• Journal of the Korean Institute of Landscape Architecture
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• v.24 no.4
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• pp.123-131
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• 1997

Since the industrial revolution. the growth of cities has been especially apid and the rate of ulbanization has been high. This urban development is encroaching on the natural environment because the cities are developed with not only residential estates, industrial area and buildings but also with infrastructure. The surface area of the city is sealed ,with pavement whereas nature is disturbed and modified. The hydrological cycle in the city is inf1uenced by the change of land use I. e., from forest to agricultural land, talc draining of wetlands and above all the increase of built-up areas. The surface retention and interception of precipitation in the city is reduced. because the surface area is now smooth and solid. The characteristics of the hydrological cycle in the city are increased runoff, reduced evapotranspiration and infiltraction . We have too much faith in technology although it may cause more unforseen problems. We build more river banks and 'emulation dams and straighten rivers and streams in order to protect ourselves from disasters.. However. the results of hose developments are often higher$.$ water levels, the disturbance of aquatic ecosystems and the reduction of biodiversity. Therefore, we should examine problems from the hydrological cycle in cities and study a natural system as close cities to nature as possible. This paper shows the problems caused by the hydrological cycle in the city. The ecology-oriented method and design must be used in order to protect our environment from dicturbance.

• Journal of Educational Research in Mathematics
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• v.22 no.2
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• pp.261-275
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• 2012

There are some geometry achievement standards presented indistinctly in middle school mathematics curriculum revised in 2011. In this study, indistinctness of some geometric topics presented indistinctly such as symbol $\overline{AB}{\perp}\overline{CD}$ simple construction, properties of congruent plane figures, solid of revolution, determination condition of the triangle, justification, center of similarity, position of similarity, middle point connection theorem in triangle, Pythagorean theorem, properties of inscribed angle are discussed. The following three agenda is suggested as conclusions for the development of next middle school mathematics curriculum. First is a resolving unclarity of curriculum. Second is an issuing an authoritative commentary for mathematics curriculum. Third is a developing curriculum based on the accumulation of sufficient researches.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.1
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• pp.47-52
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• 1999

The influence of propeller revolution on measurement of fluctuating pressure is almost minimized in the KRISO cavitation tunnel and the measurement accuracy of fluctuating pressure acting on a flat plate due to a cavitating propeller is improved. The measurement data for Sydney Excess propeller is compared with the measurement results of other research institutes loading to the conclusion that KRISO data is so stable and reasonable. The fluctuating pressure data measured on a model ship and the prototype ship is compared with the data measured on the flat plate. The solid boundary factor, derived from a calculation based on a lifting surface theory, is applied to predict full scale pressure level from the experimental data on the flat plate, showing quite reasonable agreement with full scale data.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.401-404
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to different material characteristics, such as, thermal conductivity and flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld geometry and parameters. FE simulation was performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.200-204
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• 2005

The sirocco fan is used to get low noise, and it has been applied to a lot of industry field like the heat engine, the fluid instrument power plant, the food industry, environment industry etc... because there are not any problem even it is mixed with a any kind of liquid, gas, and solid. The flow characteristics in sirocco fan are investigated by PIV. The experiment using PIV measurement for Test section's flow characteristics acquired velocity distribution, .Condition : when sirocco fan in automobile air controller maximum 1450RPM, and a revolution is a variation (1)950RPM, (2)1100RPM, (3)1250RPM. The agreement a experiment shows the validity of this study and the results of this study would be useful to the engineers who design for the flow systems for heating, ventilation and air conditioning.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.266-270
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• 2007

Inertia welding is a solid-state welding process in which butt welds in materials are made in bar and in ring form at the joint face, and energy required for welding is obtained from a rotating flywheel. The stored energy is converted to frictional heat at the interface under axial load. The quality of the welded joint depends on many parameters, including axial force, initial revolution speed and energy, amount of upset, working time, and residual stresses in the joint. Inertia welding was conducted to make the large rotor shaft for low speed marine diesel engine, alloy steel for shaft of 140mm. Due to material characteristics, such as, thermal conductivity and high temperature flow stress, on the two sides of the weld interface, modeling is crucial in determining the optimal weld parameters. FE simulation is performed by the commercial code DEFORM-2D. A good agreement between the predicted and actual welded shape is observed. It is expected that modeling will significantly reduce the number of experimental trials needed to determine the weld parameters.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.61-65
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• 2020

Rheo-diecasting with stirring has been used in many material industries. As the 4th Industrial Revolution approaches the world, eco-friendly high-strength and light-weight materials become more important. Casting methods have been studied and used for aluminum-alloy automobile parts. This study carried out the effect analysis of the micro-structure and mechanical properties, such as yield/ultimate tensile strength, elongation, and hardness, of A356 using the 6-pole EMS (electro-magnetic stirring) casting process with a high electromagnetic force. As a result, the hardness and elongation of the A356 after T6 heat-treatment show a significant improvement, respectively, by 20% and 50%.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.150-150
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• 2016

Mankind is enjoying a great convenience of their life by the rapid growth of secondary industry since the Industrial Revolution and it is possible due to the invention of huge power such as engine. The automobile which plays the important role of industrial development and human movement is powered by the Engine Module, and especially Diesel engine is widely used because of mechanical durability and energy efficiency. The main work mechanism of the Diesel engine is composed of inhalation of the organic material (coal, oil, etc.), combustion, explosion and exhaust Cycle process then the carbon compound emissions during the last exhaust process are essential which is known as the major causes of air pollution issues in recent years. In particular, COx, called carbon oxide compound which is composed of a very small size of the particles from several ten to hundred nano meter and they exist as a suspension in the atmosphere. These Diesel particles can be accumulated at the respiratory organs and cause many serious diseases. In order to compensate for the weak point of such a Diesel Engine, the DPF(Diesel Particulate Filter) post-cleaning equipment has been used and it mainly consists of ceramic materials(SiC, Cordierite etc) because of the necessity for the engine system durability on the exposure of high temperature, high pressure and chemical harsh environmental. Ceramic Material filter, but it remains a lot of problems yet, such as limitations of collecting very small particles below micro size, high cost due to difficulties of manufacturing process and low fuel consumption efficiency due to back pressure increase by the small pore structure. This study is to test the possibility of new structure by direct infiltration of SiC Whisker on Carbon felt as the next generation filter and this new filter is expected to improve the above various problems of the Ceramic DPF currently in use and reduction of the cost simultaneously. In this experiment, non-catalytic VS CVD (Vapor-Solid Chemical Vaporized Deposition) system was adopted to keep high mechanical properties of SiC and MTS (Methyl-Trichloro-Silane) gas used as source and H2 gas used as dilute gas. From this, the suitable whisker growth for high performance filter was observed depending on each deposition conditions change (input gas ratio, temperature, mass flow rate etc.).

• Journal of Welding and Joining
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• v.26 no.2
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• pp.55-61
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• 2008

Various research to reduce weight of a car is achieving. This research is tendencious to manufacture solid piston rod of shock absorber as hollow piston rod using friction welding. This study deals with the friction welding of SM45C to SM45C-Pipe that is used in car shock absorber, The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied of friction weld, and so the results were as follows. 1. In tensile strength, the hole processing is better than non-hole processing. 2. When the friction time was 1.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 869MPa, which is 103% of SM45C's tensile strength and 91% of SM45C's Pipe. 3. When the friction time was 2.0seconds under the conditions, the maximum bending strength of the friction weld happened to be 1599MPa, which is 80% of SM45C's bending strength and 118% of SM45C's Pipe.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.42-50
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• 2008

Various researches to reduce weight of a vehicle are achieving. One of these researches is tendencious to manufacture the hollow piston rod using friction welding instead of solid one of the vehicle shock absorber. This study deals with the friction welding of SM45C to SM20C-pipe that is used normally in the vehicle shock absorber. The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests of friction weld were studied and so the results were as follows. When the friction time was l.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 837MPa, which is 113% of SM20C's tensile strength and 97% of SM45C's. The optimal welding conditions were n=2,000rpm, $P_1=55MPa$, $P_2=75MPa$, $t_1=1.5sec$, $t_2=2.0sec$ when the total upset length is 1.7mm.