• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.25-31
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• 2009

In this study, the problem of existing soil pavement is a long-term durability lack and crack occurrence. It complements in order to develop the environmental soil pavement material which composites readily blended mineral binder of liquid and decomposed granite soils. It was estimated optimal mixture proportion for unconfined compressive strength, permeability, $Cr^{6+}$detection test, SEM test with age, freezing and thawing test. It resulted mixture proportion of powder types mineral binder for rates of cement : fly ash : plaster was optimal rates of 50 : 33 : 7, and $Cr^{6+}$detection test as a result was a slight production. SEM test with 3days as a result was made Ettringite. It was found that this material was early development of early-strength for chemical. This study indicated that it will execute field appliciability Evaluation test, examination of soil pavement method with decomposed granite soils and mineral binder.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.1
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• pp.23-31
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• 2003

Since the mid of 1990, permanent shotcrete tunnel linings such as Single-shell and NMT have been constructed in many countries for reducing the construction time and lowing construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of permanent shotcrete linings, high performance shotcrete having high strength, high durability and better pumpability has to be developed in advance as an integral component. This paper presents the idea and first experimental attempts to increase early strength and bond strength of wet-mixed Steel Fiber Reinforced Shotcrete (SFRS) in spring water condition. In order to increase early behavior of SFRS, a new approach using high-early strength cement with alkali-free liquid accelerator has been investigated. From the test results, wet-mix SFRS with high-early strength cement and alkali-free accelerator exhibited excellent early compressive strength improvement compared to the ordinary portland cement and good bond strength even under spring water condition.

• Journal of the Korean GEO-environmental Society
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• v.2 no.4
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• pp.73-81
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• 2001

Soil cement has been the typical material for the pavement and soft ground improvement. It has not been used up to date because that quality control is not easy and durability is not long enough for practical application. Since environmental influence is important, the application of high strength soil cement pavement has been increased for pedestrian roads of the garden, golf courses and sidewalks recently. In this study, the reference table was suggested for mixing design with appling statistical experimental technique to reference table. The reference table showed the relationship among improved strength, Soilcrete stabilizer, fine sand ratio and superplasticizer agent. The objective soil used in this study was the soft marine clay that is widely found in Korea, the compressive strength range of improved soil was between $50{\sim}150kg/cm^2$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.525-530
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• 2006

Recently companies which do not use the heavy metals such as lead, chrome, mercury to the electronic goods and alternate the materials environment-friendly are increasing. In advanced country, lead-free solder without lead is developed and soldering process almost disappeared. The lead-free solder is environment-friendly but is expensive and lack of tack and durability than lead, the improvement is necessary. To solve this problem, the welding process that uses TIG welding and the welding technology between different kind metals for lead-in wire of room lamp and base department was developed. To do this, previous room lamp manufacturing process was analysed and which process can be alternate was proposed. And the test for selection of optimal value of TIG welding parameter was done. Finally the lamp aging test and earthquake resistant test was done to check the reliability of welded room lamp.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.758-764
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• 2019

The chassis of the Korean light tactical vehicle adopts a frame-on-body structure that uses lightweight design technology in terms of equipment operating characteristics. Military vehicles are operated in much harsher conditions compared to civilian vehicles, including mountainous terrain, especially steep slopes. Due to this characteristic, frame-welded cracks were found on some military vehicles. Therefore, in this paper, road damage analysis was conducted by identifying various roads including the military unit's road. The result confirmed that the operating environment of some military units' tactical road was much harsher than the endurance road test condition. A solution was derived through defect analysis, design review, and actual vehicle driving test. This study can be used as a reference by suggesting the development direction for the durability test of a new vehicle.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.661-664
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• 2008

The structure which is located in special surroundings like ocean-environment is physically and chemically eroded by seawater or salt damage, and then concrete-structure becomes deteriorated by iron corrosion and swelling pressure which leads to remarkably decline durability due to cracks and exploitation. As a measure against salt damage, it is actively being examined to use the blended cement that controls salt damage and fix chloride in the process of hydration. In this study, therefore, to examine the property of marine concrete added admixture, marine concrete is manufactured by adding high-strength admixture(omega2000) by 0, 5, 10, and 15% to low heat-blended cement. Then it shows that the compressive strength of manufactured marine cement tends to increase and chloride penetration resistance improves.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.395-402
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• 2010

Baffle injectors are protruded into the combustion chamber and form an anti-pulsating baffle to prevent high-frequency combustion instabilities in transverse modes. Being exposed to a high heat-flux environment, the baffle injector has self-cooling passages through which kerosene is convected and heated. The baffle injector with 20 spiral cooling channels has been developed and successfully applied to 30 $ton_f$-class combustors without any performance loss due to an additional cooling. In this work, numerical analysis of conjugate heat transfer in baffle injectors with various cooling channel designs has been performed in order to reduce the fabrication cost which would be considerably increased for the 75 $ton_f$-class combustor. Prior to the application to a full-scale combustor, the thermal durability of the modified design has been verified through the subscale hot-firing tests.

• Journal of the Korea Concrete Institute
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• v.28 no.4
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• pp.445-454
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• 2016

With the increase of decrepit facilities, construction waste increased to a certain level and now the increase is more or less stabilized. Yet construction waste still constitutes the largest portion of the overall wastes. Also, it is inevitable to spend a huge amount of the national budget due to the aggravating shortage of aggregate caused by prohibition on collection of natural aggregates as well as due to the damage to the land and environment caused by development of the sources of aggregates. As a countermeasure to the situation, the Ministry of Land, Infrastructure and Transport promulgated the quality standard for recycled aggregate to manage the usage of recycled aggregate according to its quality. But use of recycled aggregate for the purpose of high added value still remains nominal. Therefore, this research aims to study the applicability of recycled aggregate concrete as structural concrete by evaluating the quality improvement effects and the performance of the recycled aggregate concrete including recycled fine aggregate and recycled coarse aggregate that have undergone carbonation for 4 days and 14 days respectively in the condition of 60% RH, 20% $CO_2$ and $20^{\circ}C$ temperature, suggested for carbonation modifying from the advance research. The result shows carbonation modify contributed to quality improvement with 0.91% decrease in absorption rate for recycled fine aggregate and 0.7% decrease in absorption rate for recycled coarse aggregate. The physical properties and durability of the recycled aggregate made of aggregate modified by carbonation showed results similar to general concrete, which confirmed the possibility of applying the recycled aggregate made of recycled aggregate modified by carbonation to structural concrete.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.12
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• pp.1848-1856
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• 2008

In order to enhance the functionality of a cotton fabric actually used as the clothing material for patients, the fabrics are treated with chitosan/nanosilver mixed solution. The nanosilver has excellent biocompatibility, not causing an environmental pollution as a natural polymer, provides expectation of an additional performance, does not harm human beings, and shows a strong antibacterial activity even in a small amount, and supplements chitosan, which is disadvantaged if used alone for fabric treatment. This study evaluates functional improvement of the clothing material for patients and observes through hygienic characteristics which are the most important function. In antibacterial activity of the fabrics treated with chitosan/nanosilver mixed solution against Staphylococcus aureus, higher ratio of chitosan was observed to achieve better antibacterial activity. In antibacterial activity against Klebsiella pneumoniae, higher ratio of nanosilver was observed to achieve better activity. Regarding laundry durability of antibacterial activity after repeated laundering, activity against Staphylococcus aureus was little reduced, but was greatly lowered against Klebsiella pneumoniae. Deodorization activity was excellent as the mixed ratio of chitosan was increased, and air permeability, moisture permeability and moisture regain were reduced as the mixed ratio of nanosilver was increased.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.34-39
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• 2015

This study confirmed the characteristics of hydrogen production according to electrode materials by producing non-diaphragm alkaline water electroanalyzer that can be controlled at medium temperature to produce hydrogen. As a result of the electrochemical characteristics by electrode material ($IrO_2/Ti$, $RuO_2/Ti$, Ti), the highest efficiency was found in $RuO_2/Ti$, as a result of hydrogen production experiment by electrolyte concentration, electrolyte concentration has a tendency to be proportional to hydrogen production and the condition of 30% KOH showed the highest hydrogen production as $118.9m^3/m^3/day$. In the experiment that confirmed hydrogen production according to electrode materials, in case of combination of anode ($IrO^2/Ti$) and cathode ($RuO^2/Ti$), it was $157.55m^3/m^3/day$ that showed a higher hydrogen production by around 6.97% than that of $IrO^2/Ti$ and cathode. It is presumed that the improvement of electrochemical activation of DSA electrode increases hydrogen production and influences the improvement of durability compared to the former electrode so that it enables stable alkaline water electrolysis.