Evaluating the quantitative damage to rocks through acoustic emission (AE) has become a research focus. Most studies mainly used one or two AE parameters to evaluate the degree of damage, but several AE parameters have been rarely used. In this study, several data-driven models were employed to reflect the combined features of AE parameters. Through uniaxial compression tests, we obtained mechanical and AE-signal data for five granite specimens. The maximum amplitude, hits, counts, rise time, absolute energy, and initiation frequency expressed as the cumulative value were selected as input parameters. The result showed that gradient boosting (GB) was the best model among the support vector regression methods. When GB was applied to the testing data, the root-mean-square error and R between the predicted and actual values were 0.96 and 0.077, respectively. A parameter analysis was performed to capture the parameter significance. The result showed that cumulative absolute energy was the main parameter for damage prediction. Thus, AE has practical applicability in predicting rock damage without conducting mechanical tests. Based on the results, this study will be useful for monitoring the near-field rock mass of nuclear waste repository.

본 연구는 음성 인식기에서 일반적으로 사용되는 음향적 특징인 MFCC, LPC, 에너지, 피치 관련 파라미터들을 이용하여 자연스러운 음성의 정서를 범주 및 차원으로 얼마나 잘 인식할 수 있는지 살펴보았다. 자연스러운 정서 반응 데이터를 얻기 위해 선행 연구에서 이미 타당도와 효과성이 밝혀진 정서 유발 자극을 사용하였고, 110명의 대학생들에게 7가지 정서 유발 자극을 제시한 후 유발된 음성 반응을 녹음하여 분석에 사용하였다. 각 음성 데이터에서 추출한 파라미터들을 독립변인으로 하여 선형 판별 분석(LDA)으로 7가지 정서 범주를 분류하였고, 범주 분류의 한계를 극복하기 위해 단계별 다중회귀(stepwise multiple regression) 모형을 도출하여 4가지 정서 차원(valence, arousal, intensity, potency)을 가장 잘 예측하는 음성 특징 파라미터를 산출하였다. 7가지 정서 범주 판별율은 평균 62.7%이었고, 4 차원 예측 회귀모형들도 p<.001수준에서 통계적으로 유의하였다. 결론적으로, 본 연구 결과는 자연스러운 감정의 음성 반응을 분류하는데 유용한 파라미터들을 선정하여 정서의 범주와 차원적 접근으로 정서 분류 가능성을 보였으며 논의에 본 연구의 개선방향에 대해 기술하였다.

This is a study on the distribution of acoustic emission parameters during a burst test for a type-II CNG vehicle fuel tank. A resonant AE sensor with a central frequency of 150 kHz was attached to the composite materials in the center of the fuel tank. The pressure was increased from 30 to 100% of the expected burst pressure and was maintained for 10 minutes at each level. Damage at 70% of expected burst pressure occurred by various damage mechanisms including fiber breakage and delamination, while that of below 60% only occurred by matrix crack initiation and growth. The count, duration and rise time of the AE signal at 60% of the expected burst pressure are distributed below 500, 5000 μs and 300 μs, respectively. Then, at above 70% they increased with pressure by superimposing of individual AE signal generated at a nearby place. These results confirmed that the analysis of the distribution of AE parameters is an effective tool for estimating damage of a CNG fuel tank.

The purpose of this study was to investigate the effects postural changes on respiratory muscles and acoustic parameters of the children with spastic cerebral palsy. Nine children with spastic cerebral palsy who required assistance when walking were selected. The ages of the children ranged from 6 to 9 years old. The phonation of the sustained vowel /a/ and the voice qualities of each child such as fundamental frequency(F0; Hz), pitch variation (Jitter; %), amplitude variation (Shimmer; %) and noise to harmonic ratio (NHR) were analyzed by Multi-Dimensional Voice Program (MDVP). The muscle activity of three major respiratory muscles: pectoralis major muscle, upper trapezius muscle and rectus abdorminalis muscle, were measured by examining the root mean square (RMS) of the surface EMG to investigate the impact of changes in the adjusted sitting posture of each subject. However, the RMS of pectoralis major muscle showed a significant differences (p<.05). Secondly, there were no significant differences in , Jitter and Shimmer between pre and post posture change, but there was a significant difference in NHR (p<.05). The data were collected in each individual; once prior and once after the sitting posture change. The data were analyzed by Wilcoxon signed ranks-test using SPSS version 14.0 for Windows. The findings of this study were as follows; Firstly, the RMS of upper trapezius and rectus abdorminalis muscle were not significant different between pre and post sitting posture changes. From the result, it is concluded that changes in the adjusted sitting posture decreases the abnormal respiratory patterns in the children with spastic cerebral palsy which is characterized by the hyperactivity of the respiratory muscles in breathing. Also, there is increased on the voice qualities in children with spastic cerebral palsy.