• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.168-173
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• 1998

A numerical analysis of axisymetric backward facing step main nozzle flow in air jet loom has been accomplished. To obtain basic design data for an optimum main nozzle for an air-jet loom and to predict the transonic/supersonic flow, a characteristic based upwind flux difference splitting compressible Navier-Stokes method has been used. The wall static pressure of the main nozzle and the flow velocity changes in the nozzle tube were analyzed by changing air tank pressures and acceleration tube lengths. The flow inside the nozzle experiences double choking one at the needle tip and the other at the acceleration tube exit at tank pressures over $4kg_f/cm^2$. The tank pressure $P_t$ leading to the critical condition depends on the acceleration tube length; i.e, $P_t$ is higher for longer acceleration tubes. The $P_t$ value required to bring the acceleration tube exit to the critical condition is nearly constant regardless of acceleration tube length. The round needle tip shape might lead to less total pressure loss when compared with step shape.

• Journal of the Korean Solar Energy Society
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• v.37 no.5
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• pp.65-75
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• 2017

In this study, the change of heat loss due to the degree of deterioration of the XPS insulation in KEPCO's office buildings is analyzed. The acceleration aging test of the XPS insulation was carried out according to the test method A of KS M ISO 11561: 2009. The performance of the insulation was analyzed by applying it to the three - dimensional steady state heat transfer analysis program. The acceleration aging test of the XPS insulation, show that the thermal resistance performance decreased by 1.44% at the A regional headquarters, 0.85% at the B regional headquarters, 6.41% at the C branch office, 7.76% at the D regional headquarters, 8.51% at the E branch office, and by 8.54% at the F branch office respectively. Using simulation, we determined that the thermal resistance value of E branch office decreased by 8.04%, while its heat loss increased by 8.52%. At A regional headquarters, the thermal resistance decreased by 1.38%, and the heat loss increased by 1.51%. At D regional headquarters, these value are 6.82% and 7.17%, respectively.

• Structural Engineering and Mechanics
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• v.82 no.6
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• pp.735-745
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• 2022

The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

• Land and Housing Review
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• v.5 no.2
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• pp.115-120
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• 2014

Site coefficient and amplification factor of current domestic Seismic Design Code (KBC-2009) have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. Accordingly, in this study dynamic centrifugal test and analysis for pile foundation into clay were achieved. and the response spectrums of free surface and basement were compared with each other. Within the period 1sec., the measured spectral acceleration of free surface and basement was bigger than the design spectral acceleration of SC and SD site. However the measured spectral acceleration of free surface and basement for the period over 1.5sec. was smaller than the design spectral acceleration of SC site. There was no severe difference of spectral acceleration according to the upper structure, embedded depth of foundation and free surface conditions. Consequently, normal domestic apartment housing for the period range over 1.5sec. could be design more economically applying these test result.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.236-242
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• 2014

Since permanent magnet coupling transfers power by magnetic force without contact, it has little shock, vibration, noise. In case of overload, it protects a pump or a motor which is relatively important by slipping internally. In this study, failure analysis and test evaluation on the permanent magnet coupling have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement plan has been presented. Finally, reliability improvement is established by analysis of the test results of before and after acceleration test.

• Journal of Applied Reliability
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• v.16 no.4
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• pp.263-271
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• 2016

Purpose: A slurry pump for flue gas desulfurization system performs a role that discharges the slurry of a plaster shape in a thermal power plant. Since a slurry pump transfers the slurry by the centrifugal force, it has the friction wear in the impeller and liner because of the slurry. Methods: In this study, failure analysis and test evaluation on the slurry pump have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement design has been presented. Results: Reliability improvement is established by analysis of the test results of before and after acceleration test. Conclusion: This study can be provided to improve the product reliability through failure analysis of a slurry pump.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.170-171
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• 2014

The buildings constructed with steel structure is coated with certified fire resistive material to resist from fire. Coating materials lose their initial performances as time passes, so they need some maintenance. This study is covers standardization of the methods for assessing the durability of SFRM. In Korea, more than 90 percent of SFRM are used indoors. So This study is to decide proper test method through investigation and examination of effect factor to performance of fire-resistant structure and applicable test method.

• Journal of The Korean Astronomical Society
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• v.48 no.1
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• pp.9-20
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• 2015

We study the evolution of the energy spectrum of cosmic-ray electrons accelerated at spherically expanding shocks with low Mach numbers and the ensuing spectral signatures imprinted in radio synchrotron emission. Time-dependent simulations of diffusive shock acceleration (DSA) of electrons in the test-particle limit have been performed for spherical shocks with parameters relevant for typical shocks in the intracluster medium. The electron and radiation spectra at the shock location can be described properly by the test-particle DSA predictions with instantaneous shock parameters. However, the volume integrated spectra of both electrons and radiation deviate significantly from the test-particle power-laws, because the shock compression ratio and the flux of injected electrons at the shock gradually decrease as the shock slows down in time. So one needs to be cautious about interpreting observed radio spectra of evolving shocks based on simple DSA models in the test-particle regime.

• International Journal of Aerospace System Engineering
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• v.4 no.2
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• pp.5-9
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• 2017

In a pressurized fuel supply system of aircraft, a flow passage opening device is required to keep fuel continuously transferred from one tank to the other. The device utilizes balancing weights in order to follow up an acceleration at special conditions such as negative g. It is very difficult to test the device in a real high-speed and high-altitude test since severe test conditions and expensive supports are needed. Therefore, this paper deals with performance analysis of a flow passage opening device through low speed aircraft captive flight tests (CFT) including roll and negative-g maneuvers. It is shown that balancing weights in the device can open the passage in accordance with fuel position.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.109-110
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• 2014

The buildings constructed with steel structure is coated with certified fire resistive material to resist from fire. Coating materials lose their initial performances as time passes, so they need some maintenance. This study is covers standardization of the methods for assessing the durability of SFRM. In Korea, more than 90 percent of SFRM are used indoors. So This study is to decide proper test method through investigation and examination of effect factor to performance of fire-resistant structure and applicable test method.