On the existence of higher order polynomial lattices based on a generalized figure of merit

Dick and Pillichshammer recently introduced generalized rank-1 polynomial lattices which can be viewed as digital (t,α,β,n×m,s)-nets as introduced by the first author. In this work we generalize the figure of merit of rank-1 polynomial lattices such that the new figure of merit _α is related to the t-value, when one views the rank-1 polynomial lattice as a digital (t,α,β,n×m,s)-net. Then we show the existence of rank-1 polynomial lattices for which the generalized figure of merit _α satisfies a certain condition. We present some numerical results comparing the corresponding t-value to known explicit constructions.     

A new strategy for fast radiofrequency CW EPR imaging: direct detection with rapid scan and rotating gradients

Rapid field scan on the order of T/s using high frequency sinusoidal or triangular sweep fields superimposed on the main Zeeman field, was used for direct detection of signals without low-frequency field modulation. Simultaneous application of space-encoding rotating field gradients have been employed to perform fast CW EPR imaging using direct detection that could, in principle, approach the speed of pulsed FT EPR imaging. The method takes advantage of the well-known rapid-scan strategy in CW NMR and EPR that allows arbitrarily fast field sweep and the simultaneous application of spinning gradients that allows fast spatial encoding. This leads to fast functional EPR imaging and, depending on the spin concentration, spectrometer sensitivity and detection band width, can provide improved temporal resolution that is important to interrogate dynamics of spin perfusion, pharmacokinetics, spectral spatial imaging, dynamic oxymetry, etc.     

Image evaluation with chemometric strategies for quality control of paints

In this study a complementary analytical methodology for quality of paints evaluation was developed. Four different primers applied to steel substrates and submitted to accelerated laboratory and outdoor exposure tests were taken into account. After this, digitalized images were obtained from these samples using a conventional scanner. The images were converted in gray color scale histograms, the resulting data were organized into a matrix form and analyzed with the help of principal component analysis (PCA) and hierarchical cluster analysis (HCA). It was possible to identify the best primers performance avoiding subjective interpretation.     

Possibility to break through limitation of measurement range in dual-wavelength digital holography

By using the beat frequency technique, the dual-wavelength digital holography(DWDH) can greatly increase the measurement range of the system. However, the beat frequency technique has a limitation in measurement range. The measurement range is not larger than a synthetic wavelength. Here, to break through this limitation, we propose a novel DWDH method based on the constrained underdetermined equations, which consists of three parts:(i) prove that the constrained underdetermined equation has a unique integer solution,(ii) design an algorithm to search for the unique integer solution,(iii) introduce a third wavelength into the DWDH system, and design a corresponding algorithm to enhance the anti-noise performance of DWDH. As far as we know, it is the first time that we have discovered that the problem of DWDH can belong in a problem of contained underdetermined equations, and it is also the first time that we have given the mathematical proof for breaking through the limitation of the measurement range. A series of results is shown to test the theory and the corresponding algorithms. More importantly, since the principle of proposed DWDH is based on basic mathematical principles, it can be further extended to various fields, such as dual-wavelength microwave imaging and dual-wavelength coherent diffraction imaging.     

计算机化的数字交流伏安法

电化学交流阻抗技术在电化学理论研究和测量上是十分有用的方法。Smith等人讨论了计算机辅助的交流极谱方法中许多人们感兴趣的问题,并曾使用快速富里叶变换技术同时检测多种谐波成分。近来,Bond进行了微处理器辅助的数字交流极谱仪的研究。迄今,计算机化的交流伏安仪方面的研究国内尚未见报道。本文在前文多功能仪器系统的基础上进一步建立了阶梯扫描交流伏安法并应用于实验研究,获得了满意的结果。     

中位数高保真数字滤波算法

提出了一种采用中位数的滑动窗口滤波方法。所设置的窗口宽度为2m+1个数据点,使宽度大于m个数据点的峰被视为信号而无失真地保留,使宽度小于或等于m个数据点的峰被视为噪声而完全滤除。中位数法较之常用的加权和法具有滤波效果好、信号畸变小等优点。此法能保证谱峰高度和谱峰位置这两个重要参数不发生变化,故非常适宜用于仪器化学分析信号的滤波。     

在线红外水分仪的一种校准方法

用动态被测物料作为校准介质,再用重量法对选取的样品定值,以此校准在线红外水分仪。     

应用数字傅里叶滤波方法提高近红外光谱多元校正模型稳健性的研究

在近红外光谱多元校正方法实际应用中,经常遇到这样的情况,近红外光谱校正模型仅适用于建模时的测量条件,而在测量条件稍有变化时就无法实现样品的准确预测。文章主要研究采用数字傅里叶滤波预处理方法提高近红外光谱多元校正模型稳健性。文章将数字傅里叶滤波预处理方法应用于葡萄糖水溶液的温度实验,实验1和实验2分别在恒温25 ℃和恒温30 ℃进行光谱测量;实验3在未控温的室内环境下进行光谱测量。采用实验1和实验2的样品作为训练集进行模型训练和优化,模型建立完毕之后,采用实验3的样品作为验证集进行模型预测能力评价。结果表明,如果训练集样品未经过预处理而直接建立偏最小二乘(PLS)多元校正模型,则验证集样品均方根预测误差(RMSEP)为664.47 mg·dL-1。而训练集和验证集样品经过傅里叶滤波预处理之后分别进行PLS建模和预测,验证集样品均方根预测误差(RMSEP)降低为58.43 mg·dL-1,样品预测值与参考值的相关性也得到提高。可见,采用数字傅里叶滤波预处理方法可以提高多元校正模型的稳健性。     

MPEG-2先进音频编码(AAC)的研究和软件仿真

ＭＰＥＧ－２ＡＡＣ是ＩＳＯ／ＩＥＣ ＭＰＥＧ组织继 ＭＰＥＧ－１、ＭＰＥＧ－２音频编解码标准后,制定 的最新国际标准（ＩＳＯ／ＩＥＣ １３８１８－７）,在６４ｋｂｐｓ／每声道低码率时能提供全透明音质。本文对其编 解码算法进行了简要介绍。论文作者对ＭＰＥＧ－２ＡＡＣ进行了软件仿真,文中介绍了仿真结果,仿 真时对ＡＡＣ标准所附编码范例中的一些不妥之处,作了改进,文中列举了６方面的修正。     

超短脉冲激光通过高散射介质的电子学全息成像技术研究

根据超短脉冲激光透过高散射介质成像的电子全息原理,建立了一套完整的适用于透过高用射介质成像的电子学全息系统。采用该系统,透过厚度为１２ｍｍ,体积百分比为５％的鲜奶和水的混合散射液体,对直径为０．６５ｍｍ的金属丝实现了成像。