• Journal of applied mathematics & informatics
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• v.26 no.3_4
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• pp.751-755
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• 2008

Formanek([2]) proved that $M_n(K)$, the matrix algebra has a nontrivial central polynomial when char K = 0. Also Razmyslov([3]) showed the same result using the essential weak identity. In this article we explicitly compute Formanek's central polynomial for $M_2(\mathbb{C})$ and $M_3(\mathbb{C})$ and classify the coefficients of the central polynomial.

• Journal of the Korean Mathematical Society
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• v.50 no.6
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• pp.1213-1222
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• 2013

This paper deals with sufficiency conditions for irreducibility of certain induced modules. We also construct irreducible representations for a group G over a field $\mathbb{K}$ where the group G is a semidirect product of a normal abelian subgroup N and a subgroup H. The main results are proved with the assumption that char $\mathbb{K}$ does not divide |G| but there is no assumption made of $\mathbb{K}$ being algebraically closed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.174-184
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• 1997

Activated carbons were prepared from palm chars by steam activation. The effect of the activation temperature and time, steam concentration and flux on the n -butane adsorption properties were investigated on the basis of surface area, pore analysis and n-butane adsorption. The amount of n -butane adsorption increased with steam concentration and steam flux at higher activation temperature to the $900^{\circ}C$, however this tendancy on the activated carbons were not observed at the temperature above $900^{\circ}C$, It was shown that surface area was 978 $\textrm{m}^2$/g, average pore size was 9.3 $\AA$ and n-butane adsorption was 5.9 g /100ml in the activated carbons, prepared at $900^{\circ}C$, 185 minutes.

• Journal of Korean Society of Forest Science
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• v.101 no.4
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• pp.567-573
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• 2012

This study was carried out to examine the effect of soil amendment treatments [(organic fertilizer: 20 kg $tree^{-1}$; compound fertilizer+wood-char fertilizer: compound fertilizer 4 kg $tree^{-1}$+wood-char 2 kg $tree^{-1}$; lime fertilizer: 3 kg $tree^{-1}$; mixed fertilizer: compound fertilizer 1 kg $tree^{-1}$+organic fertilizer 10 kg $tree^{-1}$+wood-char 1 kg $tree^{-1}$; control (no fertilizer)] on flowering and fruit characteristics in chestnut (Castanea crenata S. et Z.) orchards in Jinju and Sancheong, Gyeongsangnam-do. Diameter of fruiting shoot increased generally after soil amendment treatments compared with the control, while number of leaf, female and male flowers were not affected by the treatments. Nut weight increased after soil amendment treatments in Jinju, but was not affected by the treatments in Sancheong. There was a positive correlation between soil pH (r=0.91) or exchangeable $Ca^{2+}$ (r=0.99) and nut weight in Jinju and a positive correlation (r=0.97) between organic carbon content and soluble solid concentration, while a negative correlation (r=-0.92) between exchangeable $Mg^{2+}$ and soluble solid concentration of nuts in Jinju. However, the nut weight and soluble solid concentration in Sancheong were not correlated with soil properties. The results indicate that the characteristics of flowering and nuts in chestnut orchards depend on soil properties after soil amendment treatments between regions which show better responses on poor sites than on good sites.

• Bulletin of the Korean Mathematical Society
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• v.50 no.5
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• pp.1651-1657
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• 2013

Let R be a prime ring, I a nonzero ideal of R, $d$ a derivation of R, $m({\geq}1)$, $n({\geq}1)$ two fixed integers and $a{\in}R$. (i) If $a((d(x)y+xd(y)+d(y)x+yd(x))^n-(xy+yx))^m=0$ for all $x,y{\in}I$, then either $a=0$ or R is commutative; (ii) If $char(R){\neq}2$ and $a((d(x)y+xd(y)+d(y)x+yd(x))^n-(xy+yx)){\in}Z(R)$ for all $x,y{\in}I$, then either $a=0$ or R is commutative.

• Journal of the Korean Mathematical Society
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• v.46 no.5
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• pp.997-1005
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• 2009

Let R be a prime ring, I a nonzero ideal of R, d a derivation of R and n a fixed positive integer. (i) If (d(x)y+xd(y)+d(y)x+$yd(x))^n$ = xy + yx for all x, y $\in$ I, then R is commutative. (ii) If char R $\neq$ = 2 and (d(x)y + xd(y) + d(y)x + $yd(x))^n$ - (xy + yx) is central for all x, y $\in$ I, then R is commutative. We also examine the case where R is a semiprime ring.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.5
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• pp.381-389
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• 2014

$NH_4$-N contents in the soil treated were relatively high in the initial stages, but rapidly decreased at 124 days after treatment. $NO_3$-N contents were shown to be opposite patterns of $NH_4$-N contents. $CO_2$ emissions in the non-treatment and Carbonized rice hull treatment with application of NPK fertilizers decreased by 43.7 and 21.9% relative to the non-application of NPK fertilizer plot except 5.4% increasement in the pig manure compost treatment. $N_2O$ emissions of the non-application, the Expander rice hull application, and bio-char treatment increased by 90, 25, and 21.4%, respectively, but decreased by 54.2% in the pig manure compost treatment applied with NPK fertilizers compared with the NPK fertilizer non-application plot.

• Carbon letters
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• v.4 no.2
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• pp.57-63
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• 2003

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and $Et_3N$ and $NH_4OH$ as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using $Et_3N$ as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 $m^2/g$, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with $CO_2$ leads to the formation of activated carbon with a wide range of surface area (503~1119 $m^2/g$) with both of these resins. The maximum pore volume percentage was obtained in 3-20 ${\AA}$ region by physical activation method.

• Fire Science and Engineering
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• v.28 no.5
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• pp.71-79
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• 2014

This study was performed to test the combustive properties of Medium Density Fibreboards (MDFs) treated with chemicals of the bis-(dimethylaminomethyl) phosphinic acid (DMDAP), N,N-dimethylethylenediaminomethyl-bis-phosphonic acid (DMDEDAP), piperazinomethyl-bis-phosphonic acid (PIPEABP), and methylpiperazinomethyl-bis-phosphonic acid (MPIPEABP). MDFs were painted in three times with 15 wt% solution of the bis-(dimethylaminomethyl) phosphinic acid and alkylenediaminoalkyl-bis-phosphonic acids at the room temperature, respectively. After drying MDF treated with chemicals, combustive properties and volatile organic compounds (VOCs) contents were examined by the cone calorimeter (ISO 5660-1), test for flame retardant (NEMA Notice No. 2012034), and gas chromatography (KS M ISO 11890-2), respectively. It was indicated that the MDFs treated with chemicals showed the longer time to combustion time (CT) = (442~492) s than that of virgin plate by reducing the burning rate except for CT treated with DMDAP. In adition, the MDFs treated with chemicals showed both of the higher char area (44.33~61.33) kg/kg and char length (10.33~11.67) cm than those of virgin plate. Especially, the MDFs treated with chemicals showed the higher mean volatile organic compounds (VOCs) (0.188~0.333) g/L than that of virgin plate within the prescribed limits. Thus, It is supposed that the combustion- retardation properties were improved by the partial due to the treated chemicals in the virgin MDF.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.235-238
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• 2005

Sulfonated poly(ether sulfone) copolymers (PESs) were synthesized using hydroquinone 2-potassium sulfonate (HPS) with other monomers (bisphenol A and 4-fluorophenyl sulfone). PESs with different $mole\%$ of hydrophilic group were prepared by changing the mole ratio of HPS in the polymerization reaction. The chemical structure and the thermal stability of these polymers were characterized by using $^1H-NMR$, FT-IR and TGA techniques. The PES 60 membrane, which has $60 mole\%$ of HPS unit in the polymer backbone, has a proton conductivity of 0.091 S/cm and good insolubility in boiling water. The TGA showed that PES 60 was stable up to $272^{\circ}C$ with a char yield of about $29\%\;at\;900^{\circ}C\;under\;N_2$ atmosphere. To investigate the single cell performance, the catalyst coated PES 60 membrane was used and a single cell test was carried out using $H_2/O_2$ gases as fuel and oxidant at various temperatures. We observed that the cell performance was enhanced by increasing the cell temperature. A current density of $1400 mA/cm^2$ at 0.60 V was obtained at $70^{\circ}C$.