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991.
Stock markets in the world are linked by complicated and dynamical relationships into a temporal network.Extensive works have provided us with rich findings from the topological properties and their evolutionary trajectories,but the underlying dynamical mechanism is still not in order.In the present work,we proposed a technical scheme to reveal the dynamical law from the temporal network.The index records for the global stock markets form a multivariate time series.One separates the series into segments and calculates the information flows between the markets,resulting in a temporal market network representing the state and its evolution.Then the technique of the Koopman decomposition operator is adopted to find the law stored in the information flows.The results show that the stock market system has a high flexibility,i.e.,it jumps easily between different states.The information flows mainly from high to low volatility stock markets.And the dynamical process of information flow is composed of many dynamic modes distribute homogenously in a wide range of periods from one month to several ten years,but there exist only nine modes dominating the macroscopic patterns. 相似文献
992.
Enhancing the thermoelectric performance through the mutual interaction between conjugated polyelectrolytes and single-walled carbon nanotubes 下载免费PDF全文
We present a method of constructing composites composed of conjugated polyelectrolytes(CPEs)and singlewalled carbon nanotubes(SWCNTs)to obtain a high-performing flexible thermoelectric generator.In this approach,three kinds of polymers,namely,poly[(1,4-(2,5-didodecyloxybenzene)-alt-2,5-thiophene](P1),poly[(1,4-(2,5-bis-sodium butoxysulfonate-phenylene)-alt-2,5-thiophene](P2),and poly[(1,4-(2,5-bis-acid butoxysulfonic-phenylene)-alt-2,5-thiophene](P3)are designed,synthesized and complexed with SWCNTs as thermoelectric composites.The electrical conductivities of the CPEs/SWCNTs(P2/SWCNTs,and P3/SWCNTs)nanocomposites are much higher than those of non-CPEs/SWCNTs(P1/SWCNTs)nanocomposites.Among them,the electrical conductivity of P2/SWCNTs with a ratio of 1:4 reaches 3686 S·cm-1,which is 12.4 times that of P1/SWCNTs at the same SWCNT mass ratio.Moreover,CPEs/SWCNTs composites(P2/SWCNTs)display remarkably improved thermoelectric properties with the highest power factor(PF)of 163μW·m-1·K-1.In addition,a thermoelectric generator is fabricated with P2/SWCNTs composite films,and the output power and power density of this generator reach 1.37μW and 1.4 W·m;(cross-section)at△T=70 K.This result is over three times that of the thermoelectric generator composed of non-CPEs/SWCNTs composite films(P1/SWCNTs,0.37μW).The remarkably improved electrical conductivities and thermoelectric properties of the CPEs/SWCNTs composites(P2/SWCNTs)are attributed to the enhanced interaction.This method for constructing CPEs/SWCNTs composites can be applied to produce thermoelectric materials and devices. 相似文献
993.
To control the temporal profile of a relativistic electron beam to meet requirements of various advanced scientific applications like free-electron-laser and plasma wakefield acceleration, a widely-used technique is to manipulate the dispersion terms which turns out to be one-to-many problems. Due to their intrinsic one-to-many property, current popular stochastic optimization approaches on temporal shaping may face the problems of long computing time or sometimes suggesting only one solution. Here we propose a real-time solver for one-to-many problems of temporal shaping, with the aid of a semi-supervised machine learning method, the conditional generative adversarial network (CGAN). We demonstrate that the CGAN solver can learn the one-to-many dynamics and is able to accurately and quickly predict the required dispersion terms for different custom temporal profiles. This machine learning-based solver is expected to have the potential for wide applications to one-to-many problems in other scientific fields. 相似文献
994.
The third generation enhanced heat transfer technologies, such as three-dimensional fin and dimple, are still important means of improving energy efficiency and will continue to be challenging issues. This paper concentrates on the analysis of the condensation heat transfer performance of an edge-shaped finned-tube fabricated by extrusion–ploughing process. Experimental results show that the overall heat transfer coefficient increases with increases of volumetric flow rate of cold water and heat flux whereas the shell side heat transfer coefficient decreases with volumetric flow rate and heat flux increasing. At the similar volumetric flow rate, the shell side heat transfer coefficient of the edge-shaped finned-tube is 4–6 times larger than that of the smooth tube. At the similar volumetric flow rate, the shell side heat transfer coefficient of edge-shaped finned-tube increases with ploughing depth increasing. At the same temperature difference between wall and vapor, the shell side heat transfer coefficient is also higher than what had been reported in the literature. 相似文献
995.
996.
Amphiphilic graft copolymers are excellent additives for the development of antifouling membranes by nonsolvent induced phase separation. We report a convenient approach to the synthesis of novel graft copolymers with hydrophobic polyacrylonitrile (PAN) backbones and hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) side chains. Atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate was carried out with poly(acrylonitrile-co-p-chloromethyl styrene) (PAN-co-PCMS) as a macroinitiator in the presence of CuCl/2,2’-bipyridine at 50 °C in dimethyl sulfoxide. Kinetics of the graft polymerization was also evaluated. The synthesis of poly(acrylonitrile-co-p-chloromethyl styrene-g-2-hydroxyethyl methacrylate) (PAN-co-(PCMS-g-PHEMA)) can be relatively controlled when CMS (the ATRP sites) unit in the macroinitiator is around 5 mol%. Both the macroinitiators and graft copolymers were characterized by FTIR, NMR and GPC. The surface morphology and wettability of the copolymer films were studied by AFM and water contact angle measurement, respectively. We demonstrate that phase segregation between the PAN-co-PCMS backbones and the PHEMA side chains takes place and the surface hydrophilicity of the graft copolymers increases with the length of the PHEMA side chains. Because these amphiphilic graft copolymers can be synthesized in mass, they will be useful as latent additives for the fabrication of advanced PAN separation membranes. 相似文献
997.
ABSTRACT: BACKGROUND: Alzheimer's disease (AD) is a neurologically degenerative disorder that affects more than 20 million people worldwide. The selective butyrylcholinesterase (BChE) inhibitors and bivalent cholinesterase (ChE) inhibitors represent new treatments for AD. FINDINGS: A series of lycorine derivatives (1--10) were synthesized and evaluated for anti-cholinesterase activity. Result showed that the novel compound 2-O-tert-butyldimethylsilyl-1-O-(methylthio)methyllycorine (7) was a dual inhibitor of human acetylcholinesterase (hAChE) and butyrylcholinesterase (hBChE) with IC50 values of 11.40 [PLUS-MINUS SIGN] 0.66 muM and 4.17 [PLUS-MINUS SIGN] 0.29 muM, respectively. The structure-activity relationships indicated that (i) the 1-O-(methylthio)methyl substituent in lycorine was better than the 1-O-acetyl group for the inhibition of cholinesterase; (ii) the acylated or etherified derivatives of lycorine and lycorin-2-one were more potent against hBChE than hAChE; and (iii) the oxidation of lycorine at C-2 decreases the activity. CONCLUSION: Acylated or etherified derivatives of lycorine are potential dual inhibitors of hBChE and hAChE. Hence, further study on the modification of lycorine for ChE inhibition is necessary. 相似文献
998.
Gang Liu Yan‐Hu Li Wan‐Yi Tan Zhi‐Cai He Xiao‐Tie Wang Chi Zhang Prof. Yue‐Qi Mo Prof. Xu‐Hui Zhu Prof. Junbiao Peng Prof. Yong Cao 《化学:亚洲杂志》2012,7(9):2126-2132
A new series of monoammonium‐based organic electrolytes with the tetrafluoroborate (BF4?) counteranion have been synthesized. Replacing the pendant ethyl groups in the fluorenyl unit with 4‐ethoxyphenyl groups dramatically improves both solubility and morphological stability. The characterization of the alcohol‐processable amorphous ionic compounds as an electron‐injection layer in organic light‐emitting diodes (OLEDs) reveals that the organic electrolyte that comprises a rigid linear‐conjugated unit provides better device performance, with respect to its counterpart containing a branched bulky moiety. The capability of these compounds to facilitate electron injection from air‐stable aluminum metal is preliminarily discussed on the basis of the investigations of the electron‐only devices and photovoltaic experiments. 相似文献
999.
Dr. Nuo‐Wei Zhang Prof. Chuan‐Jing Huang Xiao‐Quan Zhu Jing‐Dong Xu Prof. Wei‐Zheng Weng Prof. Hui‐Lin Wan 《化学:亚洲杂志》2012,7(8):1895-1901
The effects of calcination temperature and feedstock pretreatment on the catalytic performance of Co/γ‐Al2O3 catalysts were studied for partial oxidation of methane (POM) to synthesis gas, with emphasis on the role of feedstock pretreatment. The physicochemical properties of the catalysts were characterized by N2 adsorption, X‐ray diffraction (XRD), transmission electron microscopy (TEM), H2 temperature‐programmed reduction (H2‐TPR), and Raman spectroscopy. The results showed that the pretreatment of the catalyst by reaction gas significantly improved the catalytic activity and stability for the POM reaction. On the other hand, the effect of calcination temperature was less significant. Although the initial activity was increased by an increased calcination temperature, the catalyst without the feedstock pretreatment suffered a rapid deactivation. The reaction‐atmosphere pretreatment was revealed as a process that mainly modified the surface structure of the catalyst. In that process, the formation of a CoAl2O4‐like compound led to high Co metal dispersion after reduction, and the transformation of the carrier into α‐Al2O3 occurred over the catalyst surface. Both the high dispersion of cobalt and the presence of α‐Al2O3 surface phase were assumed as the important factors resulting in an excellent catalytic performance in terms of high activity and high stability. 相似文献
1000.
Guang Peng Zhou Yong Hai Hui Ning Ning Wan Qiu Ju Liu Zheng Feng Xie Ji De Wang 《中国化学快报》2012,23(6):690-694
A series of novel Schiff bases bearing triazole structure were synthesized and characterized by IR and NMR.Mn(OAc)2/Schiff base efficiently catalyzed Henry reaction of nitroalkanes with aldehydes to produce the corresponding products of β-nitroalcohols, under mild conditions with high yields(up to 99%).A reaction mechanism is proposed based on the experimental results. 相似文献