• Journal of Hydrogen and New Energy
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• v.22 no.4
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• pp.488-494
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• 2011

Gasket plays an important role on sealing of the polymer electrolyte membrane fuel cell (PEMFC) stack. Stack requires gaskets in each cell to keep the hydrogen and air/oxygen within their respective regions. The failure of the gasket creates the problems of fuel leakage, mixing, damage on parts and can be a direct reason for the degrading the efficiency of fuel cell. The purpose of this paper researches on how mechanical properties of EPDM gasket in PEMFC are changed after long-term operations. The EPDM (ethylenepropylene-diene monomer) gaskets are obtained from the stack after long-term operations. DMA (dynamic mechanical analysis) is conducted to access the change of mechanical properties of the EPDM gasket. SEM/EDS (scanning electron microscope/energy dispersive spectroscopy) was used to show the surface topography and chemical characterization on the sample surface.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.168-172
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• 1999

We have studied the formation of Co/Ti bilayer silicide with low resistivity and good thermal stability on the heavily boron doped $\textrm{p}^{+}$-Si region. In this paper, Co/Ti bilayer silicides were fabricated by depositing Co($150\AA$)/Ti($50\AA$) films on the clean $\textrm{p}^{+}$-Si substrates in an E-beam evaporator and performing the two step RTA process (first annealing: 650$50^{\circ}C$/20sec, second annealing: $800^{\circ}C$/20sec) in a $N_2$ambient with the pressure of $\textrm{10}^{-1}$atm. Co/Ti bilayer silicides obtained from our experiments exhibited the low resistivity of about $18\mu\Omega$-cm and the uniform thickness of about $500\AA$ without change of sheet resistance and agglomeration under the long post0annealing time up to $1000^{\circ}C$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.629-630
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• 2017

Recently, the number of patients with habitual vertebrae is increasing due to inappropriate postures and habits while sitting on a chair for a long time, because modern people have a great deal of work and studying due to a lot of work and study. Therefore, it is necessary to prevent such a disease through real-time monitoring and to present a guide for the user to recognize the importance of correct posture. In this study, we implemented a posture discrimination system which can help users to calibrate posture by judging the user's sitting position and feedback by using a pressure sensor based weight distribution system. We analyzed the distribution pattern of body weight to determine one normal posture and six abnormal postures. If the abnormal posture is maintained constantly, the implementation of the application that induces the right posture by ringing the notification is described.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.369-372
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• 2021

These days, people spend more time sitting at a desk for studies or work. Also, because people continue to use computers, smartphones, and tablet PCs often during break times, their posture is getting worse. Maintaining a position of bad posture for an extended period of time causes problems with the musculoskeletal system related to the neck, shoulders, and spine. Additionally, problems such as physical fatigue and posture deformation are predicted to expand to a wide range of age groups. Therefore, the core function of the system we are developing is to ensure correct sitting posture and to receive alert notifications via the created mobile application. To create the system, a flex sensor, pressure sensor, and tilt sensor are attached to a chair and utilized. The flex sensor detects and compares the amount of bending in the chair's posture and transmits this value to an Arduino Uno R3 board. Additionally, information such as body balance and incline angle are collected to determine whether or not the current sitting posture is correct. When the posture is incorrect, a notification is sent through the mobile application to indicate to the user and the monitoring app that their posture is not correct. The system proposed in this study is expected to be of great help in future posture-related research.

• The Journal of the Convergence on Culture Technology
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• v.9 no.4
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• pp.239-243
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• 2023

Due to recent small unmanned aircraft threats by North Korea and unsuccessful reponses, severe concerns about future national security have been being increasingly surged. Especially it is notable and unaccpetable to see that North Korea's small drones flying over capical areas over 7 hours were not efficiently detected and identified even though South Korea already recognized the threats since early 2010s. Meanwhile a US military troop operating THAAD system on Seung-Joo, South Korea successfully shot down unidentified small drone on Jan 2023. The threats caused by small unmanned aircraft is worrisome not only to South Korea, but also to international nations. This paper surveyed US DoD Strategy for countering small aircraft systems and suggest how to improve our current anti-dron systems so that small unmanned aircraft threats will be dynamically diminished or neutralized as fast as we can.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.511-523
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• 1995

The elastic open activator is one of the modified myodynamic activator. The reduced size of the appliance mass motivates the patients' comfort and longer time of wearing. Its peculiarities in loose fitting and the lack of appliance stabilization in the mouth draws the tongue and the surrounding functional matrices on close interaction with the appliance, consigns the physiologic exertion to target structures, and eventually makes it feasible to the inland of non-extraction treatment In the context of the sagittal malocclusion, the orthodontic trench is dependent upon the growth of basal structure aimed, therefore, it is contemplated to grabble the effects of Elastic Open Activator upon the class II malocclusion of growing child retrospectively. The cephalometric headfilms and study models of nine Class II malocclusion of growing child retrospectively. The cephalometric headfilms and study models of nine class II division 1 and five division 2 patients were evaluated and analyzed, and the following observations were drawn, 1. The maxilla maintained a normal growth pattern in both groups. 2. The mandible grew anteroinferiorly in both groups. 3. The upper incisors tipped ligually in Class II division 1 and tipped labially in Class II division 2 and anterior vertical alveolar growth was interrupted in both groups. 4. The lower incisors tipped labially. 5. There was an arch expansion in both groups and increase of available space in Class II division 2

• Journal of Digital Convergence
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• v.11 no.11
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• pp.545-551
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• 2013

This study aimed to compare the effects of microcurrent stimulation and rest on the fatigue index by applying both to subjects who had accumulated fatigue after performing short-duration physical activity. The experiment was performed at S University from December 2012 to February 2013, on 22 healthy men in their 20s, who were right-handed, and without peripheral or musculoskeletal diseases. All subjects lifted a 10-kg box lift and lower 100 times in 15 minutes. Immediately after that, muscle fatigue index (Median Frequency: MF) and blood fatigue index (Creatine Kinase Lactate: CK, Lactate Dehydrogenase: LDH) were measured by using surface electromyography. The subjects were divided into two groups, and microcurrent stimulation and rest were mediated to the experimental and control groups, respectively, for 20 minutes. After intervention, muscle fatigue index and blood fatigue index were measured and the changes in the accumulated fatigue index were compared. Both groups manifested significantly decreased cumulative fatigue after applying the mediation compared to the pre-intervention level (p < .05), the only exception being the fatigue index of the left erector spinae in the rest group. Compared to the rest group, the microcurrent stimulation group showed a significant decrease in muscle fatigue index (p < .05) but no significant differences were found in the blood fatigue index. Given the results of this study, microcurrent stimulation is considered to be helpful in muscle fatigue recovery for workers who have to perform repetitive movements lifting weights, and additional studies on the correlations of the fatigue recovery with respect to the long-term follow-up of fatigue index and mediation time are necessary.

• Journal of the Korea Convergence Society
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• v.11 no.9
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• pp.277-285
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• 2020

The purpose of this study was to evaluate the effects of wearing Head-Mounted Display (HMD) on the cervical range of motion (CROM), neck muscle thickness, and pain in healthy young adults. The HMD group(male=16, female=7) was asked to perform sitting comfortably in a backless chair with hands on their knees with the HMD was worn on their heads to watch the video for 30 minutes. The control group(male=15, female=8) was asked to sit in the same posture as the HMD group for 30 minutes. CROM, neck muscle thickness, and pressure pain threshold (PPT) of both the upper trapezius and levator scapulae were measured before and after intervention. CROM and PPT of the upper trapezius and levator scapulae in the HMD group were significantly decreased and the thickness of the muscles in the HMD group were significantly increased more than in the pre-test (p<.05). There was no significant difference in CROM, muscle thickness, and PPT in the control group. Wearing HMD for a long time can cause a decrease in CROM and PPT and an increase in muscle thickness, and there is a risk of developing musculoskeletal disorders in the neck and shoulder. Therefore, this study recommends maintaining the correct posture of the neck and shoulder and using HMD only for an appropriate time.

• Journal of agricultural medicine and community health
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• v.30 no.3
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• pp.279-292
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• 2005

Objectives: The purpose of this study is to analyze agricultural accident and disease using statistical data and materials about National Survey for Health & Nutrition in 2001 and to provide fundamental materials for studies about farmers' health and safety, decision of priority about research and policy. Results: Diagnosed chronic disease prevalence is 72.4% in farmer/fisher group, 49.8% in non farmer/fisher group. The chronic disease prevalence of musculoskeletal disease, circulatory disease, and gastroenteric disease is 46.5%, 18.2%, and 17.9% in farmer/fisher group respectively. The prevalence of musculoskeletal disease in farmer/fisher is 2.4 times higher than non farmer/fisher. This result shows that it need to evaluation for risk factors of musculoskeletal disease preferentially. Lifetime accident/poisoning rate is 18.2% In farmer/fisher group and 13.3% in non farmer/fisher group. The types of accidents were fracture>sprain>contusion and the reasons of accidents were traffic accident>falling/sliding. Conclusions: "Bad or very bad" response of farmer/fisher is almost 2 times higher than non farmer/fisher group. The rate of smoking and no exercising in farmer/fisher group is higher than non farmer/fisher group.

• Journal of Preventive Medicine and Public Health
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• v.25 no.3 s.39
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• pp.247-268
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• 1992

This study was conducted to evaluate the effect of VDT work on eyes and vision among workers in a TV manufacturing plant. The study subjects consisted of 264 screen workers and 74 non-screen workers who were less than 40 years old male and had no history of opthalmic diseases such as corneal opacities, trauma, keratitis, etc and whose visual acuity on pre-employment health examination by Han's test chart was 1.0 or above. The screen workers were divided into two groups by actual time for screen work in a day : Group I, 60 workers, lesser than 4 hours a day and group II, 204 workers, more than 4 hours a day. From July to October 1992 a questionnaire was administered to all the study subjects for the general charateristics and subjective eye symptoms after which the opthalmologic tests such as visual acuity, spherical equivalent, lacrimal function, ocular pressure, slit lamp test, fundoscopy were conducted by one opthalmologist. The proportion of workers whose present visual acuity was decreased more than 0.15 in comparison with that on the pre-employment health examination by Han's test chart was 20.6% in Group II. 15.0% in Group I and 14.9% in non-screen workers. However, the differences in proportion were not statistically significant. The proportion of workers with decreased visual acuity was not associated with the age, working duration, use of magnifying glass and type of shift work (independent variables) in all of the three groups. However, screen workers working under poor illumination had a higher proportion of persons with decreased visual acuity than those working under adequate illumination (P<0.05) . The proportion of workers whose near vision was decreased was 27.5% in Group II, 18.3% in Group I, and 28.4% in non-screen workers and these differences in proportion were not statistically significant. Changes of near vision were not associated with 4 independent variables in all of the three groups. Six out of seven subjective eye symptoms except tearing were more common in Group I than in non-screen workers and more common in Group II than in Group I (P<0.01). Mean of the total scores for seven subjective symptoms of each worker(2 points for always, 1 point for sometimes, 0 point for never) was not significantly different between workers with decreased visual acuity and workers with no vision change. However, mean of the total scores for Group II was higher than those for the Group I and non-screen workers (P<0.01). Total eye symptom scores were significantly correlated with the grade of screen work, use of magnifying glass, and type of shift work. There was no independent variable which was correlated with the difference in visual acuity between the pre-employment health examination and the present state, the difference between far and near visions, lacrimal function, ocular pressure, and spherical equivalent. Multiple linear regression analysis for the subjective eye symptom scores revealed a positive linear relationship with actual time for screen work and shift work(P<0.01). In this study it was not observed that the VDT work decreased visual acuity but it induces subjective eye symptoms such as eye fatigue, blurred vision, ocular discomfort, etc. Maintenance of adequate illumination in the work place and control of excessive VDT work are recommended to prevent such eye symptoms.