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191.
Multiaxial mechanical behavior of aramid fibers and identification of skin/core structure from single fiber transverse compression testing
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Judith Wollbrett‐Blitz Sébastien Joannès Rémi Bruant Christophe Le Clerc Marc Romero De La Osa Anthony Bunsell Alba Marcellan 《Journal of Polymer Science.Polymer Physics》2016,54(3):374-384
The transverse and longitudinal mechanical properties of aramid fibers like Kevlar? 29 (K29) fibers are strongly linked to their highly oriented structure. Mechanical characterization at the single fiber scale is challenging especially when the diameter is as small as 15 µm. Longitudinal tensile tests on single K29 fibers and single fiber transverse compression test (SFTCT) have been developed. Our approach consists of coupling morphological observations and mechanical experiments with SFTCT analysis by comparing analytical solutions and finite element modeling. New insights on the analysis of the transverse direction response are highlighted. Systematic loading/unloading compression tests enable to experimentally determine a transverse elastic limit. Taking account of the strong anisotropy of the fiber, the transverse mechanical response sheds light on a skin/core architecture. More importantly, results suggest that the skin of the fiber, typically representing a shell of one micrometer in thickness, has a transverse apparent modulus of 0.2 GPa. That is around more than fifteen times lower than the transverse modulus of 3.0 GPa in the core. By comparison, the measured longitudinal modulus is about 84 GPa. The stress distribution in the fiber is explored and the critical areas for damage initiation are discussed. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 374–384 相似文献
192.
Brownian distance correlation-directed search: A fast feature selection technique for alternate test
Machine-learning indirect test relies on powerful statistical algorithms to build prediction models that relate cheap measurements to costly performance metrics. Though many works in the past have been focused on proposing different models or on ways to improve the reliability of the results, it appears that the main bottleneck of the approach is the definition of an information-rich input space. Finding the appropriate measurements that are both cheap and meaningful is a task that has not yet been automated. In this framework, feature selection is a necessary tool to explore possible candidates. In this paper a hybrid method is proposed that lay between filtering and wrapper-based methods, trying to strike the right balance between accuracy and speed for the particular case of Alternate Test. 相似文献
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194.
Flexible aluminum moisture barrier films are shown to meet ultra-barrier requirements with water vapor transmission rates as low as 1*10−4 g/m2/day at 38 °C and 90% R.H. These low transmission rates are achieved by lamination of two films that are independently processed on individual substrates. The integration in organic electronic devices like organic solar cells or OLEDs is particularly easy in a single lamination step, since an existing aluminum electrode can be utilized as one half of the moisture barrier. The resulting laminate maintains flexibility of the device and improves the barrier quality by an order of magnitude compared to conventional stacking of two barriers. Organic solar cells with this type of encapsulation are manufactured and aged in controlled climate. They do not exhibit significant extrinsic degradation. 相似文献
195.
鉴于假设检验在统计推断中的重要地位和学习它的困难度,通过讨论两类错误的产生与控制,结合概率论中的"小概率原理"和逻辑方法中的"反证法",给出了一种清晰简便的假设检验推导和推理方法。该方法适用于一个总体下总体均值、总体比例、总体方差的检验,也适用于两个个总体下总体均值、总体比例、总体方差的检验。检验结果表明,该推理方法简便、自然、适宜推广。 相似文献
196.
《Journal of computational and graphical statistics》2013,22(4):946-953
When designing programs or software for the implementation of Monte Carlo (MC) hypothesis tests, we can save computation time by using sequential stopping boundaries. Such boundaries imply stopping resampling after relatively few replications if the early replications indicate a very large or a very small p value. We study a truncated sequential probability ratio test (SPRT) boundary and provide a tractable algorithm to implement it. We review two properties desired of any MC p value, the validity of the p value and a small resampling risk, where resampling risk is the probability that the accept/reject decision will be different than the decision from complete enumeration. We show how the algorithm can be used to calculate a valid p value and confidence intervals for any truncated SPRT boundary. We show that a class of SPRT boundaries is minimax with respect to resampling risk and recommend a truncated version of boundaries in that class by comparing their resampling risk (RR) to the RR of fixed boundaries with the same maximum resample size. We study the lack of validity of some simple estimators of p values and offer a new, simple valid p value for the recommended truncated SPRT boundary. We explore the use of these methods in a practical example and provide the MChtest R package to perform the methods. 相似文献
197.
《Analytical letters》2012,45(11):2145-2154
Abstract A color test is presented for the purpose of quickly identifying glazed ceramic and/or enameled metalware which releases excessive Pb. Citric acid solution on filter paper is used to extract Pb from the ware and a Pb-sensitive chromogen indicates the presence of Pb on the paper. The quick color test takes approximately 30 min and is useful for screening ware to determine the need for testing by the 24-h method of the Association of Official Analytical Chemists/American Society for Testing and Materials. 相似文献
198.
本文主要对现阶段应用电子商务范围主要结构予以介绍,如今最佳的方法就是立足于这样的结构软件测试技术,凭借有效结合局部分层与整体测试方法,这种方法从局部与整体对应用软件实施测试,为用户可用性与开发软件性能要求提供保证。 相似文献
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200.
Simultaneous determination of boscalid and fludioxonil in grape and soil under field conditions by gas chromatography/tandem triple quadrupole mass spectrometry
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《Biomedical chromatography : BMC》2018,32(2)
A gas chromatography–tandem mass spectrometry method was developed and validated to simultaneously determine boscalid and fludioxonil in grape and soil samples. These samples were extracted with 10 mL of acetonitrile and purified using a mixed primary secondary amine/octadecylsilane sorbent. The method showed good linearity (R2 > 0.99) in the calibration range 0.005–2 μg/mL for both pesticides. The limits of detection and quantification for the two analytes in grape and soil were 0.006 and 0.02 mg/kg, respectively. Fungicide recoveries in grape and soil were 81.18–92.11% for boscalid and 82.73–97.67% for fludioxonil with relative standard deviations of 1.31–10.31%. The established method was successfully applied to the residual analysis of boscalid and fludioxonil in real grape and soil samples. The terminal residue concentrations of boscalid and fludioxonil in grape samples collected from Anhui and Guizhou were <5 mg/kg (the maximum residue limit set by China) 7 days after the last application and 1 mg/kg (the maximum residue limit set by USA) 14 days after the last application. These results could provide guidance for the proper and safe use of boscalid and fludioxonil in grape and help the Chinese government to establish an MRL for fludioxonil in grape. 相似文献