基于WVD改进算法的跳频信号参数估计

针对平滑伪维格纳分布（SPWVD：SmooLhedPseudoWigner—VilleDistribution）在跳频信号参数估计中存在的分辨率下降和运算量过大等问题,提出基于sTfTr（Short—TimeFourierTransform）与WVD（Wigner—VilleDistribution）的联合算法（STFT—WVD）,实现了跳频周期、跳变时刻和跳频频率等参数的盲估计。在参数估计的过程中,STFT—WVD算法有效地抑制了WVD的交叉干扰项,保持了WVD较高的时频分辨率,在运算量上和WVD相近,没有增加运算的复杂程度。仿真实验证明,STFT—WVD比SPWVD具有更好的整体性能,在信噪比优于-1dB时,能得到更为精准的估计值。     

基于标定的任意半径柱面上2维条形码畸变校正

摘 要：二维条码在直接零件标识技术中应用越来越广泛,但存在标刻在柱形零件上的二维条码由于扭曲形变而无法识读的问题。为了校正这种畸变,论文分析了柱面二维条码的畸变形成原理,然后基于标定的机器视觉装置与透视投影原理建立柱面上二维条码畸变校正模型,最后通过图像信息估计出柱形零件半径参数信息,并代入畸变校正模型得到最终的校正结果。实验结果表明,该方法能够较好的校正自由半径柱面上二维条码的扭曲畸变。     

Compatibility and thermal properties of poly(acrylonitrile–butadiene–styrene) copolymer blends with poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The mechanical and heat‐resistant properties of acrylonitrile–butadiene–styrene (ABS) binary and ternary blends were investigated. The relationship of compatibility and properties was discussed. The results show that poly(methyl methacrylate) (PMMA) and styrene–maleic anhydride (SMA) can improve the thermal properties of conventional ABS. The Izod impact property of ABS/PMMA blends increases significantly with the addition of PMMA, whereas that of ABS/SMA blends decreases significantly with the addition of SMA. Blends mixed with high‐viscosity PMMA are characterized by higher heat‐distortion temperature (HDT), and their heat resistance is similar to that of blends mixed with SMA. For high‐viscosity PMMA, from 10 to 20%, it is clear that blends appear at the brittle–ductile transition, which is related to the compatibility of the two phases. TEM micrographs show low‐content and high‐viscosity PMMA in large, abnormally shaped forms in the matrix. Compatibility between PMMA and ABS is dependent on both the amount and the viscosity of PMMA. When the amount of high‐viscosity PMMA varied from 10 to 20 wt %, the morphology of the ABS binary blends varied from poor to satisfactory compatibility. As the viscosity of PMMA decreases, the critical amount of PMMA needed for the compatibility of the two phases also decreases. SMA, as a compatibilizer, improved the interfacial adhesiveness of ABS and PMMA, which results in PMMA having good dispersion in the matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2652–2660, 2002     

Avoidance response of juvenile Pacific treefrogs to chemical cues of introduced predatory bullfrogs

Bullfrogs (Rana catesbeiana), native to eastern North America, were introduced into Oregon in the 1930's. Bullfrogs are highly efficient predators that are known to eat a variety of prey including other amphibians. In laboratory experiments, we investigated whether juvenile Pacific treefrogs (Hyla regilla) recognize adult bullfrogs as a predatory threat. The ability of prey animals to acquire recognition of an introduced predator has important implications for survival of the prey. We found that treefrogs from a population that co-occurred with bullfrogs showed a strong avoidance of chemical cues of bullfrogs. In contrast, treefrogs from a population that did not co-occur with bullfrogs, did not respond to the bullfrog cues. Additional experiments showed that both populations of treefrogs use chemical cues to mediate predation risk. Treefrogs from both populations avoided chemical alarm cues from injured conspecifics.     

DEAR-MULSEMEDIA: Dataset for emotion analysis and recognition in response to multiple sensorial media

Traditionally, emotion recognition is performed in response to stimuli that engage either one (vision: image or hearing: audio) or two (vision and hearing: video) human senses. An immersive environment can be generated by engaging more than two human senses while interacting with multimedia content and is known as MULtiple SEnsorial media (mulsemedia). This study aims to create a new dataset of multimodal physiological signals to recognize emotions in response to such content. To this end, four multimedia clips are selected and synchronized with fan, heater, olfaction dispenser, and haptic vest to augment cold air, hot air, olfaction, and haptic effects respectively. Furthermore, physiological responses including electroencephalography (EEG), galvanic skin response (GSR), and photoplethysmography (PPG) are observed to analyze human emotional responses while experiencing mulsemedia content. A t-test applied using arousal and valence scores show that engaging more than two human senses evokes significantly different emotions. Statistical tests on EEG, GSR, and PPG responses also show a significant difference between multimedia and mulsemedia content. Classification accuracy of 85.18% and 76.54% is achieved for valence and arousal, respectively, using K-nearest neighbor classifier and feature-level fusion strategy.     

基于CITAF-HAF的立方调频信号参数估计

针对立方调频（Cubic Frequency Modulated,CFM）信号的参数估计问题,提出了一种基于高阶模糊函数（High order Ambiguity Function,HAF）和相参积累三阶自相关函数（Coherently Integrated Trilinear Autocorrelation Function,CITAF）的参数估计方法。利用HAF将立方相位信号降阶为二次调频（Quadratic Frequency Modulated,QFM）信号,再利用CITAF完成参数估计。由于CITAF能够在时域和时延域完成信号能量的二维相参积累,其实现过程利用复乘、傅里叶变换和加法操作即可完成,因此该方法能够提高参数估计的分辨率和抗噪声干扰能力,并保持较低的计算量。实验结果证实了该算法的有效性和性能上的优越性。     

基于稀疏重构的窄带弱信号时延估计算法

提出了一种基于稀疏重构的窄带弱信号时延估计算法.利用信号的互相关谱构造数据矩阵,然后建立时延参数的冗余字典,最后通过矩阵奇异值分解在信号子空间中利用正交匹配追踪算法得到高精度时延估计.理论分析和仿真实验验证了算法的正确性和有效性.相比于传统方法,该算法可将窄带弱信号时延估计精度提高约1倍.     

Low Distortion Quick Response Noise Filter Realized with Average Peaks Method

The filter proposed in this paper is expected to reduce noise whose frequency is lower than higher order harmonics of real signals. It is based on the distributive characteristics of noise, and uses analog circuits to select the high peak and low peak of the input signal and applies their average in order to reduce random noise. So it has no cutoff frequency and higher order harmonics of real signals are remained. As a result, it gives an instant response to changes in input signals and retains the integrity of real signals. Furthermore, it has only a small phase delay. The simulation results of slew rate, phase delay and spectral analysis under MULTISIM indicate that the quick response noise filter achieves a high slew rate of 472 V/ms and the phase shift is nearly zero. By having it used in a color tester design, it is also demonstrated that the proposed filter effectively reduces noise and remains signal integrity. With the filter’s help, the relative standard deviation of the spectrograph decreases from 1% to 0.22%, indicating better stability.     

一种用于多相编码信号参数估计的MST改进算法

多相编码信号是一类典型的低截获概率雷达信号,具有类线性调频的特点,其参数估计问题是当前电子侦察信号分析的研究热点.该文基于匹配信号变换理论,推导了截获信号与匹配信号变换时间函数不匹配时的调频斜率估计性能.针对多相编码信号的特点,以及实际电子侦察环境中截获信号存在载频估计误差、信号不完整、噪声干扰等问题,提出了一种基于二维搜索的改进匹配信号变换算法.仿真实验以P4码为例,分析了提出算法的参数估计性能.实验结果表明,提出算法能够较好地解决信号失配问题,估计精度高、速度快,具有较大的工程应用价值.     

基于BCJR的GMSK混合信号分离算法研究

针对GMSK混合信号单通道盲分离问题,提出将BCJR算法用于GMSK混合信号分离。根据GMSK信号连续相位的特点,通过建立混合信号模型的有限状态马尔科夫性,推导了利用BCJR算法实现GMSK混合信号分离过程。在不增加算法复杂度的情况下,选择每个时刻后验概率的多个极大值对分离算法进行了改进。仿真实验表明,在调制参数比较相近的条件下,即使相对幅度、相对相位、相对时延估计不够准确,改进算法仍能取得较好的分离效果。