• The Journal of Engineering Geology
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• v.15 no.3
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• pp.337-348
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• 2005

Jurassic granite from Pocheon area were tested to investigate the effect of microcracks on mechanical properties of the granite. Three oriented core specimens were used for uniaxial compressive tests and each core specimen are perpendicular to the axes'R'(rift plane),'c'(grain plane) and'H'(hardway plane), respectively Among vacious elastic constants, the variation of Poisson's ratio as function of the directions was examined. From the related chart between ratio of failure strength and Poisson's ratio, H-specimen shows the highest range in Poisson's ratio and Poisson's ratio decreases in the order of C-specimen and R-specimen. The curve pattern is nearly linear in stage $I\simIII$ but the slope increases abruptly in stage H-3. As shown in the related chart, diverging point of a curve is formed when ratio of failure strength is $0.92\sim0.96$ Stage IV -3 is out of elastic region. The behaviour of rock in the four fracturing stages was analyzed in term of the stress-volumetric strain me. From the stress increment-volumetric strain equations governing the behaviour of rock, characteristic material constants, a, n, Q, m and $\varepsilon_v^{mcf}$, were determined. Among these, inherent microcrack porosity$(a, 10^{-3})$ and compaction exponent(n) in the microcrack closure region(stage I ) show an order of $a^R(3.82)>a^G(3.38)>a^H(2.32)\;and\;n^R(3.69)>n^G(2.79)>n^H(1.99)4, respectively. Especially, critical volumetric microcrack strain($\varepsilon_v^{mcf}$) in the stage W is highest in the H-specimen, normal to the hardway plane. These results indicate a strong correlation between two major sets of microcracks and mechanical properties such as Poisson's ratio and material constants. Correlation of strength anisotropy with microcrack orientation can have important application in rock fracture studies.

• Horticultural Science & Technology
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• v.34 no.6
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• pp.886-897
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• 2016

The physical properties of rooting media for the establishment of plugs in a greenhouse are modified according to variations in the greenhouse environment throughout the season. In this study, we established a standard for rooting media for the production of plug seedlings for each growing season (summer, winter and spring fall). Eight types of peatmoss (PM) and 4 types of perlite (PL) commonly used in Korea were collected and blended with the ratio of 7 parts PM to 3 parts PL (v/v) to make 32 different rooting media blends. We determined the total porosity (TP), container capacity (CC), air-filled porosity (AFP), pH, and electrical conductivity (EC) of the 32 media blends, and 6 media blends were selected for seasonal use. We also conducted additional analyses for plant easily available water (EAW), buffering water (BW), cation exchange capacity (CEC), and nutrient contents in the 6 media blends. The TP, CC, and AFP of the 32 media blends ranged from 64.7 to 96.0%, 42.9 to 90.1%, and 1.3 to 27.8%, respectively, indicating that the physical properties were strongly influenced by the type of PM and PL. The pH and EC of the PMs ranged from 2.96 to 3.81 and 0.08 to $0.47dS{\cdot}m^{-1}$, respectively. However, after blending the PM with the PL the pH was raised and the EC was lowered The media blends selected for the summer growing season were Blonde Golden peatmoss (BG) + No. 1 perlite size < 1 mm (PE1) and Latagro 0-10 mm (L1) + No. 2 perlite size 1-2 mm (PE2). These two media blends had 89.8-90.9% of TP, 80.8-81.3% of CC, and 9.0-9.7% of AFP. The media blends selected for the winter growing season were Sfagnumi Turvas (ST) + PE2 and Latagro 20-40 mm (L3) + PE2. These media blends had 79.9-86.7% of TP, 60.4-74.9% of CC, and 11.8-19.6% of AFP. The TP, CC, and AFP of two media blends, BG + No.3 perlite 2-5 mm (PE3) and Orange peatmoss (O) + PE3, selected for the spring and fall growing seasons, respectively, were 85.2-87.3%, 77.9%, and 7.4-9.4%, respectively. The percentage of EAW of the media blends selected for the spring, summer, and winter growing seasons ranged from 24.2-24.9%, 22.0-28.6%, and 18.0-21.8%, respectively, but the percentages of BW were not significantly different among the selected root media blends. The pH, EC, and CEC of the 6 selected media blends ranged from 3.11-3.97, $0.06-0.26dS{\cdot}m^{-1}$, and $97-119meq{\cdot}100g^{-1}$, respectively.

• Applied Chemistry for Engineering
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• v.21 no.2
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• pp.183-187
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• 2010

Activated carbons (ACs) have been prepared from pitch by the combination of a chemical oxidation with different $H_2O_2$ concentrations i.e., 5, 15, and 25 wt% and a chemical activation with KOH at a constant KOH/pitch ratio of 3/1. The influence of $H_2O_2$ solution on the microporous properties of the pitch and the final activated carbons were invested using XRD, FT-IR, XPS, $N_2$-adsorption, and SEM. XRD indicated that the value of interplanar distance $d_{002}$ increased by chemical oxidation. FT-IR and XPS results showed that the chemical oxidation promoted the formation of surface oxygen functionalities. Also, the specific surface area of the resulting ACs was increased with increasing the concentration of $H_2O_2$ chemical oxidation and showed a maximum value of $2111m^2/g$ at 25 wt% $H_2O_2$ concentration.

• Journal of Mushroom
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• v.9 no.4
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• pp.166-169
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• 2011

In this study we carried out to find suitable nutrient supplement of corncob as a main carbon source for bottle culture of oyster mushroom. Data from chemical analysis of Kapok seed cake(KP) treatment showed 20.2 of C/N ratio, $0.28g/cm^3$ of bulk density and 74.2% of porosity. Mushroom yield of KP treatment is 158g/bottle that is similar to control(150g/bottle). However, the price of KP is 400 won/kg that is cheaper than 550 won/kg of cotton seed cake(CS). The highest REV(relative feed value) also was observed KP treatment. A further study is required determine practical animal performance by feeding the corncob-based KP.

• Journal of Microbiology and Biotechnology
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• v.27 no.4
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• pp.747-758
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• 2017

Chronic wounds, pressure sores, lesions, and infections of microbial origin in bedridden, paralyzed, or malnutrition patients remain the object of study of many researchers. A variety of factors behind the development of these disorders are related to the patient's immune system, making it unable to respond effectively to the treatment of the wound. These factors can be properly controlled, giving particular importance to the ethiology and stage of the wound, as well as the time periods corresponding to the replacement of the dressings. The present research reports a novel foam/soft material, ${{\small}L}$-Cys-g-PCL, with an application for decubitus/pressure ulcers, especially for wounds with a difficult healing process due to infections and constant oxidation of the soft tissues. During this work, the interactions between S. aureus and ${{\small}L}$-Cys-g-PCL foam were studied under conditions that simulate decubitus ulcers; namely, pH and exudate. The effects of duration of grafting (1 or 8 h) and pH (7.0 and 8.9) on wettability, surface energy, swelling, and porosity were also evaluated. Results showed an effective microbicidal activity exhibiting an inhibition ratio of 99.73% against S. aureus. This new ${{\small}L}$-Cys-g-PCL soft material showed saftey to contact skin, ability to be shaped to fill in sunken holes (craters) - pressure ulcers stage III - and to act as a smart material responsive to pH, which can be tailored to develop better swelling properties at alkaline pH where exudates are normally higher, so as to address exudate self-cleaning and prevention of desiccation.

• Korean Journal of Materials Research
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• v.19 no.11
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• pp.601-606
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• 2009

$BiFeO_3$ (BFO) thin films were prepared on $Pt/TiO_2/Si$ substrate by r.f. magnetron sputtering. The effects of deposition pressure on electrical properties were investigated using measurement of dielectric properties, leakage current and polarization. When BFO targets were prepared, Fe atoms were substituted with Mn 0.05% to increase electrical resistivity of films. (Fe+Mn)/Bi ratio of BFO thin films increases with increasing partial pressure of $O_2$ gas. The deposited films showed the only BFO phase at 10 mTorr, the coexistence of BFO and $Bi_2O_3$ phase at 30-50 mTorr, and the only $Bi_2O_3$ phase at 70 mTorr. The crystallinity of BFO films was reduced due to the higher Bi contents and the decrease of surface mobility of atoms at high temperature. The porosity and surface roughness of films increased with the increase of the deposition pressure. The films deposited at high pressure showed low dielectric constant and high leakage current. The dielectric constant of films deposited at various deposition pressures was 84${\sim}$153 at 1 kHz. The leakage current density of the films deposited at 10${\sim}$70 mTorr was about $7{\times}10.6{\sim}1.5{\times}10.2A/cm^2$ at 100 kV/cm. The leakage current was found to be closely related to the morphology and composition of the BFO films. BFO films showed poor P-E hysteresis loops due to high leakage current.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.16-23
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• 2009

The porous pellets were prepared from porphyry by slurry foaming method. The effect of sintering temperatures on pore structure of porous porphyry pellets with different extension ratio ($E_R$) was investigated by specific surface area, water absorption and porosity, which changed with sintering temperatures. When the sintering temperatures increased from $975^{\circ}C$ to $1075^{\circ}C$, specific surface area and water absorption of the all samples decreased. In case of the sample with an equal sintering temperature, $E_R=3.0$ pellets had little influence on pore structure compared to the $E_R=2.0$ pellets. As a results, it was shown by SEM that facilitated formation of micro pores at $E_R=2.0$ pellets shrunk increasingly after sintering process. At $E_R=3.0$ and sintering temperature at $1025^{\circ}C$, optimum conditions of the porous porphyry porous pellets was found. Also, Escherichia coli removal efficiency of the silver-containing porphoyry porous pellets was measured for the feasibility as a antibacterial media. The antibacterial activity of prepared silver-containing sample was maintained above 90% for 40 days.

• Advanced Composite Materials
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• v.18 no.4
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• pp.315-326
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• 2009

PCC (precipitated calcium carbonate) and ground calcium carbonate have been widely used in alkaline papermaking. Unfortunately, although increasing filler level in papers can improve the paper properties such as brightness, opacity, stiffness gloss, smoothness, porosity, and printability, as well as decrease cost, some strength of the paper is negatively affected. In this research, needle-like aragonite was synthesized using $Ca(OH)_2$ and $CO_2$ as reactants in the presence of $MgCl_2$ and characterized with scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The physical and optical properties of the paper handsheets containing these needle-like aragonite fillers were evaluated. Results indicated that tensile strength, Z-direction tensile strength and folding endurance of the paper were improved by the needle-like aragonite crystals compared to the paper using commercial PCC (precipitated calcium carbonate) as filler. The stiffness of the paper handsheet on the machine direction was increased, but no evident difference in the cross direction was found. The improvement of paper strength mainly resulted from the twining effect between the aragonite whiskers and paper fibers. The optical properties of the paper were slightly decreased with the use of the needle-like aragonites compared to commercial PCC. These results suggest that paper cost can be decreased by increasing the content of needle-like aragonite filler while paper strength will not be decreased compared to PCC filler.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.134-141
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• 2013

Pond ash produced from Seochun Power Station was quantitatively characterized to manufacture geopolymers with a range of Si/Al compositional ratios. Mix consistency was kept nearly constant for comparing the compressive strengths of geopolymers. The amorphous composition of coal ash was determined using XRF and quantitative X-ray diffraction. Different mix compositions were used in order to achieve Si/Al ratios of 2.0, 2.5 and 3.0 in the geopolymer binder. Geopolymers synthesized from coal ash with a Si/Al ratio of 3.0 exhibited the highest compressive strength in this study. It was found that geopolymers activated with aluminate produced different microstructure from that of geopolymers activated with silicate. High silica in alkali activators produced the fine-grained microstructure of geopolymer gel. It was also found that high compressive strength was related to low porosity and a dense, connected microstructure. The outcome of the reported experiment indicates that quantitative formulation method made it possible to choose suitable activators for achieving targeted compositions of geopolymers and to avoid efflorescence.

• Journal of the Korean Ceramic Society
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• v.42 no.1
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• pp.37-42
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• 2005

Lightweight aggregate was made using glass abrasive sludge and graphite in this study. This study tried to draw the correlation between lightweight aggregate's properties and internal pore. The precursor was made by added different graphite contents and was burned for 20 min. at $700^{circ}C$ and $800^{circ}C$. The volume change of aggregate was checked at before and after homing, and confirmed that the homing temperature effected more than expanding agent on volume change. The size and area of pore in aggregate increased according to the amount of expanding agent and homing temperature but it didn't bring about big effect above $1\%$ of expanding agent. The absorbtion ratio, thermal conductivity and porosity have a high correlation, so each coefficient of correlation showed above $0.8\pm$.