• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.8-13
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• 2018

Nitrogen oxides (NOx) have recently been very influential in the generation of ultrafine dust, which is of great social interest in terms of improving the atmospheric environment. Nitrogen oxides are generated mainly by the reaction of nitrogen and oxygen in air in a combustion gas atmosphere of high temperature in a combustion apparatus such as thermal power generation. Recently, research has been conducted on the combustion that recirculates the exhaust gas to the cylindrical burner by using a piping using a Coanda nozzle. In this study, three types of burners were carried out through computational fluid analysis. Case 1 burner with the outlet of the combustion gas to the right, Case 2 burner with both sides as gas exit, Case 3 burner with left side gas exit. The pressure, flow, temperature, combustion reaction rate and distribution characteristics of nitrogen oxides were compared and analyzed. The combustion reaction occurred in Case 1 and Case 2 burner in the right direction with combustion gas recirculation inlet and Case 3 burner in the vicinity of mixed gas inlet. The temperature at the outlet was about $100^{\circ}C$ lower than that of the other burners as the Case 2 burner was exhausted to both sides. The NOx concentration of Case 1 burner at the exit was about 20 times larger than that of the other burners. From the present study, it could be seen that it is effective for the NOx reduction to exhaust the exhaust gas to both side gas exits or to exhaust the exhaust gas to the opposite direction of inlet of recirculation gas.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.81-87
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• 1997

Chonnam and Kyongsang clay alteration areas are distributed in volcanic fields of the Yuchon Group in late Cretaceous period. The host rock of the Chonnam alteration area is generally acidic and that of the Kyongsang alteration area is acidic to dominantly intermediate volcanics. The important difference of two alteration areas is source of fluid; the Chonnam alteration area is characterized by dominantly meteoric water and the Kyongsang alteration area is characterized by dominantly magmatic water. Accordingly, the high temperature minerals such as pyrophyllite and andalusite, and boron bearing minerals such as dumortierite and tourmaline are common in the Kyongsang alteration area. In contrast to this, the lower temperature minerals such as kaolin and alunite are common in the Chonnam alteration area. The mineralogical difference of two alteration areas were depended on the difference of the formation temperature of clay deposits. The other important geochemical difference is the chemistry of hydrothermal solution such as pH. The alteration of "acid-sulfate type" with alteration mineral assemblage of alunite-kaolin-quartz is dominant in the Chonnam alteration area, which was caused by the attack of strong acid and acid solution. In contrast to this, the that of "quartz-sericite type" with the mineral assemblage of sericite-quartz is dominant in the Kyongsang alteration area, which was caused by the attack of neutral or weak acid solution. Also, the Kyongsang and Chonnam alteration areas show the difference in structural setting; the Chonnam alteration area is commonly associated with silicic domes and the Kyongsang alteration area is commonly associated with calderas.

• Animal Bioscience
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• v.34 no.11
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• pp.1784-1793
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• 2021

Objective: An experiment was conducted to evaluate the effects of bamboo leaf extract (BLE) on the production performance, rumen fermentation parameters, and rumen bacterial communities of heat-stressed dairy cows. Methods: The experiment comprised a 14-day adaptation period and a 21-day experimental period and was conducted in a high-temperature and humidity environment (daily mean ambient temperature = 33.5℃±1.3℃; daily mean relative humidity = 64.9%±0.8%, daily mean temperature-humidity index = 86.2±0.4). Twelve Holstein dairy cows were randomly allocated into two groups. A total mixed ration supplemented with BLE at 0 (CON) and 1.3 g/kg dry matter (DM) were fed, respectively. Feed intake and milk yield were recorded daily. Milk samples were collected on 1, 11, and 21 d of the experimental period to analyze milk performance. Rumen fluid samples were collected on 21 d of the experimental period to analyze rumen fermentation parameters and rumen bacterial communities. Results: Compared with the control group, supplementation of BLE increased milk yield (p<0.01), milk fat yield (p = 0.04), 4% fat-corrected milk (p<0.01) and milk fat content (p<0.01); reduced somatic cell count (p<0.01). No differences in DM intake and milk protein or lactose content were observed between two groups. Supplementation of BLE also increased the rumen total volatile fatty acid (p<0.01), acetate (p<0.01), butyrate (p<0.01), and valerate (p = 0.05) concentrations. However, no significant effects were observed on rumen pH, ammonia nitrogen, propionate, acetate/propionate ratio, isobutyrate, or isovalerate. Furthermore, BLE increased the rumen bacterial abundance and the diversity of the rumen bacterial community. The BLE reduced the Firmicutes/Bacteroidetes abundance ratio and increased the abundances of Butyrivibrio_2 (p<0.01) and Ruminococcus_2 (p<0.01). Conclusion: The BLE supplementation at 1.3 g/kg DM could improve production performance and rumen fermentation in dairy cows during heat stress.

• Korean Journal of Mineralogy and Petrology
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• v.36 no.3
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• pp.199-212
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• 2023

Diffusion is a powerful tool to understand geological processes recorded in terrestrial rocks as well as extraterrestrial materials. Since the diffusive exchange of elements or isotopes may have occurred differently in the solar nebula (high temperature and rapid cooling) and on the parent bodies (fluid-assisted thermal metamorphism at relatively low temperature), it is particularly important to model elemental or isotopic diffusion profiles within the mineral grains to better understand the evolution of the early solar system. A numerical model with the finite difference method for the fast grain boundary diffusion was established for the exchange of elements or isotopes between constituent minerals in a closed system. The fast grain boundary diffusion numerical model was applied to 1) ²⁶Mg variation in plagioclase of an amoeboid olivine aggregate (AOA) from a CH chondrite and 2) Fe-Mg interdiffusion between chondrules, AOA, and matrix minerals in a CO chondrite. Equilibrium isotopic fractionation and equilibrium partitioning were also included in the numerical model, based on the assumption that equilibrium can be reached at the interfaces of mineral crystals. The numerical model showed that diffusion profiles observed in chondrite samples likely resulted from the diffusive exchange of elements or isotopes between the constituent minerals. This study also showed that the closure temperature is determined not only by the mineral with the slowest diffusivity in the system, but also strongly depends on the constituent mineral abundances.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.109-121
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• 1995

The hydrothermal vein type deposits which comprise the Kasihan, Jompong and Gempol mineralized areas are primarily copper and zinc deposits, but they are also associated with lead and/or gold mineralization. The deposits occur within the Tertiary sedimentary and volcanic rocks in the Southern Mountain zone of the eastern Java island, Indonesia. Mineralization can be separated into two or three distinct stages (pre-and/or post- ore mineralization stages and main ore mineralization stage) which took place mainly along pre-existing fault breccia zones. The main phase of mineralization (the main ore stage) can be usually classified into three substages (early, middle and late) according to ore mineral assemblages, paragenesis, textures and their chemical compositions. Ore mineralogy and paragenesis of the three areas in the district are different from each other. Pyrite, pyrrhotite (/arsenopyrite), iron-rich (up to 20.5 mole % FeS) sphalerite and (Cu-)Pb-Bi sulfosalts are characteristic of the deposits in the Kasihan (/Jompong) area. On the other hand, pyrite + hematite + magnetite + iron-poor (2.7 to 3.6 mole % FeS) sphalerite assemblage is restricted to the Gempol area. Fluid inclusion data suggest that fluids of the main ore stage evolved from initial high temperatures (near $350^{\circ}C$) to later lower temperatures (near $200^{\circ}C$) with salinities ranging from 0.8 to 10.1 equiv. wt. percent NaCl. Each area represents a separate hydrothermal system: the mineralization at Kasihan and Jompong were largely due to early fluid boiling coupled with later cooling and dilution, whereas the mineralization at Gempol was mainly resulted from cooling and dilution by an influx of cooler meteoric waters. Fluid inclusion evidence of boiling indicates that pressures of ${\geq}95$ to 255 bars (${\geq}95$ bars for the Gempol area: $\approx$ 120 to 170 bars for the Jompong area: $\approx$ 140 to 255 bars for the Kasihan area) during portions of main ore stage mineralization. Equilibrium thermodynamic interpretation indicates that the evolution trends of the temperature versus fS2 variation of ore stage fluids in the Pacitan district follow two fashions: ore fluids at Kasihan and Jompong changed from the pyrite-pyrrhotite sulfidation stage towards pyritehematite- magnetite state, whereas those at Gempol evolved nearly along pyrite-hematite-magnetite reaction curve with decreasing temperature. The sulfur isotope compositions of sulfide minerals are consistent with an igneous source of sulfur with a ${\delta}^{34}S_{{\Sigma}s}$ value of about 3.3 per mil. The oxygen and hydrogen isotopic compositions of the fluids in each area indicate a progressive shift from the dominance of highly exchanged meteoric water at early hydrothermal systems towards an un- or less-exchanged meteoric water at later hydrothermal systems.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.169-178
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• 1998

The crystal phases precipitated in various compositions glass of CaO-$SiO_2-P_2O_5$ system, were identified by XRD. E composition (CaO 49.4, $SiO_2\;36.8,\;P_2O_5$ 8.8 wt%) glass in which both apatite(($Ca_{10}(PO_4)_6O$ and $\beta$-wollastonite($CaSiO_3$) crystals would precipitate by heating, was selected as an experimental composition to prepare the glass ceramics with high bending strength and good bioactivity to the living bone. Glass powders of E composition were unidirectionally crystallized at $1050^{\circ}$C in the temperature-gadient furnace and the resultant glass ceramics were characterized. Bending strength of the glass ceramics was also measured. To investigate the bond forming ability between the glass ceramics and living bone tissue, soaking test of glass ceramics in simulated body fluid was carried out. Densed glass ceramics composed of apatite and $\beta$-wollastonite crystal were prepared by unidirectional crystallization under the optimum conditions. (2 0 2) plane of $\beta$-wollastonite crystals tended to grow perpendicularly to the crystallization direction. Average bending strength of this glass ceramics was 186.9 MPa, higher than that of the glass ceramics prepared by isothermal (not directional) crystallization In soaking test, a thin layer of apatite crystallite was formed on surface of the glass ceramics in 3 days. Apatite crystals formed on the glass ceramics could be act a role to make the chemical bond between the glass ceramics and living bone tissue.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1027-1033
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• 2010

A two-phase (gas-liquid) flow is a common phenomenon in fluidic systems, e.g., fluidic systems in the electro-magnetic or nuclear power generation industry and in the steel industry. The measurement of a two-phase flow is important for guaranteeing the safety of the system and for achieving the desired performance. The measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient, is very important. The time resolution achieved by employing the impedance method that can be used to calculate the void fraction from the impedance of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the void fraction without distortion of flow in real time by placing electrodes on the walls of the tubes. Coney analytically studied a ring-type impedance meter, which can be employed in a circular tube. The aim of this study is to experimentally verify the robustness of a three-ring impedance meter to variations in the electric conductivity of the fluid; this robustness was suggested by Coney but was not experimentally verified.

• The Journal of Engineering Geology
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• v.8 no.2
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• pp.175-188
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• 1998

This paper describes the internal structures and K-Ar ages of fault gouges collected from the Dongnae fault zone. This fault zone is internally zoned and occurs in the multiple fault cores. A fault core consists of thin gouge and narrow cataclastic zones that are bounded by a much thicker damage zone. Intensity of deformation and alteration increases from damage zone through cataclastic zone to gouge zone. It is thought that cataclasis of brittle deformation was the dominant strain-accomodation mechanism in the early stage of deformation to form the gouge zone and that crushed materials in the regions of maximum localization of fault slip subsequently moved by cataclastic flow. Deformation mechanism drastically changed from brittle processes to fluid-assisted flow along the gouge zone as the high porosity and permeability of pulverzied materials during faulting facilitated the influx of the hydrothermal fluids. Subsequently, the fluids reacted with gouge materials to form clay minerals. Fracturing and alteration could have repeatedly taken place in the gouge zone by elevated fluid pressures generated from the reduction of pore volume due to the formation of clay minerals and precipitation of other materials. XRD analysis revealed that the most common clay minerals of the gouge zones are illite and smectite with minor zeolite and kaolinite. Most of illites are composed of 1Md polytype, indicating the products of hydrothermal alteration. The major activities of the Dongnae fault can be divided into two periods based upon K-Ar age data of the fault gouges : 51.4∼57.5Ma and 40.3∼43.6Ma. Judging from the enviromental condition of clay mineral formation, it is inferred that the hydrothermal alteration of older period occured at higher temperature than that of younger period.

• Journal of the Korea Organic Resources Recycling Association
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• v.14 no.3
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• pp.85-90
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• 2006

The purpose of this research is to design an imitation boiler similar to the waste heat boiler installed on a plasma melting furnace in order to acquire a capability of a thermal design as to the circulation of heat and the discharge of noxious gas inside a boiler and to improve the efficiency of a waste heat boiler using the CFD (Computation Fluid Dynamics) program. The position of corrosion and the generation of a clinker inside a boiler due to temperature changes, combustion gas flows, and corrosive gases inside a boiler are examined to design the structure of an efficient boiler and recycle energy. As a result of this research, the boiler installed on a plasma melting furnace met the conditions of design by cooling the combustion gases discharged after the second combustion from an exhaust port, originally at 1,200 degrees Celsius, down to around 450 degrees Celsius. On the other hand, the circulation of corrosive gases (SOx and HCL) may lead to the generation of corrosion or a clinker in the upper and lower parts of an exhaust port more easily than any other parts of a boiler. Accordingly, the corrosion on the inside and outside walls of a boiler may result in a shortened lifespan of a boiler and an inability to recycle waste heat in an efficient manner. A prevention against corrosion at high and low temperatures needs to be considered in detail.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.49-55
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• 2018

Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.