• Wind and Structures
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• v.29 no.6
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• pp.471-488
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• 2019

Wind pressure is a critical argument for the wind-resistant design of structures. The attempt, however, to explore the wind pressure field on buildings still encounters challenges though a large body of researches utilizing wind tunnel tests and wind field simulations were carried out, due to the difficulty in logical treatments on the scale effect and the modeling error. The full-scale measurement has not yet received sufficient attention. By performing a field measurement, the present paper systematically addresses wind pressures on the rectangular attic of a double-tower building. The spatial and temporal correlations among wind speed and wind pressures at measured points are discussed. In order to better understand the wind pressure distribution on the attic facades and its relationship against the approaching flow, a full-scale CFD simulation on the similar rectangular attic is conducted as well. Comparative studies between wind pressure coefficients and those provided in wind-load codes are carried out. It is revealed that in the case of wind attack angle being zero, the wind pressure coefficient of the cross-wind facades exposes remarkable variations along both horizontal and vertical directions; while the wind pressure coefficient of the windward facade remains stable along horizontal direction but exposes remarkable variations along vertical direction. The pattern of wind pressure coefficients, however, is not properly described in the existing wind-load codes.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.495-510
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• 2015

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.734-741
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• 2008

At-rest and active earth pressure in plane strain condition have been applied to the design of cylindrical retaining walls. But many researchers have indicated that the earth pressure on the cylindrical retaining walls would be smaller than in plane strain condition due to wall deformation and stress relief. In this paper, the distribution of earth pressure acting on diaphragm wall of a shaft in dry sand was predicted by using the convergence confinement method and model test was performed to verify the estimated values. Test results showed that the earth pressure acting on the diaphragm wall of a shaft was expected to be 1.1~1.5 times larger than active earth pressure of plane strain condition and 0.7~0.9 times less than at-rest earth pressure.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.33-39
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• 2009

This study is intended to experiment performance of pressure relief device and to extend the effective ways to prevent cylinders of NGV from bursting when they are exposed to local fire intensively or when they are overcharged under ambient temperature at fueling stations in summer. In the results of thermal cycling experiments, all products of three companies met the requirements for gas leakage in the qualification criteria between $82^{\circ}C$ and $-40^{\circ}C$. But the o-rings of two companies' specimens among the three companies' specimens got damaged under the accelerated conditions between $135^{\circ}C$ and $-45^{\circ}C$. It took one minute and thirty nine seconds for a glass bulb type of a thermal sensitive type PRD to activate and it took two minutes and thirty one seconds for a fusible plug type of a thermal sensitive type PRD to activate. These results indicated that a glass bulb type of a thermal sensitive type PRD was one minute faster than a fusible plug type of a thermal sensitive type PRD. Under the accelerated condition $135^{\circ}C$, the activation pressure of a pressure sensitive type PRD burst at 32.1 MPa and, under the condition of qualification criteria, it burst from 30.7 MPa to 32.1 MPa.. As a result of the experiment for performance of pressure relief device, in the case of the thermal sensitive type PRD, a glass bulb type is more effective to flame than a fusible plug type. we confirmed that the rupture pressure of a pressure sensitive type PRD could not be affected by temperature and pressure cycling.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1226-1229
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• 2008

In this paper, we designed sandwich type pressure regulator for air pressure control system. As a result of research, we obtained several important conclusions. First, we decided theory of poppet valve and relief valve which are used in sandwich type pressure regulator, and then designed prototype of pressure regulator. Second, we organized circuit diagram of dual pressure regulator of air pressure control system.

• The KSFM Journal of Fluid Machinery
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• v.12 no.1
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• pp.16-21
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• 2009

In the last five years, 91 accidents from portable gas ranges and non-refillable metallic gas cartridges have occurred. The gas cylinder installed with a relief valve was developed to prevent an explosive accident from the gas cartridge. In this study it was carried out to evaluate the safety of a gas cylinder mounted with a relief valve which can prevent an explosion. Under the real using condition and the extreme condition the gas cylinder is heated with an electric heater. Simultaneously, the operating pressure is checked and the suitability of releasing flux is evaluated. And the possibility of fire or explosion was tested when the gas was released from the relief valve at the real using condition. Using a numerical simulation method, the diffusion of butane gas released from a relief valve was visualized.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.3
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• pp.171-176
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• 2016

Growing concerns about air pollution have led to increased demand for liquefied natural gas (LNG)-fuelled ships that have crankcases equipped with explosion relief valves to relieve excessive crankcase pressures and stop the flames emitted from the crankcase. The results of a computational fluid dynamics (CFD)-based feasibility analysis of the crankcase relief valve flame arrester design conducted using ANSYS CFX V14 showed that the inlet and outlet relief valve temperatures differed by $350-700^{\circ}C$. An explosion test was performed based on European standard EN14797 to evaluate the flame transmission and mechanical integrity of the valve. No flame transmission from the pressure vessel to the exterior was detected, and the mechanical integrity of the valve was confirmed. Thus, the relief valve components were found to be safe from the viewpoint of fracture.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1614-1616
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• 1998

Insulation performance of major components of prefabricated joint such as epoxy insulation unit and premolded rubber cone are guaranteed by material selection design and proper manufacturing. On the other hand insulation performance of the interfaces between the premolded rubber cone and the epoxy insulation unit and the cable insulation is maintained by keeping the premolded rubber cone to close contact with such insulation by spring. Electric characteristics of a interface depend on the contact pressure, but the required characteristics are assured so far as a proper contact pressure is maintained. In this report, the interfacial pressure by pressure sensors both in the early stage and after heating cycle were measured and the simulation by FEM program were presented. The comparison of these two results show that interfacial pressure could be controlled optimally by changing the spring length and lubricant state of the interface.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.35-43
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• 1999

The paper describes an approach for measuring delivery flow ripple generated by oil hydraulic axial piston pumps. In order to reduce pressure ripple which cause to undesirable noise. vibration and fatigue in hydraulic systems it is indispensible measure a delivery flow ripple from pumps. Since the flow ripple measurement of flow pumps is independent of the dynamic characteristics of the connected hydraulic circuit the measurement of flow ripple is most suitable for pump fluid-borne noise rating. The measurement of flow ripple with high frequencies from axial piston pumps is made by applying the remote instantaneous flow rate measurement method which is based on the dynamic characteristics between pressure and flow rate in hydraulic pipeline. The measured flow ripple waveforms are influenced by the configuration of V-shaped triangular relief groove in the valve plate. It can be seen that the appropriate relief groove in valve plate reduces the pressure and flow ripple amplitude and frequency spectrum for high harmonics.

• Journal of Power System Engineering
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• v.17 no.1
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• pp.77-84
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• 2013

The proportional pressure control valve that was used to relief valve has different dynamic characteristics on each case. Because this valve has different assembling or processing error and environmental condition. However, a customer who used the relief valve wants to have a steadily performance even if the dynamic characteristics of valve was changed. For this reason, the manufacturer try to make the robust controller that has simple structure. This paper concerns about the design of robust controller that didn't affected by plant parameter's changing. The control strategy is a model reference control that conducted by on line identification problem, gradient method and Lyapunov equation. This adaptvie control law's validity that this paper deal with was confirmed by an results of step response test or hysteresis test.