• Journal of Environmental Science International
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• v.12 no.3
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• pp.337-344
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• 2003

The photodegradation of pyrene, chrysene and benzo［a］pyrene, that were similar in structure among poly-cyclic aromatic hydrocarbons (PAMs), were investigated in water irradiated with a low-pressure mercury lamp (wavelength of 253.7 nm and UV output of 1.35 ${\times}$ 10$\^$-3/J/s). The effects of several factors (t-BuOH, HCO$_3$$\^$-/ and pH) on photodegradation of above three PAHs were also examined. The photodegradation rates of PAHs decreased with increasing the concentration of t-BuOH, but decreased little with increasing the concentration of HCO$_3$$\^$-/ under the concentrations used in this study. The photodegradation rates of PAHs decreased with increasing pH, but their change were greater in case of pH increase from acid to neutral and were little in case of pH increase from neutral to base. The photodegradation rates of PAMs fitted a first-order kinetic model and their photodegradation rates decreased in the following sequences: pyrene>chrysene>benzo[a]pyrene among the PAHs used.

• Smart Structures and Systems
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• v.19 no.5
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• pp.473-485
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• 2017

Ratcheting behavior of $90^{\circ}$ elbow piping subject to internal pressure 20 MPa and reversed bending 20 kN was investigated using experimental method. The maximum ratcheting strain was found in the circumferential direction of intrados. Ratcheting strain at flanks was also very large. Moreover, the effect of temperature on ratcheting strain of $90^{\circ}$ elbow piping was studied through finite element analysis, and the results were compared with room condition ($25^{\circ}$). The results revealed that ratcheting strain of $90^{\circ}$ elbow piping increased with increasing temperature. Ratcheting boundary of $90^{\circ}$ elbow piping was determined by Chaboche model combined with C-TDF method. The results revealed that there was no relationship between the dimensionless form of ratcheting boundary and temperature.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.607-614
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• 1996

Yttrium(Y) coating was incorporated by ion-plating method either directly on the TiAl substrate or after pack aluminizing on TiAl to improve the oxidation resistance of TiAl alloy. After Y-coating, heat treatment at low oxygen partial pressure was carried out. Performance of various coating was evaluated by isothermal and cyclic oxidation tests. A simple Y-coating without pack aluminizing can give a detrimental effect on the. oxidation resistance of TiAl alloy, because it enhances formation of $TiO_2$. On the other hand, a composite coating of aluminide-yttrium has shown excellent oxidation resistance. A continuous protective $Al_2O_3$ scale is formed on the aluminized TiAl, and Y-coating improves $Al_2O_3$ scale adherence and substantially prevents depletion of Al in the aluminide-coating layer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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• pp.267-272
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• 1995

The paper describes an approach for measuring flow ripple generated by oil hydraulic axial piston pumps. Flow ripple has periodic waveforms due to the cyclic nature of a pump's operation, and interacts with the connected hydraulic systems such as pipes and components to produce a pressure ripple, also known as fluid-borne noise. It is indispensable to measure a flow ripple because increasing of vibration and noise caused by a flow ripple has become a point to be considered and has need of solving these problems. The measurement of flow ripple with high frequencies from oil hydraulic axial piston pumps is msde by using the remote instantaneous flow rate measurement method. As a result, the reverse flow through the relief groove in valve plate has an important effect upon a flow ripple generated by a pumps.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.790-795
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• 2002

The object of this research is limited to the reduction of compression process noise only among the main sources of compressor noise such as motor noise, compression process noise, and valve port flow noise. Thus the research is focused on the wave motion rather than the particle motion of sound wave travels. A muffler is a commonly used device to reduce the compression process noise, generated by the pressure pulsations caused by the cyclic compression process. In this research, the acoustic characteristics of the muffler are analyzed by using the normal gradient integral equation proposed by Wu and Wan. Moreover, a commercial code SYSNOISE developed by indirect variational boundary integral equation is also used to validate the results. For the noise reduction, the topology optimization technique using a genetic algorithm is used. The number, size and position of the muffler holes are considered as design variables. Compared with original design, the optimized design has very improved acoustic characteristics. Both numerical and experimental analyses are used to evaluate new design.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.3
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• pp.105-111
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• 2010

It is very important to select carefully backfill materials and build for the structural integrity of abutment in bridge. In general, backfill materials of unbound crushed stones (SB-1) are used to provide the safety of abutment structure and to reduce differential settlement around abutment that is significantly related with performance of road pavement under working conditions. In this study, to evaluate the compatibility of backfill materials at abutment and to develop the abutment design program, i) basic properties of subgrade soils in Korea, ii) evaluation of deformational characteristics of backfill materials from RC/TS tests, cyclic TX tests and Creep tests were accomplished.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.65-73
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• 2004

Fatigue crack growth from surface defects is one of the most important subjects for the evaluation and the assurance of safety in pressure vessels, piping systems, LPG/LNG fuel tank and other various structures. This paper attempts to analysis some practical or general problems such as the estimation of crack growth life to penetrate the plate thickness, based on fatigue crack growth a single surface flaw and the interaction of multiple flaws. An experiment on the coalescence of multiple undercuts was carried out under cyclic tension condition as a attempt to the analysis of multiple crack problems. It is noted that the fracture strength is characterized by the analogy to that in a single crack growth.

• International Journal of Railway
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• v.5 no.2
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• pp.71-76
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• 2012

Recently, axle load, operating speed and traffic density on railroads have had a tendency to increase and thereby cause additional pressure applied on used track. These operating conditions frequently result in service failure due to wear caused by wheel-rail contact and fatigue damage under cyclic loading. Among rail defects, the transverse crack, which has been the most dangerous type of fatigue damages, is developed from the subsurface crack near the rail running face and grows perpendicular to the rail surface. Therefore, it is necessary to investigate systematically the growth behavior of transverse crack for rail steel under mixed mode. In this study, the fatigue crack growth behavior of the transverse crack in rail steel was experimentally investigated under mixed-mode variable amplitude loadings.

• 연구논문집
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• s.30
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• pp.15-23
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• 2000

In this study, develop the thermal pump using water evaporation and condensation. Vapor from heating room moves up to pumping room and press the water of pumping room. Consequently water is pumped out to water tank. Then hot vapor direct contact with cold water in condensing room after pumping process. At this time, pressure of condensing room is down to-5kPa and suck in water of tank. This pump executes self ping and good durability because of no mechanical moving parts. Thermal pump is pumped cyclic so that, this pump is not used single. Therefore thermal pump of hot water boiler used to multi-stage for stable pumping rate. As the result of performance test, the developed thermal pump proves pumping action of water evaporation/condensation. And total volume flow rate is 500liter during one hour. If three thermal pump is installed parallel, this pump can use to the hot water boiler in the 300,000kcal/h class.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.344-347
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• 2007

For modeling the non-periodic and randomly scattered powder particles, the quasi-random multi-particle array is introduced. The multi-scale process simulation, which enables to formulate a regression model with a response surface method, is performed by employing a homogenization method. The size of ${Al_2}{O_3}$ particle, amplitude of cyclic compaction pressure, and friction coefficient are considered as optimal process parameters. The optimal conditions of process parameters providing the highest relative density are finally found by using the grid search method.