POM晶体倍频相位匹配角的设计及应用

计算了新型有机晶体ＰＯＭ的倍频匹配角，并将ＰＯＭ作为倍频器件用于超短光脉冲的测量中。     

Relaxation-Induced Significant Room-Temperature Dielectric Pulsing Effects

Thermo-responsive dielectric materials are in urgent demand owing to the rapid development of smart electronic/electrical systems. Although different types and structures of thermally responsive dielectric materials have been continuously reported, their dielectric response behaviors all originate from thermodynamic phase transitions. Herein, it is demonstrated that structural relaxation in poly(vinylidene fluoride) (PVDF), a non-thermodynamic phase transition, can induce a significant thermal dielectric pulse at room temperature. The dielectric pulse strength of up to 6.3 × 10⁵ at 20 Hz, with a dielectric pulsing temperature of 24 °C, is achieved from polyethylene glycol (PEG)-PVDF coaxial nanofibrous films (PVDF@PEG), fabricated via a continuous blow spinning method. Moreover, the films exhibit excellent flexibility, adjustable strength and toughness, switchable hydrophilicity/hydrophobicity, and effective thermal management capability. The relaxation-induced dielectric pulsing effect, outstanding multifunctionality, and simple preparation combine to promote further scalability and prospects of PVDF@PEG. In particular, the work contributes to the discovery of the relaxation-induced dielectric response mechanism, which provides a new strategy for the generation of thermo-responsive dielectric materials.     

Stochastic simulation of velocity pulses of near-fault ground motions based on multivariate copula modeling

Due to the featured high-amplitude, long-period pulses in velocity or displacement time–history, the near-fault ground motion may have a stronger destructive effect on engineering structures. Therefore, studying velocity pulses modeling of near-fault ground motions has been an important topic in the earthquake engineering community. However, the variability and probabilistic correlation of pulse model parameters have not received enough attention. To this end, an elegant method for stochastic simulation of velocity pulses of near-fault ground motions is proposed based on the classical Gabor wavelet modeling and probabilistic correlation analysis of associated model parameters by multivariate copula modeling. Especially, an efficient scheme of iteratively determining the optimal copulas pertinent to edges of a complex vine structure is developed, and two parameters relevant to the near-fault ground motion records, i.e., the rupture distance and the strongest pulse orientation, are introduced which provides a physical basis for addressing the dependence structure among variables. For illustrative purposes, the ground accelerograms recorded by near-fault instruments in the 1999 Chi-Chi earthquake are used. It is shown that the multivariate copula modeling enables the efficient representation of probabilistic correlation between model parameters which is consistent with their physical mechanism. The time histories and spectral characteristics of velocity pulses of near-fault ground motions and their stochastic fluctuations with respect to the rupture distance are well simulated. While the empirical linear regression model does not meet the requirements of random vibration analysis and thus cannot guide the safety design of seismic structures.     

高阶非线性效应对啁啾高斯光脉冲传输的影响

利用对称分步傅立叶方法（SSFM）求解非线性薛定谔方程（NLS）,探讨了光纤损耗、三阶色散和五阶非线性极化效应对啁啾高斯光脉冲传输的影响.数值研究结果指出：在一定条件下,初始啁啾、三阶色散和五阶非线性效应都会对脉冲的波形、宽度和峰值功率产生影响,脉冲的振荡波形主要由三阶色散决定,五阶非线性和啁啾会对它起到调制作用,存在一定的三阶色散和五阶非线性能减弱初始啁啾对脉冲的影响.     

Percussion Laser-Drilled Holes: Characteristics and Characterization Procedure

Percussion laser drilling, being a thermal process, produces holes having widely differing characteristics than that of the mechanically drilled holes. In the present study, on the percussion laser drilling of through holes in a nickel-based superalloy (SUPERNI 263A), 21 characteristics were identified, and the methods of their determination were proposed. The effect of peak power of laser pulses on the identified hole characteristics were studied.     

一种新型的大功率电镀电源

国内生产的１０００Ａ以上的晶闸管与同容量二极管的价格相近，采用晶闸管研制出一种整流和控制结合为一体的大功率电镀电源，打破了传统的整流和控制分离而使用两种半导体器件及两种电磁部件的方法．这种新型的大功率电镀电源的特点是造价低，输出电流能力强，可靠性高，控制特性好且能量损失小．     

纳焦飞秒激光在有机材料表面刻划微结构光栅的研究

使用振荡器产生的飞秒激光在透明有机材料PMMA表面进行了刻划微结构光栅的研究．通过理论分析得到了飞秒激光参数和平台移动速度对线宽的影响，进行了系统的加工实验，加工结果与理论分析基本吻合．在透明有机材料PMMA表面进行了多种光栅的刻划，并对刻划的光栅进行了衍射和色散测试，调整光栅的尺寸和排列方式，得到了形状各异的衍射图案。     

Burst pulses for positive corona discharges in atmospheric air: the collective movement of charged species

Positive corona burst pulses are an unstable pulse mode. They appear in a small range of the onset stage, and their current pulses result from the collective movement of charged species. This paper focused on the connections between these pulses and the collective movement of charged species. The movement of species is divided into four parts with respect to time: the(1) initial growth of species,(2) formation and development of the streamer region and negative ion sheath,(3) dead time(the time interval between the pulses), and(4) rapid re-growth of species.The movement of the species in the four parts and the correspondence with the current pulse were analyzed. The numerical results indicated the following: the rapid rising of the species matched the rising edge of the pulses, the streamer region, and negative ion sheath appeared in the falling edge of the primary pulse, and the rapid re-growth of species matched the re-ignition of the pulses. The results were in qualitative agreement with deductions and experimental observations in the literature.     

基于半正定规划的超宽带正交脉冲波形设计

为了通过超宽带脉冲波形设计来降低系统多用户干扰及提高功率利用率,通过在半正定规划(SDP)算法的求解过程中引入Yalmip工具箱来实现对于FCC功率谱密度规范的更好逼近,得到了具有比较高功率利用率的正交波形.同时还分析了不同的高斯单脉冲中心频率对于最终所得功率利用率的影响,结果表明通过合理地选择参数可以进一步提高所得脉冲的功率利用率.     

飞秒激光加工参数对RB-SiC表面形貌的影响

目的 揭示飞秒激光加工参数对反应烧结碳化硅(Reaction-Bounded Silicon Carbide,RB-SiC)表面形貌的影响规律。方法 通过改变激光能量密度和有效脉冲数,研究RB-SiC表面烧蚀槽的形貌变化规律,确定飞秒激光加工RB-SiC的去除机理。采用扫描电镜、共聚焦显微镜、X射线能谱仪和拉曼光谱仪分析RB-SiC烧蚀前后的表面形貌演变行为。结果 激光能量密度在0.62~10.48 J/cm²时,Si富集区域形成凹陷结构,SiC颗粒区域形成周期性结构(Laser-Induced Periodic Surface Structures,LIPSS),周期约为970 nm。随着激光能量密度的增加,凹陷结构扩大加深,表面球形纳米颗粒增多,烧蚀槽宽度呈对数增长。有效脉冲数在69~ 1 379,Si富集区域的去除量高于SiC颗粒区域的去除量。随着有效脉冲数增加,烧蚀槽深度显著加深,凹陷结构扩展成深坑结构,飞溅至烧蚀槽外侧的纳米颗粒聚集成团簇物,由Si、SiC和非晶态SiO2构成的沉积物在烧蚀槽边缘形成堆积层。结论 降低激光能量密度能够减少RB-SiC表面凹陷和纳米颗粒,有助于提升烧蚀形貌的一致性。增加有效脉冲数会促进烧蚀槽底部深坑结构的产生,进而扩大Si与SiC去除量之间的差异。