A laser Doppler tomography method for investigating volume recording media

A laser Doppler tomography method is proposed for investigating scattering noises, shrinkage, modulation amplitudes of refractive index and absorption coefficient, and other characteristics of volume or thick recording media. The method is based on acoustooptical scanning of a test volume grating recorded earlier in the medium and on layer-by-layer collinear heterodyne detection of the scattered field. The optoelectronic scheme of the system intended for experimental validation of the method is considered. Formulas for estimating the spatial resolution of the method, the optimal test grating period, the maximal number of detected layers are obtained. Their dependence on the optical system grating parameters is shown. An example is reconstructed values of the amplitude and phase of scattered light in deep layers of a volume grating written in a photopolymer 130 µm thick.     

Evaluation of the maximum speed of layer-by-layer heterodyne analysis of light scattering characteristics in volume optical media

A method of layer-by-layer heterodyne analysis of volume optical media is described. The results of a theoretical evaluation, computer modeling, and experimental investigation of the dependence of the maximum speed of the analysis on the parameters of the optical circuit and medium are given. The effect of the analysis speed on the resolution of the method along the thickness of the optical medium and on the pattern of the dependence of the output signal on the depth of the studied layer is evaluated. A method for increasing the maximum scanning speed is proposed. The obtained results are confirmed experimentally..     

Tribological issues in perpendicular recording media

As the hard disk drive industry is transitioning from longitudinal (LMR) to perpendicular (PMR) recording, a new set of reliability challenges had to be overcome. In particular, the magnetic media structure, which relies on well-segregated grains of 6–10 nm diameter, can exhibit a rough structure, with peak-to-mean amplitude of 3–6 nm. In this paper, we will discuss how this topography could affect the overall reliability of the head–disk interface. In the first part, we will illustrate the loss of adequate coverage from the overcoat on PMR media, compared to the smoother LMR media, and we will attempt to quantify the topography in terms of its deviation from a Gaussian height distribution. Particular emphasis will be given to surface outliers and their removal during the burnishing process. The second part will be devoted to the lubricant preferential migration to the grain boundaries, driven by surface tension. It will be shown by an EELS line scan that the lubricant film is indeed thicker in the valleys between the grains, in agreement with surface tension driven redistribution. Finally, we will demonstrate that the Touchdown Height (TDH) of a PMR disk is ∼0.5 nm higher than its LMR counterpart, owing to its enhanced nano-roughness. Once recognized, these challenges can be overcome through a careful and thorough optimization of the various processing parameters, eventually leading to an overall reliability level equal or better than LMR media.     

A study of microstructures and mechanical properties of laser welded joint in GH3030 alloy

In this paper, we represent experimental laser welding of GH3030 alloy. The microstructure and mechanical properties of laser welded joints were investigated using an optical microscope, scanning electron microscope, energy diffraction spectrum and other methodologies. The results demonstrated that the weld primarily involved slender dendrites together with a small number of equiaxial crystals. The occurrence of porosities was mainly associated with the composition of the material itself. The cracks in the HAZ were induced by lowmelting- point eutectic phases that formed during laser welding. The segregation of the alloying elements in the matrix induced the variation of the performance within the joint. The average strength of welded joints was 646 MPa, 97.6 % of that of the base metal. Formation of inclusions and micropores in the fusion zone weakened the joint strength greatly.     

磨削粗糙度在线检测方法的实验研究

本文对基于摩擦声发射信号的磨削粗糙度在线检测方法进行了实验研究。实验结果表明，采用声发射传感器探头与磨削表面摩擦产生的声发射信号的特征可以对磨削表面粗糙度进行评价，建立了摩擦声发射信号特征与磨削表面粗糙度之间的对应关系，并通过实验对该方法的可行性进行了实测。结果表明，探针与工件表面摩擦声发射信号的FFT和RMS特征与磨削粗糙度有很好的对应关系，可用于磨削表面粗糙度的在线检测。     

Micro laser welding of polymer microstructures using low power laser diodes

The use of laser welding for joining micro parts has experienced a substantial increase in popularity during recent years. Specifically translucent microfluidic devices are assembled using laser welding; however, a major issue is the laser beam size of commercially available laser-welding equipment and thus the resulting welding seam size, which may be orders of magnitude larger than microfluidic channels and structures. We have successfully achieved extremely small welding seams using focussed low-power laser diodes. Commercial laser welding stations for polymer assembly will typically operate in the power-region 15–50 Watts. The focussed laser beam will have a size of typically 500 μm × 500 μm and may, depending on optical configuration, be up to several mm². The resulting welding-seam will thus be in the area of 300–600 μm depending on beam energy distribution; additionally the melt will spread to unheated areas due to capillary forces. As microfluidic channels are in 20–100 μm regions, even a very limited amount of stray melt may completely fill a part of a channel and thus render it useless. We have used commercially available “single-die” laser-diodes of optical power 200–500 mW. The beam has been focussed and directed using simple optical installations, resulting in a beam-size in the area of 50 μm × 5 μm full width half maximum (FWHM) We have achieved firm welding seams of width <10 μm, with a welding speed of 15 mm/s and with virtually no noticeable spread of melt.     

双光子三维微结构快速制备技术

建立了一种利用双光子聚合技术快速制备三维微结构的方法,并对加工分辨率进行了研究。通过对高速扫描原理的研究,提出了采用二维振镜与一维压电微移动台相结合,利用跳跃和扫描协同的运动模式,以段段扫描方式进行三维微结构加工的系统来提高其加工速度。实验制备千里马和具有木堆结构的三维光子晶体结构说明,采用上述扫描方式可使其加工速度较点点扫描方式提高10倍至1 000倍。实验结果表明,使用一定的激光功率时,其加工分辨率随曝光时间减小而显著提高,实验得到了50 nm的线宽分辨率,超过文献报道的100 nm的最高值。研究还表明,上述加工方法可实现激光三维微结构的快速制备并具有高分辨率加工的特点。     

激光外差探测对振动目标多普勒频谱成像

提出了采用激光外差技术探测振动目标,获取目标多普勒频谱图像,实现目标轮廓识别的方法。基于相位变化给出了目标振动形成外差信号的光电流模型;用扫描振镜控制激光光束方向实现对目标点扫描;通过振镜驱动电压触发数据采集卡,实现扫描与采集同步。利用频谱展宽占有比例的信号处理方式处理振动目标形成的多普勒频谱,简化了数据处理方式,有效消除了单个峰值噪声对信号的影响。实验中以5 MHz采样率测得两个目标在不同位置的特征频谱,得到了它的频谱展宽占有比例曲线;选取不同频谱展宽占有比例形成多普勒频谱图像,指出频谱展宽占有比例在0.7到0.9时能够形成良好的振动图像。文中结果证实了利用频谱展宽占有比例的数据处理方式探测振动目标是有效的,利用外差技术获取振动频谱图像是可行的。     

Validation of a single fibre-fed heterodyne laser interferometer with nanometre uncertainty

In this paper the validation of a fiber-fed heterodyne laser interferometer with nanometre uncertainty is presented. The achievable displacement measurement uncertainty is investigated for different polarisation maintaining fibres used in these interferometers. Measurement results are shown for both a range of m as well as a range of 300 mm. It is shown that a (selected) PM-fibre with an extinction ratio of 1:1650 and the use of an external reference allows realising a fibre-fed laser interferometer able to measure displacements with the same uncertainty as a laser interferometer system without fibre. Tests were performed with fibres ranging in length up to 50 m.     

激光诱导空化微孔冲裁试验研究

针对微尺度下金属箔模具冲孔存在模具挤压磨损、对中困难,激光打孔存在烧蚀、吸收层无法补偿等问题,提出通过激光诱导空泡对金属箔进行加载来实现冲裁小孔的方法。研究了不同激光焦点位置(H=0~4 mm)、激光能量(E=10.3~50.8 mJ)和铜箔厚度(T=20~70μm)对铜箔冲孔的影响,发现激光焦点位置影响明显,当铜箔变形平均深度达到147.0μm后,铜箔发生剪切断裂,可实现冲裁,并且制备的小孔边缘正表面无烧蚀、毛边、裂纹和卷边等缺陷。同时,利用高速摄影仪对激光诱导空化微孔冲裁过程进行研究,结果表明激光诱导空化微孔冲裁过程是激光等离子体冲击波、空泡溃灭冲击波和微射流共同加载的过程。     

基于飞秒激光的可运动微结构加工与旋转驱动

微驱动技术由于驱动方式的多样性和应用的广泛性,在近年来受到了越来越多的关注。本文提出一种利用飞秒激光同时实现微结构加工和旋转驱动的技术。利用双光子聚合加工直径20~30μm的微转子结构,然后结合空间光调制器调制出带有光学轨道角动量的光场,实现对微转子结构的旋转驱动,并获得了40 r/s的转动速率。详细介绍了利用飞秒激光直写技术加工可运动微转子结构的实验过程与优化参数,利用空间光调制器生成了不同拓扑荷的涡旋光,研究了其传播与聚焦特性,并用于驱动转子的顺、逆时针旋转运动。这种可控光学驱动技术在微流控、光镊技术、靶向药物运输、细胞动态行为等领域具有广阔的应用前景。     

Interfacial interactions of perfluoropolyether lubricants with magnetic recording media

Perfluoropolyethers (PFPE) are low surface tension liquids that are commonly employed in magnetic recording devices (hard-disk drives)as disk lubricants. In current drives, a single monolayer (or less) of a PFPE is applied to the amorphous carbon overcoat of the hard disk to provide the necessary lubrication of the head-disk-interface. The focus of the current paper is to demonstrate the utility of surface energy measurements in extracting information on the PFPE lubricant-carbon interfacial interactions. In particular, surface energies are reported as a function of applied lubricant thickness in the range of 2--30 Å for three Fomblin Zlubricants, i.e., ZDOL, ZDIAC, Z-15; and two Demnum lubricants,i.e. Demnum SA and SP. We show that from the surface energy measurements one can: (a) determine the extent of lubricant coverage of the carbon surface, (b) determine the orientation of the lubricant with respect to the carbon surface, (c) determine the nature of the lubricant-carbon interaction, e.g. attractivevs. repulsive, and (d) obtain an estimate of the interaction strength between the lubricant and the carbon.     

激光切割中的焦点位置检测方法研究

激光焦点位置检测与跟踪技术是激光加工的关键技术之一、本文讨论了激光切割 加工系统中焦点位置误差的产生和常用的两种检测系统的组成原理及其使用中的优缺点,分析了切割过程中等离子云对电容传感器的干扰机理,进而提出了两种有效的解决方法。     

激光熔覆合金表面耐磨性试验研究

使用CO2激光器对45#钢表面进行Co基和Ni基合金熔覆处理。利用销盘式摩擦试验机对激光熔覆表面进行摩擦磨损试验,研究干摩擦和润滑条件下磨损机理。Ni合金熔覆层比Co基耐磨性要好。润滑条件下,两种合金的耐磨性比干摩擦都得到很大提高。     

Methods for detecting structural changes in frames of video sequences when recording physical and chemical experiments

The possibility of applying the mean structural similarity, mean nonparametric structural similarity, and spectral criteria to detection of structural changes in the phase condition of an object of investigation is considered. Determination of cesium chloride phase transitions in the temperature range of 250–710°C is used as an example to demonstrate the experimental evidence of the efficiency of these criteria for solving the above-mentioned problems.     

PIC单片机在汽车燃油油量检测中的应用

介绍了一种数字式车用仪表．它以PIC单片机为核心，可以对车辆的油箱油量，运行里程、瞬时油耗和平均油耗进行实时监测和显示。该仪表充分利用了PIC16F874自身的软硬件资源，具有精度高，升级方便等特点。     

Experimental study of directional characteristics of a pulsed laser thermoacoustic radiator

Results of experimental research on revealing the dependence of directional characteristics of a pulsed laser thermoacoustic radiator of body ultrasonic waves on the radiator’s energy and geometry parameters are provided. Experimental bench and measurement procedure are described. The results can be used in developing tools for noncontact ultrasonic inspection of metal materials and products.     

矫直辊表面激光强化实验研究

采用不同激光工艺参数对9SiCr钢矫直辊表面进行强化处理,探讨各加工参数对硬化层深度和硬度的影响。