• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.3
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• pp.25-31
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• 1977

Fe V spinels were prepared by sintering the well-ground stoichiometric mixtures of Fe O and V O at 1,10$0^{\circ}C$ under H -CO atmosphere. The activation energy for electrical conduction decreases with increasing amount of iron. The tendency of activation energy depending on the amount of iron contained clarifies that the electrical condction of the spinel is mainly due to electron hopping between Fe and Fe ions at B sites. In the experiment for negative resistance characteristics, the threshold voltage (Vth) for the samples is related to ambient temperature, thickness and raising rate of applied voltage. Vth decreases as temperature increases while Vth increases linearly with thickness and Vth increases linearly with the raising rate of applied voltage in semi-logarithmic scale. These results lead to a conclusion that current paths mainly formed by thermal breakdown are ascribed to the negative resistance phenomena. Applying this property, these vanadium iron spinels may be used for switching elements.

• Journal of Environmental Science International
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• v.12 no.9
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• pp.997-1004
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• 2003

The objective of this research was to test whether, under controlled laboratory conditions, hybrid SNCR/SCR process improves N $O_{x}$ removal efficiency in comparison with the SNCR only. The hybrid process is a combination of a redesigned existing SNCR with a new downstream SCR. N $O_{x}$ reduction experiments using a hybrid SNCR/SCR process have been conducted in simple NO/N $H_3$/ $O_2$ gas mixtures. Total gas flow rate was kept constant 4 liter/min throughout the SNCR and SCR reactors, where initial N $O_{x}$ concentration was 500 ppm in the presence of 5% or 15% $O_2$. Commercial catalysts, $V_2$ $O_{5}$ -W $O_3$-S $O_4$/Ti $O_2$, were used for SCR N $O_{x}$ reduction. The residence time and space velocity were around 1.67 seconds and 2,400 $h^{-1}$ or 6000 $h^{-1}$ in SNCR and SCR reactors, respectively. N $O_{x}$ reduction of the hybrid system was always higher than could be achieved by SNCR alone at a given value of N $H_{3SLIP}$. Optimization of the hybrid system performance requires maximizing N $O_{x}$ removal in the SNCR process. An analysis based on the hybrid system performance in this lab-scale work indicates that a equipment with N $O_{xi}$ =500 ppm will achieve a total N $O_{x}$ removal of about 90 percent with N $H_{3SLIP}$ $\leq$ 5 ppm only if the SNCR N $O_{x}$ reduction is at least 60 percent. A hybrid SNCR/SCR process has shown about 26∼37% more N $O_{x}$ reduction than a SNCR unit process in which a lower temperature of 85$0^{\circ}C$ turned out to be more effective.be more effective.

• Resources Recycling
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• v.7 no.4
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• pp.64-75
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• 1998

The purpose of this study is to produce high putity composite powder composed of Fe-oxide, Mn-oxide and Mn-ferrite having superior homogencity in composition and particle size distribution by co-roasting process. Binary component metal (Fe, Mn) chloride solutions were produced by dissolving mill scale and ferro-mangancse alloy in hydrochloric acid. These chloride solutions contained the impurities such as SiO$_{2}$, P, Al, Ca and Na, which were originated from the Fe/Mn source materials. The neutralization and polymeric coagulant method were adoped to refine the hydrochloric liquor. When pH is far below the isoelectric point (pH 2-3), the SiO$_{2}$ was the most effectively reduced element, while other impurities remained unchanged. By increasing pH above 3, most of the impurities could be reduced effectively due to the coprecipitation reaction. The polymeric coagulants such as poly vinyl alcohol, resin amine and ammonium molybdate were found to have no effect on the spray roaster designed by the authors. The produced oxide powders were confirmed to be mixtures of Fe-oxide, Mn-oxide and mn-ferrite. the powders were homogeneously mixed and the particle size increased sleeply with increasing co-roasting temperature.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.147-155
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• 2010

A prediction model of resilient modulus($E_R$) was developed for recycled crushed-rock-soil mixtures. The evaluation of $E_R$, using the "orthodox" repeated loading tri-axial test, is not feasible for such a large-size gravelly material. An alternative method was proposed hereby using the subtle different modulus called nonlinear dynamic modulus. The prediction model was developed by utilizing in-situ measured shear modulus($G_{max}$) and its reduction curves of modeled materials using the large free-free resonant column test. A pilot evaluation of the model parameters was carried out for recycled crushed-rock-soil-mixture at a highway construction site near Gimcheon, Korea. The values of the model parameters($A_E,\;n_E,\;{\varepsilon}_r\;and\;{\alpha}$) were proposed as 9618, 0.47, 0.0135, and 0.8, respectively.

• Animal Bioscience
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• v.35 no.7
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• pp.1100-1108
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• 2022

Objective: The objective of this study was to evaluate the effect of waste cooking oil (WCO) addition on ammonia (NH₃) emissions during the composting of dairy cattle manure under two aeration conditions. Methods: The composting tests were conducted using the laboratory-scale composting apparatuses (14 L of inner volume). Three composting treatments (Control, WCO1.5, and WCO3, with WCO added at 0 wt%, 1.5 wt%, and 3 wt% of manure, respectively) were performed in two composting tests: aeration rate during composting was changed from 0.55 to 0.45 L/min in Test 1, and fixed at 0.3 L/min in Test 2, respectively. The NH₃ emitted and nitrogen losses during the composting were analyzed, and the effect of the addition of WCO on NH₃ emissions were evaluated. Results: Both tests indicated that the composting mixture temperature increased while the weight and water content decreased with increasing WCO content of the composting mixtures. On the other hand, the NH₃ emissions and nitrogen loss trends observed during composting in Tests 1 and 2 were different from each other. In Test 1, NH₃ emissions and nitrogen losses during composting increased with increasing WCO contents of the composting samples. Conversely, in Test 2, they decreased as the WCO contents of the samples increased. Conclusion: The WCO addition showed different effect on NH₃ emissions during composting under two aeration conditions: the increase in WCO addition ratio increased the emissions under the higher aeration rate in Test 1, and it decreased the emissions under the lower aeration rate in Test 2. To obtain reduction of NH₃ emissions by adding WCO with the addition ratio ≤3 wt% of the manure, aeration should be considered.

• Explosives and Blasting
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• v.40 no.4
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• pp.27-34
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• 2022

The government is promoting various policies to reduce greenhouse gas emissions for carbon neutrality, one of the key tasks is to revitalize the hydrogen economy. As one of these policies the government has formulated a plan to incorporate hydrogen into existing city gas pipes, and aims to commercialize 20% hydrogen mixing by 2026. In preparation for the commercialization of city gas and hydrogen mixture, this study quantitatively predicts the scale of damage and the range of impact in the event of leakage of these two gas mixtures. The quantitative damage prediction method is to calculate the damage conversion distance through the calculation of the TNT equivalent by setting the leakage amount of the gas mixture in the event of an accident under a virtual scenario.

• Journal of the Mineralogical Society of Korea
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• v.17 no.2
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• pp.135-145
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• 2004

A zeolitic bentonite, which exhibits whitish appearance and contains considerable amounts (nearly 〉 5%) of zeolites, frequently occurs as thin beds less than 1 m in Yeongil area. The bentonites are mostly found in closely association with zeolite beds in the Nuldaeri Tuff and Coal-bearing formations of the Janggi Croup. A discordant occurrence of the bentonite against the bedding plane is also locally found. Montmorillonite, the major mineral constituent of the bentonite, is mostly associated with clinoptilolite as a zeolite. However, instead of clinoptilolite, mordenite is sometimes included in the case of more silicic bentonite, and heulandite in the less silicic one. It is characteristic that the mordenite is accompanied by lots of opal-CT in the silicic bentonite. SEM observations characteristically indicate that these authigenic phases, especially the montmorillonite and zeolite, nearly coexist as mixtures not forming a fine-scale zoning. The zeolitic bentonite seems to be formed in the comparatively silicic pore fluid at the alkaline condition accompanying pH fluctuation Compared to the zeolite-free normal bentonite, the zeolitic types exhibit somewhat higher REE abundance. These chemical characteristics, together with modes of occurrences and authigenic mineral associations, may suggest that the zeolitic bentonite is not merely diagenetic products and a possible hydrothermal alteration could not be excluded in the bentonite genesis.

• Journal of the Mineralogical Society of Korea
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• v.15 no.2
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• pp.122-131
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• 2002

Muscovite, chlorite and biotite in metapelites of the Ogcheon Hetamorphic Belt are studied using electron probe microanalysis (EPMA), backscattered electron images (BEI) of scanning electron microscopy (SEM) and lattice fringe images of transmission electron microscopy (TEM). These minerals are observed to be intergrown under a polarized light microscope and are apparently interlayered below EPMA resolution; EPMA data often indicate mixtures of phyllosilicates such as muscovite/chlorite (M/C), biotite/chlorite (B/C), muscovite/pyrophyllite/chlorite (M/P/C). biotite/pyrophyllite/chlorite (B/P/C) or biotite/muscovite/chlorite (B/M/C). BEI observations show that the three minerals (muscovite, chlorite and biotite) are mixed at various scales in a grain through the garnet zone, and the interlayering of the three minerals are observed from TEM lattice fringe images and selected area electron diffraction patterns. The result of TEM observations reveals that 7-$\AA$ layers (serpentine, precursor of chlorite) are interlayered within 10-$\AA$ layers (muscovite) at 100~200 $\AA$ scale as well as M/C in the chlorite zone. The 7-$\AA$ layers become smaller in size and less frequent in the biotite tone, and 10-$\AA$ layers are interlayered with chlorite (14 $\AA$) at an individual layer scale. The 7-$\AA$ layers are no longer observed in the garnet zone, and 10-$\AA$ layers (biotite) are interlayered with chlorite (B/C) at 50~100 $\AA$ scale. Relatively large scale (1000~2000 $\AA$) of intergrowth is also frequently observed from the garnet zone samples. However, rocks from all three metamorphic zones show interlayering of a few units of 7-, 10- and 14-$\AA$ layers with each other at TEM observations. The result of this study implies that metamorphic minerals such as muscovite, chlorite and biotite form through disequilibrum mineral reactions resulting in inhomogenious phases.

• Journal of Energy Engineering
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• v.22 no.4
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• pp.347-354
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• 2013

This study was carried out to examine different mole ratio of $H_2/CO_2$ and EBCT using the continuous system in the lab scale throughout biological methods with accumulated hydrogenotrophic methanogen that can convert $CO_2$ to $CH_4$. The experimental-based results with various gas mixtures of mole ratio of 4:1($H_2/CO_2$) and 5:1($H_2/CO_2$), $H_2$ was converted more than 99% conversion rate. In case of $CO_2$, 4:1($H_2/CO_2$) and 5:1($H_2/CO_2$) were $74.45{\pm}0.33%$, $95.8{\pm}10.7%$, respectively, in addition, the study was confirmed that the amount of $H_2$ was more needed than stoichiometric equations, where approach methods are empirical versus theoretical frameworks, for converting total $CO_2$. As such, we have noticed that $H_2$ was used for energy source of hydrogenotrophic methanogen for maintaining life. Regarding the results of the ratio of treatment by retention time, limitation of treatment capacity showed that $H_2$(99.9%) and $CO_2$(96.23%) at EBCT 3.3 hrs indicated stable conversion ratio, as well as appeared that methane production rate and $CO_2$ fixation rate were investigated $1.15{\pm}0.02m^3{\cdot}m^{-3}{\cdot}day^{-1}$ and $2.01{\pm}0.04kg{\cdot}m^{-3}{\cdot}day^{-1}$, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.4
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• pp.93-99
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• 2000

Treatment of shaving scrap, a chrome containing solid scrap generated by leather manufacturing process, has been so far depended on mainly incineration, soil landfill and ocean dumping, which give bad impact on environment and cause pollution. Shaving scrap generates from the mechanical work for controlling the final thickness of leather and its main components are collagen protein and pan of chromium compound. For the purpose of reusing this leather waste as resources, researches in connection with collagen fiber recovery, gelable protein recovery and liquid fertilizer is being speedily progressed. In the experiment, shaving scrap went through wet pulverizing treatment by physical and chemical methods. Then, making the leather sheet evenly, it is mixed with natural latex and every kind of binding materials in the container, and the mixtures were passed through experimental hydraulic press machine and applied to Fourdrinier machine respectively. Lastly, a test for fading out physical strength and properties of multiple-purpose of leather-like material was performed on a continuous leather sheet prepared by the experiment. In result, the physical strength and properties of leather-like material showed noticeable differences according to mixing ratio of binding materials, beating methods and the Ends of binding materials selected, and generally tear strength was the weakest property among others. Also, by the pilot scale experiment in sequence, it was possible to manufacture recycled goods made of soft and hard types of leather-like material with various performances.