The relation between composition in laser absorption region and ambient pressure

In this paper, the compositions in a laser absorption region can be determined from the experiment of laser impulse coupling. When the ambient pressure varies from 9325 to 33325Pa, the compositions are vapour and plasma; while from 35325 to 101325Pa, they are ambient air and plasma. By analysing the relation between the degree of compression and the ambient pressure, the compositions can be determined and the variation of plasma can be explained.     

多脉冲激光对K9玻璃的表面损伤实验研究

 实验研究了波长为1 064 nm、脉宽为10 ns、重复频率为1 Hz的激光脉冲对K9玻璃的表面损伤特点,给出了脉冲透过能量随激光脉冲作用次数变化的规律。采用3维立体显微镜对损伤形貌进行观察,发现K9玻璃的损伤表面呈环状分布,分为烧蚀区、微裂纹区和断裂区。随着激光脉冲个数的增加,损伤由点状破坏演变为损伤区,微裂纹逐渐增长,损伤面积逐渐增大。基于激光支持的爆轰波理论分析,激光与脆性材料的相互作用可引起微裂纹的大量增长。在多脉冲激光的作用下,K9玻璃损伤的累积效应明显,表面损伤阈值明显降低,表面裂纹增长明显,损伤面积逐渐增大;但随着激光脉冲的继续增加,这种损伤趋于稳定。     

椰心叶甲虫综合防治脉冲动力学模型的周期解

椰心叶甲虫是棕榈科植物最主要的害虫之一.论文针对两类寄生蜂攻击椰心叶甲虫不同年龄阶段的特点,建立了阶段结构的脉冲定期喷洒药物和释放天敌的综合防治模型.通过重合度理论和分析工具,证明了该模型周期解的存在性,给出了周期解存在的充分条件,并通过数值模拟验证了理论结果的有效性.     

Experimental research on the localized electrochemical micro-machining

Due to several advantages and wider range of applications, micro-ECM is considered to be one of the most effective advanced future micromachining techniques. An experimental set-up for micro-ECM is constructed, which consists of various components and sub-systems, e.g. mechanical machining unit, nanosecond pulse power supply, circulation system of electrolyte, movement control component and process monitoring component. In addition, this system has the functions of fabricating micro tool electrode and machining status detection. Using the self-developed experimental system, the micro tool-electrode and the micro holes are sequentially machined. Upon the application of ultrashort voltage pulses, micro hole with 20μm diameter is obtained. Experimental results show the potential capability of electrochemical micromachining for better machining accuracy and smaller machining size. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 8, pp. 998–1003. The text was submitted by the authors in English.     

具非线性扩散项的脉冲抛物方程的强迫振动性

研究一类具非线性扩散项的脉冲抛物型方程解的强迫振动性问题,借助平均技巧和脉冲微分不等式,建立了该类方程在Dirichlet边值条件下所有解强迫振动的若干新的充分判据.结论充分表明振动是由脉冲效应引起的.     

相关技术在滚动轴承故障诊断中的应用

众所周知自相关技术能够有效地从随机嘈声中提取周期性信号.在滚动轴承元件的故障诊断中,由于信号图象不同,我们无法从原信号直接得到故障的情况,这种信号的显示就像宽频带随机嘈声在自相关函数的显示一样.本文中,信号经过了预处理,其结果证明是行之有效的.应用自相关技术我们还可以得到已测定的可比采样,这对于建立轴承运行条件的数据基础和进行故障诊断是十分重要的.     

惰气脉冲熔融热导法测定铌钛合金中氢含量

为准确测定铌钛合金中氢含量,使用LECO-404氢分析仪,采用惰性气氛脉冲加热熔融试样,热导法测定。研究了不同的脱气功率对空白值和试样分析值的影响,选择了脱气功率为4 500 W。通过助熔剂实验,选择了0.50g锡作为铌钛合金中氢释放的助熔剂。验证了钛标准样品的适用性。确定了分析功率为3 500 W,最短积分时间为60s。精密度实验中氢含量测定的相对标准偏差(RSD)为2.5%~5.5%,加标回收率为97.82%~104.5%,可以准确测定铌钛合金中氢含量。研究结果对准确测定铌钛合金中氢含量具有指导意义。     

Pulse Duration Dependent Asymmetry in Molecular Transmembrane Transport Due to Electroporation in H9c2 Rat Cardiac Myoblast Cells In Vitro

Electroporation (EP) is one of the successful physical methods for intracellular drug delivery, which temporarily permeabilizes plasma membrane by exposing cells to electric pulses. Orientation of cells in electric field is important for electroporation and, consequently, for transport of molecules through permeabilized plasma membrane. Uptake of molecules after electroporation are the greatest at poles of cells facing electrodes and is often asymmetrical. However, asymmetry reported was inconsistent and inconclusive—in different reports it was either preferentially anodal or cathodal. We investigated the asymmetry of polar uptake of calcium ions after electroporation with electric pulses of different durations, as the orientation of elongated cells affects electroporation to a different extent when using electric pulses of different durations in the range of 100 ns to 100 µs. The results show that with 1, 10, and 100 µs pulses, the uptake of calcium ions is greater at the pole closer to the cathode than at the pole closer to the anode. With shorter 100 ns pulses, the asymmetry is not observed. A different extent of electroporation at different parts of elongated cells, such as muscle or cardiac cells, may have an impact on electroporation-based treatments such as drug delivery, pulse-field ablation, and gene electrotransfection.     

Numerical simulation on the operational characteristics of the pulsed inductive acceleration

To analyse the ionization and acceleration properties of an inductive plasma excited by a pulsed current flowing through the planar coil, the extended GLM formulations of the MHD (EGLM‐MHD) model, combined with the high‐temperature thermodynamic and transport model, is employed to simulate the characteristics of the flow. The two‐dimensional axisymmetric calculation captures the generation, growth, and acceleration of the current sheet, and the process is completed in the first half period. The sheet is mainly comprised of lower ionization level ions in the front and higher level ions at the back, and the density is one order higher than that of the residual plasma on the coil surface. As the abscissa value of the sheet is larger than the decoupling distance, a reversed flow emerges, generating a backward impulse, and the negative velocity can be more than 15 km/s at peak intensity B₀ = 0.5 T. In the second 1/4 period, the magnetic field and current density distribute non‐linearly on the surface and regularly in the sheet, caused by the reversing of the changing rate of the magnetic field and the particles' radial diffusion. The results at different intensities show that, for the same coil size, the time at which the maximum velocity V_max appears is advanced as the intensity increases, and V_max can be greater than 20 km/s above 0.5 T.