对激光等离子体中X射线的产生与辐射加热研究

利用一维辐射流体力学程序MULTI数值模拟研究了功率为1014Wcm2、脉冲宽度为300ps、波长为0.44μm的强激光辐照平面Au靶时产生X射线的过程,给出了X射线转换效率和能谱分布.通过将靶物质划分为对所产生的X射线光学薄的转化区和光学厚的再发射区,得到了作为黑体辐射热源的最佳靶厚度,并给出了辐射加热靶所产生的等离子体的密度和温度的空间分布. 关键词： 辐射流体力学 激光等离子体 X射线转换 辐射热波     

Comparison of detection efficiencies of negatively charged gold-alkanethiolate-, gold-sulfur- and gold-clusters in ToF-SIMS

In order to improve quantification of high mass ions, the influence of cluster composition on detection efficiencies has been studied using a TOF-SIMS IV with the extended capability of postaccelerating ions up to 20 keV. In this experimental study, we focus on the comparison of detection efficiencies for three types of negatively charged secondary cluster ions: gold-alkanethiolate-clusters (Au_xM_y), gold-sulfur-clusters (Au_xS_y) and gold-clusters (Au_x). The clusters were sputtered from self-assembled monolayers of hexadecanethiols on gold substrates using 10 keV Ar⁺ primary ions. The detection efficiencies were derived on the basis of a function for the secondary electron yield and a fourth-order approximated Poisson probability distribution for electron propagation and amplification within the microchannel plate.In addition to the well-known dependence of detection efficiencies on ion mass and energy, which has already been studied for positively charged ions, we were able to show a similar behaviour for the investigated negatively charged secondary ions. We have observed major variations among the three types of clusters at similar mass and energy as predicted in a theoretical approach. The observed differences are due to the different composition of the investigated clusters which has a major influence on the kinetic ion induced electron emission within the microchannel plate. For the first time it was possible to experimentally verify these predictions for detection efficiencies.     

Electrochemical impedance spectroscopy and linear polarization applied to evaluation of porosity of phosphate conversion coatings on electrogalvanized steels

In this work, electrochemical impedance spectroscopy and linear polarization are used in determining porosity of zinc phosphates, and of nickel and manganese modified zinc phosphates on electrogalvanized steel. The porosity of the phosphate layers ranges from 0.1% for the manganese-modified hopeite to 8% for hopeite, using the linear polarization and the electrochemical impedance spectroscopy techniques. The porosity values measured using the two techniques were in agreement. All impedance spectra of coated samples showed two steps, with two capacitive arcs and an inductive looping.     

输入输出共轴的三弯曲型TM01-TE11模式转换器

 通过采用相位重匹配技术，设计了一种输入输出共轴的三弯曲型TM₀₁-TE₁₁模式转换器，该转换器由三段常曲率弯曲波导和两段直波导组成。用模式耦合理论建立了该类模式转换器的数值计算和优化设计方法，并设计了一个中心频率为7.0 GHz的模式转换器。该转换器的TM₀₁-TE₁₁转换效率在中心频率上大于99％，在6.5~7.5 GHz的频率范围内大于90％。应用时域有限差分法和有限元方法对所设计的模式转换器进行了仿真，仿真结果验证了设计理论和设计结果。     

Amorphous Fe–Mg alloy thin films: magnetic properties and atomic vibrational dynamics

Amorphous (a-) Fe _x Mg_1?x alloys are interesting materials for the investigation of non-Debye-like low-energy vibrational excitations. We have prepared a-Fe _x Mg_1?x alloy thin films (0.3 ≤ × ≤0.7) by vapour quenching. The amorphous state was confirmed by conversion electron Mössbauer spectroscopy between 4.2–300 K, and the x- and temperature-dependence of the isomer shift and hyperfine magnetic field was measured. For x= 0.6 and 0.7, magnetic ordering occurs below ~150 K. The atomic vibrational density of states, g(E), was determined by nuclear resonant inelastic scattering, providing clear evidence for the non-Debye-like low-energy vibrational excitations.     

Enhancement of Overall Photovoltaic Efficiency by Changing the Position of the Attaching Group -RSO3- on the Hemicyanine Dye Molecules

A new photoresponsive D-π-A dye, mPS, has been designed and synthesized.Compared to the parent dye PS, IPCE values in the region from 400 nm to 560 nm was greatly improved upon changing the attaching group from the p- position to the o- position of the π-conjugation bridge. A solar cell based on mPS generated a remarkably high overall yield η of 5.4% under irradiation of 80.0 mW cm^-2 white light from a Xe lamp, Compared with PS, the overall yield η increased by 64%.     

IPv4/IPv6翻译网关的研究

In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000.     

Combined X-ray-electron imaging techniques: Limitations on lateral resolution

Capabilities of the imaging techniques, in which X-rays are converted to electrons and then the emitted electrons are registered by means of an electron microscope, are analyzed, the focus being on the factors limiting lateral resolution at the stage of electron emission. Bearing in mind the tendency to use harder synchrotron X-rays for some combined X-ray-electron microscopy methods, calculations were made for two significantly different X-ray energies: E = 1.828 keV (K-edge of Si) and E = 11.923 keV (L₃-edge of Au). By using Monte Carlo simulations of the electron trajectories beneath the surface of the sample we show that the radius of the spot from which photoelectrons are emitted could be as small as 1 nm. However, when proper account is taken of an entire electron cascade associated with the re-building of electron shells after photoelectron emission, spots more than one order of magnitude larger result, limiting the best lateral resolution to 20–30 nm.     

Further study of the viscoelastic phase separation of cyanate ester modified with poly(ether imide)

In this study, the viscoelastic phase separation process was studied further by time‐resolved light scattering, differential scanning calorimetry, and scanning electron microscopy in the system of poly(ether imide)‐modified bisphenol‐A dicyanate. It was observed that the evolution time of phase structure and relaxation time of diffusion flow of the bisphenol‐A dicyanate were similar with the phase diagram of curing conversion versus content of PEI. The results suggested that the viscoelastic phase separation was affected by the curing conversion of the system at the onset point of phase separation. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 517–523, 2006     

Monitoring hydration state conversion by TG-DTA

Characterization of the solid-state form (hydrate or polymorph) of a pharmaceutical active is a key scientific and regulatory requirement during development of and prior to seeking approval for marketing of the drug product. A variety of analytical methods are available to perform this task. By nature of the fundamental information it provides, TG-DTA offers advantages over other methods in regards to monitoring and quantitation of hydration state changes. In a single experiment with only a few milligrams of sample, TG-DTA perceives minor changes in phase, quantitates total water content and percent conversion, and illustrates hydrate type. All of this is accomplished without the necessity of generating time-consuming standard curves representing the differing ratios of hydrated to anhydrous forms. This study describes the use of TG-DTA to monitor and quantitate humidity induced solid–solid phase conversion of nitrofurantoin and risedronate. Percent conversion was qualitatively observed by both TG and DTA signals and quantitated by the TG.