新型热红外伪装体系

针对热红外成像侦察技术对军事目标形成的严重威胁，介绍了三种新机理型热红外伪装体系：1）三色涂料体系，三色涂料以一定形式叠加在军事目标上，利用涂层和孔洞的明暗实现目标与背景在红外及可见光区的融合。2）相变材料体系，将相变材料以微胶囊的形式分散在基体中，利用其发生相变时伴随的吸热效应，对目标产生的热量和目标温度加以控制。3）簇饰物伪装体系，选用低发射率的聚合物薄层材料做成叶簇状物附在常规伪装网上，在移动目标的周围产生空气流，从而达到散热和抑制目标红外辐射的目的。     

相变材料应用于红外热成像假目标的初步研究

红外热成像假目标因其独特的军事价值，受到了广泛的重视．测试了不同厚度、不同环境温度，不同用量条件下的熔化过程中，不同种类相变材料在相变温度附近的维持时间，分析了相变材料应用于红外热成像假目标的技术途径，初步验证了其可行性．     

相变微胶囊与热红外隐身

在论述了相变微胶囊(PCM)的特点及应用于热红外隐身技术(TIS)的可能性基础上,指出了TIS对PCM的要求、应用条件及困难,首次提出了热反射/温度自适应红外隐身复合涂层(TTC),并对其设计指导思想、涂层结构、涂层功能、实验结果以及在热红外隐身中的应用可能进行了分析.复合涂层面层为降温作用为主的热反射隔热层.中间层为调节温度为主的相变涂层,底层为耐蚀涂层,分析及初步试验结果表明:热反射/温度自适应红外隐身复合涂层在一定温度范围内,具有明显的降温及温度自适应功能,有利于实现目标与背景的红外融合,为对抗双波段红外热像仪反隐身技术提供可能.     

基于标准黑体的物体表面发射率计算方法研究

红外测温仪器的精度和被测物体表面的发射率对测量物体红外辐射特性的准确性影响很大。为了提高物体表面发射率的计算精度,先通过标准黑体对红外热像仪进行标定。然后,利用标定好的红外热像仪测量温度,计算出被测物体表面的发射率。将基于神经网络的红外热像仪标定方法应用到目标发射率的求解方法中,有效地消除了热像仪的系统误差。测试装置简单,测试结果准确。同时,温度和发射率的精确测量为红外隐身材料的研制奠定了基础。     

热红外复合隐身涂层的性能研究

基于红外隐身技术实现的基本原理,提出了热红外复合隐身涂层的设计方案,即控制涂层表面温度和8～14μm波段红外发射率。从这两点出发,重点研究了低发射涂层铝粉、ITO粉和降温涂料相变微胶囊的制备。实验证明,进口Al粉和新型ITO粉在8~14μm波段平均红外发射率分别为0.236和0.478,相变微胶囊在相变区间内有一定的降温效果。实验结果对今后热红外复合隐身涂层的研究有很重要的指导意义。     

新型热红外复合隐身涂层的研究

本文介绍了红外隐身技术实现的基本原理,探讨了新型热红外复合隐身涂层的制备工艺和初步性能测试,即发射率、降温性能、隔热性能的测试.作为降温材料,相变微胶囊的大规模制备,使得新型热红外隐身涂层的实现有了可能.实验结果为红外复合隐身涂料的实用化研究提供了重要参考.     

红外烟幕遮蔽条件下目标热像的增强

根据红外烟幕遮蔽条件下目标热像的特征提出了一种减少红外烟幕遮蔽干扰时间的动态局部自适应直方图均衡化增强目标热像新方法。该方法采用一个滑动窗口动态地对感兴趣的目标区域计算不断变化的红外热像图的灰度分布，然后根据该区域局部直方图进行均衡化实现对整个窗口中像素的灰度级变换增强。采用该方法有效地改善了选定区域的目标红外图像，使红外烟幕的有效遮蔽时间减少了3～5s，为有效地跟踪和发现目标提供了宝贵的时间。     

红外热像仪对面目标的作用距离的公式推导及误差分析

通过分析红外热像仪镜头处所接收到的辐照度,结合红外辐射的基本理论,推导出红外热像仪对面目标的作用距离公式,讨论了影响红外热像仪对面目标的作用距离的各种因素,给出了误差计算模型．     

二氧化钒在红外自适应隐身技术中的应用

二氧化钒(VO2)是一种热致可逆相变氧化物,在约68℃时发生由半导体态向金属态的一级位移型相变,同时伴随着显著的电学、磁学、光学特性的变化,且相变温度可通过掺杂调节。制备了二氧化钒粉体和薄膜材料,分别研究了两种材料的热致红外发射率变化特性;采用热像仪拍摄了二氧化钒涂层和薄膜不同温度的红外热图,探讨了其在隐身技术中的应用。结果表明:二氧化钒涂层和薄膜在相变前后具有主动控制自身辐射强度的特性,在红外自适应隐身技术中具有一定的应用前景。     

地面机动目标的红外伪装技术探讨

利用红外热像仪对行驶中车辆的红外特征进行了实验测试和研究,在对传统红外伪装 技术分析的基础上,探讨了机动目标红外伪装的难点,提出了针对重要地面机动目标的新型红外伪装技术,并介绍了实验测试方法。     

Phase‐Change Materials Based Nanoparticles for Controlled Hypoxia Modulation and Enhanced Phototherapy

Tumor hypoxia strengthens tumor resistance to different therapies especially oxygen involved strategies, such as photodynamic therapy (PDT). Herein, the thermal responsive phase change materials (PCM) are utilized to coencapsulate ultrasmall manganese dioxide (sMnO₂) and organic photosensitizer IR780 to obtain IR780‐sMnO₂‐PCM nanoparticles for controlled tumor hypoxia modulation and enhanced phototherapy. The thermal responsive protective PCM layer can not only prevent IR780 from photodegradation, but also immediately release sMnO₂ to decompose endogenous H₂O₂ and generate enough oxygen for PDT under laser irradiation. Owing to the efficient accumulation of IR780‐sMnO₂‐PCM nanoparticles in tumor under intravenous injection as revealed by both florescence imaging and photoacoustic imaging, the tumor hypoxia is greatly relieved. Furthermore, in vivo combined photothermal therapy (PTT) and PDT, IR780‐sMnO₂‐PCM nanoparticles, compared to IR780‐PCM nanoparticles, exhibit better performance in inhibiting tumor growth. The results highlight the promise of IR780‐sMnO₂‐PCM in controlled modulation of tumor hypoxia to overcome current limitations of cancer therapies.     

针对可见光、红外、激光的光电复合隐身涂料实现方法研究

简述了可见光、激光、红外隐身涂料各自的作用机理,分析了欲制成光电复合隐身涂料所必须处理好的三者之间存在的矛盾点.从材料学角度详细讨论了如何消除矛盾点解决涂料兼容性的问题并分别提出了可见光与红外、红外与激光及三者间构成光电复合隐身涂料的实现方法.重点研究了低发射率颜料、相变微胶囊及半导体掺杂技术在涂料复合中的应用.具有良好效果及广阔发展前景.最后介绍了国外光电复合隐身涂料的最新进展情况.     

光热敏微胶囊材料的光引发固化特性研究

选取光引发剂184、聚合树脂(TMPTA)作为裹芯固化物质, 采用界面聚合法对光固化物质包囊, 扫描电镜、激光粒度仪观测表明光热敏微胶囊形貌规则, 峰值粒径为0.3 μm。热重分析获得微胶囊热分解温度高于350 ℃, 该材料在室温下具有热稳定性。利用吸收光谱、红外光谱研究了光热敏微胶囊的光引发固化反应过程。结果表明所得光热敏微胶囊的光谱吸收峰位于310 nm, 半峰全宽为30 nm; 曝光后TMPTA在1620 cm-1处的C=C双键吸收峰和920.1 cm-1, 837 cm-1处的C=C键上C-H键吸收峰减小, 说明光热敏微胶囊内光固化是TMPTA在引发剂引发下, 通过C=C双键打开形成空间网络的交联聚合过程。对比不同曝光条件下的影像密度特性, 确定裹芯固化最佳曝光时间为20 s。     

0-3型水泥基压电复合材料有限元分析与优化

用ANSYS有限元软件对纯压电陶瓷(PW)及0-3型水泥基压电复合材料(PCM0)依次进行静力、模态、谐响应及瞬态动力特性力-电耦合场分析,并以PCM0半径(Rc)和厚度(Hc)为变量对进行材料量优化设计。相比PW,PCM0垂直于极化方向的电位移增大10.9%,使压电应变常数增大;响应频率减小,呈稳态响应特性;水泥掺入对PCM0迟滞效应影响可接受。PCM0最优材料用量对应的Rc、Hc分为5.1mm、0.76mm。     

Optimum PCM Codes for DPSK

The effect of digital errors in PCM systems for speech signals depends on the PCM code used. The standard binary folded PCM code is superior to the natural binary code but it is not optimum. This paper considers PCM codes especially designed to be insensitive to the double error patterns produced by DPSK. It is concluded that the dynamic range with especially designed PCM codes is considerably extended compared to standard binary folded PCM. Special simplified interleaving schemes and optimum PCM codes for coherent PSK are also considered. The dynamic behavior of various PCM codes is calculated and compared, e.g., asymptotically optimum PCM codes for DPSK, binary folded PCM with and without interleaving, asymptotically optimum PCM codes for coherent PSK, etc. We conclude that the best scheme for DPSK is simplified interleaving and an optimum PCM code for PSK. This paper also gives analytical formulas for double errorA-factors for standard PCM systems.     

Synchronizability of a General Class of PCM Formats, Including NRZ, Manchester, and Miller Coding

This paper deals with a general class of PCM formats, which includes the well-known NRZ, Manchester, and Miller coding. We show that the Cramér-Rao lower bound on the mean-square error, resulting from a synchronizer which estimates the delay of a noisy PCM waveform, is inversely proportional to a quantity which depends on the PCM format only. This quantity is termed the "synchronizability" of the PCM format. For the general class of PCM formats we consider in this paper, we obtain as a simple result that the synchronizability equals four times the mean number of zero-crossings of the PCM waveform during one symbol period. Numerical results are presented for NRZ, Manchester, and Miller coding.     

Operation time control of a high density packaging using a low melting point alloy

This paper describes a concept of controlling operation time of a high-density packaging using a phase change material (PCM). A low cost alloy, which is composed of Bi/Pb/Sn/In and having melting point less than 343 K, was used as the PCM. Thermal experiments using the alloy were carried out and it was confirmed that the substrate back surface temperature could be kept constant at the melting temperature of the PCM for several minutes by thermal absorption, while the PCM phase changed from its original solid state into the liquid state. Also, in the present work, it was confirmed that thermal network method is practically useful for the thermal design of a package with a PCM.     

Semiconductor laser dynamics for feedback from afinite-penetration-depth phase-conjugate mirror

Most of the previous treatments of semiconductor lasers subject to optical feedback from a phase-conjugate mirror (PCM) have assumed that the PCM responds instantaneously. Furthermore, the mechanism responsible for phase conjugation does not usually enter into the analysis. In this paper, we derive the time-dependent reflectivity of a PCM created through nondegenerate four-wave mixing in a Kerr-type nonlinear medium. The resulting laser dynamics are compared with the case of the ideal PCM, as a function of the external-cavity length, the PCM reflectivity, and the PCM interaction depth. The PCM with a significant interaction depth tends to suppress otherwise chaotic output and produces pulses whose repetition rate is tunable by varying PCM reflectivity. At high feedback levels, it stabilizes the laser output. We use the circle-map formalism to explain our numerical results     

Analysis of Digital Errors in Nonlinear PCM Systems

The effect of digital errors in linear pulse code modulation (PCM) systems has been considered by several authors for channels with independent errors. In this paper we present a general approach of analyzing digital errors in linear and nonlinear PCM systems with arbitrary channels. The examples given in this paper cover the different standard nonlinear PCM systems and independent channel errors. The technique used for the analysis leads to the conclusion that there are PCM codes less sensitive to digital errors than the standard binary folded PCM code. An example of such a PCM code is given in this paper.     

Investigation of 9.6 kb/s data transmission via a pcm link at 64 kb/s with and without link errors

The problem of pulse code modulation (PCM) bit errors causing voice frequency (VF) modem errors has been studied in detail. The error mechanism consists of the addition of an impulse response type error signal added to the reconstructed VF data signal waveform at the digital-to-analogue (D/A) output of the PCM decoder. This error signal may cause a burst of errors registering in the VF modem receiver, depending on which PCM bit is in error. Numerous data have been collected in a laboratory experiment and analysed in various ways. The average bit error rate (BER) enhancement factor of VF data over PCM is between 10 and 20. For each PCM bit in error, an average of two VF data bits are in error. The analysis leads to suggestions for possible solutions to the problem.