• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.95-98
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• 1998

Fly ash is glassy dust collected from coal fired power plant. Recently, much research for fly ash conducted in Korea and fly ash is a valuable material especially when it used in high strength, high flowable, high durability concrete. But it varies with coal source, coal grinding and boiler conditions. Therefore, it is important that quality control of fly ash itself to get high quality concrete. In this study, over 20 samples of Poryong and Samchonpo fly ashs are tested and analyzed. The physical, chemical properties of fly ash and their relationships are investigated and it can be applied to quality control of concrete.

• Korean Journal of Agricultural Science
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• v.10 no.2
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• pp.334-344
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• 1983

This study was conducted to investigate the variables affecting the performance of hammer mills by the theoretical and dimensional analysis, and evaluate the power requirements of hammer mills for farm use in Korea. From the theoretical analysis, 16 variables affecting the performance of hammer mills were defined. In order to develop the mathematical relationships among the variables, the dimensional analysis was made for power requirements and $12{\pi}$ parameters were obtained. For the evaluation of the power requirements of hammer mills, approximate rates of grinding for 1HP, 3HP, 5HP, 6HP, 8HP, and 10HP were analyzed. Then, the fineness of grinding recommendation and average feeding rate of grain for livestock which is native cattle, dairy cattle, beef cattle, swine, broilers, and layers, were estimated. Finally number of livestock feeding shelled corn and barley were estimated from the above for one hour's hammer mill operation having the various power requirements. From this study it is known that 5HP is considered as an enough power for feed grinding of any kinds of livestock of Korean farm, as far as the grinding capacity is concerned.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.139-145
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• 1996

The machining accuracy and performance is largely influenced by the static, dynamic and thermal characteristics of spindle systems in machine tools, because the spindle system is a intermedium for cutting force from tool and machine powef from motor. Large cutting force and power are transmitted by bearing with a point or line contact. So, the spindle system is the static and dynamic weakest point in machine structure. For improvement of static stiffness of spindle system can be changed design parameters, such as diameter of spindle, stiffness of bearing and bearing span. But for dynamic stiffness, the change of the design parameters are not useful. In this paper, the combined bearing arrangement is suggested for high damping spindle system. The combined bearing arrangement is composed of tandem double back to back arrangement type ball bearins and a high damping hydrostatic bearing. The variation of static deflection and amplitude in first natural frequency is evaluated with the location of hydrostatic bearing between front and rear ball bearing. The optimized location of hydrostatic bearing for high static and dynamic stiffness is determined rapidly and exactly using the mode shape and transfer function of spindle. The calculation of damping effect on vibration by unbalance of grinding wheel and pulley in optimized spindle system is carried out to verify the validity of the combined bearing arrangement. Finally, the simulation of grinding process show that the surface roughness of workpiece with high damping spindle system is 60% better than with ball bearing spindle system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.87-92
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• 2018

As gas turbines for power generation become increasingly more important for high capacity and high efficiency, the technological development and investment of companies are increasing globally. Gas turbine manufacturing technology is only owned by a few companies such as GE, Siemens, and MHI, and our country currently depends on imports of processing technology and component parts. The core part of the gas turbine is curvic coupling tooth processing technology that improves turbine efficiency by smoothly transmitting power to the turbine rotor. Curvic coupling tooth machining and evaluation research is restricted overseas, and it is not underway in Korea. Therefore, in this study, roughing and finishing process technology for curvic coupling tooth machining is developed and a quantitative evaluation method is proposed. For the development of machining technology, the analysis of critical parameters was performed through C & E analysis. In the roughing process, the conditions considering the minimum machining time and tool load ratio were determined. Finishing process conditions were determined based on the contact ratio between the tooth surfaces. The image-processing method is presented for evaluation of the contact ratio and a verification test was performed.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.8
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• pp.1076-1083
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• 2009

The physicochemical properties of rice flour produced by 3 different grinding methods using various steeping times (3, 6, 9, and 12 hrs) were investigated. Roller mill gave coarse rice flour; the pin mill, intermediate flour; and mixed when both (roller & pin mills) were used. With the increase of steeping times, the rice flours became finer and the contents of crude protein, crude fat and crude ash decreased. Damaged starch was noticeably high in rice flour by roller & pin mills compared to those by roller or pin mills alone. Amylose contents, solubility and swelling power increased as the steeping times increased. Water binding capacity was the highest in roller & pin mills, followed by pin mill. In scanning electron microscope (SEM), pin mill showed distribution of separated fine particles of rice flours. The physicochemical properties of rice flours showed many differences by steeping times of rice and grinding methods. With sufficient steeping times, the rice flours obtained from pin mill were relatively fine having less damaged starch.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.57-59
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• 2018

This paper presents a novel reference variable speed control scheme of a BLDC motor for the high-speed blender machine according to the current limit. Because of a pulsating load variation of a high-speed blender machine, the actual speed is pulsated by the current limit in the high-speed region. The proposed control scheme uses a variable reference speed to reduce the speed variation from the current limit in the constant power region. The pulsated load is occurred at the material crushing, then the pulsated load is reduced after grinding. The reference speed is smoothly reduced at the pulsated load variation, then the enough torque can make a constant speed during crushing. When the pulsating load is reduced, the reference speed is automatically increased to the original speed value. The proposed control scheme is verified by experimental result by practical blender machine.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.543-547
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• 2011

Primary water stress corrosion cracking has occurred in dissimilar weld areas in nuclear power plants. Residual stress is a driving force in the crack. Residual stress may be generated by weld or surface machining. Residual stress due to surface machining depends on the machining method, e.g., milling, grinding, or EDM. The stress is usually distributed on or near the surface of the material. We present the measured residual stress for machining on SA 508 and austenitic stainless steels such as TP304 and F316. The residual stress can be tensile or compressive depending on the machining method. The depth and the magnitude of the residual stress depend on the material and the machining method.

• Korean journal of food and cookery science
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• v.26 no.6
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• pp.727-736
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• 2010

The purpose of this research was to compare the physicochemical compositions and morphological properties of five varieties of rice flours (RR, RGD, RSGD, RWDG, RWGD). RR was raw milled rice without washing, RGD was raw rice flour without soaking, RSGD was raw milled rice flour with 0 hr of soaking, RWDG was raw rice flour with 8 hr of soaking and grinding after drying, and RWGD was raw rice flour with 8hr of soaking and drying after grinding. The protein and lipid contents of wet milling rice flour (RSGD, RWDG, RWGD) were significantly lower than those of dry milling rice flour (RR, RGD). L and a values were significantly increased in wet milling rice flour, and b value was significantly increased in dry milling rice flour. Scanning electron microscopy (SEM) showed that RWDG and RWGD were distributed as separated fine particles in rice flours. The WBC of RWDG and RWGD were higher than those of other rice flours. Solubility was significantly increased according to the temperature, and swelling power of RWDG was higher than that of other rice flours at 50 and $60^{\circ}C$. Using RVA, the initial pasting temperature and setback of RWDG were lower and the peak viscosities of RSGD and RWDG were higher than those of other rice flours. Using a mixograph, peak times were not significantly different among the groups, wheras peak heights were significantly decreased in RSGD, RWDG, and RWGD. The peak width of RWGD was lower than those of other rice flours. Based on these findings, RWDG flour was less damaged, and had a lower setback and pasting temperature, which makes it an appropriate rice flour for commercial mass production.

• Korean Journal of Food Science and Technology
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• v.35 no.3
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• pp.393-398
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• 2003

Effects of convection oven dehydration conditions on the physicochemical and sensory properties of ginkgo nut powder were examined using three types of pre-treatment on ginkgo nuts: coarse grinding of ginkgo nut (GR); coarse grinding followed by 1 min blanching (GB); 3 min blanching followed by coarse grinding (BG). Pretreated ginkgo nuts were dried in convection oven at 70 and $80^{\circ}C$ to the moisture content of approximately 5%. Rehydration rate, swelling power, solubility, lightness, and greenness of GB ginkgo nut powder dried at $70^{\circ}C$ were the most similar to those of freeze dried one. GR and GB samples dried at $70^{\circ}C$ had higher sensory values of green color and ginkgo nut flavor. Ginkgo nut powder with desirable quality attributes could be produced by drying GB in convection oven at $70^{\circ}C$ for 10 hr.

• Plant Journal
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• v.18 no.3
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• pp.28-40
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• 2022

As the proportion of renewable energy generation is expected to increase, public power generation businesses need to actively consider implementing the expansion of biomass mixing, In this study, the biomass co-firing rate is being changed from 0wt.% to 5.0wt.% at 500MW coal-fired power plant, measuring the major operation characteristics of the pulverizer. First, the composition analysis and grinding characteristics of lignocelluosic biomass were examined, and the effect of volume increase on dirrerential bowl pressure difference, motor current, coal spillage, outlet temperature, and internal fire count was analyzed. As the co-firing rate increased, it was confirmed that the difference in the differential bowl pressure, motor current, and coal spillage treated increased, and the outlet temperature was minimal. The number of internal fires is difficult to find a clear correlation, but it has been confirmed that it is highly likely to occur in combination with other driving factors.