• Journal of Navigation and Port Research
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• v.44 no.6
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• pp.439-446
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• 2020

The IMO has adopted emission standards through Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL) that strictly prohibit the use of bunker C oil for vessels. In this study, we have adopted the turret-moored Floating LNG-Bunkering Terminal (FLBT) which is designed to receive the LNG from LNGCs and transfer it to LNG-bunkering shuttles in side-by-side moored condition. Numerical analyses were carried out using the high-order boundary-element method for four vessels at various relative distances. Mean wave drift forces were compared in an operational sea state. A model test was performed in the ocean engineering basin at the Korea Research Institute of Ships & Ocean Engineering (KRISO) to verify the safety of the berthing/unberthing operation. In the model test, a jig was designed to simulate tug boats pushing or pulling the bunkering vessels, so that the friction force of the g operation was not affected. Safety depended on the environmental direction, with more stable operation possible if the heading-control function of FLBT is applied to avoid beam-sea conditions.

• Explosives and Blasting
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• v.39 no.2
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• pp.1-14
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• 2021

Recently, with the development of high-performance processing devices such as GPGPU, a three-dimensional dynamic analysis technique that can replace expensive rock material impact tests has been actively developed in the defense and aerospace fields. Experimentally observing or measuring fracture processes occurring in rocks subjected to high impact loads, such as blasting and earth penetration of small-diameter missiles, are difficult due to the inhomogeneity and opacity of rock materials. In this study, a three-dimensional dynamic fracture process analysis technique (3D-DFPA) was developed to simulate the fracture behavior of rocks due to impact. In order to improve the operation speed, an algorithm capable of GPGPU operation was developed for explicit analysis and contact element search. To verify the proposed dynamic fracture process analysis technique, the dynamic fracture toughness tests of the Straight Notched Disk Bending (SNDB) limestone samples were simulated and the propagation of the reflection and transmission of the stress waves at the rock-impact bar interfaces and the fracture process of the rock samples were compared. The dynamic load tests for the SNDB sample applied a Pulse Shape controlled Split Hopkinson presure bar (PS-SHPB) that can control the waveform of the incident stress wave, the stress state, and the fracture process of the rock models were analyzed with experimental results.

• 한국노년학
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• v.40 no.3
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• pp.459-475
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• 2020

This study examined the moderating effect self-rated health has on the association between grandparenting and depressive symptoms. The fourth wave (in 2012) of the Korean Longitudinal Study of Ageing (KLoSA) was used for the analyses (N=650). The Coarsened Exact Matching (CEM) method was applied in order to ensure randomness in the selection of grandparents who participated in grandparenting and those who did not. The dependent variable was depressive symptoms, the independent variable was grandparenting, and the moderating variable was self-rated health. Control variables were education level, age, household income, gender, marital status and life satisfaction. After matching data by CEM, weighted multiple regression was applied with STATA 13.0. Also, simple slope analysis and region of significance were performed to interpret the interaction terms. The results showed that self-rated health had a significant moderating effect. Specifically, for grandparents with high self-rated health, grandparenting was associated with a lower level of depressive symptoms. On the contrary, for grandparents with low self-rated health, there was no difference depending on whether they participated in raising grandchildren. Based on these results, we discussed the need for consideration of self-rated health for grandparents who participated in grandparenting.

• 한국노년학
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• v.40 no.3
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• pp.511-530
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• 2020

The present study aimed to examine the moderating effects of marital satisfaction (MS) on the association between the number of chronic disease (CD) and depressive symptoms (DS) among ol der men and women. The 6th wave of the Korean Longitudinal Study of Ageing was utilized and the sample was married men (N=585) and women (N=460) aged 65 and over. Multiple regression analysis using SPSS WIN 25.0 and Process Macro was used to test moderating effects of MS. Control variables were age, education, household income, parent-child relationship satisfaction, self-rated health, cognitive function, current smoking status and CD of spouse. Resul ts from elderly men showed the moderating effect of MS was significant. Specifically, those with more CD were more likely to report higher level of DS in the low MS group. However, the effect of CD on DS was not significant in the high MS group. Results from elderly women showed the moderating effect of MS was not significant. This study showed the moderating effect of MS on the association between CD and DS differed by gender in later life. It suggests practical intervention to utilize the resources of spouses is in need to promote mentally healthy aging even though having chronically ill in later life.

• Korean Journal of Optics and Photonics
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• v.34 no.3
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• pp.99-105
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• 2023

The performance of astronomical telescopes can be negatively affected by atmospheric turbulence. To address this issue, techniques for atmospheric turbulence correction have been developed, requiring the simulation of atmospheric turbulence in the laboratory. The most practical way to simulate atmospheric turbulence is to use a phase plate. When measuring a phase plate that simulates strong turbulence, a Shack-Hartmann wave-front sensor is commonly used. However, the laser power decreases as it passes through the phase plate, potentially leading to a weak laser signal at the sensor. This paper investigates the need to control the laser power when measuring a phase plate that simulates strong atmospheric turbulence, and examines the effects of the laser power on the measured wavefront. For phase plates with relatively high Fried parameter r₀, the laser power causes a variation of over 10% in r₀. For phase plates with relatively low r₀, the laser power causes a variation of less than 5%, which means that the influence of the laser power is negligible for phase plates that simulate strong atmospheric turbulence. Based on the system described in this paper, a phase plate simulating strong atmospheric turbulence can be measured at a laser power of 5 mW or higher. Therefore, controlling the laser's output power is necessary when measuring a phase plate for simulating atmospheric turbulence, especially for phase plates with low r₀ values.

• 한국노년학
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• v.39 no.4
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• pp.699-721
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• 2019

The purpose of this study was to examine and compare factors affecting the subjective life expectancy among the elderly, and to suggest health practice and social welfare service implications for later life. A total of 4,483 seniors from the 6th wave(2016) of the Korean Longitudinal Study on Aging (KLoSA) were used for analysis. The subjects were divided into three age groups: the young-old (n=2,106, 65~74 years), middle-old (n=1,803, 75~84 years), and oldest-old (n=574, 85 years and older). Control variables were sociodemographic factors and health status factors. Independent variables were health promotion behavior, cognition of public care, participating social activity, economic activity, and receiving basic pension. The data were analyzed using hierarchical multiple regression. The main results were as follows. Health promotion behavior was associated with the young-old. Social activities and economic activity were associated with the young-old and middle-old. Receiving basic pension had a significant impact on all age groups. In the middle-old, significant results were focused on socio-demographic and health status factors compared to other groups. The results of this study will provide basic data for the elderly policy and welfare service and will help to find and improve the important factors for the life of the elderly.

• Journal of Venture Innovation
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• v.5 no.2
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• pp.85-99
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• 2022

Dryers becoming commercially available for experimental and industrial use are classified to general drying oven, hot-air dryer, vacuum dryer, freezing dryer, etc. and kinds of them are various from the function, size and volume, etc. But the moisture measurement is not applied although it is important factor for the quality control and the performance improvement of products, and then now is very passive because the weight is weighed arbitrarily after dry-end. Generally the method for measuring moisture is divided by a direct measurement method and a indirect measurement method, and the former such as the change of weight or volume on the front and rear of separation of moisture, etc. is mainly used. Relatively a indirect measurement is very limited to apply due to utilize measurement apparatuses using temperature conductivity and micro-wave etc. In this research, we easily designed the moisture measurement system using the open-source based Arduino, and monitored moisture fluctuations and weight profiles in the real-time without the effect of external environment. Concretely the temperature-humidity and load cell sensors were packaged into a drying oven and the various change values were measured, and their sensors capable to operate 60℃ and 80℃ were selected to suitable for the moisture sensitive materials and the food dry. And also the performance safety using the organic samples of banana, pear, sawdust could be secured because the changes of evaporation rate as the dry time and temperature, and the measurement values of load cell appeared stable response characteristics through repeated experiments. Hereafter we judge that the reliability can be improved increasingly through the expansion of temperature-humidity range and the comparative analysis with CFD(Computational Fluid Dynamics) program.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.2
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• pp.163-170
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• 2024

In the literature, inhalation of cosmetic fragrances, including natural extracts or natural essential oils, has been reported to induce brainwave changes. Angelica gigas (AG) and Cnidium officinale (CO) are widely used in East Asian countries as traditional medicines to improve health, but there have been no previous reports of inhaling their aromas and assessing changes in brain activity through electroencephalogram (EEG) recordings. In this study, the scent of natural herbal extracts such as Artemisia princeps var. orientalis (Compositae), AG, and CO was inhaled and evaluated whether emotional state changes were caused by olfactory stimuli, and brain activity was confirmed through EEG records before and after inhaling the scent of natural herbal extracts in subjects aged 20 to 30. We also used an electrocardiogram (ECG) to record the electrical activity of the heart during fragrance administration. The test results indicated that inhaling the scents of Compositae, AG, and CO extracts, as well as the positive control lavender, significantly increased the relative alpha power and the alpha/beta ratio of brain waves across the brain regions. The ECG recordings indicated that the inhalation of Compositae fragrance significantly decreased the low-frequency/high-frequency ratio, and that the inhalation of traditional herbal extract fragrances resulted in comfort and relaxation.

• Sleep Medicine and Psychophysiology
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• v.3 no.2
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• pp.32-42
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• 1996

Objectives : Upper airway resistance syndrome(UARS) is a sleep-related breathing disorder characterized by abnormal negative intrathoracic pressure during sleep. Abnormally increased negative intrathoracic pressure results in microarousal and sleep fragmentation which underlay UARS-associated complaints of daytime fatigue and sleepiness. Although daytime dysfunction in patients with UARS is comparable to that of sleep apnea syndrome, UARS has been relatively unnoticed in clinical setting. That is why UARS is apt to be excluded in diagnosing of sleep-related breathing disorders since its respiratory disturbance index and arterial oxygen saturation are within normal limits. The current study presents a summary of clinical and polysomnographic characteristics found in patients with UARS. The present study aims (1) to explore characteristics of patients diagnosed with UARS, (2) to characterize the polysomnographic findings of UARS patients, and (3) to enhance the understanding of UARS through those clinical and laboratory characteristics. Methods : This was a retrospective study of 20 UARS patients (male 15, female 5) and 30 obstructive sleep apnea (OSA) patients (male 21, female 9) at the Stanford Sleep Disorders Clinic. We diagnosed patients as having UARS when they met critenia, RDI < 5 characteristic findings of an elevated esophageal pressure($<-10\;cmH_2O$), frequent arousals secondary to an elevated esophageal pressure, and symptoms of daytime fatigue and sleepiness. We used polysomnographic value, which is standardized by Williams et al(1974), as normal control. Statiotical test were done with student t-tests. Results : (1) Mean age of UARS was $41.0\;{\pm}\;14.8$ years and OSA was $50.9\;{\pm}\;12.0$ years. UARS subject was significantly younger than OSA subject (p<0.05). (2) The total score of Epworth Sleepiness Scale (ESS) was UARS $9.7\;{\pm}\;6.3$ and OSAS $11.2\;{\pm}\;6.3$. There was no significant difference between two groups. (3) The mean body mass index was UARS $28.1\;{\pm}\;5.7\;kg/m^2$ and OSAS $32.9\;{\pm}\;7.0\;kg/m^2$. UARS had significantly lower meen body man index than OSAS subjects (p<0.05). (4) The polysomnographic parameters of UARS were not significantly different from those of OSA except RDI(p<0.001), $SaO_2$ (p<0.001) and slow wave sleep latency (p<0.05). (5) Compared with normal control, Total sleep time in UARS subjects was significantly shorter (p<0.001), sleep efficiency index was significantly lower (p<0.001), total awakening percentage was significantly higher (p<0.001), and sleep stage 1 (p<0.001) were significantly higher. (6) OSA patients showed poor sleep quality and distinct abnormal sleep architectures compared with normal control. Conclusions : Conclusions from the above results are as follows : (1) UARS patients were younger and had lower body mass index when umpared with OSA patients. (2) The quality of sleep and sleep architectures of the UARS and OSA patients are significantly different from those of normal control. (3) ESS scores and awakening frequencies of UARS are similar with those of OSA, suggesting that daytime dysfunction of UARS patients may be comparable to those of OSA patients. (4) The RDI and the $SaO_2$ which are important indicators in diagnosing sleep-related breathing disorders, of UARS subjects are close to normal value. (5) According to the the above results, we unclude that despite the absence of $SaO_2$ drops and the absence of an elevated number of apnea and hypopnea, subjects developed clinical complaints which were associated with laborious breathing, elevated Pes nadir, and frequently snoring. (6) Accordingly, we suggest including LIARS in the differential diagnosis list when sleep related breathing disorder is suspected clinically and overnight polysomnographic findings except snoring and frequent microarousal are within normal limits.

• Journal of the Korean Applied Science and Technology
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• v.37 no.4
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• pp.769-777
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• 2020

The purpose of this study was to investigate the effects of 8 weeks Self-Myofascial Release exercise on body composition, vascular and metabolic functions in obese female college students. The subjects were 19 obese female college students (n = 9) who were randomly assigned to an exercise group(n=9) and control group(n=9), with an exception of except 1 abandonment. The Self-Myofascial Release exercise group performed exercises twice a week for 8 weeks and for 40 minutes at one time using a foam roller, and the control group maintained normal life pattern for the same period. Body composition was measured by body weight, body fat percentage, vascular function was measured by pulse wave velocity(PWV), augmentation index(AIx), brachial artery vascular flow-mediated dilation(FMD), and metabolic function was measured by fasting glucose and triglyceride levels. The Self-Myofascial Release exercise with foam roller showed no significant effect on body weight and body fat percentage. The Self-Myofascial Release exercise with foam roller showed no significant effect on heart rate, FMD, PWV but, SBP, CSBP and AIx were significant decreased. The Self-Myofascial Release exercise with foam roller showed no significant effect on fasting glucose and triglyceride levels. In conclusion, 8-week Self-Myofascial Release exercise for obese female college students showed no significant effect on body composition and metabolic function, but improved SBP, CSBP and AIx levels significantly. Therefore, Self-Myofascial Release exercise will be an effective way to improve the vascular function of obese female college students.