• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.84-90
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• 2017

Explosive bolt is coupled in a variety of guided weapons and space projectiles, to perform the separation function. Thus, the role of the explosive bolt in guided weapons systems is very important, as it can cause failure of the entire system in the case of mission failure. For this reason, the design life prediction for explosive bolt is highly and frequently required recently, but its accurate prediction method has not been presented. In order to apply the existing accelerated aging process, we should know the activation energy and the acceleration factor of the explosive bolt. Since the information required for accelerated aging is not presently secured, it is difficult to predict the design life of explosive. Thus, in the present study, we have evaluated the performance of actual explosive bolts in the condition of natural aging over 10 years in order to present a minimum design life.

• Journal of Digital Contents Society
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• v.18 no.4
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• pp.621-629
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• 2017

According to the rapid population aging and the increase of the number of people with chronic diseases, the digital healthcare services are getting more and more attention. Recent improvement in information technology has expanded the consumers of digital healthcare service from the patients to the general population. Therefore, there is a growing need for studies on the status and needs of digital healthcare users in general. This study conducted a survey of 1,000 people on their perception and attitude about four areas of digital healthcare: internet health information service, smartphone healthcare application, wearable device, and u-health. The questionnaire asked the respondents about their past experience of using digital healthcare services, the purpose of use and point to be improved. The respondents were also asked about new type and contents of digital healthcare service which they would like to use. The survey results will help developers of digital healthcare service by improving their understanding and identifying unmet needs from the general population.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.595-601
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• 2020

During the safety inspection of nitrocellulose-made explosive containers stored for more than 10 years, cracks were found in the containers. Therefore, a failure cause analysis test was performed. First, the cause of failure through the failure tree analysis was conducted to select the factors that influenced failure. The changes in the properties of the container caused by the acceleration of the reaction were found to be the cause of the failure by confirming the influence on the environment and internal/external factors that may occur during storage. To confirm this, environmental tests, such as thermal shock test and vacuum thermal stability test, were performed using a naturally aged container to analyze the cause of failure, and an accelerated aging test was performed to reproduce the failure. Through this, the chemical reaction was accelerated by heat and charge, as in the result of the fault tree analysis, and it was confirmed that the physical properties of the container were changed. In addition, the service life of the container was estimated using the Arrhenius model for the storage life due to thermal aging.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.4
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• pp.19-24
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• 2013

The problem of elderly people with weak physical health has become a very important issue in the aging society. Elderly people with very low judgment and decision-making skills often falls because of the degradation of the strength and balance. Due to the fall triggered off fractures, parenchyma damage, and casualties, generally fast emergency treatment is needed. In this paper, an automatic fall detection system consisting of a triaxial accelerometer and tilt sensor. Using the fall system, the performance of the system was analyzed in many situations. The experimental results showed more than 92% analytical skills.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.1
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• pp.1-7
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• 2022

The number of patients with many complications grows with the increase of aging population. As the elders and severely ill patients spend most of their time in bed, it leads to Pressure Injuries (PI) such as bedsores. Unfortunately, there is no method to automatically detect changes in patient's posture which leads to the need for a caregiver every set of times when the patient needs to be moved. Many studies are conducted to solve this inefficient problem. Yet, these studies require costly devices or use methods that disturb patient's sleeping environment. Those methods are mostly hard to implement in practice due to these reasons. We propose a method to detect posture using a three-axis acceleration sensor from the wrist band. We developed a wearable watch that measures sleep-related data. We analyzed 40 people's sleep data with a wearable module and watch to measure their postures such as supine, left-side, and right-side. Then, we compared the classified posture from the watch with the wearable module and achieved 90% accuracy. Therefore, we concluded that only by using the wearable watch, we can detect the sleeping position without any new equipment or system to diagnose the patients without discomfort during their daily lives.

• BMB Reports
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• v.48 no.8
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• pp.467-472
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• 2015

Heat shock increases skin temperature during sun exposure and some evidence indicates that it may be involved in skin aging. The antioxidant response mediated by the transcription factor NF-E2-related factor 2 (Nrf2) is a critically important cellular defense mechanism that serves to limit skin aging. We investigated the effects of heat shock on collagenase expression when the antioxidant defense system was downregulated by knockdown of Nrf2. GSH and collagenases were analyzed, and the expression of inducible Nrf2, HO-1, and NQO1 was measured. HS68 cells were transfected with small interfering RNA against Nrf2. Heat shock induced the downregulation of Nrf2 in both the cytosol and nucleus and reduced the expression of HO-1, GSH, and NQO1. In addition, heat-exposed Nrf2-knockdown cells showed significantly increased levels of collagenase protein and decreased levels of procollagen. Our data suggest that Nrf2 plays an important role in protection against heat shock-induced collagen breakdown in skin. [BMB Reports 2015; 48(8): 467-472]

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.605-618
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• 2014

The effects of variability of the mechanical properties of lead rubber bearings on the response of a seismic isolation system are investigated. Material variability in manufacturing, aging, and operation temperature is assumed, and two variation models of an isolation system are considered. To evaluate the effect of ground motion characteristics on the response, 27 earthquake record sets with different peak A/V ratios were selected, and three components of ground motions were used for a seismic response analysis. The response in an isolation system and a superstructure increases significantly for ground motions with low A/V ratios. The variation in the mechanical properties of isolators results in a significant influence on the shear strains of the isolators and the acceleration response of the superstructure. The variation provisions in the ASCE-4 are reasonable, but more strict variation limits should be given to isolation systems subjected to ground motions having low A/V ratios. For application of seismic isolation systems to safety-related nuclear structures, the variation in the material and mechanical properties of the isolation system should be properly controlled during the manufacturing and aging processes. In addition, special consideration should be given to minimize the accidental torsion caused by the dissimilarity in the stiffness variations of the isolators.

• The Journal of the Convergence on Culture Technology
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• v.10 no.3
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• pp.845-849
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• 2024

Currently, rail surface defects are increasing due to the aging of urban railway rails, but in the detailed guidelines for track performance evaluation established by the country, rail surface damage is inspected with the naked eye of an engineer and with simple measuring tools. It is very important to discover defects in the rail surface through periodic track tours and visual inspection. However, evaluating the severity of defects on the rail surface based on the subjective judgment of the inspector has significant limitations in predicting damage inside the rail. In this study, the characteristics of cracks inside the rail due to rail surface damage were studied. In field measurements, rail surface damage was selected, old rail samples were collected in the acceleration and braking sections, and a scanning electron microscope (SEM) was used to evaluate the rail surface damage was used to analyze the crack characteristics. As a result of the analysis, the crack mechanism caused by the running train and the crack characteristics of the acceleration section where cracks occur at an angle rising toward the rail surface were experimentally proven.

• Biomolecules & Therapeutics
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• v.23 no.6
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• pp.582-589
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• 2015

Several theories emphasize that aging is closely related to oxidative stress and disease. The formation of excess ROS can lead to DNA damage and the acceleration of aging. Vigna angularis is one of the important medicinal plants in Korea. We isolated vitexin from V. angularis and elucidated the lifespan-extending effect of vitexin using the Caenorhabditis elegans model system. Vitexin showed potent lifespan extensive activity and it elevated the survival rates of nematodes against the stressful environments including heat and oxidative conditions. In addition, our results showed that vitexin was able to elevate antioxidant enzyme activities of worms and reduce intracellular ROS accumulation in a dose-dependent manner. These studies demonstrated that the increased stress tolerance of vitexin-mediated nematode could be attributed to increased expressions of stress resistance proteins such as superoxide dismutase (SOD-3) and heat shock protein (HSP-16.2). In this work, we also studied whether vitexin-mediated longevity activity was associated with aging-related factors such as progeny, food intake, growth and movement. The data revealed that these factors were not affected by vitexin treatment except movement. Vitexin treatment improved the body movement of aged nematode, suggesting vitexin affects healthspan as well as lifespan of nematode. These results suggest that vitexin might be a probable candidate which could extend the human lifespan.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1918-1920
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• 2004

본 고에서는 해남-제주간에 사용되는 Phase Control Thyristor의 구입비용을 고려하여, 해남-제주간 PCT와 동일 구조를 갖지만 전압/전류용량이 작은 A, B사의 PCT를 각각 40개씩 확보하였다. PCT의 가속열화를 위한 스트레스 인자는 전압/열이며, 이를 동시에 인가할 수 있도록 가속열화 시험장치를 구성하였다. 또한 가속열화에 의해 열화정도를 파악하기 위해 초기 특성을 측정하였으며, 이에 대한 결과를 기술하였다.