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991.
本文分析了JPEG压缩中的DCT变换和量化过程,根据量化的特性提出了一种半脆弱水印方案,并将水印信息调制为纠错码嵌入JPEG压缩过程的量化系数中,实验证明,此水印方案鲁棒性较强,虚警率低,能较好的检测图像是否被篡改并对篡改定位。 相似文献
992.
Electric Field Tunable Interlayer Relaxation Process and Interlayer Coupling in WSe2/Graphene Heterostructures 下载免费PDF全文
Yang Li Jing‐Kai Qin Cheng‐Yan Xu Jian Cao Zhao‐Yuan Sun Lai‐Peng Ma Ping An Hu Wencai Ren Liang Zhen 《Advanced functional materials》2016,26(24):4319-4328
Transition metal dichalcogenides van der Waals (vdWs) heterostructures present fascinating optical and electronic phenomena, and bear tremendous significance for electronic and optoelectronic applications. As the significant merits in vdWs heterostructures, the interlayer relaxation of excitons and interlayer coupling at the heterointerface reflect the dynamic behavior of charge transfer and the coupled electronic/structural characteristics, respectively, which may give rise to new physics induced by quantum coupling. In this work, upon tuning the photoluminescence (PL) properties of WSe2/graphene and WSe2/MoS2/graphene heterostructures by virtue of electric field, it is demonstrated that the interlayer relaxation of excitons at the heterointerface in WSe2/graphene, which is even stronger than that in MoS2/graphene and WSe2/MoS2 , plays a dominant role in PL tuning in WSe2/graphene, while the carrier population in WSe2 induced by electric field has a minor contribution. In addition, it is discovered that the interlayer coupling between monolayer WSe2 and graphene is enhanced under high electric field, which breaks the momentum conservation of first order Raman‐allowed phonons in graphene, yielding the enhanced Raman scattering of defects in graphene. The interplay between electric field and vdWs heterostructures may provide versatile approaches to tune the intrinsic electronic and optical properties of the heterostructures. 相似文献
993.
Hai-Lian Wang Chun-Yang Li Bin Zhang Yuan-De Liu Bang-Min Lu Zheng Shi Na An Liang-Kai Zhao Jing-Jing Zhang Jin-Ku Bao Yi Wang 《International journal of molecular sciences》2014,15(5):9016-9035
Mangiferin, a xanthonoid found in plants including mangoes and iris unguicularis, was suggested in previous studies to have anti-hyperglycemic function, though the underlying mechanisms are largely unknown. This study was designed to determine the therapeutic effect of mangiferin by the regeneration of β-cells in mice following 70% partial pancreatectomy (PPx), and to explore the mechanisms of mangiferin-induced β-cell proliferation. For this purpose, adult C57BL/6J mice after 7–14 days post-PPx, or a sham operation were subjected to mangiferin (30 and 90 mg/kg body weight) or control solvent injection. Mangiferin-treated mice exhibited an improved glycemia and glucose tolerance, increased serum insulin levels, enhanced β-cell hyperplasia, elevated β-cell proliferation and reduced β-cell apoptosis. Further dissection at the molecular level showed several key regulators of cell cycle, such as cyclin D1, D2 and cyclin-dependent kinase 4 (Cdk4) were significantly up-regulated in mangiferin-treated mice. In addition, critical genes related to β-cell regeneration, such as pancreatic and duodenal homeobox 1 (PDX-1), neurogenin 3 (Ngn3), glucose transporter 2 (GLUT-2), Forkhead box protein O1 (Foxo-1), and glucokinase (GCK), were found to be promoted by mangiferin at both the mRNA and protein expression level. Thus, mangiferin administration markedly facilitates β-cell proliferation and islet regeneration, likely by regulating essential genes in the cell cycle and the process of islet regeneration. These effects therefore suggest that mangiferin bears a therapeutic potential in preventing and/or treating the diabetes. 相似文献
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996.
安玉翠 《制冷与空调(北京)》2015,(2):57-63,56
以一个实际工程为例,进行冰蓄冷空调系统的设计,包括空调冷负荷(按当地气象条件及节能设计标准计算出空调冷负荷)、制冷机容量、蓄冰容量、制冷系统等的确定以及冰蓄冷系统的4种运行策略,并进行冰蓄冷空调系统与常规空调系统的经济性分析,根据工程所在地的分时电价政策,从设备初投资、冰蓄冷空调系统方案的国家政策补贴款、运行费用和投资回收期等数值的计算和对比分析,得出冰蓄冷空调系统虽然初投资比无蓄冷空调系统高,但运行费用却比无蓄冷空调系统低,且在电力上能有效发挥削峰填谷的作用,能够降低冷冻站高峰电力的需求量,充分利用夜间低谷电力电价差,节约制冷运行费用,同时可以有效地缓解高峰时段电力短缺的状况。虽然冰蓄冷中央空调系统从空调用户局部看节费不节能,但是对于业主而言,长期使用冰蓄冷空调系统能取得很好的经济效益,而从整个国家能源利用来讲,能充分利用夜间富裕的谷电,大量推广冰蓄冷空调项目,能够减少电厂数量或降低电厂总装机容量,提高电厂和电网的有效利用率和效率。 相似文献
997.
Pengfei Zhang Luzi Zhao Qinyou An Qiulong Wei Liang Zhou Xiujuan Wei Jinzhi Sheng Liqiang Mai 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(8):1082-1090
V2O5 hollow microclews (V2O5‐HMs) have been fabricated through a facile solvothermal method with subsequent calcination. The synthesized V2O5‐HMs exhibit a 3D hierarchical structure constructed by intertangled nanowires, which could realize superior ion transport, good structural stability, and significantly improved tap density. When used as the cathodes for lithium‐ion batteries (LIBs), the V2O5‐HMs deliver a high capacity (145.3 mAh g‐1) and a superior rate capability (94.8 mAh g‐1 at 65 C). When coupled with a lithiated Li3VO4 anode, the all‐vanadium‐based lithium‐ion full cell exhibits remarkable cycling stability with a capacity retention of 71.7% over 1500 cycles at 6.7 C. The excellent electrochemical performance demonstrates that the V2O5‐HM is a promising candidate for LIBs. The insight obtained from this work also provides a novel strategy for assembling 1D materials into hierarchical microarchitectures with anti‐pulverization ability, excellent electrochemical kinetics, and enhanced tap density. 相似文献
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999.
Marko Saban George Liebermann Alex Jay An‐Chang Shi Nam Ro William Dale Pat Forgione 《加拿大化工杂志》2000,78(2):320-329
Anionic polymerization of styrene in THF with n‐butyllithium/alpha‐methylstyrene initiator is described as a first step in preparation of a styrenic block copoly‐mer. In order to suppress rapid decay of living alpha‐methylstyrene unimers, which occurred at room temperature, the initiation reaction was carried out at ?20(+5)°C. The kinetic parameters of this decay reaction were determined and used for process optimization. By combining experiments with modelling of styrene propagation reaction all key process parameters were defined for l‐L, 38‐L, and 189‐L reactors. A good match was demonstrated between the model and experimental propagation exotherm for semibatch reaction conditions. Overall, it was demonstrated that technical grade THF and styrene could be used at pilot plant scale to prepare well‐defined polymers up to Mn 22 000 via the “living” polymerization mechanism. The resulting polymers had narrow molecular weight distributions (1.06 < Mw/Mn < 1.30). 相似文献
1000.