Result of search for low velocity exotic particles

The L3＋C experiment, taking advantage of the L3 muon magnetic spectrometer, measured the spatial tracks of charged cosmic ray particles to obtain rigidity as well as velocity. One possible low velocity exotic particle is observed. The existing uncertainties are discussed, and the flux upper limit of the low velocity exotic particles from this observation is deduced based on the assumption of a null observation. The result is 6.2×10^-10 cm^-2·s^-1·sr^-1 at 90% confidence level in the velocity range from 0.04c to 0.5c.     

苦豆子不同生育时期矿质元素分析

应用ICP-AES等技术,研究了苦豆子常量、微量矿质元素含量、各部位吸收比例和不同时期的矿质元素需求量。结果显示:(1)成熟期苦豆子常量矿质元素比约为N∶K∶Ca∶Mg∶P∶Na=11.91∶8.27∶7.54∶1.02∶1.00,微量矿质元素比值约为Fe∶Zn∶B∶Cu∶Mn=28.91∶2.12∶1.40∶1.18∶1.00;(2)各器官矿质元素含量因生育时期存在差异,微量元素在营养期茎中总量最高占全株总量的45.6%,而在成熟期种子中最高占全株总量的36.7%。(3)苦豆子在营养期需肥最多,盛花期次之,盛荚期最少。     

撞击流中颗粒碰撞传热理论模型研究

建立了考虑颗粒接触面导热的颗粒碰撞传热模型,相应完善了气固两相撞击流理论模型,并对不同条件的撞击流干燥过程进行了模拟。计算结果与实验结果非常吻合,从而验证了所建模型的正确性。本文还分析了颗粒碰撞传热、加料方式以及喷嘴间距对撞击流干燥性能的影响规律。结果表明:在本文所涉及的撞击流干燥过程中,颗粒碰撞传热对干燥性能的影响并不明显;单边加料时颗粒物料的降水幅度及撞击流装置的干燥强度都明显大于双边加料的工况;喷嘴间距较大时,物料的降水幅度及装置的干燥强度均较大。     

一维新型阶梯函数光子晶体透射特性

研究了阶梯型折射率n22、n11(阶梯分布高度)的大小、对应的分布厚度、不同入射角以及缺陷模对阶梯函数型光子晶体透射特性的影响.由费马原理给出光在函数光子晶体中的运动方程,再由电磁传播理论给出函数光子晶体的传输矩阵,进一步推导出函数光子晶体的透射率以及电场分布的表达式.研究表明,1)随n22,n11大小或者厚度改变,其禁带变宽;2)随光的入射角增加,其禁带变窄;3)当加入缺陷层时,随着缺陷层介质折射率增加,缺陷模强度减小且位置发生红移;4)在函数光子晶体中,缺陷层前电场分布保持不变,而在缺陷层处以及之后的电场强度都明显增强,这不同于常规光子晶体的电场分布仅在缺陷层处局域增强.     

Investigation of add-back effects in a segmented Clover detector

The resolution and the summing characteristics of an EXOGAM segmented Clover germanium detector has been studied for use it in y spectroscopic experiments. The measurements have been performed with standard radioactive sources of ^152Eu, ^133Ba and β-delayed γ-rays from 176Ir decay. The data analytic results, realized by software, are presented in this paper.     

演示实验制作促进动手动脑的大学物理探索式学习的改革尝试

介绍了我们通过制作演示实验装置促进动手动脑的大学物理探索式学习的教学改革实践.详细说明了动手动脑学习的试验过程、试验结果.自制物理演示实验装置给学生提供了一个可以自主选题的探索式学习平台.     

基于Lissajous图技术的波长移相标定方法

波长移相干涉仪可应用于大口径光学元件的检测。研究了基于Lissajous图技术的波长移相标定方法,实现了干涉图间移相量的计算,解决了在不同干涉腔长下进行测试时移相量需控制成为一个特定值的问题。首先通过模拟仿真,验证了方法的正确性;然后编写程序对已知移相量的实际干涉图进行计算。结果表明,在干涉图对比度较好以及对计算的两点选择恰当的情况下,计算出的相对误差在4%范围内。     

Characterization of different-Al-content AlGaN/GaN heterostructures on sapphire

Al x Ga 1-x N/GaN high-electron-mobility transistor (HEMT) structures with Al composition ranging from x = 0.13 to 0.36 are grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The effects of Al content on crystal quality, surface morphology, optical and electrical characteristics of the AlGaN/GaN heterostructures have been analyzed. Although high Al-content (36%) heterostructure exhibits a distinguished photoluminescence peak related to recombination between the two-dimensional electron gas and photoexcited holes (2DEG-h), its crystal quality and rough surface morphology are poor. 2DEG mobility increases with the Al content up to 26% and then it apparently decreases for high Al-content (36%) AlGaN/GaN heterostructure. The increase of sheet carrier density with the increase of Al content has been observed. A high mobility at room temperature of 2105 cm 2 /V s with a sheet carrier density of n s = 1.10 × 10 13 cm -2 , for a 26% Al-content AlGaN/GaN heterostructure has been obtained, which is approaching state-of-the-art for HEMT grown on SiC. Sheet resistance as low as 274 Ω/□ has also been achieved.     

Determination of the ~(12)C(p, γ)~(13)N reaction rates fromthe ~(12)C(~7Li,~6He)~(13)N reaction

The angular distribution of the 12C(7Li,6He)13N reaction at E(7Li) = 44.0 MeV was measured at the HI-13 tandem accelerator of Beijing, China. The asymptotic normalization coefficient (ANC) of 13N → 12C + p was derived to be (1.64 ± 0.11) fm-1/2 through the distorted wave Born approximation (DWBA) analysis. The ANC was then used to deduce the astrophysical S (E) factors and reaction rates for the 12C(p,γ)13N direct capture reaction at energies of astrophysical relevance.     

Radiative leptonic decay Bc^-→τ^vτ^-γ in the standard model and the two-Higgs-doublet model

We analyze the radiative leptonic Bc decay Bc^-→τ^vτ^-γ in the Standard Model and the two- Higgs-doublet model using the non-relativistic constituent quark model. The results confirm that this channel is experimentally promising in view of the large number of Bc mesons which are expected to be produced at future hadron facilities. We also find that this decay is sensitive to the parameters of the two-Higgs-doublet model, and it can be tested in future experiments.