• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.227-234
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• 2010

We investigated the effect of dry grinding of laterite on the extraction of nickel and cobalt. The major chemical compositions of the sample for this work were $SiO_2$, $Fe_2O_3$ and MgO. The sample contained 0.81% Ni and 0.02% Co. The major minerals of the sample were lizardite and quartz with minor amounts of forsterite and enstatite. The mean particle size, specific surface area and density of the ground sample decreased with increasing grinding time, while the amorphization of lizardite increased as identified by XRD analysis. The grinding enabled the extraction ratio of Ni and Co to increase by the breakdown of Mg-OH bonding in the lizardite structure. However, physical properties of quartz were not changed by grinding. The extraction ratio of Ni and Co increased with increasing grinding time. Approximately 80% of Ni and Co were extracted regardless of the kind of acid solutions when the sample was ground for 60 minutes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.107-108
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• 2006

• Journal of the Korean Wood Science and Technology
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• v.44 no.2
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• pp.166-171
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• 2016

Size reduction is one of the major pre-processing operations in using biomass as a source of energy or raw materials for forest products industry. The grinding characteristics of dried yellow poplar wood chips were investigated using laboratory knife mill with three different screen aperture diameters to provide the basic information for the optimizing of size reduction processes in biomass industry. Average specific energy consumptions were 0.157, 0.137, and 0.093 Wh/g for the screen aperture diameters of 5.0, 7.5, and 9.0 mm, respectively. According to the results of size distribution analysis of ground particles, the sizes of the most of ground particles were much smaller than the aperture diameters of the screens installed on knife mill used in this study.

• International Journal of Precision Engineering and Manufacturing
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• v.3 no.1
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• pp.76-82
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• 2002

This paper presents an experimental study of the effect of cutting tool materials on surface quality when turning hardened steels. Machining tests on a lathe are performed using polycrystalline cubic boron nitride (PCBN) and ceramic tools at various cutting conditions without coolant. From the experiments, it is observed that the radial force is the largest force component regardless the type of tool used. The specific cutting energy for the hard turning is estimated to be considerably smaller than the specific grinding energy. It is also found that cutting force and surface roughness with the PCBN tools are higher and better than those with the ceramic tools under the same cutting condition. It is due that the PCBN tools transfer the generated heat more effectively than the ceramic tools due to their higher thermal conductivity. The optimal cutting conditions for the best surface quality are selected by using an orthogonal array concept.

• Journal of Powder Materials
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• v.16 no.3
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• pp.196-202
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• 2009

A visible-light photoactive $TiO_{2-x}N_x$ photocatalyst was synthesized successfully by means of cogrinding of anatase-$TiO_2(a-TiO_2)$ in $NH_3$ ambient, followed by heat-treatment at $200^{\circ}C$ in air environment. In general, it is well known that the grinding-operation induces phase transformation of a-$TiO_2$ to rutile $TiO_2$. This study investigates the influence of the amount of $NH_3$ gas on the phase transformation rate of a-$TiO_2$ and enhancement of visible-light photocatalytic activity, and also examines the relation between the photocatalytic activity and the period of grinding time. The phase transformation rate of a-$TiO_2$ to rutile is retarded with the amount of NH3 injected. And the visible-light photocatalytic activity of samples, was more closely related to the period of grinding time than $NH_3$ amount injected, which means that the doping amount of nitrogen into $TiO_2$ more effective to mechanical energy than $NH_3$ amount injected. XRD, XPS, FT-IR, UV-vis, Specific surface area (SSA), NOx decomposition techniques are employed to verify above results more clearly.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.2
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• pp.61-69
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• 2015

A number of researches have been carried out regarding the utilization of nanocellulose(crystalline nanocellulose, microfibrillated cellulose, nanofibrillated cellulose) for the manufacture of various kinds of composites and functional products. However, only few research works on the manufacturing characteristics of nanocellulose could be found, although some companies started already the production of nanocellulose in commercial scale. However, the most important thing in commercializing of production and utilization of nanocellulose is to develop the economical and efficient process. Thus, this study was carried out in order to investigate the effects of refining, alkaline pre-treatment and grinder clearance on the characteristics of microfibrillated cellulose and energy consumption. There was no significant differences in crystalline index with the degree of microfibrillation. The initial fibrillation could be improved by refining pre-treatment, but its effect was not observed anymore since the fibrillation was done up to certain level by grinding. Refining pre-treatment did not improved the energy efficiency. Alkaline pre-treatment can be helpful because the swelling of pulp fiber will facilitate fibrillation. It was found that the decrease in grinder clearance was helpful to improve the energy efficiency.

• Journal of the Mineralogical Society of Korea
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• v.31 no.1
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• pp.47-55
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• 2018

Talc, hydrous magnesium phyllosilicate, is one of the most popular industrial minerals due to their chemical stability and adsorptivity. While micro-sized talc has long been used as a filler and coating, nano-sized talc recently is attracting attention as additives for improving the stability of nanocomposites. In this study, we produced the nano-sized talc powder by mechanical method using high energy ball mill and investigated the changes in particle size and crystallinity with increasing milling time up to 720 minutes. X-ray diffraction results show that the peak width of talc gradually as the milling proceeded, and after 720 minutes of pulverization, the talc showed an amorphous-like X-ray diffraction pattern. Lase diffraction particle size analysis presents that particle size of talc which was ${\sim}12{\mu}m$ decreased to ${\sim}0.45{\mu}m$ as the milling progressed, but no significant reduction of particle size was observed even after grinding for 120 minutes or more. BET specific surface area, however, steadily increases up to the milling time of 720 minutes, indicating that the particle size and morphology change steadily as the milling progressed. Scanning electron microscope and transmission electron microscope images shows that layered particles of about 100 to 300 nm was aggregated as micro-sized particles after pulverization for 720 minutes. As the grinding time increases, the particle size and morphology of talc continuously change, but the nano-sized talc particles form micro sized agglomerates. These results suggest that there is a critical size along the a, b axes in which the size of plates is reduced even though the grinding proceeds, and the reduction of plate thickness along the c axis leads the increase in specific surface area with further grinding. This study could enhance the understanding of the mechanism of the formation of nano-sized talc by mechanical grinding.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.81-86
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• 2020

A ceramic vacuum chamber feedthrough ceramic insulator is made of Al2O3; the manufacturing process involves filling alumina powder into a urethane mold and pressing it with a rubber press to produce a molded body. Thereafter, manufacturing is completed through primary shape processing, sintering, and secondary shape processing in the green body, which is a pressurized molding body, This work is intended to prevent defects in the first shape processing by improving the ceramic insulator in the green body, and to improve the productivity of the ceramic insulator by determining the optimal processing conditions.

• Journal of Environmental Health Sciences
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• v.41 no.5
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• pp.327-334
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• 2015

Objectives: In order to review both the effects of sewage sludge dewaterability and deodorizing ability in the existing advanced sewage treatment process, BIO-CLOD (a solidified mixture of 10% Bacillus concentrate and inorganics) was used as an inorganic conditioner effective for deodorization treatment in addition to the removal of organic matter and nutritive salts. Methods: Sludge dewaterability was evaluated using specific resistance to filtration (SRF) experiments with six agitators and two types of commercially available BIO-CLOD; one that is made by grinding solid matter (powdered BIO-CLOD) and one that has been obtained by sieving a separation with a particle diameter of 100 mesh (100 mesh BIO-CLOD). For deodorization odor treatment experiments, 20 g of commercially available solid BIO-CLOD was submerged in four liters of sewage sludge and mixed and agitated for 45 days. Results: When BIO-CLOD was injected into sewage sludge to experimentally compare specific resistance to filtration (SRF), the optimum amount of BIO-CLOD to be injected was shown to be 2% w/v and the SRF value in this case was $1.35{\times}10^{12}m/kg$. pH changes following BIO-CLOD injection were within 6.5-7.0. By 14 days after submerging BIO-CLOD into the sewage sludge to evaluate its deodorizing ability, $H_2S$ decreased by 68% and methyl mercaptan decreased by 74%. By 45 days after the submergal, both items decreased by 100%, indicating deodorizing ability. Conclusion: To compare the levels of dewaterablity of sewage sludge at different particle sizes of inorganic conditioner, powdered BIO-CLOD, particle size 100 mesh BIO-CLOD, and bentonite were tested. It could be seen that as the powdered BIO-CLOD increased, the precipitability increased up to 62% in 30 minutes. As an inorganic conditioner, BIO-CLOD was identified as a stable sludge conditioner that does not affect pH.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2002.08a
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• pp.109-119
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• 2002

Rice production in Korea began to rise significantly after 1970. Rice is the dominant food in Korea and most of the rice production (about 95%) is consumed as cooked rice. it provides over 4,000Kj of energy per capita per day. Apparent rice availability in 2000, 93.6Kg of milled rice per person annually. The non-allergenic character of rice offers a sound basis for development of products for markets for all age groups. Whole grains are washed rice, coated rice, enriched rice in Korea. Utilization of rice as food can be categorized three categories in Korea; direct food use, processed foods, and brewing. Rice for direct consumption include regular whole grain, precooked rice, brown rice and specialty products such as aseptic cooked rice, retort cooked rice and rice burger. Rice used for processed foods includes that for cereal, soup, baby food, snack, cake, noodle, brown rice tea, and minor unclassified uses. Rice use for brewing is for the production of fermented rice wine. The use of rice for direct food is by for the greatest of the three uses. Although direct food accounts for the largest domestic consumption, a significant quantity of rice is used in processed products. The use of rice by-products as human food should not be over looked. Utilization of by products(rice germ, rice bran) requires a specialized technology. Typical type of rice is black rice. When cooked, black rice gives a black color to cooked rice. Glutinous rice performs specific functions in several commercial products such as dessert, gravis, cake and snack. Rice starch production is quite limited because of the high cost of making of starch. Rice processed products in Korea are occupied small parts of total rice production compared to Japan. Rice cake (Garadog) is the principal from of rice product consumed in Korea. Rice cake and snack is usually prepared from non-glutinous milled by washing, grinding, steaming, cooling and packaging. Rice cake will be continued to be a major rice product in Korea. Rice products represent a means to study variety differences in rice grain quality, since the processing magnifies differences not normally detected from more boiling. Recently, rice processing companies in Korea are about 400 ones which uses rice about 160,000tons. New rice processed products and modified traditional products must be developed and diversified with high quality and processing properties of rice processed products are improved.