• Smart Structures and Systems
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• v.29 no.4
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• pp.641-652
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• 2022

High-rise structures prone to large vibrations under the action of strong winds, resulting in fatigue damage of the structural components and the foundation. A novel compound damping cable system (CDCS) is proposed to suppress the excessive vibrations. CDCS uses tailored double cable system with increased tensile stiffness as the connecting device, and makes use of the relative motion between the high-rise structure and the ground to drive the damper to move back-and-forth, dissipating the vibration mechanical energy of the high-rise structure so as to decaying the excessive vibration. Firstly, a third-order differential equation for the free vibration of high-rise structure with CDCS is established, and its closed form solution is obtained by the root formulas of cubic equation (Shengjin's formulas). Secondly, the analytical solution is validated by a laboratory model experiment. Thirdly, parametric analysis is conducted to investigate how the parameters affect the vibration control performance. Finally, the dynamic responses of the high-rise structure with CDCS under harmonic and stochastic excitations are calculated and its vibration mitigation performance is further evaluated. The results show that the CDCS can provide a large equivalent additional damping ratio for the vibrating structures, thus suppressing the excessive vibration effectively. It is anticipated that the CDCS can be used as a good alternative energy dissipation system for vibration control of high-rise structures.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.823-829
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• 2022

This study considered the experimental parameters (Nano-graphene oxide reinforced polycarbonate, GFRP) under low-velocity impact load and vibration analysis. The effect of nano-graphene oxide (NGO) on a polycarbonate-based composite was studied. Two test procedures were adopted to obtain experimental results, vibration analysis. The mechanical tests were performed on damaged and non-damaged specimens to determine the damaging effect on the composite specimens. After the test was carried out, the effect of NGO was measured and damping factors were ascertained experimentally. 0. 2 wt% NGO was determined as the optimum amount that best affected the Vibration Analysis. The experiments revealed that the composite's damping properties were increased by adding the nanoparticles to 0.25 wt% and decreased slightly for the specimens with the highest nanoparticles content. Cyclic sinus loading was applied at a frequency of 3.5 Hz. This paper study the frequency effect of 3.5khz frequency damage on mechanical results. Found that high frequency will worthlessly affect the fatigue life in NGO/polycarbonate composite. In 3.5 Hz frequency, it was chosen to decrease the heat by frequency. Transmission electron microscopy (TEM) micrographs were used to investigate the distribution of NGO on the polycarbonate matrix and revealed a homogeneous mixture of nano-composites and strong bonding between NGO and the polycarbonate which increased the damping properties and decreased vibration. Finally, experimental modal analysis was conducted after the high-velocity impact damage process to investigate the defect on the NGO polycarbonate composites.

• Journal of the Korean Society for Heat Treatment
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• v.36 no.3
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• pp.145-152
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• 2023

β titanium alloys containing β stabilizing elements such as V, Nb, Ta, Mo and Fe are widely used etc, due to their excellent specific strength, corrosion resistance, fatigue strength and easy formability. New metastable β titanium alloys are developed containing low-cost elements (Mo and Fe) in this study. Fe element is a strong β-stabilizer which can affect the mechanical and electrochemical properties of Ti-5Mo-xFe (x = 1, 4 wt%) alloys. These properties were analyzed in connection with microstructure and phase distribution. Ti-5Mo-4Fe alloy showed higher compression yield stress and maximum stress than Ti-5Mo-1Fe alloy due to solid-solution hardening and grain refinement hardening effect. As Fe element increased, Fe oxide formation and reduction of ${\bar{Bo}}$ (bond order) value affect the decrease of corrosion resistance. Ti-5Mo-xFe alloys were more excellent than Ti-6Al-4V ELI alloy.

• Food Science and Preservation
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• v.30 no.4
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• pp.663-668
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• 2023

Ginseng root is a medicinal plant widely used in Korea for its immunity enhancing and anti-fatigue properties. However, its bitter taste has a negative impact on the expansion of the ginseng market. In this study, we determined the bitter tasting compounds of ginseng using an electronic tongue. The results of measuring bitterness showed that phenolic compounds and polyacetylenes of ginseng had low bitterness. On the other hand, the bitterness was strong in ginsenosides and alkaloids of ginseng. Among them, the bitterness of ginseng was higher in ginsenosides than in alkaloids. Theses results suggest that ginsenosides have a significant affect on the bitter taste of ginseng.

• Fashion & Textile Research Journal
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• v.26 no.2
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• pp.190-197
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• 2024

With increasing global interest in environmentally friendly materials and the consequent rise in demand, there is a growing need for alternatives to synthetic fibers, which can cause skin diseases and other side effects. The fashion industry is emphasizing material sustainability owing to concerns about increasing carbon emissions. Moreover, consumers express a strong desire for ecofriendly and sustainable materials. Therefore, clothing brand companies are developing eco-friendly products to enhance their corporate image. Hemp fibers are recognized for their functionality and are utilized as crucial materials in the development of eco-friendly products by global fashion companies. In this study, we produced socks that effectively improve foot health using hemp stem bark extract fibers and demonstrated the positive efficacy of natural fibers through functional and wearability evaluations. Hemp stem bark extract fibers showed 99.9% antimicrobial effectiveness against bacteria responsible for sweat-induced bacterial proliferation and odor, when blended with lyocell fibers and woven into fabric to manufacture socks. Wearability evaluations of these terry cloth socks confirmed a reduction in foot odor and fatigue among the participants with a consumer satisfaction of 4.63/5. These findings confirm the effectiveness and positive impact of the natural antimicrobial properties of hemp fibers and terry cloth structure in improving foot health.

• Journal of Oral Medicine and Pain
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• v.26 no.2
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• pp.107-114
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• 2001

Oral malodor is a problem that traverses history, culture, race and sex. But, up to the present the study on prevalence of oral malodor in normal popualtion is short, especially there is no study on oral malodor prevalence in Korean. In our study, we investigated self-evaluation of oral malodor, self-rating intensity of oral malodor, patients efforts for curing their oral malodor, and degree of satisfaction with their efforts. Investigation was carried out on 368 public Koreans resident in a big city(174 males, 194 females), by method of self-reporting to prepared questionnaire. There was no difference in self-reporting prevalence of oral malodor in sexes(57.5% in male, 58.8% in female), and the prevalence rate was increased with aging. Self-rating intensity of oral malodor in oral malodor patients group(by self-reporting) was ranked in order of slight, weak, middle, strong in both sexes, but the number of self-rating strong female group is significantly larger than that of self-rating strong male group(9.3% in male, 17.9% in female). In question on duration of oral malodor, most subjects answered that their oral malodor was developed in certain circumstances(61.3% in male, 76.3% in female), and oral malodor-developing circumstances was ranked in order of in the early morning, in hunger state, in fatigue, in stressful situations. Subjects effort for curing their oral malodor was ranked in order of more tooth brushing, gum chewing, use of commercial product for oral hygiene, visit dental clinic, and rates of no effort subjects were 15.3% in males and 10.7% in females. The degree of satisfaction with their efforts for curing their oral malodor was very low, only 5.6% of males and 6.6% of females were answered that there were satisfactory improvement in their oral malodor. Collectively, our result revealed that prevalence of oral malodor in public Koreans and their interest in oral malodor were much higher than our anticipation, and that patients satisfaction with improvement in oral malodor was short of their expectations. Considering the life quality of patients suffering from oral malodor, we conclude that developments of more improved diagnostic tools and treatment methods for oral malodor is indispensable in future.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.145-155
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• 2002

The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.3
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• pp.30-39
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• 2012

In this paper, a safe driving assistance system is proposed by detecting the status of driver's doze based on face and eye detection. By the level of the fatigue, safe driving system alarms or set the seatbelt on vibration. To reduce the effect of backward light and too strong solar light which cause a decrease of face and eye detection rate and false fatigue detection, post processing techniques like image equalization are used. Haar transform and PCA are used for face detection. By using the statistic of the face and eye structural ratio of normal Koreans, we can reduce the eye candidate area in the face, which results in reduction of the computational load. We also propose a new eye status detection algorithm based on Hough transform and eye width-height ratio, which are used to detect eye's blinking status which decides doze level by measuring the blinking period. The system alarms and operates seatbelt on vibration through controller area network(CAN) when the driver's doze level is detected. In this paper, four algorithms are implemented and proposed algorithm is made based on the probability model and we achieves 84.88% of correct detection rate through indoor and in-car environment experiments. And also we achieves 69.81% of detection rate which is better result than that of other algorithms using IR camera.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.487-493
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• 2017

The main purpose of this study is to evaluate the main parameters involved in the asphalt pavement distresses, including IRI (International Rough Index), fatigue, and permanent deformation. The main parameters are the region (Seoul and Busan), traffic level, asphalt binder, maximum aggregate of surface course, thickness of the surface course and base. A total of 64 case studies were carried out under the auspices of the KPRP (Korea Pavement Research Program). From the analysis of the KPRP test results, the key factors for the asphalt pavement distress were determined. Considering the effect of one variable in the basic condition, asphalt binder was the major factor having an effect on the distresses for an AADT (Annual Average Daily Traffic) of 5000 in the Seoul area. Among the remaining factors, the results were found to be in the order of the base layer thickness (A), surface layer thickness (B), and aggregate particle size thickness (D). The same results were obtained for an AADT of 10000. In the case of Busan with an AADT of 5000, the same result was obtained as for Seoul. Among the remaining factors, the results were in the order of the base layer thickness (A), aggregate particle thickness (D), and surface layer thickness (B). Even though there was a slight difference in the effect of the traffic level and region, asphalt binder was the parameter having the greatest effect on the asphalt pavement distress. In the case where the effect of multiple parameters was analyzed, the combination of the asphalt binder and base thickness showed a relatively strong effect.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.135-142
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• 2015

Human-powered self-generating devices have been attractive with its operation characteristic independent from outer environment such as weather condition and wind speed. However, conventional self-generators have low electric power output due to their weakly-coupled electromagnetic structure. More importantly, rotary crank motion which is usually adopted by conventional self-generator to generate electricity requires specific skeletal muscles to maintain large torque circular motion and consequently, causes fatigue on those muscles before it can generate enough amount of electricity for any practical application. Without improvement in electric power output and usability, the human-powered self-generator could not be used in everyday life. This study aims to develop a human-powered self-generator which realized a strong electromagnetic coupling in a closed-loop tubular structure (hula-hoop shape) for easy and steady long-term driving as well as larger electric output. The performance and usability of the developed human-powered generator is verified through experimental comparison with a commercial one. Additionally, human workload which is a key element of a human-powered generator but not often considered elsewhere, is estimated based on metabolic energy expenditure measured respiratory gas analyzer. Further study will focus on output and portability enhancement, which can contribute to the continuous power supply of mobile equipments.