• Bulletin of the Society of Naval Architects of Korea
• /
• v.23 no.1
• /
• pp.13-22
• /
• 1986

Axisymmetric turbulent thick boundary layers on a rotating body of revolution are calculated numerically in the paper. Richardson number is introduced to the mixing length to take account of swirl effects on Reynolds stresses. Interactions of the boundary layer and the external potential flow are included by adding the displacement thickness of boundary layers on the original body. Pressure distributions on the body surface are estimated by integrating normal momentum equation across the boundary layer. A model is designed and tested in the wind tunnel. Mean velocities are measured. Through the present study, swirl effects on the thick axisymmetric boundary layer development are considerable in comparison with those of non-totating cases. Rotational motion generally increase boundary layer thickness, axial skin friction coefficients, and form drags. Circumferential flow can be reversed to induce negative skin friction when the section area is reduced.

• Design & Manufacturing
• /
• v.10 no.3
• /
• pp.25-29
• /
• 2016

Recently, a hyaluronic acid micro needle patch for therapeutic and cosmetic purposes has been used by attaching directly to the skin with a pattern having a micro needle shape of 1/3 thickness of hair. These products are attracting attention as an innovative product that maximizes the effect by activating the active ingredient in the skin in the deep skin without blocking the horny layer because the micro needle shape exists on the patch surface so that it can penetrate effectively to the skin. Currently, DAB (droplet air blowing) or MEMS technology is used to make pattern shapes for patches. Because of this technology, manufacturing time is long and manufacturing cost is high, so we tried to develop the mold technology to machine the microneedle shape directly to the metal. In this study, we first fabricated a needle pattern with a quadrangular pyramid shape and finally produced a conical needle pattern.

• International Journal of Automotive Technology
• /
• v.7 no.4
• /
• pp.485-492
• /
• 2006

The AA5182/polypropylene/AA5182(AA/PP/AA) sandwich sheets have been developed for application to automotive body panels in future lightweight vehicles with significant weight reduction. It has been reported that the AA5182 aluminum sheet shows $L\"{u}ders$ band because of dissolved Mg atoms that cause fabrication process problem, especially surface roughness. The examination of serration behavior has been made after the tensile deformation of the AA/PP/AA sandwich sheets as well as that of the AA5182 aluminum skins at room and elevated temperatures. All sandwich sheets and the AA5182 aluminum skin showed serration behavior on their flow curves. However, the magnitude of serration was significantly diminished in the sandwich sheet with high volume fraction of the polypropylene core. According to the results of the analysis of the surface roughness following the tensile test, $L\"{u}ders$ band depth of the sandwich sheet evidently showed lower than that of the AA5182 aluminum skin. The strain rate sensitivity, m-value, of the AA5182 aluminum skin was -0.006. By attaching these skins to the polypropylene core, which has relatively large positive value of 0.050, m-value of the sandwich sheets changed to the positive value. The serration mechanism of the sandwich sheets was quantitatively investigated in the point of the effect on polypropylene thickness variation, that on the strain rate sensitivity and that on the localized stress state.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.6
• /
• pp.222-229
• /
• 2003

The purpose of this study is to evaluate the mechanical properties of 6061 Al foams, which were fabricated by P/M and multi-step induction heating method, and to build the database, which is needed for computer aided modeling or foam components design. Aluminium foams, consisting of solid aluminium and large quantities of porosities, is widely used in automotive, aerospace, naval as well as functional applications because of its high stiffness at very low density, high impact energy absorption, heat and fire resistance, and greater thermal stability than any organic material. In this study, 6061 Al foams were fabricated for variation of fraction of porosities (%) according to porosities (%)-final heating temperature ( $T_{a3}$) curves. Mechanical properties such as compressive strength, energy absorption capacity, and efficiency were investigated to evaluate the feasibility of foams as crash energy absorbing components. Moreover, effect of the surface skin thickness on plateau stress and strain sensitivity of the 6061 Al foams with low porosities (%) were studied.d.

• Applied Microscopy
• /
• v.52
• /
• pp.13.1-13.6
• /
• 2022

Microscopic structure of skin in two amphibious mudskipper fish; Boleophthalmus dussumieri Valenciennes, 1837 (B. dussumeri) and Periophthalmus waltoni Koumans, 1941 (P. waltoni) were investigated in relation to their lifestyle. The general structure of skin is the same among the two species. Epidermis in B. dussumeri was thicker significantly than P. waltoni. The dermal bulges were only well developed in the skin of B. dussumeri. Mucous cells were absent in the epidermis of P. waltoni but present in B. dussumeri. Both B. dussumeri and P. waltoni have well-developed swollen middle cells as a shared epidermal feature. The thickness of the middle cell layer of the epidermis in B. dussumeri was significantly greater than in P. waltoni. Capillaries in the dorsal and ventral parts of the body are more closely distributed to the epidermal surface in P. waltoni than in B. dussumeri. The diffusion distance in the dorsal epidermis of P. waltoni was less than that in the ventral epidermis of B. dussumeri. A comparative examination of the skin of mudskipper species suggests that, due to the more terrestrial lifestyle adopted by P. waltoni, the skin contributes more to respiration.

• Archives of Reconstructive Microsurgery
• /
• v.25 no.1
• /
• pp.15-18
• /
• 2016

Any types of burn injury that involve more than deep dermis often require reconstructive treatment. In gluteal region, V-Y fasciocutaneous advancement flap is frequently used to cover the defect. However, in case of large burn wounds, this kind of flap cannot provide adequate coverage because of the lack of normal surrounding tissues. We suggest V-Y adipofascial flap using the surrounding superficially damaged tissue. We present the case of a patient who was referred for full-thickness burn on gluteal region. We performed serial debridement and applied vacuum-assisted closure device to defective area as wound preparation for coverage. When healthy granulation tissue grew adequately, we covered the defect with surrounding V-Y adipofascial flap and the raw surface of the flap was then covered with split-thickness skin graft. We think the use of subcutaneous fat as an adipofascial flap to cover the deeper defect adjacent to the flap is an excellent alternative especially in huge defect with uneven depth varying from subcutaneous fat to bone exposure in terms of minimal donor site morbidity and reliability of the flap. Even if the flap was not intact, it was reuse of the adjacent tissue of the injured area, so it is relatively safe and applicable.

• The Research Journal of the Costume Culture
• /
• v.2 no.2
• /
• pp.385-394
• /
• 1994

Data of the body surface is a necessary unit for the measuring of metabolism energy and activity energy. And also, these data are referring to check the degree of retaining warmth of clothes, to find the effect of heat insulation according to body surface, to calculate an average temperature of skin, and to study the several fields of clothing. In measuring of body surface, it si actually impossible to measure a subject's body surface in each experiment. As the experimental method, both gypsum method, by which the shape of body an be copied as it is, and the weighting method from which planed body surface area can be measured with consistent thickness of polyprophylene film as used. In fact, every female subject feels uncomfortable to measure her body surface as a naked body. There, it is providing a simple, accurate regressive equation with weight & height as variable factors in this study. This equation is as=117.02W+77.31H-3344.94 with average error : 0.1%, absolute average error : 2.07%.

• Asian Pacific Journal of Cancer Prevention
• /
• v.17 no.1
• /
• pp.153-157
• /
• 2016

Background: In radiation therapy, estimation of surface doses is clinically important. This study aimed to obtain an analytical relationship to determine the skin surface dose, kerma and the depth of maximum dose, with energies of 6 and 18 megavoltage (MV). Materials and Methods: To obtain the dose on the surface of skin, using the relationship between dose and kerma and solving differential equations governing the two quantities, a general relationship of dose changes relative to the depth was obtained. By dosimetry all the standard square fields of $5cm{\times}5cm$ to $40cm{\times}40cm$, an equation similar to response to differential equations of the dose and kerma were fitted on the measurements for any field size and energy. Applying two conditions: a) equality of the area under dose distribution and kerma changes in versus depth in 6 and 18 MV, b) equality of the kerma and dose at $x=d_{max}$ and using these results, coefficients of the obtained analytical relationship were determined. By putting the depth of zero in the relation, amount of PDD and kerma on the surface of the skin, could be obtained. Results: Using the MATLAB software, an exponential binomial function with R-Square >0.9953 was determined for any field size and depth in two energy modes 6 and 18MV, the surface PDD and kerma was obtained and both of them increase due to the increase of the field, but they reduce due to increased energy and from the obtained relation, depth of maximum dose can be determined. Conclusions: Using this analytical formula, one can find the skin surface dose, kerma and thickness of the buildup region.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.295-299
• /
• 2006

The inner-structure bonded(ISB) sheet metal is defined as a composite sheet metal which has middle layer of truss-structure between two skin sheets. The characteristics such as ultra-light weight, high rigidity, high strength, etc are required especially for automobile parts. The characteristic of ISB sheet metal depends on inner-structure pattern or method of bonding. Pyramid type of crimped expanded metal is used for inner-structure and both of resistance welding and adhesive bonding are applied to make a specimen. As a result of compression test, it is appeared that forming limit is 10% reduction in thickness under a load of 8kgf per unit element(one inner-structure). In case of uniaxial tensile test the non-uniform surface integrity rather than the buckling of inner-structure happened at a load of 450kgf, which indicates elongation of 7.2% and thickness reduction of 13%. The eye-inspection method was applied to examine the defects occurring on the specimen during stretch forming. In case of biaxial stretch forming only the non-uniform deformation on the surface of a skin sheet could be observed. The forming limit in stretching of ISB sheet metal with the hemi-spherical punch of 150mm in diameter was 3mm in forming depth and 5% reduction in thickness.

• Archives of Reconstructive Microsurgery
• /
• v.10 no.2
• /
• pp.118-123
• /
• 2001

Introduction : We report advantages of distally based superficial sural artery flap in the soft tissue defect in lower leg, ankle and foot. They are easier and less complicated technique than others. Material & Method : Total 26 patients were operated and their soft tissue defect site were 10 cases of anterior tibial surface, 6 cases of Achilles tendon area, 3 cases of lateral and medial surface of tibia, 3 cases of foot dorsum surface, 3 cases of sole, 1 case of medial aspect of ankle. Average pedicle distance was 12.8 cm(range $8{\sim}21cm$) and follow up period was mean 18 months. Result : We obtained 24 cases of excellent and good results. The two cases were reported low complication rate, which were one case of skin necrosis covered full thickness skin graft, and the other case of infection. Conclusion : The advantage of distally based superficial sural artery flap in soft tissue defect are long distant pedicle, short operation time, easy elevation of pedicle, constant and reliable blood supply and good cosmetic result with thin-thickness flap.