Diffusion-limited energy transfer from Tb3+ → Nd3+ and Tb3+ → Ho3+ in DMSO

The energy transfer phenomenon has been studied from Tb³⁺ → Nd³⁺ and Tb³⁺ → Ho³⁺ in DMSO. A diffusion limited dipole-dipole mechanism of energy transfer is suggested for both systems. At high acceptor concentrations, P_da depends linearly on C² consistent with the Fong and Diestler theory of energy transfer. However, at low acceptor concentrations the observations of time evolutions of Tb³⁺ luminescence decay following flash excitation has enabled us to examine diffusion limited energy transfer from Tb³⁺ to Nd³⁺ and Tb³⁺ to Ho³⁺ in DMSO.     

啤酒酵母中β-(1-3)葡聚糖的提取及其性能分析

本文采用Sevage脱蛋白法、酸溶液浸提法、碱溶液浸提法对啤酒废酵母细胞壁中的β-(1-3)葡聚糖作了提取试验,并对所获多糖进行生化特性分析,阐述了碱溶液浸提法是从啤酒酵母中回收高质量β-(1-3)葡聚糖的理想途径．     

博落回生物碱的提取及分离工艺

采用正交实验方法研究博落回生物碱的盐酸提取工艺。结果表明：盐酸法提取的最佳工艺条件为：1．5％盐酸,固液比1：18,85℃提取3次,每次2h,提取率达到80．1％,与文献报道的醇提法相比其提取率提高20％左右。然后采用柱层析方法分离得到高纯度的血根碱和白屈菜红碱,并建立了一种HPLC法测定博落回中生物碱含量的方法。     

吸收峰混叠的太赫兹光谱区间组合特征提取算法

太赫兹光谱是物质识别的前沿方法之一。由于不同物质的分子组成或结构各异,许多物质的太赫兹吸收谱会在特定频率上出现吸收峰,可以作为混合物成分检测的重要特征。有效准确地提取这些吸收峰的参数,是提高识别率的关键。多峰拟合算法将光谱曲线拟合成若干个标准峰函数之和,能够同时提取到吸收峰的频率、峰高、峰宽等信息。但是该算法以寻峰算法结果为基础确定吸收峰的大致位置和数量,寻峰结果不一定是最优的拟合结果,而且很难准确识别定位混叠状态的吸收峰。为了提高混叠光谱中吸收峰的识别定位精度,提出以大幅度平滑后的曲线波谷为分界点,将预处理后的光谱分成若干个子区间。然后将子区间组合起来进行多峰拟合,通过遗传算法得到最优的拟合子区间组合和吸收峰频率近似值,拟合时每个子区间中通过峰数递增最优化方法确定拟合的吸收峰数,最后微调优化得到最优的吸收峰频率、峰高值。为了实现物质的识别,通过密度聚类算法得到同一类纯净物在多次测量中的共同吸收峰,以此作为标准数据,通过提出的基于吸收峰特征的光谱匹配算法实现了纯净物和不同含量混合物的快速识别。对10类纯净物的实际光谱数据进行拟合聚类,得到其吸收峰参数,结果与太赫兹光谱数据库一致。通过识别算法对纯净物测试集进行识别的识别率为100%,证明了特征提取和物质识别算法的有效性。对于含有混叠峰的混合物光谱,二阶导数法对葡萄糖-乳糖混合物光谱中被掩盖吸收峰(1.280 THz)的识别率仅为70%,提取到的频率平均值为1.316 THz;而该算法提高识别率至95%,频率平均值为1.281 THz,该算法提高了对混叠峰的分辨能力,能够精确定位混叠峰。对10类纯净物构成的6类不同程度混叠的二元混合物前二、三识别率分别达到90.8%和98.3%,提取到的特征能够有效应用于混合物的成分检测。该算法能够以纯净物数据为标准数据实现成分各异的混合物成分检测,对于太赫兹光谱混合物成分检测有重要意义。     

FFT动态相位重建算法的滤波窗影响分析

为了优化相位重建算法,针对波面干涉图的傅里叶频谱,分析了不同滤波窗口的分布特征和频谱响应,通过计算机仿真和实验测试,确定了FFT动态相位重建算法的最佳滤波窗口类型。其中处理仿真干涉图重建的波面与原始波面的波面峰谷值残差为0.008 5λ,波面均方根值残差为0.000 1λ;处理实验干涉图获得的波面与移相干涉测量法获得的波面峰谷值残差为0.009 3λ,波面均方根值残差为0.000 5λ。结果表明:选取Hamming窗进行滤波处理并重建的相位经拟合后得到的波面较参考波面的面形残差最小,相位重建精度优于0.01λ,可进一步应用于大口径光学元件的测量中。     

Ultrasound-assisted desolventizing of fragrant oil from red pepper seed by subcritical propane extraction

In the present study, ultrasound was used to remove the residual solvent from the fragrant oil of red pepper seed obtained by subcritical propane extraction. The physical and chemical characteristics, particularly the volatile flavor compounds present of the oil before and after ultrasound-assisted desolventizing were comprehensively analyzed to determine the effect of the desolventizing process on product quality. The results showed that the maximum loss of residual solvent was achieved at a temperature of 90 °C maintained for 70 min with ultrasound applied during the entire process. After this treatment only a small amount of solvent (2.3% based on the total residual solvent originally present) remained in the oil. Although it was hypothesized that ultrasound treatment could result in the loss of volatile components, the analytical results showed no obvious reduction in the components associated with the typical aroma of the oil. After ultrasonic treatment, the oil also had good oxidation stability and quality. Additionally, after ultrasonic desolventizing, the oil samples were more suitable for cooking because they could more effectively minimize oxidation. Thus, these results demonstrate that this new ultrasonic technique is an effective and efficient method for removing the solvent remaining in fragrant oil after subcritical propane extraction.     

An Improved Composite Multiscale Fuzzy Entropy for Feature Extraction of MI-EEG

Motor Imagery Electroencephalography (MI-EEG) has shown good prospects in neurorehabilitation, and the entropy-based nonlinear dynamic methods have been successfully applied to feature extraction of MI-EEG. Especially based on Multiscale Fuzzy Entropy (MFE), the fuzzy entropies of the τ coarse-grained sequences in τ scale are calculated and averaged to develop the Composite MFE (CMFE) with more feature information. However, the coarse-grained process fails to match the nonstationary characteristic of MI-EEG by a mean filtering algorithm. In this paper, CMFE is improved by assigning the different weight factors to the different sample points in the coarse-grained process, i.e., using the weighted mean filters instead of the original mean filters, which is conductive to signal filtering and feature extraction, and the resulting personalized Weighted CMFE (WCMFE) is more suitable to represent the nonstationary MI-EEG for different subjects. All the WCMFEs of multi-channel MI-EEG are fused in serial to construct the feature vector, which is evaluated by a back-propagation neural network. Based on a public dataset, extensive experiments are conducted, yielding a relatively higher classification accuracy by WCMFE, and the statistical significance is examined by two-sample t-test. The results suggest that WCMFE is superior to the other entropy-based and traditional feature extraction methods.     

三维显示中基于彩色叠栅条纹的视差障栅参数设计

为确定三维显示中视差障栅(PB)的最优参数,提出一种基于彩色叠栅条纹的PB参数设计方法。液晶显示器(LCD)和PB简化为相应参数的黑白光栅模型,而具有特定参数的特定辐射光栅作为周期和倾角变化的PB模型,通过序数方程和傅里叶分析方法分析特定辐射光栅和LCD单色等效黑白光栅的叠加图样,由此推断出不同PB周期的低频主导条纹频率组项,然后利用傅里叶理论的部分和提取方法(PSE)分析不同PB周期的低频主导叠栅条纹的强度轮廓,得出PB的最佳节距和相应倾斜角度。实验结果表明,所设计的PB三维显示系统没有出现降低像质的叠栅条纹,具有较好的三维显示效果。     

Small-signal modeling of GaN HEMT switch with a new intrinsic elements extraction method

A novel and accurate method is proposed to extract the intrinsic elements of the GaN high-electron-mobility transistor(HEMT) switch.The new extraction method is verified by comparing the simulated S-parameters with the measured data over the 5-40 GHz frequency range.The percentage errors E_(ij) within 3.83% show the great agreement between the simulated S-parameters and the measured data.