• Journal of the Mineralogical Society of Korea
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• v.17 no.3
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• pp.277-288
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• 2004

Alkali-silica reaction (ASR) is a chemical reaction between alkalies in cement and chemically unstable aggregates and causes expansion and cracking of concrete. In the Present study, we studied the effects of metakaolin, which is a newly introduced mineral admixture showing excellent pozzolainc reaction property, on the inhibition of ASR. We prepared mortar-bars of various replacement ratios of metakaolin and conducted alkali-silica reactivity test (ASTM C 1260), compressive strength test and flow test. We also carefully analyzed the mineralogical changes in hydrate cement paste by XRD qualitative analysis. The admixing of metakaolin caused quick pozzolanic reaction and hydration reaction that resulted in a rapid decrease in portlandite content of hydrated cement paste. The expansion by ASR was reduced effectively as metakaolin replaced cement greater than 15%. This resulted in that the amounts of available portlandite decreased to less than 10% in cement paste. It is considered that the inhibition of ASR expansion by admixing of metakaolin was resulted by the combined processes that the formation of deleterious alkali-calcium-silicate gel was inhibited and the penetration of alkali solution into concrete was retarded due to the formation of denser, more homogeneous cement paste caused by pozzolanic effect. Higher early strength (7 days) than normal concrete was developed when the replacement ratios of metakaolin were greater than 15%. And also, late strength (28 days) was far higher than normal concrete for the all the replacement ratios of metakaolin. The development patterns of mechanical strength for metakaolin admixed concretes reflect the rapid pozzolanic reaction and hydration properties of metakaolin.

• Land and Housing Review
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• v.10 no.3
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• pp.23-32
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• 2019

Vacuum Insulation Panel(VIP) has the lowest thermal conductivity among present insulations. It is composed of envelope, core material and getter. Aluminum film is usually used as the envelope of VIP, and it is important component to decide the useful life of VIP. In this research, the thermophysical properties of incombustible fiber glass core VIP were investigated with the possibility of its architectural applications. The results of this research can be summarized as follows: 1) The thermal conductivity of 20mm-thick fiber glass core VIP is resulted as 0.00177W/m·K, which means that 20mm-thick VIP can meet all the reinforced insulation guideline and it can be used in any envelope of any region in Korea. 2) As a result of the test of incombustion and gas toxicity, fiber glass core VIP was suitable for incombustible material. 3) As the test result for the long term thermal conductivity, fiber glass core VIP was found out that it would keep above 10 times insulating performance than polystyrene foam and glass fiber. 4) To meet the thermal transmittance of 0.12W/㎡K, limited-combustible insulation of expanded polystyrene foam and phenolic foam should be used respectively as thick as above 280mm and 170mm, incombustible VIP can meet the same insulation level with 20mm thickness. 5) The price competitiveness of incombustible VIP to meet the thermal transmittance of 0.12W/㎡·K was about 1,500won/㎡ higher than that of phenolic foam.

• Journal of Korean Society of Forest Science
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• v.106 no.1
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• pp.70-76
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• 2017

Among the forest road pavement methods, the majority of current constructions utilize concrete pavements but it has disadvantages as follows: many cracked concrete pavements generated by the erosion of underlying soil layers, could not be used as forest roads in steep slope during winter, and cement contains hazardous chemicals (hexavalent chromium, etc.). In order to supplement the limitations of the use of concrete pavement, this study was conducted to investigate the operation process and cost, the strength and compaction of the experimental forest road pavement(85 m) utilizing eco-friendly solidification material at Goryeong-gun, Gyeongsangbuk-do. The work elements of experimental forest road paving were classified into: preparation, Roadbed excavation, Roadbed grading, subgrade compaction, form work, collection and selection of site soil, mixing site soil and eco-friendly solidification material, paving by eco-friendly solidification material, compaction by vibrating roller and curing. The result of economic analysis using construction cost shows that for concrete costs total to $38,681won/m^3$ while for the eco-friendly paving material it is $38,245won/m^3$. Thus the construction costs for concrete and the eco-friendly paving material are similar. And the results of the Schmidt Hammer test for strength analysis by curing period are 10.5-13.5 MPa for 7 days, 18.1-22.7 MPa for 14 days, and 20.8-23.0 MPa for 28 days.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.109-116
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• 2024

The Rapid Hardening Composite Mat (RHCM) is a product that improves the initial strength development speed of conventional Geosynthetic Cementitious Composite Mats (GCCM). It offers the advantage of quickly securing sufficient strength in railway slopes with insufficient formation level, and provides benefits such as preventing slope erosion and inhibiting vegetation growth. In this study, an analysis of the practical applicability of RHCM in railway settings was conducted through experimentation. The on-site applicability was assessed by categorizing it into fire resistance, durability, and stability, and conducting combustibility test, ground contact pressure test, and daily displacement analyses. In the case of South Korea, where a significant portion of the territory is composed of forested areas, the prevention of slope fires is imperative. To analyze the fire resistance of RHCM, combustibility tests were conducted as an essential measure. Durability was assessed through ground contact pressure tests to analyze the deformation and potential damage of RHCM caused by the inevitable use of small to medium-sized equipment on the construction surface. Furthermore, daily displacement analysis was conducted to evaluate the structural stability by comparing and analyzing the displacement and behavior occurring during the application of RHCM with railway slope maintenance criteria. As a result of the experiments, the RHCM was analyzed to meet the criteria for heat release rate and gas toxicity. Furthermore, the ground contact pressure was observed to be consistently above 50 kPa during the curing period of 4 to 24 hours under all conditions. Additionally, the daily displacement analyzed through field site experiments ranged from -1.7 mm to 1.01 mm, confirming compliance with the criteria.

• Korean Journal of Poultry Science
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• v.33 no.3
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• pp.233-238
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• 2006

In order to study the effect of feeding rare earth(RE) on growth of broiler chicks, feed conversion ratio, and probable harmfulness of feeding high levels of RE, two feeding trials with broiler chicks were conducted; one using a commercial broiler compound feed and the other using a self mixed feed excluding any growth stimulating feed additives. The the first trial used three hundred sixty of one day old Cobb broiler chicks for six levels of dietary supplementation of RE : 0, 100, 200, 400, 800 and 1,600 mg/kg. There were significant effect of RE stimulating broiler chick growth and improving feed conversion ratio, The dietary supplementation of RE at a level of 100 mg/kg was the best of all and increased body weight gain by 8.9% (p<0.05). Chicks fed RE at a level of 1,600 mg/kg grew as good as chicks fed feeds without RE and did not show my abnormalities. The second feeding trial was conducted in the same manner as the first trial using Ross broiler chicks and self-mixed experimental diets supplemented with RE at levels of 0, 50, 100 and 150 mg/kg. Differently from Results of the first trial, body weight gain and feed conversion ratio of were the best at the level of 50 mg/kg RE supplementation(p<0.05). In this trial all the birds fed RE showed significantly lower ratio of abdominal fat against live weight than those of the control group birds. Overall, it can be said that dietary supplementation of RE will improve broiler growth and feed conversion ratio and the proper dietary level would be $50\sim100mg/kg$. These results suggested that the proper level of RE for broiler chicks would be 50 to 100 mg/kg and its effectiveness is varied depending upon RE mixture. There appears abdominal fat of broiler chicks is decreased by feeding RE but further investigation is in need.

• Journal of the Korean Institute of Gas
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• v.17 no.6
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• pp.58-66
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• 2013

Among the risks which can be faced with fire, combustion toxicity is a significant influence on the survival. Fire toxicity researches have been limited generally on the lethal aspects. In this study, HF gas which can be generated from fire, and also found in general industrial site was used for analysis. Blood analysis and biochemistry analysis performed to find internal demage of experimental animals which were used for measuring average activity stopping time from Animal test(KS F2271: Gas hazard test). In addition, Using the malondialdehyde analysis, indicators of oxidative damage, we had quantitative analysis to target lymphocyte for measuring the oxidative damage caused by toxic substances.

• Korean Journal of Environmental Biology
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• v.35 no.1
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• pp.21-36
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• 2017

Phthalates, known as typical endocrine disruptors, are plasticizers used to soften plastics such as polyvinyl chloride (PVC). Because of their material properties, phthalates are used extensively in the production of toys, flooring, wood processing, detergents, and even cosmetics as lubricants and perfume solvents. Due to their endocrine disrupting effect and other adverse health effects published, recently, phthalates have been regulated in many countries. Besides, in an effort to replace phthalates, several chemical plasticizers such as trioctyltrimellitate (TOTM) and dioctylterephthalate (DIOP) have been used instead of the existing harmful phthalates, and novel alternatives are continuously being developed. Nonetheless, phthalates are still being detected in several plastic products, and the safety of alternatives that are considered safe is being questioned. In this review, we describe the adverse health effects of phthalates, their regulation and the current status of their alternatives.

• Resources Recycling
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• v.25 no.4
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• pp.23-31
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• 2016

It was found that there was no problem in recycling by-products (waste rock and tailings) from Yangyang iron mine themselves through matter conversion because they are not hazardous according to results of KSLT method. In case of using tailings as sub-materials of cement, it recommended the use of less than 3% tailings dosage not to exceed 0.6% of total alkali ($R_2O$) content based on standard quality of portland cement (KS L 5201). Non sintered eco-brick corresponding to class 1 quality of recycled clay brick (KS I 3013) can replace 15% of cement with tailings and 100% of general fine aggregate with waste rock from iron mine. As mentioned above, recycling the by-products (waste rock and tailings) as sub-materials of cement and non sintered eco-brick could gain both environmental and economic benefits, that is, reduction of scale and maintenance cost of tailing ponds, decrease of energy use and $CO_2$ emission.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.134-141
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• 2013

This paper explores a real-time system implementation to couple tightly StrapDown Inertial Navigation System(SDINS) and Global Positioning System(GPS) mounted on the aircraft. When implementing the SDINS/GPS coupled system in real-time processor, we have to deliberate SDINS's unique characteristics based on the ring laser gyro, and besides, lever-arm, measurements, and error compensation method. The novel modeling method is applied to system the misalignment error term of gyro to estimate the cumulative heading attitude errors while the aircraft banking to turn repeatedly. Captive Flight Test results show that the proposed modeling strategy has good performance.

• Korean Journal of Food Science and Technology
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• v.52 no.1
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• pp.109-112
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• 2020

To evaluate the safety of bacteriophages for application of sanitizer, endotoxin content and cell cytotoxicity of two Escherichia coli and four Staphylococcus aureus phages were determined. Endotoxin ratio was determined by the Limulus amebocyte lysate (LAL) assay as a test for representative biological endotoxin content. The average endotoxin average content of the 9 log PFU/mL lysate was 18.6 EU/mL and that of the 10 log PFU/mL lysate was 5.9 EU/mL, suggesting that the phage lysate was not suitable for clinical applications, but suitable for food pathogen control applications. To confirm the cell cytotoxicity of the phage lysates, MTT assay was performed using Raw 264.7 cells treated with 9 log PFU/mL phages. Results of the assay indicated that the phage lysates did not significantly decrease the cell viability (p>0.05). These results indicated that bacteriophages would be suitable as a food safety sanitizer.