基于高阶统计量双相干理论的图像篡改识别算法

随着图像处理技术的快速地发展和广泛地应用,图像篡改变得越来越容易和普及.恶意篡改的图像会对新闻、司法等领域造成极大的负面影响.对基于高阶统计量双相干理论的图像篡改检测方法进行了深入研究,论述了该方法的原理,并应用该方法进行了大量的分类真假图像对照实验,分析了该方法的适用条件和局限性,实验结果表明,该方法的识别准确率与拼...     

X射线衍射φ旋转及其应用

介绍了Ｘ射线衍射φ旋转方法，结合具体实例说明了该方法在单晶片全方位定向、研究生长薄膜层与衬底的取向关系、研究生长薄膜层中缺陷、以及在该系统辅助下应用非对称θ－２θ衍射技术研究生长层与衬底界面晶格失配方的应用。     

求作Fs、M图的快捷方法——积分法

本文主要讨论了绘制剪力、弯矩图的快捷方法——．积分法，通过该快捷方法的应用，使工程技术人员、学生能更快、更好地掌握该方法，并利用其为工程中梁的弯曲强度计算提供便利。     

齐次线性方程组基础解系列处理法

利用正交化列处理法和线性变换，给出了一个确定任意齐次线性代数方程组解空间结构的数值计算方法；分析了该方法的收敛性、计算复杂度、数值稳定性和内在并行性，进而探讨了该方法的应用前景。     

深度学习在计算成像中的应用

近年来,深度学习被广泛应用于计算成像中,并取得了令人瞩目的成果,已成为该领域的研究热点。为了深入了解现有基于深度学习的方法是如何解决众多计算成像问题的,主要介绍了该方法的基本理论和实施步骤,然后以散射成像、数字全息及计算鬼成像中的应用为例具体介绍该方法的有效性和优越性。汇总对比了一些典型应用,并对基于深度学习的计算成像方法进行了总结和展望。     

浅谈"平分"方法在物理实验中的应用

介绍了“平分”方法的数学原理,结合典型的物理实验,针对具体的实验过程,给出了该方法的一些应用实例,并讨论了在实验中应用该方法的重要性.     

Jacobi椭圆函数展开法及其在求解非线性波动方程中的应用

给出了Jacobi椭圆函数展开法,且应用该方法获得了几种非线性波方程的准确周期解.该方法包含了双曲函数展开法,应用该方法得到的周期解包含了冲击波解和孤波解. 关键词： Jacobi椭圆函数 非线性方程 周期解 孤波解     

特定折射率材料及光学薄膜制备

根据太阳电池阵激光防护膜性能优化的需要,应用离子辅助电子束双源共蒸工艺方法制备了优化设计所需的特定折射率的薄膜材料并用于制备激光防护膜。测试结果显示:用该工艺方法制备的掺杂材料薄膜的折射率n=1.75,与优化设计所需数值相符;激光防护膜性能优良,太阳辐射能透过率提高6%以上,实现了对该激光防护膜性能的进一步优化。为了使该双源共蒸方法适于大面积薄膜的制备,应用均匀性挡板技术来提高该方法制备大面积薄膜的膜厚均匀性,使制备的掺杂材料薄膜在口径为400 mm时的不均匀性小于2.1%。该双源共蒸方法制备工艺简单、可靠,适于实际工程应用。薄膜性能测试结果与理论优化结果相符,达到预期优化目标。     

阵列光纤在牙色测量系统中的应用

提出一种在牙色测量系统中应用阵列光纤色度传感器的新方法。该方法能够解决牙色测量中的复杂问题。采用该方法，可实现快速、精确的牙色测量，同时也能补偿平面光栅多色仪的色散。     

基于莫尔拓扑与图像处理的三维形貌术

本文叙述了一种新型三维物体表面测量方法,该方法利用单光栅投射待测物体表面而获取变形光栅像,然后应用图像处理方法,通过微机计算出物体表面各点高度。该方法测试精度高,速度快。文中对其原理进行了详细的叙述。并讨论了该法的测量范围、灵敏度。     

Generation of an acoustically bright zone with an illuminated region using multiple sources

This article addresses the way in which we can generate an "acoustically bright zone" in a space. The bright zone is defined as the volume where we can have higher acoustic energy than in other space. A method is proposed to generate the bright zone by controlling multiple monopole sources. Two kinds of cost functions involved with acoustic brightness are defined. One is the ratio of the brightness of a zone to the input power, and the other expresses the "contrast" between the bright zone and the other space. Through eigenvalue analysis, the optimal volume velocity distribution of the monopoles has been obtained.     

The 22 GHz radio-aeronomy receiver at Onsala Space Observatory

We present a radiometer system for regular long-term measurements of water vapour in the middle atmosphere. To be able to do continuous and long-term measurements a simple, robust, reliable and automatic system is needed. Our system therefore is based on a stable, uncooled, HEMT amplifier frontend and on a digital spectrometer backend. In order to minimise reflections in the frontend transmission line, which distort the signal due to standing waves, we have designed a corrugated receiver horn, which combines good characteristics (low return loss and sidelobes) and narrow beamwidth to simplify the receiver optics. In order to make the radiometer system as simple as possible, we use the sky as the calibration cold load. This is possible since we use the observed brightness temperatures of an already existing broadband dual-channel 21.0/31.4-GHz radiometer, at the observation site, to estimate the brightness temperature of the sky at . However, we have developed a calibration method, which makes it possible to estimate the sky brightness temperature even if we cannot use the dual-channel radiometer. Despite new measurements, which became available in recent years, the determination of middle atmospheric water vapour distribution still remains a challenge due to the fact that there is a large dispersion among the different measurement methods and data sets, which are obtained on a sparse and sporadic basis. This is the reason why several instruments similar to ours currently are developed in Europe.     

城市典型地物的热辐射特性研究

运用热红外技术监测地表温度已获得成熟的发展,城市化进程的加快使得城市热岛效应日益显现,有关城市典型地物热辐射特性的研究对于分析城市热岛现象的成因和分布具有重要意义。本文通过对保定市地面实测数据的研究发现,地物类型、观测时间和墙面朝向是影响城市典型地物热辐射亮度温度的主要因素。结果显示,地物类型的不同显著影响其亮度温度,但仍存在同谱异物现象;不同时间观测到的地物热辐射强度不同,且在很大程度上影响其在各通道上的亮温差异;不同朝向墙面的亮温也有差异,且这种差异随观测时间而改变。对城市典型地物热辐射特性的研究具有理论和实践意义,为热红外遥感监测城市热岛效应提供了依据。     

Fast radiative transfer modeling for infrared imaging radiometry

Fast radiative transfer codes have been developed for simulating the outgoing radiance (and corresponding brightness temperature) to be measured by the Infrared Imaging Radiometer (IIR) of the space Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission. Two simple codes (FASRAD and FASAA), for which scattering is neglected, as well as an accurate code (FASDOM), accounting for scattering and absorption with the Discrete Ordinate Method (DOM), are presented. Their accuracy has been estimated with a reference code including a line-by-line model and the DOM. Simulations have shown that the accuracy is generally better than 0.3 K on the brightness temperature for clear or cloudy atmospheres. This accuracy agrees with the expected one of future IIR measurements. In addition, the impact of scattering on the brightness temperature has been evaluated for semi-transparent liquid clouds in the IIR spectral range. Especially, simulations have shown that cloud microphysics retrieval might be possible with the Brightness Temperature Difference (BTD) between two IIR bands, using the couple of wavelengths (8.7-) or (10.6-). However, scattering strongly influences the radiation for shorter wavelengths. The error on the BTD with (8.7-) can reach 4 K when scattering is neglected, leading to large uncertainties in the retrieval of droplet effective radius.     

气溶胶垂直非均一分布对天空背景亮度的影响

对白天天空背景亮度进行了数值实验;模拟了不同标高下的气溶胶垂直分布对天空背景亮度的影响;比较了不同垂直分层和整层均匀气溶胶分布下,天空背景亮度的相对偏差,并分析了天空背景亮度对地表反射率的敏感性。结果表明:给定气溶胶光学厚度下,不同标高的垂直分布得到的天空背景亮度差别很大;天空背景亮度对地表反射率和气溶胶总光学厚度都比较敏感,敏感程度受太阳-观测几何的影响。     

Effect of KI/LiF/CdCl2 on photoluminescent and electroluminescent properties of nanocrystalline (Zn-Cd)S: Cu films

The effect of KI/LiF/CdCl₂ on photoluminescent and electroluminescent (EL) spectra have been reported for (Zn-Cd)S:Cu films. Nanocrystalline films of (Zn-Cd)S:Cu have been prepared using chemical deposition technique in aqueous alkaline bath and their subsequent condensation on substrates. Important results in terms of XRD, SEM, absorption spectra, PL and EL spectra, voltage and frequency dependence of EL brightness are presented. Also, EL brightness waves, EL decay and dependence of EL brightness on nature of electrode material are presented and discussed. SEM studies show best growth conditions in the presence of CdCl₂. Results of XRD studies are associated to ZnS and CdS. Both the studies show average particle sizes to be in the nano order. PL and EL emissions from different films show emission peaks in the blue–green region. Results of absorption spectra show a slight change in band gaps owing to the addition of impurities. Voltage dependence of EL brightness shows effectiveness of acceleration–collision mechanism. Frequency dependence of EL brightness first shows an increase in brightness in the lower frequency range, followed by saturation at higher frequencies. Brightness waves consist of primary and secondary waves, which depend on voltage and frequency of excitation. EL cells with Al electrode give better brightness compared with cells with Ag electrodes. The lifetimes of EL emission are found to be of the order of microseconds.     

基于光谱响应差异的HJ-1B热红外通道星上定标系数验证

HJ-1B卫星热红外通道自发射以来共进行了7次星上黑体定标,然而针对星上定标系数的验证工作开展较少。通过半高宽法、矩方法和查找表法计算得到2009年9月14日星上定标系数。以具有较高定标精度的MODIS为参考源,基于MODIS第31,32通道和HJ-1B热红外通道的光谱响应特性,改进对应热红外通道的光谱匹配算法,建立两传感器表观辐亮度的匹配关系,进而通过Planck公式计算出HJ-1B热红外通道的等效水表亮温,通过与HJ-1B热红外通道基于星上定标系数得到的反演水表亮温进行比较,实现对星上定标系数的验证。以光谱响应差异计算的等效亮温值为285.97 K,半高宽法、矩方法和查找表法星上定标系数反演亮温值分别为288.77,274.52和285.97 K。结果显示,半高宽法、矩方法和查找表法星上定标系数反演亮温与光谱响应差异计算的等效亮温偏差分别为2.8,-11.46和0.02 K。结果表明,HJ-1B热红外通道星上定标方法中以查找表法星上定标系数计算结果精度较高。同时证明了基于光谱响应差异的HJ-1B热红外通道星上定标系数验证方法有效可行。     

Phase aberration correction in medical ultrasound using speckle brightness as a quality factor

Medical ultrasonic images are degraded by tissues with inhomogeneous acoustic velocities. The resulting phase aberration raises the off-peak response of the imaging system's point spread function (PSF), decreasing dynamic range. In extreme cases, multiple images of a single target are displayed. Phase aberration may become a limiting factor to image quality as ultrasonic frequency and aperture size are increased in order to improve spatial resolution. A method is proposed to correct for unknown phase aberration, which uses speckle brightness as a quality factor. The phase delays of a phased array transducer are modified, element by element, to maximize mean speckle brightness in a region of interest. The technique proposed is analogous to the correction technique used by Muller and Buffington [J. Opt. Soc. Am. 64 (9), 1200-1209 (1974)] to adaptively focus incoherent optical telescopes. The method is demonstrated using a computer model with several different simulated aberration profiles. With this model, mean speckle brightness is calculated using the two-dimensional PSF. Experiments have also been conducted in which speckle brightness is shown to increase as the phase delays of an ultrasonic scanner are modified in order to compensate for a rippled aberrating layer made of silicone rubber. The characteristics of the proposed method, and the possibility of employing it clinically to correct for unknown inhomogeneities in acoustic velocity, are discussed.     

白天全天空背景测量与分析

开展了白天全天空背景亮度特性数据库研究。利用测量设备进行天空背景全天候测量,对测量数据进行分析与处理,建立了白天天空背景理论模型,提出了基于理论模型的修正完善方法,建立了该位置全天空背景亮度数据库,可给出任意时刻背景亮度值。解决了连续特定位置背景提取难的问题,提高了提取的数量和精度。     

Adaptive gamma correction based on cumulative histogram for enhancing near-infrared images

Histogram-based methods have been proven their ability in image enhancement. To improve low contrast while preserving details and high brightness in near-infrared images, a novel method called adaptive gamma correction based on cumulative histogram (AGCCH) is studied in this paper. This novel image enhancement method improves the contrast of local pixels through adaptive gamma correction (AGC), which is formed by incorporating a cumulative histogram or cumulative sub-histogram into the weighting distribution. Both qualitatively and quantitatively, experimental results demonstrate that the proposed image enhancement with the AGCCH method can perform well in brightness preservation, contrast enhancement, and detail preservation, and it is superior to previous state-of-the-art methods.