The way to high-performance single nanowire photodetectors: problems and prospects

<正>As potential building blocks for micro-nano devices,one-dimensional semiconductor nanowires(NWs)have been widely studied in recent decades.Due to limited dimension and large surface-to-volume ratio,devices based on NWs are more likely to exhibit unique properties.NW photodetectors adopting different materials have been fabricated.However,the performance is greatly affected by several issues such as lattice quality,surface homogeneity,contact electrodes and     

PIXE应用于分析Si基片热扩Ni的深度分布

本文报告了PIXE(Proton Induce X-ray Emission)技术分析Si基片热扩Ni的深度剖面,质子能量为0.7至2.5MeV,比较了两种理论计算结果的差异,并与其它测量方法得的结果作了比较。     

Sound speed in bubble film of ship wakes

As is distinct from general gas-liquid two-phase flow, a large number of bubbles with different diameters belong to ship wakes. Feasibility of Laplace equation, used to calculate wake sound speed (WSS), is confirmed based on differential postulation. Defect for calculating the adiabatic sound speed of gases in references is showed, and a concept of WSS is proposed clearly. A minimum WSS of 24.5 m/s is got when bubble ratio reads 0.5 according to the calculation when bubble dimension is less than that of resonance. Also a weak dependence of WSS on pressures is predicted. WSS from calculation corresponds with the experimental data of references well in high frequency domain, when the actual scale of bubbles is greater than the resonant scale. Supported by the National Natural Science Foundation of China (Grant No.10274046) and Pre-study Fund of Military Equipment (Grant No. 51448030101ZK1801)     

Quasi-variational principles of single flexible body dynamics and their applications

The reasons for studying single flexible body dynamics are that on one hand, it is the basis of flexible multi-body dynamics. If the theory of the single flexible body dynamics has been deeply studied, the theory of flexible multi-body dynamics will be researched easily. On the other hand, it has its unique and important applications. Quasi-variational principle of non-conservative single flexible body dynamics is established under the cross-link of particle rigid body mechanics and deformable body mechanics. Taking the interceptor as an example, this paper has explained the physical meaning of the quasi-stationary value condition of the quasi-variational principle in non-conservative single flexible body dynamics. Taking the launch of rocket as an example, it has illustrated the features of “one force for two effects” in a single flexible body dynamics. With an example of the extending flexible beam coupled with the spacecraft attitude, it has shown the transition from the single flexible body dynamics to the flexible multi-body dynamics. Finally, a number of related problems are discussed. Supported by the National Natural Science Foundation of China (Grant No. 10272034), the Doctoral Education Foundation (Grant No. 20060217020), and the Natural Science Foundation of Harbin Engineering University (Grant No. HEUF04003)     

The physics design of magnet in 14 MeV cyclotron

The 14 MeV, 400 μA compact cyclotron is under construction at China Institute of Atomic Energy (CIAE). The design of main magnet and the result of beam dynamics in the cyclotron will be described in this paper, including the choice of main parameters of magnet, the method of shimming isochronous field in the compact cyclotron and optimization of the magnetic field in central region. The beam will be accelerated to 14.6 MeV by optimizing the magnet structure.

     

Planar graphs with maximum degree 8 and without intersecting chordal 4-cycles are 9-totally colorable

The minimum number of colors needed to properly color the vertices and edges of a graph G is called the total chromatic number of G and denoted by χ’’ (G). It is shown that if a planar graph G has maximum degree Δ≥9, then χ’’ (G) = Δ + 1. In this paper, we prove that if G is a planar graph with maximum degree 8 and without intersecting chordal 4-cycles, then χ ’’(G) = 9.     

KAM tori for higher dimensional beam equation with a fixed constant potential

In this paper, we consider the higher dimensional nonlinear beam equation:utt + △2u + σu + f(u)=0 with periodic boundary conditions, where the nonlinearity f(u) is a real-analytic function of the form f(u)=u3+ h.o.t near u=0 and σ is a positive constant. It is proved that for any fixed σ>0, the above equation admits a family of small-amplitude, linearly stable quasi-periodic solutions corresponding to finite dimensional invariant tori of an associated infinite dimensional dynamical system.     

A Modular Framework for Quantum-Proof Randomness Extractors

A quantum-proof extractor is a function that is used to extract randomness from any weakly random source X in the presence of prior quantum information about X. It is known that some constructions are quantum-proof, such as Trevisan’s construction. However, these extractors are generally restrictive for applications on the one-bit output construction and the weak design. Here, we give a modular framework to combine multi-bit output extractors (not only one-bit) with pseudorandom transform, and show that it is sound in the presence of quantum side information. Then combined with the theory of operator spaces, we improve previous theoretical proofs, and discuss the security of two-bit output extractor by giving a tighter bound for it.     

Deformation behavior of Fe-based bulk metallic glass during nanoindentation

Fe-based bulk metallic glasses (BMGs) normally exhibit super high strength but significant brittleness at ambient temperature. Therefore, it is difficult to investigate the plastic deformation behavior and mechanism in these alloys through conventional tensile and compressive tests due to lack of distinct macroscopic plastic strain. In this work, the deformation behavior of Fe₅₂Cr₁₅Mo₉Er₃C₁₅B₆ BMG was investigated through instrumented nanoindentation and uniaxial compressive tests. The results show that serrated flow, the typical plastic deformation feature of BMGs, could not be found in as-cast and partially crystallized samples during nanoindentation. In addition, the deformation behavior and mechanical properties of the alloy are insensitive to the applied loading rate. The mechanism for the appearance of the peculiar deformation behavior in the Fe-based BMG is discussed in terms of the temporal and spatial characteristics of shear banding during nanoindentation. Supported by the National Natural Science Foundation of China (Grant Nos 50571109, 10572142 and 56771102) and the National Basic Research Program of China (973 Program)(Grant No 2007CB613900)