稀土掺杂纳米晶体荧光发射性质的调控

稀土掺杂纳米体系的荧光发射过程主要取决于稀土离子的性质和基质结构。对于给定体系,可控荧光性能的构筑包括改变纳米颗粒自身性质和外部条件两个方面。改变颗粒自身性质的途径主要包括调节纳米晶体的成分、结构、掺杂元素的性质、浓度及颗粒的大小、形貌、表面修饰以及通过纳米金属结构实现的金属增强等。外部环境的改变则主要包括颗粒的环境温度和泵浦方式等。本文阐述了影响荧光发射的主要因素和调控荧光性质的主要途径, 并着重对晶体结构变化和稀土共掺杂所引起的局域对称性和相互作用变化进行讨论。     

改进的自适应衰减卡尔曼滤波算法

SINS/GPS组合导航系统的融合算法主要是卡尔曼滤波,卡尔曼滤波实现最优估计的前提是系统的模型和随机噪声信息必须准确已知。实际情况下,大部分系统的模型和随机噪声信息不完全可知,这可能会导致滤波器估计精度下降。针对这一问题,根据求解遗传因子的方法不同对传统的自适应衰减卡尔曼滤波进行改进,提出一种改进的自适应衰减卡尔曼滤波。改进后的算法分别适用于系统噪声统计模型不准确可知和量测噪声统计模型不准确可知两种情况,分别对应于两种滤波算法,并且二者具有统一的滤波框架。仿真结果表明,改进的自适应衰减卡尔曼滤波比卡尔曼滤波精度较高,有效解决了因为噪声模型不准确导致的精度下降问题。     

Pressure-induced structural evolution of apatite-type La_(9.33)Si_6O_(26)

The pressure-induced structural evolution of apatite-type La_(9.33)Si_6O_(26) was systematically studied using in situ synchrotron x-ray diffraction(XRD). The XRD spectra indicated that a subtly reversible phase transition from P6_3/m to P6_3 symmetry occurred at ～ 13.6 GPa because of the tilting of the SiO_4 tetrahedra under compression. Furthermore, the La_(9.33)Si_6O_(26) exhibited a higher axial compression ratio for the a-axis than the c-axis, owing to the different axial arrangement of the SiO_4 tetrahedra. Interestingly, the high-pressure phase showed compressibility unusually higher than that of the initial phase, suggesting that the low P63 symmetry provided more degrees of freedom. Moreover, the La_(9.33)Si_6O_(26) exhibited a lower phase transition pressure(PT) and a higher lattice compression than La_(10)Si_6O_(27). Comparisons between La_(9.33)Si_6O_(26) and La_(10)Si_6O_(27) provided a deeper understanding of the effect of interstitial oxygen atoms on the structural evolution of apatite-type lanthanum silicates(ATLSs).     

Low-temperature synthesis of apatite-type La_(9.33)Ge_6O_(26) as electrolytes with high conductivity

In the present study,high-quality apatite-type La_(9.33)Ge_6O_(26) powders are successfully synthesized by a facile moltensalt synthesis method(MSSM) at low temperatures,using Li Cl,Li Cl/Na Cl mixture(mass ratio 1:1) as molten salt,respectively.Experimental results indicate that the optimal mass ratio between reactant and molten salt is 1:2,and Li Cl/Na Cl mixed molten-salt is more beneficial for forming high-quality La_(9.33)Ge_6O_(26) powders than Li Cl individual molten-salt.Comparing with the conventional solid-state reaction method(SSRM),the synthesis temperature of apatitetype La_(9.33)Ge_6O_(26) powders using the MSSM decreases more than 350?C,which can effectively avoid Ge loss in the preparation process of precursor powders.Furthermore,the powders obtained by the MSSM are homogeneous,nonagglomerated and well crystallized,which are very favorable for gaining dense pellets in the premise of avoiding Ge loss.On the basis of high-quality precursor powders,the dense and pure ceramic pellets of La_(9.33)Ge_6O_(26) are gained at a low temperature of 1100?C for 2 h,which exhibit higher conductivities(σ850?C(Li Cl)= 2.3 × 10~(-2) S·cm~(-1),σ850 ?C(Li Cl/Na Cl) = 4.9 × 10~(-2) S·cm~(-1)) and lower activation energies(Ea(Li Cl)= 1.02 e V,Ea(Li Cl/Na Cl)= 0.99 e V) than that synthesized by the SSRM.     

YAG对撞增强相位共轭腔的脉宽研究

报道了在YAG激光器上运行新型的对撞型受激布里渊散射相位共轭腔的实验情况,该腔具有较低的启动阈值,并能输出稳定的ns量级自调Q激光脉冲.本文给出了不同参量条件下的输出脉宽情况.     

氨气预混旋流燃烧火焰稳定性及燃烧极限研究

采用叶轮型旋流燃烧器,研究了旋流数、叶片数以及流量等因素对氨气预混旋流燃烧火焰稳定性和燃烧极限的影响.实验结果表明,在一定当量比下,氨气预混旋流燃烧火焰会失稳发生回火或振荡抬举;随着旋流数的增大或叶片数的增加,火焰更易失稳发生回火;石英玻璃高度越高,内部流场结构越完整,火焰高度越高。氨气预混旋流火焰贫燃极限在φ=0.64～0.76之间,富燃极限在φ=1.47～1.74之间。随着总流量的增大,贫燃极限逐渐增大,富燃极限波动较大,总体燃烧极限范围变大;随着旋流数的增大、叶片数的增加或石英玻璃高度的升高,燃烧极限范围变窄。     

A New Doppler Shift Spectroscopy for Measurement of Neutral Beam Profile

A new diagnostic based on Doppler shift is designed to measure the power profile of a hydrogen or deuterium neutral beam on the magnetic confined fusion machines. The interference filters and multi-channel photon detector array （PDA） are the main components of this diagnosis. The multi-channel PDA measures the line integrated Doppler Ha signal emitted by the neutral beam at one section in two directions. The local intensity of neutral beam can be obtained with the tomography technique. Compared to the conventional calorimeter diagnoses, this diagnosis can provide the beam profile without blocking the injection of neutral beam.     

固体火箭发动机虚拟试验技术初探和应用

为改进固体火箭发动机传统试验模式存在的资源瓶颈、试验性能难以预示等问题,在固体火箭发动机试验与测试领域引入虚拟试验技术,设计并开发了固体火箭发动机虚拟试验基础系统;阐述了固体火箭发动机试验模型、试车架模型的建模方法,利用均匀设计方法分析影响内弹道数据的主要因素权重,以修正虚拟试验内弹道数据;针对某型号固体火箭发动机进行虚拟验证,试验结果表明,虚拟试验基础系统在一定程度上具有与真实固体火箭发动机地面试验相似的流程和功能,通过修正虚拟试验内弹道数据,进一步降低了虚拟试验结果与真实试验结果间的误差,为深入开展固体火箭发动机虚拟试验技术研究奠定了基础。     

NH3/H2预混旋流火焰稳定性及燃烧极限实验研究

采用叶轮型旋流燃烧器,选取氢气作为燃料添加剂,研究了掺氢比对氨气旋流火焰稳定性的影响,分析了不同旋流数、叶片数、当量比以及预混气总流量条件下,旋流火焰形态变化.测定并分析了不同参数对旋流火焰燃烧极限范围的影响,结果表明,随掺氢比的增大,火焰逐渐由"V"型转化为稳定的"M"型,燃烧反应愈发充分;高旋流数(1.27)或低叶...