Development of an accurate and sensitive gas chromatographic method for the determination of acrolein content in Calvados and cider

Acrolein can be at the origin of an important organoleptic defect in beverages made from apples. Its content was investigated in freshly distilled Calvados and cider. The specificity of 3-methylbenzothiazolone hydrazine (MBTH) towards carbonyl compounds was used in order to derive acrolein in azines. Azines were separated and detected by gas chromatography coupled with a nitrogen-phosphorus Detector. Results showed that acrolein concentrations could be quickly determined in either Calvados or cider. Accuracy of quantification was better than 6% for concentrations about 1 mg/l in freshly distilled Calvados and 10% for concentrations about 10 μg/l in ciders. Acrolein content was found between 0.7 and 5.2 mg/l in samples of freshly distilled Calvados whereas it was between 7 and 15 μg/l in samples of cider. This method of quantification was applied to study disappearance kinetics of acrolein in cider. Acrolein content was found to decrease rapidly during the first hours and to change very slowly after a few days. Its behaviour during a distillation was also investigated showing that in spite of its high volatility it could also be found in the last fractions of distillation.     

Development of real-time PCR methods to quantify patulin-producing molds in food products

Patulin is a mycotoxin produced by different Penicillium and Aspergillus strains isolated from food products. To improve food safety, the presence of patulin-producing molds in foods should be quantified. In the present work, two real-time (RTi) PCR protocols based on SYBR Green and TaqMan were developed. Thirty four patulin producers and 28 non-producers strains belonging to different species usually reported in food products were used. The patulin production was tested by mycellar electrokinetic capillary electrophoresis (MECE) and high-pressure liquid chromatography-mass spectrometry (HPLC-MS). A primer pair F-idhtrb/R-idhtrb and the probe IDHprobe were designed from the isoepoxydon dehydrogenase (idh) gene, involved in patulin biosynthesis. The functionality of the developed method was demonstrated by the high linear relationship of the standard curves constructed with the idh gene copy number and Ct values for the different patulin producers tested. The ability to quantify patulin producers of the developed SYBR Green and TaqMan assays in artificially inoculated food samples was successful, with a minimum threshold of 10 conidia g⁻¹ per reaction. The developed methods quantified with high efficiency fungal load in foods. These RTi-PCR protocols, are proposed to be used to quantify patulin-producing molds in food products and to prevent patulin from entering the food chain.     

Uncertainty in microscale gas damping: Implications on dynamics of capacitive MEMS switches

Effects of uncertainties in gas damping models, geometry and mechanical properties on the dynamics of micro-electro-mechanical systems (MEMS) capacitive switch are studied. A sample of typical capacitive switches has been fabricated and characterized at Purdue University. High-fidelity simulations of gas damping on planar microbeams are developed and verified under relevant conditions. This and other gas damping models are then applied to study the dynamics of a single closing event for switches with experimentally measured properties. It has been demonstrated that although all damping models considered predict similar damping quality factor and agree well for predictions of closing time, the models differ by a factor of two and more in predicting the impact velocity and acceleration at contact. Implications of parameter uncertainties on the key reliability-related parameters such as the pull-in voltage, closing time and impact velocity are discussed. A notable effect of uncertainty is that the nominal switch, i.e. the switch with the average properties, does not actuate at the mean actuation voltage. Additionally, the device-to-device variability leads to significant differences in dynamics. For example, the mean impact velocity for switches actuated under the 90%-actuation voltage (about 150 V), i.e. the voltage required to actuate 90% of the sample, is about 129 cm/s and increases to 173 cm/s for the 99%-actuation voltage (of about 173 V). Response surfaces of impact velocity and closing time to five input variables were constructed using the Smolyak sparse grid algorithm. The sensitivity analysis showed that impact velocity is most sensitive to the damping coefficient whereas the closing time is most affected by the geometric parameters such as gap and beam thickness.     

用户眼动行为与网站设计要素关系研究

运用用户体验、感性工学、交互设计理论,以团购网站中浏览、搜索、查找、登陆购买这4个典型的交互任务为研究对象,研究交互设计要素与用户眼动行为之间的关系.首先,运用多维尺度和聚类分析选取4个代表性团购网站,并运用形态分析法提取网站的交互设计要素;其次,通过眼动实验获取用户在完成各交互任务中的眼动数据,并筛选出可反映用户情感体验的眼动指标;最后,通过数量化Ⅰ类理论将网站的交互设计要素进行编码,运用偏最小二乘回归方法建立不同交互任务下设计要素与眼动指标的关系模型,并给出了提高用户体验的设计变量组合建议.     

Densitometric quantification for the validation of decolorization of Disperse Orange ERL by lichen Parmelia sp.

1. Download high-res image (211KB)
2. Download full-size image

     

三维球形拐角内壁缺陷形状的红外定量计算

用红外技术、导热反问题计算及计算机技术相结合诊断工业热设备内壁缺陷的方法,因涉及到复杂的数学问题并受设备几何形状的限制,而具有挑战性。用该方法对三维球形拐角内壁缺陷进行计算。利用红外热像仪获取内壁形状未知设备的外壁温度场,将其作为强制边界条件,结合传热反问题计算,推导出了该形状内壁曲面的普适方程,从而确定缺陷的位置及尺寸,并从理论上证明了该方法的可行性,为这类缺陷的诊断提供了基础。给出的数学方法具有普适性,可应用到内部边界为第二及第三类条件的情况中。     

一种新型量化混沌序列的统计特性研究

提出了一种多值量化器，并对一维无限折叠混沌映射所产生的多值量化序列的统计特性与混沌映射和量化器参数的关系进行了研究。理论分析和统计检验表明，选择适当的参数可使量化序列接近于独立同分布序列。该多值序列发生器还具有结构简单、实现效率高等优点。因此，它可用于产生混沌扩谱序列和混沌密钥流序列。     

基于参数智能调节的模糊预估控制在时滞时变系统中的研究

在化工、炼油、冶金、矿山和建材等一些复杂拘工业过程当中，广泛地存在着时滞时变现象。由于时滞时变的存在，使得控制系统的稳定性变差，调节时间延长，对系统的设计和控制增加了很大的困难。如何控制时变时滞对象一直是控制界关注的课题之一。通常对于固定时滞系统，采用Smith预估控制器进行控制，其结构简单、控制品质好。但它对模型误差及时滞变化较敏感。本文就时滞时变系统提出一种参数智能调节的模糊预估控制，进行仿真研究。