基于异步时序的高帧频相机垂直拖尾处理

介绍一种高帧频相机垂直拖尾影响的解决方法,该方法同时考虑连续采集模式下帧间图像和像元合并（binning）技术的影响。与常用的静态图像拖尾处理的算法如逆向逐行修正算法相比,该算法非常适用于连续图像拖尾处理,特别是经过Binning后获取的图像。在某自主研制的基于异步时序的40 000 帧/秒高速相机中应用该方法,有效去除了拖尾影响。最后,运用该方法处理的图像验证了算法的有效性。     

束流发射度对太赫兹微电真空折叠波导行波管性能的影响

采用理论分析与数值模拟相结合的方法,分别对140,220和345 GHz折叠波导行波管中的束流发射度的影响因素及其对直流导通率的影响进行了分析,总结了发射度随频率、结构参数和电子束参数的变化规律。研究发现,在太赫兹频段束流发射度直接决定着聚焦磁场的选取设计, 是表征太赫兹频段束流品质的一个重要参量。     

回旋加速器束测探头感生放射性实验研究

基于束流沉积法测量回旋加速器内部束流参数将在束测探头上产生感生放射性污染,从而对加速器调束工作人员带来不必要的辐射危害。采用AGM-6型监测仪对探头感生放射性进行在线测量,通过测量不同半径处探头受辐射后的空气比释动能率,间接反映探头感生放射性的强弱和危害。研究结果表明,在束流调试实验中,应尽量降低馈入高频的占空比;探头测量后冷却2~3 h取出,则不需要考虑测量探头辐照后的残留感生放射性的危害。     

Double Electrical Layer at the Plasma‐Solution Interface

Plasma‐solution interface plays the important role in the systems of the electrical discharges with or in liquids (electrolyte solutions). Processes, which pass at this interface, influence on as plasma as liquid. In this paper, the theoretical and experimental results of studies of the double layer on the liquid surface are presented. Data of cathode region properties, kinetics of nonequilibrium vaporization, correlation between radiation intensity and fluxes from electrolyte cathode surface and energy consumptions per on one water molecule transfer are summarized. It is able to suggest the transfer mechanism at the plasma‐solution interface. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Diffusion tensor parameters and principal eigenvector coherence: Relation to b-value intervals and field strength

Diffusion-weighted MRI images acquired at b-value greater than 1000 s mm^− 2 measure the diffusion of a restricted pool of water molecules. High b-value images are accompanied by a reduction in signal-to-noise ratio (SNR) due to the application of large diffusion gradients. By fitting the diffusion tensor model to data acquired at incremental b-value intervals, we determined the effect of SNR on tensor parameters in normal human brains, in vivo. In addition, we also investigated the impact of field strength on the diffusion tensor model. Data were acquired at 1.5 and 3 T, at b-values 0, 1000, 2000 and 3000 s mm^− 2 in twenty diffusion-sensitised directions. Fractional anisotropy (FA), mean diffusivity (MD) and principal eigenvector coherence (κ) were calculated from diffusion tensors fitted between datasets with b-values 0–1000, 0–2000, 0–3000, 1000–2000 and 2000–3000 s mm^− 2. Field strength and b-value effects on diffusion parameters were analysed in white and grey matter regions of interest. Decreases in FA, κ and MD were found with increasing b-value in white matter. Univariate analysis showed a significant increase in FA with increasing field strength in highly organised white matter. These results suggest there are significant differences in diffusion parameters at 1.5 and 3 T and that the optimal results, in terms of the highest values of FA in white matter, are obtained at 3 T with a maximum b = 1000 s mm^− 2.     

Gd2(WO4)3: Eu纳米发光材料中黄昆因子和能量传递速率的实验获得

采用共沉淀法制备了不同Eu³⁺掺杂浓度的Gd₂(WO₄)₃纳米发光材料. 测量了纳米材料样品的X射线衍射谱(XRD) 和场发射扫描电镜, 对样品的结构和形貌进行了表征. 测量了各样品的发射光谱和激发光谱(声子边带光谱), 绘制了浓度猝灭曲线, 确定了最佳的掺杂浓度为20 mol%. 通过声子边带光谱计算了不同掺杂浓度样品的黄昆因子. 测量了不同浓度样品的荧光寿命, 利用Auzel模型对Eu^{3+ 5}D₀能级荧光寿命数据进行了拟合, 确定了⁵D₀能级的固有寿命和猝灭过程中生成的声子数. 本文还根据荧光寿命数据计算了Eu³⁺之间的能量传递速率, 确定了能量传递速率与浓度的关系. 关键词： 钨酸盐 3+')" href="#">Eu³⁺ 黄昆因子 能量传递速率     

A molecular dynamics simulation study on the cavitation inception of water with dissolved gases

The promotion/prevention mechanism of dissolved gases on cavitation inception is essential for many high-tech industries and research. In the present study, large-scale molecular dynamics simulations are performed to investigate the effects of water cavitation caused by different gas types by using nitrogen and oxygen gases with TIP4P/2005 water. The cavitation inception behaviour is analyzed via Mean First Passage Time method. Water with dissolved gases has a higher nucleation rate and is easier to cavitate than pure water. At the same gas concentration, the cavitation of water with nitrogen is promoted to a greater extent than that with oxygen. The number and energy of hydrogen bond (HB) are further calculated by the Acceptor-Hydrogen-Donor method to explain this promotion mechanism. The number and energy of HB in water with gases decrease compared with those in pure water. The introduction of gases weakens the HB network and promotes cavitation inception because of weaker interactions between gas and water molecules. A model is developed to describe the relationship between nucleation rate and HB energy. Gas molecules assemble on the surface of bubbles during water cavitation, which may decrease the free energy of bubble surface, maintain the existing bubble, and contribute to the growth process.     

Buckled nano rod – a two state system: quantum effects on its dynamics

We consider a suspended elastic rod under longitudinal compression. The compression can be used to adjust potential energy for transverse displacements from the harmonic to the double well regime. The two minima in potential energy curve describe two possible buckled states. Using transition state theory (TST) we have calculated the rate of conversion from one state to other. If the strain ? = 4? _c the simple TST rate diverges. We suggest a method to correct this divergence for quantum calculations. We also find that zero point energy contributions can be quite large so that single mode calculations can lead to large errors in the rate.     

Dose rate effect of gamma on JFET transistors

Dose rate effects on the noise characteristics of gamma-irradiated junction field effect transistors (JFETs) are presented. The dose rate varied between 0.5 and 19 kGy/h at a constant radiation dose of 600 kGy. Neither obvious nor non-general relationship was identified between noise and dose rate along the total dose rate range. Nevertheless, some explanations have been provided about the resulting effects when the total range was studied, as some partial ranges corresponded to low, medium and high dose rates. This explanation is based on the gamma interaction process in JFET structure and the electronic noise resulted.     

Natural radionuclide concentrations in soils around Baoji coal-fired power plant,China

Radionuclides are released together with fly ash from the coal-fired power plant and thus add to the natural radiation. Fifty soil samples were collected around the Baoji coal-fired power plant from 25 locations and the natural radionuclide concentrations were determined by a gamma ray spectrometric system. The results show that the activity concentrations in soil samples range from 12.54 to 40.18 Bq kg^?1, 38.02 to 72.55 Bq kg^?1 and 498.02 to 1126.98 Bq kg^?1 for ²²⁶Ra, ²³²Th and ⁴⁰K with the mean values of 27.35, 52.66 and 764.72 Bq kg^?1, respectively. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Ra_eq), the absorbed dose rate (D) and the annual effective dose rate have been calculated and compared with the internationally approved values. The radium equivalent activity in all the soil samples is lower than the safe limit set in the Organization for Economic Cooperation and Development report (370 Bq kg^?1). The average value of the calculated dose rates is higher than the global average value 55 nGy h^?1, and the calculated annual effective dose rate is significantly lower than the average annual external effective dose rate (460 μSv y^?1) of the normal background radiation.