衍射光栅刻划机精密工作台定位特征识别试验研究

针对机械式衍射光栅刻划机精密定位工作台定位过程中产生的振动信号特性与光学性能指标（杂散光强度和波前质量）之间的关系,提出利用改进的Hilbert-Huang变换(HHT)获得的时频谱和边际谱对超精密工作台精定位特性进行研究。首先,给出了基于固有模态函数（IMF）筛选和瞬时频率差分求解的HHT信号处理算法。然后,设计了光学测量实验获得工作台50nm定位信号。最后,完成精密定位信号的特征提取和振动测试验证。结果表明:利用改进的HHT可以精确地完成精密定位信号的特征提取,从而为在衍射光栅的制造工艺中从根源上降低衍射光栅的杂散光强度和提高波前质量提供依据。     

How the online social networks are used: dialogues-based structure of MySpace

Quantitative study of collective dynamics in online social networks is a new challenge based on the abundance of empirical data. Conclusions, however, may depend on factors such as user''s psychology profiles and their reasons to use the online contacts. In this study, we have compiled and analysed two datasets from MySpace. The data contain networked dialogues occurring within a specified time depth, high temporal resolution and texts of messages, in which the emotion valence is assessed by using the SentiStrength classifier. Performing a comprehensive analysis, we obtain three groups of results: dynamic topology of the dialogues-based networks have a characteristic structure with Zipf''s distribution of communities, low link reciprocity and disassortative correlations. Overlaps supporting ‘weak-ties’ hypothesis are found to follow the laws recently conjectured for online games. Long-range temporal correlations and persistent fluctuations occur in the time series of messages carrying positive (negative) emotion; patterns of user communications have dominant positive emotion (attractiveness) and strong impact of circadian cycles and interactivity times longer than 1 day. Taken together, these results give a new insight into the functioning of online social networks and unveil the importance of the amount of information and emotion that is communicated along the social links. All data used in this study are fully anonymized.     

Characterization and authentication of a novel vegetable source of omega-3 fatty acids,sacha inchi (Plukenetia volubilis L.) oil

Consumption of omega-3 fatty acids (ω-3’s), whether from fish oils, flax or supplements, can protect against cardiovascular disease. Finding plant-based sources of the essential ω-3’s could provide a sustainable, renewable and inexpensive source of ω-3’s, compared to fish oils. Our objective was to develop a rapid test to characterize and detect adulteration in sacha inchi oils, a Peruvian seed containing higher levels of ω-3’s in comparison to other oleaginous seeds. A temperature-controlled ZnSe ATR mid-infrared benchtop and diamond ATR mid-infrared portable handheld spectrometers were used to characterize sacha inchi oil and evaluate its oxidative stability compared to commercial oils. A soft independent model of class analogy (SIMCA) and partial least squares regression (PLSR) analyzed the spectral data. Fatty acid profiles showed that sacha inchi oil (44% linolenic acid) had levels of PUFA similar to those of flax oils. PLSR showed good correlation coefficients (R² > 0.9) between reference tests and spectra from infrared devices, allowing for rapid determination of fatty acid composition and prediction of oxidative stability. Oils formed distinct clusters, allowing the evaluation of commercial sacha inchi oils from Peruvian markets and showed some prevalence of adulteration. Determining oil adulteration and quality parameters, by using the ATR-MIR portable handheld spectrometer, allowed for portability and ease-of-use, making it a great alternative to traditional testing methods.     

动物性食品中胆固醇氧化产物的研究进展

动物性食品中的胆固醇氧化产物(Cholesterol Oxidation Products,COPs)的健康效应受到广泛关注。其水平在新鲜动物性食材中均很低,但在储藏加工和家庭烹调中可能有显著增加。文章介绍了水产品、畜产品、蛋制品及乳制品4类食品中影响胆固醇氧化产物形成的因素。研究表明长时间储藏、高温、非适宜的水分活度、与光线和氧气接触等因素均会促进胆固醇氧化产物的形成。烹调中加入油脂的饱和程度和所含抗氧化物质也影响动物性食物烹调后COPs的形成。加入适量的天然抗氧化物质可能有利于减少COPs的生成。     

进出口动物源性食品中志贺氏菌检验方法优化

为建立进出口动物源性食品中志贺氏菌检验方法,从检测条件入手,通过增菌方式、分离培养基特异性和生化鉴定优化方法,以不同种类食品检测和不同实验室检测验证方法。确定的检测条件为志贺氏菌增菌液中(41.5±1)℃厌氧培养16～20h作为志贺氏菌检测的增菌方式;在分离上,同时使用MAC、XLD和HE三种平板,以提高志贺氏菌的检出率;选择了微量生化管和API20E对志贺氏菌和其他肠杆菌进行了生化鉴定和比较,效果明显。以此方法检测人工污染食品均检出志贺氏菌,各实验室也均检出志贺氏菌。     

基于Freeman改进准则的输电线断股识别

为了解决输电线断股故障识别问题,将图像处理识别技术应用到电力系统故障检测中,在Freeman检测直线准则的基础上进行了改进,提出了一种简单高效的检测输电线断股故障的算法。该算法根据输电线端点特征识别出端点,并通过端点对输电线图像进行水平校正,再根据输电线断股故障的特征提出用Freeman链码标记异常处的一些相关的点,计算这些点与输电线边缘之间的垂直距离,以此距离来判断输电线是否存在断股故障。理论分析和实验结果证明,该算法可行、有效、识别率高。     

智能微波开关微波信号识别方法

智能微波开关是采用波束障碍原理,测量物位的智能传感器。为了更加可靠地检测微波信号以消除干扰,其发射和接收采用了调制和解调的方法,解调电路将检波到的微波信号解调,得到微波幅值信号、低频信号、高频信号。文中用单片机MSP430F149的模数转换模块测量微波幅值信号,用定时器的比较/捕获模块测量低频信号和高频信号。测量得到的微波幅值、低频频率、高频频率分别与标称值进行二值比较,3个比较结果表决判断微波信号的畅通/阻断,在延时窗口内为智能微波开关的输出提供依据。实验结果表明该方法能准确地识别出微波信号,系统可以安全可靠地工作。     

基于太赫兹光谱技术的抗生素类药物检测研究

本文利用太赫兹时域光谱技术在室温下对几种在临床和人们日常生活中常用的抗生素类药物阿莫西林、青霉素钠、头孢氢氨苄和头孢拉丁进行了光谱测量,获得了四种物质在0.2-1.7THz波段的吸收谱和折射谱,发现这四种抗生素类药物在太赫兹波段均存在明显的特征吸收峰,可作为其在太赫兹波段的指纹谱用于药物分子识别。本研究表明,太赫兹时域光谱技术在常用抗生素类药物的物质鉴别及药品质量检查方面有着广泛的应用前景。     

Partial discharge recognition system for current transformer using neural network and 2D wavelet transform

In this paper, a neural network and two‐dimensional (2D) wavelet transform are applied to recognize partial discharge (PD) patterns on current transformers (CTs). To avoid the discrepancy between simulated results and real experimental data, we adopted seven cast‐resin CTs that were purposely fabricated with various insulation defects as the PD patterns collected samples to actually emulate the various defects incurred often during their production. All measurements are taken in a shielded lab; the commercial TE571 PD detector is adopted to measure PD patterns to ensure the reliability of the PD signals. Next, we extract the patterns' features via a 2D wavelet transform and use the features as the training set of a backpropagation neural network (BNN) to construct the recognition system for CTs' PD patterns. Finally, we add random noises to the measured PD signals to emulate the field diagnosis under a high‐noise environment. The study results indicate that, under a simulated noise magnitude of 30 pC, the recognition rate of the proposed system still can reach around 80%, signifying a great potential in applying the proposed recognition system in field measurements in the future. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.