• Journal of Korean Society of Environmental Engineers
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• v.27 no.4
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• pp.353-361
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• 2005

In this study, we performed whole effluent toxicity(WET) test and compared the biological component analyses tests for some streams into which wastewater treatment plant effluents are discharged. The test procedures for the WET test and the biological component analysis were conducted according to U.S. EPA guidelines and the Ohio EPA wading method. The WET tests based on the test species of D. manga and S. capricornutum All treatment plants showed a S. capricornutum toxicity, and at 7 sites, except A and J, we could observe a D. magna toxicity. The highest toxicity was observed at site D and this were followed by E and F. The biological component analyses applied to the effluent discharged stream. We found that total species were low at sites C1, D1 and J1 and the low number of total individuals were observed at sites A1, C1, E1, H1, and J1 compared to the controls and other sites. The species richness was low at sites A1, B1, C1, D1, and J1. The species change was evident at site D(D1) and the tolerant species was predominant. The biological analyses and WET tests suggested that the effluents resulted in massive ecosystem impact.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.8
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• pp.663-671
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• 2013

Recently, the Wi-Fi Direct standard based on WLAN is getting more attention as a new technology for enabling D2D(Devide-to-Device) communications on mobile devices. However, due to limited power resource of mobile devices and, an energy inefficiency problem can be an issue. In order to solve this problem, the Wi-Fi Direct defines two power management schemes: Opportunistic scheme and Notice of Absence(NoA) scheme. However, there is no concrete description of which power management scheme would be better for when. In this paper, via comprehensive simulation studies using ns-3, we show that each scheme presents obviously different performance and energy efficiency according to data traffic patterns. We then propose more energy efficient way of dynamically switching the two power management schemes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.27-30
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• 2016

in this paper, to improve the narrow bandwidth problem of the microstrip antenna for WLAN and WiFi dual band array antenna was designed to satisfy the bandwidth of 3.6GHz and 5.2GHz it contained with IEEE 802. 11. The substrate of proposed microstrip array antenna is FR-4(er=4.3) and $25mm{\times}45mm{\times}0.8mm$ size and thickness t=0.035mm, and the simulation was used for CST Microwave Studio 2014. input return loss compared -10dB less than operates at and when gain 3.6GHz 2.516dB, 5.2GHz showed the results of 3.581dB. the antenna designed to be miniaturized and the be used in electronic devices such as mobile phone.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.8
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• pp.65-73
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• 2007

This paper presents a low power CMOS continuous-time $\Sigma\Delta$ (sigma-delta) modulator for UMTS receivers. The loop filter of the continuous-time $\Sigma\Delta$ modulator consists of an active-RC filter which performs high linearity characteristics and has a simple tuning circuit for low power operating system The architecture of this modulator is the $3^{rd}-order$ 4-bit single loop configuration with a 24 of OSR (Oversampling Ratio) to increase the power efficiency. The modulator includes a half delay feedback path to compensate the excess loop delay. The experimental results of the modulator are 71dB, 65dB and 74dB of the peak SNR, peak SMR and dynamic range, respectively. The continuous-time $\Sigma\Delta$ modulator is fabricated in a 0.18-um 1P4M CMOS standard process and dissipates 15mW for a single supply voltage of 1.8V.

• The Journal of the Acoustical Society of Korea
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• v.13 no.5
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• pp.59-68
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• 1994

This paper describes the performance assessment test and analysis of test results on a Korean speech recognizer which recognizes Lombard effect received speech in noisy environment, as a basic performance assessment research. In the assessement test, standard speech data were first manipulated close to speech uttered in a noisy environment, and then performance assessment tests were carried out along with the assessment items (the type of noise, SNR) in two ways-one with Lombard effect received speech(LES), the other with not received(NLES). As a result, when 90% of recognition rate is set to be a recognition limit, it was achieved at 10dB SNR point with LES, while at 30dB with NLES. This 20dB of SNR difference indicates Lombard effect should be considered in real world assessment test. The type of noises didn't affect performance of recognizers in out tests. ANOVA analysis, in evaluating several kinds of recognizers, showed every assessment item affecting the recognition performance could be quantified.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.1
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• pp.49-58
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• 1999

This paper describes an integrated low pass filter fabricated by using $0.8{\mu}m$ single poly CMOS ASIC technology. The filter has been designed for a 5th-order elliptic switched capacitor filter with cutoff frequency of 5khz, 0.1dB passband ripple. The filter consists of MOS swiches poly capacitors and five CMOS op-amps. For the realization of the SC filter, continuous time transfer function H(s) is obtained from LC passive type, and transfered as discrete time transfer H(z) through bilinear-z transform. Another filter has been designed by capacitor scaling for reduced chip area, considering dynamic range of the op-amp. The test results of two fabricated filters are cutoff frequency of 4.96~4.98khz, 35~38dB gain attenuation and 0.72~0.81dB passband ripple with the ${\pm}2.5V$power supply clock of 50KHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1316-1322
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• 2004

Recently, the UWB (ultra wide-band) wireless communication technology, which provides high data transmission and is capable of linearly trading between throughput and signal-to-noise ratio (SNR), has drawn much attention for short-range wireless networks. Fully exploiting its notable features and minimizing its interference to coexisting other systems require the knowledge of SNR's at receivers In this paper, we propose an algorithm for estimating the pulse energy to noise ratio Ep/No of UWB signal with utilization of outputs from a correlator at a receiver, and evaluate the performance of the proposed algorithm through computer simulation. According to simulation results, the maximum standard deviation is about 1 13 dB with a block size of 500. Except for Ep/No=O and 2 dB cases with a block size of 500, no errors greater than 3 dB were observed in all the remaining experiments. Generally speaking, it improves as the true Ep/No, increases and as the block size increases A notable feature of the proposed algorithm is that it does not reduce the effective throughput because the estimation process does not require sending additional training signal of any specific format.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10A
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• pp.1563-1570
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• 1999

This paper relates to the soft decision method with erasure technique in digital terrestrial television broadcasting system. The proposed decoder use the CSI derived from using the pilots in receiver. The active real(I) and imaginary(Q) data are transferred to the branch metric calculation block that decides the Euclidean distance for the soft decision decoding and also the estimated CSI values are transferred to the same block. After calculating the Euclidean distance for the soft decision decoding, the Euclidean distance of branch metric is multiplied by CSI. To do so, new branch metric values that consider each carrier state information are obtained. We simulated this method in better performance of about 0.15dB to 0.17dB and 2.2dB to 2.9dB in Rayleigh channel than that of the conventional soft decision Viterbi decoding with or without bit interleaver where the constellation is QPSK, 16-QAM and 64-QAM.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.162-167
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• 2024

Low frequency noise emitted by wind turbines is one of the most noise complaints. In this study, the reliability of the models was examined by comparing the measured sound pressure levels with the predicted levels based on Denish model and commercial programs of the SounPLAN and the ENPro based on ISO 9613. As a result of applying it to representative 3 MW wind turbines, on lnad, the measured and the predicted values differed within a maximum of 5 dB in the frequency range of 12.5 Hz to 80 Hz. It may be due to the change in the acoustic power levels because the wind turbines have been in operation for more than 7 years. However, considering that the Boundary Element Method (BEM) predicted value, which is known to be the most accurate in the low frequency band, the predicted values are well matched within 2.5 dB, the models of this study are expected to be used as deviation within 3 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.32-37
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• 2007

A DMB CMOS power amplifier (PA) with high efficiency and linearity is present. For this work, a 0.13-um standard CMOS process is employed and all components of the proposed PA are fully integrated into one chop including output matching network and adaptive bias control circuit. To improve the efficiency and linearity simultaneously, an adaptive bias control circuit is adopted along with second harmonic termination circuit at the drain node. The PA is shown a $P_{1dB}$ of 16.64 dBm, power added efficiency (PAE) of 38.31 %, and power gain of 24.64 dB, respectively. The third-order intermodulation (IMD3) and the fifth-order intermodulation (IMD5) have been -24.122 dBc and -37.156 dBc, respectively.