Study for the Sonar Target Pattern Recognition Based on the Acoustic Scattering Features

Study for the Sonar Target Pattern Recognition Based on the Acoustic Scattering Features The objects of active sonar are to detect targets and further to acquire their information such as target specification, dimension, motion and state, after processing their echoes. Especially, classification and discrimination of target using active sonar need to utilize the advanced analysis of target echo features. Specular reflection and scattering from surface irregularities and inner structures contribute to the target echoes. Since contributors of echoes vary with the target kind and target aspect angle, they consititute basic features of the target signal. Feature parameters of the experimental target signal were extracted in three ways which are the envelope in time domain, the time separation pitch in frequency domain, and the short time Fourier transform in time-frequency domain. The extracted features were applied to the pattern recognition techniques to classify and discriminate target. Classifying and discriminating similarly shaped targets of which dominant component of the echo is specular reflection result in poor assortment and identification. However, the results show better performance when the effect of inner structures appears in target echoes at the specific aspect angle

효모 Saccharomyces cerevisiae 에서 O - methylguanine -DNA methyltransferase 유전자의 전사조절에 관한 연구

Thesis (doctoral)--서울대학교 대학원 :분자생물학과,1995.Docto

Optimization of Array Configuration in Time Reversal Processing and Application for Underwater Communication

Time reversal processing is useful in diverse areas, such as reverberation nulling, target echo enhancement and underwater communication. In underwater communication, the bit error rate has been improved significantly due to the increased signal to noise ratio by spatio-temporal focusing. This dissertation deals with the optimization of array configuration in time reversal processing which can provide better performance with optimal number of array element. The formulation which is based on the genetic algorithm maximizing the contrast between the foci and area of interest as an objective function is applied to determine the optimal location of array element and optimal number of element. In addition, the developed algorithm was applied to the matched field processing with ocean experimental data for verification. The sea-going data and simulation showed almost 3dB improvement in the output power at the foci when the array elements were optimally distributed. The rule of thumb which is the optimal configuration of array as a function normalized depth and normalized spacing is derived in the event. It is shown that the optimal spacing of sensor at the time reversal processing is twice of wave length by the numerical simulation and the theory of normal mode in the shallow-water waveguide. Lastly, the effect of optimal array configuration in underwater acoustic communication with passive time reversal is examined in order to assist developing underwater communication system. According to the simulation, the optimal configuration of the array is also observed in underwater communication.1. 서 론 1 1.1 연구의 필요성 및 목적 1 1.2 연구 내용 및 논문의 구성 4 2. 이론적 배경 5 2.1 시역전처리 5 2.2 정합장처리 6 2.3 유전알고리즘을 이용한 최적화 9 2.4 센서배열 최적화 모의실험 방법 13 2.5 SWellEx-96 실험 18 3. 최적 센서배치 모의실험 결과 20 3.1 최적 센서 배치 20 3.2 유효센서 개수 28 3.3 시역전처리 센서 배열 최적화 실험결과 정리 32 3.4 시역전처리 센서 배열 최적화 이론적 해석 34 4. 최적 센서배치 수중통신 적용 37 4.1 수동시역전 수중통신 37 4.2 수중통신 모의실험 39 4.3 결과 분석 47 5. 결 론 56 참고문헌 5