• Journal of the Korean Ceramic Society
• /
• v.47 no.4
• /
• pp.296-301
• /
• 2010

The objective of the present research is to develop the body for Temmoku Teabowl, in order to manufacture the Temmoku Teabowl with the characteristics of Jian Ware, which has a rich dark brown color and has been extolled as the representative fine article of Temmoku Teabowl. Basic composition was first determined using domestically produced clay, kaolin and pottery stone as starting materials. After the addition of calcinated Hwangto, which is rich in iron, the mixture was subjected either to oxidizing calcination at $1260^{\circ}C$ to produce a body with a color suitable for Hanam ware or to reducing calcination at $1230^{\circ}C$ to produce a body with a color suitable for Jian Ware. The bodies produced in this research showed the strength value of $380{\sim}36\;Kg/cm^2$, the specific gravity of 2.304~2.310, the absorption ratio of 4.103~3.897, and the porosity of 8.608~8.207%.

• Proceedings of the Acoustical Society of Korea Conference
• /
• autumn
• /
• pp.379-382
• /
• 2001

In the muffler industry, the main purpose of the research works is to determine a way to increase the TL (Transmission Loss) properties of the muffler, without deteriorating the back pressure influence. In order to obtain better results, several works have been done by changing the geometrical characteristics of the muffler or the type of the muffler. This work will focus on the perforated muffler components with concentric chamber, to investigate the effect of a non-uniform porosity along the inner perforated tube of the muffler on the TL. It is noted that varying the perforation ratio affects the peaks frequencies of the TL, especially fer $2\pi < kL < 4\pi$ (in the case of L : 200mm for the concentric resonator). The magnitudes of the TL, for this range of frequencies, vary noticeably by changing the porosity distribution.

• 한국해양학회지
• /
• v.23 no.3
• /
• pp.146-157
• /
• 1988

Properties of porosity, compressional wave velocity, velocity anisotropy, electrical resistivity, and resistivity anisotropy are measured and calculated for two DSDP clay-rich hemipelagic sequences in the northwestern Pacific. Velocity and resistivity increase with burial depth at the expense of decreasing porosity. Profiles of velocity anisotropy and resistivity anisotropy show almost the same trend. Horizontally developed low aspect ratio pores may generate velocity and resistivity anisotropy. The preferred orientation of clay minerals is also believed to be responsible for the observed anisotropy.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.05a
• /
• pp.553-554
• /
• 2006

This paper presents the effects of different operating parameters on the performance of a proton exchange membrane (PEM) fuel cell by a three-dimensional computational fluid dynamics (CFD) model. The effects of different operating parameters on the performance of PEM fuel cell studied using pure hydrogen on the anode side and air on the cathode side. The various parameters are temperatures, pressures, humidification of the gas steams and various combinations of these parameters. In addition, geometrical and material parameters such as the gas diffusion layer (GDL) thickness and porosity as well as the ratio between the channel width and the land area were investigated.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.6
• /
• pp.855-859
• /
• 2012

Silicon nanowires (SiNWs) were fabricated by a metal-assisted chemical etching of Si and the porous structure on their surfaces was controlled by changing the volume ratio of the etching solution composed of hydrofluoric acid, hydrogen peroxide, and deionized water. The concentration of hydrogen peroxide as the oxidant was varied for controlling the porosity of SiNWs. The optical properties of porous SiNWs were unique and very different from those of single-crystalline Si, as characterized by measuring their photoluminescence and Raman spectra for different porosities.

• Corrosion Science and Technology
• /
• v.5 no.1
• /
• pp.15-22
• /
• 2006

The introduction of two-grid inside a conventional process system produces a reactive coating deposition and increases metal ion ratio in the plasma, resulting in denser and smoother films. The corrosion behaviors of TiN coatings were investigated by electrochemical methods, such as potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in deaerated 3.5% NaCl solution. Electrochemical tests were used to evaluate the effect of microstructure on the corrosion behavior of TiN coatings exposed to a corrosive environment. The crystal structure of the coatings was examined by X-ray diffractometry (XRD) and the microstructure of the coatings was investigated by scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM). In the potentiodynamic polarization test and EIS measurement, the corrosion current density of TiN deposited by two grid-attached magnetron sputtering was lower than TiN deposited by conventional magnetron type and also presented higher Rct values during 240 h immersion time. It is attributed to the formation of a dense microstructure, which promotes the compactness of coatings and yields lower porosity.

• Journal of the Korean Ceramic Society
• /
• v.26 no.2
• /
• pp.147-156
• /
• 1989

The effects of starting composition, sintering temperature and porosity on the mechanical properties of hydroxyapatite ceramics were investigated. The hydroxyapatite powder were prepared by precipitation method using Ca(NO3)2.4H2O and (NH4)2.HPO4. The obtained powders were Ca-deficient hydroxyapatites and as the Ca/P mole ration in the initial solution was increased, the particle size of the precipitates was decreased, and the decomposition of hydroxyapatite to $\beta$-TCP was controlled. The porosity, as well as Ca/P mole ratio in starting composition and sintering temperature, plays major role in the mechanical properties of dense hydroxyapatite ceramics.

• KSBB Journal
• /
• v.13 no.4
• /
• pp.449-455
• /
• 1998

The bacterial motility in sand was studied with Alcaligenes xylosoxidans Y234 which is known as a strong decomposer of aromatic chemicals, especially toluene. Apparent motility coefficient (${\mu}$c,app) and apparent chemotaxis coefficient (${\mu}$c,app) for toluene were measured in the sands which have four different porosities. Adsorption ratio of Alcaligenes xylosoxidans Y234 on the sands was measured as 17%. The ramdom motility coefficients were 0.85∼1.68${\times}$10-3$\textrm{cm}^2$/sec, and decreased as the porosity of sands decreased. Apparent chemotaxis coefficients were measured as 1.1∼6.8${\times}$10-5$\textrm{cm}^2$/sec, and decreased as the porosity decreased and with time. The tendency of alcaligenes xylosoxidans Y234 movement towards toluene seemed very weak and showed little chemotaxis.

• Structural Engineering and Mechanics
• /
• v.70 no.1
• /
• pp.97-112
• /
• 2019

Using the classical, first order and third order shear deformation plates theories the motion equations of an undrained porous FG circular plate which is located on visco-Pasternak elastic foundation have been derived and used for free vibration analysis thereof. Strains are related to displacements by Sanders relationship. Fluid has saturated the pores whose distribution varies through the thickness according to three physically probable given functions. The equations are discretized and numerically solved by the generalized differential quadrature method. The effect of porosity, pores distribution, fluid compressibility, viscoelastic foundation and aspect ratio of the plate on its vibration has been considered.

• Korean Journal of Metals and Materials
• /
• v.47 no.5
• /
• pp.290-296
• /
• 2009

We report on the effects of mixing of powders with various particle sizes on fracture toughness and wear resistance of thermally sprayed WC-10Co-4Cr coating layers fabricated by HVOF (high-velocity oxygen fuel) process. The size and the mixing ratio of powders were changed in order to get high fracture toughness and wear resistance. The mixing of small amount of coarse powders with fine powders resulted in the highest fracture toughness and wear resistance due to the lowest porosity in coating layers.