• Geomechanics and Engineering
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• v.35 no.1
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• pp.95-108
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• 2023

Soft soil ground is a crucial factor limiting the development of the construction of transportation infrastructure in coastal areas. Soft soil is characterized by low strength, low permeability and high compressibility. However, the ordinary treatment method uses Portland cement to solidify the soft soil, which has low early strength and requires a long curing time. Microbially induced carbonate precipitation (MICP) is an emerging method to address geo-environmental problems associated with geotechnical materials. In this study, a method of bio-cementitious mortars consisting of MICP and cement was proposed to stabilize the soft soil. A series of laboratory tests were conducted on MICP-treated and cement-MICP-treated (C-MICP-treated) soft soils to improve mechanical properties. Microscale observations were also undertaken to reveal the underlying mechanism of cement-soil treated by MICP. The results showed that cohesion and internal friction angles of MICP-treated soft soil were greater than those of remolded soft soil. The UCS, elastic modulus and toughness of C-MICP-treated soft soil with high moisture content (50%, 60%, 70%, 80%) were improved compared to traditional cement-soil. A remarkable difference was observed that the MICP process mainly played a role in the early curing stage (i.e., within 14 days) while cement hydration continued during the whole process. Micro-characterization revealed that the calcium carbonate filling the pores enhanced the soft soil.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.2
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• pp.47-53
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• 2004

In this experiment the effects of the packing structure of pigment on the surface characteristics (smoothness and gloss) of coated paper are studied. Four different kinds of inorganic pigments(clay), ground calcium carbonate(GCC), two of precipitated calcium carbonates(PCC), and two organic pigments(solid bead and hollow type) were used. The method of measuring the relative sediment volume(RSV) was used to analyze the packing structure of coating layer. The relative sediment volume was measured, using the pressure dewatering dry-cake method(PDDM) and centrifuge method. Also, the particle size distribution of coating pigment was determined. The results showed that small amount of organic pigment, added to inorganic pigment, improved smoothness and its effect was greater when GCC was used as inorganic pigment. The efficiency of organic pigment depended upon the inorganic pigment since the organic pigment is packed in the pores formed by the inorganic pigment.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.46 no.5
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• pp.27-34
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• 2014

In-situ $CaCO_3$ formation onto recycled wood pulp was studied to improve optical properties and ash attachment to the fiber furnish in papermaking. We controlled initial reaction temperature of in-situ $CaCO_3$ formation method from $30^{\circ}C$ to $50^{\circ}C$. It was found that the attachment of newly formed $CaCO_3$ to recycled fibers, old newspaper (ONP) in this case, was stronger than that of ground calcium carbonate (GCC, mean dia. $2.4{\mu}m$) addition case, but was not much different among those formed at different temperature. Morphologies of newly formed $CaCO_3$ were changed according to the reaction temperature. More aragonite shape was seen at higher temperature. In-situ $CaCO_3$ formation increased brightness and lowered ERIC value of ONP sheet greatly at the same level of ash contents when compared to GCC addition method, but gave equivalent ERIC and brightness when compared to those of the precipitated calcium carbonate (PCC) addition method. However, tensile strength of the handsheets of the in-situ $CaCO_3$ formation method were much greater than those of the PCC addition method.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.2
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• pp.62-73
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• 1998

The aim of this work was to investigate the effects of pigment composition on the calendering response and structure of the coated paper. Calendering response of the coated paper was determined from the gloss values of the uncalendered and calendered coated papers, and the relationship between gloss and coating structure was discussed. The surface and cross section of the coating layer was observed using a scanning electron microscope to examine the coating structure. Coating layers were hardened in epoxy resin and polished with carbimet paper disc for preparing SEM samples. Maximum calendering response was obtained for the coated paper prepared from 80pph of clay and 20pph of ground calcium carbonate (GCC) as pigments. Photomicrographs of the surface and cross section of the coating layer show that clay tends to form dense coating structure, while GCC tends to form bulky coating layer.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.48 no.2
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• pp.83-90
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• 2016

Increasing the amount of filler in paper is of high interest for paper industry while maintaining its key sheet quality properties. In this study, a MFC-GCC composite, made through a co-grinding NBSK (Northern bleached softwood kraft) pulp with a ground calcium carbonate (Intracarb 60), was used as a strength aid in paper in order to evaluate a potential cost reduction through filler increase without sacrificing paper quality. Hand-sheets were made of NBSK and/or eucalyptus pulp by using white water recirculation in a Tappi sheet former and was compared its properties without or with MFC additions at different filler levels. It was found that the MFC-GCC composite has a large surface area compared to the fiber, allowing the formation of more hydrogen bonds in the web, thus giving natural strength to the paper. Overall results are encouraging that the MFC-GCC composite allows papermaker to reduce basis weight and maintain critical sheet properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.449-452
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• 2003

The objective of this study is to investigate the basic properties of polyester mortars using ground calcium carbonate(GCC), blast furance slag(BFS), fly ash(FA), ordinary portland cement(OPC) as fillers. Particle size distribution, particle shape and resin absorption of GCC, BFS, FA and OPC are checked. Polyester mortars with GCC, BFS, FA and OPC are prepared with various MEKPO content and tested for working life. The flexural and compressive strengths of the polyester mortars with MEKPO content of 0.5phr are evaluated. As a test result, the average sizes of GCC, BFS, FA and OPC are 9.7$\mu\textrm{m}$, 11.6$\mu\textrm{m}$, 21.2$\mu\textrm{m}$, 29.9$\mu\textrm{m}$. Resin absorption of FA is 1.5times larger than other fillers. The polyester mortar with FA at a MEKPO content of 0.5phr has the longest working life and the maximum flexural and compressive strengths.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.2
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• pp.77-85
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• 1999

A study on the thermal stability of commonly used six fillers, such as titanium dioxide, silica, ground calcium carbonate, zeolite, and, clay, showed that most fillers except titanium dioxide were strongly effected by heat treatment. Therefore, the present methods for determination of ash in paper give weight loss due to thermal decomposition of fillers. It was found that a paper ashing method at a temperature of 40$0^{\circ}C$ allows most fillers in their original and undecomposed from. Results presented in this paper also show that X-ray diffraction can be used for qualitative determination of mixed fillers and coating pigments in a paper sheet.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2011.10a
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• pp.421-428
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• 2011

• 보존과학연구
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• s.15
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• pp.59-103
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• 1994

Painting is well regarded as a stratified structure by the conservators and restorers. Hence, the scientific methods have been developed for the study of the interal layer of paintings. Examples of such methods are X-ray, infra-red, and ultra-violet photography. A more direct method is to look at the painting in cross section under the microscope and to analyze pigments using an electron probe X-ray micro analyzer(EPMA).In this research, I study and analyze twenty two Korean paintings of self-portraits including the first oil painting of Hui Dong Koh's self-portrait stored in the museum of Tokyo National University of Fine Arts and Music, employing these scientific techniques. The small fragments taken from the ground layers of the early oil paintings(1915∼1942)are analyzed using the EPMA. According to their main materials, the ground layers can be classified into five types ; 1. Lead white layer and double layer of calcium carbonate and lead white, 2. Zinc white with some mixiture of lead white, 3.Titanium white with some barium white, 4. Barium white, 5.Double layer of titanium white and zinc white.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.40 no.5
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• pp.323-331
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• 2007

Barren ground is an abnormal phenomenon in coastal ecosystems where seaweeds are destroyed and largely replaced by coralline algae containing calcium carbonate components. To restore the seaweed forest, we attempted reconstruction in an area of Samcheok, Korea, where barrenness is extensive. We developed two methods of seaforest construction underwater longline and seed transplantation for the brown seaweed Laminaria japonica, a fast-growing edible seaweed. The blade length of L. japonica attached to an underwater long line was $93.9{\pm}38.2cm$ and blade weight $7.6{\pm}2.1g$ in February 2004. Seaweed size declined after August 2004. A Similar pattern was observed using the transplantation method with maxima of $179.3{\pm}40.3cm\;and\;14.9{\pm}3.2g$ for blade length and weight, respectively in July 2004. The transplanted seaweeds matured in October as did a wild population. These results indicate that transplanted seaweed acclimate to new environments.