• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.699-710
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• 2006

Batch scale experiments to investigate the efficiency of the solidification process for metal mine tailing treatment were performed. Portland and MSG (micro silica pouting) cements were used as solidifier and three kinds of mine tailings (located at Gishi, Daeryang, and Aujeon mine) were mixed with cements to paste solidified matrices. Single axis com-pressible strengths of solidified matrices were measured and their heavy metal extraction ratios were calculated to investigate the solidification efficiency of solidified matrices created in experiments. Solidified matrices ($5cm{\times}5cm{\times}5cm$) were molded from the paste of tailing and cements at various conditions such as different tailing/cement ratio, cement/water ratio, and different cement or tailing types. Compressible strengths of solidified matrices after 7, 14, and 28 day cementation were measured and their strengths ranged from 1 to $2kgf/mm^2$, which were higher than Korean limit of compressible strength for the inside wall of the isolated landfill facility ($0.21kgf/mm^2$). Heavy metal extractions from intact tailings and powdered matrices by using the weak acidic solution were performed. As concentration of extraction solution for the powdered solidified matrix (Portland cement + Gishi tailing at 1:1 w.t. ratio) decreased down to 9.7 mg/L, which was one fifth of As extraction concentration for intact Gishi tailings. Pb extraction concentration of the solidified matrix also decreased to lower than one fourth of intact tailing extraction concentration. Heavy metal extraction batch experiments by using various pH conditions of solution were also performed to investigate the solidification efficiency reducing heavy metal extraction rate from the solidified matrix. With pH 1 and 13 of solution, Zn and Pb concentration of solution were over the groundwater tolerance limit, but at pH $1{\sim}13$ of solution, heavy metal concentrations dramatically decreased and were lower than the groundwater tolerance limit. While the solidified matrix was immerged Into very acidic or basic solution (pH 1 and 13), pH of solution changed to $9{\sim}10$ because of the buffering effect of the matrix. It was suggested that the continuous extraction of heavy metals from the solidified matrix is limited even in the extremely high or low pH of contact water. Results of experiments suggested that the solidification process by using Portland and MSG cements has a great possibility to treat heavy metal contaminated mine tailing.

• Restorative Dentistry and Endodontics
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• v.24 no.3
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• pp.473-481
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• 1999

This study evaluated the shear bond properties of IPS Empress glass ceramic to enamel and dentin surfaces with three ceramic surface treatments, and three resin cements. The influence of thermocycling was also investigated. The purpose of this study was to investigate the influences of resin cements, ceramic surface treatments, and thermocycling on shear bond properties. Ninety freshly extracted, noncarious human molars were selected for this study. The surface treatments of ceramic were etching <5.0% hydrofluoric acid, application of silane coupling agents(Tokuso Ceramic Primer, Clearfil porcelain bond, Monobond-S), and the combination of the two methods. Empress cylinders were bonded to enamel and dentin surfaces with three kinds of resin cements(Bistite resin cement, Panavia 21, Variolink). The specimens were aged in $37^{\circ}C$ distilled water for 24 hours. Half of the specimens were then thermocycled 500times between $5^{\circ}C$ and $55^{\circ}C$ with a dwell time of 15 seconds. Each specimen was debonded in shear mode and measured shear bond properties by using the universal testing machine(Zwick 020, Germany). The data were analyzed by SPSS/PC+(one-way ANOVA, Scheffe' s test and t-test). The results were as follows : 1. Without thermocyling, there was significant difference of shear bond strength to enamel surface between Bistite Resin Cement and Panavia 21 in case of etched and silane-treatment(p<0.05). 2. Without thermocyling, the shear bond strength of a group treated with silane and etching was significantly higher than that of a group treated with silane or etching with the application of Panavia 21 and Variolink(p<0.05). 3. A group treated with etching with the application of Variolink only showed a decrease of shear bond strength after thermocycling(p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.237-245
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• 2000

For the purpose of comparing the bond strengths of some tooth adhesive restoration materials on primary enamel and dentin, 4 kinds (7 brands) of restorative materials including a composite resin (Z 100), a conventional glass ionomer cement (Chem-Flex), 2 brands of resin-modified glass ionomer cements (Fuji II LC-I, Vitremer), and 3 brands of compomers(Dyract AP, F2000, Compoglass) were investigated using UTM for measuring the shear bond strengths. Additionally the failure modes were examined by histologically observing the fractured surfaces of each specimen. The following results were obtained. 1. The shear bond strengths of Z 100 to the primary enamel were higher than those of other experimental materials except Fuji II LC-I, which showed significantly higher bond strength than Chem-Flex or Vitremer (P<0.05). 2. The shear bond strengths of Z 100 to the primary dentin were higher than those of other experimental materials except Dyract AP and Fuji II LC-I, both of which showed significantly higher shear strength than Chem-Flex or Vitremer (P<0.05). 3. The shear bond strengths of all restorative materials except Dyract AP showed relatively higher values to enamel surface than to dentin surface. In Dyract AP, the reverse was true significantly. 4. All materials examined showed cohesive failures except some Chem-Flex and Vitremer, which showed adhesive failures.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.84-90
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• 2012

Patents in Korea, Japan and the U.S. were searched at the Korea Intellectual Property Rights Information Service (KIPRIS) of Korea Institute of Patent Information using related keywords in order to analyze the trend of patents on the usage of waste wood. Materials on a total of 77 patents in Korea, 317 patents in Japan, and 316 patents in the U.S. that had been registered as patents as of Dec. 31, 2011 were collected. Among the collected materials, the patents rejected, expired, annulled, withdrawn and waived as well as those which had little relationship with waste wood were excluded and the 71 patents in Korea, 227 patents in Japan and 216 patents in the U.S. were finally selected for analysis. In addition, the properties of the mortar which used waste wood as an alternative for a part of the fine aggregate were tested as a basic study for the usage of waste wood as a lightweight aggregate for concrete. For the test, the waste wood of the pine tree was crushed, sifted through No. 8(2.4 mm) sieve, and then dried for 24 hours at $100{\pm}5^{\circ}C$. As it is known that some kinds of tree prevent the hardening of cement when the wood is mixed with cement, the crushed waste wood in this study was dipped in the water of $20^{\circ}C$, $50^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$ and then dried up before testing the properties of the mortar to examine the effect of the preliminary treatment of crushed waste wood.

• Tunnel and Underground Space
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• v.28 no.2
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• pp.156-169
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• 2018

The relationship between the mechanical and textural properties of sedimentary rocks has been studied for decades. However, inconsistencies in the results have arisen from both the inhomogeneity of natural rocks and the difficulties encountered in controlling just one textural factor of interest in each experiment. This work produced artificial sedimentary rocks to enable control of every independent parameter at all times. Their homogeneity lowered the deviation of the results, and thus they produced clearer correlations than for natural rocks. The samples were made by mixing bassanite powder with water and silica sand, which produced rocks consisting of sand and gypsum cement. The effect of grain content and size on mechanical properties such as uniaxial compressive strength, Young's modulus, and seismic velocity was estimated. Increasing grain content lowered the compressive strength but raised Young's modulus and seismic velocity. Overall, grain size did not linearly affect the mechanical properties of the samples, but affected them in some way. In future, these results can be compared and integrated with similar experiments using different cement or grain types. This should allow comparison of the effects of the rock constituents themselves and their interactions, with applicability to all kinds of sedimentary rocks.

• Journal of Korean Society of Disaster and Security
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• v.7 no.2
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• pp.25-34
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• 2014

This study researches on global technology trend in each of composing technology, such as grouting material, grouting equipment, and construction management technology, which grouting technology has been founded upon to improve relatively inadequate domestic grouting technology and to establish the global standard for overseas expansion in the future. As far as grouting material is concerned, while High-Penetration and High-Strength micro cement ($1.5{\mu}m$) has been developed in 2000's in Japan, JinChun Kim et al. (2014) has been developing hybrid type micro cement grouting material and examining specifications of different kinds of projects and countries to analyze the trend of grouting equipment development. The specification contains detailed requisite specification for materials, mixers, pumps, agitators, and packers and it has to satisfy the standard of different countries to win global contracts. Grouting management technology can be divided into four different generations and Scandinavian countries, such as Sweden, Norway, and Finland, Japan, and South Korea are recently doing vigorous researches on the Fourth generation which merges grouting technology with ICT.

• Geophysics and Geophysical Exploration
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• v.12 no.4
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• pp.328-337
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• 2009

To investigate the relation between pore fluid conductivity and bulk resistivity of a rock sample it is assumed that electrolyte solution perfectly substitute the pore fluid that occupied the pore space within the sample in general. In this study, it is investigated that how much can the electrolyte solution substitute the pore fluid by repeating the same saturation process. Four kinds of NaCl solutions of 8, 160, 3200, 64000 ${\mu}S$/cm are used. The saturation process has repeated four times for each electrolyte in increasing conductivity order first then four times each in decreasing order. The more the saturation process repeated with the same electrolyte, the more electrolyte solution substitute the pore fluid. Geometric mean of bulk resistivity in increasing and decreasing orders with the same electrolyte solution is assumed to be mostly close to the bulk resistivity with perfect substitution. Bulk resistivity measurements for both increasing and decreasing order differs within 10% to the geometric mean when repeating the saturation process 4 times while maximum 40% difference is observed when single saturation process for each electrolyte solution with increasing order. The modified parallel resistant model can generally represent the relations between pore fluid resistivity and bulk resistivity in the experiment, but more experimental data with various rock samples with different porosity is needed to generalize the model.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.1
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• pp.25-42
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• 1992

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from a unilateral distal extention removable partial dentures with five kinds of the direct retainers, that is, the bilaterally designed bar clasp of the cross-arch lingual bar and the unilaterally designed bar clasp, circumferential clasp, mini-Dalbo attachment, and telescope retainer. A photoelastic model for mandible was made of the epoxy resin(PL-1) and hardner (PLH-1) with the acrylic resin teeth used and was coated with plastic cement-1 at the lingual surface of the model, and then five kinds of removable partial dentures were set, A unilateral vertical load of about 16Kg was applied on the first molar and the stress pattern of the photoelastic model under each condition was analyzed by the reflective circular polariscope. The following results were obtained: 1. The conventional removable partial denture with the bilaterally cross arch lingual bar produced the most favorable stress distribution on the residual ridge and supporting structure of abutment teeth than the unilaterally designed removable partial dentures. 2. The unilaterally designed removable partial denture with the bar clasp produced the stress distribution on the residual ridge, except sligtly higher stress concentration on the supporting structure of the abutment teeth, similar to the conventional removable partial denture with the bilaterally designed cross arch lingual bar. 3. On the unilaterally designed removable partial dentures, the bar clasp produced greater stress distribution on the residual ridge and supporting structure of the abutment teeth than the circumferential clasp. 4. On the unilaterally designed removable partial dentures, the mimi-Dalbo attachment produced relatively higher stress concentration on the residual ridge, but produced lesser stress concentration on the supporting structure of the abutment teeth than the other direct retainers. 5. On the unilaterally designed removable partial dentures, the telescope retainer produced uniform stress distribution on the residual ridge, but produced higher stress concentration at the root apex of the terminal abutment tooth than the other direct retainers. 6. On the unilaterally designed removable partial dentures the circumferential clasp and telescope retainer produced slightly higher stress concentration on the residual ridge and supporting structure of the abutment teeth than the bar clasp and mini- Dalbo attachment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.2
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• pp.536-544
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• 2016

Recently, with the increase in the number of high rise and huge scaled buildings, ultra-high strength concrete with 80~100 MPa has been used increasingly to withstand excessive loads. Among the components of concrete, the effects of the kinds and properties of fine aggregates on the performance and economic advantages of ultra-high strength concrete need to be evaluated carefully. Therefore, this study examined the effects of the type of fine aggregates and mixing methods on the engineering properties of ultra-high strength concrete by varying the fine aggregates including limestone fine aggregate (LFA), electrical arc slag fine aggregate (EFA), washed sea sand (SFA), and granite fine aggregate (GFA) and their mixtures. Ultra-high strength concrete was fabricated with a 20 % water to binder ratio (W/B) and incorporated with 70 % of Ordinary Portland cement: 20 % of fly ash:10 % silica fume. The test results indicate that for a given superplasticizer dose, the use of LFA resulted in increases in slump flow and L-flow compared to the mixtures using other aggregates due to the improved particle shape and grading of LFA. In addition, the use of LFA and EFA led to enhanced compressive strength and a decrease in autogenous shrinkage due to the improved elastic properties of LFA and the presence of free-CaO in EFA, which resulted in the formation of C-S-H.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.379-400
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• 1992

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from the mandibular distal extension removable partial dentures with the mesial or distal placement of the occlusal rest and the mesial or distal connection in the back-action clasp with the five various designs of the back-action clasp, that is, the mesial connection and the distal rest, the distal connection and mesial rest, the mesial connection and mesial rest, the distal connection and the mesial and distal rest, and the mesial connection, and the mesial and distal rest. A photoelastic model was made of the epoxy resin(PC-1) and the hardner(PLH-1) with the acrylic resin teeth used and was coated with the plastic cement-1 at the lingual surface of the model and then five kinds of the removable partial dentures on the photoelastic model were set. A unilateral vertical load of 12.5 kg was applied on the central fossa of the first molar with the use of specially designed loading device and the pattern and distribution of the stress of the photoelastic model under each condition was analyzed by the reflective circular polariscope. The following results were obtained. 1. In the back-action clasp with the mesial connection and mesial rest of the case 3, the effect of the stress distribution was the most favorable. 2. In the back-action clasp with the mesial and distal rest, of the case 4 and 5, the stress distribution was more greatly showed in the terminal abutment. 3. Generally, the stress distribution was more favarable in the mesial connection than in the distal connection. 4. In the back-action clasp with the mesial connection of the case 1, 3 and 5, the stress distribution was the most favorable in the mesial rest.