• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.12
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• pp.1438-1446
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• 2010

In this paper, we compared and analyzed the antenna characteristics such as bandwidth, efficiency, and readable range in terms of the size and the number of turns of the multiple meander RFID tag antenna in the UHF band. The sizes of the each antenna are $20.0{\times}19.7$, $25.0{\times}24.8$ and $30.0{\times}29.7\;mm^2$. The bandwidths of the antennas for VSWR<5.8 are 857~963 MHz, 844~965 MHz, and 844~968 MHz which cover the worldwide UHF RFID bandwidth. The readable range of the antenna was greatly affected by the efficiency and gain of the antenna which depends on the size and the number of turns of the meander antenna.

• The Journal of the Acoustical Society of Korea
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• v.25 no.1
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• pp.21-29
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• 2006

In this Paper a split bandwidth wideband speech coder and its highband coding method are Proposed. The coder uses a split-band approach. where the wideband input speech signal is split into two equal frequency bands from 0-4kHz and 4-8kHz. The lowband and the highband are coded respectively by the 11.8kb/s G.729 Annex E and the proposed coding method. After the LPC analysis, the highband is divided by two modes according to the properties of signals. In stationary mode. the highband signals are compressed by the mixture excitation model; CELP algorithm and W (Matching Pursuit) algorithm. The others are coded by the only CELP algorithm. We compare the performance of the new wideband speech coder with that of G.722 48kbps SB-ADPCM and G.722.2 12.85kbps in a subjective method. The simulation results show that the Performance of the proposed wideband speech coder has better than that of 48kbps G.722 and no better than that of 12.85kbps G.722.2.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.484-491
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• 2013

In this paper, the method of designing a wideband antenna has been introduced through the design technique that simultaneously employs L- and slot-type feeds. Using the two kinds of feeds and additional fence structure, a compact wideband patch antenna has been realized. The size of the patch has been reduced by about 30 % based on the low frequency(824 MHz) and the full fractional bandwidth is wider than 100 %. The L-feed element is for the EM coupling feeding at the low frequency, while it functions as a feeding line for the power coupling through the slot at the high frequency. The proposed antenna has been designed not only for wideband operations but also for a proper array element with a reduced size. Thus, the foundation for developing the ultra wideband patch array antennas has been prepared. The fabricated antenna has been found to have good characteristics on V.S.W.R and the radiation patterns over the full bands. The experimental and computed results are shown to be in good agreement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.886-894
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• 2014

A wideband bow-tie antenna fed by wideband microstrip-coplanar stripline(CPS) balun and band notch structures that can be applied to bow-tie antenna are proposed in this paper. In order to increase bandwidth, bow-tie radiators are reshaped so that the surface current flows continuously, and wideband impedance matching is achieved by adjusting strip width and spacing of CPS feeding line. The VSWR is measured as 2:1 over the wide frequency range of 2.3~12 GHz. The fabricated antenna size is $60mm{\times}60mm$. In order to achieve the band-notch function at WLAN(5.8 GHz), ${\lambda}/4$ folded-slits located ${\lambda}/4$ away from feeding point are utilized. To minimize the slit size, folded-slit type is adopted. The measured VSWR is 7:1 and gain attenuation is 14 dB at 5.8 GHz.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.546-559
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• 1997

The purposes of this study were to evaluate the efficiency of cavity preparation and to determine the incidence of tooth crack when root-end retrograde cavity preparation was done with ultrasonics. 91 distobuccal root-ends of extracted human maxillary first molars were cut by 3 mm perpendicularly to the long axis of tooth using a slow speed diamond saw, retrocavities were prepared using a slow-speed no. 2 round bur as controls, and stainless steel ultrasonic tips of power settings of 1 through 10 as experimentals. Time consumed and the number of strokes used for the cavity preparation were measured and evaluated, and the incidence of tooth cracks was observed under a stereomicroscope. The results were as follows : For the retrograde cavity preparation, time and number of strokes used were decreased as the ultrasonic power setting increased (p<0.001). High power setting of ultrasonics induced significantly more tooth cracks than did the slow-speed bur or low- and medium power setting of ultrasonics (p<0.05). Teeth with previous crack induced significantly more tooth cracks than those without previous one when high power setting of ultrasonics were used for the retrograde cavity preparation (p<0.001). Teeth with initial apical canal size of no. 10 induced significantly more crack than did those with size of no. 15 when low power setting of ultrasonics were used for the retrograde cavity preparation (p<0.05).

• Journal of the Korean earth science society
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• v.41 no.6
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• pp.647-657
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• 2020

Infrasound signals associated with the 29 May 2004 offshore Uljin earthquake (Mw 5.1) were recorded at infrasound arrays of CHNAR (epicentral distance of 321 km) and TJNAR (256 km). Back-azimuths, indicating the directions to source locations, varied more than 28° broadly for the long-lasting signals over several minutes. From the analysis of the back-projecting location method and attenuation correction for infrasound propagation, the infrasound waves were to be generated by the interaction (diffraction) between seismic waves and topography in an area of ~4,600 ㎢ connecting the Samcheok-Uljin-Pohang regions. The maximum sound source pressure (BSP) was estimated to be 11.1 Pa. This result was consistent with the peak sound pressure (PSP) calculated by the Rayleigh integral approximation to the peak ground acceleration (PGA) dataset. In addition, the minimum PGA that was detectable at the two arrays was estimated to be ~3.0 cm s-2. Although the earthquake occurred offshore, diffracted infrasound signals were effectively generated by ground motions when seismic surface waves passed through high-topographic regions in the eastern Korean Peninsula. The relationship between infrasound source pressure and PGA can be applicable to characterize the ground motions in areas with insufficient seismological observatories.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2010.04a
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• pp.193-193
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• 2010

이전의 연구에서 우리는 선응집 기술을 적용한 중질탄산칼슘의 크기에 따른 수초지의 물성을 평가하였다. 이때 선응집 기술이 적용된 충전물의 입도와 분포를 측정하기 위해 light diffraction spectroscopy (LDS) 가 사용되었다. 경질탄산칼슘과 양이온성 고분자의 흡착 현상을 알아보기 위한 이번 연구에도 LDS가 사용되었으며, 일회성으로 입자의 크기와 분포를 측정하는 것에서 더 나아가 시간의 흐름에 따라 응집체의 형성과 파괴, 재성장을 관찰할 수 있는 도구로서 역할 하였다. 본 연구에서 우리는 세 가지 경우로 나누어 경질탄산칼슘의 응집 현상을 관찰하였다. 첫째로 경질탄산칼슘에 흡착되는 양이온성 고분자의 특성, 분자량과 전하밀도, 을 달리하여 응집체의 성장과 파괴를 관찰하였다. 둘째, 양이온성 고분자로 중질탄산칼슘을 응집시켜, 경질탄산칼슘 응집체의 경우와 입도와 전단 안정성 등을 비교하였다. 마지막으로 나노 크기의 실리카 투입이, 마이크로 크기의 경질탄산칼슘 응집체가 강한 전단에 의해 파괴되었을 때, 응집체의 전단 안정성이나 재성장 측면에 도움을 주는지 관찰하였다. 내첨용 충전물로써 경질탄산칼슘의 사용이 전 세계적으로 늘고 있는 시점에서 양이온성 고분자 첨가에 의한 경질탄산칼슘의 응집 현상을 관찰하는 것은 일반적인 제지 공정에서 경질탄산칼슘의 거동을 이해하는데 도움이 될 뿐만 아니라, 내첨용 충전물 첨가에 따른 종이의 강도 저하 방지를 위한 선응집 기술의 적용에도 도움이 될 수 있을 것으로 생각한다.

• Journal of Korean Society for Geospatial Information Science
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• v.11 no.3 s.26
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• pp.47-53
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• 2003

Recently, there is studying about slope analysis according to cell size and affect in conformity to determination of hydrologic topographical parameters the cell size a classified map scale about subwatershed. In this study, we wish to offer the base data to determination of hydrologic topographical parameters request of runoff model analysis in this basin on the basis of this results that we compute the CN(curve number) using GIS after classify the map of soil and landuse on the Su-Young River basin. Also, as determination a classified cell size of $100m{\times}100m$ in case of the most optimum size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.1
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• pp.8-15
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• 1998

In this paper, to improve the bandwidth of microstrip antenna, we discussed parasitic patch structure coupled capacitively at radiating slot. To reduce the overal size of antenna,$\lambda$/4 short structure is accepted instead of $\lambda$/2 patch. Since ground plane is reduced, backward radiation is occurred. The characteristics of the designed antenna is evaluated, based on the transmission line model and the aperture analysis method. And by computer program the radiation pattern and return loss are evaluated. As simulation results, backward radiation is -15 dB. Bandwidth of constructed antenna is 167 MHz at the resonant frequency of 2.45 GHz, which is very broad, compared to conventional microstrip antennas. Therefore the proposed antenna will be suitable for very wide bandwidth communications.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.9 no.4
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• pp.71-84
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• 1999

The randomness test for a sequence from an encription algorithm has an important role to make differences between plain and cipher text. Thus it is necessary to investigate and analyze the currently used randomness tests. Also in real time point of views it would be helpful to know a minimum sample size which gives discernment of plain and cipher text. In this paper we analyze the rate of successes for widely used nonparametric randomness tests to discern plain and cipher text through experiments. Moreover for given sample sizes an optimal sample size for each randomness test is proposed using the design of experiments.