• Journal of Korean Society of Steel Construction
• /
• v.25 no.5
• /
• pp.569-578
• /
• 2013

In a super-tall building construction, thick and large-sized embed plates are usually used to connect mega structural steel members to RC core wall or columns by welding a gusset plate on the face of the embed plate with T-shape. A large amount of heat input accumulated by weld passes causes the plates to expand or deform. In addition, the temperature of concrete around the plates also could be increased. Consequently, cracks and spalls occur on the concrete surface. In this study, the effect of weld heat on embed plates and 80MPa high strength concrete is investigated by considering weld position (2G and 3G position), edge distance, concrete curing time, etc. Measured temperature of the embed plates was compared with the transient thermal analysis results. Finally, push-out tests were performed to verify and compare the shear studs capacity of the embed plate with design requirement. Test result shows that the shear capacity of the plate is reduced by 14%-19% due to the weld heat effect and increased as the concrete curing time is longer.

• Journal of Energy Engineering
• /
• v.24 no.3
• /
• pp.150-163
• /
• 2015

Gasification technology is one of the representative next-generation fossil fuel utilization technologies, converting low grade fossil fuels such as coal, heavy residue oil, pet-coke into highly clean and efficient energy sources. Accordingly, related market demand for gasification technology is ever increasing steadily and rapidly. A few years ago, conventional pulverized coal utilization technology had an edge over the gasification technology but the most significant technical barrier of limited capacity and availability has been largely overcome nowadays. Futhermore, it will be more competitive in the future with the advancement of related technologies such as gas turbine, ion transfer membrane and so on. China has recently completed a commercialization-capable large-scale coal gasification technology for its domestic market expansion and foreign export, rapidly becoming a newcomer in the field and competing with existing US and EU technical leadership at comparable terms. Techno-economic aspect deserves intensive attention and steady R&D efforts need to continue in organized, considering that gasification technology is quite attractive combined with $CO_2$ capture process and coal to SNG plant is economically viable in Korea where natural gas is very expensive. In the present paper, recent technology development and commercialization trend of many leading companies with coal gasification expertise have been reviewed with significant portion of literature cited from the recently held '2014 Gasification Technology Conference'.

• Applied Microscopy
• /
• v.32 no.3
• /
• pp.265-273
• /
• 2002

The purpose of this study was to observe the influences of the water fluoride concentration on the growth changes, the histologic characteristics of osteoblast in the tibia of growing newborn rats by using electron microscopy and on the composition changes of bone matrix in those by using energy dispersive x-ray system (EDX). The water fluoride concentration was respectively 0 ppm (contrast group), 100 ppm (100 ppm group), 200 ppm (200 ppm group) and 300 ppm (300 ppm group). The results of the investigation by using electron microscopy were as followed. In contrast group, the traditional cuboidal osteoblasts were observed. In 100 ppm group, several reversal line, the newly formed osteoid by the strongly activated osteoblast and the well developed rough endoplasmic reticulum, mitochondria in cytoplasm of osteoblast were observed. Also, many secretory vesicle around cell membrane were observed and some fused with cell membrane released secretory granule out of cell. In 200 ppm group, the depressed osteoblasts were observed, mitochondria in cytoplasm were expanded and cristae shape in mitochondria were destroyed. Also, the ribosome at the surface of rough endoplasmic reticulum were not observed. In 300 ppm group, the adjacent osteoblasts with endosteum were irregularly arranged, the cell membrane were destroyed and organelles were flowed out of cell. On the other hand, the results of the investigation by using energy dispersive x-ray system were as followed. P and Ca concentrations in 100 ppm group were increased more than those in contrast group. But, in 200 and 300 ppm group were not increased more than those in 100 ppm group. Therefore, the activities of the osteoblasts were increased, the bone matrix were actively synthesized by the supplied water fluoride. But, the osteoblasts were destroyed, inhibited by the higher water fluoride concentration.

• The Korean Journal of Malacology
• /
• v.27 no.1
• /
• pp.15-27
• /
• 2011

This study was performed to observe ultrastructure of the gill and to ascertain the effect of salinity on histopathological and ultrastructural changes in the gill of the Japanese clam, Corbicula japonica. Experimental period was 7 days. Experimental groups consisted of control, 5, 10, 20 psu. $LC_{50}$ (96 h.) by the probit was 19.55 psu. Mortality was significantly different from the control (p < 0.05). Inner demibranch of the gill of C. japonica was wider 1.37 times than outer demibranch (p < 0.001). The filament zone on the plica can be distinguished by the six epithelial celll cell; frontal ciliated epithelium ($7{\mu}m$), latero-frontal ciliated epithelium ($5{\mu}m$), postlatero-frontal epithelim ($3{\times}8{\mu}m$), and lateral ciliated epithelium ($5{\mu}m$) in the frontal zone, endothelial cellin the intermediate zone, and abfrontal cell in the abfrontal zone. It had one type of secretory cell that was filled with fibrous substances of low electron density. The gill of C. japonica exposed to 5 psu for 7 days was observed partially disappearance of the cilia, and glycogen granule in the filament. In the 10 psu, gill appeared partially modification of epithelial cell and destruction of the glycocalyx. Gill exposed to 20 psu was extended nuclus of the ciliated epithelial cell, destruction of the organelles, and observed glycogen granules infiltration and numerous vacuoles. Moreover, more than 50% filaments were observed that come out chitinous rod from disappearance of epithelial cell in the filament. Therefore, the destruction of the cilia and epithelial cell induce physiological activity and it may be leading directly to death.

• Korean Journal of Soil Science and Fertilizer
• /
• v.20 no.3
• /
• pp.209-216
• /
• 1987

The experiments were carried out in lab. as well as in pots, to develop the agricultural usage of water swellable polymer, a kind of polyacrylic acid(K-sorb) synthesized by the Korea Advanced Institute of Science & Technology (KAIST) recently. The changes of soil physical properties and the influences to crops were investigated with various levels of K-sorb. When the K-sorb mixed with soils and soaked up distilled water, the volume of soils increased with the increase of soil available water contents and increase of K-sorb application levels. The rate increase of soil available water was higher in the coarse textured soils than in the fine while the swelling rate of soil volume showed adverse tendencies. A positive linear regression was observed between the contents of available soil water and levels of K-sorb. K-sorb application decreased bulk density and hardness due to the increase of porosity after soybean cultivation. The permeability in coarser textured soils such as sandy and coarse loamy families was decreased with the increase of K-sorb but in the medium textured soils it was opposite. At higher levels of K-sorb, about 0.5%, the permeability abruptly decreased due to dispersion and vertical movement in silty soils, while it was not changed in fine clayey soils but has the same trend with silty soils. In the plot of 0.3% of K-sorb application, the growth of soybean such as number of pods and stem length etc. increased and the yield also increased about 1.2-1.8 times of control. The optimum amounts of K-sorb were slightly different according to soil texture but estimated from regression curves were about 0.2% to 0.35% of soils in dry weight bases.

• Korean Journal of Food Science and Technology
• /
• v.27 no.1
• /
• pp.112-118
• /
• 1995

The effect of various packaging methods on kimchi quality was investigated in order to develop the packaging techniques for preventing commercial kimchi products from inflation and explosion, due to fermentative gas evolved during storage and distribution. Kimchi was packaged in different methods; 1) atmospheric packaging(AP), 2) check valve packaging(CV), 3) double packaging(DP), and 4) vacuum packaging(VP). The quality of kimchi during storage at $10^{\circ}C$ was evaluated in terms of gas composition, free volume, pH, titratable acidity color index and sensory properties. The gas composition inside packages showed different curves according to the packaging methods. Due to fermentative gas accumulation in both AP and CV, $CO_2$ concentration increased by 2 stepwise pattern, while $O_2$, concentration decreased exponentially. In DP, $O_2$ concentration remained constant, but $CO_2$ concentration increased by 2 stepwise pattern and then decreased. In contrast, VP produced low $O_2$ and high $CO_2$ concentrations only at the end of storage. The free volume in both AP and CV showed typical sigmoidal curves similar to $CO_2$ concentration changes. It remained constant in DP, but started to increase at the late stage of storage in VP. There was no significant effect of packaging methods on pH changes of kimchi. In titratable acidity, DP maintained relatively higher than others. Regarding to the color change of crushed kimchi juice in all packages, L and b values decreased exponentially but a value remained constant during storage. Color index(L b/a) of crushed kimchi juice decreased exponentially and remained constant at the end of storage. The growth of lactic acid bacteria was VP, CV, AP, DP in increasing order. In sensory test, the sourness scores of DP were fairly higher than those of others, but the texture was not significantly affected by the packaging methods. The preference for kimchi showed VP>AP, CV>DP in order of score. In this study, it could be proposed to employ DP and VP method as the effective packaging techniques for preventing commercial kimchi products from inflation.

• Korean Journal of Food Science and Technology
• /
• v.34 no.3
• /
• pp.449-453
• /
• 2002

This was studied to evaluate the quality characteristics of the bread added chitosan during storage at room temperature(Temp. $27^{\circ}C{\pm}2$, RH $75%{\pm}10$). The volume of the dough was increased depending on the larger molecular weight and the higer concentration of chitosan but was decreased at 0.50% of 120 kDa chitosan. The water activity was low depending on the larger molecular weight and the higher concentration of chitosan at the early storage, but maintained constantly during storage totally. The colors of the bread was hardly affected by 30 kDa of chitosan. Textural characteristics was improved at 30 kDa and 120 kDa of chitosan. Especially, the change of the hardness were maintained lower at 30 kDa, 120 kDa of chitosan during storage than that of standard. These results showed that the quality of the bread by added 30 kDa of chitosan was improved highly.

• Applied Chemistry for Engineering
• /
• v.32 no.1
• /
• pp.117-123
• /
• 2021

In this study, the composite was prepared by mixing SiOx, soft carbon, and carbon black and the electrochemical properties of lithium ion battery were investigated. The content of SiOx added to improve the capacity of the soft carbon anode material was varied to 0, 6, 8, 10, 20 wt%, and carbon black was added as a structural stabilizer for reducing the volume expansion of SiOx. The physical properties of prepared CB/SiOx/C composite were investigated through XRD, SEM, EDS and powder resistance analysis. In addition, the electrochemical properties of prepared composite were observed through the charge/discharge capacity, rate and impedance analysis of the lithium ion battery. The prepared CB/SiOx/C composite had an inner cavity capable of mitigating the volume expansion of SiOx by adding carbon black. The formed internal cavity showed a low initial efficiency when the SiOx content was less than 8 wt%, and low cycle stability when the content of SiOx was less than 20 wt%. The CB/SiOx/C composite containing 10 wt% of SiOx showed an initial discharge capacity of 537 mAh/g, a capacity retention rate of 88%, and a rate of 79 at 2C/0.1C. SiOx was added to improve the capacity of the soft carbon anode material, and carbon black was added as a structural stabilizer to buffer the volume change of SiOx. In order to use the CB/SiOx/C composite as a high-efficiency anode material, the mechanism of the optimal SiOx and the use of carbon black as a structural stabilizer was discussed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.9
• /
• pp.92-100
• /
• 2017

The Helicopter MRA Control Rod System has the important function of controlling the speed, height, and direction of helicoptersby adjusting the main rotor disc. However, the ingress of water into the inner control rod can cause ice damage in the rod during winter operation and also corrosion;these defects need to be rectified. The water flowed into the control rod through the upper side space, and the rod was cracked during icing expansion occurring at low temperature. The corrosion occurred due to the lack of coating process during the manufacturing process. To resolve these problems, the upper rod was sealed to prevent water inflow and a coating process was added to prevent corrosion. These solutions were verified by awaterproof test and a salt fog test. The phenomena, causes and measures were reviewed and the methods of improvement were established and proven. This proposed technology to prevent water infiltration and corrosion will contribute to the safety of rotary wing aircraft.

• Journal of Life Science
• /
• v.18 no.8
• /
• pp.1164-1168
• /
• 2008

We investigated gravitropic responses in the primary root of maize (Zea mays) seedlings which were exposed to salt stress. The maize roots salt-stressed with higher than 100 mM NaCl or KCl started to reveal enhanced gravitropic curvature after 2 hours form the gravi-stimulation. Such a promotion was not caused by sodium phosphate, but invoked by potassium phosphate, indicating the active component is $K^{+}$. Because NaCl increased gravitropic curvature, despite that $Na^{+}$ did not played any role, we evaluated the role for $Cl^{-}$ by comparing the effects of $MgCl_2$ and $MgSO_4$. The enhancement of the curvature only with $MgCl_2$ revealed that $Cl^{-}$ played a role in the gravi-response, indicating the involvement of anion channels. These results suggest that both of $K^{+}$ and $Cl^{-}$ play roles in the regulation of osmosis that is required for cell expansion in gravitropism as well as in nyctinasty and stomatal opening.