激光引信数据采集处理系统的研制

文中介绍了为建立目标和背景的激光反射特性数字模型而研制的用于脉宽几十纳秒的数据采集系统的设计和工作方式。针对测量窄脉冲信号幅值及实现不间断连续采集过程的使用目的,将窄脉冲回波信号的身值展宽成100us的方波,以系统设置的发射 基信号或回波信号自身作为采集的同步控制信号,并将基准信号展宽为5-50us的方波,以其上升沿触发采集,实现发射与采集同步,提高了采集存储的有效性;而且,在作用距离范围内,不管目标或背景位于多远处,都能保证于脉宽峰值处采集,保证了采集精度。系统的各项技术指标均达到使用要求并经过了测试试验验证。     

高展宽量八通展宽器的设计制作

在啁啾脉冲放大(CPA)技术中,提高展宽器的展宽量能有效地提高激光器的输出能力,而展宽器的展宽量与其构型及参数设计紧密相关,因此可以通过构型的选取及参数的优化来提高展宽器的展宽量。用光线追迹法导出了单光栅单透镜展宽器构型的设计解析式,利用这些解析式可以进行展宽器参数的优化,在此基础上设计制作了高展宽量的八通展宽器,并利用所研制的展宽器,将中心波长为1053 nm的93 fs脉冲展宽到4.35 ns。在该构型展宽器中,通过控制焦平面反射镜处的光强分布可以较方便地进行光谱整形,在实验中得到了和声光色散滤波器整形后类似的中心凹陷的波形。     

拉伸速度及其他参数变化对束纤维细化过程的影响

羊毛拉伸细化中,拉伸的速率对分子的构象和滑移影响重大,不仅会造成拉伸力过大形成冲击和损伤,而且会导致能耗大,结构不稳定。利用自行设计的拉伸细化过程测量装置,实时测量了羊毛纤维条拉伸的力学行为,并在此基础上讨论和分析了拉伸速度、毛条捻度、握持距离等不同拉伸工艺条件对纤维细化过程的影响,验证了控制拉伸速度的重要性。     

Fabrication of large area flexible and highly transparent film by a simple Ag nanowire alignment

This article describes the fabrication of a flexible polymer thin film incorporating a highly aligned Ag nanowire array, resulting in high transparency and polarisation that are useful for potential applications to optical filters, electronic and optical devices and negative refractive index materials.     

Structural modifications in stretch-induced crystallization in PVDF films as measured by small-angle X-ray scattering

The nanostructure of stretched and nonstretched PVDF samples was studied by small-angle X-ray scattering (SAXS). The crystallinity of the samples was determined by wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC), and crystalline phases by Fourier transform infrared spectroscopy (FTIR). The nanostructure can be described by a lamellar stacking of crystalline and amorphous layers, with a fairly well defined long period D and a diffuse-boundary in the interface between the crystalline and amorphous phases. The crystallinity of the stretched sample was found to be greater than that of the nonstretched sample. The long period D and the thicknesses of the crystalline lamellae T_c were found to be greater in the stretched sample than those in the nonstretched sample. The thickness of the diffuse-boundary was evaluated as being ∼ 1.4 nm in the nonstretched sample and 1.1 nm in the stretched sample. It was concluded that the growth of the thickness of the crystalline layer induced by the stretching process (stretch-induced crystallization) occurs partially at expense of the diffuse boundary and also by the coarsening of the structure with the stretching process, because of the diminution in the surface area to volume ratio observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Increasing nano‐particle dispersion ratio in the bubble stretching‐based technique

We present a new method to increase nano‐particle migration rate in bubble stretching‐based technique. Vibration created by the inflation and shrinking process of bubbles is used. Process parameters can be adjusted to increase the probability of collision between the nano‐particles and the bubble wall. In effect, particles sufficiently migrate to the bubble wall, increasing both particle migration rate and dispersion ratio. Our measurement show that: (1) particle diameter, initial bubble radius, and initial bubble pressure strongly influence the migration of particles; (2) with appropriate parameters, nano‐particles can quickly and efficiently migrate to the bubble wall through this new method. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Magnetohydrodynamics boundary layer flow and heat transfer in porous medium past an exponentially stretching sheet under the influence of radiation

Buoyancy forces result from the cooling or heating of a continuous stretching sheet, which causes a change in the resulting flow and thermal fields, and hence the heat transfer behavior in the manufacturing process. The study of the thermal buoyancy induced in boundary layer flow is important due to its recent advances in the areas of nuclear energy, electronics, and space technology. In this perspective, the aim of the present study is to investigate the effect of the buoyancy parameter on the magnetohydrodynamics boundary layer flow over an exponentially stretched sheet in the presence of nonlinear thermal radiation and porous media. Using similarity transformation, the flow model of partial differential equations is transformed into a set of coupled nonlinear ordinary differential equations. The efficient fourth‐order Runge‐Kutta scheme with the shooting method is used to solve the reduced equations. The impact of various associated parameters on velocity and temperature profiles were analyzed and computed through graphs. The major outcome of the present study shows the enhancement in the velocity distribution with the increase in the buoyancy parameter. Also, the increase in thermal buoyancy and thermal radiation leads to an increase in fluid temperature. Moreover, it is worth to note that the fluid velocity declines with the augmentation of the magnetic parameter.     

Heat transfer in a fluid through a porous medium over a permeable stretching surface with thermal radiation and variable thermal conductivity

This paper treats about the flow and heat transfer of a viscous incompressible fluid in a porous medium over a permeable stretching surface taking into account thermal radiation and the variation of the thermal conductivity with temperature. Analytical solutions for the stream function are obtained and two cases are studied, namely, (i) prescribed surface temperature (PST case) and (ii) prescribed heat flux (PHF case). The effects of Prandtl number, permeability, suction/blowing, variable thermal conductivity, thermal radiation and surface temperature parameters on heat‐transfer characteristics are shown through tables and graphs and discussed. Ce document concerne l´écoulement et le transfer de chaleur dans le cas d´un fluide visqueux incompressible dans un milieu poreux sur une poreux surface s´étendant en tenant compte de la radiation thermique et de la conductivité thermodépendante. Les solutions analytiques pour la fonction de courant sont obtenus et deux conditions à la frontière pour la tempèrature et le flux de chaleur sont apliquées: (i) predicted surface tempèrature (PST) et (ii) le flux de chaleur predicted (PHF). Les effects du nombre de Prandtl, perméabilité, succion/soufflage, conductivité thermodépendante, radiation thermique et de la surface tempèrature sur le transfer de chaleur sont indiqués dans des tableaux et des graphiques, puis sont discutés. © 2011 Canadian Society for Chemical Engineering     

非对称双曲面线形离子阱的设计及性能研究

为提升离子阱质量分析器的分析性能,本文提出一种非对称双曲面线形离子阱结构,通过优化离子出射方向上x电极的单向拉伸距离Δr_a,引入合理的非对称射频电场,从而提高离子单向出射效率。利用SIMION和AXSIM模拟软件分析非对称双曲面线形离子阱的内部电场分布、离子运动轨迹及模拟质谱图。结果表明,在性能优化的对称双曲面线形离子阱结构的基础上,其中1个x电极单向拉伸Δr_a=0.8 mm时,通过优化AC频率和扫描速率等参数,非对称双曲面线形离子阱的离子单向出射率可达90%以上,同时m/z 609离子的质量分辨率超过5 100。经优化几何结构后的非对称双曲面线形离子阱可在保证高质量分辨率的情况下,大幅提高离子检测效率,这在小型化质谱仪的开发中具有显著的优势。