Design of Ka-band Monolithic Image Rejection Mixer

In this paper, a 30–40 GHz monolithic image rejection mixer is described. The mixer employs two drain LO injection mixer cells, which can perform well even with zero drain bias voltage. Also it employs Lange Coupler for RF quadrature signal generation. The mixer is fabricated by a commercial 0.18-μm pseudomorphic high electron-mobility transistor (pHEMT) process. It achieves image rejection ratio of more than 20.4 dB and conversion loss of less than 12.6 dB in the frequency range of 30 to 38 GHz.     

镜像光衍射技术及其在测量中的应用

对光衍射技术提出了一种新方法,即在衍射缝后引入反射形成镜像,用以改变衍射条纹的光强分布,这种方法可提高测量精度,加大动态范围,改善因缝不理想所形成的场分布,还对参数的选取进行了讨论。     

砷化镓半导体材料与器件中高频场分布研究的新方法——脉冲电光检测技术

介绍了砷化镓材料和器件中高频电场的分布测量的新方法——谐波混频脉冲电光检测:它的原理、实验装置以及在砷化镓共平面波导中微波驻波场分布测量中应用的结果.在频率高达20.10GHz及开路、短路和50Ω不同的负载条件下测得的结果与理论预计值符合很好.本文最后对方法的灵敏度和空间分辨率进行讨论.     

A Novel Hyperchaotic 2D-SFCF with Simple Structure and Its Application in Image Encryption

In this paper, a novel image encryption algorithm is proposed based on hyperchaotic two-dimensional sin-fractional-cos-fractional (2D-SFCF), called sin-fractional-cos-fractional image-encryption (SFCF-IE). The 2D-SFCF is constructed from two one-dimensional cosine fractional (1-DCFs), and it has a more complex chaotic behavior with a larger parameter space than one-dimensional chaotic systems. Compared with the two-dimensional (2D) chaotic system, the 2D-SFCF has a simple structure, and the parameter space in the chaotic state is continuous, which is beneficial to generating the keystream in the cryptosystem. Therefore, in the novel image encryption algorithm, we use the 2D-SFCF to generate the keystream of the cryptosystem. The encryption algorithm is a process of scrambling and diffusion. Different from common diffusion methods, the diffusion starting position of the SFCF-IE is randomly generated, enhancing the algorithm’s security. Simulation experiments show that the image encrypted by this algorithm has better distribution characteristics and can resist common attack methods.     

马铃薯光谱及数字图像特征参数对氮素水平的响应及其应用

为准确、快速地掌握马铃薯氮素状况,提高马铃薯对氮素的利用率,采用便携式高光谱地物波谱仪、数码相机与SPAD-502叶绿素仪获取马铃薯冠层图像、叶片光谱、叶片SPAD值,分析不同施氮水平下马铃薯两个关键生育时期数字化指标、叶片光谱指标、SPAD、产量的变化状况,以SPAD为辅助验证指标,以产量为氮素施用效率评价,分析数字化指标、叶片光谱与SPAD、产量的关系,明确最佳施氮水平下数字化指标、叶片光谱指标的临界值,以期探讨快速、简便进行马铃薯氮素营养诊断的方法。结果表明：(1)随着施氮水平的增加红边位置出现了“红移”,红边参数REP,Lwidth,FD_Max增加,Lo减小。(2)随着施氮水平增加数字化指标G/B和(G-B)/(R+G+B)逐渐降低,B/(R+G+B)逐渐增加。(3)SPAD随施氮量增加而提高,施氮量增加低氮水平增产效果明显,高氮水平增产效果不明显。光谱、红边参数、数字化指标与SPAD、产量相关性较好,据此建立了各个指标评价马铃薯氮营养丰缺的量化标准。表明运用数字图像与光谱技术进行马铃薯氮素营养诊断具有可行性,为马铃薯精准氮素营养监测提供研究思路与技术支撑。     

Single Neuronal Dynamical System in Self-Feedbacked Hopfield Networks and Its Application in Image Encryption

Image encryption is a confidential strategy to keep the information in digital images from being leaked. Due to excellent chaotic dynamic behavior, self-feedbacked Hopfield networks have been used to design image ciphers. However, Self-feedbacked Hopfield networks have complex structures, large computational amount and fixed parameters; these properties limit the application of them. In this paper, a single neuronal dynamical system in self-feedbacked Hopfield network is unveiled. The discrete form of single neuronal dynamical system is derived from a self-feedbacked Hopfield network. Chaotic performance evaluation indicates that the system has good complexity, high sensitivity, and a large chaotic parameter range. The system is also incorporated into a framework to improve its chaotic performance. The result shows the system is well adapted to this type of framework, which means that there is a lot of room for improvement in the system. To investigate its applications in image encryption, an image encryption scheme is then designed. Simulation results and security analysis indicate that the proposed scheme is highly resistant to various attacks and competitive with some exiting schemes.     

Modified Hilbert Curve for Rectangles and Cuboids and Its Application in Entropy Coding for Image and Video Compression

In our previous work, by combining the Hilbert scan with the symbol grouping method, efficient run-length-based entropy coding was developed, and high-efficiency image compression algorithms based on the entropy coding were obtained. However, the 2-D Hilbert curves, which are a critical part of the above-mentioned entropy coding, are defined on squares with the side length being the powers of 2, i.e., 2ⁿ, while a subband is normally a rectangle of arbitrary sizes. It is not straightforward to modify the Hilbert curve from squares of side lengths of 2ⁿ to an arbitrary rectangle. In this short article, we provide the details of constructing the modified 2-D Hilbert curve of arbitrary rectangle sizes. Furthermore, we extend the method from a 2-D rectangle to a 3-D cuboid. The 3-D modified Hilbert curves are used in a novel 3-D transform video compression algorithm that employs the run-length-based entropy coding. Additionally, the modified 2-D and 3-D Hilbert curves introduced in this short article could be useful for some unknown applications in the future.     

DNP-EPR多功能谱仪中微波桥的设计与实现

在自主研制的动态核极化（Dynamic Nuclear Polarization,DNP）分子影像装置的基础上,提出了一种集DNP和电子顺磁共振（Electron Paramagnetic Resonance,EPR）于一体的多功能谱仪,并对其中的关键部件之一--微波桥进行了设计.微波桥的引入,实现了DNP微波发射机的集成化,以及在DNP谱仪基础上的EPR功能扩展.通过结构设计、电路仿真及系统测试,完成了高频谱纯度、高动态范围的微波发射机以及低噪声系数的微波检测系统的设计与制作.并通过DNP增强实验以及连续波EPR实验对微波桥的性能进行了验证.     

A New Hyperchaotic 4D-FDHNN System with Four Positive Lyapunov Exponents and Its Application in Image Encryption

In this paper, a hyperchaotic four-dimensional fractional discrete Hopfield neural network system (4D-FDHNN) with four positive Lyapunov exponents is proposed. Firstly, the chaotic dynamics’ characteristics of the system are verified by analyzing and comparing the iterative trajectory diagram, phase diagram, attractor diagram, 0-1 test, sample entropy, and Lyapunov exponent. Furthermore, a novel image encryption scheme is designed to use the chaotic system as a pseudo-random number generator. In the scenario, the confusion phase using the fractal idea proposes a fractal-like model scrambling method, effectively enhancing the complexity and security of the confusion. For the advanced diffusion phase, we proposed a kind of Hilbert dynamic random diffusion method, synchronously changing the size and location of the pixel values, which improves the efficiency of the encryption algorithm. Finally, simulation results and security analysis experiments show that the proposed encryption algorithm has good efficiency and high security, and can resist common types of attacks.     

光子晶体微波加速结构的计算与设计

用有限差分法计算了由金属棒分别按方形和三角形晶格分布的二维光子晶体的色散曲线, 得出了带隙图．计算结果表明: 对于三角形晶格, 当金属棒半径和棒间距比值小于0.2时, 由该种光子晶体构成的微波加速结构可约束主模、抑制高次模; 用Microwave Studio软件模拟计算了三角形晶格分布的二维光子晶体加速结构, 研究了新加速结构的RF参数与结构尺寸的关系, 优化出一组RF频率为9.37GHz时此种加速腔的结构尺寸, 计算还表明该种新加速结构具有较高的分路阻抗和品质因数.     

数字光弹性中五步彩色相移法及其应用

把相移法与光学彩色信息图像处理技术相结合,提出全场数字化确定主方向角的光弹性五步彩色相移法。其主要优点是采用最简单的白光平面偏振仪光学系统,由数码照相机采集五幅等色线与等倾线相互耦合的彩色条纹图,经计算机进行处理后,就可以得到[O～π／2]范围内单纯连续的等倾角相图;为了减少测量误差,在相移法中引入背景光强参与运算。对实验中存在的三种主要误差因素进行了定量分析,给出了具体的误差控制指标。用对径压缩圆盘问题的理论仿真模拟结果、基本实验和复杂平面及空间实际问题进行检验和对比,表明本方法是正确可行的。     

3D组织培养模型及其在辐射诱导旁效应研究中的应用

综述了3D细胞培养技术（TDCC）的发展, 3种主要的体外组织构建方法; 辐射诱导2D细胞产生旁效应的现象与机理; 人工构建的3D组织辐射后诱导的旁效应及其细胞间信号传导机理。 重离子（C离子）辐照作为一种重要的放疗工具, 对其辐射处理3D组织后诱导产生的旁效应进行了展望。 由于3D组织更接近人体细胞生长的真实环境, 因而以3D组织作为模型研究辐射诱导的旁效应, 对于辐射旁效应的防护和治疗可能具有重要的指导意义。 Compared with the cultured monolayer (2D) cells, three dimensional (3D) tissue could be more similar to the environment in vivo including the physical support, chemical factors, cell cell and cell matrix interaction and so on. With the development of three dimensional cell culture techniques (TDCC), 3D tissue is widely used in the areas of bystander effect research. This review focuses on introducing the TDCC method and its application in bystander effect research. First, the development process of 3D tissue culture method was introduced. Secondly, the induction of radiation induced bystander effects both in 2D cell and 3D tissue and its mechanisms were reviewed. Finally, because heavy ion (carbon ion beam) has been developed as a useful tool to cure solid cancer ,and the 3D tissue model is an ideal material to study the damages on body after being irradiated and to understand the underlying mechanisms, future study about heavy ion radiation inducing bystander effect in 3D tissue was discussed.     

High Speed Terahertz Pulse Imaging in the Reflection Geometry and Image Quality Enhancement by Digital Image Processing

We describe the formation and enhancement of two dimensional pulsed terahertz (THz) images obtained in the reflection geometry with a high-speed optical delay line. Two test objects are imaged and analyzed with respect to material information and concealed structure. Clear THz images were obtained with various imaging modes and were compared with the X-ray images. The THz image of a sample revealed material features that the X-ray image cannot distinguish. We could enhance the THz image quality using various image processing techniques, such as edge detection, de-noising, high-pass filtering, and wavelet filtering.     

一阶模的滤除及在Y分支和多模干涉结构中的应用

Y分支和多模干涉结构广泛应用于平面光波导器件中，在这些器件中，Y分支和多模干涉结构输出对称性具有重要意义。引入Y分支和多模干涉结构输出的不对称主要原因是这两种结构中产生了一阶导模，设计一种新的耦合器结构，在这个结构中．两根单模波导分别放置在一根多模波导两边，并且单模波导的传播常量与多模波导的一阶模的传播常量相同，这种结构可以将一阶导模滤除。在Y分支和多模干涉结构中使用了这种结构，模拟结果表明，采用这种耦合器的Y分支和多模干涉结构具有非常好的输出对称性。     

一种基于三氟甲基取代的2-苯并[b]噻吩基吡啶配体的红色电致磷光材料及器件

研究了一种新型红色磷光材料及其在有机电致磷光器件(OLEDs)中应用.在经典红色磷光材料btp₂Ir(acac)的配体2-苯并噻吩吡啶的吡啶环的5位引入吸电子基团CF₃,将辅助配体换为2-吡啶甲酸,成功研制出了双(2-(2′-苯并[b]噻吩基)吡啶)吡啶甲酸合铱配合物[(btfmp)₂Ir(pic)].这种结构可以改变了原配合物的电子云分布,三氟甲基的引入将导致原分子的LUMO能下降,减小了HOMO与LUMO的能隙,引起发光峰位的红移,但2-吡啶甲酸又可引起发光蓝移,最终得到了最大峰位为637nm的饱和红光新的铱(Ⅲ)配合物,为通过简单配体修饰设计和制备新的有机磷光材料提供了一种简洁途径.     

Application of FDTD Method to the Analysis and Design of Leaky-Wave Antennas at Microwaves and Millimeter Waves

The Finite-Difference Time-Domain (FDTD) method, though rather heavy from the computational point of view, allows a complete characterization of a radiating structure, permitting also the accuracy evaluation of the other available solutions. Numerical results have been derived for a broad class of leaky-wave antennas proposed in the literature, always revealing a very good agreement with the methods previously employed. By the FDTD technique it is possible to easily determine the propagation and radiation characteristics of such structures, to obtain the radiation pattern in the far field, and to simulate the longitudinal tapering, necessary to satisfy the design requirements usually imposed to reduce sidelobes in the radiation diagram.     

Flow-field dynamics of the non-reacting and reacting jet in a vitiated cross-flow

The dynamics of a premixed ethylene-air jet injected transverse to a vitiated cross-flow were investigated using high-repetition rate particle image velocimetry (PIV). Both non-reacting and reacting jets were found to be characterized by a dominant frequency associated with the jet wake vortex system. For the isothermal jet, increasing the momentum flux ratio (J) has only a slight effect on the frequency of the oscillation but significantly increases its magnitude. The reacting jet was found to exhibit different behavior, with a monotonic increase in the dominant frequency with J. The jet equivalence ratio (?_j) was found to have little effect on the rate of wake vortex shedding but affects the overall magnitude of the oscillation. Comparison with data reported in the literature suggests the relationship between the wake Strouhal number (St_w) and J is fuel dependent. Application of a vortex detection algorithm shows a stark difference in the location of the wake vortices under non-reacting and reacting conditions. Under isothermal conditions, the vortices are found close to the jet centerline and dissipate relatively quickly. Reaction confines the vortices to a narrow shear layer until a farther distance downstream and the vortices convect through the entire area of interest. Additionally, the vortex circulation strength was found to increase with J. Proper orthogonal decomposition (POD) analysis of the non-reacting and reacting jets demonstrates the dominance of the wake vortex structures in the oscillating flow fields. In both cases, the temporal information extracted from the most energetic modes is identical to the dominant frequencies measured in the flow fields. The primary effect of heat release is to reduce the overall amount of coherence and to delay the appearance of elevated coherence levels until a larger streamwise distance from the jet exit.     

New Generalized Transformation Method and Its Application in Higher-Dimensional Soliton Equation

A new generalized transformation method is presented to find more exact solutions of nonlinear partial differential equation. As an application of the method, we choose the (3+1)-dimensional breaking soliton equation to illustrate the method. As a result many types of explicit and exact traveling wave solutions, which contain solitary wave solutions, trigonometric function solutions, Jacobian elliptic function solutions, and rational solutions, are obtained. The new method can be extended to other nonlinear partial differential equations in mathematical physics.     

双随机位相编码信息隐蔽传递过程中的融合和重构图像质量的研究

利用具有高度保密性的双随机位相编码技术,通过灰度迭加方法将编码信息的实部和虚部同时隐藏在一幅足够大的宿主图像中。在提取隐藏图像过程中直接对携带隐藏信息的融合图像进行处理,不需要利用原始宿主图像,且重构图像的质量较好,不受宿主图像的影响。在此基础上进一步对影响融合和重构图像质量的因素进行了讨论,结果表明,对于确定的宿主图像和隐藏图像可通过调整迭加权重得到最佳效果。     

Aqueous Cobalt(II) ion as a Nitrogen-14 Chemical Shift Reagent and Its Application to the Determination of Betaine,Glycerophosphorylcholine and Ammonium Ion

Aqueous cobalt(II) ion is shown to be an effective chemical shift reagent for nitrogen-14 nuclear magnetic resonance spectroscopy. Addition of an 8 fold excess of cobalt (II) ion to a mixture of betaine, glycerophosphorylcholine and ammonium ion results in baseline resolution of the three components. The chemical shift of each component is a function of cobalt concentration up to a molar ratio of about 4:1 after which, the shifts