波长间隔可调的可开关双波长掺铒光纤激光器

对两种波长间隔可调的可开关双波长掺铒光纤激光器结构进行了实验研究。一种结构应用保偏光纤中布拉格光栅作为波长选择器件，另一种结构则利用侧向压力下的常规单模光纤光栅作为波长选择器件。两种结构均利用了光纤光栅的双折射特性。在室温下，通过调整偏振控制器的状态可使两激光器工作在稳定的双波长状态或在两单波长之间转换。通过改变加在光纤光栅上侧向应力的大小和方向，可有效控制双波长激射的波长间隔。     

An upper gradient approach to weakly differentiable cochains

The aim of the present paper is to define a notion of weakly differentiable cochain in the generality of metric measure spaces and to study basic properties of such cochains. Our cochains are (sub)additive functionals on a subspace of chains, and a suitable notion of chains in metric spaces is given by Ambrosio–Kirchheim?s theory of metric currents. The notion of weak differentiability we introduce is in analogy with Heinonen–Koskela?s concept of upper gradients of functions. In one of the main results of our paper, we prove continuity estimates for cochains with p-integrable upper gradient in n-dimensional Lie groups endowed with a left-invariant Finsler metric. Our result generalizes the well-known Morrey–Sobolev inequality for Sobolev functions. Finally, we prove several results relating capacity and modulus to Hausdorff dimension.     

A novel approach for preparing silver nanoparticles under electron beam irradiation

Silver (Ag) nanoparticles were obtained when Ag microparticles were exposed to an electron beam in a transmission electron microscope (TEM). Results from TEM characterization indicated that the morphologies of the prepared Ag nanoparticles were quasi-circular, and the sizes were mainly in the range of 5–60 nm. The effect of irradiation time (t) on size and distribution of Ag nanoparticles was investigated. It was found that the sizes of Ag nanoparticles increased with the increase of t. The bigger Ag nanoparticles were near the Ag microparticle and the smaller ones were far from it. In addition, these Ag nanoparticles were monodisperse. This approach offered a new route for preparing Ag nanoparticles under electron beam irradiation, and the forming process of Ag nanoparticles was explained by the nucleation-growth mechanism.     

斜入射脉冲X射线产生电流实验

针对斜入射脉冲X射线与金属的几种可能相互作用机制,设计了实验布局,测量了斜入射X射线在金属靶上产生的脉冲电流,建立了相应的理论模型。结果显示,当X射线入射强度低于105 W/cm2时,以光电效应为主,高于此值时,以热电效应为主导。这表明,X射线加载强度较弱时,电子表现出个体行为,而增大X射线入射强度,电子表现出弱关联集体行为。由此可以预测,超强X射线辐照下,金属表面将出现宏观尺度的电荷密度调制,在退激发过程中,这种调制状态可能以较高的效率辐射定向的微波电磁脉冲。     

基于GaSe差频产生8～19μm可调中红外辐射

利用Nd:YAG激光器抽运内腔KTP光学参量振荡器,得到了输出为2μm附近的双波长,并在满足Ι类相位匹配条件下,在GaSe中共线差频产生8～19μm连续宽调谐调的中红外辐射.在8.76μm处脉冲最大能量达33.66μJ,峰值功率7.4kW,光子转换效率达4.43%左右.分析了影响能量转化效率的原因,提出了补偿走离的措施.     

在模情况时二面体群$D_{2p}$作用下的transfer理想

In this paper, we determine the structures of the transfer ideal and its radical ideal for the ring of polynomials F p[x, y] under the action of dihedral group D2 p in the modular case. We mainly use Transfer variety, p order elements, and Hilbert’s Nullstellensatz Theorem.     

高精度组合脉冲激光时序控制系统设计

在激光等离子体机理的研究中,为实现灵活的界面配置和多路脉冲激光器高精度的时序延时,设计了一种基于微控制器STM32和FPGA的多路时序延时控制系统。重点介绍了基于FPGA的多路ns级时序信号和基于ucGUI的触摸屏界面的设计。另外,采用高速光电隔离技术和高速FET开关电路技术,对驱动电路进行了设计,缩短了输出脉冲上升沿的时间,提高了系统延时精度、驱动能力和抗干扰性能。测试结果表明,该设计每路延时可调,调节范围为5 ns~10 ms,最小可调步进为5 ns,延时误差小于1 ns。     

指数修正高斯拟合寻峰算法处理FBG传感信号

光纤布拉格光栅(FBG)传感系统因其检测精度高、重复性好和适应性强等优点而被广泛应用于不同领域。由于FBG传感器为波长调制型传感器,因此对于外界参量的检测即为FBG中心波长的检测,而FBG中心波长值对应于FBG反射光谱的峰值。因此,系统解调的核心即为FBG反射光谱的峰值检测,而高精度的寻峰算法是系统解调的关键技术。现有的寻峰算法对FBG反射谱进行峰值检测时,都是以FBG反射谱为标准高斯型为前提的。但由于实际制作工艺及环境的影响,FBG反射光谱并不是标准高斯型光谱,而是非对称的高斯型光谱,其非对称特性往往会对寻峰精度有一定的影响。针对现有算法这一缺陷,提出了一种指数修正高斯(EMG)拟合寻峰算法。利用三次判定定位实现粗定位,同时剔除假峰和无效峰值;在此基础上以粗定位点为中心进行光谱重构,再利用积分判定峰值偏向;然后根据不同的峰值偏向以给定的指数修正函数进行相应的峰值修正。实验仿真结果表明：定温条件下或变温条件下,与直接寻峰算法、高斯拟合算法和文献中的算法相比,EMG算法的峰值检测误差最小,寻峰精度提高。考虑了FBG反射光谱非对称特性对寻峰的影响,从光谱自身特性的角度,既克服了传统寻峰算法的局限性,又保证了高精度的寻峰效果。     

Quasiregular mappings to generalized manifolds

We establish the basic analytic and geometric properties of quasiregular maps f: ω → X, where ω ? ? ⁿ is a domain and X is a generalized n-manifold with a suitably controlled geometry. Generalizing the classical Väisälä and Poletsky inequalities, our main theorem shows that the path family method applies to these maps.     

Synthesis of novel 4H-pyrimido[1,6-a]pyrimidines via a one-pot three-component condensation

Abstract  

Highly substituted novel 4H-pyrimido[1,6-a] pyrimidines were prepared by a trifluoromethanesulfonic acid catalyzed one-pot three-component condensation of 4-aminopyrimidines, aldehydes, and β-ketoesters. A preliminary feasibility study was undertaken on these compounds, to assess the potential production of a library of further diversified compounds by nucleophilic replacement of Cl (R¹) or by reaction of electrophiles with the NH₂ (R²) group.