• Transactions of the Korean hydrogen and new energy society
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• v.29 no.3
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• pp.280-291
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• 2018

Torrefaction is one of the methods to increase combustion calorific value and hydrophobicity of biomass. In this study, the effects of torrefaction on devolatilization, char reactivity and biomass structure were analyzed. Empty fruit bunch (EFB) and Kenaf biomass were used as fuels to be torrefied in the N2 environment at 200, 250 and $290^{\circ}C$. Devolatilization and char kinetics were analyzed by using TGA and biomass structure was investigated through petrography image. The reactivity showed different trends depending on the torrefaction temperature and biomass structure. The herbaceous biomass, Kenaf, was shown as high reactivity and thin wall structure. On the contrary, the woody biomass, EFB, had relatively low reactivity and thick wall structure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.405-406
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• 2005

A theoretical investigation of the solid-phase mechanochemical synthesis of nano-sized target product on the basis of dilution of the initial powdered reagent mixture by another product of an exchange reaction is presented. On the basis of the proposed 3-mode particle size distribution in mechanically activated mixture, optimal molar ratios of the components in mixture are calculated, providing the occurrence of impact-friction contacts of reagent particles and excluding aggregation of the nanosized particles of the target reaction product. Derivation of kinetic equations for mechanochemical synthesis of nanoscale particles by the final product dilution method in the systems of exchange reactions is submitted. On the basis of obtained equations the necessary times of mechanical activation for complete course of mechanochemical reactions are designed. Kinetics of solid phase mechanosynthesis of nano-TlCl by dilution of initial (2NaCl + $Tl_2SO_4$) mixture with the exchange reaction product (diluent, $zNa_2SO_4$, $z=z^*=11.25$) was studied experimentally. Some peculiar features of the reaction mechanism were found. Parameters of the kinetic curve of nano-TlCl obtained experimentally were compared with those for the model reaction KBr + TlCl + zKCl = (z + 1) KCl + TlBr ($z=z_l^*=13.5$), and for the first time the value of mass transfer coefficient in a mechanochemical reactor with mobile milling balls was evaluated. Dynamics of the size change was followed for nanoparticle reaction product as a function of mechanical activation time.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1163-1168
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• 2019

Hydrodynamic properties have been investigated for promising extraction systems: $0.05mol\;L^{-1}$ solutions of di(N-ethyl-4-ethylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid, di(N-ethyl-4-fluoroanilide) of 2,6-pyridinedicarboxylic acid and di(N-ethyl-4-hexylanilide) of 2,2'-bipyridine-6,6'-dicarboxylic acid in meta-nitrobenzotrifluoride (F-3) or trifluoromethylphenyl sulfone (FS-13) diluents. To evaluate the perspectives for their use as extraction mixtures at the final stage of the nuclear fuel cycle, the change in density, viscosity, surface tension, and phase separation rate under irradiation with accelerated electrons was studied. The concentrations of extractants in the irradiated mixtures have been determined and the radiation-chemical yields have been calculated. Irradiation significantly decreases the phase separation rate at the stages of extraction and back extraction for all the studied systems. The viscosity of the DYP-7 solution in FS-13 increase above the values suitable for its use in extraction processes.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.65-77
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• 2022

Determination of strength properties of intact rock using artificial cores has been considered in recent years. In this study, some relationships for estimating the static properties of dolomudstone cores of the Asmari reservoir were presented using artificial cores prepared from cuttings of two wells, southwest of Iran. For this purpose, first natural cuttings (NC) and 33 cores including dolomite limestone (dolomudstone), anhydrite and anhydrite dolomite were prepared between depths of 1714 and 2208 meters. Petrographic, physical, mechanical and dynamic tests were performed on cores, NC and artificial cuttings (AC) which was prepared from the residuals of dolomudstone cores. For preparing the artificial cores, the average porosity of the dolomudstone cores was considered and determined using four methods. Artificial and natural cuttings were classified as dolomite limestone and dolomite limestone to calcareous dolomite, respectively. Using ordinary Portland cement (OPC), water, AC and NC artificial cores were prepared. Results of evaluating the proposed relationships using statistical criteria showed that the static properties of the artificial cores can be used to predict the static properties of the dolomudstone cores.

• Journal of the Korean association of regional geographers
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• v.11 no.4
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• pp.440-452
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• 2005

The granites in the Gyeongju area are represented by the Namsan granites and the Tohamsan granodiorites. In this study I examined the geomorphological and geological characteristics of the granite landforms in the Gyeongju area. Joint, tor and corestones are most identifiable geomorphological and geological structure in the study areas. Tor in the Namsan granites is well developed and mainly composed of cubic corestones. Petrographical features of the stones used for the stone-built cultural properties are compared with those of the granites cropped out nearby. Additionally radiogenic element contents (K, Th, U) were acquired for comparison by gamma-ray spectrometer analysis. Most stones from the stone-built cultural properties in the Bulguksa Temple are very similar to the Namsan granites in terms of petrography, radiogenic elements. On the contrary almost all stones from the Seokguram Grotto share common petrographical, physical and chemical characteristics with the Tohamsan granodiorites. Therefore it can be suggested that the stones in the Bulguksa Temple were supplied from Namsan, and that the stones in the Seokgurarn Grotto were collected at nearby Tohamsan.

• Economic and Environmental Geology
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• v.28 no.2
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• pp.123-137
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• 1995

The Mesozoic Geumsan granitic rocks of various composition are distributed in the Geumsan district, the central part of the Ogcheon Fold Belt. About 40 ore deposits of $CaF_2{\pm}Au{\pm}Ag{\pm}Cu{\pm}Pb{\pm}Zn$ are widely distributed in this district and are believed to be genetically related to the granitic rocks. Based on their petrography and geochemistry, the granitic rocks in this district can be classified into two groups ; the Group I( equigranular leucocratic granite, porphyritic biotite granite, porphyritic pink-feldspar granite, seriate leucocratic granite) and the Group II(seriate pinkfeldspar granite, equigranular alkali-feldspar granite, equigranular pink-feldspar granite, miarolitic pink-feldspar granite, equigranular biotite granite). Interpreted from their isotopic dating data and geochemical characteristics, the Group I and the Group II are inferred to be emplaced during the Jurassic(~184Ma), and the Cretaceous to the early Tertiary period(~59Ma), respectively. Both Group I and Group II generally belong to magnetite-series granitoids. The Cretaceous granitic rocks of Group II are more highly evolved than those of the Jurassic Group I. The Rb-Sr variation diagram suggests that the granitic rocks of the Jurassic Group I and of the Cretaceous Group II be evolved mainly during the processes of fractional crystallization and partial melting, respectively.

• Journal of Conservation Science
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• v.30 no.2
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• pp.189-203
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• 2014

In this study, the identification and distribution for rock types of the South Gate Wall of Myeoncheoneupseong Town Wall in Dangjin was investigated, and the homogeneity analysis of rock properties in the wall between the surrounding out crops estimated by examining the possible provenances. The Town Wall consists of variable rock types about 15 kinds. Granitic rocks (61.0%), quartzite (21.0%) and quartz feldspar porphyry (8.7%) accounted over 90% of total survey section. These rock properties are very similar to surrounding rocks of the Town Wall on the basis of occurrences, magnetic susceptibility, petrography, mineralogical and goechemical characteristics. Thus, it is probable that the rock properties of the Town Wall were supplied from the Town Wall around about 8km within at Seongsangri, Yangyuri, Seongbukri, Galsanri and Daedeokdong area. And supplied rock properties in the construction process, easy procurement rather than rock type was most likely seems to be considered.

• The Journal of the Petrological Society of Korea
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• v.12 no.2
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• pp.55-69
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• 2003

A spinifex textured komatiite sample of Early Tertiary age, from the Gorgona Islands of Colombia in South America, was petrographically and geochemically studied, and compared with the previous researches of the komatiites including other Precambrian komatiites in South Africa, Western Australia and Canada. The sample shows the komatiitic characteristics in its petrography and geochemistry very well, i.e. in high specific gravity (2.98) and density (3.2), rock forming minerals, spinifex texture, major and race element abundances and REE pattern. In particular the REE pattern for it strongly suggests that the Gorgona komatiite must have been crystallized from a magma generated from a depleted mantle as that of Munro Township area in Ontario, Canada which is pyroxenite komatiite or basaltic komatiite of Group I of the Archean.

• The Journal of the Petrological Society of Korea
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• v.22 no.4
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• pp.263-272
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• 2013

We investigated the lithology and petrography of granites and metasedimentary rocks in Deokjeok Island at the western margin of the Gyeonggi massif. The major lithology comprises the biotite granite that intrudes all other types of rocks. A minor amount of mylonitized porphyritic granite crops out along the southeastern coast. Metasedimentary rocks in the north are further divided into: (1) sheared quartzite-schist to the northeast; and (2) relatively less-deformed, low-grade metasedimentary rocks to the northwest. The former contains quartz grains showing undulatory extinction and subgrain aggregates as well as minor amount of primary chlorite and biotite in the muscovite-rich matrix. Metamorphic condition belongs to the greenschist facies or the biotite zone. On the other hand, the latter unit consists of meta-conglomerate, meta-sandstone, meta-pelite, and black slate. Regardless of the lithology, the intensity of deformation apparently increases eastward to develop the flow banding of quartz in the shear zone.

• Journal of Conservation Science
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• v.29 no.1
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• pp.1-14
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• 2013

The Hongjimun Ogansumun (Five-arched floodgates) is composed mainly of biotite granite, pink feldspar granite and granodiorite that are very similar with granitic rocks around the Seoul. Main damage in the floodgates was gray, yellow and predominantly white discoloration on the surface of stone blocks. All floodgates showed more discoloration in the wall than ceiling, and there were growing stalactite on the ceiling. Scientific analyses determined that the white discoloring substrates were mainly calcite. Therefore, conservation treatment was carried out to remove the substrates by using dry cleaning, high pressure cleaning and chemicals. The floodgates have been restored to good state, but it is still significantly necessary to install drainage on the top of the gates.