薄膜反射镜静电成形单电极控制

静电拉伸薄膜反射镜是近年来发展起来的一种新型技术,薄膜反射镜具有质量轻、柔韧性好、可折叠等优点,在航天领域具有广阔的应用前景。静电拉伸薄膜反射镜的原理为利用静电场上库仑力作用使薄膜产生面形变化,生成所需的反射曲面。由于薄膜变形力学,以及静电场理论的复杂性,目前薄膜成形及其面形控制的研究工作都还不完善。本文在薄膜反射镜成形控制机理研究的基础上,设计了单电极式薄膜反射镜的控制试验,详细计算了控制成形所需的主要参数,设计了薄膜反射镜的夹持结构和控制电路,并利用刀口仪测量了形成的反射面的焦距,试验结果表明在10000V的高压下可以行程焦距约为2.1m的反射镜面,面形的PV值达到11.14λ, RMS值为1.86λ,通过改善夹持结构和选取性能优良的薄膜材料控制面形精度可进一步提高。     

薄膜反射镜静电成形机理研究

摘要：薄膜反射镜是一种正在发展中的新概念技术,它将解决反射镜孔径与重量相互制约的问题。采用静电拉伸法控制薄膜反射镜面形,具有结构简单、反射镜面形易于控制等优点,其原理为利用静电场上库仑力作用使薄膜产生面形变化,生成所需的光学曲面。由于薄膜变形力学,以及静电场理论的复杂性,目前薄膜成形及其面形控制在理论分析上仍未有定量的结果。本文主要从理论上分析了静电场中空间电势分布特性,以单电极静电场中的薄膜反射镜面形为考察因素,通过数值计算的方法得到薄膜反射镜上的静电力分布,运用有限元分析获得该分布下的反射镜面形,并将其与理想面形进行了比较。提出采用多电极闭环控制可获得更高的控制精度,对静电拉伸薄膜的研究工作具有重要的指导意义。     

薄膜反射镜的成形控制

针对望远镜发射系统承载空间与承载质量的限制与大口径、高分辨率反射镜使用需求之间的矛盾,开展了轻质柔性薄膜反射镜地基试验研究,实现了静电拉伸式薄膜反射镜的精确成形控制.针对口径为300 mm的同心环分布式电极静电拉伸聚酰亚胺镀铝薄膜反射镜,基于泊松方程的薄膜小变形近似求解.并通过确定每环电极对面形的影响函数来确定分布式电极对反射镜薄膜成形的控制矩阵,进而利用最小二乘法求得了分布式电极对面形精确控制所需的分布电压.用ANSYS有限元分析法对比结果,分析相关误差并总结控制方法.结果显示,在薄膜中心变形量超过2.5 mm以后,基于泊松方程的理论求解和ANSYS有限元分析结果相差很大,计算面形与理想面形偏差也很大;认为只有综合运用数值计算和有限元分析,通过确定分布式电极对面形的控制矩阵,运用最小二乘法求解分布式电压,才能准确地实现薄膜小变形面形的预知和控制.     

静电拉伸薄膜反射镜的多电极成形控制

针对现有薄膜反射镜成形控制方法存在求解复杂,工程实用性差等问题,提出了基于反演求解的半解析成形控制方法.首先,基于Karman方程和静电场理论推导了所要拉伸的抛物面面形与施加压强分布的关系及实验所需的离散电极环电压值;其次,利用有限元软件建模和分析,验证所推导的压强分布;最后,在口径为300 mm的三环电极的静电拉伸反射镜实验平台上进行了验证实验.实验显示,拉伸面形最大变形量与理论值基本吻合,面形误差与传统均匀压强下的相比有所减少,最好的实验结果得到的PV值和RMS值较均匀压强下的值分别减少了9.76％和15.38％.仿真及实验结果表明:所描述的方法可以控制面形并提高面形精度,与传统的成形控制方法相比较具有简单实用等优点.     

静电拉伸薄膜反射镜成形控制方法研究

摘要：目的：针对发射系统承载空间与承载重量的限制与大口径、高分辨率反射镜使用需求之间的矛盾,开展轻质柔性薄膜反射镜地基试验研究,实现静电拉伸式薄膜反射镜精确成形控制。方法: 首先,基于泊松方程的薄膜小变形近似求解,针对口径Φ300mm的三环分布式电极静电拉伸聚酰亚胺镀铝薄膜反射镜,通过确定每环电极对面形的影响函数来确定分布式电极对反射镜薄膜成形的控制距阵,进而利用最小二乘法求得分布式电极对面形精确控制所需的分布电压。并用ANSYS软件有限元分析进行结果对比,分析相关误差因素,总结控制方法。结果：在薄膜中心变形量大约超过2.5mm以后,基于泊松方程的理论求解和ANSY有限元分析结果相差很大,计算面形与理想面形偏差也很大。结论：只有综合运用数值计算、有限元分析方法,通过确定分布式电极对面形的控制矩阵,运用最小二乘法求解分布式电压,才能准确地实现薄膜面形的预知和控制。     

空间薄膜反射镜面形设计及优化

在分析聚酰亚胺薄膜反射镜面形成型理论的基础上,结合光学系统对反射镜面形的要求,用有限元法求解了薄膜反射镜在一定预应力存在的条件下,受均布载荷作用产生变形的数值解,通过数据拟和给出了反射镜面形,并计算了理论面形与计算面形的误差;以反射镜镜面不同区域施加的载荷为设计变量,薄膜的屈服强度为状态变量,理想面形与计算面形的误差为目标函数,用ANSYS软件对薄膜反射镜面形进行了优化;最后以Zernike多项式为接口对反射镜面形进行了波前拟合,给出了优化前后反射镜的像差,证明了通过对薄膜反射镜施加适当的力场可以得到面形精度很好的抛物线面形。结果表明:改变力场可以控制薄膜反射镜面形,并得到需要的面形,为实际设计、构建聚酰亚胺薄膜反射镜提供了理论基础、设计依据和方法。     

大口径空间反射镜大容差支撑结构设计与优化

针对传统反射镜无法消除加工及装配应力,长期使用后面形精度下降不能满足使用要求的问题,提出了一种高稳定性空间反射镜支撑结构的解决方案,进行了具有大容差特性的1.5m口径高精度空间反射镜工程化研究和创制。依据经验和理论,完成了初始反射镜组件构型,反射镜的材料选用RB-SiC,采用三角形背部半开口反射镜轻量化形式和背部三点膜片型柔性支撑结构。以装配误差0.01mm的9种工况下反射镜的面形RMS变化量最小为目标,利用isight软件对反射镜支撑结构的主要尺寸进行了优化设计。最终完成了轻量化率为82.1%,组件质量为170.23kg的反射镜的研制。试验结果表明:反射镜在1 g重力作用下,面形精度RMS优于0.016λ(λ=632.8nm);加入0.02mm强迫位移模拟装配误差,面形RMS仍然为0.016λ;在20℃±5℃温变环境下,面形RMS变化量在0.002λ范围内;组件一阶固有频率为101.3Hz。反射镜组件静态刚度、动态刚度、面形精度以及环境适应性满足空间工程应用要求。     

空间相机1 m口径反射镜组件结构设计

针对1 m口径空间相机反射镜的设计要求,提出了一种新的反射镜柔性支撑结构.以材料选择、径厚比、支撑点数量和位置、轻量化结构形式等为设计变量,以自重作用下反射镜面形精度rms值为目标函数,优化设计了一种背部开口、三角形轻量化孔、背部三点支撑的SiC空间反射镜结构,同时提出了一种反射镜柔性支撑结构.对反射镜在光轴水平状态下进行装调检测时影响反射镜面形精度的柔性支撑结构参数进行了灵敏度分析,找到了影响反射镜面形精度的结构参数.对反射镜组件动、静态特性和热特性进行了有限元分析,分析结果表明,光轴水平方向重力载荷作用下反射镜面形精度rms达到5.6nm,4℃均匀温升工况下反射镜面形rms为2.7 nm,反射镜组件一阶固有频率为192Hz.最后,进行了反射镜组件的动力学测试试验,测得反射镜组件一阶固有频率为197 Hz,最大响应应力为181MPa,验证了有限元分析的准确性.得到的结果显示该反射镜组件完全满足设计指标要求.     

基于筋板式基结构的大口径空间反射镜构型设计的拓扑优化方法

针对大口径空间光学反射镜对轻量化的需求,提出了基于筋板式基结构的大口径空间反射镜构型设计的拓扑优化方法.该方法利用基结构拓扑优化的思想,将反射镜初始设计域限定为筋板式的反射镜基结构,通过各筋板的有无描述结构构型的变化.首先,借鉴连续体结构拓扑优化的思想,以壳单元离散筋板结构,以加筋板各单元的相对密度为设计变量(通过相对密度取1或0,描述该单元所在区域的筋板是否存在),以光轴竖直工况下镜面面形误差为设计约束,镜体的质量最小为优化目标,建立了镜体结构构型设计的拓扑优化模型;然后,以拓扑优化所得构型为基础,提取并形成结构概念构型;最后,采用有限元法进行动静刚度分析与光学性能分析,并对结构进行修正,形成性能更好、满足要求的反射镜轻量化结构创新构型.文中的设计实例得到的反射镜镜面面形误差PV值小于λ/10,RMS值小于λ/40,第一阶自振频率大于1 000 Hz,轻量化率达到86.0％.得到的结果验证了本文方法的有效性.     

大口径轻质反射镜坯的制造

给出了制造大口径轻质反射镜坯的机械法减重技术及所制造的反射镜坯.在镜坯制造过程中通过计算机辅助设计搜索轻量化加工区域的形状、大小、深度,并对其进行分类标识;编辑TPH(toolpath)轨迹数据文件,编写CNC(comput ernumbercontrol)数控系统的零件加工程序,由数控系统在图形方式下控制实际加工.同时采用化学方法消除加工过程中产生的应力与微小裂纹.加工出的大口径轻质反射镜坯达到设计要求,轻量化率达到65%以上,加工后的非球面面形精度达到0.029λ(rms,λ=633nm).制造过程中在不同支撑状态下,变形量很小,保持了非球面面形精度稳定性,显示出了结构的稳定性.该方法已经成为大口径反射镜制造的关键支撑技术.     

基于无矩理论的凹版印刷机运动薄膜横向振动特性及稳定性

研究了运动薄膜横向振动特性及其稳定性,以无矩理论为基础,建立了多色组印刷情况下具有中间刚性支承运动薄膜的横向振动模型。根据D'Alembert原理,建立了振动系统的运动微分方程。数值分析了薄膜的振动频率与运动速度、张力、支承位置之间的关系,结果表明中间单刚性支承薄膜振动发散失稳的临界速度为35.855 m/s。对于具有中间两刚性支承的印刷运动薄膜,薄膜轴向运动速度越低,支撑位置的变化对薄膜振动频率影响越明显。     

预张力膜片风振反应的试验研究

针对张拉膜片在确定的预应力水平下的风振反应来考察它的模态和风振特性．采用膜面预应力检测仪测量了试验中膜片的预应力水平。膜结构的振动形式经常是以高阶振型为主．基频随预应力水平的增大而增大。预应力水平越高，各阶模态对应的阻尼比相差越小；反之，气动阻尼越集中在低阶模态。与风速和预应力水平相比．膜面倾角对膜面位移风振系数的影响更为显著．并对不同倾角的膜面位移风振系数提出了建议值。部分工况下膜片出现颤振。膜面倾角和较低的预应力水平是诱发颤振的主要因素。     

反渗透膜表面Zeta电位研究

本文研究电解质溶液的种类、浓度及pH等因素对反渗透膜表面Zeta电位的影响.为膜表面Zeta电位的准确测定提供依据,并通过研究不同电解质溶液对膜面Zeta电位的影响,得到电解质溶液对膜表面Zeta电位的基本作用规律,以指导用于各种污水体系的膜的污染情况和使用寿命,为不同污水体系膜的选择和使用提供借鉴和指导作用。在此基础上,又研究污染膜和清洗后膜表面的Zeta电位和接触角,定性表征污染膜表面的污染程度及各种方法的清洗效果。     

Elastic force of red blood cell membrane during tank-treading motion: Consideration of the membrane's natural state

The elastic force of a red blood cell (RBC) membrane during its tank-treading motion was estimated using a three-dimensional spring network model. An RBC membrane was modelled by an assembly of triangular elements in which stretch/compression and bending springs were placed to express planar shear and out-of-plane bending deformations, respectively. An areal incompressibility of the membrane and a volumetric constraint on the entire RBC were taken into account. Different natural states of an RBC membrane were considered by adjusting reference lengths and angles of the stretch/compression and bending springs, respectively. An elastic motion simulation was conducted using the spring network model to reproduce a tank-treading motion of the membrane for a constant biconcave discoid RBC under a fluid shear force. Given the simulated tank-treading motion, an additional membrane elastic force due to the motion was determined from the elastic energy changes during the motion. It was confirmed that the natural state of the RBC membrane should be nonuniform to generate the additional elastic force. Greater spring constants and greater natural state nonuniformity induced a greater additional elastic force, and the elastic force was regarded as a resistance against the tank-treading motion. Additional elastic forces due to the membrane tank-treading motion for different sets of spring constants and natural state nonuniformity values were determined, and they were compared with fluid shear forces at shear rates within the range of which a transition between tank-treading and tumbling motions of an RBC occurs in experiments. The results suggested that for the experimentally measured elastic moduli, natural state nonuniformity in a physiological state is moderate between that for a spherical or flat shape and that for the biconcave shape. Moderate nonuniformity was also confirmed by a simulated RBC shape in a minimum state of elastic energy.     

New methods of track membrane treatment in the preparation of samples for further observation with scanning electron microscopy

Track membranes are porous systems consisting of a polymer foil with thin channels (i.e. pores) piercing it from surface to surface. The creation of non‐cylindrical pores in a track membrane is important for the optimization of membrane characteristics, i.e. the highest productivity at the required selectivity. A new method of cleavage preparation (the irradiation of track membrane samples with accelerated electrons) for the observation of channel shapes directly in the membrane cross‐sections is presented. Diagrams showing the tensile and burst strengths as a function of the irradiation dose, and images of surfaces and cleavages of track membrane samples are presented in this work. The changes in the pore sizes and shapes along the channel were clearly seen. These results can be used for the optimization of track membrane production.     

用于太空望远镜的大口径薄膜菲涅尔衍射元件

为了满足空间衍射成像系统对大口径、轻量化衍射元件的需求,设计制作了直径为400mm的聚酰亚胺(PI)薄膜菲涅尔衍射元件。通过紫外光刻、离子束刻蚀等微细加工方法在石英基底上制作衍射图形,然后将衍射图形复制到PI薄膜上得到菲涅尔衍射型薄膜元件。结合有限元法探究了薄膜复制过程中热应力的变化规律及降低热应力的方法,分析了影响薄膜衍射效率的因素及薄膜制作误差、温度变化对薄膜成像的影响,最终实现了大面积薄膜与基底的分离,并通过局部氧气等离子体轰击提高了薄膜衍射效率的均匀性。经测试,薄膜菲涅尔衍射元件的厚度约为20μm,在波长633nm处的实际衍射效率平均值为33.14%,达到了理论效率的81.83%,衍射效率的均方根值RMS=0.01。实验结果表明,通过紫外光刻、离子束刻蚀和薄膜复制的方法可以得到大口径、高衍射效率的薄膜菲涅尔衍射元件。     

Fabrication of key components of a receptor-based biosensor

A three-pronged approach was taken to the development of receptor-based bisensors. First, asymmetric bilayer membranes were developed with one monolayer adaptable to the particular receptor of interest and the other monolayer polymerized to enhance membrane stability. Second, alamethicin and calcium channel complexes were introduced into the stabilized membrane and tested for ion-channel function. Third, a porous support for the receptor-containing membrane was fabricated, which is compatible with silicon technology. Preliminary devices incorporating these components were constructed.     

Dimensions of active cytochrome c oxidase in reconstituted liposomes using a gold ball shadow width standard: a freeze-etch electron microscopy study

The preparation and characterization of a distribution of gold balls on a thin, flat carbon film is described. The relation of the platinum carbon shadow width distribution means to a gold ball size is reported. Freeze-etched cytochrome oxidase vesicles and gold ball calibration grids were simultaneously shadowed with platinum/carbon. The shadow width distribution of the cytochrome oxidase located in and spanning the membrane was measured. The membrane fracture face edge and cross-fractured bilayer membrane edge were also measured. Dimensions of the cytochrome oxidase were found to be 5·8 ± 0·3 nm in diameter parallel to the membrane and 8·2 ± 0·3 nm long across the membrane. The bilayer membrane dimensions were 3·0 ± 0·3 nm for the half bilayer and 5·8 ± 0·3 nm for the cross-fractured bilayer membrane edge thickness. The length of the cytochrome oxidase was observed to span the bilayer membrane. Previous X-ray diffraction measurements on similar hydrated liquid crystalline artificial membranes were found to be in good agreement with the freeze-etched results. Membrane widths from thin-sectioned cytochrome oxidase vesicles were measured and found to be 5·8–5·9 nm in non-post-stained sections. Post-staining with uranyl acetate and/or lead citrate was shown to increase this average thickness. The technique of freeze-etching electron microscopy in conjunction with the gold ball shadow width calibration experiment has been shown to provide accurate and precise measurements of membranes and a functional intramembrane protein in a hydrated non-crystalline sample.     

Morphological studies on the translocation of tubulovesicular system toward the intracellular canaliculus during stimulation of the gastric parietal cell

The gastric parietal has two characteristic membrane systems. One is the intracellular canaliculus, which is specialized networks of enfolded luminal membrane channels lined with numerous microvilli. The other structures common to all parietal cells are the tubulovesicles or the tubulovesicular membranes, a system of tubules and vesicles. The tubulovesicular compartment is drastically depleted during maximal gastric acid secretion and this is coincident with an increase in the canalicular cell surface membrane. A plausible explanation for this redistribution is the fusion and transfer of tubulovesicular membranes to the plasma membrane. However, for many years there was no convincing evidence of connections between these two membrane systems. The mechanism of the transformation of tubulovesicular membrane into the plasma membrane without demonstrable connections has been an enigma to electron microscopists. Using a recently developed fixation technique for parietal cells [Sugai et al. (1995) Acta Anat Nippon 74:S101], we have investigated the organization of the cytoplasmic membrane systems in the rat resting and tetragastrin stimulated stomachs by ultra-high-resolution scanning electron microscopy (SEM). Gastric mucosae were microwave-fixed in a cacodylate buffer, (334 milliosmoles/kgH(2)O (mOsm)), to which 1.0% glutaraldehyde and 0.5% formaldehyde were added. Specimens examined by TEM of thin sections revealed the cytoplasm packed with tubular membranes similar to images detected by rapid-freeze/freeze-substitution fixation. To render the cytoplasmic membranes visible by SEM, fixed mucosae were treated by the aldehyde-osmium-DMSO-osmium maceration procedure. With much of the cell matrix and filaments removed, SEM revealed numerous 30-60-nm tubules, which formed a meshwork with small cisternae. Vesicles or isolated tubules were not found in adequately macerated parietal cells. The cytoplasmic surface of the intracellular canaliculus was smooth except for round openings representing the bases of macerated microvilli. In favorable sites, connections of the tubular membranes to the canaliculi were clearly visible. Stereo pair views were particularly useful to demonstrate these continuities. Connections between these two membrane compartments suggest the probability of rapid membrane transposition. In this article, the form and distribution of membrane systems of parietal cells in the resting state and after tetragastrin stimulation will be presented and discussed. Special emphasis is made to demonstrate connections between the tubulovesicular system and the intracellular canaliculus.     

Cytoskeletal architecture of neuromuscular junction: Localization of vinculin

Cytoskeletons underneath the postsynaptic membrane of neuromuscular junctions were studied by using a quick-freeze deep-etched method and immunoelectron microscopy of ultrathin frozen sections. In a quick-freeze deep-etched replica of fresh, unfixed muscles, 8.9 ± 1.5-nm particles were present on the true postsynaptic membrane surface. Underneath this receptor-rich postsynaptic membrane, networks of fine filaments were observed. These cytoskeletal networks were more clearly observed in extracted samples. In these samples, diameters of the filaments which formed networks were measured. In the platinum replica, three kinds of filament were recognized—12 nm, 9 nm, and 7 nm in diameter. The 12-nm filament seemed to correspond to the intermediate filament. The other two filaments formed meshworks between intermediate filaments and plasma membrane. In ultrathin frozen sections vinculin label was localized just beneath the plasma membrane. Thirty-six percent of the label was within 18 nm from the cytoplasmic side of the plasma membrane and 50% was within 30 nm. Taking the size of the vinculin molecule into account, it was concluded that vinculin is localized just beneath the plasma membrane and might play some role in anchoring filaments which formed meshworks underneath the plasma membrane.