• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.4
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• pp.329-336
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• 2000

Welding is a important technological method in mechanical engineering. $CO_2$MAG(metal active gas) welding means that metal part in double capstan drum for the inshore and costal vessels are joined by melting(with or without a filler material) or that new material is added to a metal part by melting. The thermal stresses appear due to a non-uniform temperature field, inhomogeneous material properties, external restraint and volume changes during phase transformations. In this study analysis the elasto-plastic thermal stresses distribution of welding part in double capstan drum for the inshore and costal vessels using finite element method (FBM). Therefore it calculates the numerical value that can be applied to the optimum design of welding parts and the shapes. The significant results obtained in this study are summarized as fellows. At early stage of the cooling after welding process, the abrupt thermal stresses gradient has been shown in the vicinity of welding part. In the thermal stresses analysis due to temperature gradient and heat shocking maximum stress was occurred of welding part and stresses were distributed from 54MPa~48MPa.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.151-164
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• 2011

Mineralogical and petrological characteristics were investigated on matrix of dense gray, vesiculate gray, brown and black pumice in Ulleung Island by using XRD, FT-IR, XRF, SEM and thermal analysis. According to the analysis, most of pumice matrix are amorphous and include very small amount of sanidine and anorthoclase. Since the adsorption moistures, which commonly observed as O-H peak in FT-IR spectrum, are not identified in thermal analysis, it seems reasonable to conclude that content of the adsorption moisture has very low level. Although pumice has a large specific surface area, with long time elapsed after eruption, pumice matrix shows very low degree of hydration alteration due to the low level of water content. In SEM images, most surfaces of pumice show morphological characteristics such as various shapes of vesicle with wrinkled and thin walls resulted from ductile coalescence. Dense gray pumice formed in the initial stage includes small vesicles less than $15{\mu}m$ in size with subangular to angular shapes, free of ovoid vesicle. These characteristics are interpreted to have related to the hydrous environment derived from phreato-plinian eruption. Submicron particles observed as amorphous alumina silicate assemblages in vesicle surface are considered as particles sticked to the matrix surface through rapidly cooling process during ascent of alkali phonolitic magma. It indicates that these particles coexisted partly with crystallized alkali feldspar.

• Economic and Environmental Geology
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• v.49 no.6
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• pp.459-467
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• 2016

Due to the limited areal space for installation, borehole heat exchangers (BHEs) at depths deeper than 300 m are considered for geothermal heating and cooling in the urban area. The deep vertical closed-loop BHEs are unconventional due to the depth and the range of the typical installation depth is between 100 and 200 m in Korea. The BHE in the study consists of 50A (outer diameter 50 mm, SDR 11) PE U-tube pipe in a 150 mm diameter borehole with the depth of 300 m. In order to compensate the buoyancy caused by the low density of PE pipe ($0.94{\sim}0.96g/cm^3$) in the borehole filled with ground water, 10 weight band sets (4.6 kg/set) were attached to the bottom of U-tube. A thermal response test (TRT) and fundamental basic surveys on the thermophysical characteristics of the ground were conducted. Ground temperature measures around $15^{\circ}C$ from the surface to 100 m, and the geothermal gradient represents $1.9^{\circ}C/100m$ below 100 m. The TRT was conducted for 48 hours with 17.5 kW heat injection, 28.65 l/min at a circulation fluid flow rate indicates an average temperature difference $8.9^{\circ}C$ between inlet and outlet circulation fluid. The estimated thermophysical parameters are 3.0 W/mk of ground thermal conductivity and 0.104 mk/W of borehole thermal resistance. In the stepwise evaluation of TRT, the ground thermal conductivity was calculated at the standard deviation of 0.16 after the initial 13 hours. The sensitivity analysis on the borehole thermal resistance was also conducted with respect to the PE pipe diameter and the thermal conductivity of backfill material. The borehole thermal resistivity slightly decreased with the increase of the two parameters.

• Resources Recycling
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• v.18 no.4
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• pp.62-69
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• 2009

We researched separation of mixed waste acids with HF, $CH_3COOH$, $HNO_3$ that were produced during a semiconductor wafer process to recycle these acids. At first, we manufactured the fluoride compound in form of $Na_2SiF_6$ by precipitating HF using $NaNO_3$ and Si powder. The concentration of HF was reduced from the initial concentration of 127 g/L to 0.5 g/L with an HF recovery ratio of 99.5%. After the manufacture of $Na_2SiF_6$, the concentration of $HNO_3$ and $CH_3COOH$ demonstrated 502 g/L and 117 g/L respectively. Following these findings we added NaOH in this $CH_3COOH/HNO_3$ mixed acid in order to obtain pH=4. Next we separated the $CH_3COOH$ and recoverd it through the use of vaccum evaporation at -440 mmHg, $95^{\circ}C$. The concentration of the recovered $CH_3COOH$ was approximately 15% and the recovery ratio of $CH_3COOH$ was over 85%. We precipitated the $NaNO_3$ by cooling the concentrated solution to $20^{\circ}C$ with a $HNO_3$ recovery ratio of over 93%. We confirmed that only $Na_2SiF_6$ and $NaNO_3$ were manufactured by XRD analysis after drying these precipitants at $90^{\circ}C$. The precipitants demonstrated a purity of approximately 97% and 98% respectively. Therefore, the purity of the precipitants proved to be similar to that of commercial products.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.67-72
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• 2010

In this study, the impact on the circulating water system has been analyzed due to an installation of helical turbine to develop hydro-kinetic energy at the discharge channel of the power plant. Numerical simulations of velocity and pressure variations have been performed when one set of $3.6\;m\;{\times}\;1.5\;m$ sized helical turbine is installed at the outlet of discharge culvert. In case of mean sea level, change of downstream water surface elevation does not affect upstream elevation of the weir because its propagation is blocked by the seal well weir. However in case of highest high water level, change of downstream elevation affects upstream elevation because flow pattern in discharge culvert becomes the full pipe flow with submerged weir. Although an unstable pressure change occurs in upstream of the weir during the intial 10 minutes after beginning of the discharge, it becomes stable after that time. In addition, a rise of water surface elevation by 0.2 m is observed but it is concluded that it hardly affects the safety of circulating water pump (CWP) although its required power is increased more or less. Therefore, the increase of required power of CWP needs to be considered for evaluation of the helical turbine applicability.

• Journal of the Korean Society of Food Culture
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• v.22 no.5
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• pp.603-608
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• 2007

Optimal winterizing condition of com oil was cooling temperature of bleached oil from $105^{\circ}C$ to $40^{\circ}C$. Then, filtering it after keeping $1{\sim}2^{\circ}C$ by lowering the temperature gradually with treating perlite of 0.3%(w/w) amount about bleached oil and stirring. We could measure that triglyceride(TG) that extracted from lipid components from spent perlite(SP) obtained through filtration after winterizing by SACC method is major causing materials of clouding in com oil. The result of separating TG fraction by agentation TLC was that it classified into 4 kinds -U3, SU2, S2U, S3 type and the most were U3 type. From this, it's easy to identify cause of clouding in com oil is TG fraction and most of them form wax materials that can observed. The results were they kept clear appearance at $0^{\circ}C$ generally during 39.6 to 96.5 hours, especially the result of A sample that had the lowest temperature condition while they have some difference by condition of treating temperature.

• Clean Technology
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• v.30 no.2
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• pp.113-122
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• 2024

In order to better understand carbon dioxide recycling, the carbon dioxide capture characteristics of six different alkaline industrial by-products, including incineration ash, desulfurized gypsum, low-grade quicklime, and steelmaking slag were investigated using a laboratory-scale direct aqueous carbonation reactor. In addition to the dissolution characteristics of each sample, the main reaction structure was confirmed through thermogravimetric analysis before and after the reaction, and the reactive CaO content was also defined through thermogravimetric analysis. The carbon dioxide capture capacity and efficiency of quicklime were determined to be 473 g/kg and 86.9%, respectively, and desulfurized gypsum and incineration ash were also evaluated to be relatively high at 51.1 to 131.7 g/kg and 51.2 to 87.7%, respectively. On the other hand, the capture efficiency of steelmaking slag was found to be less than 10% due to the influence of the production and post-cooling conditions. Therefore, in order to apply the carbonation process to steelmaking slag, it is necessary to optimize the slag production conditions. Through this study, it was confirmed that the carbon dioxide capture characteristics of incineration ash, quicklime, and desulfurized gypsum are at levels suitable for carbonation processes. Furthermore, this study was able to secure basic data for resource development technology that utilize carbon dioxide conversion to produce calcium carbonate for construction materials.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.14-14
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• 2011

W (tungsten)-alloys will be the most promising plasma facing armor materials in highly loaded plasma interactive components of the next step fusion reactors due to its high melting point, high sputtering resistance and low deuterium/tritium retention. The bonding technology of tungsten to Cu alloy was one of the key issues. In this paper, W/CuCrZr diffusion bonding has been performed successfully by inserting pure metal interlay. The joint microstructure, interfacial elements migration and phase composition were analyzed by SEM, EDS, XRD, and the joint shear strength and micro-hardness were investigated. The mock-ups were fabricated successfully with diffusion bonding and the cladding technology respectively, and the high heat flux test and thermal fatigue test were carried out under actively cooling condition. When Ni foil was used for the bonding of tungsten to CuCrZr, two reaction layers, Ni4W and Ni(W) layer, appeared between the tungsten and Ni interlayer with the optimized condition. Even though Ni4W is hard and brittle, and the strength of the joint was oppositely increased (217 MPa) due primarily to extremely small thicknesses (2~3 ${\mu}m$). When Ti foil was selected as the interlayer, the Ti foil diffused quickly with Cu and was transformed into liquid phase at $1,000^{\circ}C$. Almost all of the liquid was extruded out of the interface zone under bonding pressure, and an extremely thin residual layer (1~2 ${\mu}m$) of the liquid phase was retained between the tungsten and CuCrZr, which shear strength exceeded 160 MPa. When Ni/Ti/Ni multiple interlayers were used for bonding of tungsten to CuCrZr, a large number of intermetallic compound ($Ni_4W/NiTi_2/NiTi/Ni_3T$) were formed for the interdiffusion among W, Ni and Ti. Therefore, the shear strength of the joint was low and just about 85 MPa. The residual stresses in the clad samples with flat, arc, rectangle and trapezoid interface were estimated by Finite Element Analysis. The simulation results show that the flat clad sample was subjected maximum residual stress at the edge of the interface, which could be cracked at the edge and propagated along the interface. As for the rectangle and trapezoid interface, the residual stresses of the interface were lower than that of the flat interface, and the interface of the arc clad sample have lowest residual stress and all of the residual stress with arc interface were divided into different grooved zones, so the probabilities of cracking and propagation were lower than other interfaces. The residual stresses of the mock-ups under high heat flux of 10 $MW/m^2$ were estimated by Finite Element Analysis. The tungsten of the flat interfaces was subjected to tensile stresses (positive $S_x$), and the CuCrZr was subjected to compressive stresses (negative $S_x$). If the interface have a little microcrack, the tungsten of joint was more liable to propagate than the CuCrZr due to the brittle of the tungsten. However, when the flat interface was substituted by arc interfaces, the periodical residual stresses in the joining region were either released or formed a stress field prohibiting the growth or nucleation of the interfacial cracks. Thermal fatigue tests were performed on the mock-ups of flat and arc interface under the heat flux of 10 $MW/m^2$ with the cooling water velocity of 10 m/s. After thermal cycle experiments, a large number of microcracks appeared at the tungsten substrate due to large radial tensile stress on the flat mock-up. The defects would largely affect the heat transfer capability and the structure reliability of the mock-up. As for the arc mock-up, even though some microcracks were found at the interface of the regions, all microcracks with arc interface were divided into different arc-grooved zones, so the propagation of microcracks is difficult.

• Journal of Food Hygiene and Safety
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• v.29 no.2
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• pp.79-84
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• 2014

This study has been performed for about 270 days at analyzing biologically hazardous factors in order to develop HACCP system for the non heat-frozen carrot juice. A process chart was prepared by manufacturing process of raw agricultural products of non heat-frozen carrot juice, which was contained water and packing material, storage, washing, cutting, extraction of the juice, internal packing, metal detection, external packing, storage and consignment (delivery). As a result of measuring Coliform group, Staphylococcus aureus, Salmonella spp., Bacillus cereus, Listeria Monocytogenes, Enterohemorrhagic E. coli before and after washing raw carrot, Standard plate count was $4.7{\times}10^4CFU/g$ before washing but it was $1.2{\times}10^2CFU/g$ detected after washing. As a result of testing airborne bacteria (Standard plate count, Coliform group, Yeast and Fungal) depending on each workplace, number of microorganism of in packaging room, shower room and juice extraction room was detected to be 10 CFU/Plate, 60 CFU/Plate, 20 CFU/Plate, respectively. As a result of testing palm condition of workers, as number of Standard plate count, Coliform group and Staphylococcus aureus was represented to be high as $6{\times}10^4CFU/cm^2$, $0CFU/cm^2$ and $0CFU/cm^2$, respectively, an education and training for individual sanitation control was considered to be required. As a result of inspecting surface pollution level of manufacturing facility and devices, Coliform group was not detected in all the specimen but Standard plate count was most dominantly detected in scouring kier, scouring kier tray, cooling tank, grinding extractor, storage tank and packaging machine-nozzle as $8.00{\times}10CFU/cm^2$, $3.0{\times}10CFU/cm^2$, $4.3{\times}10^2CFU/cm^2$, $7.5{\times}10^2CFU/cm^2$, $6.0{\times}10CFU/cm^2$, $8.5{\times}10^2CFU/cm^2$ respectively. As a result of analyzing above hazardous factors, processing process of ultraviolet ray sterilizing where pathogenic bacteria may be prevented, reduced or removed is required to be controlled by CCP-B (Biological) and critical level (critical control point) was set at flow speed is 4L/min. Therefore, it is considered that thorough HACCP control plan including control criteria (point) of seasoning fluid processing process, countermeasures in case of its deviation, its verification method, education/training and record control would be required.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.241-247
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• 2001

Boundary line method was adopted to analyze the relationships between rice yield and meteorological conditions during rice growing period. Boundary lines of yield responses to mean temperature($T_a$) and sunshine hour( $S_{h}$) and diurnal temperature range($T_r$) were well-fitted to hyperbolic functions of f($T_a$) =$$\beta$_{0t}$(1-EXP(-$$\beta$_{1t}$ $\times$ ($T_a$) ) and f( $S_{h}$)=$$\beta$_{0t}$((1-EXP($$\beta$_{1t}$$\times$ $S_{h}$)), to quadratic function of f($T_r$) =$\beta$$_{0r}$(1-($T_r$ 1r)$^2$), respectively. to take into account to, the sterility caused by low temperature during reproductive stage, cooling degree days [$T_c$ =$\Sigma$(20-$T_a$] for 30 days before heading were calculated. Boundary lines of yield responses to $T_c$ were fitted well to exponential function of f($T_c$) )=$\beta$$_{0c}$exp(-$$\beta$_{1c}$$\times$$T_c$ ). Excluding the constants of $\beta$$_{0s}$ from the boundary line functions, formed are the relative function values in the range of 0 to 1. And these were used as yield indices of the meteorological elements which indicate the degree of influence on rice yield. Assuming that the meteorological elements act multiplicatively and independently from each other, meteorological yield index (MIY) was calculated by the geometric mean of indices for each meteorological elements. MIY in each growth period showed good linear relationship with rice yield. The MIY's during 31 to 45 days after transplanting(DAT) in vegetative stage, during 30 to 16 days before heading (DBH) in reproductive stage and during 20 days after heading (DAH) in ripening stage showed greater explainablity for yield variation in each growth stage. MIY for the whole growth period was calculated by the following three methods of geometric mean of the indices for vegetative stage (MIVG), reproductive stage (HIRG) and ripening stage (HIRS). MI $Y_{I}$ was calculated by the geometric mean of meteorological indices showing the highest determination coefficient n each growth stage of rice. That is, (equation omitted) was calculated by the geometric mean of all the MIY's for all the growth periods devided into 15 to 20 days intervals from transplanting to 40 DAH. MI $Y_{III}$ was calculated by the geometric mean of MIY's for 45 days of vegetative stage (MIV $G_{0-45}$ ), 30 days of reproductive stage (MIR $G_{30-0}$) and 40 days of ripening stage (MIR $S_{0-40}$). MI $Y_{I}$, MI $Y_{II}$ and MI $Y_{III}$ showed good linear relationships with grain yield, the coefficients of determination being 0.651, 0.670 and 0.613, respectively.and 0.613, respectively.