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基于模块组合式阵列的三维漏磁检测系统 总被引:1,自引:0,他引:1
为了研究阵列传感器在试件上大面积扫查检测的问题,研制了一种基于模块组合式AMR磁阻传感器阵列的三维弱磁信号检测系统。检测系统由结构相同的标准模块组成,每个模块可同时采集X、Y、Z三个方向的磁信号。对含预制裂纹的16MnR钢平板试件进行检测实验,并采集试件表面的磁信号。结果表明:可重配置式三维阵列探头对表面裂纹具有较高的灵敏度,并对亚表面裂纹具有一定的辨识能力;三维阵列探头可有效扩大检测范围,并通过对磁阵列信号成像可得到裂纹的形状及所处的位置信息。 相似文献
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More and more conversation recordings from phone calls are used as forensic evidence. To decide whether an unknown speech recording comes from mobile phone or not becomes an important issue in digital audio forensics. The communicating conversation recorded by mobile phones is encoded by Adaptive Multi-Rate (AMR) audio codec, which was adopted as the standard speech codec by 3GPP and widely used in GSM and UMTS. Therefore, AMR decompressed audio detection can be used to identify the source of the digital audio recording. Furthermore, it is helpful to locate the forgery position of the splicing AMR decompressed audio for forensic purposes. In this article, we focus on the identification of AMR decompressed audio, namely, given the waveform of an audio, we wish to identify whether it has been previously compressed by AMR codec or not. The artifacts introduced by the AMR codec will help to detect the source of the recordings. Based on our analysis, we find that the sample repetition rate of the AMR decompressed waveform is significantly greater than the regular waveform. Therefore, we employ the sample repetition rate as a feature to identify the AMR decompressed audio. The experimental results show that this feature is robust and effective. 相似文献
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A system modeling approach for predicting the performance of active magnetic regenerators using a one-phase approximation is presented. The approach is described for an arbitrary AMR device independent of the magnetic refrigerant, thermal losses or magnetic waveform. A general expression for magnetic work is derived which can be used for cycles where the low-field intensity is not zero. Additionally, a means of treating the varying magnetic field waveform as a single high and low field is described. The model is applied to a permanent magnet magnetic refrigerator using water–glycol as the heat transfer fluid. Simulated results are compared to experimental data which vary by heat load, frequency and utilization. A sensitivity analysis is performed using utilization, adiabatic temperature change, effective conductivity and particle size as independent variables. Comparisons to experimental data show that reducing the calculated magnetocaloric effect by 25% provides good agreement between simulations and experimental results. 相似文献
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Nowadays, the development of classification algorithms gives the ability to improve Automatic Modulation Recognition (AMR) effectively. This paper presents a novel modulation recognition algorithm based on clustering approach. Generally, we aim to distinguish multicarrier modulation OFDM from single-carrier modulations. In this regard, two statistics of the amplitude of the received signal are calculated at the output of a quadrature mixer as key features. The extracted features of training data points are submitted to the clustering algorithm, then, centroids for single-carrier and multicarrier modulations are assessed. Afterwards, each point of testing dataset is dedicated to its nearest centroid based on Euclidian distance and the recognition is accomplished. Simulation results demonstrate that the algorithm is beneficial in a wide range from low to high SNRs. 相似文献
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本文根据AMR技术在GSM系统中物理层信道卷积编码规范,提出了一种可控制信道差错,降低工程实现难度的译码MATLAB仿真方案。结果表明,通过该仿真方案适合AMR语音业务信道卷积码的译码。 相似文献
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主要探讨的是根据AMR技术来尝试使用不同的语音编码方式来提升MOS值,使得用户的通话质量得到提高。采用PESQ听觉模型的语音测评方法,能够客观地评价网络质量和音质。AMR技术在MOS网络优化中提高PESQ指标对运营商提高市场竞争力具有重要意义。 相似文献
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通过对拖曳式有源雷达诱饵干扰的分析,得到了平衡状态下对导引头测角值进行数据积累并且取均值后,导引头将指向大功率辐射源的结论。在诱饵信号从功率上压制栽机回波信号的前提下,对导引头处于平衡状态时的测量角公式进行数学推导。结果表明:可由导引头处理时间内任意两次测角值及其对应的和支路振幅比求得载机、诱饵和导弹三者形成的夹角的角平分线方向,从而间接求得小功率辐射源(载机)的角度。最后,结合比例导引规律,通过飞行弹道仿真验证了雷达型空空导弹应用上述方法可以获得准确的目标角度,进而导引导弹准确命中目标。 相似文献
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