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111.
New thermoelectric materials, n-type Bi6Cu2Se4O6 oxyselenides, composed of well-known BiCuSeO and Bi2O2Se oxyselenides, are synthesized with a simple solid-state reaction. Electrical transport properties, microstructures, and elastic properties are investigated with an emphasis on thermal transport properties. Similar to Bi2O2Se, it is found that the halogen-doped Bi6Cu2Se4O6 possesses n-type conducting transports, which can be improved via Br/Cl doping. Compared with BiCuSeO and Bi2O2Se, an extremely low thermal conductivity can be observed in Bi6Cu2Se4O6. To reveal the origin of low thermal conductivity, elastic properties, sound velocity, Grüneisen parameter, and Debye temperature are evaluated. Importantly, the calculated phonon mean free path of Bi6Cu2Se4O6 is comparable to the interlayer distance for BiO─CuSe and BiO─Se layers, which is ascribed to the strong interlayer phonon scattering. Contributing from the outstanding low thermal conductivity and improved electrical transport properties, the maximum ZT ≈0.15 at 823 K and ≈0.11 at 873K are realized in n-type Bi6Cu2Se3.2Br0.8O6 and Bi6Cu2Se3.6Cl0.4O6, respectively, indicating the promising thermoelectric performance in n-type Bi6Cu2Se4O6 oxyselenides. 相似文献
112.
目前,很少有文章就如何实现宽角度吸波材料进行详细的理论分析和设计指导,设计宽角度吸波材料仍然是一件很困难的事情.本文基于等效介质理论对带有反射地板的单层介质超材料吸波体进行较为详细的理论分析.从基础电磁理论出发,推导TE波(横电波,电场方向与入射面垂直的平面电磁波)和TM波(横磁波,磁场方向与入射面垂直的平面电磁波)照射下吸波体的反射系数,分析实现宽角度吸波效果所需的等效电磁参数,为宽角度超材料吸波体的设计提供了理论基础.此外,论文还理论分析了实现宽带宽角吸波等效电磁参数所要满足的条件,并做了计算检验.结果表明,当介质等效电磁参数按照特殊曲线随频率发生变化时,理论上能实现宽带宽角的吸波效果. 相似文献
113.
A simple method was proposed to prepare nanosized Si composite anode materials for lithium-ion (Li-ion) batteries. The preparation
started with the shock-type ball milling of silicon in liquid media of polyacrylonitrile (PAN)/dimethylformamide (DMF) solution,
forming slurry where the nano-Si particles were uniformly dispersed, followed by the drying of the slurry to remove DMF. The
nanosized Si composite anode material was obtained after the pyrolysis of the mixture at 300 °C where the pyrolyzed PAN provided
a conductive matrix to relieve the morphological change of Si during cycling. As-prepared composite presented good cyclability
for lithium storage. The proposed process paves an effective way to prepare high performance Si, Sn, Sb and their alloys based
composite anode materials for Li-ion batteries. 相似文献
114.
The energy loss of slow ions during grazing scattering from a LiF(100) surface as a function of the projectile atomic number Z1 is observed to show oscillations similar to those occurring in metals. A model of stopping of ions in an electron gas where screening is calculated from density functional theory reproduces well the experimental data. The same model gives good agreement with the energy loss obtained in transmission experiments performed with H and He projectiles. Analysis of these results allows us to gain new insights in the stopping of slow ions in ionic crystals. 相似文献
115.
116.
Fourier transform infrared spectroscopy(FTIR) and circular dichroism(CD) were used to investigate the conformational changes of heated whey protein(WP) and the corresponding changes in the hydrolysates immunoreactivity were determined by competitive enzyme-linked immunosorbent assay(ELISA).Results showed that the contents of α-helix and β-sheet of WP did not decrease much under mild heating conditions and the antigenicity was relatively high;when the heating intensity increased(70 ℃ for 25 min or 75 ℃ for 2... 相似文献
117.
Baole Lu Haowei Chen Jiaxi Guo Renjian Zhang Zhaoyu Ren 《Optics Communications》2011,284(7):1941-1944
A dual-wavelength laser at 1064 nm and 1319 nm is obtained by a single Nd:YAG crystal rod. On the basis of 1064 nm and 1319 nm dual-wavelength laser installation, the second harmonic waves at 532 nm and 660 nm can be achieved by using non-linear frequency conversion technology. When 1064 nm and 1319 nm lasers oscillate simultaneously, the maximum output power is 30.5 W and 8.78 W, respectively. When the 1319 nm laser is restrained, we obtain a 35.6 W maximum output power at 1064 nm and by contrary 11.2 W at 1319 nm. The maximum output powers of 532 nm and 660 nm lasers are 5.34 W and 1.353 W when oscillating simultaneously. With one of them restrained, the maximum output power is 6.72 W at 532 nm and 1.90 W at 660 nm. The optimum repetition rate of the acousto-optic Q-switch is 10.5 KHz and 20.5 KHz for 532 nm and 660 nm lasers, respectively. The optical-to-optical conversion efficiency from the fundamental waves to the harmonic waves is 17.5% and 15.4%. The instability is less than 2%. 相似文献
118.
An experimental and simulation investigation regarding the effect of various CRAMPS parameters (delays interleaved with the decoupling shape, z-rotation symmetry and offset frequency) on the DUMBO decoupling performance is presented using two model compounds, glycine and tyrosine·HCl. Although the conclusions of this work may be extended to the other homonuclear-decoupling schemes, this work focuses essentially on the effect of adding interleaved delays to DUMBO decoupling during the indirect dimension using different 2D pulse-scheme architectures. While the simulations revealed an increasing loss of the spectral resolution with longer delays (from 0 to 6 μs), the experimental 2D (1)H DUMBO NMR correlation spectra revealed that the inclusion of delays, during the indirect dimension, improves the (1)H resolution whether the z-rotation symmetry was used or not. The best experimental spectra are obtained when z-rotation symmetry and windows are combined. 相似文献
119.
荧光核酸碱基类似物的设计合成是众多研究领域的热点课题. 本文利用密度泛函理论(DFT)和含时密度泛函理论(TDDFT)考察了新型鸟嘌呤类似物y-鸟嘌呤(yG-t1) 及其五个异构体(yG-t2到yG-t6)的结构性质、电子性质和光谱性质, 同时考察了甲醇溶剂和碱基配对对其光谱性质的影响. 研究表明, 气相中y-鸟嘌呤的标准结构并不是最稳定的结构, 其具有三个能量相近的异构体, y-鸟嘌呤最有可能以这三种形式存在. 光谱性质研究表明y-鸟嘌呤的最大吸收波长比天然鸟嘌呤大得多, 人们可以对其进行选择性激发. y- 鸟嘌呤的标准结构与其异构体显示出不同的光谱特性, 因此可以利用其电子光谱指纹对它们进行区分. 研究发现甲醇溶剂将使y-鸟嘌呤标准结构的最大吸收波长和荧光发生蓝移, 而使其他异构体相应值发生红移; 与胞嘧啶配对将使yG-t1, yG-t2, yG-t5 和yG-t6的最大吸收波长和荧光波长发生蓝移, 表明y-鸟嘌呤的电子光谱性质受环境影响较大. 相似文献
120.
Temperature or strain induced adjustable-chirp characteristics of uniform fibre grating with tapered metal coating 下载免费PDF全文
Temperature and strain characteristics of uniform fibre grating with
tapered metal coatings have been analysed theoretically, by which
adjustable chirp characteristics of such gratings are shown.
Electroplating is adopted to fabricate such gratings, and the tapered
metal coating is obtained by gradually drawing the fibre grating out
of the solution during the process of electroplating. The gradually
changing cross-sectional area of the metal coating is calculated by a
newly suggested numerical method. By combining the theoretical and
numerical simulation analyses, the gratings' characteristics are
given at various temperatures and strains. The results obtained using
such a method are also testified by experiments. 相似文献