Variational iteration method for solving compressible Euler equations

This paper applies the variational iteration method to obtain approximate analytic solutions of compressible Euler equations in gas dynamics.This method is based on the use of Lagrange multiplier for identification of optimal values of parameters in a functional.Using this method,a rapid convergent sequence is produced which converges to the exact solutions of the problem.Numerical results and comparison with other two numerical solutions verify that this method is very convenient and efficient.     

Photoluminescence and field-emission properties of Cu-doped SnO2 nanobelts

By using a thermal evaporation and condensation method, Cu-doped SnO₂ nanobelts were synthesized on silicon substrate. High-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy studies of Cu-doped SnO₂ nanobelts demonstrate that the nanobelts are single-crystal structures and Cu is homogeneously doped into the SnO₂ lattice. X-ray diffraction further confirmed the single-phase nature of these nanobelts. The photoluminescence measurements of the nanobelts and samples annealed in oxygen were measured from 77 K to 300 K. Field-emission measurements demonstrated that the Cu-doped nanobelts possessed good performance with a turn-on field of ∼2.9 V/μm and a threshold field of ∼4.8 V/μm.     

利用恒星辐射测量整层大气透过率的多目标星定标

介绍了整层大气透过率测量仪及其测量原理和Langley-Plot定标方法,提出了基于恒星整层大气透过率仪测量大气透过率的多目标星定标方法,并分别进行了K,A光谱类型恒星定标试验,得到了基于K,A两种光谱类型恒星辐射的定标值。对多目标星定标方法与单颗恒星的Langley-Plot定标方法进行了对比实验,验证了多目标星定标方法的合理性与准确性。当实时测量同类型的恒星辐射整层大气透过率时,就可以根据对应的定标参数进行测量研究。     

基于原始波形测量的脉冲电场探测器

介绍了脉冲电场微分测量和原始波形测量的基本原理,设计研制了一系列不同灵敏度的脉冲电场原始波形测量系统,分析了脉冲电场探测器的理论修正模型。该测量系统主要包括天线模块、积分器模块、放大和驱动模块以及光电传输模块,利用同轴型TEM小室对测量系统进行了时域标定。结果表明:测量系统的前沿响应时间小于1.0 ns,系统输出脉冲平顶在10.0μs内下降不超过5%,测量系统输出幅度与电场强度在20 dB的动态范围内呈线性关系,该系列探测器可以用来测量最小10 V/m、最大100 kV/m的电场强度,满足高空电磁脉冲标准环境的测量要求。     

密闭微波消解-电感耦合等离子体质谱法测定烟用香精中多种微量元素

烟用香精对卷烟的香、吃味和质量稳定有重要影响,为了有效控制香精质量,降低卷烟主流烟气中有害元素的含量,采用密闭微波消解-电感耦合等离子体质谱法同时测定了烟用香精中铍、钒、铬、锰、镍、铜、锌、砷、硒、锶、钼、镉、铊和铅14种元素,方法的线性相关系数0.999 5~1.000 0,相对标准偏差1.3%~9.5%(n=5),检出限0.003~0.13μg.L-1,加标回收率88.1%~109.3%。结果表明方法能够满足微量元素的分析要求。用实验方法测定了38个牌号烟用香精中铍、钒等14种元素的含量。结果发现:(1)香精中锰、锌、锶的含量较高,硒、镍、铬、铜次之,铍、铊、钼、镉、钒、铅和砷的含量最低,其平均值均小于0.1μg.g-1。(2)锰、镉、锶的含量在不同香精之间差别较大,其变异系数分别为276.4%,238.7%,243.8%。     

Two-mode vibration control of a beam using nonlinear synchronized switching damping based on the maximization of converted energy

In this paper, a new switch control strategy based on an energy threshold is proposed for the synchronized switch damping techniques in multimode control. This strategy is derived from the total converted energy of a synchronized switch damping (SSD) system in a given time window. Using the new strategy the voltage is inverted only at those extrema where the effective distance, which is proportional to the converted energy between two neighboring extrema, exceeds the threshold. The new switch control strategy is used in both the synchronized switch damping on inductor (SSDI) technique and the synchronized switch damping on voltage source (SSDV) technique, which are applied to the two-mode control of a composite beam. Their control performances are compared with those of the single-mode control and those of classical SSDI and SSDV techniques in two-mode control. The experimental results show that voltage inversion is prevented at some of the displacement extrema to increase the total converted energy, and exhibit better global damping effect than classical SSDI and classical SSDV, respectively. In single mode, the best control performance is achieved when the voltage is inverted at every extremum. But in multimodal control, the total converted energy in a given time window is increased and the control performance is improved when some extrema are skipped.     

Product measurements and fully symmetric measurements in qubit-pair tomography: A numerical study

State tomography on qubit pairs is routinely carried out by measuring the two qubits separately, while one expects a higher efficiency from tomography with highly symmetric joint measurements of both qubits. Our numerical study of simulated experiments does not support such expectations.     

Multilayer growth of BaTiO3 thin films via pulsed laser deposition: An energy-dependent kinetic Monte Carlo simulation

An energy-dependent kinetic Monte Carlo approach was proposed to simulate the multilayer growth of BaTiO₃ thin films via pulsed laser deposition, in which the four steps, such as the deposition of atoms, the diffusion of adatoms, the bonding of adatoms, and the surface migration of adatoms, were considered. Distinguishing with the traditional solid-on-solid (SOS) model, the adatom bonding and the overhanging of atoms, according to the perovskite structure, were specially adopted to describe the ferroelectric thin film growth. The activation energy was considered from the interactions between the ions, which were calculated by Born-Mayer-Huggins (BMH) potential. From the simulation the relative curves of the each layer coverage and roughness vs total coverage were obtained by varying the parameter values of the incident kinetic energy, laser repetition rate and mean deposition rate. The relationship between growth modes and the different parameters was also acquired.     

Element segregation on the surfaces of pure aluminum foils

The surface segregation trend of trace elements in pure aluminum foils was investigated by density functional theory. The model of nine-layer Al(1 0 0) slab substituted partially by trace element atoms was proposed for calculating surface segregation energy. The calculating results show that (i) B, Mg, Si, Ga, Ge, Y, In, Sn, Sb, Pb and Bi exhibit negative segregation energy and possibly move to the surface, while Be, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zr exhibit positive segregation energies and migrated into the bulk; (ii) the segregation energy was found to be related with the covalent radius, the relaxed position at the surface of the substituting atom and the surface energy; (iii) the segregation behavior of trace element generates lots of defects and dislocation, which can increase the initial pitting nucleation sites in the surface of aluminum foils; (iv) the impurity atom concentration was tested with Pb-doped surfaces, the calculated negative segregation energies in all coverage increases rapidly with the Pb coverage. These conclusions are helpful for designing of the chemical composition and to advance the tunnel etching of aluminum foils.     

The 60° or 180° twinned Bi-doped PbTe film studied by EBSD

The Bi-doped PbTe film was grown on Si(1 1 1) substrate by using hot wall epitaxy (HWE) technique. The film was characterized by means of scanning electron microscopy, micro-area X-ray diffraction and electron backscatter diffraction (EBSD). The results indicate that the film is dominated by 〈1 1 1〉 orientation. The film consists of two twinned domains, rotated 60° or 180° around the normal to the film surface. It is speculated that the twinned PbTe film results from the deviated triangular grains. The ratio between the grains with two different orientations will decrease with the increase of the film thickness.