• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1C
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• pp.130-137
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• 2010

An uplink indoor positioning system is proposed in the present work, where the acoustic signals are solely used for positioning. The underlying acoustic signals include whistle, finger snap, and hands-clapping. In the proposed method, positioning is achieved by finding the time-difference-of-arrivals using several self-generating sounds. To evaluate the feasibility of the signals and their positioning accuracies, the database of 100 persons about self-generating acoustic signals is built up. The results show that the hands-clapping sound is the most suitable for acoustic-based indoor positioning.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.857-863
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• 2014

In determining interaction between plasma and electromagnetic wave, plasma frequency and collision frequency are two key parameters. They are derived from electron density and temperature, which vary in an extremely wide range, depending on a plasma generator. Because the parameters are usually unknown, traditional researches have utilized simplified electron density model and constant electron temperature approximation. Introduction of plasma fluid model to electromagnetics is suggested to utilize relatively precise time dependent variables for given generator. Dielectric barrier discharge(DBD) generator is selected due to its simple geometry which allows us to use one dimensional analysis. Time dependent property is analyzed when microwave is launched toward parallel plate DBD plasma. Afterwards, attenuation tendency with the change of electron density and temperature is demonstrated.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.1
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• pp.40-50
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• 1994

Through the low orbit GPS satellite a 3-dimensional real time position detection can be achieved anywhere. Utilizing the GPS satellite detection values an analysis of the varing characteristics of the iono- sphere can be achicved, and by calculating the correlation relationship of the position detection error and the ionospheric time delay characteristics, an advanced algorithm technique can be developed. Computer simulation of the developed algorithm for defining the correlation between the position detec- tion error and the varing ionospheric time delay characteristics has been proceeded. The results of simulation reveal the fact that the varing characteristics of the ionosphere nearly match the actual ionospheric time delay characteristics.

• Tunnel and Underground Space
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• v.16 no.4 s.63
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• pp.326-333
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• 2006

In this study, the vibration waveform of the single hole which is not interfered from the different blasting holes is separated, the each dominant frequency which is determinated through the Fast Fourier Transform(FFT) is measured. Also the separation waveform executed a superposition modeling which changes to delay time from 1ms to 80 ms in 1ms interval and controls the number of blasting holes from 2 holes to 15 holes in order to investigate the effect of PPV according to the duration time of the vibration and the number of blasting holes. As a result of analysis, the longer the duration time of the vibration, the longer the delay time which is not interfered from the different blasting holes and the effect regarding the number of blasting holes from inside identical delay time did not appear a lot.

• The Journal of the Acoustical Society of Korea
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• v.38 no.3
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• pp.363-369
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• 2019

Various studies have been conducted for the diagnosis of noise condition of complex rotary machines. In this study, diagnosis index using vibration signal is developed for the efficient and objective assessment of noise condition of a blower motor. The noise most commonly caused by the abnormal blower motor are Tick/Click noise and Tone noise. According to cause and noise characteristics, time-frequency analysis is used to diagnose Tick/Click noise, and smoothing in frequency domain is used to diagnose tone noise condition. The noise condition of the blower motors were diagnosed using the developed index and these results are compared with the diagnostic results by the experts. As a result, the agreement rate was about 95 %.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2007.04a
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• pp.473-476
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• 2007

본 논문에서는 LBT(Listen Before Talk) 방식을 사용하는 ZigBee와 FH(Frequency Hopping) 방식을 사용하는 DCP, RFID, Bluetooth 등의 소출력 무선기기가 공유주파수대역에 공존할 경우 요구되는 적정 채널수를 산출하고 전체 공유주파수대역폭 산출법을 제시하였다. 한정된 주파수 대역에서 LBT 및 FH 방식을 사용하는 총 User 수가 포용되는 공유주파수대역폭 산출은 중요한 작업이다. 소출력 무선기기 시스템의 간섭 회피 기술로 사용되는 FH 방식과 LBT 방식에 대기행렬이론(Queueing Theory)을 적용하였으며, 주위의 전파환경을 감지하여 유휴 주파수대역을 찾아 데이터전송을 시도하는 LBT 방식은 random하게 주파수채널을 이동하며 통신을 시도하는 FH 방식과는 구별된다. 채널수 별 User의 통신시도 시간간격을 통계적으로 처리하여 Throughput을 분석한 결과, Throughput 70% 조건에서 FH 방식과 LBT 방식을 사용하는 250mW 소출력 무선기기들이 공존하는 공유주파수대역의 적정 채널수는 30개를 가지며, 전체 공유주파수대역폭은 채널수에 채널당 대역폭의 곱으로 산출이 가능하다.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.175-176
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• 2006

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.795-798
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• 2000

연속음 인식과 음성 합성을 위해서는 정밀한 음성학적 모델과 연속 음성에 적용 가능한 언어 모델의 개발이 중요하다. 이를 위해서는 음성 데이터 베이스에 대한 인식 단위, 혹은 합성 단위의 분할이 필요한데, 수동음성 분할은 일관성의 유지가 어렵고 긴 시간이 소요되므로 최근에는 자동 분할 기술이 많이 연구되고 있다. 자동 음성 분할 기법으로는 시간 영역이나 주파수 영역특징 벡터의 천이를 분석하는 방법과 특징 벡터간의 상관도를 구하여 경계를 추출하는 방법이 있다. LPC smoothed log amplitude spectra는 음성의 주파수 영역의 특징을 잘 나타내며, 동일 음소 내의 상관도가 서로 다른 음소의 상관도보다 더 크고, 음소의 경계구간에서 급격한 상관도의 변화를 보인다. 이 특성을 이용하여 이웃 프레임에 대한 상관도의 방향성이 특정조건을 만족하는가를 검사하여 음소의 경계를 구하는 방법을 찾았다. 또한 LPC. 이득 인자만으로 묵음 구간을 검출하는 방법을 제시한다. 이렇게 하면 묵음 구간검출과 음소 경계 검출의 일관성을 향상시키고 수행 시간을 단축시킬 수 있다. 제안한 기법으로 허용 오차 20ms 이내에서 연속음성에 대한 음소 경계 검출 실험을 수행한 결과, 수작업으로 행한 경계 검출 지점의 약 88%를 정확히 검출하였다.

• The Journal of the Acoustical Society of Korea
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• v.7 no.4
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• pp.31-53
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• 1988

In this work we study extensively the structures and performance characteristics of the block least mean-square (BLMS) adaptive digital filters (ADF's) that can be realized efficiently using the fast Fourier transform (FFT). The weights of a BLMS ADF realized using the FFT can be adjusted either in the time domain or in the frequency domain, leading to the time-domain BLMS(TBLMS) algorithm or the frequency-domain BLMS (FBLMS) algorithm, respectively. In Part Ⅰof the paper, we first present new results on the overlap-add realization and the number-theoretic transform realization of the FBLMS ADF's. Then, we study how we can incorporate the concept of different frequency-weighting on the error signals and the self-orthogonalization of weight adjustment in the FBLMS ADF's , and also in the TBLMS ADF's. As a result, we show that the TBLMS ADF can also be made to have the same fast convergence speed as that of the self-orthogonalizing FBLMS ADF. Next, based on the properties of the sectioning operations in weight adjustment, we discuss unconstrained FBLMS algorithms that can reduce two FFT operations both for the overlap-save and overlap-add realizations. Finally, we investigate by computer simulation the effects of different parameter values and different algorithms on the convergence behaviors of the FBLMS and TBLMS ADF's. In Part Ⅱ of the paper, we will analyze the convergence characteristics of the TBLMS and FBLMS ADF's.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.1-6
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• 2001

In this paper, we propose the initial optimized structure of the Radial Basis Function Network(RBFN) which is more simple in the part of the structure and converges more faster than Neural Network. For this, we use the analysis method using time frequency localization and we can decide the initial structure of the RBFN suitable for the given problem. When we compose the hidden nodes with the radial basis functions whose localization are similar with the target function in the plane of the time and frequency, we can make a good decision of the initial structure having an ability of approximation.