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141.
Rui Feng Li Zhang Huapeng Ruan Yue Zhao Gengwen Tan Xinping Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6145-6149
The first main‐group element radical based one‐dimensional magnetic chain ( 1K )n was realized by one‐electron reduction of the pyridinyl functionalized borane 1 with elemental potassium in THF in the absence of 18‐crown‐6 (18‐c‐6). The electron spin density of ( 1K )n mainly resides at the boron centers with a considerable contribution from central benzene and pyridine moieties. The spin centers exhibit an antiferromagnetic interaction as demonstrated by magnetic measurements and theoretical calculations. In contrast, the reduction in the presence of 18‐c‐6 afforded the separated radical anion salt 1K(Crown) , in which the potassium cation was trapped by THF and 18‐c‐6 molecules. Further one‐electron reduction of 1K(Crown) and ( 1K )n led to the diamagnetic monomer and polymer, respectively. 相似文献
142.
143.
Dong Chen Prof. Zhifeng Liu Dr. Zhengang Guo Dr. Mengnan Ruan Prof. Weiguo Yan 《ChemSusChem》2019,12(14):3286-3295
The construction of junctions on hematite is an effective way to overcome the problems of slow charge separation and transfer kinetics, but constructing the junction is a significant challenge in photoelectrochemical (PEC) water splitting. Herein, a considerable improvement in PEC performance for α-Fe2O3 was achieved following the introduction of a p–n homojunction between n-type α-Fe2O3 and p-type Ca-doped α-Fe2O3 through a facile hydrothermal method. The resultant 3D branched Ca-Fe2O3/Fe2O3 enhanced the absorption intensity and reached a photocurrent density of 2.14 mA cm−2 at 1.23 V vs. reversible hydrogen electrode (RHE). The merit of the desired lattice matching of the buried p–n homojunction structure built an internal electric field, which led to appropriate band alignment. These results were supported by a series of photoelectrochemical measurements, in particular, surface photovoltage (SPV) measurements. For further improvement of the charge-separation efficiency, a combination of separated cocatalysts was established on the homojunction structure, in which Pt acted as the electron collector and was deposited on the bottom, and Co-Pi as the hole-extraction cocatalyst was inserted to accelerate hole transfer on the surface of the photoanode. The resulting Co-Pi/Ca-Fe2O3/Fe2O3/Pt branched nanorods showed a significant improvement in charge-separation efficiency and photocurrent density (2.94 mA cm−2 at 1.23 V vs. RHE). The present strategy, both the construction of the p–n homojunction and the coupling electron- and hole-transfer cocatalyst, could be expanded to many unstable or low-efficiency semiconductors for the design and fabrication of cost-effective photoanodes in PEC water splitting. 相似文献
144.
Deyin Kong Xiaojun Wu Bo Wang Tianxiao Nie Meng Xiao Chandan Pandey Yang Gao Lianggong Wen Weisheng Zhao Cunjun Ruan Jungang Miao Yutong Li Li Wang 《Advanced Optical Materials》2019,7(20)
Flexible manipulation of terahertz wave polarizations during the generation process is very important for terahertz applications, especially for the next‐generation on‐chip functional terahertz sources. However, current terahertz emitters cannot satisfy such demand, hence calling for new mechanisms and conceptually new terahertz sources. Here an efficient and broadband terahertz source with magnetic‐field‐controlled flexible switching for the polarizations between linear and elliptical states in ferromagnetic heterostructures driven by femtosecond laser pulses is demonstrated. More importantly, the chirality, azimuthal angle, and ellipticity of the generated elliptical terahertz wave can be precisely manipulated by harnessing external magnetic fields via effectively tailoring the photoinduced spin currents. Such an ultrafast photomagnetic interaction‐based, magnetic‐field‐controlled, and broadband tunable solid‐state terahertz source integrated with polarization tunability functions not only provides the capability to reveal physical mechanisms of femtosecond spin dynamics, but also demonstrates the feasibility to realize novel on‐chip terahertz functional devices, boosting the potential applications for controlling elementary molecular rotations, phonon vibrations, spin precessions, high‐speed communications, and accelerating the development of ultrafast terahertz optospintronics. 相似文献
145.
A priori investigation of subgrid correlation of mixture fraction and progress variable in partially premixed flames 总被引：1，自引：0，他引：1
Zhi X. Chen N. Anh Khoa Doan Shaohong Ruan Ivan Langella N. Swaminathan 《Combustion Theory and Modelling》2018,22(5):862-882
Subgrid correlation of mixture fraction, Z, and progress variable, c, is investigated using direct numerical dimulation (DNS) data of a hydrogen lifted jet flame. Joint subgrid behaviour of these two scalars are obtained using a Gaussian-type filter for a broad range of filter sizes. A joint probability density function (JPDF) constructed using single-snapshot DNS data is compared qualitatively with that computed using two independent β-PDFs and a copula method. Strong negative correlation observed at different streamwise locations in the flame is captured well by the copula method. The subgrid contribution to the Z–c correlation becomes important if the filter is of the size of the laminar flame thickness or larger. A priori assessment for the filtered reaction rate using the flamelet approach with independent β-PDFs and correlated JPDF is then performed. Comparison with the DNS data shows that both models provide reasonably good results for a range of filter sizes. However, the reaction rate computed using copula JPDF is found to have a better agreement with the DNS data for large filter sizes because the subgrid Z–c correlation effect is included. 相似文献
146.
In this paper, we consider an inverse time-dependent source problem of heat conduction equation.Firstly, the ill-posedness and conditional stability of this inverse source problem is analyzed. Then, a finite difference inversion method is proposed for reconstructing the time-dependent source from a nonlocal measurement. The existence and uniqueness of the finite difference inverse solutions are rigorously analyzed, and the convergence is proved. Combined with the mollification method, the propos... 相似文献
147.
It is well known that for a Brownian motion, if we change the medium to be inhomogeneous by a measure μ, then the new motion(the time-changed process) will diffuse according to a different metric D(·, ·).In 2009, Kigami initiated a general scheme to construct such metrics through some self-similar weight functions g on the symbolic space. In order to provide concrete models to Kigami’s theoretical construction, in this paper,we give a thorough study of his metric on two classes of fractals of pr... 相似文献
148.
149.
用能量法求多自由度振动系统的角频率 总被引：1，自引：1，他引：1
利用简谐振动能量方程，通过分析振幅矢量的关系，用能量法求多自由度振动系统的角频率或简正振动频率。 相似文献
150.
<正>Cr ion implantations in glass with the different doses of D=1.493×10~(17) and 4.976×10~(17) ion/cm~2 are obtained by metal vapor vacuum arc(MEVVA).The effects of the different Cr ion implanted doses on terahertz(THz) transmission property are analyzed from THz time-domain spectroscopy.The results show that the more the Cr ion implanted dose in the micro-area implantation glasses,the larger the THz transmission except the larger absorption at 0.24 THz.This is an effect attributed to the coupling of plasmas on both the implantation and the implantation affected zones of the Cr ion implantation glass. 相似文献