共查询到20条相似文献,搜索用时 31 毫秒
1.
基于在轨成像物理机理的立体测绘相机成像建模与仿真综合考虑了大气辐射传输、卫星运行平台、光学系统成像、相机辐射响应等各个环节,采用数值模拟技术进行精确建模,可用于进行成像过程端到端的完整分析,评估成像系统设计可行性及成像质量。本文以可见光立体测绘相机为例,采用高精度高、分辨率地表物理模型作为输入源,首先结合立体测绘相机内外方位元素计算正视相机和前视相机CCD光敏面各亚像元区域中心的观测向量,然后根据目标相机的成像参数得到地面目标在相机入瞳处的辐亮度,最后通过光线追迹算法和光学系统点扩散函数模型计算探测器靶面的辐通量,经由探测器辐射响应模型得到数字影像。实验结果表明,正视相机几何物理模型定位精度达124 m,前视相机定位精度达193 m,能够较为可靠地模拟出立体影像,模拟方法可行。 相似文献
2.
Maha Benzarti-GhédiraHaikel Hrichi Nejmeddine JaballahRafik Ben Chaâbane Mustapha MajdoubHafedh Ben Ouada 《Physica B: Condensed Matter》2012,407(7):1051-1054
The opto-electronic properties of native poly(p-phenylene vinylene) (PPV) were tuned by the confinement of the π-conjugation and the incorporation of a sulphur group as a spacer in order to obtain a blue-green emitting polymer (PPVS). The energy band gap of the PPVS thin film has been measured by UV-vis absorption spectroscopy and evaluated to 2.87 eV. Current-voltage characteristics and impedance spectroscopy measurements performed on sandwich structures [ITO/PPVS/Al] are used to elucidate the conduction mechanisms. The static electrical characterisations showed a space charge limited conduction (SCLC) and a conductivity with low power frequency behaviour characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor RP and capacitor CP network in series with a resistor RS. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterised by an exponential trap distribution. 相似文献
3.
为了研究微穿孔板吸声结构对不稳定燃烧的抑制作用,采用高精度的计算气动声学(Computational Aeroacoustics,CAA)方法开展时域下的数值仿真。首先对带有压力时滞模型的三维声学扰动方程进行求解,给出发动机不稳定燃烧的频率信息。然后通过解析模型分析微穿孔板吸声结构的阻抗特性,并由多自由度宽频阻抗模型模拟微穿孔板对该不稳定频率的抑制作用。仿真捕捉到的不稳定燃烧频率与地面试车测得的频率相一致。表明采用的计算气动声学方法及相应模型可以准确地捕捉不稳定燃烧的频率信息,并分析微穿孔板对不稳定燃烧的抑制作用,对于工程上快速预测不稳定燃烧具有一定意义。 相似文献
4.
5.
S. Bollanti P. Di Lazzaro F. Flora L. Mezi D. Murra A. Torre 《Applied physics. B, Lasers and optics》2006,85(4):603-610
The design criteria of a Schwarzschild-type optical system are reviewed in relation to its use as an imaging system in an extreme ultraviolet lithography setup. Both the conventional and the modified reductor imaging configurations are considered, and the respective performances, as far as the geometrical resolution in the image plane is concerned, are compared. In this connection, a formal relation defining the modified configuration is elaborated, refining a rather naïve definition presented in an earlier work. The dependence of the geometrical resolution on the image-space numerical aperture for a given magnification is investigated in detail for both configurations. So, the advantages of the modified configuration with respect to the conventional one are clearly evidenced. The results of a semi-analytical procedure are compared with those obtained from a numerical simulation performed by an optical design program. The Schwarzschild objective based system under implementation at the ENEA Frascati Center within the context of the Italian FIRB project for EUV lithography has been used as a model. Best-fit functions accounting for the behaviour of the system parameters vs. the numerical aperture are reported; they can be a useful guide for the design of Schwarzschild objective type optical systems. 相似文献
6.
粒子加速器中真空元件的阻抗是引起束流不稳定的重要原因。基于储存环的新一代同步辐射光源的设计发射度更小,相应地要求更小的真空盒孔径,进而带来阻抗的显著增加,这就要求在设计阶段对真空元件的阻抗进行准确的评估和优化。阻抗测量是验证阻抗模型准确性的重要手段,而同轴线法是常用的实验室测量方法。对小孔径真空元件同轴线法纵向阻抗测量进行了研究,针对窄带阻抗元件,使用pillbox腔开展了相关的阻抗测量,研究了不同的内导体尺寸对于测量结果的影响,同时基于尾场模拟、散射参数模拟以及本征模模拟对测量结果进行了验证,模拟和测量结果符合很好,并证明原有的内导体导致谐振峰频移的理论分析应用于小孔径元件时存在偏差。此外针对非窄带阻抗元件,对条带冲击磁铁结构进行了同轴线法阻抗测量,研究了内导体对结果的影响,验证了同轴线法测量的有效性。 相似文献
7.
A fiber-optic-bundle-based optical coherence tomography (OCT) probe method is presented. The experimental results demonstrate this multimode optical fiber-bundle-based OCT system can achieve a lateral resolution of 12 microm and an axial resolution of 10 microm with a superluminescent diode source. This novel OCT imaging approach eliminates any moving parts in the probe and has a primary advantage for use in extremely compact and safe OCT endoscopes for imaging internal organs and great potential to be combined with confocal endoscopic microscopy. 相似文献
8.
9.
Microsphere has been demonstrated for imaging resolution improvement based on optical microscope, and applied in many engineering and biological fields successfully, while its mechanism is still inconclusive due to the complex physics of both near-field and far-field optics involved. In this paper, a comprehensive simulation model based on point spread function is built to develop a physical insight into microsphere optical nanoscope by numerical simulation. With this model, the Fresnel-region focusing of microsphere lens is studied, which shows the contradiction between focal spot size and focal length. Furthermore, the gap between microsphere and the sample surface is investigated by numerical simulation and experimental verification. As increasing of this gap, the image resolution declines rapidly, and the image becomes blur more and more. At last, a customized sample with a flower pattern etched on silicon substrate is demonstrated with microsphere optical nanoscope, and its feature sizes of 51 nm line width are imaged clearly. While it is generally accepted that microsphere optical nanoscope can be implemented in nano-imaging, these findings quantified the limit on image resolution of this setup, which serves as a general guideline in system design of the other microsphere or micro-particle assisted microscope/nanoscope. 相似文献
10.
11.
Analysis of High Codimensional Bifurcation and Chaos for the Quad Bundle Conductor's Galloping 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A two-degree-of-freedom model of iced, electrical quad bundle conductor is developed to comprehensively describe the different galloping behaviors observed. By applying centre manifold and invertible linear transformation, the co-dimension-2 bifurcation is analyzed. The relationships of parameters between this system and the original system are obtained to analyze and to control the galloping of the quad iced bundle conductor. The space trajectory, Lyapunov exponent and Lyapunov dimension are investigated via numerical simulation to present a rigorous proof of existence of chaos. 相似文献
12.
基于电阻抗成像技术和生物阻抗谱技术,提出一种面向生物组织检测的生物阻抗谱成像方法.该方法将目标区域可视化并精准识别目标种类,可用于肺癌早期检测,协助临床医生对早期肺癌进行精准检测,提高早期肺癌的治愈率.本文通过数值仿真的方法验证生物阻抗谱成像方法在肺癌早期检测中的可行性和有效性,仿真结果表明:1)生物阻抗谱成像方法可以实现早期肺癌区域的可视化,并精确判别出早期肺癌种类; 2)生物阻抗谱成像方法中阻抗谱的最佳采集模式是4次循环采集,最佳分类器是Linear-SVM, 5折交叉验证的平均分类准确率可以达到99.9%.为了验证仿真结果,本文选取3种具有不同电学特性的生物组织模拟癌变区域进行了检测.实验结果表明该方法可以对生物组织区域可视化,并判别出生物组织的种类.该方法可以兼顾电阻抗成像和生物阻抗谱方法的优点,有望用于肺癌早期检测. 相似文献
13.
介绍了针对环形阵列超声断层扫描的高分辨率全波形反演成像方法,不同于传统的延时叠加和渡越时间断层扫描,该方法充分考虑声传播的透射、反射、散射等特点,通过数据匹配的方法重构目标体声学参数图像。开发了环形超声换能器阵列构建超声断层扫描成像系统,并设计了适合检验成像算法的数值和物理模型,分别使用基于射线理论的回波延时叠加和初至波渡越时间断层扫描、以及基于波动理论的全波形反演方法对目标体进行图像重建,并对比其原理、分辨率、计算量等方面的特点,系统性分析了波动方法相对传统射线方法的优点和不足。结果表明,全波形反演这类充分考虑接收信号多种物理特征的方法可用于较高分辨率的声参数成像,适合与传统方法结合设计有效的超声断层扫描成像系统。 相似文献
14.
电爆丝断路开关是在电感储能系统中广泛应用的断路开关,其具有结构简单、成本低、截断能力强的特点。介绍了电爆丝工作的基本原理,其本质为一个快速增长的电阻,利用高阻抗来实现断流。通过PSpice软件建立了电流通过电爆丝断路开关工作时,其电阻变化的模型,从而可以仿真电爆丝断路开关的工作过程。设计了一组电爆丝断路开关的实验,PSpice模型仿真结果同实验结果进行了比较。结果发现,该模型起爆时刻,产生电压幅值等方面和实验结果比较接近,说明该模型比较科学合理,对以后的电爆丝断路开关的设计具有较大的参考价值。分析了产生误差的原因及该种仿真方法的局限性。 相似文献
15.
提出和发展了一种基于大数值孔径环形光锥照明的远场超分辨光学显微成像新方法, 采用将发光二极管(LED)面光源、窄带滤光和环形光锥照明相结合的特种照明方式, 实现超分辨显微成像. 建立了大数值孔径环形光锥照明成像的物理模型, 根据标量衍射理论, 在不同环形光锥照明时, 推导出光学显微系统像面衍射斑光强分布的理论计算公式; 通过Matlab求解和绘图, 得到衍射斑光强的分布图样, 从理论上证明这一成像方法可以有效提高光学显微镜的分辨率; 建立了相应的显微成像系统, 通过实验验证了该方法可有效改善显微镜的成像质量, 显著提高分辨率; 在中心波长450 nm、环形光锥数值孔径1.125—1.25时, 实验获得的分辨率至少优于150 nm, 与理论研究结果相符合, 从而证明了这一方法的可行性. 相似文献
16.
为能够较好的计算混合介质等效复介电常数和复磁导率, 提出了一种基于等效电路理论的阻抗模拟方法.导出了材料的电磁参数与材料容抗、感抗之间的对应关系, 并建立了能够较完整、精确地刻画实际复合材料的模型.通过求解混合介质的等效阻抗, 进一步反演其等效电磁参数.将计算结果与经典理论公式以及基于有限差分的数值方法进行了比较, 结果都符合得很好, 说明该方法可以用于计算材料的等效电磁参数.另外, 引入薄膜层结构来刻画表面效应等因素, 使得计算结果更加符合实验结果, 弥补了经典公式在这方面的不足, 同时也体现了该方法在刻画实际模型时所具有的优势.
关键词:
等效电磁参数
阻抗模拟
等效电路
混合介质 相似文献
17.
为研究贯通导体及其负载电路对金属腔体内部电磁场的影响,建立了不同贯通导体端接负载模型,使用电磁仿真软件CST进行仿真,利用GTEM室、矢量网络分析仪、功率放大器、ETS电场探头组建实验测试系统,验证了仿真结果的正确性,揭示了贯通导体及其电路对金属腔体内部电磁场的影响规律。研究结果表明:腔体内部电磁场同时受到贯通导体与腔体谐振的影响,在谐振频点干扰场强取得极大值,屏蔽效能取得极小值甚至为负值。贯通导体端接负载不接地与贯通导体两端开路情形相似,贯通导体端接负载直接接地时内部场显著降低,谐振频点降低,贯通导体端接负载浮点接地时内部场变化规律低频时与开路模型相似,高频时与直接接地模型相似。贯通导体端接负载的电阻值、电容值也会影响腔体的内部场。 相似文献
18.
A 10 MeV compact cyclotron (CYCHU-10) has been developing in Huazhong University of Science and Technology (HUST). The RF system includes a 10 kW RF power generator and a resonance cavity. There is no automatic frequency tuning equipment in the cavity due to space limitations, so the generator must search and track the cavity resonant frequency. AD9850 synthesizer is used to generate RF signal in the experimental prototype, and a fine sinusoidal waveform around 99 MHz is obtained with the method of picking up a special aliased signal from the synthesizer’s output, and the output power level can be set by regulating the resistor connected to the Pin ‘R set’. The final stage amplifier based on tetrode operates in the grounded cathode configuration, and the schematic of the tetrode circuit is illustrated. The method of searching the resonant frequency is discussed in detail. For the sake of a compact and robust structure, the resonance cavity will adopt non-uniform characteristic impedance coaxial structure, and the magnet surface electroplated with copper will be used as dummy Dees. The precise shapes and dimensions of the cavity are designed and simulation results are carried out in this paper. The distributions of electromagnetic field are illustrated by means of numerical calculation analysis, and the wooden model test is preformed as well. 相似文献
19.
An algebraic optical coherence tomography (OCT) method is presented in this paper for high resolution tomography imaging. The method achieves high resolution by formulating the frequency domain OCT (FD-OCT) into a ?1-optimization based algebraic reconstruction problem. The performance of the proposed algebraic method is evaluated by simulation and experiment, and compared to the FD-OCT method. It is shown that the proposed method can deliver high resolution beyond the coherence length and imaging depth bigger than the ones of the FD-OCT method. The computational load is greatly reduced compared to the traditional algebraic reconstruction methods. 相似文献