共查询到20条相似文献,搜索用时 78 毫秒
1.
The depolarized component of Paman scattering by pure liquid HCl and DCl and of solutions of these acid halides in liquid CO2 are reported. At room temperature the band contours show no S branch intensity in pure acid halide liquid, but in solution in liquid CO2 and S branch is increasingly evident with increasing CO2 concentration. The frequency shifts are a function of the dielectric constant and refractive index of the solution. Reorientational correlation functions calculated from the anisotropic scattering decay more slowly in the first few tens of femtoseconds than predicted for monomeric acid halides, suggesting contribution to the composite correlation function by species of larger moments of inertia but vibrational frequencies identical with those of the monomers. 相似文献
2.
3.
Wintersweet Branch‐Like C/C@SnO2/MoS2 Nanofibers as High‐Performance Li and Na‐Ion Battery Anodes
下载免费PDF全文
![点击此处可从《Particle & Particle Systems Characterization》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Huimin Zhou Xin Xia Pengfei Lv Jin Zhang Zengyuan Pang Dawei Li Yibing Cai Qufu Wei 《Particle & Particle Systems Characterization》2017,34(12)
Structure and morphology of molybdenum disulfide (MoS2) play an important role in improving its reversible lithium storage and sodium storage as anodes. In this study, a facile method is developed to prepare C/C@SnO2/MoS2 nanofibers with MoS2 nanoflakes anchoring on the core–shell C/C@SnO2 nanofibers through hydrothermal reaction. By adjusting the concentration of MoS2 precursors, the synthesized MoS2 with different slabs dimensions, size, and morphologies are obtained, constituting budding and blooming wintersweet branch‐like composite structure, respectively. Owing to scattered MoS2 nanoparticles and sporadic MoS2 nanoflakes, the budding wintersweet branch‐like composite nanofibers processes less slabs of staking in number and large specific surface area. Benefiting from the exposed C@SnO2 shell layer, the synergistic effect among SnO2, carbon, and MoS2 is strengthened, which maximizes the advantage of each material to exhibit stable specific capacities of 650 and 230 mAh g?1 for Li‐ion batteries and Na‐ion batteries after 200 cycles. 相似文献
4.
5.
6.
7.
Tang SK 《The Journal of the Acoustical Society of America》2004,115(1):218-227
The sound transmission characteristics of a Tee-junction formed by a sidebranch and an infinitely long duct are investigated numerically using the finite element method. The associated corrections of the branch length and the upstream duct length are also discussed in detail. The types of branch resonance that result in strong or weak sound transmission across the junction are determined and their effects on the length corrections examined. Results suggest that the type of sidebranch, the branch width, the branch length, and the order and the form of the resonance affect more significantly the length corrections of the duct section. The excitation of nonplanar higher branch modes gives rise to rapid increase in the duct length corrections and also results in lower sound transmission. 相似文献
8.
We have analyzed a single vortex at T=0 in a 3D superfluid atomic Fermi gas across a Feshbach resonance. On the BCS side, the order parameter varies on two scales: k(F)(-1)and the coherence length xi, while only variation on the scale of xi is seen away from the BCS limit. The circulating current has a peak value jmax which is a nonmonotonic function of 1/k(F)a(s) implying a maximum critical velocity approximately v(F) at unitarity. The number of fermionic bound states in the core decreases as we move from the BCS to the BEC regime. Remarkably, a bound state branch persists even on the BEC side reflecting the composite nature of bosonic molecules. 相似文献
9.
利用激光大气传输4维程序对激光大气传输相位不连续点的时空演化特征进行了数值计算。仿真计算了相位不连续点随光波传输的产生和湮灭过程,以及某一固定传输位置处,畸变光场内的相位不连续点随时间的变化情况。计算结果表明,相位不连续点是随着波前运动的,并且可以成对地产生或湮灭;当传输路径中的某一位置固定时,垂直于传播方向的畸变光场内的相位不连续点所在的位置随时间的变化是不确定的,但在传输条件一定的情况下,该位置处的相位不连续点数目的统计平均值是可以确定的。 相似文献
10.
The theoretical properties of a composite chiral-plasma medium are developed. By using the reaction theorem for a magnetized
chiroplasma, we obtain the proof of nonreciprocity based upon the constitutive relationships between electromagnetic vectorsE, B, H, D. Using the Maxwell’s equations and the proposed constitutive relations for a chiral-plasma medium, we derive the vectorsE andH and from these equations, dispersion relations andE-field polarizations are based. The obtained results for waves propagating parallel to the external magnetic field in a cold
magnetized chiro-plasma are compared with typical results obtained for a cold plasma. For circulary polarized waves, a new
mode conversion is founded with the chiral effect. The chiral rotation is obtained and compared with the Faraday rotation.
For waves propagating across the magnetic field, we found a shift of the cut-offs of ordinary and extraordinary waves. On
the lower branch of the extraordinary wave mode there is no bands of forbidden frequencies and the reflection point vanishes
when the chiral parameter increases. 相似文献
11.
利用数值方法研究了不同起伏条件下准直激光束在湍流大气中的传播,分析了光斑的分形维数以及相位不连续点数目的统计特征。结果表明:随着起伏条件的增大,光斑的分形维数以及相位不连续点数目增大;光斑的分形维数与锐度(描述光斑质量的参量)有一定的关系,但相位不连续点数目与光斑质量不存在确定的关系。在本文的计算条件下,分形维数一直随起伏条件的增大而增大,没有出现类似于闪烁饱和的现象。在一定的起伏条件下,相位不连续点数目具有一定的统计分布,而不是一个确定的值,并且具有相当的发散性。 相似文献
12.
13.
提出一种可稳定计算Pekeris波导中声场的波数积分方法,并在此基础上开发出一个数值模型,可用于提供Pekeris波导中声场的精确、稳定的数值解。在这个方法中,由于与深度有关的波动方程齐次解中所有的上行波与下行波均采用了合理的归一化表示,从而得到的系统方程是无条件稳定的。在简正波方法中,割线积分一般只对近场有显著影响。因此,传统的简正波模型一般都忽略割线积分对声场的贡献。但是,如果某号简正波离割线非常近,则割线积分对非常远距离的声场仍可能有显著影响。在这种情况下,传统的简正波模型由于忽略割线积分的贡献,从而得到的声场结果是不准确的。本文通过数值算例比较本文提出的波数积分模型与传统的简正波模型。数值结果表明,本文提出的模型可以提供精确、稳定的Pekeris波导中声场的数值解,而在某些情况下传统的简正波模型得到的声场结果是不准确的。因此,本文提出的模型可以作为Pekeris波导中声传播问题的标准模型使用。 相似文献
14.
As there may be some branches in long enclosures, such as high-speed railway and freeway tunnels, it will make a difference in the sound propagation in long enclosures if we give more consideration to different designs of the branches at the onset of their construction. However, most researches on the sound propagation in long enclosures available are concerned with straight long enclosures. In this paper, the sound pressure level (SPL) attenuation, early decay time (EDT), and reverberation time (RT30) of long enclosures with a vertical or inclined branch of different dimensions have been studied by comparing experimental results from physical scale models of such enclosures with those of the straight long enclosure. This experimental investigation gives interesting results on the behavior of sound propagation in long enclosures with a vertical or inclined branch of different dimensions. When conducting engineering design for long tunnels of the high-speed railway or freeway, it would be appropriate to consider designing the branch of the tunnels into a widened left inclined or right inclined one to provide a better relative SPL than that of other branches with different dimensions. This study further reveals that with an inclined branch of different dimensions, the EDT of the long enclosure will be different. At both 500 and 1000 Hz 1/3 octave bands, the EDT is the shortest when the long enclosure has a left inclined branch and an extended left inclined branch, while the EDT is the longest when the long enclosure has a widened vertical branch. Generally speaking, in the near field (i.e. the source-receiver distance is shorter than the threshold distance), the EDT measurements are similar, while in the far field (i.e. the source-receiver distance exceeds the threshold distance), the EDT is the longest for the straight long enclosure, second longest for the long enclosure with a widened inclined branch, third longest for the long enclosure with a vertical branch, and the shortest for the long enclosure with an extended inclined branch, which is similar to the trend with RT30. 相似文献
15.
D. Tonon B.J.T. Landry J.F.H. Willems A. Hirschberg 《Journal of sound and vibration》2010,329(8):1007-5912
Corrugated pipes are widely used because they combine local rigidity with global flexibility. Whistling induced by flow through such pipes can lead to serious environmental and structural problems. The whistling of a multiple side branch system is compared to the whistling behavior of corrugated pipes. The study has been restricted to cavities with sharp edges which are convenient for theoretical modeling. The side branch depth is chosen to be equal to the side branch diameter, which corresponds to cavity geometries in typical corrugated pipes. The low frequency resonance modes of the multiple side branch system have been predicted by means of acoustic models, of which the validity has been tested experimentally. Several experiments have been carried out for characterizing the whistling behavior of the system. While the behavior of a multiple side branch system is interesting on its own it can be compared to that of corrugated pipes. These experiments show that the multiple side branch system is in many aspects a reasonable model for corrugated pipes. Advantage of the multiple side branch system is that it is an experimental setup allowing easy modification of cavity depth. We used this feature to identify the pressure nodes of the acoustic standing wave along the main pipe as the regions where sound is produced. This contradicts recent publications on corrugated pipes. Another interesting aspects is that the system appears to whistle at the second hydrodynamic mode of the cavities rather than at the first hydrodynamic mode. A prediction model for the whistling behavior is proposed, consisting of an energy balance, based on the vortex sound theory. The model predicts the observed Strouhal number but overestimates the acoustic fluctuation amplitude by a factor four. 相似文献
16.
An approach of separating individual wave arrivals for a dipole logging is presented. The branch points are treated as a type
of logarithm and the Riemann surface structure of the multivalued function is studied, that is, the displacement potential
within the borehole. Based on the theoretical analysis, the complex poles contributing to the wave field on various Riemann
sheets are investigated in detail for the case of a fast formation. It is shown that poles on Riemann sheet (0,0) are real
and form branches of modes with dispersion. Mathematically, it is demonstrated that the flexural mode has no cutoff frequency,
which is different from the traditional point of view. Poles on other relevant Riemann sheets are complex and form many branches
on the complex frequency-wavenumber plane. Further investigation on the pole and branch cut contributions indicates that the
vertical branch cut integration method has limitations in separating wave arrivals. By properly taking into account the complex
poles on various Riemann sheets together with branch cut integrations, wave arrivals are separated from the full waveforms
effectively for both the fast and slow formation models. Specially, there are complex poles on Riemann sheet (0,−1) in the
vicinity of the compressional branch cut for a slow formation with a large Poisson’s ratio, which have small imaginary parts
and contribute a lot to the p-wave arrival.
Supported by the National Natural Science Foundation of China (Grant No. 10534040) 相似文献
17.
18.
用相场法模拟了过冷纯物质二次枝晶的生长过程,并定量地研究了过冷度、各向异性、热扰动振幅等参数对二次枝晶的影响. 通过加入热扰动,相场法能更真实地模拟过冷熔体中二次枝晶的生长,计算得到的二次枝晶间距和幅值与由Wentzel_Kramers_Brillouin方法得到的结果符合较好. 模拟结果表明,过冷度和各向异性对二次枝晶有较大影响. 当过冷度增大时,二次枝晶间距随之减小;当各向异性增大时,二次枝晶间距随之增大,但二次枝晶幅值则随之减小. 热扰动振幅主要影响二次枝晶幅值,而对二次枝晶间距影响较弱.
关键词:
相场法
热扰动
枝晶生长
二次枝晶 相似文献
19.
A consistent tanh expansion (CTE) method is developed for the dispersion water wave (DWW) system. For the CTE solvable DlVVC system, there are two branches related to tanh expansion, the main branch is consistent while the auxiliary branch is not consistent. From the consistent branch, we can obtain infinitely many exact significant solutions including the soliton-resonant solutions and soliton-periodic wave interactions. From the inconsistent branch, only one special solution can be found. The CTE related nonlocal symmetries are also proposed. The nonlocai symmetries can be localized to find finite Backlund transformations by prolonging the model to an enlarged one. 相似文献
20.
Time-resolved infrared absorption features in the 1800–2400 cm?1 region during a typical cycle in the oscillatory oxidation of CO over a platinum foil were obtained by Fourier transform infrared reflection absorption spectroscopy. Pretreatment of the foil in an oxidizing environment at high temperatures was found to be necessary to induce large-amplitude, stable oscillations. The oscillations are approximately square-wave in shape, with a high and a low reaction-rate branch. The level of chemisorbed CO in the high reaction-rate branch is typically below the noise level, while in the low reaction-rate branch substantial substantial surface coverages of CO can be observed. No evidence for CO bridge-bonded to the platinum substrate or chemisorbed in the presence of a subsurface Pt oxide could be found at any time during the oscillation cycle. Evidence is presented for the existence of CO islands in the low reaction-rate branch. It is also shown that the low reaction rate realized in this branch is not due to blocking of the surface by chemisorbed CO. 相似文献