Author Affiliations
Abstract
1 College of Science, National University of Defense Technology, Changsha 410073, People’s Republic of China
2 Hunan Key Laboratory of Extreme Matter and Applications, National University of Defense Technology, Changsha 410073, People’s Republic of China
3 Applied Mechanics Laboratory, Department of Engineering Mechanics, School of Aerospace, Tsinghua University, Beijing 100084, People’s Republic of China
4 Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, People’s Republic of China
5 Department of Material Science and Technology, Shanghai Jiao Tong University, Shanghai, People’s Republic of China
Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extreme conditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50 is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physical properties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change are successfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relatively insensitive to the strain rate when ranges from 7.5 × 108 to 2 × 109/s, which are values reachable in QIC experiments, with a magnitude of the order of 10-2kB/atom per GPa. However, when is extremely high (), a notable increase in entropy production rate with is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated that entropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase in configurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamental relation between microstructure evolution and plastic dissipation.
Matter and Radiation at Extremes
2024, 9(2): 027802
江西师范大学地理与环境学院，江西 南昌 330022
针对历史栅格地图、遥感影像和LiDAR点云数据中提取的建筑物轮廓存在锯齿、边界不规则和位置不准确等问题，提出了一种普适的建筑物轮廓优化方法。首先，利用改进的Douglas-Peucker算法对轮廓进行初步简化，其中采用凸包法获取轮廓线的起止点并使用垂距法获取轮廓简化的距离阈值。其次，利用最小二乘法进行直线拟合和直线求交，对轮廓进一步优化。再其次，对定义的特征边和特征角进行规则化处理。然后，根据建筑物主方向与每条轮廓边的夹角关系进行直角化处理。最后，设计了一种基于最大面积重叠度的方法实现轮廓位置的精准化。利用多源建筑物轮廓矢量数据进行了实验，结果表明所提方法有效，且与当前主流方法相比，具有更高的建筑物轮廓精度和较强的普适性。
遥感 建筑物轮廓优化 轮廓简化 规则化 位置精准化 光学学报
2023, 43(12): 1228012
中国原子能科学研究院 核安全研究所北京 102413
康普顿成像技术是近年新兴的一种辐射热点定位技术，其无需准直，视野广，效率高，应用前景广阔。针对核设施热点定位需求，采用两块像素型碲锌镉（Cadmium Zinc Telluride，CZT）探测器，基于专用读出芯片（Application Specific Integrated Circuit，ASIC）的读出电子学系统，结合列表模式期望最大化极大似然（List-mode Maximum Likelihood Expectation Maximization，LM-MLEM）图像重建算法研制了一套双层分离式康普顿相机。采用137Cs点源对该系统的成像性能开展了实验测试，并对探测器层间距、吸收层面积等成像性能影响参数展开了优化研究，最后通过移动探测器的测量位置实现了对放射源的远场三维成像功能测试。该系统优势在于其结构可调性，探测器成本低，读出电子学相对简单，成像视野范围宽于传统γ相机，测试结果表明：系统的能量分辨率约为3%（FWHM@662 keV），能确定5 m外的137Cs点源三维位置信息，优化后的系统前锥角θ和侧向方位角φ的角分辨率约为10°。
康普顿相机 热点成像 碲锌镉探测器 Compton camera Hot spot imaging CdZnTe detector
Author Affiliations
Abstract
1 Inner Mongolia Key Laboratory of Ferroelectric-Related New Energy Materials and Devices, School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou, Inner Mongolia 014010, P. R. China
2 Department of Chemical Engineering, Ordos Institute of Technology, Ordos, Inner Mongolia 017000, P. R. China
3 Frontier Institute of Science and Technology and State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong University, Xi’an, Shaanxi 710049, P. R. China
Ferroelectric materials are considered to be the most competitive energy storage materials for applications in pulsed power electronics due to excellent charge–discharge properties. However, the low energy storage density is the primary problem limiting their practical application. In this study, (1)NaBiTiO3 – SrLaTiO3[(1)NBT–SLT] ferroelectric ceramics are found to exhibit excellent energy storage performances through a synergistic strategy. As the SLT concentration increases, the relaxation characteristic increases significantly and the breakdown strength increases dramatically from 150 kV/cm to 220 kV/cm. The recoverable energy storage density of the 0.55NBT–0.45SLT ceramic is 2.86 J/cm3 with an energy storage efficiency of 88% under an electric field of 220 kV/cm. Furthermore, the ceramic with = 0.45 mol exhibited excellent energy storage stability in the ranges of 20–180C (temperature) and 1–125 Hz (frequency). These excellent properties demonstrate the potential of (1)NBT–SLT ceramics when used as dielectric capacitors in pulsed power systems.Ferroelectric materials are considered to be the most competitive energy storage materials for applications in pulsed power electronics due to excellent charge–discharge properties. However, the low energy storage density is the primary problem limiting their practical application. In this study, (1)NaBiTiO3 – SrLaTiO3[(1)NBT–SLT] ferroelectric ceramics are found to exhibit excellent energy storage performances through a synergistic strategy. As the SLT concentration increases, the relaxation characteristic increases significantly and the breakdown strength increases dramatically from 150 kV/cm to 220 kV/cm. The recoverable energy storage density of the 0.55NBT–0.45SLT ceramic is 2.86 J/cm3 with an energy storage efficiency of 88% under an electric field of 220 kV/cm. Furthermore, the ceramic with = 0.45 mol exhibited excellent energy storage stability in the ranges of 20–180C (temperature) and 1–125 Hz (frequency). These excellent properties demonstrate the potential of (1)NBT–SLT ceramics when used as dielectric capacitors in pulsed power systems.
Energy storage ferroelectric lead-free ceramics dielectric microstructure Journal of Advanced Dielectrics
2023, 13(1): 2242003
1 海军工程大学电气工程学院，湖北 武汉 430033
2 92853部队四分队，辽宁 葫芦岛 125106
提升数据处理能力是实现光纤电流传感器（FOCS）在微弱电流检测领域中应用的重要支撑。针对独立成分分析（ICA）算法对信源数量的要求和变分模态分解（VMD）对冲击噪声处理能力不足的问题，采用优化参数的变分模态分解与独立成分分析联合算法（OVMD-ICA算法），提升微弱电流检测能力。首先，在分析全光纤电流传感器输出信号的特征和噪声特性的基础上，以能量谱熵为目标函数，采用捕食者算法（HPO算法）获取模态参数K和二次惩罚因子α，完成变分模态分解。然后，通过设置相关系数阈值，对各模态函数分类并构建虚拟通道，以满足ICA对信源数量的要求，并采用FastICA算法实现盲源分离。最后，通过对比实验确定了该方法的有效性，发现采用所提方法能够实现3 mA微弱电流的识别检测。
信号处理 全光纤电流传感器 微弱电流测量 变分模态分解 独立成分分析 捕食者算法
1 海军工程大学电气工程学院，湖北 武汉 430033
2 92853部队，辽宁 葫芦岛 125106
3 国防科技大学信息通信学院，湖北 武汉 430033
采用全光纤电流传感器实现微弱电流检测，可以拓展光纤传感技术在微弱磁场检测领域的应用。在分析全光纤微电流传感器的基本原理和主要光路结构的基础上，从增加光路循环次数、提高传感光纤性能、降低系统噪声三个方面，综述了全光纤微电流传感的最新研究成果及存在问题，并展望了全光纤微电流传感器未来发展趋势。
传感器 光纤传感 全光纤电流传感器 微电流测量 灵敏度 激光与光电子学进展
2022, 59(17): 1700005
1 武汉大学遥感信息工程学院, 湖北 武汉 430079
2 武汉市国土资源和规划信息中心, 湖北 武汉 430014
3 江西师范大学地理与环境学院, 江西 南昌 330022
为了解决缺乏明显特征点给基础矩阵计算带来的难题，针对水平直线与垂直直线所特有的极几何关系，提出了一种可以联合这两种直线特征的基础矩阵计算方法。首先以相机方位元素、相对姿态为基础矩阵的参数化要素，构建基于水平直线与垂直直线的等量方程式，然后以特征直线作为RANSAC算法的内点筛选出特征点的最优子集，再结合M-estimators算法确定各个要素的权值，最后构建统一的平差模型进行计算。模拟数据与真实图像的对比实验结果表明，该方法切实可行，能够减少传统基础矩阵计算方法对特征点的依赖，特征直线的引入也能在一定程度上提高计算结果的精确度与稳定性。
机器视觉 基础矩阵 对极几何 直线特征 稳健性 光学学报
2013, 33(10): 1015003
淮阴工学院机械工程学院江苏省数字化制造技术重点建设实验室, 江苏 淮安 22300
以ABAQUS和MSC.fatigue软件为平台, 建立了激光喷丸强化前后试样疲劳寿命及薄弱位置预测的有限元分析模型。为研究材料强度对激光喷丸强化效果的影响, 以AZ31B和ZK60两种不同强度变形镁合金为对象, 对激光喷丸强化后的残余应力和塑性变形进行了分析, 并预测了喷丸前后的疲劳寿命, 两种材料的疲劳寿命增益分别为112.04%和181.2%。结果表明, 高强度材料激光喷丸强化效果优于低强度材料。
激光喷丸强化 数值模拟 变形镁合金 疲劳寿命 残余压应力 laser shot peening numerical simulation wrought magnesium alloy fatigue life residual stress
1 淮阴工学院机械工程学院江苏省数字化制造技术重点建设实验室, 江苏 淮安 223003
2 江苏大学机械工程学院, 江苏 镇江 212013
为研究铜合金薄板的脉冲激光弯曲成形工艺, 基于 Taguchi方法对单道单次扫描成形 V形件的工艺进行了正交试验设计。以弯曲角为响应目标, 以望大特性的信噪比评估弯曲角的品质特性, 得到了最佳工艺参数组合: 激光功率 P为 24W, 扫描速率淄为 500 mm/min, 离焦量 L为 4 mm, 实验测得弯曲角为 1.362毅。在成形 V形件的实验基础上采用多道多次扫描方式进行了预定曲率半径的圆弧曲面成形实验。依据扫描次数与弯曲角之间的关系规划了扫描路径和扫描次数, 实验结果与预设目标有较好的一致性; 半路径扫描比全路径扫描更能得到理想的变形效果和表面质量。实验中发现, 因铜合金薄板热传导率高、厚度小, 激光扫描时上下表面的温度梯度不太明显, 成形机理以屈曲机理为主。
激光技术 脉冲激光弯曲成形 Taguchi方法 铜合金 工艺参数优化 laser technique pulsed laser bending Taguchi method copper alloy parameter optimization
1 淮阴工学院机械工程学院， 江苏省数字化制造技术重点建设实验室， 江苏 淮安 223003
2 江苏大学机械工程学院， 江苏 镇江 212013
为研究激光喷丸对高强度变形镁合金ZK60疲劳性能的影响机理，使之适应交变应力结构件的工作需要，进行了激光喷丸强化表面改性和拉伸疲劳性能实验。实验结果表明，在激光喷丸强化区域获得有益的残余压应力，产生硬化效应，表面塑性变形的微小区域，变形轮廓曲线波动范围较基体小，增加喷丸次数可增强激光喷丸的强化效应。经3次激光喷丸后，中心孔疲劳试样的平均疲劳寿命由未喷丸试样的78023次提高到125641次，寿命增益达61%。从断口来看，激光喷丸强化主要是改变了裂纹源萌生位置，延缓了裂纹扩展速率，对瞬断区无明显影响。激光喷丸强化为镁合金的抗疲劳制造提供了新的途径。
激光技术 激光喷丸强化 疲劳寿命 变形镁合金 残余压应力 激光与光电子学进展
2012, 49(8): 081403
