Earticle

주행 중인 차량의 타이어에서 발생하는 초음파 신호의 포락선에서 손상 물질에 의한 특징 신호의 주기를 검출하여 타이어 손상을 분별하는 방법을 연구하였다. 손상된 타이어는 주행 시 회전에 의해 주기성을 갖는 신호를 발생하기 때문에 이를 펄스화하고 펄스 간의 시간 간격을 밀도함수로 나타내어 우성 주기를 검출하였다. 펄스화하기 위한 임계값은 포락선 신호를 이동평균필터 처리하여 결정하였다. 손상물질이 한 개이고, 주행속도가 약 50km/h, 80km/h일 때, 시간밀도함수의 결과는 제 1 피크시간이 156ms, 102ms로 주행속도에 따라 계산한 타이어의 회전주기와 일치하였고, 한 개 이상의 손상물질의 경우에는 각 피크시간의 합이 타이어의 회전주기와 동일한 결과를 얻을 수 있었다.

The tire damage classification method is researched by periodicity detection of ultrasonic envelope signals to occur at the driving vehicle tire. Because periodic signals is generated by rotations of the damaged tire, it should convert to pulse for using the density function. After time intervals of pulses are represented by the density function, the dominant periodicity is detected. The threshold to make a pulse is calculated by moving average of envelope signals. The result of time density function in case of one damage material, the first peak's time is equals to tire's rotation period, 162ms and 102ms, about the speed of 50km/h and 80km/h. In case of more than one damage material, the sum of each peak's time is equals to tire's rotation period about the speed.

차량 주행 중에 타이어에서 발생하는 초음파를 이용하여 손상 물질에 의한 타이어의 손상을 검출하는 방법에 대해 연구하였다. 손상이 있는 타이어는 회전 주기성이 있는 초음파 신호가 발생하므로 주기성을 검출하기 위해 포락선 검출 전처리 과정을 거친 후 자기상관함수를 사용하였다. 실험에서는 손상된 타이어의 1회전 시간과 자기상관함수를 이용해 구한 주기가 같은 것으로 나타났다. 이로 인해 타이어의 손상 유무를 분별할 수 있는 결과를 도출하였다.

The damage of tire by damage material classification method is researched as used ultrasonic wave signal to occur at a tire during vehicle driving. Auto-correlation function after having passed through an envelope detecting preprocess is used for detecting periodicity because of occurring periodic ultrasonic waves signal with tire revolution. One revolution cycle time of a damaged tire and period that calculated auto-correlation function appeared equally in experiment. The result that can classification whether or not there was a tire damage is established.

This paper proposes a linearization method that is to control the operating point of a class AB amplifier according to its output power. The proposed linearization method is presented in this paper and the performance test results using two-tone signal are presented also.

사전 왜곡형 선형 증폭기는 회로가 간단하고 제작 비용이 적은 장점이 있으나, 상호 변조 왜곡 hump 특성 때문에 낮은 출력 전력에서 상호 변조 왜곡 특성이 나빠지는 단점이 있다. 본 논문에서는 출력 전력에 따라 전력 증폭기의 바이어스를 제어하는 방법으로 이와 같은 단점을 개선하였다. AB급 바이어스를 사용한 16 W급 사전 왜곡형 전력 증폭기에 본 논문에서 제안한 방법을 적용한 결과, 넓은 출력 전력 범위에서 약 10 dB의 3차 상호변조 왜곡 특성이 개선됨을 확인하였다.

In spite of the advantage of simple circuit, small size, and low price, predistortered power amplifier does not satisfy the IMD specification at low power range because of an IMD hump characteristic. To reduce the performance degradation by IMD hump, the method which is to control the operating point of amplifier according to its output power is presented. This method using envelope detection bias control is applied to the implemented class AB predistortered 16 W power amplifier. The measured result shows 10 dB improvement of $3^{rd}$ IMD performance in wide dynamic range of output power.

Heart sound segmentation into its components, S1, systole, S2 and diastole is the first step of analysis and the most important part in the automatic diagnosis of heart sounds. Conventionally, the Shannon energy envelope peak detection method has been popularly used due to its superior performance in locating S1 and S2. Recently, the HMM has been shown to be quite suitable in modeling the heart sound signal and its use in segmenting the heart sound signal has been suggested with some success. In this paper, we compared the two methods for heart sound segmentation using a common database. Experimental tests carried out on the 4 different types of heart sound signals showed that the segmentation accuracy relative to the manual segmentation was 97.4% in the HMM based method which was larger than 91.5% in the peak detection method.

Chikungunya virus (CHIKV), a tropical pathogen, has re-emerged and has massive outbreaks abruptly all over the world. Containing many dominant epitopes, the envelope E2 protein of CHIKV has been explored for the vaccination or diagnosis. In the present study, the antigenicity of a recombinant expressed intrinsically disorder domain (IUD) of E2 was tested for the detection of the antibody against CHIKV through western blot method. The gene of the IUD of E2 was inserted into 2 different vectors and expressed as recombinant GST-E2 and recombinant MBP-E2 fusion protein, respectively. Two kinds of fusion proteins were tested with 30 CHIKV patient sera and 30 normal sera, respectively. Both proteins were detected by 25 patients sera (83.3%) and 1 normal serum (3.3%). This test showed a relatively high sensitivity and very high specificity of the recombinant E2 proteins to be used as diagnostic antigens against CHIKV infection.

We propose an improved algorithm for detecting audio watermarks based on a spread spectrum in the spectral domain. Since the energy of a watermark is much smaller than that of the cover audio data, pre-processing to reduce the effect of the cover data is needed to reliably extract watermarks. We introduce a spectral envelope filter as a pre-process that enhances detecting performance by filtering out the intrinsic spectral character of cover data. The proposed watermarking structure can be easily included in the compression system and can extract watermarks from partially decompressed spectral data. Our experimental results demonstrate that with a bit error rate of around 10 dB against general attacks, the proposed detecting scheme works better than detectors without the spectral filter.

심음도(PCG, Phonocardiogram) 분석을 이용하여 심장의 판막과 관련된 질환을 진단하기 위해서는 먼저 심음 분할을 위해 심음의 주성분인 S1과 S2를 정확하게 찾아야 한다. 본 논문에서는 심음포락선의 모멘트 특성을 분석하고 이를 심음 분할에 적용하였다. 기존의 2차 모멘트를 이용한 심음 분할의 문제점을 분석하고, 심잡음이 있더라도 심음 주성분의 검출이 용이한 3차 모멘트에 기반한 방법을 제안하였다. 심음포락선은 심음 신호의 단구간 에너지를 이용하였으며, 3차 모멘트 궤적의 기울기 정보를 이용하여 심음 주성분을 검출하고 지속시간을 게이팅(gating) 하였다. 다양한 심잡음이 포함된 심음 신호에 대한 실험을 통해 제안한 방법이 기존의 2차 모멘트 기법보다 심잡음의 영향을 적게 받고 심음 주성분의 구간을 정확하게 검출 할 수 있음을 보였다.

To diagnose the cardiac valve abnormalities using analysis of phonocardiogram, first of all, accurate detection of S1, S2 components is needed for heart sound segmentation. In this paper, a new method that uses the third moment characteristics of an envelope of the PCG is proposed for accurate detection of S1 and S2 components of the heart sound with cardiac murmurs. The envelope of the PCG is obtained from the short-time energy profile, and its third moment profile with slope information is used for accurate time gating of the S1, S2 components. Experimental results have shown that the proposed method is superior to the conventional second moment method for detection of S1 and S2 regions from the heart sound signals with cardiac murmurs.