• Proceedings of the Computational Structural Engineering Institute Conference
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• 1995.04a
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• pp.114-121
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• 1995

Problems of noise and vibration induced by subway operation became one of the major factor when new subway 1 me is under consideration. One of the most economic method in reducing the noise and vibration is the increasement of the tunnel mass. . Vibration of the massive tunnel structure has been measured induced by subway operation. STEDEF system which was adopted by Seoul Metropolitan Subway Bureau has been proved that more than 99% of the vibration has been decreased at the bottom of the railway track. Most of the vibration measured inside and outside of the tunnel showed that their peak frequency is around SOHz or 100Hz. The propagation characteristics of vibration in massive tunnel , wave propagate in three directions. Overall frequency in the range of 0 to 125H2 horizontal transmission usually increase, while vertical transmission decreases about 50% in the range of 0 to 25Hz and 90Hz to 125Hz regardless of modal shape.

• Journal of Korea Multimedia Society
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• v.21 no.5
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• pp.592-598
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• 2018

In wireless sensor networks where there is no centralized base station, each node has limited transmission range and the multi-hop routing for transmitting data to the destination is the one of the important technical issues. In particular, the wireless sensor network is not powered by external power source but operates by its own battery, so it is required to maximize the network life through efficient use of energy. To balance the power consumption, the residual power based adaptive power control is required in routing protocol. In this paper, we propose a routing protocol that prolongs the network lifetime by balancing the power consumption among the nodes by controlling the transmit power according to the residual power. We evaluate the proposed routing protocol using extensive simulation, and the results show that the proposed routing scheme can balance the power consumption and prolong network lifetime.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.39-44
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• 2005

A broadband DC to 40 GHz 5-bit MMIC digital attenuator has been developed. The ultra broadband attenuator has been achieved by newly inserted the transmission lines in conventional Switched-T attenuator and the optimization of the transmission line parameters. Momentum was employed in design for an accurate performance prediction at high frequencies and Monte Carlo analysis was applied to verify performance stability against the MMIC process variation. The attenuator has been fabricated with 0.15 $\mu$m GaAs pHEMT process. This attenuator has 1 dB resolution and 23 dB dynamic range. High attenuation accuracy has been achieved over all attenuation range and full 40 GHz bandwidth with the reference state insertion loss of less than 6 dB at 20 GHz. The input and output return losses of the attenuator are better than 14 dB over all attenuation states and frequencies.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.232-242
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• 1997

In this paper, we have designed an active radio frequency identification system solving the problems of moving transponder which is identification range expanding and low battery consuming of transponder. Developed radio frequency identification system is a bidirectional data transmission system which is composed of decoder data transmission of 120 kHz and transponder data carrier of 60 kHz which is a subharmonic frequency response with ASK modulation. The experimental results, designed system operating at 9600 bps, show good performances with detecting the 40 km/h moving transponder up to the range of 2 and 15 ${mu}A$ low consuming current.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1727-1732
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• 2011

In order to realize a high performance(low loss, high isolation) microwave power divider/combiner, we have designed the power combiner/divider precisely in accordance with the different hight of central part. In the case of the high central part of the hight of $h_r$=10.2, a compensating part of the conical line is inserted in the conical conversion transmission line, and in the case of low central part of the hight of $h_r$=5.0, the conical conversion transmission line is remodeled into the 2-stage bend structure. In both case, the reflection characteristics are improved to 30dB over the operating frequency range of 5GHz bandwidth. A resistance is inserted between the peripheral ports so as to try to improve the isolation characteristics of the device. For the 16-divider/combiner, the isolation characteristics are improved to 10dB over the operating frequency range of 5GHz bandwidth.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.209-217
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• 2020

The purpose of this study was to compare the model-predicted and experimentally measured target strength (TS) of golden cuttlefish Sepia esculenta cuttlebones. Ultrasonic signals used to estimate frequency-dependent TS and the speed of sound in cuttlebones were measured by pulse-echo and through-transmission techniques, using a chirp sonar system and an ultrasonic pulser/receiver system under controlled laboratory conditions. The model appeared to slightly underestimate the predicted TS values in the frequency range of 100-160 kHz. However, there was good agreement between the predicted and measured TS values in the frequency range of 160-200 kHz. The significant similarity between the model-predicted and experimentally measured TS values supports the use of the Kirchhoff-ray mode (KRM) model for acoustic scattering analysis of cuttlebones. Accordingly, we concluded that the KRM model can be used as a tool to evaluate the frequency-dependent variability of TS due to changes in golden cuttlefish swimming depth.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.941-949
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• 2006

Nonlinear behavior analysis was used to verify whether a one-way clutch is effective for reducing the torsional vibration of a paired spur gear system under periodic excitation. The dynamic responses were studied over a wide frequency range by speed sweeping to check the nonlinear behavior using numerical integration. The gear system with a one-way clutch showed typical nonlinear behavior. The oscillating component of the dynamic transmission error was reduced over the entire frequency range compared to a system without a one-way clutch. The one-way clutch also eliminated unsteady continuous jump phenomena over multiple solution bands, and prevented double-side contact, even with very small backlash. Installing a one-way clutch on both sides of the gear system was more effective at mitigating the negative effects of external periodic excitation and various parameter changes than a conventional gear system without a one-way clutch.

• Mass Spectrometry Letters
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• v.4 no.4
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• pp.91-94
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• 2013

We performed computer simulations to improve transmission efficiencies of a dual ion funnel system implemented on an FT-ICR MS. We found that the low m/z range from 50 to 150 could be significantly improved by operating the two ion funnels at different RF amplitudes. These new operational conditions could be applied to analyze metabolome samples, which require high sensitivity in the m/z range from 50 to 1,000.

• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.6
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• pp.12-15
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• 1976

This paper presents the realization method of 90$^{\circ}$ constant phase shifter in the VHF band, constructed by the entirely differens idea from the conventional method of the realization of constant phase shifter in the audio frequency range. The construction of 90$^{\circ}$ constant phase shifter is. simple and can be easily realized by using the distributed constant element, transmission line, and the lumped constant elements, R,C,L.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.11-13
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• 2013

We have developed a terahertz time-domain spectroscopy (THz-TDS) system for transmission and reflection measurements of metallic thin films. Using our THz-TDS system, we studied the conventional superconductor niobium (Nb) in the normal state in the spectral range from 5 to $50cm^{-1}$. Both the real and imaginary parts of the conductivity are acquired without Kramers-Kronig analysis. Nb exhibits a nearly frequency independent real conductivity spectrum in the terahertz range, with a very small imaginary part.