• Korea-Australia Rheology Journal
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• v.17 no.4
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• pp.191-198
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• 2005

The static and dynamic rheological behavior of concentrated sodium dodecylsulfate (SDS) stabilized, deformability controllable polydimethylsiloxane (PDMS) emulsions is reported and comparisons made with silica (hard sphere) suspensions. Steady-mode measurements indicate 'hard' (viscoelastic) droplets behave as hard spheres, while 'soft' (viscous) droplets induce structural flexibility of the emulsion against shear. Dynamic-mode measurements reveal that viscoelasticity of droplets provides the great magnitude of elasticity for the 'hard' emulsion, while formation of planar films between droplets is the origin of the elasticity of 'soft' emulsions. Combination of steady and dynamic rheological behavior has enabled depiction of droplet structure evolution in relation to the shear stress applied, especially by taking advantage of the normal force that reflects the transient deformation of droplets.

• Biomolecules & Therapeutics
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• v.25 no.5
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• pp.528-534
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• 2017

Placenta is a special organ that contains many nutrients such as growth factors, minerals, and bioactive peptides. Dipeptides of glycine and leucine are major components of porcine placenta extracts (PPE) that has been used as an alternative of human placenta extracts. In this study, we investigated whether major peptides of PPE, Glycyl-L-Leucine (Gly-Leu), L-Leucyl-Glycine (Leu-Gly), and L-Leucyl-L-Leucine (Leu-Leu), affect skin hydration and elasticity in vitro and in vivo. We found that Gly-Leu and Leu-Gly dipeptides induced the expression of transglutaminase 1 in normal human epidermal keratinocytes (NHEKs) whereas Leu-Leu dipeptides did not. Treatment with Gly-Leu or Leu-Gly significantly increased hyaluronan (HA) synthesis in NHEKs and the upregulation of hyaluronan synthase 2 (HAS2) mRNA level was confirmed. In addition, elastase activity was inhibited in NHEKs treated with Gly-Leu or Leu-Gly dipeptides. Oral administration of Gly-Leu or Leu-Gly dipeptides increased skin hydration and elasticity in UVB-irradiated hairless mice. The significant upregulation of HA in UVB-irradiated hairless mice was observed in response to oral administration of Gly-Leu or Leu-Gly. These results suggest that the major dipeptides of porcine placenta, Gly-Leu and Leu-Gly, are potentially active ingredients for skin moisturization formulations.

• Archives of Plastic Surgery
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• v.41 no.4
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• pp.330-336
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• 2014

Background For patients with full thickness skin defects, autologous Split-thickness skin grafts (STSG) are generally regarded as the mainstay of treatment. However, skin grafts have some limitations, including undesirable outcomes resulting from scars, poor elasticity, and limitations in joint movement due to contractures. In this study, we present outcomes of Matriderm grafts used for various skin tissue defects whether it improves on these drawbacks. Methods From January 2010 to March 2012, a retrospective review of patients who had undergone autologous STSG with Matriderm was performed. We assessed graft survival to evaluate the effectiveness of Matriderm. We also evaluated skin quality using a Cutometer, Corneometer, Tewameter, or Mexameter, approximately 12 months after surgery. Results A total of 31 patients underwent STSG with Matriderm during the study period. The success rate of skin grafting was 96.7%. The elasticity value of the portion on which Matriderm was applied was 0.765 (range, 0.635-0.800), the value of the trans-epidermal water loss (TEWL) was 10.0 (range, 8.15-11.00)$g/hr/m^2$, and the humidification value was 24.0 (range, 15.5-30.0). The levels of erythema and melanin were 352.0 arbitrary unit (AU) (range, 299.25-402.75 AU) and 211.0 AU (range, 158.25-297.00 AU), respectively. When comparing the values of elasticity and TEWL of the skin treated with Matriderm to the values of the surrounding skin, there was no statistically significant difference between the groups. Conclusions The results of this study demonstrate that a dermal substitute (Matriderm) with STSG was adopted stably and with minimal complications. Furthermore, comparing Matriderm grafted skin to normal skin using Cutometer, Matriderm proved valuable in restoring skin elasticity and the skin barrier.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.577-582
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• 2007

A variational formulation for plane elasticity problems is derived based on an isogeometric approach. The isogeometric analysis is an emerging methodology such that the basis functions in analysis domain arc generated directly from NURBS (Non-Uniform Rational B-Splines) geometry. Thus. the solution space can be represented in terms of the same functions to represent the geometry. The coefficients of basis functions or the control variables play the role of degrees-of-freedom. Furthermore, due to h-. p-, and k-refinement schemes, the high order geometric features can be described exactly and easily without tedious re-meshing process. The isogeometric sensitivity analysis method enables us to analyze arbitrarily shaped structures without re-meshing. Also, it provides a precise construction method of finite element model to exactly represent geometry using B-spline base functions in CAD geometric modeling. To obtain precise shape sensitivity, the normal and curvature of boundary should be taken into account in the shape sensitivity expressions. However, in conventional finite element methods, the normal information is inaccurate and the curvature is generally missing due to the use of linear interpolation functions. A continuum-based adjoint sensitivity analysis method using the isogeometric approach is derived for the plane elasticity problems. The conventional shape optimization using the finite element method has some difficulties in the parameterization of boundary. In isogeometric analysis, however, the geometric properties arc already embedded in the B-spline shape functions and control points. The perturbation of control points in isogeometric analysis automatically results in shape changes. Using the conventional finite clement method, the inter-element continuity of the design space is not guaranteed so that the normal vector and curvature arc not accurate enough. On tile other hand, in isogeometric analysis, these values arc continuous over the whole design space so that accurate shape sensitivity can be obtained. Through numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.271-276
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• 1999

This study is performed to evaluate an elastic properties and acid-resistance of concrete using pine needle ash(PNA). Materials used for this experiment are PNA , normal portland cement, natural fine and coarse aggregate. Test results show that the highest ultrasonic pulse velocity , dynamic and static modulus of elasticity is achieved by 5% PNA filled PNA concrete, which has showed similar with those of thei normal cement concrete. Acid-resistance of PNA concrete is increased with increase of the contnet of PNA , it is 1.29 times of the normal cement concrete by 5% PNA fille PNA concrete an d2.57 times by 15% PNA filled PNA concrete . Accordingly , PNA concrete wil greatly improve the properties of concrete.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.4
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• pp.86-91
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• 1999

This study is performed to evaluate the physical and meanical properties of oyster shell concrete. The result shows that the unit weights of concrete with oyster shell are less by 15 ~2% than that of the normla cement concrete. The highest strengths are achieved by 2.5% oyster shell concrete , with increased compressive strength by 4% , tensile strength by 6% and bending strength by 7% than that of the normal cement concrete, respectively. The static modulusof elasticity is in the range of 290$\times$10$^3$~314 $\times$10$^3$kgf/㎤ for 2.5~7.0% oyster shell concrete,which has showed about the same compared to that of the normal cement concrete. The Poisson's number of oyster shell concrete is less than that of the normal cement concrete. Accordingly, oyster shell concrete will improve the properties of concrete.

• Korean Journal of Agricultural Science
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• v.26 no.2
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• pp.49-55
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• 1999

This study is performed to evaluate the properties of permeable polymer concrete with blast furnace slag and fly ash. The following conclusions are drawn: 1. The highest strength is achieved by 50% filled blast furnace slag powder and fly ash permeable polymer concrete, it is increased 36% by compressive strength and 217% by bending strength than that of the normal cement concrete, respectively. 2. The static modulus of elasticity is in the range of $100{\times}10^3{\sim}130{\times}10^3kgf/cm^2$, which is approximately 43~51% of that of the normal cement concrete. 3. The dynamic modulus of elasticity is in the range of $102{\times}10^3{\sim}130{\times}10^3kgf/cm^2$, which is approximately less compared to that of the normal cement concrete. The highest dynamic modulus is showed by 50% filled blast furnace slag powder and fly ash permeable polymer concrete. The dynamic modulus of elasticity are increased approximately 0~4% than that of the static modulus. 4. The water permeability is in the range of $4.612{\sim}5.913l/cm^2/h$, and it is largely dependent upon the mix design.

• The Journal of Korean Physical Therapy
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• v.19 no.6
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• pp.5-10
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• 2007

Purpose: This study examined whether or not the balance performing ability of the disabled (blindness and deafness) is lower than normal people. Chronometry was used to compare the balance maintaining ability of blind and deaf subjects with that of normal subjects under the same conditions. Methods: In this study, balance foam, eye bandage, earplugs and headphones were used. The balance foam used in this study is smooth with slight elasticity and a convex upper side, 60cm wide, 15cm long and 9cm high. The eye bandage was used to artificially block the sight of the normal subjects, and the earplugs and headphones to block their hearing. Results: The mean time of the normal subjects standing with their eyes open, blindfolded and wearing ear plugs was 26.7, 19.8 and 28.7sec, respectively. The mean standing maintaining time for the blind and deaf subjects was 12.5 sec and 24.1 sec, respectively. The t-test result of the calculated mean time showed no significant difference (p>0.05) between the normal subjects and the normal subjects with their hearing blocked but there was a significant difference between the normal subjects with their hearing blocked and the deaf subjects (p>0.05). Conclusion: There was significance between the normal subjects and the normal subjects with their eyes blocked but there was no significant difference between the normal subjects with their eyes blocked and the blind subjects. Furthermore, there was a significant difference between the deaf and the normal subjects, which corresponds to the report showing that sight has a significant influence on balance.

• Structural Engineering and Mechanics
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• v.18 no.3
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• pp.315-330
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• 2004

A four-point bending RC beam strengthened with FRP plate is investigated based on the theory of elasticity. Taking the adhesive layer into account but ignoring some secondary parameters, the analytical solutions of the normal stress and shear stress on concrete-adhesive interface are obtained and discussed. Besides, the pure bending region of the beam is analyzed and the ultimate load of the beam is predicted. The results obtained in the present paper agree very well with both the results of FEM and the experimental findings.

• Steel and Composite Structures
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• v.50 no.2
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• pp.123-133
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• 2024

The paper deals with the propagation of Rayleigh waves in a nonlocal thermoelastic isotropic layer which is lying over a nonlocal thermoelastic isotropic half-space under the purview of Green-Lindsay model and Eringen's nonlocal elasticity in the presence of voids. The normal mode analysis is employed to the considered equations to obtain vector matrix differential equation which is then solved by eigenvalue approach. The frequency equation of Rayleigh waves is derived and different particular cases are also deduced. The effects of voids and nonlocality on different characteristics of Rayleigh waves are presented graphically.