• Journal of Environmental Science International
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• v.32 no.1
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• pp.47-55
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• 2023

This study evaluated the biochemical methane potential (BMP) of primary sludge, secondary sludge, and food waste in batch anaerobic mono-digestion tests, and investigated the effects of mixture ratio of those organic wastes on methane yield and production rate in batch anaerobic co-digestion tests, that were designed based on a simplex mixture design method. The BMP of primary sludge, secondary sludge and food waste were determined as 234.2, 172.7, and 379.1 mL CH₄/g COD, respectively. The relationships between the mixing ratio of those organic wastes with methane yield and methane production rate were successfully expressed in special cubic models. Both methane yield and methane production rate were estimated as higher when the mixture ratio of food waste was higher. At a mixing ratio of 0.5 and 0.5 for primary sludge and food waste, the methane yield of 297.9 mL CH₄/g COD was expected; this was 19.4% higher than that obtained at a mixing ratio of 0.3333, 0.3333 and 0.3333 for primary sludge, secondary sludge, and food waste (249.5 mL CH₄/g COD). These findings could be useful when designing field-scale anaerobic digersters for mono- and co-digestion of sewage sludges and food waste.

• Journal of the Korean Ceramic Society
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• v.34 no.5
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• pp.505-511
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• 1997

The effects of sintering atmospheres(air, O2, N2) on the sintering and microwave dielectric properties of (1-x)CaTiO3-xLaAlO3 system was investigated. The sintered density of (1-x)CaTiO3-xLaAlO3 under air atmosphere increased linearly with increasing x, but it decreased in the range of x>0.5 under O2 atmosphere and x>0.6 under N2 atmosphere in spite of the increament of the smaller La(1.06$\AA$) and Al(0.5 $\AA$) ion than Ca(0.99$\AA$) and Ti(0.6$\AA$). In case of the air sintering atmosphere of (1-x)CaTiO3-xLaAlO3 the two phases of orthorhombic and rhombohedral crystal system were coexisting, and the XRD peak of rhombohedral crystalsystem was to be higher with increasing x. However, the sintering atmosphere of O2 and N2 made the monophasic crystal system of orthorhombic keep up by x=0.5 and x=0.6, respectively, and it transformed to pseudo-cubic crystal system in x>0.5 and x>0.6. The XRD peak intensity of (1-x)CaTiO3-xLaAlO3 was to be gradually higher with increasing x under the air atmosphere of sintering. Whereas, its XRD peak intensity increased till x=0.6 but decreased with increasing x in the range of x>0.6 under O2 and N2 atmosphere. The relative dielectric constant of (1-x)CaTiO3-xLaAlO3 sintered under air atmosphere decreased linearly and the Q.f0 value increased according as x increased. On the other hand, the relative dielectric constant of (1-x)CaTiO3-xLaAlO3 under O2 and N2 atmosphere decreased in the range of x$\leq$0.5 with increasing x, but increased rapidly in the range of x$\geq$0.6. And the Q.f0 value increased till x=0.6 but decreased in the range of x>0.6 with increasing x. The temperature coefficient of resonant frequency had no relation to sintering atmosphere.

• Journal of Korea Spatial Information System Society
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• v.4 no.2 s.8
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• pp.55-64
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• 2002

VEfficient generation of road data is one of the most important issues in GIS (Geographic Information System). In this paper, we propose a hybrid approach for automatic generation of road data by combining mobile mapping and image processing techniques. Mobile mapping systems have a form of vehicle equipped with CCD camera, GPS, and INS. They can calculate absolute position of objects that appear in acquired image by photogrammetry, but it is labor-intensive and time-consuming. Automatic road detection methods have been studied also by image processing technology. However, the methods are likely to fail because of obstacles and exceptive conditions in the real world. To overcome the problems, we suggest a hybrid method for automatic road generation, by exploiting both GPS/INS data acquired by mobile mapping system and image processing algorithms. We design an estimator to estimate 3-D coordinates of road line and corresponding location in an image. The estimation process reduces complicated image processing operations that find road line. The missing coordinates of road line due to failure of estimation are obtained by cubic spline interpolation. The interpolation is done piecewise, separated by rapid change such as road intersection. We present experimental results of the suggested estimation and interpolation methods with image sequences acquired by mobile mapping system, and show that the methods are effective in generation of road data.

• Applied Chemistry for Engineering
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• v.8 no.6
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• pp.954-959
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• 1997

The solid solutions of the $Sr_{1-X}M_XFeO_{3-y}$ (x=0.1, 0.2, 0.3, 0.4, 0.5, M=Ca) system having perovskite structures were prepared in air by heat treatment at 1473 K for 18hr. X-ray diffraction assigns cubic system for all the samples and shows that the lattice volume of each system decreases with increasing x value until x=0.3, but increases abruptly from x=0.4. The mole fractions of $Fe^{4+}$ ion($\tau$ value), the amounts of oxygen vacancy (y value) and finally nonstoichiometric chemical formulas for each composition were determined from Mohr salt analysis. TG/DTA thermal analysis (temperature range: 300~1173K) exhibits that 3-y values of the samples having x=0.1 and 0.2, decrease with temperature and increase almost reversibly with decreasing temperature. The samples of $x{\geq}0.3$, however, didn't show the reversible weight change and the 3-y values of them were nearly 2.5 in cooling process. Conductivities of each sample were varied within the semiconductivity range at relatively low temperature. And the conductivity at constant temperature decreases steadily with x value. The conduction mechanism of this ferrite system may be proposed as a hopping model of conducting electrons between the mixed valence states. At high temperature semiconductivity of each sample changed into metallic property.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.211-218
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• 1991

A series of samples in the $Nd_{-x}Sr_{x}CoO_{3-y}$ system (x = 0.00, 0.25, 0.50, 0.75 and 1.00) have been produced by heating the reactants at 1200${\circ}$C under atmospheric pressure. The solid solutions were analysed by X-ray diffraction spectra, thermal analysis, and SEM micrographs. X-ray powder diffraction assigns the compositions of x = 0.00, 0.25, 0.50 and 0.75 to the cubic system and the composition of x = 1.00 to the orthorhombic system. The reduced lattice volume is increased with increasing x values in the system. The mole ratio of $Co^{4+}$ or ${\tau}$ values are determined by the Iodometric titration method and are maximum at the composition of x = 0.50. The magnetic measurement shows that a ferromagnetism is appeared in the compositions of x = 0.00, 0.25, 0.50 and 0.75 and then an antiferromagnetism in the composition of x = 1.00. The measurement of the electrical conductivity shows that the semiconductivity is appeared in the composition of x = 0.00, 0.25 and 1.00 and the metallic conductivity in the composition of x = 0.50 and 0.75. The magnetic and electrical properties of the samples are discussed with the nonstoichiometric chemical formulas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.587-591
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• 2019

Fine dust aerated in the atomsphere penetrates our lungs and blood lines through respiratory. Recent fine dust problems in Korea leads to development of various air purifiers. The researchers used this to study systems that could replace chemical filters. In order to compare the effect of the reduction of moss and conventional chemical filter(Hepa), a 1 cubic meter cube was prepared and the amount of the concentration of fine dust reduction was compared under controlled environment. Under the high concentration of fine dust, a test was done to figure out the reduction rate of the fine dust concentration by using air purification system with moss, hepa, and no filter. The air purification system(moss, hepa, and no filter) were operated 90 times in total, 30 times each. The test explains that the reduction of the fine dust amount and the rate of fine dust concentration. The results illustrate that the reduction of the amount fine dust was 138.93 after using air purification system with moss filter. In contrast, the usage of air purification system with hepa filter reduced the amount of fine dust to 76.57. And the air purification with no filter shows that the slight reduction of fine dust amount at 0.10. In the rate of fine dust concentration, moss filter was significantly higher than that of hepa, no filter (0.2379, 0.1298 and 0.0063 each). The results have confirmed that moss is effective in reducing fine dust concentration, and it is expected that with further improvement it can be used as a means to replace or supplement existing chemical filters in air purifier.

• Journal of the Korean Chemical Society
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• v.39 no.7
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• pp.508-512
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• 1995

A series of samples in the $Eu_{1-x}Sr_xCoO_{3-y}$ system has been prepared by heating the proper amount of reactant mixture to 1150$^{\circ}C$ under an ambient atmosphere, and the solid solutions are identified by X-ray powder diffraction analysis. The crystal system of samples for the compositions of x=0.00 and 0.25 are found to be orthorhombic whose local symmetry is similiar to the distorted octahedra with orthoferrite type one, whereas those of x=0.50 and 0.75 to be the cubic system, and that of x=1.00 to the orthorhombic similiar to be the brownmillerite type. The amount of $Co^{4+}$ ion (${\tau}$ value) is maximized at the composition of x=0.50, and the oxygen vacancies increase with the x value. The nonstoichiometric chemical formula of each compound could be determined from the mole ratio of $Co^{4+}$ ion and oxygen vacancies. The $Co^{3+}$ ion located in octahedral site has spin transition from low spin to high spin states with increasing temperature. Therefore, the effective magnetic moment of each samples obtained from the magnetic measurement is increased with the increasing temperature. The $EuCoO_{3.00}$ has strong antiferromagnetic interaction between the neighboring $Co^{3+}$ ions through the intermediate oxygen ions. With the increasing ${\tau}$ value, the absolute {\theta}_p$ value is decreased by the ferromagnetic interaction of $Co^{3+}-O^2-Co^{4+}$ and thus the {\theta}_p$ has positive value at x=0.50.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.67-74
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• 1996

The binary phase equilibrium experiments of carbon dioxide/1,2,3,4 ${\alpha}$-tetrahydro-1-naphthol(${\alpha}$-tetralol) system were conducted to get phase equilibrium and mixture density data at 313.2K, 343.2K and 373.2K and within pressure ranges of 6.0 MPa to 35.0MPa. The phase equilibrium apparatus was type that circulated the vapor and liquid phase, the expended volume measuring system was adopted to microsampling technique for the analysis. The phase equilibrium and mixture density data were obtained for carbon dioxide/${\alpha}$-tetralol system from liquid and vapor phase. The mole fraction of carbon dioxide in liquid phase decreases and the mole fraction of ${\alpha}$-tetralol in vapor phase increases at constant pressure according to increment of temperature, and both the densities of the vapor and liquid phase approach to the mixture critical density as the pressure increases at any temperature. For she thermodynamic analysis, the experimental data were correlated with Peng-Robinson equation in cubic equation of state and compared to theoretical values of carbon dioxide/${\alpha}$-tetralol system. The AAD result was in the range of 1.08%~8.93% in the case of K(1), and was in the range of 45.71%~72.34% in the case of K(2).

• Journal of Korean Society of Forest Science
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• v.70 no.1
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• pp.84-90
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• 1985

The objective of this study is to analyze the market structure and price formation status of imported log from overseas which has leadership of timber price decision mechanism in Korea. The results obtained are as follows; 1) The 53 percents of the total 134 log importing companies are the small scale companies which import less than ten thousand cubic meters per year, and are mainly aimed to do agent task of importing log. 2) The market structure of imported log formed high level 01 oligopolistic structure, but did not make excess profit of oligopoly because of excess import. 3) The bargaining power of Korea on the price decision process in the overseas log exporting market is very weak, because the market has the bilateral oligopoly structure, and the non-systematic importing behavior of Korean log importing companies make the bargaining power of Korea more weak. 4) It is analyzed that Korean domestic marketing system is comperatively simple, but reasonable marketing system is not established because of the disorder of the marketing behavior. From the results obtained above, it is proposed that the government has to establish the general institutional system to control the supply-demand and marketing problems of imported log, in order to establish the rational structure of market and price decision system of imported log.

• Korean Journal of Materials Research
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• v.9 no.7
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• pp.701-706
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• 1999

The crystal structure and magnetic properties of magnetic oxide system (F $e_2$ $O_3$)$_{5}$(A $l_2$ $O_3$)$_{4-x}$(G $a_2$ $O_3$)$_{x}$)SiO has been studied using X-ray diffraction and Mossbauer spectroscopy The changes of magnetic structure by the Ga ion substitution and the temperature variation have been investigated using Mossbauer spectroscopy, and the results are compared with those of the SQUIB measurements. Results of X-ray diffraction indicated that the crystal structures of the system change from a cubic spinel type to an orthorhombic via the intermediate region. This magnetic oxide system seems to be new kind of spinel type ferrites containing high concentration of cation vacancies. Various and complicated Mossbauer spectra were observed in the samples (x>0.2) at temperatures lower than room temperature. This result could be explained by freezing of the superparamagnetic dusters. On cooling and substitution, magnetic states of the system show various and multicritical properties. Unexpected dip in magnetization curves below 50K was observed in SQUID measurements. It was interpreted as an effect of spin canting including spin freezing or collective spin behavior.ior.r.