Impact of molecular weight of polymers and shear rate effects for nanoimprint lithography

Linear polystyrene of different weight averaged molecular weight (M_w = 58 kg/mol and 353 kg/mol) and a narrow molecular weight distribution was imprinted to point out differences in the flow behaviour caused by the polymer’s molecular weight in a typical hot embossing/thermal nanoimprint process. Residual layer thickness and uniformity as well as defects were taken as a measure to qualify the imprint process. Since polymer viscosity is addressed as the main material parameter, a full thermo-mechanical characterisation of the two polymers via parallel plate dynamic viscosimetry was performed prior to imprint. The main process parameter responsible for viscosity, the temperature, was varied from about 30 to 150 K above the glass transition. In addition the amount of polymer supplied for the process was varied, i.e. the initial spin-coated polymer layer thickness. Situations representing ‘underfilling’, ‘filling’ and ‘overfilling’ of the stamp cavities in specific regions were investigated. Squeezed flow simulations were performed taking into account the increase of pattern size and the filling of cavities during the ongoing imprint, which have substantial impact on the residual layers obtained. The results show that shear thinning is an issue in a high pressure hot embossing system. It governs the initial phase of the imprint featuring a rapid decrease of the polymer height. From theoretical considerations, a model could be derived for the imprint procedure under shear thinning in a constant pressure system which was able to interpret the observed phenomena. Despite the macroscopic nature of the thermo-mechanical analysis, the standard viscosimetric data for the polymers appeared to be sufficient to understand the experimental results.     

红外探测器光谱响应度的均匀性及直线性测试研究

红外探测器光谱响应度的均匀性及直线性一直被认为是评价红外探测器性能的关键技术指标。目前，国防科工委光学计量一级站正在进行红外光谱响应度及其均匀性和直线性的测试研究，也包括对大气窗口一系列特性的测试研究。同时，还评价了一系列商用红外探测器，期望得到性能良好的、可用于不同波段量值传递的红外标准探测器。本文着重介绍红外探测器光谱响应度的均匀性及直线性的测试方法及测试结果，并评价一系列用于量值传递的不同波段的红外探测器。     

LED背光源亮度均匀性的研究

讨论LED的偏置电阻和发光亮度对LED背光源亮度均匀性的影响。     

Uniformity pattern and related criteria for two-level factorials

In this paper,the study of projection properties of two-level factorials in view ofgeometry is reported.The concept of uniformity pattern is defined.Based on this new con-cept,criteria of uniformity resolution and minimum projection uniformity are proposed forcomparing two-level factorials.Relationship between minimum projection uniformity andother criteria such as minimum aberration,generalized minimum aberration and orthogo-nality is made explict.This close relationship raises the hope of improving the connectionbetween uniform design theory and factorial design theory.Our results provide a justifi-cation of orthogonality,minimum aberration,and generalized minimum aberration from anatural geometrical interpretation.     

BEPCⅡ冲击磁铁的设计和样机研制

由于BEPCⅡ储存环注入系统对冲击磁铁的设计要求比较高，国际上现有的两种低束流阻抗的冲击磁铁方案都不能完全满足其要求. 本文提出的一种新型冲击磁铁方案解决了BEPCⅡ冲击磁铁的设计难题，并且通过样机的成功研制，证明了这种方案对于BEPCⅡ来说是可行的，结构和工艺设计是合理的.     

一种新型冲击磁铁的理论分析和模拟计算

在国际上已有的冲击磁铁方案不能完全满足BEPCⅡ储存环注入系统对冲击磁铁宽均匀场区、高均匀度和低束流阻抗的设计要求的情况下,提出了一种新型冲击磁铁的设计思想.理论分析和瞬态OPERA程序模拟计算的结果表明,在Δx=±20mm的范围内,中心平面上场的均匀性为±0.6%,y=5mm的平面上场的均匀性为±0.7%,y=10mm的平面上场的均匀性为±2.9%,均优于BEPCⅡ储存环注入对冲击磁铁的设计要求.MAFIA程序模拟计算的束流阻抗Z/n(eff)小于0.022Ω,小于设计要求的0.025Ω.     

激光空间相干性对照明均匀性的影响

 研究了激光相干性对照明均匀性的影响，为照明激光器的选择提供了理论参考。其中，部分相干高斯光束分解为模式间相互独立的厄米-高斯光束的迭加。采用相位屏的近似处理方法对激光通过大气湍流的传输进行计算模拟。数值模拟的结果表明：当照明光束的空间相干性降低时，其照明均匀度逐步提高。因此对于照明激光器而言，选择空间相干性较差的激光器对其照明均匀度更加有益。     

Isotopically pure uniform polymers: The final step toward true uniformity in macromolecules

Computer‐based calculations were used to simulate the mass spectra for a number of uniform macromolecules having fixed, well‐defined chain lengths. The presence of naturally occurring carbon, hydrogen, oxygen, and halogen isotopes introduced significant levels of mass heterogeneity into these systems. For a given polymer, mass variability was demonstrated to be a function of both the elemental composition and degree of polymerization of the polymer chain. In many cases, these natural variations in mass exceeded the molecular weight of one or more monomeric repeat units along the polymer backbone, effectively blurring the mass distinction between uniform polymer constructs formed from N and N+1 repeat units. The significance of isotopic diversity and its potential impact on the synthesis and physiochemical properties of highly uniform macromolecules is also discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 923–935, 2002     

光学膜层激光损伤阈值均匀性的实验研究

 镀制了多种氧化物介质薄膜。用R-on-1方法测定了膜层的激光损伤阈值。引入数据处理方法，对测试数据进行分析。结果表明，基片清洗后，若放置一段时间再镀膜，则会影响到镀膜后膜层损伤阈值的均匀性，但对损伤阈值自身大小没有影响。测试激光参数对阈值均匀性也有一定影响。     

国产家庭轿车选型优化

利用数学中的层次分析法,对人们关心的家用轿车的选购问题,进行选型优化,选择出了最优的方案,即选择出最优、最适合大家购买的车型.