• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.39-48
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• 2017

In this study, combustion modeling of ZPP and $BKNO_3$ mainly used in the PMD industries has been performed. Saint Robert's law, energy conservation equation, and the Noble-Abel equation of the state have been used for governing equations. The results of pressure obtained from established combustion models and actual CBT have been compared. In the case of ZPP, the model has predicted a pressure curve similar to that of the experimental results, but $BKNO_3$ has showed that the maximum pressure of the model is greater than the experiment at small chamber volume. For these gaps, the probability of $BKNO_3$ unburning has been considered.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.428-432
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• 2010

A study on the forming characteristics of outer shell structure for thrust chamber nozzle extension has been performed. In order to identify anisotropy of cold rolled sheet metal, three types of tensile specimens according to the direction to the sheet rolling axis were prepared and tested, and Landford's values were obtained using the results and applied to structural analysis. Forming characteristics of the outer shell structure of the nozzle extension are investigated through manufacturing and forming of the full scale outer shell structures, and strain values obtained by the forming processes are compared to the numerical analysis results. The results obtained by this study will be utilized to design forming tools and processes for manufacturing other outer shell structures which have a bigger expansion area ratio.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.41-47
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• 2012

Every object over $O^{\circ}K$ emits radiant energy based on its own temperature. Uncooled thermal imaging system displays the detected incident radiant energy as an image by signal processing. Recently, the uncooled thermal imaging system is applied to various areas such as medical, industrial, and military applications. Also, several researches are in progress to find new applications of the uncooled thermal imaging system. In this paper, we present effective method for controlling TEC-less detector in the uncooled thermal imaging system and also present the efficient control scheme for maximizing the accuracy of temperature measurement. The proposed scheme is to apply TEC-less and temperature detection algorithm in Uncooled thermal imaging system. In results of tests performed by using the actual chamber, we acquired images of better quality than the former system and temperature measurement accuracy was improved to less than $1^{\circ}C$.

• Journal of the Korean Institute of Gas
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• v.17 no.4
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• pp.9-17
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• 2013

Butanethiol is known as a typical odorant with hydrogen sulfide, methyl mercaptan, methyl sulfide, but on the physical and chemical properties and biological hazard assessment, including inhalation toxicity data are very scarce. Butanethiol as a colorless transparent liquid, and has physic-chemical characteristics with flash point as $-23^{\circ}C$ and strong fire risk, boiling point $84-85^{\circ}C$, vapor pressure 80.71 mmHg ($25^{\circ}C$), freezing point $-140.14^{\circ}C$. From whole body exposure with SD rats, the $LC_{50}$ is above 2,500 ppm (9.22mg/L), and then it is classified as the acute toxic chemical (inhalation) category 4 according to the governmental notification No. 2012-14.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.711-717
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• 2017

Startability and harmful emissions are the main issues in diesel engine development under cold conditions. The characteristics of combustion with multiple injection were investigated under cold start conditions. For quantitative analysis, the in-chamber pressure profile was measured and combustion visualization using direct imaging was accomplished. With multiple injection, the peak in-chamber pressure and heat release rate were increased compared to single injection. In addition, the period of flame luminosity detection was shortened using multiple injection. Combustion by main injection was improved with an increase in heat released by pilot combustion when the pilot injection quantity was increased. Finally, an increase in injection pressure also showed the possibility of combustion improvement. On the other hand, an increase of in the pilot injection quantity and injection pressure can cause an increase in harmful emissions, such as HC and CO due to wall wetting. Therefore, more sensitive calibration will be needed when applying a multiple injection strategy under cold start conditions.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.43-50
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• 2022

In this paper, we designed and verified a Far-field measurement system for measuring the performance of an antenna operating in millimeter wave(W-band). For the antenna test, a measurement system should be selected according to the type of antenna, measurement items, measurement environment and period, etc. In the case of near-field measurement, it takes a lot of time because the number of measurement items increases when the antenna has multiple channels or various beams. Such an antenna can reduce the measurement time through Far-field measurement, and only necessary measurement items can be measured. Therefore, this study secured precise alignment of the far-field measurement system using a high-power laser and improved the measurement accuracy by applying a double amplifier system. The designed system was built in the anechoic chamber and verified by comparison with the verified Near-field measurement system.

• Composites Research
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• v.19 no.4
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• pp.23-30
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• 2006

In the development of a cryogenic propellant tank, the proper selection of adhesives to bond composite and metal liner is important for the safety of operation. In this study, 3 types of adhesives were tested for the ability to bond CFRP composites developed for cryogenic use and aluminum alloy (Al 6061-T6) for lining the tank using double-lap joint specimens. The double-lap joint specimens were tested inside an environmental chamber at room temperature and cryogenic temperature ($-150^{\circ}C$) respectively to compare the bond strength of each adhesive and fracture characteristics. The material properties with temperature of component materials of double-lap joints were measured. In addition, ABAQUS was used for the purpose of analyzing the experimental results.

• Tunnel and Underground Space
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• v.34 no.2
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• pp.154-168
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• 2024

The Tunnel Boring Machine (TBM) disc cutter is subjected to wear and damage during the rock excavation process, and the worn disc cutter should be replaced on time. The manual inspection by workers is generally required to determine the disc cutter replacement. In this case, the workers are exposed to dangerous environments, and the measurements are sometimes inaccurate. In this study, we developed a technology that measures the disc cutter wear in real time. From a series of laboratory tests, a magnetic sensor was selected as the wear sensor, and the real-time disc cutter measurement system was developed integrating wireless communication modules, power supply and data processing board. In addition, the measurement system was verified in actual TBM excavation circumstances. As a result, it was confirmed that the accuracy and stability of the system.

• Journal of Applied Biological Chemistry
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• v.55 no.1
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• pp.55-59
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• 2012

We designed a new rapid detection method for volatilized formaldehyde from wood. The process was installed with volatilizing and collecting parts in an incubator. For rapid sampling of formaldehyde from wood, we pulverized the wood to sawdust, and used 0.15-2.0 mm particles for the tests. The highest sampling rate (94.8%) was obtained at 40 mL/min flow rate and $100^{\circ}C$. Under the optimized condition, we could collect the volatilized formaldehyde with good recovery rate. The developed method was applied to the monitoring of the formaldehyde from wood, and the measured concentrations were 0.7-4.6 ${\mu}g/g$ from natural wood, 5.9-12.3 ${\mu}g/g$ from preserved wood, and 5.9-211.5 ${\mu}g/g$ from chemical adhesive processed wood. From the results, we identified natural wood sawdust and chemically processed wood (medium density fiberboard, high density fiberboard, particle board) by the formaldehyde contents except preserved wood.

• Journal of the Korean GEO-environmental Society
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• v.14 no.7
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• pp.19-29
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• 2013

Analysis via classical soil mechanics theory is either ineffective or inappropriate for fully describing stress distribution or failure conditions in cold regions, since mechanical properties of soils in cold regions are different from those reported in the classical soil mechanics theory. Therefore, collecting and analyzing technical data, and systematic and specialized research for cold regions are required for design and construction of the structure in cold regions. Freezing and thawing repeat in active layer of permafrost region, and a loading condition affecting the structure changes. Therefore, the reliable analysis of mechanical properties of frozen soils according to various conditions is prerequisite for design and construction of the structure in cold regions, since mechanical properties of frozen soils are sensitive to temperature condition, water content, grain size, relative density, and loading rate. In this research, the direct shear apparatus which operates at 30 degrees below zero and large-scaled low temperature chamber are used for evaluating shear strength characteristics of frozen soils. Weathered granite soil is used to analyzed the shear strength characteristics with varying freezing temperature condition, vertical confining pressure, relative density, and water content. This research shows that the shear strength of weathered granite soil is sensitively affected by various conditions such as freezing temperature conditions, normal stresses, relative densities, and water contents.