A novel modified four path method (FPM) is presented for calculating coupling field of super-low altitude aircraft target. Based on the hybrid method PO + MEC (Physical Optics and Method of Equivalent Currents), the a...A novel modified four path method (FPM) is presented for calculating coupling field of super-low altitude aircraft target. Based on the hybrid method PO + MEC (Physical Optics and Method of Equivalent Currents), the antenna radiation pattern is introduced to consider the multipath interference from side lobe of seeker. The modified FPM is used to calculate the coupling field from super-low altitude aircraft target above different terrestrial environments. The curves of scattering coefficient are analyzed. The influences of height of target, root mean square (RMS), and incident angle on coupling field characteristics are discussed. The simulation results can be used for reference in detection for super-low altitude target and optimization for radar system.展开更多
The Super-Low Frequency （SLF） electromag- netic prospecting technique, adopted as a non-imaging remote sensing tool for depth sounding, is systematically proposed for subsurface geological survey. In this paper, we ...The Super-Low Frequency （SLF） electromag- netic prospecting technique, adopted as a non-imaging remote sensing tool for depth sounding, is systematically proposed for subsurface geological survey. In this paper, we propose and theoretically illustrate natural source magnetic amplitudes as SLF responses for the first step. In order to directly calculate multi-dimensional theoretical SLF responses, modeling algorithms were developed and evaluated using the finite difference method. The theore- tical results of three-dimensional （3-D） models show that the average normalized SLF magnetic amplitude responses were numerically stable and appropriate for practical interpretation. To explore the depth resolution, three-layer models were configured. The modeling results prove that the SLF technique is more sensitive to conductive objective layers than high resistive ones, with the SLF responses of conductive objective layers obviously show- ing uprising amplitudes in the low frequency range. Afterwards, we proposed an improved Frequency-Depth transformation based on Bostick inversion to realize the depth sounding by empirically adjusting two parameters. The SLF technique has already been successfully applied in geothermal exploration and coalbed methane （CBM） reservoir interpretation, which demonstrates that the proposed methodology is effective in revealing low resistive distributions. Furthermore, it siginificantly contributes to reservoir identification with electromagnetic radiation anomaly extraction. Meanwhile, the SLF inter- pretation results are in accordance with dynamic production status of CBM reservoirs, which means it could provide an economical, convenient and promising method for exploring and monitoring subsurface geo-objects.展开更多
在低光环境下,人脸图像增强是许多任务的重要恢复方法。然而,现有的低光环境下人脸超分辨率方法通常依赖于低光增强和超分算法的序列建模。遗憾的是,由于优化目标之间的差异,使用这种方法来增强人脸图像很容易导致伪影或噪声。为了应对...在低光环境下,人脸图像增强是许多任务的重要恢复方法。然而,现有的低光环境下人脸超分辨率方法通常依赖于低光增强和超分算法的序列建模。遗憾的是,由于优化目标之间的差异,使用这种方法来增强人脸图像很容易导致伪影或噪声。为了应对这一挑战,本文提出了一个端到端的低光人脸图像超分辨率网络(low-light face super resolution network,LFSRNet)。该网络由浅层特征提取、深层特征提取和特征过滤上采样3个模块组成。首先浅层特征模块将输入的低光、低分辨率人脸图像映射到特征空间。随后,深度特征提取模块对其进行亮度校正并细化结构。最后,特征过滤上采样模块处理提取到的特征并重建人脸图像。此外,为了更好地重建丢失的面部细节本文还设计了一个损失函数faceMaskLoss。大量实验证明了所提模型的有效性。展开更多
吸气式电推进(air-breathing electric propulsion,ABEP)系统使用超低轨道大气作为工质,可突破推进剂携带量对卫星使用寿命的限制瓶颈,是超低轨卫星实现长期驻留的关键技术途径之一.本文采用直接模拟蒙特卡罗(direct simulation Monte C...吸气式电推进(air-breathing electric propulsion,ABEP)系统使用超低轨道大气作为工质,可突破推进剂携带量对卫星使用寿命的限制瓶颈,是超低轨卫星实现长期驻留的关键技术途径之一.本文采用直接模拟蒙特卡罗(direct simulation Monte Carlo,DSMC)计算方法,对二维的ABEP进气道模型进行模拟.设定壁面碰撞模型为完全漫反射,在进气道的进口直径保持定值的前提下,改变进气道的长纵比、出口锥角、栅格长度和栅格层数,以分别探究这些影响因素单一作用下的进气道性能变化规律.在单一影响规律的前提下,利用遗传算法进行多目标优化,得到符合设计要求的高性能进气道设计参数,通过权重分配实现了典型高度下进气道设计中收集效率与压缩比的最优解.本研究对大气收集器产品的工程化应用具有指导意义.展开更多
文摘A novel modified four path method (FPM) is presented for calculating coupling field of super-low altitude aircraft target. Based on the hybrid method PO + MEC (Physical Optics and Method of Equivalent Currents), the antenna radiation pattern is introduced to consider the multipath interference from side lobe of seeker. The modified FPM is used to calculate the coupling field from super-low altitude aircraft target above different terrestrial environments. The curves of scattering coefficient are analyzed. The influences of height of target, root mean square (RMS), and incident angle on coupling field characteristics are discussed. The simulation results can be used for reference in detection for super-low altitude target and optimization for radar system.
文摘The Super-Low Frequency （SLF） electromag- netic prospecting technique, adopted as a non-imaging remote sensing tool for depth sounding, is systematically proposed for subsurface geological survey. In this paper, we propose and theoretically illustrate natural source magnetic amplitudes as SLF responses for the first step. In order to directly calculate multi-dimensional theoretical SLF responses, modeling algorithms were developed and evaluated using the finite difference method. The theore- tical results of three-dimensional （3-D） models show that the average normalized SLF magnetic amplitude responses were numerically stable and appropriate for practical interpretation. To explore the depth resolution, three-layer models were configured. The modeling results prove that the SLF technique is more sensitive to conductive objective layers than high resistive ones, with the SLF responses of conductive objective layers obviously show- ing uprising amplitudes in the low frequency range. Afterwards, we proposed an improved Frequency-Depth transformation based on Bostick inversion to realize the depth sounding by empirically adjusting two parameters. The SLF technique has already been successfully applied in geothermal exploration and coalbed methane （CBM） reservoir interpretation, which demonstrates that the proposed methodology is effective in revealing low resistive distributions. Furthermore, it siginificantly contributes to reservoir identification with electromagnetic radiation anomaly extraction. Meanwhile, the SLF inter- pretation results are in accordance with dynamic production status of CBM reservoirs, which means it could provide an economical, convenient and promising method for exploring and monitoring subsurface geo-objects.
文摘在低光环境下,人脸图像增强是许多任务的重要恢复方法。然而,现有的低光环境下人脸超分辨率方法通常依赖于低光增强和超分算法的序列建模。遗憾的是,由于优化目标之间的差异,使用这种方法来增强人脸图像很容易导致伪影或噪声。为了应对这一挑战,本文提出了一个端到端的低光人脸图像超分辨率网络(low-light face super resolution network,LFSRNet)。该网络由浅层特征提取、深层特征提取和特征过滤上采样3个模块组成。首先浅层特征模块将输入的低光、低分辨率人脸图像映射到特征空间。随后,深度特征提取模块对其进行亮度校正并细化结构。最后,特征过滤上采样模块处理提取到的特征并重建人脸图像。此外,为了更好地重建丢失的面部细节本文还设计了一个损失函数faceMaskLoss。大量实验证明了所提模型的有效性。
文摘吸气式电推进(air-breathing electric propulsion,ABEP)系统使用超低轨道大气作为工质,可突破推进剂携带量对卫星使用寿命的限制瓶颈,是超低轨卫星实现长期驻留的关键技术途径之一.本文采用直接模拟蒙特卡罗(direct simulation Monte Carlo,DSMC)计算方法,对二维的ABEP进气道模型进行模拟.设定壁面碰撞模型为完全漫反射,在进气道的进口直径保持定值的前提下,改变进气道的长纵比、出口锥角、栅格长度和栅格层数,以分别探究这些影响因素单一作用下的进气道性能变化规律.在单一影响规律的前提下,利用遗传算法进行多目标优化,得到符合设计要求的高性能进气道设计参数,通过权重分配实现了典型高度下进气道设计中收集效率与压缩比的最优解.本研究对大气收集器产品的工程化应用具有指导意义.
