This study suggests that children with siblings might be more susceptible to FAs when accompanied by certain sleep problems. Further studies are warranted to address the underlying dimensions and possible mediation effects of having siblings with sleep problems.

• Journal of Preventive Medicine and Public Health
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• 제57권1호
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• pp.83-90
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• 2024

Objectives: Professional firefighters face various health hazards and are required to maintain both physical and mental fitness to effectively mitigate crises and respond to emergencies. Moreover, the long working hours and shift work of this profession impact sleep quality. This study investigated the quality of sleep and its associated factors among firefighters in Bangkok, Thailand. Methods: This was a cross-sectional study of firefighters affiliated with the Bangkok Fire and Rescue Department, Bangkok Metropolitan Administration, Thailand between January 2023 and March 2023. A cluster random sampling technique was utilized to distribute 600 questionnaires to firefighters in 15 fire stations. The questionnaire addressed demographic, work-related, and environmental factors. Sleep quality was assessed using the Thai version of the Pittsburgh Sleep Quality Index (PSQI). Data analysis involved both descriptive and inferential statistics. Bivariate and multiple logistic regressions were performed. Results: The response rate was 78.7% (n=472), and 44.1% of the firefighters reported poor sleep quality (PSQI score >5). Sleep quality was statistically associated with conflicting family relationships (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.1 to 2.9), additional part-time jobs (daytime, OR, 2.4; 95% CI, 1.3 to 4.4; or nighttime, OR, 4.3; 95% CI, 1.1 to 16.7), noisy sleeping areas (OR, 1.7; 95% CI, 1.1 to 2.8), and the availability of adequate bedding (OR, 3.0; 95% CI, 1.8 to 4.9). Conclusions: Poor sleep quality among firefighters was associated with various personal, work-related, and environmental factors. Organizations should promote policies that improve sleep quality through good sleep hygiene practices and facilities.

• 해양환경안전학회지
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• 제27권6호
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• pp.708-720
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• 2021

가막만 북서내만해역에서 매년 여름 발생하는 빈산소수괴는 해양환경에 악영향을 미쳐왔다. 따라서, 본 연구는 빈산소수괴 발생시기의 집중적인 현장조사 결과를 바탕으로 다중회귀분석(MRA)을 이용하여 빈산소수괴의 종합적인 발생 메커니즘을 밝혀내고, 그 주요인에 따른 빈산소수괴 관리방안의 방향성을 모색하였다. 그 결과, 2017년 첫 빈산소수괴는 6월 26일에 발생하였으며, 기상 조건에 의한 수온약층의 형성과 퇴적된 유기물의 영향으로 형성되었다. 이어 7월 12일에는 강우량의 증가에 의한 염분약층의 형성으로, 조사 시기 중 빈산소수괴가 수직 및 수평적으로 가장 크게 확장되었다. 그리고, 8월 8일에는 소량의 강우로 빈산소수괴가 크게 약화되었으며, 이때 주 요인은 Chlorophyll-a 농도 증가(식물플랑크톤 증식)과 퇴적된 유기물이었다. 그리고, 약 1주일 후인 8월 16일에는 많은 강우량에 기인한 매우 안정된 염분약층과 Chlorophyll-a 농도 증가(식물플랑크톤 증식)에 의해 크게 확장된 빈산소수괴가 재발생하였다. 이후 9월 13일의 빈산소수괴 소멸시기에서는 빈산소수괴가 해저 면을 따라 얕게 확장되었으며, 퇴적된 유기물에 의해 주로 영향을 받은 것으로 나타났다. 이는 빈산소수괴 관리를 위해서는 퇴적된 유기물의 개선뿐만 아니라 성층의 완화 기술이 필요함을 암시하였다.