红外迷彩伪装涂料发射率对目标伪装效率的影响

伪装效率是衡量涂料的红外伪装效果的重要指标，它取决于涂料本身的红外发射率、特定的环境背景和气候条件等多种因素。在一种典型的南方草地背景下，随着阳光辐射和昼夜环境温度的变化，研究了不同发射率涂料样品的红外伪装效率；并对不同发射率的样品进行组合，研究比较复杂的红外迷彩伪装目标的伪装效率，在此基础上，讨论了发射率对红外迷彩伪装目标的伪装效率的影响。     

关于红外半球全发射率与温度关系的讨论

从红外物理基本定律出发，推导出了红外半球全发射率随温度变化的函数关系解析表达式，得出物体的半球全发射率均随温度升高而降低的结论。     

一种在8—12μm波段高发射率涂料的研制

影响目标红外辐射亮度有两个因素：表面温度和发射率。运用涂料是改变发射率的一种简单可行的方法，使用不同发射率的涂料能够灵活有效地使目标热变形，达到隐身的目的。我们研制的一种高发射率涂料（ＦＨ９４－１型）由粘合剂、着色染料、填加剂配制而成。用红外光谱仪测得该涂料在８￣１２μｍ波段有较强吸收特性，这种吸收特性主要来自填加剂。使用ＡＧＥＭＡ９００热像仪，测得８￣１２μｍ波段法向平均发射率εｎ等于０．９２。     

红外发射率控制方法及机理研究

红外发射率的控制具有广泛的用途,根据电磁波理论,讨论了物体表面的发射率与折射率的关系,折射率大的物体发射率低.电致变色材料是一种可控制其表面折射率和发射率的材料.以氧化钨为例探讨了发射率的控制方法.利用电场对三氧化钨薄膜进行离子和电子的共注入和共抽取,三氧化钨中的载流子浓度发生了变化,折射率和红外发射率也发生了变化.     

一种在8—12μm波段高发射率涂料的研制

影响目标红外辐射亮度有两个因素：表面温度和发射率。运用涂料是改变发射率的一种简单可行的方法，使用不同发射率的涂料能够灵活有效地使目标热变形，达到隐身的目的。我们研制的一种高发射率涂料（ＦＨ９４－１型）由粘合剂、着色染料、填加剂配制而成。用红外光谱仪测得该涂料在８￣１２μｍ波段有较强吸收特性，这种吸收特性主要来自填加剂。使用ＡＧＥＭＡ９００热像仪，测得８￣１２μｍ波段法向平均发射率εｎ等于０．９２。     

热处理对氧化铋在8μm～14μm波段内的发射率的影响

本文通过设计正交实验,采用不同的热处理工艺对着色颜料氧化铋粉末进行热处理,随后测量样品在8μm～14μm波段的平均法向发射率,并得出优化的热处理工艺路线;对各个影响因素进行的分析表明,温度是热处理过程中影响样品发射率变化的主要因素,并通过XRD、SEM、EDS等多种表征手段,分析了红外发射率变化的内在机理.结果表明,晶格畸变是引起发射率变化的主要因素,而由气体分子吸附引起的表面成分变化对发射率也有一定的影响.     

双波段红外反隐身技术研究

本文详细分析了气象和环境因素对不同发射率的目标表面辐射温度的影响，得出了有关公式并进行了计算机仿真分析。结果表明，采用低发射率涂料可以有效地对付单一波段的红外热成象系统的侦察，但双波段红外热成象系统结合简单的图象处理技术可以成功地揭露这种方式的伪装。     

热处理对氧化铅红外发射率的影响

在不同温度下对氧化铅进行热处理,并对样品进行了XRD、红外光谱以及红外发射率方面的测试.结果表明:随着热处理温度的升高,样品的晶体结构产生转变,红外发射率先降低后升高,当热处理温度为400℃时最低(3～5μm波段为0.08,8～14μm波段为0.58).经分析后认为热处理后氧化铅的发射率变化是由于其微观晶体结构转变产生的品格振动的变化引起的,当氧化铅晶体结构致密、间隙率小时,红外发射率较低.     

干燥裸地红外辐射统计特性：发射率起伏的影响

根据干燥裸露地表的稳态热平衡方程，考虑到地表的感热交换和天空热辐射的作用，用Monte-Carlo方法分析了风场下地表发射率空间起伏对裸露地表红外辐射统计特性的影响。结果表明：由于地表发射率在空间的起伏变化，地表热红外图像的反差将显著增加；地表辐射温度概率密度分布的偏态与峰度也不同程度地发失变化。     

紧凑型发射率和温度测量红外探测仪

为了评价有关目标如飞机和其他飞行器的红外特性，需要具备能够测量发射率的仪器。现有的用于测量发射率的实验室仪器体积大，难以操作，而且工作时还需要精心控制实验室环境，所以它们是不适合在野外进行简单操作的。     

Implementation of transparent sources in FDTD simulations

Sources can be embedded in a finite-difference time-domain (FDTD) grid in any one of several ways. Depending on the particular implementation, the embedded source corresponds physically to a hard field source (applied field), a transparent current source (impressed current), a finite-impedance voltage source, or some other physical excitation. While the implementation of any of these sources is a straightforward procedure in FDTD simulations, ensuring an accurate correspondence between the physical source and its numerical implementation is challenging. We describe the implementation of a new field source, referred to as a transparent field source, that couples the same fields into the FDTD grid as a hard field source. Unlike the hard field source, however, the transparent source does not scatter energy, i.e., the usual FDTD update equation applies to the source node. The implementation is described both in terms of a single node and in terms of an array of nodes. The latter is discussed in the context of parallel-plate waveguide excitation     

Admissibility properties or Gilbert's encoding for unknown source probabilities (Corresp.)

Huffman coding provides optimal source encoding for events of specified source probabilities. Gilbert has proposed a scheme for source encoding when these source probabilities are imperfectly known. This correspondence shows that Gilbert's scheme is a Bayes scheme against a certain natural prior distribution on the source probabilities. Consequently, since this prior distribution has nonzero mass everywhere, Gilbert's scheme is admissible in the sense that no source encoding has lower average code length for every choice of source probabilities.     

Influence Coefficient Method for Calculating Discrete Heat Source Temperature on Finite Convectively Cooled Substrates

A simple method is developed for predicting discrete heat source temperatures on a finite convectively cooled substrate. The method is based on the principle of superposition using a single source solution for the mean or maximum contact temperature of an eccentric uniform heat source on a rectangular substrate. By means of influence coefficients, the effect of neighboring source strength and location may be assessed. It is shown that the influence coefficients represent localized thermal resistances, which must be weighted according to source strength. For a system of$N$heat sources, there exists$N$effects of source strength and position on any one heat source. This includes a self effect (source of interest) and$N$$-$1 influence effects (neighboring sources). The method is developed for isotropic, orthotropic, and compound systems. Convection in the source plane is addressed for isotropic and orthotropic systems. Expressions are developed for both mean and centroidal temperature.     

Local Linear Estimators for the Bioelectromagnetic Inverse Problem

Linear estimators have been used widely in the bioelectromagnetic inverse problem, but their properties and relationships have not been fully characterized. Here, we show that the most widely used linear estimators may be characterized by a choice of norms on signal space and on source space. These norms depend, in part, on assumptions about the signal space and source space covariances. We demonstrate that two estimator classes (standardized and weight vector normalized) yield unbiased estimators of source location for simple source models (including only the noise-free case) but biased estimators of source magnitude. In the presence of instrumental (white) noise, we show that the nonadaptive standardized estimator is a biased estimator of source location, while the adaptive weight vector normalized estimator remains unbiased. A third class (distortionless) is an unbiased estimator of source magnitude but a biased estimator of source location.     

热源温度对热压自然通风房间内污染物浓度分布的影响

在房间有初始污染物浓度和有均匀分布污染源两种情况下,对热压自然通风房间内的污染物浓度分布进行数值模拟,指出热源温度越高,有初始污染物的房间内浓度分层高度越高,有均匀分布污染源的房间内污染物被清除的效果越好。综合两种情况的浓度分布特征,表明热源温度越高,室内平均污染物浓度越低且污染物在室内的水平分布更均匀。     

双程前向掺铒光子晶体光纤超荧光光源

为了获得高稳定光纤陀螺掺铒光纤光源和改进传统掺铒光纤超荧光光源的输出稳定性,提出和使用掺铒光子晶体光纤作为超荧光光源的增益媒介。构建了双程前向结构掺铒光子晶体光纤超荧光光源, 研究了这种新型光源的输出特性。分析了掺铒光子晶体光纤长度和泵浦功率对光源输出功率、光谱谱宽和平均波长的影响。结果表明,通过选取光纤长度为10 m 和泵浦功率为220 mW,获得了双程前向结构掺铒光子晶体光纤超荧光光源。输出功率为35.4 mW,光光转换效率约16.09%,谱宽为30.9 nm,平均波长为1 548.3 nm。该结果为进一步研究掺铒光子晶体光纤超荧光光源的环境温度稳定性和适应性奠定基础。     

单相电压源变换器减少开关次数调制算法的研究

作为基本的电力电子变换器,单相全桥结构两电平电压源变换器包括单相电压源逆变器、单相并网逆变器、单相电压源整流器和单相有源电力滤波器,具有广泛的应用场合。鉴于单相电压源变换器具有多解性,可以寻找一种减少开关次数的调制算法,以便降低开关损耗。本文根据三相电压源全桥结构两电平电压源变换器的最小开关次数调制算法,设计了一种适合单相全桥结构两电平电压源变换器的最少开关次数的调制算法,在理论分析的基础上,采用MATLAB/SIMULINK进行了仿真验证。     

New Bounds on the Expected Length of Optimal One-to-One Codes

In this correspondence, we consider one-to-one encodings for a discrete memoryless source, which are "one-shot" encodings associating a distinct codeword with each source symbol. Such encodings could be employed when only a single source symbol rather than a sequence of source symbols needs to be transmitted. For example, such a situation can arise when the last message must be acknowledged before the next message can be transmitted. We consider two slightly different types of one-to-one encodings (depending on whether the empty codeword is used or not) and obtain lower and upper bounds on the expected length of optimal one-to-one codes. We first give an extension of a known tight lower bound on the expected length of optimal one-to-one codes for the case that the the size of the source alphabet is finite and partial information about the source symbol probabilities is available. As expected, our lower bound is no less than the previously known lower bound obtained without side information about the source symbol probabilities. We then consider the case that the source entropy is available and derive arbitrarily tight lower bounds on the expected length of optimal one-to-one codes. We also derive arbitrarily tight lower bounds for the case that the source entropy and the probability of the most likely source symbol are available. Finally, given that the probability of the most likely source symbol is available, we obtain an upper bound on the expected length of optimal one-to-one codes. Our upper bound is tighter than the best upper bound known in the literature     

Am improved tail current source for low voltage applications

A new current source for low-voltage applications is proposed. This current source is well suited for biasing differential pairs and source followers. Measured compliance voltage is slightly smaller than that of a single transistor. Its output resistance is a factor of 25 larger than that of a single transistor current source and was measured to be 8 MΩ. The use of the new current source improves the common-mode input range and the common-mode rejection ratio of fully balanced and single-ended differential amplifiers