Muscle oxygenation measurement in humans by noninvasive optical spectroscopy and Locally Weighted Regression

We have developed a method to make real-time, continuous, noninvasive measurements of muscle oxygenation (Mox) from the surface of the skin. A key development was measurement in both the visible and near infrared (NIR) regions. Measurement of both oxygenated and deoxygenated myoglobin and hemoglobin resulted in a more accurate measurement of Mox than could be achieved with measurement of only the deoxygenated components, as in traditional near-infrared spectroscopy (NIRS). Using the second derivative with respect to wavelength reduced the effects of scattering on the spectra and also made oxygenated and deoxygenated forms more distinguishable from each other. Selecting spectral bands where oxygenated and deoxygenated forms absorb filtered out noise and spectral features unrelated to Mox. NIR and visible bands were scaled relative to each other in order to correct for errors introduced by normalization. Multivariate Curve Resolution (MCR) was used to estimate Mox from spectra within each data set collected from healthy subjects. A Locally Weighted Regression (LWR) model was built from calibration set spectra and associated Mox values from 20 subjects using 2562 spectra. LWR and Partial Least Squares (PLS) allow accurate measurement of Mox despite variations in skin pigment or fat layer thickness in different subjects. The method estimated Mox in five healthy subjects with an RMSE of 5.4%.     

基于改进阈值消噪算法的小波包降噪

小波变换是一种把时间和频率结合起来的时频分析方法,D.L.Dohono在小波变换的基础上提出了小波软、硬阈值消噪法,此方法简单有效,得到了广泛的重视和研究。在经典的小波软、硬阈值消噪方法的基础上,提出了一种基于小波包分析的改进方法。Matlab仿真结果表明,此法同时克服了软、硬阈值方法的缺点,而且其消噪效果比小波消噪方法要好。     

Development of models for prediction of the antioxidant activity of derivatives of natural compounds

Antioxidants are important for maintaining the appropriate balance between oxidizing and reducing species in the body and thus preventing oxidative stress. Many natural compounds are being screened for their possible antioxidant activity. It was found that a mushroom pigment Norbadione A, which is a pulvinic acid derivative, shows an antioxidant activity; the same was found for other pulvinic acid derivatives and structurally related coumarines. Based on the results of in vitro studies performed on these compounds as a part of this study quantitative structure–activity relationship (QSAR) predictive models were constructed using multiple linear regression, counter-propagation artificial neural networks and support vector regression (SVR). The models have been developed in accordance with current QSAR guidelines, including the assessment of the models applicability domains. A new approach for the graphical evaluation of the applicability domain for SVR models is suggested. The developed models show sufficient predictive abilities for the screening of virtual libraries for new potential antioxidants.     

光电侦察系统目标定位精度评价指标研究

鉴于光电侦察定位系统的设计、验收、订购阶段均涉及对系统精度的评价,指出影响光电侦察系统目标定位精度的评价指标。研究了均方根误差、平均误差及置信概率区间方法的计算原则及使用条件,给出光电侦察系统目标定位精度的评价指标,并提出设计阶段的精度预估方法、验收阶段的精度评定方法以及设备采购阶段的性能优选方法。规范了光电侦察系统的定位精度预估、验收以及订购。     

光纤传感信号中小波去噪的最优分解尺度确定方法

小波分解尺度选择是小波去噪中的关键,分解尺度 过大或过小,都会直接影响传感信号去噪的质量。本文 通过分析常规的分解尺度选择方法,引用指标融合算法原理从图形和统计两个角度出发选用 信噪比(SNR)、均方 根误差(RMSE)、平滑度r以及信号偏差(BIAS)4项评价指标融合 成一项指标,采用指数函数对融合指标进行拟合,并提出 一种拐点判别公式来准确判定最优分解尺度。然后,采用所提方法,结合改进的阈值和阈值 函数,对实验 信号进行最佳分解尺度寻优,实验验证结果表明,本文方法所确定的最优分解尺度对应的中 心波长反射率与实际值相符,因此能够获得更优的去噪效果。     

精确自动识别莫尔条纹方向角的算法

由于常规莫尔条纹计算方法难以满足速度和精度的要求,本文提出一种快速准确求取莫尔条纹方向角的算法。该算法首先根据直线方向与莫尔条纹方向越接近则均方误差值越小的原理,初步求得莫尔方向角α,之后采用Mean-Shift算法在方向角α附近进一步精确求取莫尔条纹方向角。实验结果表明：采用误差评判指标测试对比度满足5.4%时,提出的算法所获得的莫尔条纹方向角计算精度达到29＇,同时计算速度相对频域处理方法大幅提高,计算时间为15 ms,满足算法处理速度对实时性的要求。     

Modeling of In2O3-10 wt% ZnO thin film properties for transparent conductive oxide using neural networks

Effects of deposition process parameters on the deposition rate and the electrical properties of In₂O₃–10 wt% ZnO (IZO) thin films were modeled and analyzed by using the error back-propagation neural networks (BPNN). Output models were represented by response surface plots and the fitness of models was estimated by calculating the root mean square error (RMSE). The deposition rate of IZO thin films is affected by the RF power and the substrate temperature. The electrical properties of the IZO thin films are mainly controlled by O₂ ratio and the substrate temperature. The predicted output characteristics by BPNN can sufficiently explain the mechanism of IZO deposition process. Thus, neural network models can provide the reliable explanation of IZO film deposition.     

激光诱导击穿光谱技术对土壤中重金属元素Cr的定量分析

为促进LIBS技术在土壤微量重金属元素检测中的应用,提高特征谱线的光谱强度和信背比,对实验参数进行优化,并对Cr元素进行分析.首先对激光器激发能量、样品距透镜距离和光谱仪采集延时等实验参数进行优化.对比激光器能量从60 m J到110 m J的谱线强度和信背比,当选用90 m J的激发能量时可以得到最佳实验结果.其次,...     

DWT-iPLS在烃源岩漫反射光谱数据处理中的应用

红外漫反射光谱技术被广泛地应用于粉末样品的定性、定量测量中。但是由于粉末样品自身的特点,颗粒度、密度、表面粗糙程度等几何参数的影响,使得漫反射光谱数据的信噪比很低、背景干扰很大。因此需要一种有效的方法对漫反射光谱数据进行预处理来提高信噪比,消除背景干扰。文章采用了离散小波变换对红外漫反射光谱进行了预处理,有效地消除了光谱中的高频噪声和低频背景的干扰,并结合iPLS(间隔偏最小二乘回归)方法进行线性回归分析,建立了用于复杂样品体系组分分析的建模方法(DWT-iPLS)。并以烃源岩的红外漫反射光谱为例,将DWT-iPLS应用于数据的预处理及建立数学模型,其结果与未用DWT预处理的方法相比较,准确度有明显的提高,证明了此方法是一种快速有效的定量分析的建模方法。     

基于相频空间稀疏性快速估计LED灯点参数

在LED照明应用中,为了能够获得、记录或重现特定的照明模式,要求检测装置可以测量出每个LED灯点照明空间中某一位置时的独立"贡献量",这可以归结为对驱动LED工作的脉宽调制波形(PWM)的参数(振幅、频率偏移量、相位延迟)估计问题。为了达到参数估计的目的,首先将频率偏移空间和相位延迟空间离散化成二维网状格点,然后根据检测装置测量得到的数据在格点空间具有稀疏性的特点建立稀疏模型。接着,采用正交匹配追踪算法(OMP),用很少的采样点快速有效地重建未知参数。最后,为了有效抑制估计误差,本文使用了一种逐级迭代细分网格的技术作为前面稀疏模型的补充。实验结果表明,本文方法仅使用相当于奈奎斯特采样定理要求的27.5%的少量采样点就完成了快速估计的任务,同时,不同噪声条件下的对比试验说明算法在信噪比大于20dB时鲁棒性较好。