• MALSORI
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• no.61
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• pp.75-86
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• 2007

In this paper, we propose a scalable audio coder, which has a variable bandwidth from the narrowband speech bandwidth to the audio bandwidth and also has a bit-rate from 8 to 320 kbits/s, in order to cope with the quality of service(QoS) according to the network load. First of all, the proposed scalable coder splits bandwidth of the input audio into narrowband up to around 4 kHz and above. Next, the narrowband signals are compressed by a speech coding method compatible to an existing standard speech coder such as G.729, and the other signals whose bandwidth is above the narrowband are compressed on the basis of a psychoacoustic model. It is shown from the objective quality tests using the signal-to-noise ratio(SNR) and the perceptual evaluation of audio quality(PEAQ) that the proposed scalable audio coder provides a comparable quality to the MPEG-1 Layer III (MP3) audio coder.

• Journal of Radiation Protection and Research
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• v.31 no.1
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• pp.25-30
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• 2006

To know radon and uranium concentration variations in groundwater with regional difference, groundwaters were sampled at five different Daejeon area. Seventy-five samples were analyzed and forty samples were collected twice at drying and after raining season to know surface water effect. The average radon and uranium concentration of five areas are $270.9{\pm}152.3\;Bq/L,\;43.8{\pm}23.5\;{\mu}g/L$ at Yusung-gu, $112.9{\pm}65.8\;Bq/L,\;0.45{\pm}0.23\;{\mu}g/L$ at Seo-gu, $41.3{\pm}24.0\;Bq/L,\;4.9{\pm}11.3\;{\mu}g/L$ at Dong-gu, $131.8{\pm}99.5\;Bq/L,\;54.3{\pm}127.5\;{\mu}g/L$ at Daeduk-gu and $44.0{\pm}43.0\;Bq/L,\;8.1{\pm}11.6\;{\mu}g/L$ at Jung-gu. The mean concentrations of analyzed samples to know surface water effect were ranged from 0.5 to 640 ${\mu}g/L$ for uranium and from 0.4 to 729 Bq/L for radon. The average concentration of radon and uranium after raining season were lower than those of drying season. The mean contents of radon End Uranium at drying season were $253{\pm}14\;Bq/L,\;63{\pm}12.2\;{\mu}g/L$, and $195{\pm}11\;Bq/L,\;45.4{\pm}11.7\;{\mu}g/L$ after raining season.

• The Korean Journal of Food And Nutrition
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• v.25 no.4
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• pp.729-736
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• 2012

The purpose of this study is to determine the possibility of using cultured wild ginseng roots as a natural health food source. To accomplish this purpose, the contents of general and antioxidative nutrients of cultured wild ginseng roots were measured. The contents of carbohydrate, crude protein, crude lipid and ash are 61.72%, 17.36%, 0.23% and 10.90%, respectively. Further, the calories of cultured wild ginseng roots were 323.97 kcal. Total dietary fiber was 82.13%. The protein contained a total of 18 different kinds of amino acids. The contents of amino acids were 16.15 g. The K was the largest mineral followed by P, Ca, and Mg, which means cultured wild ginseng roots is alkali material. The contents of saturated fatty acids and unsaturated fatty acids were 0.23 g, and 0.62 g, respectively. Crude saponine content was 25.87 mg/g. Total phenolic contents of cultured wild ginseng roots were 11.2mg/g, and total flavonoids contents were estimated as 4.2mg/g. The electron donating ability of cultured wild ginseng roots were 24.7~31.6%. The nitrite scavenging activity was pH dependent, and was highest at pH 1.2 and lowest at pH 6.0. The cultured wild ginseng roots extract showed the highest reducing power (0.06) at the concentration of $1,000{\mu}g/m{\ell}$. Based on the above results, we deemed that the cultured wild ginseng roots might have potential antioxdant activities.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.727-729
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• 1992

In this study, the piezoelectric composites with 1-3 connectivity have been studied. A piezoelectric ceramics PZT prepared by Flux method is used as a filler in a epoxy Eccogel polymer matrix. The piezoelectric coefficients were increased as PZT volume% increases, and resonance frequency was moved to lower frequency as the sample thickness increased. The acoustic matching impedance with water is lowered than single phase PZT ceramics.

• The Journal of the Acoustical Society of Korea
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• v.37 no.2
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• pp.110-117
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• 2018

In this paper, we propose a low delay window switching MDCT (Modified Discrete Cosine Transform) method for speech/audio coder. The window switching algorithm is used to reduce the degradation of sound quality in non-stationary trasient duration and to reduce the algorithm delay by using the low delay TDAC (Time Domain Aliasing Cancellation). While the conventional window switching algorithms uses overlap-add with different lengths, the proposed method uses the fixed overlap add length. It results the reduction of algorithm delay by half and 1 bit reduction in frame indication information by using 2 window types. We apply the proposed algorithm to G.729.1 based on MDCT in order to evaluate the performance. The propose method shows the reduction of algorithm delay by half while speech quality of the proposed method maintains same as the conventional method.

• ETRI Journal
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• v.35 no.5
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• pp.935-938
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• 2013

This letter presents an algorithm for selecting a low delay for the modified discrete cosine transform (MDCT) and inverse MDCT (IMDCT). The implementation of conventional MDCT and IMDCT requires a 50% overlap-add (OLA) for a perfect reconstruction. In the OLA process, an algorithmic delay in the frame length is employed. A reduced overlap window and MDCT/IMDCT phase shifting is used to reduce the algorithmic delay. The performance of the proposed algorithm is evaluated by applying the low-delay MDCT to the G.729.1 speech codec.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.08a
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• pp.465-469
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• 1998

가변 전송율 음성 부호화기를 위한 음성 검출기를 통계적 모델을 적용하여 설계한다. 제안된 음성 검출기는 음성 파라미터를 decision-directed 방식으로 추정함으로써 LRT를 이용하여 동작 특성이 우수한 판정 규칙을 유도한다. 또한 음성 발생 사건들을 1차의 Markov process 로 모델링 함으로써 과거의 관찰들을 현재 프레임의 음성 검출 과정에서 고려할 수 있는 행오버 알고리즘을 개발한다. 개발된 음성 검출기는 고려된 실험환경에서 ITU-T 표준인 G.729 Annex B 음성 검출기보다 맹 우수한 성능을 나타내었다.

• Journal of Korea Multimedia Society
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• v.7 no.7
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• pp.896-904
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• 2004

In this paper, We present an efficient variable rate speech coder for spectral efficiency and packet processing technique for packet loss compensation of a voice codec with 10msec frame in VoIP service. Through disconnecting the users from the spectral resource during silence interval of about 60% period, a variable rate voice coder based on a voice activity detection(VAD) can increase spectral gain by two times. The performance of the method was analyzed by variation of detected voice activity factor and degraded speech frame ratio under various background noise level, and compared those of G.729B of ITU-T 8kbps standard speech codec. A method to compensate lost packets utilized addition of recovery data to a main stream and error concealment scheme for speech quality enhancement, the performance is verified by reconstructed speech quality. The proposed scheme can achieve spectral gain by two times or enhance speech quality by 3dB through reserved bandwidth of VAD. Therefore, the proposed method can enhance a spectral efficiency or speech quality of VoIP.

• The Journal of the Acoustical Society of Korea
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• v.29 no.1
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• pp.48-55
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• 2010

It has a falling off in speech quality, especially when consecutive packet loss occurs, even if a vocoder implemented in the packet network has its own packet loss concealment (PLC) algorithm. PLC algorithm is divided into transmitter and receiver algorithm. Algorithm in the transmitter gives superior quality by additional information. however it is impossible to provide mutual compatibility and it occurs extra delay and transmission rate. The method applied in the receiver does not require additional delay. However, it sets limits to improve the speech quality. In this paper, we propose a new method that puts extra information for PLC in a part of Extension Header Data which is not used in RTP Header. It can solve the problem and obtain enhanced speech quality. There is no extra delay occurred by the proposed algorithm because there is a jitter buffer to adjust network delay in a receiver. Extra information, 16 bits each frame for G.729 PLC, is allocated for MA filter index in LP synthesis, excitation signal, excitation signal gain and residual gain reconstruction. It is because a transmitter sends speech data each 20 ms when it transfers RTP payload. As a result, the proposed method shows superior performance about 13.5%.

• 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.