• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06a
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• pp.85-90
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• 2006

Increasing the filler content of sheet improves the optical properties and printability of paper and provides an opportunity for saving production cost through fiber replacement with relatively low-priced filler. But increasing the filler content tends to decrease the strength of paper and filler retention. It also tends to deteriorate drainage on the paper machine. To overcome these problems, preflocculation technology of fillers may be employed. Many research efforts have been made on the properties of preflocculated filler, namely prefloc, whose size and size distribution were influenced by polymer type and shear level. But there is much to be investigated about the effect of the prefloc characteristics on the physical properties of paper. To evaluate the effect cationic polymers on the size and size distribution of preflocculated GCC and their shear stability, cationic PAM and cationic starch were used. The influence of the preflocculation on filler retention and its surface distribution, and the changes of physical and optical properties of handsheets affected by the characteristics of preflocs were examined. Filler distribution on sheet surface was also analyzed by EPMA. Results showed that cationic PAM formed large preflocs at low dosage. Cationic starch was required to add 15 times as much as cationic PAM to obtain the preflocs with similar size. But preflocs formed with cationic starch was superior in shear stability to those formed with cationic PAM. Filler preflocculation technology could provide an opportunity of increasing filler content significantly without loss in tensile strength. And increased filler contents could compensate brightness loss which often accompanies filler preflocculation. When excessively large preflocs were used, however, brightness loss rather than the improvement in tensile strength was predominant. Therefore it is of great importance to produce preflocs with proper size and shear stability for maximizing the improvement of physical properties of papers.

• Tribology and Lubricants
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• v.33 no.5
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• pp.214-219
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• 2017

Abrasive fluidized bed machining (AFBM) is similar to general abrasive fluidized machining (AFM) in that it can perform polishing of the outer and inner surfaces of a 3-dimensional shape by the flow of particles. However, in the case of AFM, the shear force generated by the flow of the particles causes material removal, while in AFBM, the abrasive particles are suspended in the chamber to form a bed. AFBM can be used for deburring, polishing, edge contouring, shot peening, and cleaning of mechanical parts. Most studies on AFBM are limited to metals, and research on application of AFBM to plastic materials has not been performed yet. Therefore, in this study, we investigate the effect of rotating speed of the specimen and the air flow rate on the material removal characteristics during AFBM of polyacetal with a horizontal AFBM machine. The material removal rate (MRR) increases linearly with increase of the rotating speed of the main shaft because of the shear force between the particles of the fluidized bed and the rotation of the workpiece. The reduction in surface roughness tends to increase as the rotating speed of the main shaft increases. As the air flow rate increases, the MRR tends to decrease. At a flow rate of 70 L/min or more, the MRR remains almost constant. The reduction of the surface roughness of the specimen is found to decrease with increasing air flow rate.

• Journal of the Korean earth science society
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• v.25 no.5
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• pp.315-326
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• 2004

The aim of this study is to investigate the relationship between visitors' behavior and their satisfaction at Natural History Museum (NHM). This study involves 204 participants including elementary, middle, and high school students, their teachers and parents, and university students from Korea. The results are tested using crosstabs and chi-square. The main results are as follows: First, dominant behavior involves visiting with family, visiting for leisure and just visiting, viewing exhibits utilizing explanation cards, and visiting for over 2 hours. Second, the degree of satisfaction tends to be high in visiting with family or alone, visiting for interest in science, and viewing exhibits utilizing explanation cards or explanation by a parent, teacher, or a guide. While, third, the degree of satisfaction tends to be low in visiting with a school group, visiting for leisure/just visiting, or visiting for homework research, and viewing exhibits without any guidance. Forth, the relationship between length of visits and degree of satisfaction is positively significant.

• Journal of the Korean Society of Clothing and Textiles
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• v.45 no.6
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• pp.1035-1051
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• 2021

This study compares the strength properties of Jumchi-Hanjis dyed with 70% and 100% persimmon juice concentrations and undyed Jumchi-Hanjis. The Juumchi-Hanjis were made from Dakjis (mulberry papers), which were mixed with different ratios of fibers from paper mulberries originating in Korea and Thailand, including wood pulp from Canada. Research results showed that tensile, wet tensile, and bursting strengths of Jumchi-Hanjis dyed with 70% concentration were higher than those of undyed Jumchi-Hanjis. However, the tearing strengths of the dyed Jumchi-Hanjis were lower than those of undyed Jumchi-Hanjis. The wet tensile strengths of Jumchi-Hanjis dyed with 100% concentration were higher than those of dyed with 70% concentration. The increase and decrease of tensile, tearing, and bursting strengths depending on persimmon juice dyeing differed as per the mixing ratio of the raw materials of Jumchi-Hanjis. Dyeing with 100% persimmon juice concentration tends to be more useful than 70% to increase the tensile (MD) and wet tensile strengths of Jumchi-Hanjis containing only Korean mulberry fibers (90%) and wood pulp (10%) as raw materials. Dyeing with 100% concentration tends to be less useful than 70% to increase the tensile, tearing and bursting strengths of Jumchi-Hanjis with high proportions (90% or 60%) of mulberry fibers from Thailand.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.4
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• pp.647-654
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• 2018

This study examines the literature regarding teacher-child interaction in the classroom, aiming to find ways to support child-care teachers in improving the quality of teacher-child interaction. The study selected studies exploring teacher-education programs that aim to support child-care teachers in interacting with their children in the classroom in a quality manner. The selected studies were analyzed, by focusing on how the study proposes ways to support child-care teachers in interacting with their children in a quality manner. The results of previous studies are as follows: 1) the literature tends to focus on teachers' language interaction with their children in the classroom; 2) the literature tends to apply a variety of observation tools (or coding schemes) to measure teacher-child interaction in child-care settings; 3) the literature prefers individualized approaches such as mentoring or consulting as ways of supporting child-care teachers in interacting with their children in a quality manner; and 4) the literature aims in general to improve teachers' self-reflection skills.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.11a
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• pp.175-176
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• 2022

By studying the characteristics of matrix insulated through heat generated through oxidation of iron powder, the basic research results on the possibility of buffering and applicability of Cold weather concrete as a curing method are presented. In order to prevent freezing due to a sharp decrease in temperature in the initial stage of curing, iron powder (Fe), powder activated carbon, which is a small amount of porous carbonaceous adsorbent, and salt (NaCl) as an oxidizing agent are replaced with iron powder admixture. As the curing temperature increases, the strength tends to increase, and when replacing the admixture at the same curing temperature, the strength slightly decreases. This is determined as a result of generating iron oxide through an oxidation reaction of iron powder, activated carbon, and NaCl generating a large amount of pores in the matrix. In addition, the internal temperature tends to increase as the mixing substitution rate increases, and it is judged that the oxidation heat of the iron powder mixture affects the increase of the internal temperature during curing. The higher the replacement rate of the iron powder mixture, the slightly lower the strength, but it is determined that freezing and melting that may occur in the early stage of curing can be prevented due to an increase in the initial internal temperature.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1244-1248
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• 2003

This paper describes visual tracking procedure of the underwater mobile robot for nuclear reactor vessel inspection, which is required to find the foreign objects such as loose parts. The yellowish underwater robot body tends to present a big contrast to boron solute cold water of nuclear reactor vessel, tinged with indigo by Cerenkov effect. In this paper, we have found and tracked the positions of underwater mobile robot using the two color information, yellow and indigo. The center coordinates extraction procedures are as follows. The first step is to segment the underwater robot body to cold water with indigo background. From the RGB color components of the entire monitoring image taken with the color CCD camera, we have selected the red color component. In the selected red image, we extracted the positions of the underwater mobile robot using the following process sequences; binarization, labelling, and centroid extraction techniques. In the experiment carried out at the Youngkwang unit 5 nuclear reactor vessel, we have tracked the center positions of the underwater robot submerged near the cold leg and the hot leg way, which is fathomed to 10m deep in depth.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.213-218
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• 1996

Characteristics of high density U-Mo alloy powder prepared by centrifugal atomization have been examined. The results indicate that the majority of the atomized U-Mo alloy particles has a smooth surface and frequently near-perfect spheroidal shape with few satellites attached. The size distribution of atomized U-Mo alloy powder shows the mono-modal size distribution seen in ligament disintegration mechanism. All phases of atomized alloy powder below 150$\mu\textrm{m}$ irrespectively to particle size are found to be ${\gamma}$-U (cubic structure) phases with isotropic structure and not to be U$_2$Mo phase at all. The microstructure of atomized U-Mo alloy particulates has micro-crystalline structure with non-dendritic gram supersaturated with Mo element. Also the grain size of ${\gamma}$ -U tends to decrease with the decrease of the powder diameter.

• Journal of Magnetics
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• v.16 no.3
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• pp.318-321
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• 2011

A new Fe-based amorphous compound powder was prepared from Fe-Si-B amorphous powder by crushing amorphous ribbons as the first magnetic component and Fe-Cr-Mo metallic glassy powder by water atomization as the second magnetic component. Subsequently by adding organic and inorganic binders to the compound powder and cold pressing, the new Fe-based amorphous compound powder cores were fabricated. This new Fe-based amorphous compound powder cores combine the superior DC-Bias properties and the excellent core loss. The core loss of 500 kW/$m^3$ at $B_m$ = 0.1T and f = 100 kHz was obtained When the mass ratio of FeSiB/FeCrMo equals 3:2, and meanwhile the DC-bias properties of the new Fe-based amorphous compound powder cores just decreased by 10% compared with that of the FeSiB powder cores. In addition, with the increasing of the content of the FeCrMo metallic glassy powder, the core loss tends to decrease.

• Journal of the Korean Institute of Landscape Architecture
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• v.31 no.6
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• pp.129-135
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• 2004

This study reviews the research trends of landscape ecology, geographical information system(GIS) and remote sensing(RS) that have appeared in articles published in the Journal of the Korean Institute of Landscape Architecture over the last 30 years. The aim is to identify the research characteristics in Korea. There were 905 papers published in the journal during this period. There were 35 papers concerning landscape ecology, and 26 papers concerning GIS/RS, which are few compared to other research fields. The papers were classified chronologically, and reviewed in terms of their contents. In the seventies and eighties, papers were contributed from other disciplines, e. g., forestry, and also included translated papers from foreign sources. However, in the nineties, the number of papers grew continuously. During the fist half of nineties, six papers were published. However, 30 papers were published during the last half of nineties, which shows a rapid increase in the number of papers contributed. From 2001 to 2003, there were 17 papers published. Overall, there tends to be an increase in the number of papers contributed and published.