To explore the trend of fatty acid methyl esters (FAMEs) during the oxidation process of biodiesel , this study uses gas chromatography - mass spectrometry (GC-MS) combined with information entropy theory to propose a new method to analyze the effect of FAMEs on the stability of biodiesel (especially with different amounts of unsaturated FAMEs). The induction periods of the main FAMEs in biodiesel were determined by the Rancimat method. The results showed that the longest induction period of methyl stearate was 248 h, while the induction of methyl linoleate was only 0.12 h. Accelerated oxidation of biodiesel, using GC-MS analysis showed that the oxidation trends of FAMEs was different. The oxidation rate of methyl linoleate was the fastest. A mathematical equation was proposed to calculate the trend of FAMEs. The results showed that during the 5 h accelerated an oxidation process, the content of methyl linoleate decreased from 28.35% to 2.10%, while the content of methyl oleate decreased by 18.21%. Using information entropy, the weighting coefficients of FAMEs in the oxidation process of biodiesel were calculated. The weighting coefficient of methyl linoleate was as high as 0.6797. Methyl linoleate was the main reason why biodiesel was easily oxidized.
Wang Kun,Shi Jianwei,Lai Wenxuan,He Qiang,Xu Jun,Ni Zhenyi,Liu Xinfeng,Pi Xiaodong,Yang Deren
Integrated circuit anti-counterfeiting based on optical physical unclonable functions (PUFs) plays a crucial role in guaranteeing secure identification and authentication for Internet of Things (IoT) devices. While considerable efforts have been devoted to exploring optical PUFs, two critical challenges remain: incompatibility with the complementary metal-oxide-semiconductor (CMOS) technology and limited information entropy. Here, we demonstrate all-silicon multidimensionally-encoded optical PUFs fabricated by integrating silicon (Si) metasurface and erbium-doped Si quantum dots (Er-Si QDs) with a CMOS-compatible procedure. Five in-situ optical responses have been manifested within a single pixel, rendering an ultrahigh information entropy of 2.32 bits/pixel. The position-dependent optical responses originate from the position-dependent radiation field and Purcell effect. Our evaluation highlights their potential in IoT security through advanced metrics like bit uniformity, similarity, intra- and inter-Hamming distance, false-acceptance and rejection rates, and encoding capacity. We finally demonstrate the implementation of efficient lightweight mutual authentication protocols for IoT applications by using the all-Si multidimensionally-encoded optical PUFs.
危险品化学品经营许可证（带存储）