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71.
Non-uniformity (NU) evaluation metric of infrared thermal imaging system is important for evaluating the thermal imager and also can help to improve existing NU correction methods. However, in existing evaluation metrics, there are still some problems, such as not objective enough and not comprehensive enough. This paper brings forward a novel NU evaluation metric, in which we adopt the average derivative of the response of thermal imager with the temperature of test blackbody as a new parameter. A metric-temperature curve which shows the change trend of the NU with the temperature of test blackbody was achieved to enhance the performance of NU evaluation metric. Both the subjective images and objective data indicate that the new method raised in this work is much more objective and comprehensive. Our work is expected to become a general NU evaluation metric in the future. 相似文献
72.
We apply the multifractal detrending moving average (MFDMA) to investigate and compare the efficiency and multifractality of 5-min high-frequency China Securities Index 300 (CSI 300). The results show that the CSI 300 market becomes closer to weak-form efficiency after the introduction of CSI 300 future. We find that the CSI 300 is featured by multifractality and there are less complexity and risk after the CSI 300 index future was introduced. With the shuffling, surrogating and removing extreme values procedures, we unveil that extreme events and fat-distribution are the main origin of multifractality. Besides, we discuss the knotting phenomena in multifractality, and find that the scaling range and the irregular fluctuations for large scales in the Fq(s) vs s plot can cause a knot. 相似文献
73.
The government has been acting as an important role in the formation and operation of closed-loop supply chain. This paper focuses on how consumption-subsidy influences dual-channel closed-loop supply chain. After introducing government consumption-subsidy program and dual-channel closed-loop supply chain, the paper analyzes the channel members’ decisions before and after the government-funded program performance, respectively. Finally, influence of consumption-subsidy has been considered from the consumers, the scale of closed-loop supply chain and the enterprises perspectives, which provides an important basis for our propositions. The key propositions of the paper are listed as follows: All the consumers that purchase the new products are beneficiaries of the government consumption-subsidy in varying degrees; the consumption-subsidy is conducive to the expansion of closed-loop supply chain; both the manufacturer and the retailer are beneficiaries of the consumption-subsidy, while the e-tailer benefits or not is uncertain. 相似文献
74.
A DMAP (4-dimethylaminopyridine) catalyzed cyclization of methyl 2-alkynylbenzimidates has been developed, which affords 3-methoxy-1-methyleneisoindoles with excellent Z-stereoselectivity under mild and transition-metal-free conditions. The (Z)-3-methoxy-1-methyleneisoindole products can be converted to corresponding 3-amino-1-methyleneisoindoles, 3-methoxy-isoindoles, 3-methyleneisoindolinones and isoindolinones with high efficiency. 相似文献
75.
Yang Bai Xiang Yao Jiandong Wang Jin-Long Wang Si-Cheng Wu Shi-Ping Yang Wei-Shi Li 《Tetrahedron》2019,75(33):4676-4685
Fullerene-based organic solar cells are generally suffering from severe microstructure evolution occurring in their bulk heterojunction active layers and thus are extremely stable. To address it, four polymerizable C70 fullerene derivatives, [6,6]-phenyl-C71-ethyl acrylate (PC71EA), [6,6]-phenyl-C71-propyl acrylate (PC71PrA), [6,6]-phenyl-C71-butyl acrylate (PC71BA), and [6,6]-phenyl-C71-pentyl acrylate (PC71PeA), have been designed, synthesized, and investigated. These fullerene compounds have a molecular structure, shape and size very like the conventional C70 fullerene acceptor, [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), and have been found no different in their light absorption, redox potentials, and frontier orbital energy levels. Using these fullerene acrylates individually as acceptor and poly(3-hexylthiophene) as donor, organic solar cells have been fabricated and gave optimal efficiencies ranging from 3.32% to 4.16%, comparable to PC71BM-based reference cells (4.06%). Owing to their acrylate functionality, these fullerene derivatives can turn into insoluble upon heating, and thus endow their solar cell devices much better thermostability than PC71BM-based reference cells. The best one, coming from PC71PeA devices, reported an optimal efficiency of 4.16%, and maintained 91.7% efficiency after heat treatment at 150 °C for 35 h. As a sharp contrast, the PC71BM reference cell dropped its optimal efficiency from 4.06% to 0.48% only after 5 h heat treatment. X-ray diffraction, optical and atomic force microscopy, and space-charge-limited current method have been carried out to understand active layer structure, morphology, and charge mobility change during heat treatment. 相似文献
76.
Bing-Jie Zhang Wen-Na Xiao Jing Chen Mei-Fen Bao Johann Schinnerl Qi Wang Xiang-Hai Cai 《Tetrahedron》2019,75(38):130515
Continued interest in Erythrina alkaloids resulted in the isolation of 38 alkaloids including 7 undescribed ones from the leaves of Erythrina arborescens Roxburgh. Among the new compounds, erythrivarines H-I were two dimeric alkaloids, while others were Erythrina alkaloid glucosides. Dimeric Erythrina alkaloids and monomers, turcomanidine and isoboldine, showed medium xanthine oxidase inhibition. 相似文献
77.
An efficient method of copper-catalyzed aryldifluoromethylenation of N-arylacrylamides is described to step-economic synthesis of the various biologically important biheterocyclic compounds linked by gem-difluoromethylene moiety through addition of benzo-1,3-azolic (oxa- or thia-)difluoromethyl radicals generated in situ to terminal of C–C double bond of N-arylacrylamides then cyclization cascade. This protocol has demonstrated to have broad substrate scope and excellent functional-group tolerance under mild reaction conditions. 相似文献
78.
Tao Li Ping-Lin Li Xiang-Chao Luo Xu-Li Tang Guo-Qiang Li 《Tetrahedron letters》2019,60(30):1996-1998
Three new dibromopyrrole alkaloids, 9-N-methylcylindradine A (1), 1-N-methylugibohlin (2), nemoechine H (3), together with one known dibromopyrrole alkaloid N-methyldibromoisophakellin (4) were isolated from the South China Sea sponge Agelas nemoechinata. Their structures were elucidated by comprehensive spectroscopic methods including HRESIMS and NMR, and the absolute configuration of compound 1 was further confirmed by comparison of optical rotation. Compound 3 exhibited moderate cytotoxic activity against K562 and L-02 with IC50 values of 6.1 μM and 12.3 μM, respectively. 相似文献
79.
Xinxin Yuan Lulu Wu Cuilian Xu Zhenliang Pan Lijun Shi Guoyu Yang Caixia Wang Sufang Fan 《Tetrahedron letters》2019,60(52):151329
A one-pot two-step reaction of 3-(trifluoroacetyl)coumarin and indole afforded trifluoromethyl-substituted bis(indolyl)methane compounds containing coumarin skeleton. The atomic economic and simply manipulative reaction involved premier treatment of reaction mixtures with Sc(OTf)3, followed by p-TSA in one-pot process. The reaction proceeded to give the title compounds in high yields (up to 95% yield). 相似文献
80.
Qiang Xue Yajie Zhang Ruoning Li Chao Li Na Li Chenyang Yuan Shimin Hou Yongfeng Wang 《中国化学快报》2019,30(12):2355-2358
The self-assembly of l-tryptophan on Cu(111) is investigated by an ultrahigh vacuum scanning tunneling microscope (STM) at 4.4 K. When deposited onto the substrate at around 120 K with a coverage of 0.1 monolayer, molecular trimers, tetramers, hexamers, and chains coexist on Cu(111). Then almost all molecules self-assemble into chiral hexamers after being annealed at room temperature. When increasing molecular coverage to the full layer, a new type of chain is observed on the surface. Based on the high-resolution STM images at sub-molecular level, we suggest that the l-tryptophan molecules are present in neutral, zwitterionic or anionic states in these structures. 相似文献