• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.362-369
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• 2000

Via screw theory, a vibration mode can be geometrically interpreted as a pure rotation about the vibration center in a plane and as a twisting motion on a screw in a three dimensional space. In thi s paper, applying the conditions that can be used to diagonalize the stiffness matrix by a parallel axis congruence transformation, the vibration modes and frequency response of an elastically suspended optical disc drive have been analyzed. It is first shown that the system has one plane of symmetry, which enables one to decouple the complicated vibration modes into two sets of modes independent of each other. Having obtained the analytical solutions for the axes of vibrations, the frequency response for a given applied input force has been demonstrated. Most importantly, it has been explained that this research result could be used in the synthesis process of a linear vibration system in order to improve the frequency response.

• Textile Coloration and Finishing
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• v.34 no.4
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• pp.250-260
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• 2022

In this research, a high-elasticity acrylic emulsion binder with core-shell polymerization and self-crosslinking system is mixed with a flame-retardant water-dispersed polyurethane (PUD) binder. In addition, finite element analysis was conducted through virtual engineering software ANSYS by applying three representative nonlinear material models. The most suitable nonlinear material model was selected after the relative comparison between the actual experimental values and the predicted values of the properties derived from simulations. The selected nonlinear material model is intended to be used as a nonlinear material model for computational simulation analysis that simulates the experimental environment of the vibration test (ASTM E1399) and the actual fire safety test (ASTM E1966). When the mass fraction of thermally expandable graphite was 0.7%, the thermal and physical properties were the best. Among the nonlinear material models, the simulation result of the Ogden model showed the closest value to the actual result.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.3
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• pp.259-266
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• 2018

In today's society, where people look younger than their chronological age due to improvements in the quality of life, there is a gaining interest in anti-aging and how people compare to those in the same age group. We evaluated the wrinkle index, which is the most important attribute amongst skin parameters, to evaluate external age (wrinkle age). The wrinkles of the whole face were scored by divided 8 areas (forehead, glabella, nasal root, upper eyelid, lower eyelid, crow's feet, nasolabial groove and perioral skin) and analyzed the correlation between chronological age and skin parameters. 206 subjects (Korean female, n = 105 and Mongolians female, n = 101) were enrolled. Subjects were divided into four groups by ages: 20s, 30s, 40s, and 50s. Wrinkle scores of 8 areas were evaluated and developed a calculation formula based on the wrinkle scores. Skin characteristic parameters were measured about skin elasticity, pore, wrinkle, sebum secretion. There was no difference between the calculated ages and the chronological ages in Korean women. On the other hand, Mongolian looked older than chronological age by 9 years. The correlation between the facial wrinkle ages and skin physiology parameters was presented in the order of skin elasticity > pore or crow's feet > skin tone > sebum secretion in both countries. Skin elasticity represented the most related parameter with the facial wrinkle ages. This study identified the skin wrinkle patterns of Korean and Mongolian women and the wrinkle age calculation formula developed from this study can be used as a tool for calculating the facial wrinkle ages in cosmetic studies.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.2
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• pp.161-170
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• 2018

Skin aging degree can be objectively measured using the instrumental analysis. The purpose of this study was to evaluate the anti-aging effects of a cream containing 8000 PPM of resveratryl triacetate (RTA) in the human skin test. Twenty female subjects were given test products twice a day for 8 weeks on the face, and wrinkles, sagging, elasticity, dermis denseness, moisture and brightness were measured every 4 weeks by instrument analysis. After 4 and 8 week-use of the test product, total wrinkle area decreased (5.12%, 4.86%), total wrinkle volume decreased (10.53%, 8.41%), sagging decreased (4.69%, 5.91%), elasticity increased (2.84%, 3.98%), dermis denseness increased (15.65%, 20.80%), water content increased (5.83%, 7.37%), lightness ($L^*$ value) increased (0.79%, 1.07%), and individual typology angle ($ITA^{\circ}$) increased (5.43%, 4.95%)compared with the baseline values before treatments, and all these changes were statistically significant (p < 0.05). No adverse skin reactions were observed in all participants during the study period. This study supports the anti-aging effects of the test product.

• Journal of Ginseng Research
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• v.44 no.5
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• pp.738-746
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• 2020

Background: Red ginseng contains components, including microelements, vitamins, essential oils, and fatty acids, that can be used in skincare to delay the aging process. We investigated the effects of red ginseng treatment on skin elasticity by assessing cellular stiffness and measuring collagen protein synthesis. Methods: Human dermal fibroblasts were treated with red ginseng, and the resulting changes in stiffness were investigated using atomic force microscopy. Cytoskeletal changes and mRNA expression of biomarkers of aging, including that of procollagens I and VII, elastin, and fibrillin-1, were investigated. Collagen in a human skin equivalent treated with red ginseng was visualized via hematoxylin and eosin staining, scanning electron microscopy, and atomic force microscopy. Results and conclusion: The stiffness of fibroblasts was significantly reduced by treatment with red ginseng concentrations of ≥ 0.8 mg/mL. The ratio of F-actin to G-actin decreased after treatment, which corresponded to a change in fibroblast stiffness. The storage modulus (G') and loss modulus (G'') of the skin equivalent were both lowered by red ginseng treatment. This result indicates that the viscoelasticity of the skin equivalent can be restored by red ginseng treatment.

• The Research Journal of the Costume Culture
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• v.28 no.5
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• pp.705-718
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• 2020

The goal of this study was to develop a haptic communication system that can convey the tactile sensation of fashion materials in a virtual environment. In addition, the effectiveness and how realistically the virtual fabric image of this system delivers the tactile sensation of actual fabric was verified. First, a literature review was conducted through which the tactile attributes of fashion materials were defined that would be implemented in the haptic communication system. Then, a questionnaire for evaluating the tactile attributes of fashion materials was developed. Next, a haptic communication system was designed to convey fashion image experiences in a virtual environment, from which a haptic rendering model was suggested. The effectiveness of the haptic communication system was evaluated by verifying user experiences with questions developed through a user evaluation experiment. The validity of the evaluation questions pertaining to the tactile attributes and the effects of the haptic communication system were verified. Factor analysis was conducted to verify the evaluation of the tactile sense attributes of the fashion material, which identified density, thickness, and elasticity of the material as key factors. As a result of comparisons between the tactile sense through haptic characteristics and through touching, it was observed that regarding density and thickness, tactile sense experience led to greater perceived reality, while this was not the case for elasticity.

• Medical Lasers
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• v.10 no.3
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• pp.161-169
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• 2021

Background and Objectives Fractional microneedle radiofrequency systems are popular options to increase elasticity in aging skin. Laser-assisted drug delivery is a promising method for the epidermal injection of topically applied drugs and cosmetic ingredients. This study assesses the safety and efficacy of topical delivery of L-ascorbic acid, vitamin E, and ferulic acid after fractional microneedle radiofrequency treatment for reducing photodamage. Materials and Methods In this prospective, single-center, split-face, controlled pilot study, six women (mean age, 48.0 years; range, 35-57 years; Fitzpatrick skin types III and IV) exhibiting mild to moderate photodamage, underwent a single session of fractional microneedle radiofrequency treatment. The patients were instructed to apply the antioxidant formulation to only one side of the face. Patients were evaluated 3 days, 7 days, and 4 weeks thereafter, using three-dimensional imaging and ultrasound. Ex vivo, the full-thickness human skin was used for molecular and histological evaluation. Statistical analysis was achieved by applying t-tests, Mann-Whitney U tests, and one-way analyses of variance. Results Compared to the untreated side, the antioxidant-treated side exhibited a significant increase in dermal thickness (10.32% vs. 17.54%, p < 0.05), but not in skin elasticity (4.76% vs. 4.69%, p > 0.05). The difference in erythema between the sides was statistically not significant (p > 0.05). In the ex vivo model, expression of FGF2 in the skin was significantly increased after application of the antioxidant formulation, as compared to results obtained subsequent to fractional microneedle radiofrequency treatment only (p < 0.01). Conclusion This study demonstrates that for the treatment of photodamaged skin, laser-assisted delivery of the antioxidant formulation is a safe and effective adjuvant modality following fractional microneedle radiofrequency.

• Journal of the Korean Wood Science and Technology
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• v.51 no.4
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• pp.253-269
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• 2023

Oriented strand board (OSB) distributed in Korea was collected, and its mechanical properties were investigated according to the International Organization for Standardization (ISO), Japanese Industrial Standards, and Korean Design Standard. Ten types of OSBs were collected, including six types for walls and others for floors. The thickness swelling, moisture content, and density of each product satisfied the ISO standards. All products showed lower formaldehyde emission values than those of the SE0 grade. The internal bonding strengths of all products, except products B, H, and I, met the ISO standards. However, products A, B, C, F, and H did not satisfy the thickness swelling standard of the load-bearing OSB for use in dry conditions. Products D and G showed heavy duty load-bearing OSB for use in humid conditions in terms of internal bonding and bending strength after boiling. In the nail head pull-through force and lateral nail resistance tests, all products met the standards. In terms of the structural bending performance (four points), the six types of OSBs for walls satisfied the standard for bending strength and modulus of elasticity. All the products for flooring met the standard for bending strength but, except for product G, the products did not meet the standard for modulus of elasticity. Although the results of this study cannot represent the performance of all imported OSBs, considering the above results, the water resistance performance of seven types of OSB products did not meet the standard, and 10 types of products did not match the labeling grades.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.1-10
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• 2022

In this paper, the spatial randomness and probability characteristics of material properties are inversely estimated by using a set of the stochastic fields for the material properties of geotechnical structures. By using the probability distribution and probability characteristics of these estimated material properties, topology optimization is performed on structure shape, and the results are compared with the existing deterministic topology optimization results. A set of stochastic fields for material properties is generated, and the spatial randomness of material properties in each field is simulated. The probability distribution and probability characteristics of actual material properties are estimated using the partial values of material properties in each stochastic field. The probability characteristics of the estimated actual material properties are compared with those of the stochastic field set. Also, response variability of the ground structure having a modulus of elasticity with randomness is compared with response variability of the ground structure having a modulus of elasticity without randomness. Therefore, the quantified stochastic topology optimization result can be obtained with considering the spatial randomness of actual material properties.

• Advances in nano research
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• v.16 no.3
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• pp.231-249
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• 2024

When the amplitude of the vibrations is equivalent to that clearance, the vibrations for small amplitudes will really be significantly nonlinear. Nonlinearities will not be significant for amplitudes that are rather modest. Finally, nonlinearities will become crucial once again for big amplitudes. Therefore, the concrete panel system may experience a big amplitude in this work as a result of the high temperature. Based on the 3D modeling of the shell theory, the current work shows the influences of the von Kármán strain-displacement kinematic nonlinearity on the constitutive laws of the structure. The system's governing Equations in the nonlinear form are solved using Kronecker and Hadamard products, the discretization of Equations on the space domain, and Duffing-type Equations. Thermo-elasticity Equations. are used to represent the system's temperature. The harmonic solution technique for the displacement domain and the multiple-scale approach for the time domain are both covered in the section on solution procedures for solving nonlinear Equations. An effective data-driven solution is often utilized to predict how different systems would behave. The number of hidden layers and the learning rate are two hyperparameters for the network that are often chosen manually when required. Additionally, the data-driven method is offered for addressing the nonlinear vibration issue in order to reduce the computing cost of the current study. The conclusions of the present study may be validated by contrasting them with those of data-driven solutions and other published articles. The findings show that certain physical and geometrical characteristics have a significant effect on the existing concrete panel structure's susceptibility to temperature change and GPL weight fraction. For building construction industries, several useful recommendations for improving the thermo-mechanics' behavior of structural concrete panels are presented.