• International Journal of Concrete Structures and Materials
• /
• v.9 no.4
• /
• pp.487-498
• /
• 2015

A proper initial curing is a very simple and inexpensive alternative to improve concrete cover quality and accordingly extend the service life of reinforced concrete structures exposed to aggressive species. A current study investigates the effect of wet curing duration on chloride penetration in plain and blended cement concretes which subjected to tidal exposure condition in south of Iran for 5 years. The results show that wet curing extension preserves concrete against high rate of chloride penetration at early ages and decreases the difference between initial and long-term diffusion coefficients due to improvement of concrete cover quality. But, as the length of exposure period to marine environment increased the effects of initial wet curing became less pronounced. Furthermore, a relationship is developed between wet curing time and diffusion coefficient at early ages and the effect of curing length on time-to-corrosion initiation of concrete is addressed.

• Journal of the Korean Society of Industry Convergence
• /
• v.4 no.4
• /
• pp.451-455
• /
• 2001

The epitaxial growth of Ge on the clean and surfactant(Sn) adsorbed surface of Ge(111) was studied by the intensity oscillation of a RHEED specular spot. In the case of epitaxial growth without the adsorbed surfactant, the RHEED intensity oscillation was stable and periodic up to 24ML at the substrate temperature of $200^{\circ}C$. Therefore the optimum temperature for the epitaxial growth of Ge on clean Ge(111) seems to be $200^{\circ}C$. However, in the case of epitaxial growth with the adsorbed surfactant, the irregular oscillations are observed in the early stage of the growth. The RHEED intensity oscillation was very stable and periodic up to 38ML, and the $d2{\times}2$ structure was not charged with continued adsorption of Ge at the substrate temperature of $200^{\circ}C$. These results may be explained by the fact that the diffusion length of Ge atoms is increased by decreasing the activation energy of the Ge surface diffusion, resulted by segregation of Sn toward the growing surface. From the desorption process, the desorption energy of Sn in Ge $\sqrt{5}{\times}\sqrt{5}$ structure is observed to be 3.28eV.

• Journal of the Korean Society of Food Culture
• /
• v.34 no.4
• /
• pp.411-423
• /
• 2019

This study conducted qualitative research through in-depth interviews on the diffusion process of Korean food in accordance with the length of residence of Chinese students in Korea. As the analysis method, the qualitative analysis method such as NVivo12.0 was used, and the analysis was performed through word frequency, word cloud, and coding matrix. The images of taste of Korean food were revealed as 'Spicy', 'Sweet', and 'Light taste' by both short-term Chinese residents and long-term Chinese residents. The long-term Chinese residents showed their dissatisfaction with the institutional food, and they also pointed out the importance of the matter of cooking for quick adaptation to life in Korea. The long-term Chinese residents also thought of Korean food as 'High-fiber food', and this was influenced by the 'Less-oil' cooking method of Korean food, which is different from the cooking method of Chinese food. The length of residence was used as a main variable of this study, and it was one of the factors having positive effects on the diffusion of Korean food and acculturation. It would be difficult to generalize the results because this study used the convenience sampling method and snowball sampling.

• Journal of the Institute of Convergence Signal Processing
• /
• v.4 no.4
• /
• pp.23-29
• /
• 2003

In this paper, we propose an idea for the improved 3-D sound system using conventional stereo headphones to obtain a better sound diffusion from the mono-sound recorded at an anechoic chamber. We use the HRTF(Head Related Transfer Function) for the sound localization and the wavelet filter bank with time delay for the sound diffusion. And we test the modified HRTF with the various sampling rate. We investigate the effects of the 3-D sound depending on the length of time delay at lowest frequency band. Also the correlation coefficient of the signals between the left channel and the right channel is measured to identify the sound diffusion. At last we obtain the diffusion sound using Cool Edit for reverberation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.1
• /
• pp.27-31
• /
• 2017

In this study, the effect of Tb inward diffusion on the magnetic properties of the Nd-Fe-B sintered magnets was studied. After sintering of the magnets, $TbF_3$ slurries were dip-coated on the surface of the samples, then heat-treatment was followed for $TbF_3$ diffusion. The element distribution in the magnets and the diffusion profiles of Tb ions were analyzed by an EPMA (electron probe micro-analyzer). Prolonged heat treatment resulted in a deeper diffusion length of Tb ions. Coercivity of the $1^{st}$ heat-treated sample showed 21.86 kOe, while that of the $1^{st}$, $2^{nd}$ heat-treated and annealed sample revealed 34 kOe.

• Progress in Superconductivity and Cryogenics
• /
• v.24 no.4
• /
• pp.16-24
• /
• 2022

Applications of REBa₂Cu₃O_7-δ tapes require joints with a simple manufacturing process, low resistance and good mechanical properties. In the present study, we successfully developed a copper diffusion joint between Cu-stabilized REBa₂Cu₃O_7-δ tapes that meets the above requirements without solder simply by applying flux, heat and pressurization. After a 3 min thermocompression process at approximately 150 δ and 336 MPa in air, two tapes were directly connected between Cu stabilizers by copper diffusion, which was proven by microstructure analysis. The specific resistivity of the copper diffusion joint reached 5.8 nΩ·cm² (resistance of 0.4 nΩ for a 306 mm splicing length) at 77 K in the self-field. The axial tensile stress reached 200 N without critical current degradation. The results show promise for the preparation of copper diffusion joints to be used in coils, attached tapes, and wire/cable terminals.

• Journal of the Korean Society of Combustion
• /
• v.10 no.1
• /
• pp.13-19
• /
• 2005

Measurements of flame length and NOx emissions have been conducted to investigate the effects of acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. When the acoustic excitation of a specific frequency is applied to coaxial air stream, flame length is dramatically reduced, resulting in reduction of flame residence time. Consequently, EINOx could decrease up to 35 % and this shows that acoustic excitation is effective in reducing NOx emissions. Mie scattering technique has been used to visualize the vortex structure induced by acoustic excitation and vortex formation, development and destruction were observed quantitatively. As a result, vortex entrains coflow air into fuel stream and mixing rate between fuel and air is significantly enhanced, which may contribute to reduction of NOx emissions.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.305-313
• /
• 2005

Measurements of flame length, width and NOx emissions have been conducted to investigate the effect of an acoustic excitation on flame structure in turbulent hydrogen diffusion flames with coaxial air. The resonance frequency of oscillations was varied between 259 ,514 and 728 Hz with power rate of 0.405 and 2.88w. When these frequencies imposed to hydrogen flames, dramatic reduction of flame length and NOx emission was achieved. And acetone planar laser-induced fluorescence technique was used to measure a concentration of the near field of driven axisymmetric jet. The air-fuel stoichiometric line was plotted to investigate the mixing layer and development of air entrainment to fuel jet. Consequently, acoustic excitation on flame could enhance the air-fuel mixing resulting in abatement of NOx emission quantitatively.

• 한국연소학회:학술대회논문집
• /
• 2004.06a
• /
• pp.118-123
• /
• 2004

The combustion characteristics of 0.03MW turbulent methane/oxygen diffusion flames have been investigated to give basic informations for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since 3-5% nitrogen is intrinsically included from the current oxygen producing processes. Flame lengths and NOx concentrations were measured by varying flow velocities with and without installing quarls. Flame stabilities are significantly enhanced by oxyfuel combustion in contrast to air-fuel combustion. Flame length decreases with increasing fuel or oxygen velocity because of the enhancement of turbulent mixing. NOx concentration was reduced with increasing flo velocities. This can be attributed to the entrainment of inert product gases into flame decreasing flame temperature. The installation of quarl on the burners rather increased NOx concentration since the quarl blocked the entrainment above the nozzles.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.11 s.242
• /
• pp.1277-1284
• /
• 2005

The combustion characteristics of methane oxygen diffusion flames have been investigated to give basic information for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since the small amount of nitrogen is included from the current low cost oxygen production process. Flame lengths decreased with increasing fuel or oxygen velocity because of the enhancement of mixing effect. Correlation equation between flame length and turbulent kinetic energy was proposed. NOx concentration was reduced with increasing fuel or oxygen velocity because of the enhanced entrainment of the product gas into flame zone as well as the reduction of residence time in combustion zone.