光静态散射测试系统的研究与实现

随着科学技术的发展,对粒子的大小、浓度及其他特性的探测已经发展成为一个专门的研究领域和现代测量学中的一个重要分支,而光散射法已经成为一种常用的粒子测量方法。为了满足应用需求,文中提出了一种基于C8051F500单片机的光静态散射测试系统方案,详细介绍了该测试系统的设计理论原理、硬件电路的设计依据、固件程序的设计思想和测试系统的具体实现。选取一定浓度的样品溶液,运用该系统进行光散射的角度依赖性测试,实际测量值与理论依据基本相符;在不同激光功率下,对同一角度的散射光强进行测试,将测量得到的数据分析,线性度良好,满足设计要求。     

红外成像系统NETD参数测试算法及应用研究

噪声等效温差(NETD)是表征红外成像系统灵敏度的关键参数,也是评估红外成像系统性能的重要参数之一,应用广泛。通过对红外成像系统3D噪声、信号传递函数(SiTF)、NETD等参数测试方法、算法和流程研究,给出一种基于视频文件的3D噪声离线对比测试方法和一种SiTF线性区自动判断计算斜率算法,在此基础上针对某型技术保障装备国产化光电检测平台开发了配套应用软件功能模块。实现了通过计算单位均方根噪声所对应的SiTF斜率值,分析得出系统NETD参数值的功能。以某型热像仪为被测对象,开展了测试结果重复性和一致性试验,并与美国Optikos公司I-SITE红外整机测试系统进行了对比测试。实验结果表明开发的NETD参数测试功能模块测试精度和重复性满足设计要求,具有较高实用价值,已进行了工程应用。     

Metric inequalities for routings on direct connections with application to line planning

We consider multi-commodity flow problems in which capacities are installed on paths. In this setting, it is often important to distinguish between flows on direct connection routes, using single paths, and flows that include path switching. We derive a feasibility condition for path capacities supporting such direct connection flows similar to the well-known feasibility condition for arc capacities in ordinary multi-commodity flows. The condition can be expressed in terms of a class of metric inequalities for routings on direct connections. We illustrate the concept on the example of the line planning problem in public transport and present an application to large-scale real-world problems.     

CORSICA: correction of structured noise in fMRI by automatic identification of ICA components

When applied to functional magnetic resonance imaging (fMRI) data, spatial independent component analysis (sICA), a data-driven technique that addresses the blind source separation problem, seems able to extract components specifically related to physiological noise and brain movements. These components should be removed from the data to achieve structured noise reduction and improve any subsequent detection and analysis of signal fluctuations related to neural activity. We propose a new automatic method called CORSICA (CORrection of Structured noise using spatial Independent Component Analysis) to identify the components related to physiological noise, using prior information on the spatial localization of the main physiological fluctuations in fMRI data. As opposed to existing spectral priors, which may be subject to aliasing effects for long-TR data sets (typically acquired with TR >1 s), such spatial priors can be applied to fMRI data, regardless of the TR of the acquisitions. By comparing the proposed automatic selection to a manual selection performed visually by a human operator, we first show that CORSICA is able to identify the noise-related components for long-TR data with a high sensitivity and a specificity of 1. On short-TR data sets, we validate that the proposed method of noise reduction allows a substantial improvement of the signal-to-noise ratio evaluated at the cardiac and respiratory frequencies, even in the gray matter, while preserving the main fluctuations related to neural activity.     

1/f Noise QWIPs and nBn detectors

The low-frequency noise is a ubiquitous phenomenon and the spectral power density of this fluctuation process is inversely proportional to the frequency of the signal. We have measured the 1/f noise of a 640 × 512 pixel quantum well infrared photodetector (QWIP) focal plane array (FPA) with 6.2 μm peak wavelength. Our experimental observations show that this QWIP FPA’s 1/f noise corner frequency is about 0.1 mHz. With this kind of low frequency stability, QWIPs could unveil a new class of infrared applications that have never been imagined before. Furthermore, we present the results from a similar 1/f noise measurement of bulk InAsSb absorber (lattice matched to GaSb substrate) nBn detector array with 4.0 μm cutoff wavelength.     

Performance of an optical stabilization system at NSLS beamline U12IR

A low-cost optical feedback system using dynamic mirrors has been developed at the NSLS for stabilizing the position and direction of an infrared synchrotron beam against thermal drift and mechanical noise. The system design has some unique features that potentially simplify installation into an existing infrared beamline. We describe the system and its features along with some performance results.     

同步光分组交换网核心节点光分组长度分析

研究了同步光分组交换网中光分组长度的设计及其对一些网络性能参数的影响,分别推导了光分组中开销所占比率、时延及光纤延时线长度与光分组长度的关系,并给出各自相应的理论分析和数值解析,为光分组中分组长度的设计做了基础工作。     

值得重视的田口式参数设计法

本文着重论述了田口式参数设计法在半导体制造中对线宽的质量控制.通过田口式参数设计法,可以优化线宽控制对光刻过程步骤中的可控参数的条件,以便将不可控因素的影响降到最低.     

基于基片集成同轴线的双馈点圆极化天线

提出了一种采用基片集成同轴线(SICL)馈电的双馈点圆极化微带贴片天线。具体通过多馈点法实现圆极化,并通过背腔加载提高增益,增加带宽,减小后瓣,降低互耦,提高天线性能。经过仿真验证,该天线能够在42.42～56.69 GHz之间实现S₁₁<-10 dB(相对带宽为28.8%@51 GHz),在45.26～48.08 GHz之间实现轴比小于3 dB,最大增益8.9 dBi。     

How a moving passive observer can perceive its environment ? The Unruh effect revisited

We consider a point-like observer that moves in a medium illuminated by noise sources with Lorentz-invariant spectrum. We show that the autocorrelation function of the signal recorded by the observer allows it to perceive its environment. More precisely, we consider an observer with constant acceleration (along a Rindler trajectory) and we exploit the recent work on the emergence of the Green’s function from the cross correlation of signals transmitted by noise sources. First we recover the result that the signal recorded by the observer has a constant Wigner transform, i.e. a constant local spectrum, when the medium is homogeneous (this is the classical analogue of the Unruh effect). We complete that result by showing that the Rindler trajectory is the only straight-line trajectory that satisfies this property. We also show that, in the presence of an obstacle in the form of an infinite perfect mirror, the Wigner transform is perturbed when the observer comes into the neighborhood of the obstacle. The perturbation makes it possible for the observer to determine its position relative to the obstacle once the entire trajectory has been traversed.