Robustness of SDOF elastoplastic structure subjected to double-impulse input under simultaneous uncertainties of yield deformation and stiffness

A series of impulse-type inputs has been extensively used to evaluate the critical response of an elastoplastic structure subjected to diverse types of pulse-type inputs, including a near-fault ground motion. In this paper, we consider the critical double-impulse input for a single-degree-of-freedom elastic–perfectly plastic structure, and study effects of structural uncertainties. When the natural frequency (or, equivalently, the stiffness) is fixed, the critical response of the structure does not necessarily decrease as the yield deformation (or, equivalently, the yield force) increases. As the first contribution, we give through investigation of this non-monotonicity property. Moreover, we present a systematic method for finding the worst-case scenario when the yield deformation and the stiffness of a structure assumed to be uncertain simultaneously. Numerical examples are presented to illustrate that the robustness of a structure does not necessarily improve when the yield deformation and/or the yield force is increased.     

Beam emittance investigation in high brightness injector using different driver laser profiles

Beam emittance plays an important role in any accelerator, and it is a main parameter to judge the performance of an accelerator. Emittance optimization is an indispensable part in conditioning and operation of the facility. For a laser-driven high brightness injector, different time structure of the laser pulse has different effects on transverse emittance. In order to compare Gaussian and flat-top laser pulse, systematic simulations of 500 pC have been done. From the simulation results, one can see that flat-top pulse laser will yield smaller minimal transverse beam size and transverse beam emittance than Gaussian pulse laser.     

高斯初始能量分布下自由电子激光饱和状态的统计理论求解

基于高增益自由电子激光饱和状态的统计物理方法,在不同的电子束相空间初始分布下对原有理论进行了发展和推广,借助于多重数值积分技术解决了粒子束一般动量初始分布带来的计算困难,并以更接近实际的高斯动量分布为例进行计算。作为对比验证编写高斯初始动量分布下的直接数值模拟程序,将高斯初始分布同"水袋"两种初始分布的"暖电子束"入射情形下自由电子激光达到饱和时系统的光强、聚束因子和粒子相空间分布均进行相应计算和比较。结果表明:数值模拟和统计计算结果相一致;在目前选取的参数范围内,两种初始分布的相应结果差异并不显著。     

紧凑型自由电子激光THz源上四极磁铁的设计及测量

基于自由电子激光（FEL）的太赫兹源具有高功率、高效率、波谱范围宽且连续可调、波束质量好等显著优点,目前是获得最高输出功率的方法。紧凑型太赫兹源使整体装置小型化,减少了装置成本和占用空间,但依然可以提供高功率、高品质的太赫兹波束,是一种便利可靠的用户装置。由于空间限制,FEL上的磁铁要尽可能地减小其尺寸,并仍能满足束流参数设计要求。本文设计的四极磁铁磁轭孔径与有效长度,其中2块是64 mm100 mm,另外3块是45 mm100 mm。这些四极磁铁的磁场梯度可以达到0.6~1.9 Tm-1。采用Poisson和Oprra-3D软件进行四极磁铁的二维和三维仿真计算,设计优化四极磁铁的结构,并测量了加工完成后的四极磁铁的磁场。     

Application of parallel synthesis and high-throughput characterization in photocatalyst discovery

The last decade has seen significant progresses in the application of combinatorial approaches and high-throughput screening in photocatalyst discovery. This paper aims at providing a comprehensive review on the parallel synthesis and high-throughput characterization of photocatalysts, including the development of instrumentation, strategy of experiment, preparation of libraries, high-throughput screening technique and data analysis. The review ends with a summary of the remaining challenges and prospects on combinatorial photocatalyst discovery.     

Anion Mass Spectrometry Study of Ion-Pair Photodissociation of CO2 in the XUV Energy 19.70-22.24eV

We demonstrate anion mass spectrometry using the Hefei synchrotron radiation source to investigate the ion-pair dissociation processes of molecules. The efficiency curve of the O^- anionic product via ion-pair dissociations of CO2 is recorded with tunable extreme vacuum ultraviolet photons （energy： 19.70-22.24 eV） and compared with the spectrum available in the literature. The possible dynamics of CO2 ＋ hv → CO^＋＋ O^- in this energy range is discussed.     

Photodissociation Efficiency Spectroscopy Study of the Rydberg Excited Ion-Pair States of Carbon Dioxide

Photodissociation efficiency spectrum of anionic oxygen atom produced via ion-pair dissociations of carbon dioxide is recorded by means of the synchrotron radiation excitation （XUV photon energy 17.40-20.00eV）. The present spectrum is assigned as the Rydberg-like excited ion-pair states, i.e., Tanaka-Ogawa and Henning series, -↑C^2∑g^＋ （CO2^＋） vibrational ground-state and excitation series. Three Rydberg series, npσu, npπu, and nfu, converging to -↑C^2∑g^＋ （0, 0, 0）, show the higher cross sections.     

Charge transfer dynamics of 3,4,9,10-perylene-tetracarboxylic-dianhydride molecules on Au(111) probed by resonant photoemission spectroscopy

Charge transfer dynamics across the lying-down 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) organic semiconductor molecules on Au(111) interface has been investigated using the core-hole clock implementation of resonant photoemission spectroscopy. It is found that the charge transfer time scale at the PTCDA∕Au(111) interface is much larger than the C 1s core-hole lifetime of 6 fs, indicating weak electronic coupling between PTCDA and the gold substrate due to the absence of chemical reaction and∕or bonding.