掺Y对PbWO4闪烁体的热释光影响

研究了纯PbWO₄和PbWO₄:Y晶体经γ射线辐照和可见光光照前后室温 以上的热释光.发现大剂量辐照后掺Y可以有效地抑制热释光的强度并使热释光峰移向高温, 说明掺Y有利于提高光输出的稳定性.可见光光照也会影响热释光并可以产生新的热释光峰, 这可能是由于光释电子(或空穴)被浅陷阱重新俘获或是光照后产生了新型色心的结果. 关键词： 4')" href="#">PbWO₄ 掺Y 热释光     

关于正拼挤流形的P调和映射的不稳定性

本文研究了出发流形为δ-Pinched流形的P调和映射的不稳定性,推广了文献[3]的相应结果。     

SPECT均匀衰减投影数据的反演公式

依据近年来公开发表的有关单光子发射断层成像(SPECT)成像技术的文献,探索SPECT均匀衰减投影数据的反投影问题.主要采用指数型拉动变换的性质和构造特殊函数—–δ函数的方法,进而应用δ函数的特殊性得到了一个精确的反演公式.结果表明,由这种方法得到的反演公式能够更加有效和精确地实现图像的重建.     

Influence of the substrate material on the properties of pulsed laser deposited thin Li1+xMn2O4−δ films

Thin Li_1+xMn₂O_4−δ films were deposited on several substrate materials (stainless steel, p-doped silicon and glassy carbon) by pulsed laser deposition. To obtain the correct thin film stoichiometries, targets with a different amount of excess lithium were required (Li_1.03Mn₂O₄ + xLi₂O; x = 2.5 and 7.5 mol%). The resulting polycrystalline thin films were characterized with respect to their morphology and electrochemical activity. It was found that only thin Li_1+xMn₂O_4−δ films deposited on stainless steel and glassy carbon showed the typical insertion and deinsertion peaks of Li⁺ during cycling.     

Ga掺杂δ-Pu的密度泛函理论计算

δ-Pu为Pu的高温相,掺杂少量的Ga即可使其在室温下稳定存在.本文采用密度泛函理论方法,对不同掺杂量体系进行晶体结构和电子结构计算,主要包括体系的晶格常数、密度、形成能、态密度、电荷密度和Mulliken布居分析.结果表明：在研究范围内,Ga掺杂后,体系晶格常数降低,密度增大,6.25%（原子百分比,下同）掺杂量体系的稳定性高于3.125%和12.5%掺杂量的体系;Ga掺杂使得Pu周围体系电子的局域性增强,成键能力增强,揭示了Ga稳定δ-Pu的电子机制.Ga和Pu之间为金属键,发生的作用主要由Pu的7s、6p、6d和Ga的4s、4p轨道电子贡献,但这种成键作用相对较弱,使得掺杂体系可以保持原有的力学性能和机械加工性能.Ga对δ-Pu的稳定作用主要在于改善Pu原子的成键性能,而不是与Pu原子直接成键.     

Sr3YCo4-xMgxO10.5+δ(0≤x≤0.04)多晶的制备和热电输运性质研究

采用固相反应法制备Sr3YCo4-xMgxO10.5+δ(0≤x≤0.04)系列多晶,研究了Mg掺杂对体系结构、电输运和热电性质的影响.结果表明系列多晶为四方晶系,由于掺入的Mg2+(0.066 nm)部分替代了Co3+/4+(0.053 nm/0.061 nm),使晶格膨胀;多晶热电势在340~830 K随温度升高而下降,且Mg掺杂对热电势影响不大,表明Mg掺杂对体系载流子浓度影响不大;多晶电阻率在100~300 K随温度升高而降低,且随着掺杂量增加电阻率降低,结合扫描电镜观察到多晶的气孔数目减少、晶粒连接紧密和热电势的结果认为Mg掺杂对体系电输运性质的影响机制主要是使气孔、晶界散射作用减弱、载流子迁移率变大,而Mg掺杂对载流子浓度的影响是次要的.     

Microwave absorption properties regulation and bandwidth formula of oriented Y2Fe17N3-δ@SiO2/PU composite synthesized by reduction-diffusion method

As concepts closely related to microwave absorption properties, impedance matching and phase matching were rarely combined with material parameters to regulate properties and explore related mechanisms. In this work, reduction-diffusion method was innovatively applied to synthesize rare earth alloy Y$_{2}$Fe$_{17}$. In order to regulate the electromagnetic parameters of absorbers, the Y$_{2}$Fe$_{17}$N$_{3-\delta }$ particles were coated with silica (Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$) and absorbers with different volume fractions were prepared. The relationship between impedance matching, matching thickness, and the strongest reflection loss peak (${\rm RL}_{\rm min}$) was presented obviously. Compared to the microwave absorption properties of Y$_{2}$Fe$_{17}$N$_{3-\delta }$/PU absorber, Y$_{2}$Fe$_{17}$N$_{3-\delta }$@SiO$_{2}$/PU absorbers are more conducive to the realization of microwave absorption material standards which are thin thickness, light weight, strong absorbing intensity, and broad bandwidth. Based on microwave frequency bands, the microwave absorption properties of the absorbers were analyzed and the related parameters were listed. As an important parameter related to perfect matching, reflection factor ($\sqrt {ărepsilon_{\rm r}/\mu_{\rm r}}$) was discussed combined with microwave amplitude attenuation. According to the origin and mathematical model of bandwidth, the formula of EAB (${\rm RL}<-10$ dB) was derived and simplified. The calculated bandwidths agreed well with experimental results.     

稳定同位素比质谱法测定苹果和浓缩苹果汁的δ13C值

用从国际原子能机构溯源得到的橄榄油标准物质[Cat No.B 2172-Batch 3130,其δ13CPDB为(-28.51±0.16)‰]作标准,应用稳定同位素比质谱法测定了苹果和苹果汁的δ13 C值,并以此确定国产苹果的δ13 C值的范围和鉴定制成的果汁的质量。苹果样品去皮后切碎,打成糊状,离心后取其上清液,在75℃加热2～3h至呈黏稠状液体,冷却至室温。此时其糖度约为70Brix。浓缩苹果汁样品是黏稠液体,其糖度一般也在70Brix左右。取2μL上述样品置于锡杯中,按方法处理后供质谱分析。标准物质的进样量为2μL。按所测得碳的稳定同位素13C与12C的比值代入所给公式计算δ13 C值。结果表明:方法的精密度较好,其相对标准偏差(n=11)均小于0.021%。根据测定结果发现,我国苹果的δ13C值在-29.1‰～-23.33‰之间。     

On the ground state of quantum graphs with attractive δ-coupling

We study relations between the ground-state energy of a quantum graph Hamiltonian with attractive δ coupling at the vertices and the graph geometry. We derive a necessary and sufficient condition under which the energy increases with the increase of graph edge lengths. We show that this is always the case if the graph has no branchings while both energy increase and decrease are possible for graphs with a more complicated topology.     

利用H3PO4液层侧面红外热像研究YBCO高温超导薄膜的激光辅助刻蚀特性

利用红外热像实时监测系统,获取钇钡铜氧激光辅助化学刻蚀中H₃PO₄液层的侧面红外热像,研究了其溶液温度分布与热对流特性,并对红外监测数据与钇钡铜氧薄膜激光化学刻蚀特性的关系进行了分析.主要实验结论包括:红外灰度图可真实反映溶液的温度分布和热对流情况,为激光化学刻蚀的热环境分析提供有价值的红外监测数据;通过任意时刻钇钡铜氧表面生成热流所到达高度的分布情况和该时刻的红外灰度图,分析出钇钡铜氧薄膜表面各区域的腐蚀启动先后和刻蚀程度差异等重要信息,为钇钡铜氧及其它材料的激光化学刻蚀特性的实时监测提供了一种新的技术手段.