如何通过测量复摆的周期计算转动惯量

本文给出一种简约可行的方法,用来计算不规则物体绕任意轴转动时的转动惯量,同时,亦可定出质心轴位置.本文讨论的内容对教学有意义.     

电感耦合等离子体发射光谱法检测獭兔肉中的微量元素

研究了用电感耦合等离子体光谱法检测獭兔肉中多种微量元素的实验方法。实验表明,獭兔肉中多种微量元素在选定的最佳条件下能够可靠、准确测得,且精密度在0.59%—8.85%之间,回收率为96.5%—103.5%。该方法具有灵敏度高、干扰少、线性范围宽和多元素同时测定等优点,是科学工作者研究微量元素可行的方法之一;同时该方法准确、快速、简便,适用于同类样品的测定,结果令人满意。     

397 GHz斜注管互作用系统的设计模拟

斜注管是返波振荡器的一种,通过电子注的倾斜,电子距离慢波结构更近,高频场更强,耦合阻抗和互作用效率更高,显著增加输出功率。对带状注斜注管的互作用系统进行了设计,并首次将双排齿慢波结构应用于斜注管。利用电磁模拟软件和3D粒子模拟软件对设计的斜注管的色散曲线和场分布进行了分析,并对其注-波互作用进行了模拟,可以得到大于100 mW的输出功率以及50 GHz的调谐带宽。输出功率在370.5 GHz频点处处达到峰值2.3 W,电子注电压7.0 kV,注电流120 mA,聚焦磁场1.0 T。     

Research on the cyclostationary nearfield acoustic holography based on boundary element method

Cyclostationary sound field is a special kind of nonstationary sound field, in which the pressure signal is modulated seriously and sidebands exist in its spectrum. The reconstructed sound field can＇t figure the cyclostationary features in conventional Nearfield Acoustic Holography （NAH） procedure. On the basis of planar cyclostationary NAH, the cyclostationary NAH based on boundary element method is proposed which can be utilized to analyze radiators with complicated surface. Replacing the Fourier＇s transform with the second-order cyclic statistics, the Cyclic Spectral Density （CSD） functions is used as the reconstructed physical quantity in the proposed NAH technique, instead of the spectrum or power spectral density of pressure signal. By virtue of the demodulation ability of CSD function, the reconstructed CSD can effectively express the information of modulating and carrier wave respectively. The simulation and experiment illustrate that the validity and accuracy of this cyclostationary NAH technique satisfy the request of engineering.     

脉冲X射线剂量率测量不确定度分析

“强光一号”短脉冲高能X射线剂量率测量,主要包括脉冲射线总剂量与脉冲射线时间宽度的测量,前者采用热释光剂量计测量,后者采用PIN半导体探测器记录。根据不确定度传递数学模型,分析了影响X射线剂量和脉冲宽度测量结果的因素。针对“强光一号”短脉冲高能X射线测量,定量地给出了各种因素引入的测量不确定度,总剂量测量是影响剂量率测量准确性的决定性因素,其相对标准不确定度为25.1％,脉冲宽度测量不确定度为3.7％,剂量率测量扩展不确定度为50.8%,置信概率95%。     

An Overview of The Photoacoustic Phase Spectra of Rare Earth Complexes

Abstract

The photoacoustic(PA) amplitude and phase spectra of several kinds of rare earth (RE) complexes are reported and summarized briefly. It is observed that both the amplitude and phase spectra well characterize the different energy levels of the RE complexes. The phase angle of the RE complexes is associated with the relaxation time τ and the optical absorption coefficient β concerning with the π-π? transition and the f-f transitions, respectively. After individual detailed discussion of the phase spectra, a reasonable theoretical consideration is given to interpret the results.     

Plasmonic planar lens based on stack of metal–insulator–metal waveguides with height tuning

We introduce a technique capable of focusing electromagnetic (EM) waves through plasmonic nanoslits symmetrically arranged along the indented semi-circular surface in silver background. The EM transports through the tuning slits in the form of surface plasmon polaritons (SPPs), and gets the required phase retardations to focus at the focal plane. Due to the subwavelength nature of planar metallic lens, we present the rigorous electromagnetic analysis by using two dimensional (2D) finite difference time domain (FDTD) method. These height-modulated slits with uniform width are demonstrated to have unique advantages in beam manipulation. In combination with previous studies, it is expected that our structure with small number of slits could lead to realization of optimum designs of plasmonic nano-lens.     

Optical study of single crystals grown by the Czochralski method from Yb3+-doped (Gd1−x Y x )2SiO5 solid solution

Yb³⁺-doped crystals were grown by the Czochralski method from (Gd_0.5Y_0.5)₂SiO₅ melt employing seeds cut out from single crystals of Yb:Gd₂SiO₅ and Yb:Y₂SiO₅. XRD analysis revealed that the structure of the solid solution crystals grown is consistent with the structure of the seed, namely C2/c for the Yb:Y₂SiO₅ seed and P2₁/c for the Yb:Gd₂SiO₅ seed. Optical absorption spectra, emission spectra and luminescence decay curves were recorded at 10 K and 300 K. Analysis of gathered spectroscopic data made it possible to evaluate radiative transition rates for the ²F_5/2 multiplet of Yb³⁺ in the two structures and to assess crystal field splitting of multiplets involved in radiative transitions. It has been concluded that transition intensities and relaxation dynamics of Yb³⁺ in the systems studied are similar but the intensity distribution of emission and absorption bands depends significantly on the system structure. This feature, combined with inhomogeneous broadening of spectral lines, may be advantageous for the tailoring of lasers employing ytterbium-doped crystals for specific applications.     

The effect of 3-aminopropyltrimethoxysilane on the formation of NiFe2O4/SiO2 nanocomposites

NiFe₂O₄/SiO₂ nanocomposites were prepared using a sol–gel method with the addition of 3-aminopropyltrimethoxysilane (APS). Different phases and morphologies of NiFe₂O₄/SiO₂ nanocomposites were obtained when different amounts of APS were used. The structural properties of the products were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Sheet-like morphology was observed at higher molar ratio of APS to NiFe₂O₄, while spherical NiFe₂O₄/SiO₂ nanoparticles separated from each other were formed at lower molar ratio of APS to NiFe₂O₄. The magnetic properties of the nanocomposites were also investigated, indicating that the interparticle interactions exhibit strong dependence on the molar ratio of APS to NiFe₂O₄.     

Improved multiparty quantum key agreement in travelling mode

The need to simultaneously balance security and fairness in quantum key agreement (QKA) makes it challenging to design a flawless QKA protocol, especially a multiparty quantum key agreement (MQKA) protocol. When designing an MQKA protocol, two modes can be used to transmit the quantum information carriers: travelling mode and distributed mode. MQKA protocols usually have a higher qubit efficiency in travelling mode than in distributed mode. Thus, several travelling mode MQKA protocols have been proposed. However, almost all of these are vulnerable to collusion attacks from internal betrayers. This paper proposes an improved MQKA protocol that operates in travelling mode with Einstein-Podolsky-Rosen pairs. More importantly, we present a new travelling mode MQKA protocol that uses single photons, which is more feasible than previous methods under current technologies.