• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.11
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• pp.2704-2710
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• 1993

A simple and straightforward method is introduced for developing continuum beam-rod model of a box-beam typed aircraft wing with composite layered skin based on "energy equivalence." The equivalent continuum structral properties are obtained from the direct comparison of the reduced stiffness and mass matrices for box-beam typed wing with those for continuum beam-rod model. The stiffness and mass matrices are all represented in terms of the continuum degrees-of freedom defined in this paper. The finite-element method. The advantage of the present continuum method is to give every continuum structural properties including all possible coupling terms which represent the couplings between different deformations. To evaluate the continuum method developed in this paper, free vibration analyses for both continuum beam-rod and box-beam are conducted. Numerical tests show that the present continuum method gives very reliable structural and dynamic properties compared to the results by the conventional finite-element analysis. analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.699-705
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• 2015

Aircraft needs high lift-to-drag ratio and weight reduction of the structure for long endurance flight with a small power. Generally high aspect ratio wing is applied to HALE(High Altitude Long Endurance) aircraft. Also high modulus, and high strength CFRP(Carbon Fiber Reinforced Plastic) has been used in primary structures. and thin mylar(membrane material) film has been applied to skin of wing. As a result, wing is more flexible than the other structures. and the stiffness of thin mylar film has an affect on dynamic stability. In this study, the membrane characteristic of mylar film has been simulated using nonlinear gap elements. And equivalent modeling method using shell elements is presented using the nonlinear simulation result. The linear equivalent model has verified using the results of nonlinear membrane method. Proposed linear equivalent shell model has applied to mode analysis for estimate the effect of mylar mechanical properties on natural frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.853-856
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• 2004

This study presents a prediction method for sound insulation of sandwich plate which consists of orthotropic plates as skin and mineral wool as core. Prediction by classic theory, which considers orthotropic effects, requires considerably complex and cumbersome process and moreover many assumption. However, experimental results of the sandwich plate with orthotropic plates as skin show that the orthotropic effects are disappeared or fade out. Hence, predictions by using sandwich model are conducted by a simple modelling that substitutes an orthotropic plate into an equivalent flat plate. Comparative results show that sandwich model gives a good agreements with theoretical prediction.

• Proceedings of the SCSK Conference
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• 2003.09a
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• pp.387-412
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• 2003

Influence of gelatinase on basement membrane (BM) structure was investigated by using a skin equivalent (SE) model. The results showed that (1) gelatinase produced by cells degraded the BM and (2) the addition of matrix metalloproteinase-specific inhibitor to the SE medium accelerated the formation of BM structure, indicating that gelatinase is involved in BM impairment. The activity of gelatinase was also studied in healthy human facial skin tissues. The result of in situ zymography revealed gelatinase activity around the basal layer of the epidermis, where BM integrity was severely compromised. Therefore, this enzyme was suggested to be associated with BM decomposition in human facial skin. To assess the behavior of gelatinase in stratum corneum (SC) non-invasively, an immunological study was performed. Since positive immunostaining of pro-gelatinase B was observed in SC stripped from sun-exposed skin, whereas no positive staining detected in SC of non-irradiated skin, gelatinase in the epidermis could be non-invasively detected by measuring gelatinase in SC. Gelatinase in SC of healthy female volunteers was monitored using a special film that sensitively and conveniently detects gelatinase. Ninetr percent of SC from facial skin (l00 women, 40's-50's) was gelatinase-positive. On the other hand, SC from non-irradiated skin was negative. These results strongly suggest that (1) gelatinase is constantly produced in the facial epidermis of most middle-aged woman during their daily life, and (2) the enzyme might be involved in the aging-related degeneration of both BM and the matrix fibers of the upper layer of the dermis, acting as a very important aging factor. Strong inhibitory activity against gelatinase was found in turmeric extract and identified curcumin as the major ingredient. Topical application of cream containing turmeric extract significantly decreased the number of gelatinase-positive SC clusters in human facial skins. These results indicated that turmeric is an effective ingredient to prevent skin from photo aging by suppressing chlonically upregulated gelatinase activity by UV and to improve skin condition.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.3
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• pp.219-224
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• 2012

European Union prohibited the marketing of cosmetic products containing constituents that have been examined through animal experiments. Thus, non-animal test models are needed to replace animal experiments. The reconstructed skin models are important as a test system for cosmetic, pharmaceutical, and medical device safety testing. In the present study, we tried to develop an optimal skin equivalent model containing basement membrane and epidermis. For this purpose, we used mesenchymal stem cells (MSCs) and/or preadipocytes as well as fibroblasts as the dermal matrix cells. The formation of basement membrane and epidermis was verified by immunohistochemical stains. Among various models, the epidermis was thickest when MSCs were used in the dermal matrix. Furthermore, PCNA and involucrin distribution showed that dermal matrix with MSCs resembled human skin. Therefore, skin equivalents with MSCs could be developed as a non-animal test model to replace animal experiments.

• Journal of the Korea Convergence Society
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• v.8 no.2
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• pp.121-126
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• 2017

In this study, we measured the bioelectrical impedance of whole body in various frequency bands by non-invasive method by four electrode method using a portable small impedance measurement system developed to understand the bioimpedance characteristics of intracellular fluid and extracellular fluid components through a skin equivalent model. The measurements were performed on 10 male subjects (mean age $24{\pm}3.0$, body mass index(BMI) $20.3kg/m^2$) for four weeks and the bioimpedances were measured at multi-frequencies (1 kHz, 5 kHz, 50 kHz, 70 kHz, 100 kHz and 500 kHz). Experimental results show that the impedance is the highest in the low frequency range of 1 kHz and the lowest in the high frequency range of 500 MHz. Especially, it was confirmed through experiments that the impedance is rapidly lowered above 50 kHz band. In addition, it was confirmed that similar characteristics to the measured values of the bioimpedance measuring system were obtained in the simulations for understanding the impedance characteristics of the intracellular fluid and the extracellular fluid through the skin equivalent circuit model.

• Journal of Microbiology and Biotechnology
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• v.28 no.12
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• pp.2121-2132
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• 2018

Abnormal melanin synthesis results in several hyperpigmentary disorders such as freckles, melanoderma, age spots, and other related conditions. In this study, we investigated the anti-melanogenic effects of an extract from the microalgae Chlamydomonas reinhardtii (CE) and potential mechanisms responsible for its inhibitory effect in B16F10, normal human epidermal melanocyte cells, and human skin-equivalent models. The CE extract showed significant dose-dependent inhibitory effects on ${\alpha}$-melanocyte-stimulating, hormone-induced melanin synthesis in cells. Additionally, the CE extract exhibited suppressive effects on the mRNA and protein expression of microphthalmia-associated transcription factor, tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2. The CE extract also inhibited the phosphorylation of protein kinase A and extracellular signal-related kinase, which function as upstream regulators of melanogenesis. Using a three-dimensional, reconstructed pigmented epidermis model, the CE-mediated, anti-pigmentation effects were confirmed by Fontana-Masson staining and melanin content assays. Taken together, CE extract can be used as an anti-pigmentation agent.

• Natural Product Sciences
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• v.25 no.4
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• pp.341-347
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• 2019

Luffa cylindrica (LC) is a very fast-growing climber and its fruit have been considered as agricultural wastes. We conducted to check the comparative qualities of ethanol solvent extraction (LCE) and supercritical carbon dioxide extraction (LCS) of L. cylindrica fruit and seed. LCS had higher antioxidant and polyphenol contents than LCE. LCS were significantly increased peroxisome proliferator-activated receptor (PPAR)-a and involucrin expression as epidermal differentiation marker in 3D skin equivalent model. LCS also showed antimicrobial activity against Staphylococcus aureus, a causative bacteria in atopic dermatitis. In addition, LCS inhibited the adipocyte differentiation of 3T3-L1 cells. When treated with the extract at a concentration of 100 ㎍/mL, the Wnt/β-catenin pathway reporter luciferase activity of HEK 293-TOP cells was increased approximately by 2-folds compared to that of the untreated control group. These results indicate that L. cylindrica supercritical carbon dioxide extract may serve as a cosmeceutical for improving skin barrier function and the treatment of obesity.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.113-117
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• 2003

The recent development of methods for culturing hair follicles in vitro has proved an important tool to investigate many aspects of drug screening. Hair follicles develop as a result of epithelial-mesenchymal interactions between epidermal keratinocytes and dermal cells. We isolated some follicle cells using explantation and enzymatic digestion method from human scalp hair follicles. So we could culture some follicular cells, such as outer root sheath (ORS) cells, dermal papilla (DP) cells, dermal sheath (DS) cells, matrix cells and melanocytes. To induce hair morphogenesis in vitro the cells were 3-D cultured as skin structures. Moreover, to develop hair follicel organ culture model, we applied dermal equivalent (DE) to culturing hair follicles to expand hair growth period.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.5
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• pp.218-223
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• 2005

Impedance matching characteristics of planar type inductively coupled plasma sources are investigated utilizing the previously reported two-dimensional theory[1] of the anomalous skin effect. Two types of matching networks are considered, and the values of the circuit elements are expressed as functions of various reactor parameter. Also, two cases of perfect and imperfect matching conditions are considered and the functional dependence of the values of matching capacitance and reflection coefficient on the various reactor parameters are investigated using the present circuit model.