• Journal of the Korean institute of surface engineering
• /
• v.50 no.5
• /
• pp.360-365
• /
• 2017

In this study, ion release and biocompatibility of sintered Ni-Cr-Ti alloy for dental prosthodontics have been researched by corrosion and cell culture test. The microstructures of the alloys were observed by optical microscope, and corrosion behavior was investigated using potentiostat (Model PARSTAT 2273, EG&G, USA). Cell culture was carried out using hGf cell in DMEM (Welgene Inc., South Korea) supplemented with 10% fetal bovine serum (FBS) (Welgene Inc., South Korea) and antibiotic antimycotic solution (Welgene Inc., South Korea). After corrosion and cell culture test, surface morphologies were observed by field-emission scanning electron microscopy. For wettability behaviors, contact angles were measured by wettability test. As the content of Ti increased, the number of pit decreased and the corrosion resistance was improved from anodic polarization test, also, polarization resistance of samples containing Ti remarkably improved as compared with the alloy not containing Ti. The sintered alloy showed a low contact angle due to the pores formed on the surface. The addition of Ti element showed that the cell survival rate was better than that of the control group.

• Asian-Australasian Journal of Animal Sciences
• /
• v.30 no.4
• /
• pp.449-454
• /
• 2017

Recently, increasing attention has been paid to the welfare of farm animals, which have been evaluated using behavioral and physiological measures. However, so far, the measures have almost always been used to estimate poor welfare. In this review, firstly we focus on how oxytocin (OT) relates to positive social behavior, pleasure, and stress tolerance, and second on which management factors stimulate OT release. OT induces maternal and affiliative behaviors and has an anti-stress effect. Further, OT is produced during enjoyable events, and has positive feedback on its own release as well. Therefore, to some extent, the relationship of OT to positive normal behavior was mutually beneficial-heightened OT concentration owing to comfortable rearing conditions induces positive social behavior, which in turn may increase OT concentration. Hence, studies on animal welfare should pay more attention to increasing comfort and the stress tolerance, rather than only focusing on when stress occurs in farm animals.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.1 no.1
• /
• pp.9-20
• /
• 1989

This paper presents an analysis to predict thermal behaviors of water in ice storage tank during the coldness release process. To deal with complicated transient phenomena due to ice-water phase change and the density inversion, a theoretical model which consists of initial perfectly mixed, stratified and thermal diffusion state was introduced and a criterion on the growth of thermal boundary layer was developed. The analysis includes considerations on the type of ice-making heat exchanger, refrigerator on/off and tank arrangement. Also, discussions on the various parameters and operating conditions which have influence on the performance of the system were made. Finally, simulated results were shown, which agreed with experiments in trends reasonably.

• Structural Engineering and Mechanics
• /
• v.23 no.2
• /
• pp.163-175
• /
• 2006

In this paper, the dynamic response of a piezoelectric layer with a penny-shaped crack is investigated. The piezoelectric layer is subjected to an axisymmetrical action of both mechanical and electrical impacts. Two kinds of crack surface conditions, i.e., electrically impermeable and electrically permeable, are adopted. Based upon integral transform technique, the crack boundary value problem is reduced to a system of Fredholm integral equations in the Laplace transform domain. By making use of numerical Laplace inversion the time-dependent dynamic stress and electric displacement intensity factors are obtained, and the dynamic energy release rate is further derived. Numerical results are plotted to show the effects of both the piezoelectric layer thickness and the electrical impact loadings on the dynamic fracture behaviors of the crack tips.

• Tribology and Lubricants
• /
• v.18 no.6
• /
• pp.384-388
• /
• 2002

The adequate design of a passenger car braking system, which is directly related to the safety of a car, is very important since the safety is an essential design parameter of a car to keep men and car from the damage. The thermal behaviors of the ventilated disk has been investigated based on the air cooling effects during repeat braking operations. In this study, the thermal behavior of ventilated disk brake system was investigated by numerical method. The 3-Dimensional unsteady model was simulated by using a general purpose software package “FLUENT” to obtain the temperature distributions of disk and pad. The model includes the more realistic braking method, which repeats braking and release. The effects of aspect ratio of ventilated hole on the heat dissipation was investigated.

• Journal of Pharmaceutical Investigation
• /
• v.40 no.5
• /
• pp.263-267
• /
• 2010

Nanoemulsions have been widely investigated for many years because of their attractive and unique characteristics. Nanoemulsions are composed of oil, surfactant, co-surfactant and water. Especially, cosurfactant plays a critical role in formation of nanoemulsions. In pharmaceutical area, a pre-concentrate form of nanoemulsions which is known as self-nanoemulsifying drug delivery systems (SNEDDS) was available for some water-insoluble drugs. In this study, we investigated the functional behaviors of cosurfactant in design of SNEDDS and nanoemulsions. Cremophor RH 40$^{(R)}$, Propylene carbonate and medium chain triglyceride were selected for surfactant, cosurfactant and oil, respectively. Cyclosporine was employed as a drug. Phase diagrams showed the area of isotropic o/w region which forms o/w nanoemulsions was not significantly affected by the compositional ratio of cosurfactant. But, drug solubilization capacity, droplet size of nanoemulsions and drug release rate were greatly affected by the cosurfactant.

• Journal of Power System Engineering
• /
• v.3 no.3
• /
• pp.36-43
• /
• 1999

Many of thermodynamic-based diesel combustion simulations incorporated a model of fuel spray which attempts to describe how the spray develops according to time. Because the spray geometry is an essential aspect of the fuel-air mixing process, it is necessary to be calculated quantitatively for the purpose of heat release and emission analysis. In this paper, we proposed the calculating method of non-evaporation spray behaviors by injection rate shapes under actual operating conditions of diesel engine. We confirmed the utility of this calculating model as the calculated results were compared with the measured results. This calculating program can be applied usefully to study on the diesel spray behavior.

• Korean Membrane Journal
• /
• v.6 no.1
• /
• pp.37-43
• /
• 2004

Comb-type graft hydrogels composed of alginate and poly(N-isopropylacrylamide) (PNIPAAm) were prepared to manifest rapid temperature and pH sensitivity. To appear the electro-sensitivity, the polyaniline, conducting polymer, was added into the matrix. The swelling kinetics and ratios were compared under the various compositions of polyaniline. The swelling behaviors revealed that conducting polymer/hydrogel composites could control the swelling ratio and kinetics. The addition of polyaniline in the matrix improved the thermal stability in comparison with that of the hydrogel without polyaniline. In temperature sensitivity, the adding the polyaniline into the matrix decreased the degree of change in the swelling ratio. The swelling ratios continuously increased with increasing pH values. The drug release rate from the hydrogel increased with the adding the polyaniline and the applying the direct voltage to the hydrogels.

• Journal of the Korean Society of Safety
• /
• v.13 no.4
• /
• pp.71-78
• /
• 1998

Real crack and fracture surfaces have irregularities producing zigzag contours. These irregularities are analysed by a fractal geometry which has been by a Mandelbrot. We obtained a fractal dimension which is one of the fractal characteristics. It is also estimated by an vertical section method that fractal characteristics in the fractured surfaces can be obtained as the crack grows. Moreover fractal fracture energy that corresponds to an energy release rate is shown to find relationships between fractal dimensions and crack behaviors. From these results, we concluded that a fractal characteristics analysis for a crack can be applied to a fracture mechanics.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.159-164
• /
• 2000

The fracture behaviors of aluminum foils and sheet papers were analyzed on the basis of linear elastic fracture mechanics(LEFM). The fracture loads of the similarly shaped specimens were calculated by dimensional analysis. The actual fracture loads were measured using the simple tension equipment. The predicted fracture loads were compared with the experimental results.