基于X射线微焦CT的燃料颗粒空间距离自动测量方法

在某燃料元件产品中燃料颗粒随机弥散分布在非金属材料中,表征燃料颗粒的分布状况进而评估产品工艺质量具有重要意义。针对该问题,对三维空间内相邻燃料颗粒的间距测量进行了研究,使用X射线微焦计算机层析成像（CT）对该类产品进行了三维扫描成像,从而得到了三维CT图像。在三维CT图像的基础上,提出了一种结合改进型空间直觉模糊C均值聚类和三维区域生长的自动算法,用于分割图像中的燃料颗粒以得到每个燃料颗粒的空间结构。然后,通过计算质心获得燃料颗粒的中心坐标,进而自动计算出相邻燃料颗粒的空间距离。通过仿真实验验证了所提算法的可行性,通过标准球实验验证了测量误差,并通过实际燃料元件测试了相邻燃料颗粒间距的自动测量,表明了所提方法对燃料颗粒间距测量的有效性。     

He+等离子体辐照下钨丝表面He通量分布的数值模拟

在He等离子体辐照条件下,钨纳米丝的形成对材料的抗辐照性能及钨丝间隙内He的分布产生显著影响。根据钨丝层中He离子的碰撞过程,建立了He⁺辐照下钨纳米丝表面He通量分布的模型。研究表明钨丝表面He通量随着深度的增大而减小,在深度3.3μm处,钨丝表面He通量是表层的百分之一。钨丝表面He通量随着注入离子通量的增加呈线性增长,但是与注入离子的能量几乎无关。钨丝层厚度越大,钨丝表面He通量越小;随着钨丝半径的增大,钨丝表层的He通量会明显增大。     

原子系统中偶极-偶极相互作用对量子存储支撑熵不确定度的调控研究

本文研究了Markovian过程和non-Markovian过程两种情况下,原子系统中偶极-偶极(D-D)相互作用和失谐量对两原子系统量子存储支撑(QMA)熵不确定度的调控作用.与Markovian过程相比,在non-Markovian过程中,由于库环境的记忆效应使得具有D-D相互作用的两原子系统QMA熵不确定度的演化行为呈现出振荡上升现象,且熵不确定度的上升趋势得到减缓,从而抑制了由系统量子噪声引起的退相干效应.此外,D-D相互作用对两原子系统QMA熵不确定度具有显著的调控能力,且D-D相互作用比失谐量的调控能力更强.     

图形衬底对多周期InGaAs量子点自组装生长的影响

量子点器件技术广泛应用于量子计算和光电器件上.成核位置的均匀性、有序性和尺寸一致性,可以有效提高光电器件性能.为了实现阵列量子点的可控性,本文采用湿法刻蚀制备图形化衬底,理论上解释了铟原子在图形化衬底上成核现象,产生有序的量子点分布特征,发现图形衬底的缺陷诱导在平台边缘和沟壑边缘成核,形成较大的量子点.在Stranski-Krastanow模式下图形衬底制备多周期量子点,发现多周期生长可以弱化台阶结构对量子点分布的限制作用.     

CH4裂解制备C2H2过程气体空芯光纤增强拉曼光谱检测研究

基于空芯反谐振光纤设计搭建了光纤增强拉曼光谱检测平台,实现了95%的激光耦合效率;提出CCD和小孔协同降噪方法,使信噪比提高约6倍;相比于未使用光纤时,信噪比提高约270倍。基于单一标准浓度气体分析,确定了用于气体定性的特征拉曼谱峰及标定模型并建立了过程气体定量分析模型,实现了CH₄裂解制备C₂H₂过程气体现场样本的同时检测分析,主要成分包含H₂、CO、CO₂、CH₄、C₂H₂、C₂H₆和C₂H₄。各气体同时最小检出限分别达到6.3、26.6、1.2、2.2、4.2、3.9、9.1μL/L·bar,各气体含量分别为560 588.51μL/L、230 678.21μL/L、33 107.65μL/L、56 086.77μL/L、77 945.56μL/L、1 307.19μL/L、1 823.55μL/L,各气体浓度与色谱仪标...     

基于混酸回流制备碳点的中和过程

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na₂CO₃, K₂CO₃, and NH₃·H₂O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na₂CO₃ showed the strongest emission under the same excitation wavelength, while that prepared with NH₃·H₂O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.     

MULTIPLE SCATTERING AND DYNAMIC STRESS ANALYSIS OF ELASTIC WAVES IN A FIBER—REINFORCED COMPOSITE WITH INTERFACES

Based on the theory of elastic dynamics, multiple scattering of elastic waves and dynamic stress concentrations in fiber-reinforced composite are studied. The analytical expressions of elastic waves in different regions are presented. The mode coefficients of elastic waves are determined in accordance with the continuous conditions of displacement and stress on the boundary of the multi-interfaces. By using the addition theorem of Hankel functions, the formula of scattered wave fields in different local coordinates are transformed into those in one local coordinate to determine the unknown coefficients and dynamic stress concentration factors (DSCFs). The influences of the distance between two inclusions, material properties and structural size on the DSCFs near the interfaces are analyzed. As examples, the numerical results of DSCFs near the interfaces for two kinds of fiber-reinforced composites are presented and discussed. The project supported by the National Natural Science Foundation of China (19972018)     

RESEARCH ON RELIABILITY GROWTH FOR SYNCHRONOUSLY DEVELOPED MULTI-SYSTEMS

IntroductionAMSAA model could evaluate reliability growth test for mono-system perfectly[1-8].Butfor multi-systems,especially for synchronously developed multi-systems,the model parametersneed to be estimated by developing some newmethods.AMSAA-BISE model…     

几种高分子材料的磨粒侵蚀机理

本文采用自行设计制造的磨粒侵蚀试验台对聚氨酯、丁苯橡胶、尼龙6和聚四氟乙烯4种高分子材料的磨粒侵蚀行为进行了试验研究,并且通过扫描电镜对试样磨损表面进行了观察分析,分别提出了这4种高分子材料磨粒侵蚀的物理模型和物理过程,阐明了它们的磨粒侵蚀机理:具有一定动能的固体颗粒对材料表层产生微切削;微观裂纹的萌生与扩展导致材料表层微观剥落;材料的力化学分解和热分解;材料表层局部塑性变形发展成塑性断裂而从表面脱落。     

工业过程混沌稳态优化控制研究

本文基于混沌现象普遍存在于各类非线性动力学系统中这一事实，针对工业过程中的混沌运动行为，给出了混沌稳态的严格定义，并对工业过程的混沌稳态优化控制问题刊物了数学描述。仿真结果表明，文中的定义以及对问题的描述是准确和恰当的；本文的工作为解决工业过程的混沌稳态优化问题提供了理论依据。