NⅡ离子2p4f—2p3d辐射跃迁概率的理论研究

在全相对论理论框架下，利用多组态Dirac-Fock(MCDF)方法，系统计算了NⅡ离子2p4f—2p3d的辐射跃迁概率，得到的结果与已有实验值符合很好.具体计算中，详细分析了相对论效应、电子关联、弛豫效应、Breit相互作用和量子电动力学(QED)效应对能级精细结构及辐射跃迁概率的影响.结果表明：相对论效应、电子关联和弛豫效应对NⅡ 2p4f-2p3d辐射跃迁概率有很重要的影响,考虑了这些效应后计算值得到明显改善.     

光纤模式混合器在差分吸收光谱系统中的应用研究

差分吸收光谱技术(DOAS)已经发展为监测对流层痕量气体的重要技术，一般采用光电倍增管(PMT)作为探测器.由于光电二极管阵列(PDA)在多道探测及像元灵敏性方面的优势，采用PDA代替扫描探测装置将能改善系统剩余噪声，提高系统性能.但实际应用中由于使用收发一体Cassegrain望远镜造成灯谱与大气谱结构不统一，在消除PDA像元间差异的过程中给系统带来误差，从而导致剩余噪声的标准偏差达到1.4×10^-3.根据光纤扰模原理在系统中加入自制光纤模式混合器很好的解决了上述难题，在实际应用中起到良好的作用，系统剩余噪声的标准偏差为3.4×10^-4. 关键词： 差分吸收光谱 扰模 模式混合器 剩余噪声     

Optimal Conditions for Existence of Vesicles Under Electric Field

Giant vesicles have been of intense interest as the model system for cell membranes. To bring numerous applications of the vesicles into full play, the existence time of the vesicles becomes particularly important. In this work, we explored the existence time of the vesicles in distilled water under four kinds of representative alternative current (AC) electric fields with different energizing time. When the application time of AC electric field reached 1 hour, the existence time of the vesicles reached the maximum value. As the applied electric field time increased, the existence time of the vesicles decreased. Thus, after obtaining the best vesicles on the carbon fiber electrode, disconnecting the external electric field is very necessary. Based on the in situ observation using inverted microscope, the disappearing phenomena of the vesicles were presented. In addition, it is found that vesicles in phosphate buffer solutions (PBSs) can last about 2–3 days when the electric field was applied for 1 hour, which was much longer than that in distilled water.     

在SQUID心磁测量中基于奇异值分解和自适应滤波的噪声消除法

采用矩阵奇异值分解(singular value decomposition, SVD)的方法，对高温射频超导量子干涉仪(HTc rf-SQUID)采集到的单通道心磁信号进行处理.证明了对于近似周期性的心磁信号，在无参考噪声的情况下矩阵奇异值分解的方法与自适应窄带陷波相结合有较好的消除广谱噪声的效果. 关键词： 高温射频超导量子干涉仪 心磁信号 奇异值分解 噪声消除     

用于乙烯环氧化反应的CuCs掺杂银基催化剂设计

最近的理论研究筛选出CuCs掺杂Ag基催化剂是一种高效的乙烯环氧化催化剂[ACS Catal. 11,3371 (2021)]. 然而,该工作是基于研究表面建模预测Ag基催化剂的性能,在实际反应过程中,Ag基催化剂是颗粒状的. 本文结合密度函数理论、Wulff构造理论和微观动力学分析来研究Ag基催化剂在颗粒模型上的催化性能. 研究表明,CuCs掺杂Ag基催化剂在选择性和活性方面都优于纯Ag基催化剂,这一点通过实验得到了证明. 进一步地表征分析发现,CuCs掺杂能促进颗粒的生长以及颗粒的分散,从而形成富含晶界的Ag颗粒. 此外,CuCs促进了催化剂表面亲电氧的形成,这均有利于环氧乙烷的形成和解吸. 本工作为理论与实验相结合的催化剂设计提供了一个案例研究.     

电子束在等离子体微波器件中的脉动

 对填充等离子体漂移空间小脉动电子束进行了近似分析,对大脉动电子束进行了较精确的计算,结果表明虽然α区和β区束的脉动性能各不相同,但幅度和波长均受限于电子入射的初始条件和等离子体参数,当其它条件给定后存在一最佳等离子体填充密度。     

Corrosion inhibition of ammonium molybdate for AA6061 alloy in NaCl solution and its synergistic effect with calcium gluconate

The corrosion inhibition of ammonium heltamolybdate (AH) and calcium gluconate (CG) for AA6061 alloy in 3% NaCl solution was investigated by the electrochemical measurements. It indicates that AH inhibits the corrosion of AA6061 alloy and acts as an anodic inhibitor. Maximum inhibition efficiency reaches 74.3% at the concentration of 1 × 10^?4 mol.l^?1 AH. The results of the electrochemical studies reveal AH is physically adsorbed on the AA6061 alloy surface and the adsorption follows Langmuir isotherm. The combination of AH and CG enhances the inhibition efficiency to 95.9%. The enhanced inhibition is attributed to the promotion of AH adsorption by CG. The mixture of AH and CG is a mixed‐type inhibitor and renders the corrosion potential to more positive values. Copyright © 2011 John Wiley & Sons, Ltd.     

Nanoscale Broadband Viscoelastic Spectroscopy of Soft Materials Using Iterative Control

A novel approach to nanoscale broadband viscoelastic spectroscopy is presented. The proposed approach utilizes the recently developed modeling-free inversion-based iterative control (MIIC) technique to achieve accurate measurement of the material response to the applied excitation force over a broad frequency band. Scanning probe microscope (SPM) and nanoindenter have become enabling tools to quantitatively measure the mechanical properties of a wide variety of materials at nanoscale. Current nanomechanical measurement, however, is limited by the slow measurement speed: the nanomechanical measurement is slow and narrow-banded and thus not capable of measuring rate-dependent phenomena of materials. As a result, large measurement (temporal) errors are generated when material is undergoing dynamic evolution during the measurement. The low-speed operation of SPM is due to the inability of current approaches to (1) rapidly excite the broadband nanomechanical behavior of materials, and (2) compensate for the convolution of the hardware adverse effects with the material response during high-speed measurements. These adverse effects include the hysteresis of the piezo actuator (used to position the probe relative to the sample); the vibrational dynamics of the piezo actuator and the cantilever along with the related mechanical mounting; and the dynamics uncertainties caused by the probe variation and the operation condition. In the proposed approach, an input force signal with frequency characteristics of band-limited white-noise is utilized to rapidly excite the nanomechanical response of materials over a broad frequency range. The MIIC technique is used to compensate for the hardware adverse effects, thereby allowing the precise application of such an excitation force and measurement of the material response (to the applied force). The proposed approach is illustrated by implementing it to measure the frequency-dependent plane-strain modulus of poly(dimethylsiloxane) (PDMS) over a broad frequency range extending over 3 orders of magnitude (~1 Hz to 4.5 kHz).     

Micromechanical analysis of damage in saturated quasi brittle materials

In this paper, we propose a micromechanical analysis of damage and related inelastic deformation in saturated porous quasi brittle materials. The materials are weakened by randomly distributed microcracks and saturated by interstitial fluid with drained and undrained conditions. The emphasis is put on the closed cracks under compression-dominated stresses. The material damage is related to the frictional sliding on crack surface and described by a local scalar variable. The effective properties of the materials are determined using a linear homogenization approach, based on the extension of Eshelby’s inclusion solution to penny shaped cracks. The inelastic behavior induced by microcracks is described in the framework of the irreversible thermodynamics. As an original contribution, the potential energy of the saturated materials weakened by closed frictional microcracks is determined and formulated as a sum of an elastic part and a plastic part, the latter entirely induced by frictional sliding of microcracks. The influence of fluid pressure is accounted for in the friction criterion through the concept of local effective stress at microcracks. We show that the Biot’s effective stress controls the evolution of total strain while the local Terzaghi’s effective stress controls the evolution of plastic strain. Further, the frictional sliding between crack lips generates volumetric dilatancy and reduction in fluid pressure. Applications of the proposed model to typical brittle rocks are presented with comparisons between numerical results and experimental data in both drained and undrained triaxial tests.