The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/α-（Fe,Co） nanocrystalline magnets at low temperature

This paper reports that the SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700 C for 10 minutes.The x-ray diffraction results show that the phase structure of SmCo 6.8 Zr 0.2 nanocrystalline permanent magnets is composed of SmCo 7 phase and SmCo 6.8 Zr 0.2 /α-(Fe,Co) nanocomposite permanent magnets is composed of SmCo 7 and α-(Fe,Co) phases.The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets.The inter-grain exchange interaction at low temperature is investigated,which shows that the inter-grain exchange interaction of SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets increases greatly by the decrease of the measured temperature.According to Δm irr-H/H cj,Δm rev-H/H cj and χ irr-H/H cj curves at room temperature and 100 K,the changes of irreversible and reversible magnetization behaviours of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets with the decreasing temperature are analysed in detail.The magnetic viscosity and the activation volume of SmCo 6.8 Zr 0.2 and SmCo 6.8 Zr 0.2 /α-(Fe,Co) magnets at different temperatures are also studied.     

一种制备单原子碳链的方案

考虑到迄今为止实验上尚不能制备含有上百个原子的自由单原子链,本文提出利用探针从graphene中拉伸较长单原子碳链的设想,并通过分子动力学计算发现,室温下可以利用C60探针以1 m/s的速度从graphene的zigzag边缘拉出较长的一维单原子碳链,为实验提供了一种制备单原子碳链的可能方案. 关键词： 碳链 一维 分子动力学 探针     

LD泵浦Nd:YVO_4双波长运转腔内和频491nm激光器

分析了Nd:YVO4激光器实现双波长运转及腔内和频的条件,利用一种LD泵浦Nd:YVO4晶体产生1 064 nm和914 nm双波长激光束,采用一个线性平凹腔结构,利用腔内Ⅰ类临界相位匹配LBO和频,获得了连续波输出的全固态激光器。实验采用端面结构,在5.0 W的808 nm泵浦功率下,获得了最高功率为2.5 mW连续波TEM00的激光输出,光-光转换效率为0.05%。     

硼酸对亚微米级Ca3Sc2Si3O12:Ce绿色荧光粉的制备及发光性能的影响

采用凝胶-燃烧法合成了Ca₃Sc₂Si₃O₁₂ ∶Ce绿色LED用荧光粉,用X射线粉末衍射(XRD)、扫描电镜(SEM)、荧光光谱仪等对合成产物进行了分析和表征.结果表明:通过添加H₃BO₃做助熔剂,制得的荧光粉晶相纯正,颗粒形貌均呈现为较规则的类球形,而且所得荧光粉的粒径均小于1 μm.发射光谱呈现为一宽带,发射主峰位于505 nm,该宽峰对应于Ce³⁺关键词： 白光LED 荧光粉 3Sc₂Si₃O₁₂ ∶Ce')" href="#">Ca₃Sc₂Si₃O₁₂ ∶Ce 发光     

A new model for electromigration grain boundary noise based on free volume

Grain boundary plays a key role in electromigration process of polycrystal interconnection. We take a free volume to represent a 'vacancy--ion complex' as a function of grain boundary specific resistivity, and develop a new characterisation model for grain boundary noise. This model reveals the internal relation between the boundary scattering section and electromigration noise. Comparing the simulation result with our experimental result, we find the source as well as the form of noise change in the electromigration process. In order to describe the noise enhancement at grain boundary quantitatively, we propose a new parameter-grain boundary noise enhancement factor, which reflects that the grain boundary noise can characterise the electromigration damage sensitively.     

沉积参数对SiNx薄膜结构及阻透性能的影响

利用直流脉冲磁控溅射法在室温下制备无氢SiNx,薄膜.通过傅里叶变换红外光谱、台阶仪、紫外一可见分光光度计、接触角测量仪、透湿测试仪等表征技术,分析了N2流量、Si靶溅射功率等实验参数对SiNx薄膜成分、结构、及阻透性能、透光性能、接触角等性能的影响.研究结果表明,Si靶溅射功率固定时,在低N2流量条件下,或N2流量固定时,在高Si靶溅射功率条件下,制备的SiN,薄膜中Si-N键含量高,结构致密,薄膜对H2O的阻透性能优良,随着N2流量的增加或者Si靶溅射功率的降低,SiNx,薄膜成分、结构发生变化,红外光谱发生偏移,其对H2O的阻透性能下降.在N2流量为6 sccm,Si靶溅射功率为300 W时制备的SiN,薄膜在可见光波段透过率超过97.5%,对H2O的接触角为30,同时其对H2O的渗透系数最低,为0.764,综合性能满足柔性有机电致发光器件封装用阻透膜的要求,因此SiNx薄膜有望成为新一代柔性有机电致发光器件封装用阻透材料.     

Risk-sensitive dynamic pricing for a single perishable product

We show that the monotone structures of dynamic pricing for a single perishable product under risk-neutrality are preserved under risk-sensitivity with the additive general utility and atemporal exponential utility functions. We also show that the optimal price is decreasing over the degree of risk-sensitivity under the exponential class of both additive and atemporal utility functions.     

Crystal growth,spectroscopic characterization and laser performance of Nd:Lu<Subscript>0.33</Subscript>Y<Subscript>0.36</Subscript>Gd<Subscript>0.3</Subscript>VO<Subscript>4</Subscript> crystal

A new three-matrix mixed vanadate crystal Nd:Lu_0.33Y_0.36Gd_0.3VO₄ (Nd:LuYGdVO₄) crystal was grown by the Czochralski method. Room temperature absorption and fluorescence spectra of the Nd:LuYGdVO₄ crystals were measured and the spectroscopic parameters were calculated by the Judd-Ofelt theory. The intensity parameters of the Nd:LuYGdVO₄ crystal were Ω₂ = 9.736 × 10⁻²⁰ cm², Ω₄ = 4.179 × 10⁻²⁰ cm², Ω₆ = 8.020 × 10⁻²⁰ cm² and the stimulate emission cross section was 5.3 × 10⁻¹⁹ cm². Diodepumped actively Q-switched and passively Q-switched Nd:LuYGdVO₄ and Nd:Lu_0.14Y_0.86VO₄ lasers at 1.06 μm were demonstrated. The results indicate that, for both actively and passively Q-switched lasers, the Nd:LuYGdVO₄ lasers can generate shorter pulse width with higher peak power than the Nd:Lu_0.14Y_0.86VO₄ lasers at the same cavity conditions.     

基于Poincaré差值散点图的心率变异性分析方法研究

在心率变异性的非线性分析中, Poincaré散点图分析是一种重要手段.本文基于Poincaré差值散点图(modified Poincaré plot)提出了两个参数——区域分布熵和区域分布系数, 用于定量描述所考察区域内散点的分布趋势, 并提出对散点在4个象限中的分布进行分别计算.通过对MIT-BIH数据库中健康年轻人、健康老年人和充血性心力衰竭患者样本数据的分析, 发现两参数值均呈现显著的组间差异;同时, 不同象限的分析结果显示了四个象限具有不同的区分敏感性, 而其中尤以第一象限的区分度为最高, 反映出充血性心力衰竭患者相对健康人迷走神经调控功能的改变最为显著, 与以往的生理学研究结论相符.经验证, 该方法可用于短时数据, 更易于扩展至临床应用.     

Analysis of the breakdown mechanism for an ultra high voltage high-side thin layer silicon-on-insulator p-channel low-density metal-oxide semiconductor

This paper discusses the breakdown mechanism and proposes a new simulation and test method of breakdown voltage(BV) for an ultra-high-voltage(UHV) high-side thin layer silicon-on-insulator(SOI) p-channel lateral double-diffused metal-oxide semiconductor(LDMOS).Compared with the conventional simulation method,the new one is more accordant with the actual conditions of a device that can be used in the high voltage circuit.The BV of the SOI p-channel LDMOS can be properly represented and the effect of reduced bulk field can be revealed by employing the new simulation method.Simulation results show that the off-state(on-state) BV of the SOI p-channel LDMOS can reach 741(620) V in the 3-μm-thick buried oxide layer,50-μm-length drift region,and at 400 V back-gate voltage,enabling the device to be used in a 400 V UHV integrated circuit.