Author Affiliations
Abstract
1 School of Electronics and Information Engineering, Hunan University of Science and Engineering, Yongzhou 425199, China
2 BNP Paribas, 787 Seventh Avenue, New York 10019, U.S.A.
3 College of Communication and Information Engineering, Chongqing University of Posts and Telecommunications, Chongqing 400065, China
4 Key Laboratory of Granular Computing, Minnan Normal University, Zhangzhou 363000, China
In view of the problems that the encoding complexity of quasi-cyclic low-density parity-check (QC-LDPC) codes is high and the minimum distance is not large enough which leads to the degradation of the error-correction performance, the new irregular type-II QC-LDPC codes based on perfect cyclic difference sets (CDSs) are constructed. The parity check matrices of these type-II QC-LDPC codes consist of the zero matrices with weight of 0, the circulant permutation matrices (CPMs) with weight of 1 and the circulant matrices with weight of 2 (W2CMs). The introduction of W2CMs in parity check matrices makes it possible to achieve the larger minimum distance which can improve the error- correction performance of the codes. The Tanner graphs of these codes have no girth-4, thus they have the excellent decoding convergence characteristics. In addition, because the parity check matrices have the quasi-dual diagonal structure, the fast encoding algorithm can reduce the encoding complexity effectively. Simulation results show that the new type-II QC-LDPC codes can achieve a more excellent error-correction performance and have no error floor phenomenon over the additive white Gaussian noise (AWGN) channel with sum-product algorithm (SPA) iterative decoding.
光电子快报（英文版）
2017, 13(5): 358
中国科学院 上海光学精密机械研究所 高功率单元技术研发中心, 上海 201800
研究了惯性约束聚变高功率激光驱动器使用的脉冲氙灯灯管(复合石英灯管和掺铈石英灯管)的光谱性能和抗冲击性能。分别对新复合石英灯管、新掺铈石英灯管、放电14 000发次的复合石英灯管、放电14 000发次的掺铈石英灯管进行了光谱透过率测试和实验对比。结果显示: 复合石英灯管和掺铈石英灯管光谱性能都达到了高功率脉冲氙灯灯管的光谱指标, 但掺铈石英灯管光谱透过率比复合石英灯管高约1%。对复合石英灯管和掺铈石英灯管进行了成分测试以验证其光谱性能。结果表明: 除铈以外, 掺铈石英灯管的其他金属杂质含量均低于复合石英灯管, 认为其是掺铈石英灯管光谱性能优于复合石英灯管的一个原因。模拟了氙灯的放电运行, 分别对复合石英灯管和掺铈石英灯管进行了动态抗冲击性能测试。结果表明, 复合石英灯管的抗冲击性能较掺铈石英灯管高约6%。
惯性约束聚变 高功率脉冲氙灯 复合石英灯管 掺铈石英灯管 透过率 抗冲击性能 Inertial confinement fusion high power pulsed xenon lamp composite quartz tube cerium doped quartz tude transmissivity Shock resistance 光学 精密工程
2016, 24(12): 2988
1 中国科学院上海光学精密机械研究所, 上海 201800
2 中国科学院大学, 北京 100049
为了研究储能电容初始电压、电极间距、充气压及灯管内径等条件对脉冲氙灯电流脉冲和发光脉冲的影响, 在电极间距100~300 mm、充气压13.33~53.32 kPa、灯管内径6~12 mm、储能电容初始电压1.75~4.25 kV的条件下, 分别测量了脉冲氙灯的电流脉冲和发光脉冲的变化状况。测量得到脉冲氙灯的电流脉冲宽度和发光脉冲宽度均在15~45 μs之间。对比发现: 储能电容初始电压较高有助于获得高峰值、窄脉宽且滞后时间短的电流脉冲;具有较高充气压或较长电极间距的脉冲氙灯其电流脉冲与发光脉冲的峰值较小、脉冲宽度较大, 且发光脉冲滞后时间较长;较粗灯管内径虽然可以增加电流脉冲的峰值, 但电流脉冲的宽度被增宽, 发光脉冲峰值减小, 发光脉冲宽度展宽, 且延长了发光脉冲的滞后时间.
图像处理 高速摄影 脉冲氙灯 电流脉冲 光脉冲 脉冲宽度 滞后时间 Image processing High speed photography Flash lamps Current light Light current Pulse width Lag time
中国科学院上海光学精密机械研究所，上海 201800
利用转镜式高速摄影机分幅摄影技术，对脉冲氙灯放电中的沟道扩展和熄灭过程进行了摄影和分析.放电时沟道扩展速度很快，呈树枝状，沟道熄灭过程长于扩展过程，且呈斑状.同时研究了预电离放电对沟道扩展和熄灭过程的影响，当预电离存在时，脉冲氙灯放电的沟道扩展的时间要长.结果表明，预电离有利于放电沟道的形成，提高氙灯的发光效率，且有助于减小主放电能量对管壁材料的冲击.
脉冲氙灯 沟道 高速摄影 预电离 Pulsed xenon lamp Expansion of channel High speed photography Pre-ionization
