辽宁工程技术大学 电子与信息工程学院,辽宁 葫芦岛 125105
针对现有图像重定向方法视觉效果差和处理速度慢的问题,提出一种基于主成分分析法和分块的内容感知图像重定向方法。首先,利用主成分分析法融合梯度图和显著图来提取更加丰富的图像特征,避免主体信息失真;其次,相邻裁缝线由均值代替,避免像素不连贯;最后,根据能量图中列能量值的大小将图像分为显著区域和非显著区域,并行缩放分块,更加注重图像特征并提高运行效率。在MIT RetargetMe、DUT-OMRON和NJU2000数据集上进行实验分析,以主观感受和客观因子运行时间、SIFT-flow作为评价指标,与几种常用算法对比。实验结果表明,该方法保证了图像主体信息的完整性,平均运行时间为线裁剪算法的1/3。本文提出的方法不仅具有较优的视觉效果,而且可降低运算量。
主成分分析法 能量图 分块 裁缝线 缩放 principal component analysis energy map blocking seams scaling
1 中国科学院力学研究所流固耦合系统力学重点实验室,北京 100190
2 中国科学院力学研究所空天飞行高温气动国家重点实验室,北京 100190
3 中国科学院大学工程科学学院,北京 100049
高速气流作用下激光辐照结构诱导的热-力响应相似关系,因涉及多物理场之间的强耦合而非常复杂。笔者采用近似等效方法,将切向气流的作用等效为金属平板结构的力载荷和热载荷边界条件,建立了该耦合问题的无量纲控制方程,并结合主控因素分析,推导出了适用于高速气流与激光联合作用下的金属平板热-力响应特性的相似关系与尺度律。采用高速气流下强激光辐照金属平板的流-热-固多场耦合数值算例对该尺度律进行考核验证,结果表明:不同缩比率及不同马赫数条件下,满足该相似关系的缩比模型与原模型之间的热-力响应误差均在1%之内。本研究为高速气流条件下激光辐照缩比模型近似等效试验的开展奠定了理论基础。
激光技术 尺度律 方程分析法 金属平板 多场耦合 热-力响应 中国激光
2024, 51(12): 1202103
语音感知是无人系统的重要组成部分, 已有的工作大多集中于单个智能体的语音感知, 受噪声、混响等因素的影响, 性能存在上限。因此研究多智能体语音感知, 通过多智能体自组织、相互协作, 提高感知性能非常必要。假设每个智能体输出一个通道的语音流条件下, 本文提出一种多智能体自组织语音系统, 旨在综合利用所有通道提高感知性能; 并进一步以语音识别为例, 提出能处理大规模多智能体语音识别的通道选择方法。基于 Sparsemax算子的端到端语音识别流注意机制, 将带噪通道权重置零, 使流注意力具备通道选择能力, 但 Sparsemax算子会将过多通道权重置零。本文提出 Scaling Sparsemax算子, 只将带噪较强的通道权重置零; 同时提出了多层流注意力结构, 有效降低了计算复杂度。在 30个智能体的无人系统环境下, 基于 conformer架构的识别系统实验结果表明, 在通道数失配的测试环境下, 提出的 Scaling Sparsemax在仿真数据集上的文字差错率 (WER)相比 Softmax降低 30%以上, 在半真实数据集上降低 20%以上。
多智能体语音识别 通道选择 注意力 Scaling Sparsemax算子 multi-agent speech recognition channel selection attention Scaling Sparsemax 太赫兹科学与电子信息学报
2023, 21(9): 1163
Keystone变换(KT)是一种经典的雷达目标距离走动校正工具。针对现有实现方法计算复杂度高、抗噪效能不够理想的问题, 提出基于快速傅里叶变换(FFT)插值的KT实现方法, 先将慢时间回波转换至频域, 再通过频域补零、快速傅里叶逆变换(IFFT)、时域抽取等操作, 计算尺度化回波, 完成KT去耦合。仿真结果表明, 所提方法抗噪效能优于现有几种KT实现方法, 且计算复杂度明显更低。
Keystone变换 FFT插值 时间尺度 频域补零 Keystone Transform (KT) FFT interpolation time-scaling zero padding in frequency domain
季华实验室光电科学与技术研究部,广东 佛山 528200
针对角谱法在远距离衍射计算时的失真问题,分析其原因为有效频谱成分减少和频谱混叠造成的计算误差。结合带限角谱法的频域采样特性,对缩放角谱法进行了改进,并应用于大尺寸方形长焦透镜、圆形轴锥透镜和平顶光束衍射光学元件的衍射场分布计算。结果表明,相较于原始的带限角谱法和缩放角谱法,改进算法获得的衍射场分辨率更高且不存在边缘失真现象,在大尺寸口径、长距离、小衍射场精确计算方面具有重要的应用潜力。
衍射 角谱法 失真 带限角谱法 缩放角谱法 激光与光电子学进展
2023, 60(23): 2307001
Author Affiliations
Abstract
1 State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
2 Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
Colloidal CdSe quantum dots (QDs) are promising materials for solar cells because of their simple preparation process and compatibility with flexible substrates. The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes. However, the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle. This article presents a novel explanation that reconciles this controversy. Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window. Further, we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states. Each of the contradictory size-dependent patterns reflects this trend in a specific size range. As the optical band gap increases, the radiative lifetime decreases in larger QDs, increases in smaller QDs, and is weakly dependent on size in the intermediate energy region. This study addresses the inconsistencies in the scaling law of the exciton lifetime and gives a unified interpretation over a widened framework. Moreover, it provides valuable guidance for carrier separation in the thin film solar cell of CdSe QDs.Colloidal CdSe quantum dots (QDs) are promising materials for solar cells because of their simple preparation process and compatibility with flexible substrates. The QD radiative recombination lifetime has attracted enormous attention as it affects the probability of photogenerated charges leaving the QDs and being collected at the battery electrodes. However, the scaling law for the exciton radiative lifetime in CdSe QDs is still a puzzle. This article presents a novel explanation that reconciles this controversy. Our calculations agree with the experimental measurements of all three divergent trends in a broadened energy window. Further, we proved that the exciton radiative lifetime is a consequence of the thermal average of decays for all thermally accessible exciton states. Each of the contradictory size-dependent patterns reflects this trend in a specific size range. As the optical band gap increases, the radiative lifetime decreases in larger QDs, increases in smaller QDs, and is weakly dependent on size in the intermediate energy region. This study addresses the inconsistencies in the scaling law of the exciton lifetime and gives a unified interpretation over a widened framework. Moreover, it provides valuable guidance for carrier separation in the thin film solar cell of CdSe QDs.
solar cells CdSe quantum dot radiative lifetime scaling law optical band gap exciton fine structure room temperature Journal of Semiconductors
2023, 44(3): 032702