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自旋尾翼弹头的双基地微多普勒研究 总被引:1,自引:0,他引:1
微动特征是弹道中段目标雷达识别的有效特征之一。针对基于自旋尾翼弹头的双基地微多普勒的自旋和结构参数估计问题,该文首先建立了自旋尾翼弹头双基地散射中心的微多普勒模型,然后利用FEKO计算了尾翼弹头的双基地散射系数,通过对散射系数序列的时频分析,验证了模型的正确性,同时总结了自旋尾翼弹头的双基地微多普勒特性,再分析了估计自旋和结构参数的可行性,最后,由于闪烁效应导致Hough变换已不能有效估计参数,该文提出了利用闪烁效应估计参数的新思路。 相似文献
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Jaewoo Choi Nagarajan Balaji Vinh Ai Dao Cheolmin Park Seunghwan Lee Jungmo Kim Minkyu Ju Hoongjoo Lee Youn-Jung Lee Junsin Yi 《Journal of Electronic Materials》2014,43(9):3191-3195
The effect of hydrogen capping of SiN(Si-rich)/SiN(N-rich) stacks for n-type c-Si solar cells was investigated. Use of a passivation layer consisting of Si-rich SiN with a refractive index (n) of 2.7 and N-rich SiN with a refractive index of 2.1 improved the thermal stability. A single SiN passivation layer with a refractive index of 2.05 resulted in an initial lifetime of 200 μs whereas the layer with a refractive index of 2.7 resulted in a high initial lifetime of 2 ms, but the layer degraded rapidly after firing. A stacked passivation layer with refractive indices of 2.1 and 2.7 had a stable lifetime of 1.5 ms with an implied open-circuit voltage (iV oc) of 720 mV after firing. The thermally stable passivation mechanism with changing amounts of Si–N and Si–H bonding was analyzed by Fourier-transform infrared (FTIR) spectroscopy. Incorporation of the SiN x stack layer (2.7 + 2.1) into the passivated rear of n-type Cz silicon screen-printed solar cells resulted in energy conversion efficiency of 19.69%. Improved internal quantum efficiency in the long-wavelength range above 900 nm, with V oc of 630 mV, is mainly because of superior passivation of the rear surface compared with conventional solar cells. 相似文献
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Experiment and analysis of the effect of fine tracking system on the unstable platform in laser communication 总被引:3,自引:0,他引:3
Atmospheric turbulence and platform vibration in the space optical communication can cause the offset and jitter of beam, which further result in the fluctuations of received optical power. To resist this effect, a communication system with fine tracking systems in the receiver and transmitter is designed. The system is used in the experiment of laser communication between high-rise buildings over a distance of 3.5 km. After adding a vibration source to the transmitter, the centroids of spots captured by the camera of the transmitter and the optical power of receiver are recorded for the purpose of analysis. When the vibration source works at the designated frequency, a peak appears at the corresponding frequency in the spectrum of the spot centroids and the optical power of receiver. Then the peak disappears once the fine tracking system begins to work. Compared with the condition without the fine tracking system, the minimum value of the optical power of receiver is increased by 5 dB, and the standard deviation is decreased by 30%. 相似文献
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Traditional rate-distortion (R-D) model-based Lagrange multiplier \(\lambda \) that is employed by H.264/SVC does not consider the inter-layer correlation. This paper presents new R-D models and \(\lambda \) which exploits inter-layer correlation for coding modes that perform residual prediction in H.264/SVC medium-grain quality scalability (MGS) coding. We have observed that in MGS coding, the prediction error of modes performing residual prediction is approximately equal to the reconstruction error of the corresponding macroblock in the reference layer. Based on that observation, we investigate the distribution \(f_r \) of transformed residual prediction error signals and prove that \(f_r \) is related to the quantization step of the corresponding macroblock in the reference layer. In such a case, both the conventional \(\lambda \) and the R-D models in the literature that are derived independently of inter layers are not much fit for residual prediction modes any more. Thus, we build more appropriate R-D models depending on the derived distribution and develop a new \(\lambda \) from the R-D models. Experimental results show that when residual prediction is enabled, the proposed scheme by using the new Lagrange multiplier achieves an average PSNR gain of 0.47 dB and up to more than 1 dB over the scheme using the conventional Lagrange multiplier. 相似文献
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