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51.
M.F. Luo J.Y. Huang C.I. Chiang G.R. Hu C.C. Wang C.T. Wang C.W. Lin 《Surface science》2009,603(3):558-565
We present a self-organised approach for the synthesis of one-dimensional (1D) arrays of supported nanoclusters. By oxidising NiAl surfaces vicinal to the (1 0 0) plane tilted along the crystallographic direction [0 1 0], we produced ordered thin films of θ-Al2O3 that exhibit uniform protrusion stripes propagating uniquely along direction [0 0 1] of the NiAl. These protrusions are preferential centres for nucleation of metal deposited from a vapour; the nanoclusters grown from such metal are aligned and form massive 1D cluster arrays along direction [0 0 1]. The arrays of Co nanoclusters exhibit a diameter as small as 3 nm and length exceeding a micrometer. The results imply prospective applications for which a patterned assembly of nanoclusters is desired. 相似文献
52.
T. A. Nguyen H. T. Dung 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):173-177
Using the Born expansion of the Green tensor, we consider the
spontaneous decay rate of an excited atom placed in the vicinity of
a rectangular plate. We discuss the limitations of the commonly used
simplifying assumption that the plate extends to infinity in the lateral
directions and examine the effects of the atomic dipole moment
orientation, atomic position, and plate boundary and thickness on the atomic
decay rate. In particular, it is shown that
due to the plate finite size, the spontaneous decay may be inhibited
even when the atom is situated very close to the surface, and that
in the boundary region, the
spontaneous decay rate can be strongly modified. 相似文献
53.
Highly ordered Prussian blue nanowires with diameter of about 50 nm and length up to 4 m have been fabricated by an electrodepositing technology with two-step anodizing anodic aluminum oxide films. The Mössbauer spectra taken between 15 and 300 K indicate that the hyperfine parameters decrease as the temperature increases. The temperature dependence of the quadrupole splitting, the isomer shift and the spectra area are discussed. A decrease of Debye temperature for Prussian blue nanowires was found with respect to that of Prussian blue bulk. 相似文献
54.
Several new constructions for difference matrices are given. One classof constructions uses pairwise balanced designs to develop newdifference matrices over the additive group of GF (q). A second class of constructions gives difference matrices overgroups whose orders are not (necessarily) prime powers. 相似文献
55.
The use of non-contact laser techniques for the generation of ultrasound has extended the limits of the application of traditional ultrasonic techniques. This paper focusses on the use of one such non-contact laser technique, known as ‘optical fibre array’, to generate shear and surface waves. The shear wave experimental directivity pattern results are presented and compared with the theoretical results of a single source and an array source. The experimental directivity results for the surface wave are also presented, and compared with the theoretical results. The data show that the array enhances signal generation in the forward direction for both shear and surface waves. The array gain is also discussed. The receiver for the directivity measurements was a contact piezoelectric transducer. 相似文献
56.
The optimal attitude control problem of spacecraft during its solar arrays stretching process is discussed in the present
paper. By using the theory of wavelet analysis in control algorithm, the discrete orthonormal wavelet function is introduced
into the optimal control problem, the method of wavelet expansion is substituted for the classical Fourier basic function.
An optimal control algorithm based on wavelet analysis is proposed. The effectiveness of the wavelet expansion approach is
shown by numerical simulation.
This work is supported by the National Natural Science Foundation of China. 相似文献
57.
Nonlinear contrast imaging modes such as second harmonic imaging (HI) and subharmonic imaging (SHI) are increasingly important for clinical applications. However, the performance of currently available transducers for HI and SHI is significantly constrained by their limited bandwidth. To bypass this constraint, a novel transducer concept termed multi-frequency harmonic transducer arrays (MFHA's) has been designed and a preliminary evaluation has been conducted. The MFHA may ultimately be used for broadband contrast enhanced HI and SHI with high dynamic range and consists of three multi-element piezo-composite sub-arrays (A-C) constructed so the center frequencies are 4f(A) = 2f(B) = f(C) (specifically 2.5/5.0/10.0 MHz and 1.75/3.5/7.0 MHz). In principle this enables SHI by transmitting on sub-array C receiving on B and, similarly, from B to A as well as HI by transmitting on A receiving on B and, likewise, from B to C. Initially transmit and receive pressure levels of the arrays were measured with the elements of each sub-array wired in parallel. Following contrast administration, preliminary in vitro HI and SHI signal-to-noise ratios of up to 40 dB were obtained. In conclusion, initial design and in vitro characterization of two MFHA's have been performed. They have an overall broad frequency bandwidth of at least two octaves. Due to the special design of the array assembly, the SNR for HI and SHI was comparable to that of regular B-mode and better than commercially available HI systems. However, further research on multi-element MFHA's is required before their potential for in vivo nonlinear contrast imaging can be assessed. 相似文献
58.
59.
使用基于密度泛函理论的第一性原理赝势法和超原胞模型,研究了吸附在Cu(100)表面上的二维有序排列的幻数团簇Nb4的结构稳定性及其电子结构性质.计算表明,四面体结构和平面的菱形结构的Nb4团簇都可以稳定地吸附在Cu(100)表面上,这个体系很可能有重要的应用前景.在Cu(100)表面上,菱形结构的Nb4比四面体结构的Nb4更稳定,从Nb4团簇的四面体结构到菱形结构,需经过的势垒高度约为0.94eV/团蔟.电子结构的计算表明,在Nb4吸附后,Cu(100)表面与Nb4团簇间有明显的电荷重新分布,表面Cu原子的电子态密度也明显改变.
关键词:
4团簇')" href="#">Nb4团簇
有序排列
结构稳定性
从头计算 相似文献
60.
Meg Duroux Leonid Gurevich Esben Skovsen Steffen B. Petersen 《Applied Surface Science》2007,254(4):1126-1130
Ultraviolet light can be used to immobilize biomolecules onto thiol reactive surfaces in order to, e.g., make biosensors. The mechanism involves light-induced formation of free, reactive thiol groups in disulphide containing molecules. This technology allows for the creation of arrays of biomolecules with a high degree of reproducibility, circumventing the need for often expensive nano/micro-dispensing technologies. The ultimate size of the immobilized spots is defined by the focal area of the UV beam. Light-induced immobilization has the added benefit that the immobilized molecules will be spatially oriented and covalently bound to the surface. In this paper, we demonstrate the utility of a sensor array created with the new sensor technology when integrated into a microfluidic system. Protein arrays made using light-induced immobilization showed successful antigen/antibody binding in a flow cell allowing the visualisation of real time binding and enzyme activity. This new technology is ideal for the creation of protein/DNA microarrays, can replace present micro-dispensing arraying technologies and is ideal as a molecular imprinting technology. 相似文献