一类时滞分数阶计算机病毒模型的稳定性研究

本文研究一类改进的时滞分数阶计算机病毒模型正平衡点的稳定性问题.利用线性化方法和拉普拉斯变换获得模型对应的线性化系统的特征方程,通过讨论特征方程的根以及横截条件研究时滞和正平衡点稳定性之间的关系,推导了Hopf分支出现时时滞临界值的计算公式,并选择恰当的系统参数进行数值模拟以验证理论分析的合理性.     

Gradient Learning under Tilted Empirical Risk Minimization

Gradient Learning (GL), aiming to estimate the gradient of target function, has attracted much attention in variable selection problems due to its mild structure requirements and wide applicability. Despite rapid progress, the majority of the existing GL works are based on the empirical risk minimization (ERM) principle, which may face the degraded performance under complex data environment, e.g., non-Gaussian noise. To alleviate this sensitiveness, we propose a new GL model with the help of the tilted ERM criterion, and establish its theoretical support from the function approximation viewpoint. Specifically, the operator approximation technique plays the crucial role in our analysis. To solve the proposed learning objective, a gradient descent method is proposed, and the convergence analysis is provided. Finally, simulated experimental results validate the effectiveness of our approach when the input variables are correlated.     

扩散场扇扫重建格林函数实现近表盲区缺陷检测

针对结构近表盲区缺陷检测难题,发展了一种扩散声场扇扫重建格林函数的超声检测方法.在对扩散场扇扫重建格林函数理论分析的基础上,通过5 MHz超声相控阵探头对铝块近表盲区缺陷进行了检测实验并对影响成像结果的延时时间、时间窗宽和扫查方式进行了分析.结果显示,该方法可以有效检测铝块近表1.5?3 mm的盲区缺陷;扇形扫查方式的...     

直接进样毛细管气相色谱法测定水中乙醛和丙烯醛

建立气相色谱法测定水中乙醛和丙烯醛的方法.直接进样用大口径填充毛细管柱进行分离分析,分离度好,灵敏度高,水中乙醛和丙烯醛的栓出浓度分别为0.02mg/L、0.01mg/L;样品加标回收率乙醛为102%～103%,丙烯醛为94.8%～!96.8%;6次平行测定结果的相对标准差不大于5.8%(n=6).该方法简便、快速、准确、重现性好.适合各种水中乙醛和丙烯醛的同时测定     

An Implantable Fiber Biosupercapacitor with High Power Density by Multi-Strand Twisting Functionalized Fibers

Biosupercapacitors (BSCs) that can harvest and store chemical energy show great promise for power delivery of biological applications. However, low power density still limits their applications, especially as miniaturized implants. Here, we report an implantable fiber BSC with maximal power density of 22.6 mW cm⁻², superior to the previous reports. The fiber BSC was fabricated by integrating anode and cathode fibers of biofuel cell with supercapacitor fibers through multi-strand twisting. This twisting structure endowed many channels inside and high electrochemical active area for efficient mass diffusion and charge transfer among different fibers, benefiting high power output. The obtained thin and flexible fiber BSC operated stably under deformations and performed high biocompatibility after implantation. Eventually, the fiber BSC was implanted subcutaneously in rats and successfully realized electrical stimulation of sciatic nerve, showing promise as a power source in vivo.     

光电半导体材料辐照诱发微观缺陷的演化特性研究

基于分子动力学计算方法，运用LAMMPS程序模拟了Si, GaAs, 3C-SiC三种半导体材料中辐照引起的级联碰撞过程，并分析了晶体内微观缺陷的演化特性。模拟结果表明，级联碰撞会在晶体内部形成类似离位峰的结构，大多数空位缺陷聚集在损伤区域内部，而损伤区域外围分布的主要是间隙缺陷。通过对三种材料进行缺陷簇分析，发现Si中缺陷簇数量明显多于GaAs,缺陷簇最大尺寸达到了17个原子。此外，三种材料中的Frenkel对的数量变化过程大致相同，均呈现“上升，下降，稳定”的趋势，但3C-SiC中的缺陷数量要远小于Si和GaAs,表明3C-SiC具有更好的辐射抗性，其晶体结构在受到辐照后仍能保持相对稳定。     

基于SEM电压衬度的缺陷定位方法研究

光发射显微分析、光致电阻变化技术两种电失效定位方法在精确定位缺陷上存在局限性,为此提出了基于SEM电压衬度的联用方法用于精确定位集成电路缺陷.首先根据电特性测试进行光发射显微分析或者光致电阻变化分析,结合电路原理和版图,提出失效区域的假设,再进行电压衬度像分析,通过衬度翻转可精确和快速确定缺陷位置,最后通过FIB或者T...     

Highly Efficient Decomposition of Perfluorocarbons for over 1000 Hours via Active Site Regeneration

Tetrafluoromethane (CF₄), the simplest perfluorocarbon (PFC), has the potential to exacerbate global warming. Catalytic hydrolysis is a viable method to degrade CF₄, but fluorine poisoning severely restricts both the catalytic performance and catalyst lifetime. In this study, Ga is introduced to effectively assists the defluorination of poisoned Al active sites, leading to highly efficient CF₄ decomposition at 600 °C with a catalytic lifetime exceeding 1,000 hours. ²⁷Al and ⁷¹Ga magic-angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the introduced Ga exists as tetracoordinated Ga sites (Ga_IV), which readily dissociate water to form Ga−OH. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density function theory (DFT) calculations confirmed that Ga−OH assists the defluorination of poisoned Al active sites via a dehydration-like process. As a result, the Ga/Al₂O₃ catalyst achieved 100 % CF₄ decomposition keeping an ultra-long catalytic lifetime and outperforming reported results. This work proposes a new approach for efficient and long-term CF₄ decomposition by promoting the regeneration of active sites.     

全极化雷达抗间歇采样转发式干扰的非匹配滤波方法

间歇采样转发式干扰（ISRJ）能够在雷达接收机形成多个逼真的假目标，兼具压制和欺骗的干扰效果。为提升雷达在此干扰场景下的目标检测能力，提出了一种全极化雷达体制下的抗ISRJ非匹配滤波方法。文中以脉冲压缩后信号最小旁瓣能量输出和干扰最小积分能量输出为出发点，基于罚函数的思想建立多目标优化模型；通过帕累托参数的组合加权，将模型转化为多线性约束下最小输出积分能量的目标函数，以此设计非匹配滤波器。仿真实验表明，本文方法能够有效抑制不同样式的间歇采样转发式干扰。     

Toward Sustainable Metal-Iodine Batteries: Materials,Electrochemistry and Design Strategies

Due to the natural abundance of iodine, cost-effective, and sustainability, metal-iodine batteries are competitive for the next-generation energy storage systems with high energy density, and large power density. However, the inherent properties of iodine such as electronic insulation and shuttle behavior of soluble iodine species affect negatively rate performance, cyclability, and self-discharge behavior of metal-iodine batteries, while the dendrite growth and metal corrosion on the anode side brings potential safety hazards and inferior durability. These problems of metal-iodine system still exist and need to be solved urgently. Herein, we summarize the research progress of metal-iodine batteries in the past decades. Firstly, the classification, design strategy and reaction mechanism of iodine electrode are briefly outlined. Secondly, the current development and protection strategy of conventional metal anodes in metal-iodine batteries are highlighted, and some potential anode materials and their design strategies are proposed. Thirdly, the key electrochemical parameters of state-of-art metal-iodine batteries are compared and analyzed to solve critical issues for realizing next-generation iodine-based energy storage systems. Therefore, the aim of this review is to promote the development of metal-iodine batteries and provide guidelines for their design.