• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.566-569
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• 2004

This study is to trace the change of stream shape using the past series of aerial photographs, and to compare the land use changes of riparian area along the stream. For the Gyeongan national stream, aerial photographs of 1966, 1981 and 2000 were selected and ortho photographs were made with interior orientation and exterior orientation, respectively. As apparent changes of the stream, the consolidated reaches of stream with levee construction were straightened and their stream widths were widened. Especially the stream width of inlet part of Paldang lake was widened almost twice because of the rise of water level by dam construction in 1974. The land use maps (1966, 1981,2000) of riparian areas were also made, respectively and classified into 6 categories (water, forest, agricultural land, urban area, road, sandbar) by digitizing. The area of forest and agricultural land decreased and urban area increased as the stream maintenance was performed.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.2
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• pp.15-21
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• 2005

This study is to trace the change of stream shape using the past series of aerial photographs, and to compare the land use changes of riparian area along the stream. For the Gyeongan national stream, aerial photographs of 1966, 1981 and 2000 were selected and ortho-photographs were made with interior orientation and exterior orientation, respectively. Apparent changes of the stream were found that the consolidated reaches of stream by levee construction became straight together with widening of their stream widths. Especially the stream width of inlet part of Paldang lake widened almost twice because of the rise of water level by dam construction in 1974. The land use of riparian areas of three selected years were classified into six categories (water, forest, agricultural land, urban area, road, sandbar) by digitizing method. The forest and agricultural lands decreased and urban area increased as the stream maintenance had been performed.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.04a
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• pp.55-55
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• 2000

Cylinder machine usually gives more fiber orientation than fourdrinier and has limitation in machine speed because of fiber wash-off caused by centrifugal force in case of adding machine speed. This study aimed at improvement of paper formation and higher productivity by setting up an apron in vat inlet and by adjustment of mould water head. As results, there were improvement of formation and increase of machine speed, which ultimately improve productivity. Setting up an apron successfully decreased fiber wash-off. Fiber orientation and two-sideness of ash distribution became less severe. These results could lead to better dimension stabilities in the CD through mitigation of fiber orientation and also could result in less curl from two-sideness of paper. The proper adjustment of water head inside the cylinder mould proved to be important factor not only in paper formation but also in decreasing paper two-sideness.

• Journal of Power System Engineering
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• v.14 no.3
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• pp.19-24
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• 2010

The purpose of this study is to develop a snow melting system using the pulsating heat pipe(PHP). The experimental apparatus is consisted of a PHP, a concrete structure, a constant water thermostatic bath and a flowmeter. The experiment was performed at the outdoor air temperature of $-8^{\circ}C$ and inlet temperature of hot water of $75^{\circ}C$. PHP is the closed and non-loop type heat exchanger which is charging R-410A as an operating fluid. As experimental results, the temperature profile of vertical and horizontal orientation of concrete structure was measured with operating time. The heat flux of the snow melting was required more than 300 $W/m^2$. We confirmed that the snow melting system using the PHP was useful for anti-freezing road.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.761-770
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• 1996

Silicon carbide (SiC) films were deposited by low pressure chemical vapor deposition (LPCVD) using MTS (CH3SICl3) in a hydrogen atmosphere onto graphite substrates. Depletion effects of reactants which usually occur in the hot wall horizaontal reactor were increased with deposition temperature and pressure. Below 50 torr of total pressure (111) plane was preferenctially grown irrespectrive of deposition temperature and deposition site. Over 50 torr of total pressure however (220) plane was preferentially deposited under 130$0^{\circ}C$ and at inlet site. The surface morphologies of SiC films were uniform at all deposition sites under low pressure but greatly changed with pressure. It shows that a facet structure which was formed above 125$0^{\circ}C$ played an important role in the changed of preferred orientation and surface roughness.

• Journal of Korea Water Resources Association
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• v.38 no.5 s.154
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• pp.379-390
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• 2005

This study is to trace the change of stream shape using the past series of aortal photographs and topographic maps, and to compare the land use changes of inland along the stream. For the Gyeongan first & second class of local stream, aerial photographs of 1966, 1981 and 2000 were selected and ortho photographs were made with interior orientation and exterior orientation, respectively. In addition, topographic maps of 1914 - 1915 were used to compare with stream of 1966, 1981 and 2000. As apparent changes of the stream, the consolidated reaches of stream with levee construction were straightened and their stream width widened. Especially the stream width of inlet part of Paldang lake was widened almost twice because of the rise of water level by dam construction in 1974. The land use maps (1966, 1981, 2000) of riparian areas were also made, respectively and classified into 6 categories (water, forest, agricultural land, urban area, road, sandbar) by digitizing, The main changes of land use were agricultural land, urban area, road and sandbar.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.250-258
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• 2014

Due to recent industrial growth and development, there has been a high demand for light and highly durable materials. Therefore, a variety of new materials has been developed. These new materials include carbon fiber reinforced plastic (CFRP or CRP), which is a wear-, fatigue-, heat-, and corrosion-resistant material. Because of its advantageous properties, CFRP is widely used in diverse fields including sporting goods, electronic parts, and medical supplies, as well as aerospace, automobile, and ship materials. However, this new material has several problems, such as delamination around the inlet and outlet holes at drilling, fiber separation, and tearing on the drilled surface. Moreover, drill chips having a fine particulate shape are harmful to the work environment and engineers' health. In fact, they deeply penetrate into machine tools, causing the reduction of lifespan and performance degradation. In this study, CFRP woven and unidirectional prepregs were formed at $45^{\circ}$ and $90^{\circ}$, respectively, in terms of orientation angle. Using a high-speed steel drill and a TiAIN-coated drill, the two materials were tested in three categories: cutting force with respect to RPM and feed speed; shape changes around the input and outlet holes; and the shape of drill chips.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.5
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• pp.201-211
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• 2019

Low carbon steel (S20C steel) and SPCC steel sheet have been austenitic nitrided at $700^{\circ}C$ in a closed pit type furnace by changing the flow rate of ammonia gas and heat treating time. When the flow rate of ammonia gas was low, the concentration of residual ammonia appeared low and the hardness value of transformed surface layer was high. The depth of the surface layer, however, was shallow. With increasing the concentration of residual ammonia by raising up the ammonia gas flow, both the depth of the surface layer and the pore depth increased, while the maximum hardness of the surface layer decreased. By introducing a large amount of ammonia gas in a short time, a deep surface layer with minimal pores on the outermost surface was obtained. In this experiment, while maintaining 10~12% of residual ammonia, the flow rate of inlet ammonia gas, 7 liter/min, was introduced at $700^{\circ}C$ for 1 hour. In this condition, the thickness of the surface layer without pores appeared about $60{\mu}m$ in S20C steel and $30{\mu}m$ in SPCC steel plate. Injecting additional methane gas (carburizing gas) to this condition played a deteriorating effect due to promoting the formation of vertical pores in the surface layer. For $1^{st}$ transformed surface layer for S20C steel, maintaining 10~12% residual ammonia condition via austenitic nitriding process resulted in ${\varepsilon}$ phase with relatively high nitrogen concentration (just below 4.23 wt.%N) among the mixed phases of ${\varepsilon}+{\gamma}$. The ${\varepsilon}$ phase was formed a specific orientation perpendicular to the surface. For $2^{nd}$ transformed layer for S20C steel, ${\gamma}$ phase was rather dominant (just above 2.63 wt.%N). For SPCC steel sheet, there appeared three phases, ${\gamma}$, ${\alpha}(M)$ and weak ${\varepsilon}$ phase. The nitrogen concentration would be approximately 2.6 wt.% in these phases condition.