• Textile Coloration and Finishing
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• v.20 no.6
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• pp.8-17
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• 2008

Poly (vinyl acetate) (PVAc) was used as a precursor of PVA/PVAc (skin/core) bicomponent. In order to investigate the possibility of PVA particles for electrical applications, PVA/PVAc particles were produced with an emulsifier, SDS (Sodium Dodecyl Sulfate) and an initiator, V-50 (2,2'-azobis(2-amidinopropane)digydrochloride). In this study, we investigated the electrical property of PVA/PVAc (skin/core) particles. The hydroxyl group of the PVA/PVAc (skin./core) was confirmed by the analysis of PVAc and PVA/PVAc (skin/core) using Fourier Transform Infrared Spectroscopy (FT-IR). The zeta-potential of the PVA/PVAc (skin/core) and PVAc has similarity; however, charge control agent (CCA) treated PVA/PVAc (skin/core) particles has lower zeta-potential than untreated PVA/PVAc particles. The zeta-potential (negative values) of the PVA/PVAc (skin/core) were enhanced in proportion to the increased concentration of CCA.

• Journal of Microbiology and Biotechnology
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• v.32 no.2
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• pp.238-247
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• 2022

Since the skin covers most surfaces of the body, it is susceptible to damage, which can be fatal depending on the degree of injury to the skin because it defends against external attack and protects internal structures. Various types of artificial skin are being studied for transplantation to repair damaged skin, and recently, the production of replaceable skin using three-dimensional (3D) bioprinting technology has also been investigated. In this study, skin tissue was produced using a 3D bioprinter with human skin cell lines and cells extracted from mouse skin, and the printing conditions were optimized. Gelatin was used as a bioink, and fibrinogen and alginate were used for tissue hardening after printing. Printed skin tissue maintained a survival rate of 90% or more when cultured for 14 days. Culture conditions were established using 8 mM calcium chloride treatment and the skin tissue was exposed to air to optimize epidermal cell differentiation. The skin tissue was cultured for 14 days after differentiation induction by this optimized culture method, and immunofluorescent staining was performed using epidermal cell differentiation markers to investigate whether the epidermal cells had differentiated. After differentiation, loricrin, which is normally found in terminally differentiated epidermal cells, was observed in the cells at the tip of the epidermal layer, and cytokeratin 14 was expressed in the lower cells of the epidermis layer. Collectively, this study may provide optimized conditions for bioprinting and keratinization for three-dimensional skin production.

• Steel and Composite Structures
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• v.45 no.3
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• pp.467-482
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• 2022

One of the major failure modes in composite sandwich structures is the separation between skins and core. In this study, the effect of employing foam filled composite corrugated core on the skin/core debonding (resistance to separation between skin and core) is investigated both experimentally and numerically. To this aim, triangular corrugated core specimens are manufactured and compared with reference specimens only made of PVC foam core in terms of skin/core debonding under bending loading. The corrugated composite laminates are fabricated using the hand layup method. Also, the Vacuumed Infusion Process (VIP) is employed to join the skins to the core with greater quality. Utilizing an End Notched Shear (ENS) fixture, three point bending tests are performed on the manufactured sandwich composite panels. The results reveal that the resistance to separation capacity and flexural stiffness of sandwich composite has been increased about 170% and 76%, respectively by using a triangular corrugated core. The Cohesive Zone Model (CZM) with appropriate cohesive law in ABAQUS finite element software is used to model the progressive face/core interfaces debonding the difference between experimental and numerical results in predicting the maximum born load before the skin/core separation is about 6 % in simple core specimens and 3% in triangular corrugated core specimens.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.3101-3101
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• 2001

Near Infrared spectroscopy (NIR) used on human skin measurement was explored in the past decade. Many publications in different journals and magazines discussed the feasibility of the NIR technique for cosmetic product property studies. Based upon the results of pioneers, we have pursued some work of the NIR instrument coupled with a probe module for skin measurement in vivo and vitro. In part I of this paper, the specific Near Infrared spectroscopy instrument stability, human subject conditions and other parameters, which could affect the measurements reproducibility are discussed. Second derivative NIR spectra and Principle Components Analysis (PCA) are utilised for data interpretation. In part II of this paper, the relationship of human skin moisture and ageing, the gender information and finally, the discovery of penetration depth of NIR incident light on skin are reported. A theoretical penetration depth calculation equation is proposed. In part III, the study results of a couple of commercial skin care products effect will be described. The skin lotions were applied on human skin (in vivo) in order to exam the NIR feasibility to monitor the changes of moisture level. The results are consistently positive. From our primary study, it can conclude that the NIR is potentially a very powerful instrument for skin condition diagnostics, either for cosmetic and/or for medication purposes.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.159-167
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• 1999

Sandwich injection molding is one of the remarkable polymer processes recently developed from conventional injection molding. But it is almost impossible to do theoretical investigation that we've researched it through numerical simulation. In this paper, numerical simulation on the study of sandwich injection molding is based on Finite Element Method and FAN/Control Volume method. In addition to conventional filling parameter that can confirm skin polymer melt front, new filling parameters have been introduced to confirm core polymer melt front advancement. These filling parameters are defined in each layer which is divided to solve temperature field along the thickness direction. One can notice different filling patterns resulted from the variation of material properties such as viscosities and power-law indexes, and processing conditions such as switch-over times and wall temperatures. It gives us a better understanding of the sandwich injection molding process. And we can recognize that it's the core polymer spatial distribution after the completion of filling that is the most important key point to use this process for industrial molding process.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.93-102
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• 2013

An optimization work was developed in this work to provide design information for sandwich beam in civil engineering applications. This research is motivated by the wide-range applications of sandwich structures such as; slab, beam, girder, and railway sleeper. The design of a sandwich beam was conducted by using analytical and numerical optimization. Both analytical and numerical procedures consider the optimum design with structure mass objective minimization. Allowable deflection was considered as design constraints. It was found that the optimized core to the skins mass ratio is affected by the skin to core density and elastic modulus ratios. Finally, the optimum core to skin mass ratio cannot be constant for different skin and core materials.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.61-64
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• 2004

The strength characteristics as well as deformation behaviors of honeycomb sandwich composite (HSC) structures were investigated under bending in consideration of various failure modes such as skin layer yielding, interface-delamination, core shear deformation and local buckling. Deformation behaviors of honeycomb sandwich plates were observed with various types of aluminum honeycomb core and skin layer. Their finite-element analysis simulation with a real model of honeycomb core was performed to analyze stresses and deformation behaviors of honeycomb sandwich plates. Its results were very comparable to the experimental ones. Consequently, the increase in skin layer thickness and in cell size of honeycomb core had dominant effects on the strength and deformation behaviors of honeycomb sandwich composites.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1630-1635
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• 2005

The microstructure of the parts made by the microcellular injection molding process influence properties, including impact strength, tensile strength and density of material. Microstructure of microcellular plastics is divided into core foaming region and solid skin region. Core foaming region is influenced by pressure drop rate, viscosity and cell coalescence. However, actual mechanism of the skin layers is not known despite its importance. The study on the skin layer is getting important because foaming rate of the plastics is determined by the thickness ratio of the skin layer. Especially in case of large molded part, control of the skin layer is needed because skin layer thickness is changed largely. Therefore it is necessary to study variation in skin layer thickness with processing parameters. In this paper, the influence of temperatures in the mold cavity on the skin layer s thickness was also addressed. In addition, the relationship between the temperature distributions across cavity of the mold with impact strength on parts made with the microcellular injection molding process was addressed. In addition, the method to predict the variation in skin layer thickness with mold temperature is discussed.

• Composites Research
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• v.15 no.3
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• pp.45-51
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• 2002

Smart skin, a multi-layer structure of composed or different materials, was designed and fabricated. Tests and analyses are conducted to study the characteristics of its behavior under compression and bending loads. The designed smart skin failed due to premature buckling before compression failure. It was confirmed that shear moduli of honeycomb core affect structural stability of smart skin. A new test method and device were designed fur better measurement of shear moduli of honeycomb core. Numerical prediction of structural behavior of smart skin by NASTRAN agreed well with experimental data.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.25 no.4
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• pp.35-44
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• 2012

Objectives : This study was aimed to evaluate the treatment effect of psoriasis patient using pyretotherapy. Methods : The clinical study was performed using retrospective observational research method. Treatment method was pyretotherapy that optimized core temperature through herbs therapy, food therapy, excercise and life style change. In other aspects, pyretotherapy is skin cure therapy that rise core temperature, down skin temperature and open sweat gland. Results : 1. 40s years showed the most coming of clinic in the distribution of age of psoriasis patient. 2. Board type showed the most number in the classification of psoriasis. 3. Pyretotherapy was very effective results in psoriasis patient treatment. 4. Pyretotherapy showed effects of rising axillary temperature and moving facial high skin temperature toward abdominal portion. Conclusions : The author is able to say that it is possible for pyretotherapy to become new skin therapy for many skin disease, especially psoriasis.