Computational Technique of Volumetric Object Reconstruction in Integral Imaging by Use of Real and Virtual Image Fields

We propose a computational reconstruction technique in large‐depth integral imaging where the elemental images have information of three‐dimensional objects through real and virtual image fields. In the proposed technique, we reconstruct full volume information from the elemental images through both real and virtual image fields. Here, we use uniform mappings of elemental images with the size of the lenslet regardless of the distance between the lenslet array and reconstruction image plane. To show the feasibility of the proposed reconstruction technique, we perform preliminary experiments and present experimental results.     

三维集成成像中无串扰显示系统的设计与实现

通过对集成成像原理和串扰现象原理的分析,基于显示系统的串扰与观察距离的关系和人眼视觉特性,提出了显示系统的无串扰设计方法。设计实例及实验结果表明,本文的三维集成成像显示系统的无串扰设计方法不仅使在预期的观察位置观看所得的三维集成像不再受串扰现象影响,而且满足人眼视觉分辨特性要求。     

基于集成成像的三维空间数字水印新技术

提出了一种基于集成成像的数字水印技术,利用基于智能深度反转模型的计算集成成像系统,生成三维数字水印;设计基于离散小波变换的嵌入与提取算法,实现了水印信息的隐藏,并利用集成成像显示三维数字水印。通过实验证明,表明新技术产生的三维数字水印不仅满足了稳健性和安全性的要求,且图像质量和显示效果均符合人类视觉模型的要求。该研究工作为三维数字多媒体产品的版权保护提供了新的思路及解决手段。     

轴对称流场的计算流动显示算法

讨论了全息干涉、纹影、阴影的计算光学原理 ,对数值计算的结果进行图形处理以模拟光学仪器的工作过程。针对轴对称流场的特殊性 ,对三维的光程积分计算进行简化 ,采用环带法用二维的计算网格计算出三维的沿光线的积分结果 ,发展了一套轴对称流场的计算流动显示的快速算法。通过计算流场图像与试验流场图像的直接比较 ,可以验证数值计算的有效性。示例给出了弹道靶中高超声速钝锥流动的应用     

Double depth-enhanced 3D integral imaging in projection-type system without diffuser

Stable porphyrin-oxygenated carbon nanomaterial dispersions were prepared by blending porphyrin solutions with hydroxyl groups modified multi-walled carbon nanotubes(MWNTs-OH)and graphene oxide(GO)dispersions,respectively.Optical nonlinearity and optical limiting(OL)property of these blends are investigated in nanosecond regime.Results show that the OL performance of the blends can be tuned by changing the concentrations ratio of porphyrin and oxygenated carbon nanomaterials.The high concentration of oxygenated carbon nanomaterial leads to the poor OL performance.However,with the moderate concentration,the blends exhibit the low threshold value of OL and the enhanced OL performance at high fluence region.The superior OL performance can be attributed to complementary mechanisms and possible photoinduced electron or energy transfer between porphyrin moiety and oxygenated carbon nanomaterials.     

基于集成成像的深度提取线性插值增强方法

分别用定义的深度提取精密度和深度提取正确度对实验结果进行分析,从结果的整体分布和整体偏差两个方面证明了线性插值对基于集成成像的深度提取具有增强作用。由于单元透镜数量众多,单个图像传感器像素个数有限,传统的基于集成成像的深度提取受到单元图像低分辨率的制约。无需额外的硬件移动,采用线性插值将单元图像像素个数增加一倍,深度提取精密度提升了20%,深度提取正确度提升了15%。集成成像可以同时实现三维场景的重建和深度的提取。这是其他深度提取技术所不具备的特点。通过使用插值后得到的深度信息,使目标物体的重建图像更为清晰。基于集成成像的深度提取可应用于三维场景的背景去除。     

一种基于逆问题的差分干涉SAR层析成像方法

高度-速率维成像时,差分干涉层析成像合成孔径雷达获取的观测数据在基线-时间平面非均匀分布。若直接对观测数据进行两维傅里叶变换来恢复散射体高度-速率维像,则因强副瓣存在,成像效果不理想。该文将差分干涉层析成像合成孔径雷达高度-速率维成像问题归结为2维积分方程的逆问题,提出了一种采用Backus-Gilbert算法实现差分干涉SAR层析成像的新方法,并使用Tikhonov正则化获得逆问题的正则解。仿真结果表明该文提出的方法能够克服基线时间不均匀造成的影响,获得较好的成像结果。     

Emerging Low‐Dimensional Nanoagents for Bio‐Microimaging

Nanomaterials with unique physical and biological properties have attracted increased attention for bio‐microimaging applications. Among them, low‐dimensional nanomaterials have quantum confinement effect in zero, one, or two dimensions, which have high specific surface area for cargo (such as dye) loading, anisotropic optical properties for polarization, and enhanced infrared absorption for efficient photoluminescence. In this review, recent efforts on bio‐microimaging of low‐dimensional nanomaterials, including confocal imaging, multiphoton imaging, Raman imaging, and super‐resolution imaging, will be highlighted. Bio‐microimaging principle, respective advantages and bottlenecks, and applications of low‐dimensional materials in various imaging technologies will be discussed. Furthermore, the review will shed light on the common synthetic methods of low‐dimensional nanomaterials. Finally, the classification and comparison of various nanomaterials, including carbon, black phosphorus, gold, metal composites, and 2D graphene analogues will also be elaborated.     

Facile Synthesis of Graphene Quantum Dots from 3D Graphene and their Application for Fe3+ Sensing

Owing to their small size, biocompatibility, unique and tunable photoluminescence, and physicochemical properties, graphene quantum dots (GQDs) are an emerging class of zero‐dimensional materials promising a wide spectrum of novel applications in bio‐imaging, optical, and electrochemical sensors, energy devices, and so forth. Their widespread use, however, is largely limited by the current lack of high yield synthesis methods of high‐quality GQDs. In this contribution, a facile method to electrochemically exfoliate GQDs from three‐dimensional graphene grown by chemical vapor deposition (CVD) is reported. Furthermore, the use of such GQDs for sensitive and specific detection of ferric ions is demonstrated.     

Improved Viewing Quality of 3‐D Images in Computational Integral Imaging Reconstruction Based on Round Mapping Model

In this paper, we propose a computational integral imaging reconstruction (CIIR) method using a round mapping model to improve the viewing quality of 3‐D images. The proposed CIIR method can overcome the problem of non‐uniformly reconstructed images caused by the conventional method. To show the usefulness of proposed method, some experiments are carried out and the results are presented.     

Hierarchical Composite Electrodes of Nickel Oxide Nanoflake 3D Graphene for High‐Performance Pseudocapacitors

NiO nanoflakes are created with a simple hydrothermal method on 3D (three‐dimensional) graphene scaffolds grown on Ni foams by microwave plasma enhanced chemical vapor deposition (MPCVD). Such as‐grown NiO‐3D graphene hierarchical composites are then applied as monolithic electrodes for a pseudo‐supercapacitor application without needing binders or metal‐based current collectors. Electrochemical measurements impart that the hierarchical NiO‐3D graphene composite delivers a high specific capacitance of ≈1829 F g^?1 at a current density of 3 A g^?1 (the theoretical capacitance of NiO is 2584 F g^?1). Furthermore, a full‐cell is realized with an energy density of 138 Wh kg^?1 at a power density of 5.25 kW kg^?1, which is much superior to commercial ones as well as reported devices in asymmetric capacitors of NiO. More attractively, this asymmetric supercapacitor exhibits capacitance retention of 85% after 5000 cycles relative to the initial value of the 1^st cycle.     

2D Image Construction from Low Resolution Response of a New Non‐invasive Measurement for Medical Application

This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important.     

Curved Projection Integral Imaging Using an Additional Large‐Aperture Convex Lens for Viewing Angle Improvement

In this paper, we propose a curved projection integral imaging system to improve the horizontal and vertical viewing angles. The proposed system can be easily implemented by additional use of a large‐aperture convex lens in conventional projection integral imaging. To obtain the simultaneous display of 3D images through real and virtual image fields, we propose a computer‐generated pickup method based on ray optics and elemental images, which are synthesized for the proposed system. To show the feasibility of the proposed system, preliminary experiments are carried out. Experimental results indicate that our system improves the viewing angle and displays 3D images simultaneously in real and virtual image fields.     

三维寄生电容边界元计算的半解析积分方法

在VLSI三维多介质互连寄生电容的边界元法计算中,利用互连结构特点,本文提出一种半解析积分方法,它应用原函数方法将二维面积分转化为一维线积分,再用一维高斯积分求出积分值.与二维高斯积分相比,速度更快、精度更高,并改善了解的精度.     

光束阵列扫描LM APD阵列三维成像方法性能分析

激光三维成像是空间目标自主交会中相对位姿信息获取的关键技术,线性模式雪崩光电二极管阵列成像具有帧频高、小型化、功耗低等优势,能够适用于星载平台三维成像要求。但是目前国内阵列探测器像元数量有限,需要采用扫描方式提高三维成像分辨率。本文针对光束阵列扫描三维成像方法在空间非合作目标三维成像的应用场景,分析了该成像方法的成像性能。分析结果表明,光束阵列扫描方法能够有效提高LM APD阵列三维成像分辨率,且在能量效率、光束均匀性等方便均有较好的表现。     

The time integral program for output section of broadband klystrons

This paper presents a single period, one dimensional time integral model, with which we calculate the energy exchange between the rf field and electrons in the output section of a klystron. A method is given by which the distance integral can be simply transformed into the time integral and the calculation of the space charge force of electron disks in the output section can be resolved. A program with DJS-6 type computer automation language is written to calculate a C-band klystron. The calculated results are in good agreement with the experimental ones. We have also studied the influence of the parameters of the output section on the efficiency of the klystron.     

An Efficient PAB‐Based Query Indexing for Processing Continuous Queries on Moving Objects

Existing methods to process continuous range queries are not scalable. In particular, as the number of continuous range queries on a large number of moving objects becomes larger, their performance degrades significantly. We propose a novel query indexing method called the projected attribute bit (PAB)‐based query index. We project a two‐dimensional continuous range query on each axis to get two one‐dimensional bit lists. Since the queries are transformed to bit lists and query evaluation is performed by bit operations, the storage cost of indexing and query evaluation time are reduced significantly. Through various experiments, we show that our method outperforms the containment‐encoded squares‐based indexing method, which is one of the most recently proposed methods.     

Wavelet-based compression algorithm for still omnidirectional 3d integral images

Three dimensional (3D) integral imaging is a method that allows the display of full colour images with continuous parallax within a wide viewing zone. Due to the significant quantity of data required to represent a captured 3D integral image with high resolution, image compression becomes mandatory for the storage and transmission of integral images. This paper investigates the use of 2D discrete wavelet transform (2D-DWT) for the compression of omnidirectional 3D integral images (OII). The method requires the extraction of different viewpoint images from the integral image. A single viewpoint image is constructed by extracting one pixel from each microlens, then each viewpoint image is decomposed using a 2D-DWT. The resulting array of coefficients contains several frequency bands. The lower frequency bands of the viewpoint images are assembled and compressed using a 3D discrete cosine transform (3D-DCT) followed by Huffman coding. Whereas, the remaining higher bands are fed directly into a quantisation process followed by arithmetic coding. Simulations are performed on a set of several grey level 3D OII using a uniform scalar quantizer with deadzone. It was found that the algorithm achieves better rate-distortion performance and reconstructs the images with much better image quality at very low bit rates than previously reported 3D-DCT-based scheme.     

Three‐dimensional radiation pattern measurement strategy for ground station antennas

This article describes how to measure a three‐dimensional antenna radiation pattern and the most effective method to achieve this. We present a new automated three‐dimensional measurement scheme, inspired by the seed pattern of a sunflower seed head, where the seed placements are arranged in a way so that rotational symmetry is obtained to compromise the circular shape of a dish antenna radiation pattern in the three‐dimensional space. This new AU–TUM Antenna Radiation Measurement Strategy has produced superior results. It has been shown by this scheme that for instance the three‐dimensional transmission pattern of a dish antenna can be measured automatically and easily checked against present regulations. The generic AU–TUM Antenna Radiation Measurement Strategy was verified on a 4.8‐m Ka‐band dish antenna. It was concluded that a three‐dimensional radiation pattern can be measured two to thirteen times faster than the best performing current strategies. Copyright © 2012 John Wiley & Sons, Ltd.     

A Link Between Integrals and Higher‐Order Integrals of SPN Ciphers

Integral cryptanalysis, which is based on the existence of (higher‐order) integral distinguishers, is a powerful cryptographic method that can be used to evaluate the security of modern block ciphers. In this paper, we focus on substitution‐permutation network (SPN) ciphers and propose a criterion to characterize how an r‐round integral distinguisher can be extended to an (r+1)‐round higher‐order integral distinguisher. This criterion, which builds a link between integrals and higher‐order integrals of SPN ciphers, is in fact based on the theory of direct decomposition of a linear space defined by the linear mapping of the cipher. It can be directly utilized to unify the procedure for finding 4‐round higher‐order integral distinguishers of AES and ARIA and can be further extended to analyze higher‐order integral distinguishers of various block cipher structures. We hope that the criterion presented in this paper will benefit the cryptanalysts and may thus lead to better cryptanalytic results.