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981.
Ling Yun Wang Wei Hua Gui Kok Lay Teo Ryan Loxton Chun Hua Yang 《Journal of Global Optimization》2012,54(2):307-323
Before zinc electrolysis, zinc powder is added to the zinc sulphate electrolyte solution to facilitate the removal of harmful metallic ions. This purification process can be modeled by a time delay differential equation. Since some of the parameters in this model are unknown, zinc powder is normally added excessively. We use an optimization technique to estimate the unknown parameters from experimental data. Then, we formulate an optimal control problem to minimize the amount of zinc powder added. We solve this optimal control problem numerically by using the control parametrization method. The results indicate that the amount of zinc powder added can be decreased, on average, by approximately 7%. 相似文献
982.
A proper vertex coloring of a graph G is linear if the graph induced by the vertices of any two color classes is the union of vertex-disjoint paths. The linear chromatic number lc(G) of the graph G is the smallest number of colors in a linear coloring of G. In this paper, it is proved that every planar graph G with girth g and maximum degree Δ has(1)lc(G) ≤Δ 21 if Δ≥ 9; (2)lc(G) ≤「Δ/2」 + 7 ifg ≥ 5; (3) lc(G) ≤「Δ/2」 + 2 ifg ≥ 7 and Δ≥ 7. 相似文献
983.
Gui Qiao Xu 《数学学报(英文版)》2012,28(8):1581-1596
For the weighted approximation in L p -norm, we determine the asymptotic order for the paverage errors of Lagrange interpolation sequence based on the Chebyshev nodes on the Wiener space. We also determine its value in some special case. 相似文献
984.
Jia Y Cao A Kang F Li P Gui X Zhang L Shi E Wei J Wang K Zhu H Wu D 《Physical chemistry chemical physics : PCCP》2012,14(23):8391-8396
Deposition of nanostructures such as carbon nanotubes on Si wafers to make heterojunction structures is a promising route toward high efficiency solar cells with reduced cost. Here, we show a significant enhancement in the cell characteristics and power conversion efficiency by growing a silicon oxide layer at the interface between the nanotube film and Si substrate. The cell efficiency increases steadily from 0.5% without interfacial oxide to 8.8% with an optimal oxide thickness of about 1 nm. This systematic study reveals that formation of an oxide layer switches charge transport from thermionic emission to a mixture of thermionic emission and tunneling and improves overall diode properties, which are critical factors for tailoring the cell behavior. By controlled formation and removal of interfacial oxide, we demonstrate oscillation of the cell parameters between two extreme states, where the cell efficiency can be reversibly altered by a factor of 500. Our results suggest that the oxide layer plays an important role in Si-based photovoltaics, and it might be utilized to tune the cell performance in various nanostructure-Si heterojunction structures. 相似文献
985.
Two structural isomers of six-fused-ring sulfur-containing molecules were synthesized as active materials for p-type organic field-effect transistors, and their optical and electrochemical properties were characterized. Field-effect transistors based on these compounds were fabricated to investigate the relationships between structures and semiconductor properties. 相似文献
986.
Dr. Feng‐Rong Dai Dr. Yung‐Chung Chen Lai‐Fan Lai Dr. Wen‐Jun Wu Chao‐Hua Cui Gui‐Ping Tan Xing‐Zhu Wang Prof. Jiann‐T'suen Lin Prof. He Tian Prof. Wai‐Yeung Wong 《化学:亚洲杂志》2012,7(6):1426-1434
Four new unsymmetric platinum(II) bis(aryleneethynylene) derivatives have been designed and synthesized, which showed good light‐harvesting capabilities for application as photosensitizers in dye‐sensitized solar cells (DSSCs). The absorption, electrochemical, time‐dependent density functional theory (TD‐DFT), impedance spectroscopic, and photovoltaic properties of these platinum(II)‐based sensitizers have been fully characterized. The optical and TD‐DFT studies show that the incorporation of a strongly electron‐donating group significantly enhances the absorption abilities of the complexes. The maximum absorption wavelength of these four organometallic dyes can be tuned by various structural modifications of the triphenylamine and/or thiophene electron donor, improving the light absorption range up to 650 nm. The photovoltaic performance of these dyes as photosensitizers in mesoporous TiO2 solar cells was investigated, and a power conversion efficiency as high as 1.57 % was achieved, with an open‐circuit voltage of 0.59 V, short‐circuit current density of 3.63 mA cm?2, and fill factor of 0.73 under simulated AM 1.5G solar illumination. 相似文献
987.
A hollow-structured heterojunction consisting of Bi2WO6 nanoplatelets and Bi2O3 nanoparticles was successfully prepared by a facile solvothermal process. Bi2O3/Bi2WO6 heterojunction is the aggregate of some hollow spheres with diameter ranging from several hundred nanometers to 1.5 μm and is connected to each other by tube-like cavums. On the basis of scanning and transmission electron microscopy observation and X-ray diffraction analysis of the samples synthesized at different reaction stages, a possible growth mechanism was proposed for the growth of hollow-structured Bi2O3/Bi2WO6 heterojunction. Its photocatalytic activity was evaluated by degradation of rhodamine B under visible-light irradiation (λ>400 nm). The results indicate that the hollow-structured Bi2O3/Bi2WO6 heterojunction exhibits much higher photocatalytic activity than both pure Bi2WO6 and pure Bi2O3. The improved photocatalytic performance can be ascribed to the heterojunction of Bi2O3 and Bi2WO6 in the framework in which the hierarchical hollow structure possesses good permeability and large surface area. More importantly, the hollow-structured Bi2O3/Bi2WO6 heterojunction is not only highly stable but also easy to be separated by simple sedimentation for recycle. 相似文献
988.
Yan-Qing Ge Teng Wang Gui Yun Duan Li Hua Dong Xiao Qun Cao Jian Wu Wang 《Journal of fluorescence》2012,22(6):1531-1538
Novel imidazo[1,5-a]pyridinyl 1,3,4-Oxadiazole derivatives were synthesized and characterised by IR, 1H NMR and HRMS.UV-vis absorption and fluorescence properties of these compounds in different solutions showed that the maximal emission wavelength was not significantly changed in different solvents; however, maximum absorption wavelength was blue-shifted with the increase of solvent polarity. Absorption λmax and emission λmax was less correlated with substituent groups on benzene rings. The calculated molecular orbital correlates well with their absorption. 相似文献
989.
Guilong Yang Dianjun Li Jijiang Xie Laiming Zhang Fei Chen Jin Guo Lihong Guo 《Laser Physics》2012,22(7):1173-1176
A high power repetitive spark-pin UV-preionized TEA CO2 laser system is presented. The discharge for generating laser pulses is controlled by a rotary spark switch and a high voltage pulsed trigger. Uniform glow discharge between two symmetrical Chang-electrodes is realized by using an auto-inversion circuit. A couple of high power axial-flow fans with the maximum wind speed of 80 m/s are used for gas exchange between the electrodes. At a repetitive operation, the maximum average output laser power of 10.4 kW 10.6 ??m laser is obtained at 300 Hz, with an electro-optical conversion efficiency of 15.6%. At single pulsed operation, more pumping energy and higher gases pressures can be injected, and the maximum output laser energy of 53 J is achieved. 相似文献
990.
L Qu Y Guo H Luo C Zhong G Yu Y Liu J Qin 《Chemical communications (Cambridge, England)》2012,48(80):9965-9967
A simple nickel bis(dithiolene) complex has been developed as an excellent n-type molecular semiconductor for FETs, with an electron mobility of 0.11 cm(2) V(-1) s(-1) and an on/off ratio of 2 × 10(6) despite its small π-conjugated system. Good FET stability in ambient conditions has also been observed. 相似文献