• Wind and Structures
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• v.14 no.3
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• pp.239-252
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• 2011

The wind-induced mean, background and resonant responses of Beijing National Stadium are investigated in this paper. Based on the concepts of potential and kinetic energies, the mode participation factors for the background and the resonant components are presented and the dominant modes are identified. The coupling effect between different modes of the resonant response and the coupling effect between the background and resonant responses are analyzed. The coupling effects between the background and resonant components and between different modes are found all negligible. The mean response is approximately analogous to the peak responses induced by the fluctuating wind. The background responses are significant in the fluctuating responses and it is much larger than the resonant responses at the measurement locations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.887-891
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• 2003

In this paper, two filters with center frequency of 19.58MHz were cascaded and its bandwidth characteristics were investigated with the variations of coupling capacitance for intermediate frequency (IF) bandpass filter application. The cascaded filter showed the higher stop region, reduction of spurious response and increase of selectivity. With the increase of coupling capacitance, insertion loss was increased but spurious response reduced. The cascaded filter with coupling capacitance of 15pF showed insertion loss of 5.643dB, 3dB bandwidth of 55.089kHz and 20dB bandwidth of 83.608kHz, respectively.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.9-14
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• 2002

Direct-conversion receiver(DCR) architecture has superior advantages in size, cost, and power over superheterodyne receiver architectures. However, the use of direct-conversion receiver architecture has been limited due to the direct-current offset noise. The ac coupling, which is used to overcome the direct-current offset noise, causes an inter-symbol interference(ISI), whose effects can be effectively mitigated using an equalizer. In this paper, the performance of a direct-conversion receiver with ac coupling in the presence of direct-current offset is analyzed via computer simulation. The simulation result shows that by using decision feedback equalizer with LMS(Least Mean Square) algorithm, signal-to-noise ratio loss of the direct-conversion receiver compared to the idea receiver can be reduced to less than 1㏈ for corner frequencies as large as 10% of the symbol rate.

• Journal of Power Electronics
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• v.11 no.3
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• pp.319-326
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• 2011

Nowadays numerous research projects are being conducted in the field of electric motors. Non-modeling of flexible connections such as couplings and the belt-pulley do not show some real behaviors. With an increase in the number of connections and drive factors, these Non-modeled modes become more important. The coupling of two electric motors, instead of one motor, in submarine propeller force is an obvious example which shows that Non-modeled vibration modes caused by flexible connections can disturb controller operation and make undesirable vibrations in the submarine body. In this paper a dynamic model of flexible connections and a completed dynamic model of two different coupled electric models is presented. A robust controller for the completed model is also amended so that the two controlling targets of a desired speed adjustment and an appropriate load division between the two motors with sufficient accuracy are achieved.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5745-5751
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• 2013

The purpose of this study was to evaluate the effect of the surface treatment of MMA and TEGDMA concentration, silane coupling agent on the shear bond strength of denture base resin and denture reliners. Denture base resin surface was treated with MMA and TEGDMA concentration, silane coupling agent. After denture reliners were injected bond strength was measured. The results of MMA and TEGDMA concentration on the shear bond strength of Vertex self curing resin showed that the value of MMA 95% and TEGDMA 5%, MMA 90% and TEGDMA 10%, MMA 80% and TEGDMA 20% groups were higher than that of other group(P<0.05). MMA and TEGDMA concentration on the shear bond strength of Kooliner resin showed that the value of MMA 95% and TEGDMA 5%, MMA 90% and TEGDMA 10% were higher than that of other group(P<0.05). Silane coupling agent on the shear bond strength of Vertex self curing resin and Kooliner showed that the value of MMA 95% and silane coupling agent 5% groups was higher than that of other group(P<0.05). Therefore, we could conclude that appropriate chemical surface treatments are supposed to affect the bond of denture base resin and denture reliners.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1049-1052
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• 2008

Coupling beams have been used in bearing wall system during last decades. Practically their sectional effects are fully considered in analysis stage to control lateral displacement because they have good contribution to the stiffness of bearing wall system. But the high resultant forces of coupling beam are not fully satisfied in design stage because coupling beams are restricted in sectional size. In this paper the performance of bearing wall system with coupling beam has been evaluated based on improved equivalent linearization procedure of FEMA 440. 15 storied building is selected for analysis. Variables for performance evaluation are natural period, degree of coupling and soil site. To evaluate performance, demand capacity spectrum is calculated based on KBC 2005. As a result, for the most of the cases the life safety limit of chord rotation of coupling beam is less than the performance point of system for soil site $S_D$. That means that the coupling beam can be severly damaged before the system reaches at performance point.

• Journal of the Korean Institute of Gas
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• v.21 no.1
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• pp.87-93
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• 2017

This study was conducted to analyze thermal effects for the structure of portable butane gas stoves in accordance with the introduction of safety standard to protect gas accidents that were caused by using oversized grills. The temperatures of oversized grill, cartridge and cover of cartridge coupling part were measured with stoves that heat sink was installed the inside of cover of cartridge coupling part and had different height of tripods. The trend of measured temperatures affected by thermal effects of grill and flame was analyzed. The condition of using portable butane gas stove safely is that the distance between grill and cover of cartridge coupling part should be about 28 mm and over. In contrast, when the distance between grill and cover of cartridge coupling part would be shorter, thermal effects of not only grill but also flame could affect the cartridge directly. In this case, the danger that could cause gas accident would be higher. When heat sink was installed the inside of cover of cartridge coupling part, it was effective on reducing of thermal effects. However, it still had the danger of explosive gas accident of cartridge due to overheating.

• Explosives and Blasting
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• v.35 no.4
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• pp.19-26
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• 2017

The most widely used method for determining the blast effects of explosives is the Trauzl lead block test. This test is used to measure the explosive power (strength) of a substance by determining volume increase, which is produced by the detonation of a test explosive charged in the cavity of a lead block with defined quantity and size. In this paper, Trazul lead block test and AUTODYN numerical analysis were conducted to evaluate the coupling medium effect of blast hole. The effects of coupling materials can be expressed as the expansion of the cavity in a standard lead block through explosion of the explosives. The tests were conducted with emulsion explosives. The coupling mediums used as the filling material around a explosive charge were air, sand, water and gelatine. Results of test and numerical analysis showed that expansion of lead block were much more affected by water&gel than by sand and air. The water and gel showed similar results. As expected, the transmitted pressure and dynamic strain was higher in water and gelatine coupled blast hole than in air and sand.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.2
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• pp.87-93
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• 2020

Seismic responses due to the dynamic coupling between a primary structure and secondary system connected to a structure are analyzed in this study. The seismic responses are compared based on dynamic coupling criteria and according to the error level in the natural frequency, with the recent criteria being reliant on the error level in the spectral displacement response. The acceleration responses and relative displacement responses of a primary structure and a secondary system for a coupled model and two different decoupled models of two degrees-of-freedom system are calculated by means of the time integration method. Errors in seismic responses of the uncoupled models are reduced with the recent criteria. As the natural frequency of the secondary system increases, error in the natural frequency decreases, but seismic responses of uncoupled models can be underestimated compared to that of coupled model. Results in this paper can help determine dynamic coupling and predict uncoupled models' response conservatism.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.221-226
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• 2005

In this paper, a dynamic model for the rotor shaft-coupling-blade system is developed. The blades are attached to a disk and driven by an electric motor shaft which is flexible in torsion. We assumed that the shaft torsional flexibility is lumped in the flexible coupling which is usually adopted in rotor systems. The Lagrangian approach with the small deformation theory for both blade-bending and shaft-torsional deformations is employed for developing the equation of the motion. The assumed modes method is used for estimating the blade transverse deflection. The numerical results highlight the effects of both structural damping of the system and the torsional stiffness of the flexible coupling to the dynamic response of the blade. The results showed strong coupling between the blade bending and shaft torsional vibrations in the form of inertial nonlinearif, stiffness hardening and softening.