Levels in182W populated in the decay of182Ta

Theγ-rays emitted in theβ-decay of¹⁸²Ta have been reinvestigated with improved statistics in attempting to clarify the reported new levels at 1460.41, 1592.98, 1620.36, 1712.29 and 1762.91 keV in¹⁸²W observed in theβ-decay of¹⁸²Ta. The present study demonstrated that the fifteen newγ-rays, which were used to support the existence of the five new levels, are not relevant to theγ-decay of¹⁸²Ta. Therefore the five new levels are not populated in this decay. Additionally, theγ-ray with an energy of 1035.6 keV (0 ₂ ⁺ →2 ₁ ⁺ ) deexciting theβ-band head in¹⁸²W is observed for the first time in the present decay study and the previous tentative placement of the 351.0 keVγ-ray in the level scheme is confirmed by the present coincidence measurements.     

基于散射模型设计外遮光罩

通过对粗糙表面散射情况的分析发现,普通金属材料的表面散射能量主要集中在10°散射角内。针对这种现象,提出了基于该散射特性的光学系统外遮光罩设计方法,该遮光罩的杂散光抑制角比基于反射理论计算的大5°,具有良好的散射杂散光的抑制作用。最后以Ritchey-Chirtien(R-C)光学系统为例,为其设计了合适的遮光罩,并在TracePro软件中对比性地建模、分析。结果证明了该模型的正确性,且该遮光罩对抑制杂散光起到了很好的效果,点源透射比(PST)相对较低。     

优化两色组合场参数获得单个阿秒脉冲

基于经典方法优化了组合场中基频场和低频场的强度比,利用优化后的组合场驱动一维氦原子,通过求解含时薛定谔方程研究了氦原子产生的高次谐波,其截止位置得到扩展,再考虑基频场初相位对产生高次谐波的影响,能够得到脉宽为37as的单个阿秒脉冲.     

Synthesis and luminescent properties of BaGd2O4:Dy3+, an novel scintillating phosphor

The BaGd_2?x O₄:xDy³⁺ (0 ≤ x ≤ 0.08) phosphors were synthesized at 1,300 °C in air by the solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction, photoluminescence excitation spectra, photoluminescence (PL) spectra, X-ray excited luminescence (XEL) spectra, and thermoluminescence (TL) spectra. It is found that the quenching concentration of Dy³⁺ ions in BaGd₂O₄ host is dependent on the selected excitation wavelength. The optimal PL intensity for the investigated BaGd_2?x O₄:xDy³⁺ phosphors is found to be x = 0.01, 0.02, and 0.04, upon excitation by 234, 277, and 350 nm ultraviolet light, respectively. The energy transfer among Dy³⁺ ions upon excitation by 350 nm is confirmed to be an electric dipole–dipole interaction mechanism based on the fitting of Huang’s rule. In addition, the intensive XEL from BaGd₂O₄:Dy³⁺ phosphor is observed by the naked eyes at room temperature, and TL properties of the investigated phosphors are analyzed and discussed. All the results imply that the investigated phosphors could be a promising scintillating phosphor.     

Propagation of a Hermite–Laguerre–Gaussian beam in a turbulent atmosphere

The propagation and spreading of a Hermite–Laguerre–Gaussian (HLG) beam in a turbulent atmosphere has been investigated. Based on the extended Huygens–Fresnel integral and some mathematical techniques, analytical expressions for the average intensity, the effective beam size, and the kurtosis parameter of an HLG beam in a turbulent atmosphere are derived, respectively. The average intensity distribution and the spreading properties of HLG beams in a turbulent atmosphere are numerically demonstrated. Upon propagation in a turbulent atmosphere, the central lobes in the beam spot of the HLG beam will evolve into the dominant lobes, and the peripheral lobes around the central lobes will evolve into the subdominant lobes. The influences of the additional angle parameter and the transversal mode numbers on the propagation of HLG beams in a turbulent atmosphere are also discussed. As the coherence length of the turbulence is determined by the propagation distance, the effect of the additional angle parameter on the effective beam size is related to the propagation distance. The kurtosis parameter generally increases with increasing the additional angle parameter. The influence of the transversal mode numbers on the kurtosis parameter is related to the additional angle parameter and the propagation distance. According to the practical need of free-space optical communications and remote sensing, the HLG beam in a turbulent atmosphere can be controlled by choice of the additional angle parameter and the transversal mode numbers.     

The ionic conductivity of Li6BaLa2M2O12 with coexisting Nb and Ta on the M sites

In a view to balancing cost and lithium ion conductivity, Li₆BaLa₂Nb _x Ta_2???x O₁₂ (x?=?0–2) was prepared by solid-state reaction, and its corresponding AC impedances were tested at temperatures ranging from 20 to 250 °C in air. Li₆BaLa₂Ta₂O₁₂ exhibits the highest conductivity, 8.77?×?10^?6?S/cm, and the second highest is Li₆BaLa₂Nb₂O₁₂ with 6.69?×?10^?6?S/cm. Partial replacement of Ta with Nb cannot bestow the advantages of cost saving or the enhancement of lithium ion conductivity. X-ray diffraction patterns revealed a gradual change as an increasing amount of Nb replaces Ta in Li₆BaLa₂Nb _x Ta_2???x O₁₂ (x?=?0–2), and it is thought that the trending of Nb and Ta to rest on the crystallographic planes is different.     

密集阵高功率微波空间功率合成

对基于矩形阵列的高功率微波二维密集阵阵列合成进行了研究。仿真分析了均匀矩形栅格阵列的远场方向图,结果表明采用密集阵可以实现高效的、具有确定主波束的空间功率合成。并分析了阵元间距及阵元初相位对阵列空间功率合成的影响,结果表明:阵元间距越小,栅瓣越少,主波束宽度越宽,具有确定主波束的临界距离越小;当目标高度超过阵临界距离时,阵元初相位相差越小合成效率越高,阵列初相位分布范围超过/2时,阵列得不到确定的主波束,进行阵列设计时应充分考虑阵元间距及初相位对阵列合成的影响。     

基于斯托克斯矢量的偏振成像仪器及其进展

偏振成像技术将景物的偏振信息转化为二维图像信息,从而可以和灰度图像一样对目标景物进行场景特征分析。介绍了基于斯托克斯矢量的偏振成像原理。按照获取斯托克斯矢量方法的不同,分别介绍了偏振片起偏、偏振棱镜分光和可变延迟波片调制三类分时偏振成像方式,分振幅、分孔径、分焦平面三种同时偏振成像方式。结合我国的制造水平,设计了双CCD渥拉斯顿棱镜同时偏振成像实验系统,并采集了实验图像。分析了各种偏振成像方式的优缺点。指出了偏振激光照明主动偏振成像、光谱偏振成像是偏振成像仪器进一步的发展方向。     

改进的三维电磁PIC系统模拟并行算法

为了更好地实现对大尺度器件的模拟,以及更系统地验证和解决高功率微波系统在设计和实验中负载变化等影响,在进一步深入研究电磁PIC并行算法的基础上,运用MPI消息传递函数做出了改进。提出了一种整体建模、分段解析的并行算法,并从并行时序算法入手,通过减少一次同步提高了计算的效率。最后经过一个磁绝缘线振荡器进行验证,改进的算法正确,并且当计算进程数4个增加到16个时,计算速度能提高2.5倍左右。