Energy spectrum of multi-radiation of X-rays in a low energy Mather-type plasma focus device

The multi-radiation of X-rays was investigated with special attention to their energy spectrum in a Mather-type plasma focus device （operated with argon gas）. The analysis is based on the effect of anomalous resistances. To study the energy spectrum, a four-channel diode X-ray spectrometer was used along with a special set of filters. The filters were suitable for detection of medium range X-rays as well as hard X-rays with energy exceeding 30 keV. The results indicate that the anomalous resistivity effect during the post pinch phase may cause multi-radiation of X-rays with a total duration of 300 ± 50 ns. The significant contribution of Cu-Kα was due to the medium range X-rays, nonetheless, hard X-rays with energies greater than 15 keV also participate in the process. The total emitted X-ray energy in the forms of Cu-K and Cu-K/3 was around 0.14 ± 0.02 （J/Sr） and 0.04 ±0.01 （J/Sr）, respectively. The total energy of the emitted hard X-ray （〉 15 keV） was around 0.12± 0.02 （J/Sr）.     

小问题 大作用

习题教学是课堂教学的重要组成部分，机械式的习题教学满足于较对答案，套题型，将学生的思维引向生搬硬套；开放性的习题教学能启迪学生的思维，引导学生们从不同角度出发推敲问题（横看成岭侧成峰），从解题错误出发拷打问题（柳暗花明又一村），从联想引申出发生成问题（绿叶成阴子满枝）．一些不起眼的小问题在教师的精心设计下能释放大能量，起到大作用，有效提升学生的思维水平．     

Linear and Nonlinear Optical Absorptions of a Donor Impurity in Spherical Quantum Dots

An investigation of the optical properties of a hydrogenic donor in spherical parabolic quantum dots has been performed by using the matrix diagonalization method. The optical absorption coefficient between the ground （L = 0） and the first excited state （L = 1） have been examined based on the computed energies and wave functions. The results are presented as a function of the incident photon energy for the different values of the confinement strength. These results show the effects of the quantum size and the impurity on the optical absorption coefficient of a donor impurity quantum dot.     

Precision measurements of strangeness photoproduction at threshold energies with the Crystal Ball at MAMI-C

The photoproduction of K＋ mesons from the nucleon provides important constraints on the nucleon excitation spectrum and at threshold energies challenges effective field theories based on chiral perturbation in the strange quark sector. Preliminary cross-section measurements for γ（P, K＋）A are presented at an unprecedented beam energy resolution. The data was collected at the MAMI-C facility in Mainz using the Crystal Ball Detector. A new method of K＋ detection was used in which the K＋ is tagged from its weak decay products in the detector crystals. This technique has application with other calorimeters at present and future hadron facilities.     

ETER中子通量监测器的中子学计算

对ITER中子通量监测器（NFM）建立了简化模型并进行了计算分析。利用MCNP程序模拟计算了具有不同慢化剂材料，类型的NFM的探测效率能量响应和时间响应，通过对结果的分析确定了不同NFM上所使用的慢化剂种类及其用量，同时给出了对ITER NFM的初步物理认识。     

纳米粒子在方管中传输与沉降的研究

采用有限体积法离散并应用Simple方法对方截面弯曲管道内的纳米粒子传输和沉降进行了数值计算,结果表明Reynolds数和Schmidt数是影响纳米粒子传输和沉降的重要参数。粒子较小时,弯管中轴向速度较大的区域就是粒子的高浓度区域,沉降增强因子最大值出现在外弯侧的中心位置;粒子较大时,截面浓度的梯度值降低,沉降增强因子趋于平均,此时整个截面的粒子平均沉降。弯曲作用对于粒子较大且Dean数也较大时的影响更加明显。     

高等学校化学学报第31卷(1～12期)学科分类目次

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定性分析法在含有数值判断题分析中的作用

对含数值的判断题,先根据物理规律列出方程,然后把具体数值代入方程,用计算的结果可以做出精确的判断.一般情况下,对于含数值的判断题用计算的方法是行之有效的.但在有的情况下,所给的数值之间具有倍数关系,是巧合,还是隐藏"天机"?笔者发现,若能根据数值之间的倍数关系,采用定性