水凝胶支架的飞秒激光全息加工

为了实现以水凝胶为材料的细胞支架快速加工,将计算全息法引入传统的飞秒激光双光子加工中,并对全息图的生成方法和全息图对加工结构的影响进行了研究。首先,根据贝塞尔光波动方程和其透射函数生成贝塞尔光束全息图,分析两种参数对环形结构大小和质量的影响。然后利用生成的全息图加工得到壁厚800nm、直径为8~15μm不等的水凝胶(PEGDA)圆管结构。最后,实现了基于圆管道的水凝胶细胞支架高效快速加工,支架中圆管道壁厚800nm、直径为8μm。本文首次将飞秒激光全息加工技术应用于水凝胶三维支架加工,解决了飞秒激光单点加工效率的问题。该技术在生物医学中具有广阔的应用前景。     

双光子三维微细加工技术及实验系统的开发

介绍了一种新型的三维微细加工技术,描述了自行开发的双光子微细加工实验系统.双光子三维微细加工技术利用材料与飞秒激光束在焦点局域发生的双光子激发,通过逐点扫描,实现微器件的三维成型.由于材料发生双光子激发的几率与激发光强的平方成正比,所以具有极高瞬时光强的飞秒激光器和可以对光束进行强聚焦的显微镜装置成为系统的关键部件,对此进行了详细的说明.最后,给出了部分利用上述加工系统所获得的初步实验结果.     

飞秒激光多次聚焦在并行加工中的应用研究

飞秒激光的并行加工多是利用分光元件先分光再加工,在实际应用中,这种方法无法对加工出的平行结果进行灵活的控制。本文通过控制飞秒激光在介质中的多次聚焦,实现微光波导的并行加工,总结出影响加工的控制因素,并且对这种加工方法的机理和控制因素作了理论分析。由于不依赖分光元件,该方法对并行加工的控制相对灵活。对于飞秒激光的并行加工,该方法提出了一个值得发展的方向。     

基于原子力显微镜的PMMA飞秒激光纳米加工

介绍了一种基于原子力显微镜(AFM)的激光近场增强纳米加工方法。探讨了作为主要影响因素的激光场增强效应,用时域有限差分法对AFM探针下光场的空间分布进行了数值分析。研究了飞秒激光入射到AFM探针的PMMA材料的图形化,在PMMA材料表面加工了不同宽度的线条和字母。利用AFM对所得纳米图形进行了原位测试。在激光参数未经优化的情况下,其线宽可达100 nm,超过了实验室飞秒激光远场加工的分辨能力(200 nm)。     

快速并行激光显微切割方法

针对传统激光显微切割采用单激光焦点与工件相对运动形成加工轨迹,存在切割效率低、切割轨迹首尾不易闭合等局限性,提出基于数字微镜器件的无机械运动激光显微切割方法。通过调控数字微镜阵列,对激光光束的振幅进行调控,配合光路设计在样品区域得到任意的光场强度分布,实现强度近乎相同的面投影并行切割。阐述了关键参数设计、模拟仿真、系统搭建过程。先对聚酯薄膜进行直线、空心圆环、空心矩形等多种图案的切割,再对冷冻切片的细胞组织进行切割。实验表明,通过一次投影并行切割可设计的图案化结构,目标图形准确,切割效率高。在20×物镜下,最小切割线宽达到亚微米,最小圆环直径小于单细胞直径。该方法可为提高激光显微切割系统的效率和精度提供新思路和新方向。     

飞秒激光正交线扫描诱导表面微纳结构

通过控制激光偏振与扫描方向,利用飞秒脉冲激光正交线扫描的微加工方式,在硅和不锈钢表面诱导出了规则分布的复合表面微纳结构并分析了激光能量密度对微纳表面结构形成的影响。实验显示:当激光的能量密度接近材料烧蚀阈值时,在硅表面诱导出了周期条纹嵌套纳米孔的双层复合二维结构,在不锈钢表面则诱导出了依赖于激光偏振方向的纳米点阵列分布,分析认为纳米点阵列是由周期条纹结构边缘发生断裂而生成的。另外,当激光的能量密度大于材料烧蚀阈值时,在硅和不锈钢表面会烧蚀出规则分布的微米级孔洞结构。实验结果表明:第一次扫描诱导出的表面微纳结构增加了对入射激光的吸收,促进入射激光与表面等离子体波的耦合,加强了后扫描的烧蚀效果,使得后扫描诱导出的微纳结构占主导。文中提出的正交线扫描的加工方式为微纳表面结构的制备提供了新的思路。     

基于飞秒激光双光子的微齿轮加工技术研究

针对传统加工方法很难实现微机电系统(Micro electromechanical systems,MEMS)零部件高质量加工的问题,在微细加工技术研究基础上,提出采用飞秒激光双光子聚合加工技术加工标准渐开线微齿轮的方法.采用钛蓝宝石激光器自行搭建的飞秒激光双光子加工系统,能够输出波长为800 nm的飞秒激光用于双光子聚合加工,利用AutoCAD软件设计标准渐开线微齿轮,通过理论和试验两种方法研究激光功率与单个固化点尺寸之间的关系,进而研究扫描步距与加工精度和表面粗糙度之间的关系,结果表明,激光功率越小,加工分辨率越高;扫描步距越小,加工变形越大,但表面质量提高.采用优化后的加工工艺参数加工出高质量的标准渐开线微齿轮,其表面粗糙度Ra27.66 nm.因此,飞秒激光双光子加工技术能够为微齿轮或其他MEMS零部件的加工提供一条有效途径.     

数字全息位相拼接实验研究

数字全息拼接技术旨在实现较大物体的检测或在同样的测量面积下获得更高的空间分辨力,实现方法是采集被测物体多个子孔径的数字全息图,且保持相邻子孔径之间有一定的重叠区。分别精密再现各个子孔径的数字全息图,然后将各孔径的位相信息进行拼接,以获得全孔径的位相分布。分别处理了反射型分辨力板(子孔径数为2×4)和透射性微透镜阵列(子孔径数为4×4)两个样本的全息图,并给出了消除测量光束和参考光束非等光程所引入的误差的方法。     

雷达功率组件的金刚石微通道热沉激光加工工艺

为研究雷达功率组件金刚石微通道热沉的加工难题,开展了飞秒激光加工多晶金刚石微流道的工艺研究,仿真模拟了飞秒激光作用于金刚石表面的温度场分布,以及诱导去除过程,理论与实验研究了金刚石的烧蚀阈值,系统研究了激光能量、扫描速度、扫描次数、焦点位置等参量及其优化工艺参数对金刚石微槽尺寸的影响规律。结果表明:当飞秒激光功率大于0.3 W时,激光作用于金刚石的最高温度超过材料去除的气化温度,温度最高位置处于光斑中心,功率不会改变温度场的分布情形;飞秒激光加工金刚石的烧蚀阈值为1.80 J/cm2,金刚石微槽深度与激光功率、扫描次数正相关,与扫描速度负相关,与正负离焦量基本成对称分布关系,而金刚石微槽表面宽度则变化不明显;在激光功率为5 W,扫描速度为100 mm/s,扫描次数为30,离焦量为-0.5 mm的优化参数下,加工出的金刚石微槽结构形状规则,截面侧壁锥度控制在3°以内,表面无残渣、裂纹、崩边等缺陷,且内部也无裂纹等缺陷,加工一致性较高,实现了微通道的 “冷”加工,可满足雷达功率组件金刚石热沉对微通道的高质量加工要求。     

飞秒激光加工及其应用

综述了激光短脉冲化的飞秒激光发展史,重点论述了飞秒激光的加工机理和特点.飞秒激光独特的光束特性决定了他是一种理想的微细加工工具,可以实现聚合物的制备,可以对各种透明材料内部进行三维加工和改性,另外在生物学领域也有着独特的应用.本文最后还展望了飞秒激光加工未来的发展方向.     

飞行时间质谱仪射频四极杆驱动器的研制

针对自制垂直引入式飞行时间质谱仪（orthogonal extraction time-of-flight mass spectrometer, O-TOFMS）的需要,运用直接数字频率合成 (direct digital frequency synthesis,DDS)技术,研制了射频四极杆的高压射频驱动电路装置。该驱动器频率可调范围为0.5~2 MHz,幅度最高达到1 000 Vp-p。该射频四极杆驱动器（radio frequency quadrupole driver,RFQ Driver）可用于分子离子反应器（molecule ion reactor,MIR）和RFQ驱动,其结构简洁、成本低、性能稳定可靠。     

从光电容积图中提取脉搏率、呼吸率和心率的新方法

光电容积描记图(PPG)是一种利用光学技术无创检测人体心血管脉搏波的方法。PPG信号来源于MIMIC数据库,它含有许多生理信息。本文提出了将集合经验模态分解(EEMD)、倒谱、快速傅里叶变化和过零点检测相结合的方法,从PPG中可靠地估算脉搏率(PR)、心率(HR)和呼吸频率(RR)。首先,将PPG信号通过EEMD分解为有限个固有模态函数(IMF)。因为EEMD有自适应滤波特性,所以估算不同的生理参数时,可以用不同的IMF分量来重构信号。其次,估算脉搏率时,舍去低频含有伪迹的IMF,再通过过零点检测可以得到瞬时脉搏率。然后,估算心率时,用1 Hz~1.67 Hz(60次/分钟~100次/分钟)的IMF来重构信号,再求倒谱,选取反映心脏活动的频带来得到心率。最后,估算呼吸率时,用0.05 Hz~0.75 Hz(3次/分钟~45次/分钟)的IMF来重构信号,然后对呼吸信号求快速傅里叶变化得到频谱图,寻找频谱图中的峰值得到呼吸率。对来自MIMIC数据库的53个成人PPG信号进行了仿真。仿真结果表明使用该综合信号处理方法提取的生理参数与实际生理参数一致,且该方法有运算量小,精确度高的优点(误差不超过1.17%)。     

UPLC-MS/MS测定二苯甲烷二异氰酸酯

建立了二苯甲烷二异氰酸酯（MDI）的超高效液相色谱-串联质谱（UPLC-MS/MS）联用的分析方法。实验用甲醇作衍生试剂,将二苯甲烷二异氰酸酯衍生成二苯甲烷二氨基甲酸甲酯（MDC）,通过测定二苯甲烷二氨基甲酸甲酯来确定二苯甲烷二异氰酸酯的含量。实验采用Waters Acquity BEH C18超高效液相色谱柱,甲醇-0.1%甲酸作为梯度洗脱液,二苯甲烷二氨基甲酸甲酯在1.5 min内与其他化合物进行完全分离,经四极杆质谱选择离子监测模式检测。线性范围为2~100 μg/L,检出限为1 μg/L,相关系数0.999 4。考察了水、甲酸、甲酸铵流动相体系,以及进样量大小对样品的分离效果,发现甲酸流动相体系的分离效果优于其他两种流动相体系,同时发现在进样量大时出现平头峰。并且在优化条件下,对实际样品中游离的二苯甲烷二异氰酸酯进行了测定。     

Rapid one-of-a-kind production

To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study, the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy, which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this paper. This system consists of a number of inter/intranet based computer models or sub-systems for supporting rapid development of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental product development strategy” and an integrated product data structure called “product production structure”. Some industrial implementations of the proposed system, product development strategy and product data structure are also reported in the paper.     

汽车ESC系统DIL/HIL仿真平台设计

全面准确地标定与测试是开发车辆电子稳定控制(electronic stability control,ESC)系统的关键环节。车辆控制过程是典型的强非线性系统,建立精确的车辆模型比较困难,驾驶员模型也很难准确模拟紧急工况下驾驶员的真实反应。在仿真系统中将难以精确建模的液压制动系统、ESC压力调节单元、转向及电子节气门装置采用真实硬件,并在试验平台中嵌入真实驾驶员,基于Matlab/Simulink/dSPACE环境和车辆动力学软件veDYNA,开发硬件在环(hardware-in-the-loop,HIL)和驾驶员在环(driver-in-the-loop,DIL)的仿真试验平台,并在此平台上对所设计的ESC系统进行仿真试验研究。试验结果表明,所设计的DIL/HIL仿真平台可以大幅提高ESC系统的开发效率和测试准确性。     

Effect of the molecular weight on deformation states of the polystyrene film by AFM single scanning

Nanobundles patterns can be formed on the surface of most thermoplastic polymers when the atomic force microscope (AFM)‐based nanomechanical machining method is employed to scratch their surfaces. Such patterns are reviewed as three‐dimensional sine‐wave structures. In the present study, the single‐line scratch test is used firstly to study different removal states of the polystyrene (PS) polymer with different molecular weights (MWs). Effects of the scratching direction and the scratching velocity on deformation of the PS film and the state of the removed materials are also investigated. Single‐wear box test is then employed to study the possibility of forming bundle structures on PS films with different MWs. The experimental results show that the state between the tip and the sample plays a key role in the nano machining process. If the contact radius between the AFM tip and the polymer surface is larger than the chain end‐to‐end distance, it is designated as the “cutting” state that means the area of both side ridges is less than the area of the groove and materials are removed. If the contact radius is less than the chain end‐to‐end distance, it is designated as the “plowing” state that means the area of both side ridges is larger than the area of the groove and no materials are removed at all. For the perfect bundles formation on the PS film, the plowing state is ideal condition for the larger MW polymers because of the chains’ entanglement. SCANNING 35:308‐315, 2013. © 2012 Wiley Periodicals, Inc.     

Rapid one-of-a-kind production

To shorten the product development cycle time and reduce the cost at the same time, which is very critical for the survival of those small and mid-sized one-of-a-kind production (SMOKP) companies, various computer communication, simulation and computer aided engineering and management techniques have been widely used in these SMOKP companies. However, according to our study, the applications of these advanced computer technologies in these SMOKP companies are lack of system integration and synergy, which result in communication errors, reworks, duplications and hence a longer product development lead time and a higher cost. To solve this problem, an inter/intranet based computer aided rapid product development system is presented in this paper. This system consists of a number of inter/intranet based computer models or subsystems for supporting rapid development of a one-of-a-kind product. It also employs a novel concurrent product development strategy called “prototype based incremental product development strategy” and an integrated product data structure called “product production structure”. Some industrial implementations of the proposed system, product development strategy and product data structure are also reported in the paper.     

The efficacy of back propagation neural network with delta bar delta learning in predicting the wear of carbide inserts in face milling

Face milling is a process predominantly affected by dynamic variation of cutting forces, thermo-mechanical shocks and vibration leading to catastrophic tool failure along with gradual wear of the inserts. Keeping in view the industrial importance of this process, it is necessary to devise suitable methods to predict in advance the onset of tool failure without grossly impairing the machining set-up and the job. Hence, the applicability of back propagation neural network with delta bar delta learning rule for faster convergence has been studied with the above objective. The multi sensor based tool condition monitoring strategy shows that the learning rate adaptation scheme combined with the selection of suitable process parameters drastically reduces the training time of the artificial neural network without dispensing with the prediction accuracy.     

复合ICA-SVM机械状态模式分类

提出了一种新颖的、基于独立分量分析(ICA)的复合神经网络，用于不同机械状态模式的特征提取。利用支持向量机(SVM)进行最终分类。与通常的基于经验风险最小化(ERM)原理的神经网络方法相比，基于结构风险最小化(SRM)原理的支持向量机分类方法具有更好的推广能力。而借助多个独立分量分析网络，隐藏于多通道振动观测信号中的不变特征得到有效提取，从而实现了支持向量机分类器在分类能力和推广性两者间的合理平衡。     

同位素稀释质谱法测定贻贝中多氯联苯的国际比对研究(CCQM-P67)

A method developed to participate the pilot study of international comparison CCQM-P67 was introduced. Isotope dilution mass spectrometry (IDMS) was used in the detection of five PCB congeners in freeze-dried muscle tissue. Soxhlet Extraction is used for extraction of mussel, duplicate clean-up of GPS and SPE column were used, C-13 labeled PCB congeners were added as internal standard to avoid the error from sample preparation and diction. High resolution Mass spectrometer was used to give good result of detection.