为了应对能源枯竭和环境污染这一关乎人类生存的重要问题,太阳能电池是利用太阳能这一低廉并且对环境友好的清洁能源的有效手段。但是光伏器件易受灰尘、粉尘等固体微颗粒污染物的影响,从而大大减少光电转化效率,因此在光伏器件表面引...为了应对能源枯竭和环境污染这一关乎人类生存的重要问题,太阳能电池是利用太阳能这一低廉并且对环境友好的清洁能源的有效手段。但是光伏器件易受灰尘、粉尘等固体微颗粒污染物的影响,从而大大减少光电转化效率,因此在光伏器件表面引入超疏水自清洁薄膜则成为一种潜在有效的清洁手段。基于前人研究并参考“荷叶表面微观结构”,提出了一种具有高透光的SiO2微孔膜耦合ZnO纳米棒的分级自清洁结构,通过FDTD方法对设计的薄膜结构进行相应的数值模拟,得到了三组透过率、反射率和吸收率等数据曲线,以及膜结构内部不同截面的电场分布。从模拟结果来看,该膜结构在微纳分级复合结构保证超疏水性的同时,具有优异的光学性能和极强的推广可行性。To address the critical issue of energy depletion and environmental pollution that threatens human survival, solar cells represent an effective means of harnessing solar energy, a low-cost and environmentally friendly clean energy source. However, photovoltaic devices are susceptible to the influence of solid particulate pollutants such as dust and powder, which can significantly reduce their photoelectric conversion efficiency. Therefore, introducing a superhydrophobic self-cleaning film on the surface of solar panels has become a potentially effective cleaning solution. Based on previous research and inspired by the microstructure of lotus leaf surfaces, we propose a hierarchical self-cleaning structure composed of a highly transparent silica microporous film coupled with zinc oxide nanorods. The designed film structure was numerically simulated using the FDTD method, yielding three sets of data curves for transmittance, reflectance, and absorptance, as well as the electric field distribution at different cross-sections within the film structure. The simulation results indicate that the film structure maintains super-hydrophobicity through its micro-nano hierarchical composite structure while exhibiting excellent optical properties and strong feasibility for widespread application.展开更多
复杂形状的纳米星一直是认识等离子体现象的主要障碍。本文通过时域有限差分(FDTD)方法,对纳米星形结构进行模拟分析。我们对不同几何参数(如粒子直径、金星分支尖角的粗细和金星分支的数量)下的光谱响应进行了数值研究,以阐明纳米星的...复杂形状的纳米星一直是认识等离子体现象的主要障碍。本文通过时域有限差分(FDTD)方法,对纳米星形结构进行模拟分析。我们对不同几何参数(如粒子直径、金星分支尖角的粗细和金星分支的数量)下的光谱响应进行了数值研究,以阐明纳米星的光学特性与几何结构之间的关系。另外,还在金纳米星的基础上耦合了银,发现可以通过调整银的不同含量来调谐纳米星的消光峰,而且能提升纳米粒子的电场增强。我们的结果为确定选择不同激发波长的SERS应用中纳米星的几何形状提供了理论指导。这项工作为开发具有宽吸收光谱增强电磁场的等离子金属晶体结构铺平了道路。此外,这项研究还为医学成像和农药残留检测提供了一种有效的SERS基底。The complex shape of nanostars has been a major obstacle to understanding plasma phenomena. In this paper, the finite difference Time domain (FDTD) method is used to simulate and analyze the nanostar structure. Numerical studies of spectral responses under different geometric parameters such as particle diameter, the thickness of Venusian branches, and the number of Venusian branches are carried out to clarify the relationship between the optical properties of nanostars and their geometric structure. In addition, silver is coupled to the gold nanostars, and it is found that the extinction peak of the nanostars can be tuned by adjusting the different content of silver, and the electric field enhancement of the nanoparticles can be improved. Our results provide theoretical guidance for determining the geometry of nanostars in SERS applications where different excitation wavelengths are selected. This work paves the way for the development of plasma metallic structures with a wide absorption spectrum enhanced electromagnetic field. In addition, this study provides an effective SERS substrate for medical imaging and pesticide residue detection.展开更多
基于管道渗漏异常区与周边土壤存在明显介电差异特点,采用了一种分辨率高、抗干扰能力强、高效、无损的探地雷达(GroundPenetratingRadar,GPR)检测成像技术,用以解决地下管道渗漏异常区的准确识别问题。为了提高对地下管道渗漏雷达图像...基于管道渗漏异常区与周边土壤存在明显介电差异特点,采用了一种分辨率高、抗干扰能力强、高效、无损的探地雷达(GroundPenetratingRadar,GPR)检测成像技术,用以解决地下管道渗漏异常区的准确识别问题。为了提高对地下管道渗漏雷达图像特征的认识,采用时域有限差分法(Finite Difference Time Domain,FDTD)模拟了不同材质管道、不同填充物质、不同渗漏位置和范围下的GPR电磁波响应特征,并应用偏移成像技术将分散于目标体两侧的能量汇聚,使反射波正确归位,有效提高探地雷达剖面横向分辨率,最终确立地下管道渗漏正演模拟特征图谱,为实际探地雷达探测图像解释提供理论基础。实例管道探测结果表明,探地雷达法可准确识别有效探测深度下管道两侧一定范围的渗漏异常,且异常特征清晰、显著。模拟结果可为地下管道渗漏探测识别提供参考。展开更多
对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transfo...对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。展开更多
文摘为了应对能源枯竭和环境污染这一关乎人类生存的重要问题,太阳能电池是利用太阳能这一低廉并且对环境友好的清洁能源的有效手段。但是光伏器件易受灰尘、粉尘等固体微颗粒污染物的影响,从而大大减少光电转化效率,因此在光伏器件表面引入超疏水自清洁薄膜则成为一种潜在有效的清洁手段。基于前人研究并参考“荷叶表面微观结构”,提出了一种具有高透光的SiO2微孔膜耦合ZnO纳米棒的分级自清洁结构,通过FDTD方法对设计的薄膜结构进行相应的数值模拟,得到了三组透过率、反射率和吸收率等数据曲线,以及膜结构内部不同截面的电场分布。从模拟结果来看,该膜结构在微纳分级复合结构保证超疏水性的同时,具有优异的光学性能和极强的推广可行性。To address the critical issue of energy depletion and environmental pollution that threatens human survival, solar cells represent an effective means of harnessing solar energy, a low-cost and environmentally friendly clean energy source. However, photovoltaic devices are susceptible to the influence of solid particulate pollutants such as dust and powder, which can significantly reduce their photoelectric conversion efficiency. Therefore, introducing a superhydrophobic self-cleaning film on the surface of solar panels has become a potentially effective cleaning solution. Based on previous research and inspired by the microstructure of lotus leaf surfaces, we propose a hierarchical self-cleaning structure composed of a highly transparent silica microporous film coupled with zinc oxide nanorods. The designed film structure was numerically simulated using the FDTD method, yielding three sets of data curves for transmittance, reflectance, and absorptance, as well as the electric field distribution at different cross-sections within the film structure. The simulation results indicate that the film structure maintains super-hydrophobicity through its micro-nano hierarchical composite structure while exhibiting excellent optical properties and strong feasibility for widespread application.
文摘复杂形状的纳米星一直是认识等离子体现象的主要障碍。本文通过时域有限差分(FDTD)方法,对纳米星形结构进行模拟分析。我们对不同几何参数(如粒子直径、金星分支尖角的粗细和金星分支的数量)下的光谱响应进行了数值研究,以阐明纳米星的光学特性与几何结构之间的关系。另外,还在金纳米星的基础上耦合了银,发现可以通过调整银的不同含量来调谐纳米星的消光峰,而且能提升纳米粒子的电场增强。我们的结果为确定选择不同激发波长的SERS应用中纳米星的几何形状提供了理论指导。这项工作为开发具有宽吸收光谱增强电磁场的等离子金属晶体结构铺平了道路。此外,这项研究还为医学成像和农药残留检测提供了一种有效的SERS基底。The complex shape of nanostars has been a major obstacle to understanding plasma phenomena. In this paper, the finite difference Time domain (FDTD) method is used to simulate and analyze the nanostar structure. Numerical studies of spectral responses under different geometric parameters such as particle diameter, the thickness of Venusian branches, and the number of Venusian branches are carried out to clarify the relationship between the optical properties of nanostars and their geometric structure. In addition, silver is coupled to the gold nanostars, and it is found that the extinction peak of the nanostars can be tuned by adjusting the different content of silver, and the electric field enhancement of the nanoparticles can be improved. Our results provide theoretical guidance for determining the geometry of nanostars in SERS applications where different excitation wavelengths are selected. This work paves the way for the development of plasma metallic structures with a wide absorption spectrum enhanced electromagnetic field. In addition, this study provides an effective SERS substrate for medical imaging and pesticide residue detection.
文摘基于管道渗漏异常区与周边土壤存在明显介电差异特点,采用了一种分辨率高、抗干扰能力强、高效、无损的探地雷达(GroundPenetratingRadar,GPR)检测成像技术,用以解决地下管道渗漏异常区的准确识别问题。为了提高对地下管道渗漏雷达图像特征的认识,采用时域有限差分法(Finite Difference Time Domain,FDTD)模拟了不同材质管道、不同填充物质、不同渗漏位置和范围下的GPR电磁波响应特征,并应用偏移成像技术将分散于目标体两侧的能量汇聚,使反射波正确归位,有效提高探地雷达剖面横向分辨率,最终确立地下管道渗漏正演模拟特征图谱,为实际探地雷达探测图像解释提供理论基础。实例管道探测结果表明,探地雷达法可准确识别有效探测深度下管道两侧一定范围的渗漏异常,且异常特征清晰、显著。模拟结果可为地下管道渗漏探测识别提供参考。
文摘探地雷达(Ground Penetrating Radar,GPR)正演模拟是解译和反演实测GPR数据的基础。然而,使用传统时域有限差分方法(Finite Difference Time Domain,FDTD)实现GPR正演模拟时,时间步长受到Courant Friedrichs Lewy(CFL)条件严格限制,存在运算耗时较长的问题,为此,提出使用局部一维隐式时域有限差分方法(Locally One Dimension Finite Difference Time Domain,LOD-FDTD)实现二维GPR正演模拟。LOD-FDTD使用Crank-Nicolson方法从FDTD中推导得到,该方法的时间步长不受CFL条件限制,能够使用大时间步快速完成GPR正演模拟。对均质模型以及含多层界面和多个地质体的复杂地质模型进行GPR正演模拟实验,结果表明,在占用内存空间小于120MB的情况下,LOD-FDTD方法能够使用FDTD最大时间步长2倍以上的时间步长,有效地计算雷达波在地下空间的传播过程,并获得不同地质体的GPR响应信号,证明了本文方法具有占用内存适中、运算速度快、求解精度好等优点,较传统FDTD能够快速、高效地实现GPR正演模拟。
文摘对已有的Z变换时域有限差分法(Z-transformation Finite Difference Time Domain,Z-FDTD)在电磁波与非均匀磁化等离子体中的传输特性分析的计算误差问题进行了研究,并探讨了一种修正计算误差的Z变换时域有限差分方法(Modified Z-transform Finite Difference Time Domain,MZ-FDTD),以提升Z-FDTD方法对非均匀磁化等离子体的适用性。对MZ-FDTD和Z-FDTD之间的计算误差问题,通过严格的公式推导求得该误差的计算公式,并引入误差分析因子,对比分析了该误差受空间步长和非均匀磁化等离子体的物理特性的影响特征,在充分的误差分析与网格参数对比后,以电磁波在非均匀磁化等离子体中的传输特性为分析目标,举例说明了MZ-FDTD的优越性。研究结果表明,相比于经典Z-FDTD,通过MZ-FDTD方法计算得到的数值结果具有更高的计算准确度,较低的运行时间和较少的运行内存占用。此外,对电磁波在非均匀等离子体中传输特性分析的举例说明也证明了相比于Z-FDTD,优化的Z-FDTD方法无论是在较低频段还是较高频段都保持较好的稳定性。在今后的工作中,使用MZ-FDTD方法研究非均匀磁化等离子体问题将会获得更好的计算结果,这项工作中的误差分析方法也将对某些计算电磁学在等离子体中的应用与优化工作起到一定的帮助作用。
文摘提出一种新的节省计算空间的FDTD-PWS混合算法,并应用于透镜天线的焦面场分析.首先采用FDTD(Finite-Difference Time-Domain)求解得到聚焦透镜天线的口面场的幅度和相位分布,再通过PWS(Plane Wave Spectrum)外推至焦平面,求解得出焦面场分布.根据天线场分布的对称性,将PEC(Perfect Electric Conductor)和PMC(Perfect Magnetic Conduc-tor)边界应用于FDTD的仿真过程,使仿真模型缩减为原模型的1/4,进一步节省了计算空间.应用于毫米波聚焦透镜天线的焦面场仿真分析,并对其焦面场进行平面近场扫描测试,将仿真结果进行探头补偿后与实验数据作比较,证明该方法是精确和高效的.
