研究性物理实验与大学生创新心理品质培养

文章提出了大学研究性物理实验与创新心理品质培养的主题,介绍了大学研究性物理实验的特点,论述了大学研究性物理实验对大学生创新心理品质的影响。     

A New Type of Terahertz Waveguides

A new type of THz waveguides, which employs a solid polyethylene rod as the core and polyethylene tubes in a periodic array of square lattice as the cladding, is proposed. Optical properties of this new THz waveguide, especially in dispersion, confinement loss and single mode property, are investigated in detail with the plane wave expansion method and the beam propagation method. Numerical results demonstrate that the new THz waveguide can reach not only low dispersion but also low confinement loss at single mode propagation. Therefore, the square lattice structure is a better candidate as THz waveguides than the triangular ones.     

Sparse polynomials, redundant bases, gauss periods, and efficient exponentiation of primitive elements for small characteristic finite fields

Gauss periods give an exponentiation algorithm that is fast for many finite fields but slow for many other fields. The current paper presents a different method for construction of elements that yield a fast exponentiation algorithm for finite fields where the Gauss period method is slow or does not work. The basic idea is to use elements of low multiplicative order and search for primitive elements that are binomial or trinomial of these elements. Computational experiments indicate that such primitive elements exist, and it is shown that they can be exponentiated fast.     

Hybrid reordering strategies for ILU preconditioning of indefinite sparse matrices

Incomplete LU factorization preconditioning techniques often have difficulty on indefinite sparse matrices. We present hybrid reordering strategies to deal with such matrices, which include new diagonal reorderings that are in conjunction with a symmetric nondecreasing degree algorithm. We first use the diagonal reorderings to efficiently search for entries of single element rows and columns and/or the maximum absolute value to be placed on the diagonal for computing a nonsymmetric permutation. To augment the effectiveness of the diagonal reorderings, a nondecreasing degree algorithm is applied to reduce the amount of fill-in during the ILU factorization. With the reordered matrices, we achieve a noticeable improvement in enhancing the stability of incomplete LU factorizations. Consequently, we reduce the convergence cost of the preconditioned Krylov subspace methods on solving the reordered indefinite matrices.     

NiTi合金中马氏体相的低频力学谱研究

我们用最近研制成功的LMA型低频力学谱测试系统对NiTi合金马氏体相进行了在很大频率范围内（0．003～1Hz）的低频等温力学谱和温度谱的测量．我们研究的形状记忆合金NiTi（Ni50．2at％）试样长34mm，直径1mm细丝．经一定热处理，分别在333K．343K和353K做了内耗随频率的变化的测量。实验表明：频率越小，内耗越大，也就是内耗随频率减少而增大。同时我们采用阶梯升温的方法在八个温度下每个温度测量三种频率（1Hz，0．1Hz，0．01Hz）的内耗，结果清楚地表明：不同频率下，内耗峰都出现在372K（99℃）。而且频率越低，峰高越高。这是具有相变峰的特点：相变峰的峰温不随测量频率不同而变化，相变峰高度随频率减少而增大。我们还测量了在1Hz与0．5Hz频率下内耗随温度的变化。本文用马氏体相的位错理论初步讨论了上述实验结果。     

Remote stereocontrol by the sulfinyl group: Mukaiyama aldol reactions of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde in the asymmetric synthesis of β-hydroxyacids and 1,3-diols

(S)-2-[2-(p-Tolylsulfinyl)phenyl]acetaldehyde reacts with different O-silylated ketenethioacetals in the presence of Yb(OTf)₃ yielding β-hydroxythioesters in high yields and diastereoselectivities. The obtained compounds were readily transformed into β-hydroxyacids and their corresponding diols. These Mukaiyama aldol reactions are a direct evidence of the ability of the sulfinyl group to control 1,5- and 1,6-asymmetric induction processes.     

溴酸钾-亚甲蓝催化光度法测定硝酸盐和亚硝酸盐

用镉柱将NO-3 还原为NO-2 ,利用在磷酸介质中NO-2 对溴酸钾氧化亚甲蓝这一褪色反应具有强烈的催化作用而建立了同时测定痕量硝酸盐和亚硝酸盐的新方法。本方法简便、快速、灵敏 ,对亚硝酸盐和硝酸盐测定的线性范围分别为 0～ 2 0 0 μg·L-1和 0 0 0 3～ 310 μg·L-1,用于测定各种水样中痕量NO-2 和NO-3 的含量均获得满意结果     

时间分辨光子计数系统的研究和应用

对由SPCM-AQR-14和MCS组成的时间分辨光子计数系统进行了研究,分析了SPCM和MCS的工作原理及主要特性.利用该系统对磷光物质和洋葱的延迟发光进行了测量,对它们的光子计数率曲线进行拟合,发现其光强衰减符合双曲线规律.     

Modified gravity on the brane and dark energy

We analyze the dynamics of an AdS₅ braneworld with matter fields when gravity is allowed to deviate from the Einstein form on the brane. We consider exact five-dimensional warped solutions which are associated with conformal bulk fields of weight –4 and describe on the brane the following three dynamics: those of inhomogeneous dust, of generalized dark radiation, and of homogeneous polytropic dark energy. We show that, with modified gravity on the brane, the existence of such dynamical geometries requires the presence of non-conformal matter fields confined to the brane.