• Journal of Korean Society of Forest Science
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• v.99 no.3
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• pp.353-358
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• 2010

In this study, we investigated the relationship of tree-ring growth with total nitrogen content, and stable carbon and nitrogen isotopes from the core samples of Pinus koraiensis (35-year-old). Annual ring width showed significant positive correlations with the ${\delta}^{13}C$ (P=0.003). The total nitrogen content (P=0.024), and the ${\delta}^{13}C$ content was also correlated with total nitrogen content (P=0.038), indicating that the growth of P. koraiensis was stimulated as the contents of both ${\delta}^{13}C$ and total nitrogen were increased. On the other hand, the less the ${\delta}^{15}N$ content and the C/N ratio were, the larger the annual ring width was. Moreover the families with relatively better growth performance contained the higher levels of ${\delta}^{13}C$ in the xylem compared to other families. These results suggest that the ${\delta}^{13}C$ and total nitrogen contents are the important determinants in the growth performance of P. koraiensis.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.37-43
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• 2014

Exhaust emissions were studied as a function of gasoline olefin composition in two vehicles-MPI and GDi engine equipped vehicles. Three different gasolines were tested which varied in olefin contents-12, 16 and 20 vol%. Exhaust emissions in two vehicles were affected by changes in gasoline olefin composition. Responses to changes in olefins were similar in both vehicles : reducing olefins lowered emissions of NOx and CO. Measured exhaust emissions included total hydrocarbons (THC), oxides of nitrogen (NOx), carbon monooxide(CO), carbon dioxide($CO_2$), formaldehyde, benzene, toluene, xylene, 1,3-butadiene and acetylene.

• Carbon letters
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• v.12 no.1
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• pp.31-38
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• 2011

This study experimentally investigated dicyclohexylammonium 2-cyanoacrylate (CA) as a potential comonomer for polyacrylonitrile (PAN) based carbon fiber precursors. The P(AN-CA) copolymers with different CA contents (0.19-0.78 mol% in the feed) were polymerized using solution polymerization with 2,2-azobis(isobutyronitrile) as an initiator. The chemical structure and composition of P(AN-CA) copolymers were determined by proton nuclear magnetic resonance and elemental analysis, and the copolymer composition was similar to the feeding ratio of the monomers. The effects of CA comonomer on the thermal properties of its copolymers were characterized differential scanning calorimetry (DSC) in nitrogen and air atmospheres. The DSC curves of P(AN-CA) under nitrogen atmosphere indicated that the initiation temperature for cyclization of nitrile groups was reduced to around $235^{\circ}C$. The heat release and the activation energy for cyclization reactions were decreased in comparison with those of PAN homopolymers. On the other hand, under air atmosphere, the P(AN-CA) with 0.78 mol% CA content showed that the initiation temperature of cyclization was significantly lowered to $160.1^{\circ}C$. The activation energy value showed 116 kJ/mol, that was smaller than that of the copolymers with 0.82 mol% of itaconic acids. The thermal stability of P(AN-CA), evidenced by thermogravimetric analyses in air atmosphere, was found higher than PAN homopolymer and similar to P(AN-IA) copolymers. Therefore, this study successfully demonstrated the great potential of P(AN-CA) copolymers as carbon fiber precursors, taking advantages of the temperature-lowering effects of CA comonomers and higher thermal stability of the CA copolymers for the stabilizing processes.

• Journal of Forest and Environmental Science
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• v.31 no.1
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• pp.14-23
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• 2015

In this study, we investigated the effects of three land uses on soil properties in two soil layers; surface soil (0~15 cm) and subsoil (15~30 cm). Soil samples were collected from planted forest, barren lands and cultivated lands from different areas in Chittagong Cox's Bazar and analyzed for some physical and chemical properties. Results showed that soil textural class varied from sandy clay loam in planted forest and barren land site to sandy loam in cultivated soils. Maximum water holding capacity was higher in forest followed by barren land and the lowest in cultivated lands. At both soil depths, soils of cultivated land showed the highest values of bulk density (1.42 to $1.50g\;cm^{-3}$), followed by barren lands (1.37 to $1.46g\;cm^{-3}$) and the least (1.32 to $1.45g\;cm^{-3}$) in forest soils. Total porosity decreased with depth ranging from 40.24% to 41.53% in subsoils and from 42.04 to 43.23% in surface soil of cultivated and of planted forest sites respectively. The result further revealed that organic carbon (OC) and total nitrogen (TN) contents were higher in the planted forest soil than in other two land uses. The soils of all land uses under study are acidic in nature and the lowest pH was found in both surface and subsoils of barren land. Cultivated soil contained the highest amount of available P, Ca, Mg and K in both surface soil and subsoils. In contrast, barren site had the lowest contents of available P, Ca, Mg and K in both layers. The soil organic carbon (SOC) and total N storage were higher in planted forest than in barren and cultivated land uses.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.2
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• pp.169-179
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• 1998

This paper was performed to estimate interrelations between humus level of sediments and nutrient release from sediments in Dae-cheong reservoir. For investigations, sediments were sampled in June and October, in 1997 at fish farms, embayment, and the main stream of Dae-cheong reservoir. Items for investigation are as follows; water content, weight loss on ignition(IG), porosities of sediments, contents of element such as hydrogen, nitrogen, carbon, and nutrient release rates. Water contents and porosities were measured to conjecture the physical trait and grain size trait. Weight loss on ignition was measured to determine the contents of organic substance. For determination of the humus level of sediments, carbon and nitrogen contents were measured by elemental analyzer. As a result of elemental analysis, C/N ratio was determined in the range of $3.0\~13.1$. From the elemental analysis, humus level of Dae-cheong reservoir sediment was estimated from mesohumic state to oligotrophic state. For the determination of nutrient release rate, $PO_4-P$ and $NH_4-N$ concentrations of interstitial water and overlying water were measured. By using the concentration difference between interstitial water and overlying water and using the Fick's diffusion law, the release rates of phosphorus and nitrogen from the sediment samples were calculated. Release rates of nutrients which directly influence to the water quality were $0.05\~8.63mgP/m^2day$ and $4.99\~36.56mgP/m^2day$. It was found that release rate was measured higher in the 1st sampling period than in the 2nd sampling period. For the determination of phosphorus content in sediment, TPs were measured in 807\~1542{\mu}g/g$ in the 1st samling period and $677\~5238{\mu}g/g$ in the End samling period. Phosphorus release rate and phosphorus content were not interrelated each other.

• Journal of Electrochemical Science and Technology
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• v.8 no.4
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• pp.338-343
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• 2017

Activated carbon has lower electrical conductivity and reliability than other carbonaceous materials because of the oxygen functional groups that form during the activation process. This problem can be overcome by doping the material with heteroatoms to reduce the number of oxygen functional groups. In the present study, N, F co-doped activated carbon (AC-NF) was successfully prepared by a microwave-assisted hydrothermal method, utilizing commercial activated carbon (AC-R) as the precursor and ammonium tetrafluoroborate as the single source for the co-doping of N and F. AC-NF showed improved electrical conductivity ($3.8\;S\;cm^{-1}$) with N and F contents of 0.6 and 0.1 at%, respectively. The introduction of N and F improved the performance of the pertinent supercapacitor: AC-NF exhibited an improved rate capability at current densities of $0.5-50mA\;cm^{-2}$. The rate capability was higher compared to that of raw activated carbon because N and F codoping increased the electrical conductivity of AC-NF. The developed method for the co-doping of N and F using a single source is cost-effective and yields AC-NF with excellent electrochemical properties; thus, it has promising applications in the commercialization of energy storage devices.

• Korean Journal of Materials Research
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• v.15 no.10
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• pp.632-638
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• 2005

To investigate the effect of Mo and Cu contents on tensile strength of cold drawn stainless steel 304H wires, metallographical and mechanical tests were performed for the wire specimens drawn to different drawing strains at room temperature. It was confirmed that the contents of Mo ana Cu have little influence on the tensile strength of drawn specimens, even though the strain induced martensite transformation decreased with increasing the contents of Mo and Cu. These results were explained by the strengthening of the formed martensite itself due to the solid solution effect of interstitial solutes, carbon and nitrogen. The contents of these elements were slightly higher in the specimens containing additionally added Mo and Cu.

• Resources Recycling
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• v.25 no.5
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• pp.75-83
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• 2016

AlN powder was prepared by carbon reduction and subsequent nitridation method through the scale-up experiments of 0.7 ~ 1.5 kg per batch. AlN powder was synthesized using the mixture of $Al_2O_3$ powder and carbon black at $1,550{\sim}1,750^{\circ}C$ for 0.5 ~ 4 hours under nitrogen atmosphere (flow rate of nitrogen gas: $10{\sim}40{\ell}/min$) at $2.0{\times}10^{-1}Torr$. Experimental results showed that $1,700{\sim}1,750^{\circ}C$ for the reaction temperature, 3 hr for reaction time, and $40{\ell}/min$ for the flow rate of nitrogen gas were the optimal conditions. Also, in order to remove carbon in the synthesized AlN, the remained carbon was removed at $650{\sim}750^{\circ}C$ for 1 ~ 2 hr using horizontal tube furnace. The results showed that 1 : 3.2 mol ratio of $Al_2O_3$ to carbon black, reaction temperature of $750^{\circ}C$, reaction time of 2 hours, rotating speed of 1.5 rpm under atmosphere condition were the optimal conditions. Under these conditions, high-purity AlN powder over 99% could be prepared: carbon and oxygen contents of the AlN powder were 835 ppm and 0.77%, respectively.

• Carbon letters
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• v.7 no.1
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• pp.34-41
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• 2006

The objective of this paper is to compare the variation of surface properties by hydrochloric acid pre-treatment and of metallic potassium and their salts loading effect for activated carbon after surfaces transformation by acid. From the results of nitrogen adsorption, each isotherm shows a distinct knee band, which is closely related to the characteristic of microporous carbons with capillary condensation in micropores. In order to present the causes of the differences in surface properties and $S_{BET}$ after the samples were treated with hydrochloric acid, pore structure and surface morphology are investigated by adsorption analysis. X-ray diffraction (XRD) patterns indicate that activated carbons show better performance for metallic potassium and potassium salts by pre-treatment with hydrochloric acid. Scanning electron microscopy (SEM) pictures of potassium/activated carbon particles provide information about the homogeneous distribution of metal or metal complex on the surface. For the chemical composition microanalysis for potassium treatment of the activated carbon pre-treated with hydrochloric acid, samples were analyzed by energy disperse X-ray (EDX). Finally, the type and quality of oxygen groups are determined from the method proposed by Boehm. A positive influence of the acidic groups on the carbon surface by acid treatment is also demonstrated by an increase in the contents of potassium salts with increasing of acidic groups calculated from Boehm titration.

• Journal of Ecology and Environment
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• v.42 no.4
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• pp.163-173
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• 2018

Background: Deforestation and degradation are currently affecting the ecosystem services of forests. Among the ecosystem services affected by deforestation and degradation are the amount of soil organic carbon (SOC) and total nitrogen (TN) stored in forest soils which have greater impacts in global climate change. This study aimed at examining the amount of SOC and TN in the forest fragments which were separated from the continuous tracts of forests of Jibat and Chillimo through fragmentation processes over four decades. Methods: We have sampled soils from 15 forest fragments of Chillimo and Jibat in the central highlands of Ethiopia. The soil samples obtained in two separate soil depths (0-30 and 30-60 cm) were bulked, dried, and sieved for analysis. Results: Our results have shown that the two sites (Jibat and Chillimo forest fragments) differed in their SOC and TN contents. While the values for Jibat were found to be 29.89 Mg/ha of SOC and 2.84 Mg/ha for TN, it was 14. 06 Mg/ha of SOC and 1.40 Mg/ha for TN for Chillimo. When all forest fragment soil samples were bulked together, Jibat site had twice the value of SOC and TN than Chillimo. When disaggregated on the basis of each fragments, there existed differences in SOC (1.86 Mg/ha and 42.15 Mg/ha) and TN (0.24 Mg/ha and 4.23 Mg/ha) values. Among the forest fragments, fragment four ($F_4$) had the highest Relative Soil Improvement Index (RSII) value of 3826.82% and fragment fifteen ($F_{15}$) had the lowest RSII value (726.87%) which indicated that the former had a better quality of soil properties than the latter. Conclusion: SOC and TN differed across sampled fragments and sites. Variations in soil properties are the reflections of inherent soil parent material, aboveground vegetation, human interferences, and other physical factors. Such differences could be very important for identifying intervention measures for restoration and enhancing ecosystem services of those fragments.