分层结构PELE侵彻多层间隔靶横向效应实验研究

为了研究不同弹丸结构和壳体材料对PELE横向效应的影响,通过实验方法,对比研究了常规结构、轴向分层结构和径向分层结构PELE(壳体材料均为钨合金)对多层间隔金属靶的毁伤效果。研究结果表明:轴向和径向分层结构PELE产生的破片数量较常规结构PELE分别提高了5.3%和84.2%,且其对第2层靶板的开孔尺寸分别提升了23%和16%,但是它们无法对后续靶板继续形成高效毁伤; 故此,将分层结构PELE的壳体材料换成钨丝/锆基非晶复合材料,做进一步实验研究。实验结果发现:钨丝/锆基非晶复合材料的分层结构PELE对第2层靶板的开孔尺寸下降约10%,但是,对第3层、第4层靶板的破坏尺寸提升分别约90%～140%和25%～30%。结果表明:钨丝/锆基非晶复合材料与分层结构PELE相结合,可提升对多层间隔靶板的高效毁伤。     

“电力电子技术”课程教学模式研究

本文分析了“电力电子技术”课程的特点及实施教学的挑战性;探索并设计了以分析方法为路线,以关键性问题为导向的教学结构;提炼了用于电力电子电路教学的两个定律、四种方法以及八个关键问题.从教学实践结果看,提出的关键问题面向工程实际且涵盖了电力电子电路的主要分析技巧与知识点,拓展了学生的分析思维,为知识再创新提供理论与实践基础.     

抗几何攻击图像水印方案

几何形变一直是各类数字水印算法较难抵抗的攻击手段。针对此问题,提出一种抗几何攻击数字图像水印算法。采用周期性的水印嵌入图像,强度由NVF函数确定。在检测时,用白化滤波器对图像进行预处理。由于水印数据是随机的,而图像数据高度相关,白化滤波器起到增加水印数据能量,同时降低图像数据能量的作用。由理论计算得出选择滤波器的原则。然后,通过自相关检测,得到反映几何形变的峰值点。对实验结果的分析证明,该算法对各类几何攻击都能够精确定位。     

A General Strategy for Antimony-Based Alloy Nanocomposite Embedded in Swiss-Cheese-Like Nitrogen-Doped Porous Carbon for Energy Storage

Due to its suitable working voltage and high theoretical storage capacity, antimony is considered a promising negative electrode material for lithium-ion batteries (LIBs) and has attracted widespread attention. The volume effect during cycling, however, will cause the antimony anode to undergo a severe structural collapse and a rapid decrease in capacity. Here, a general in situ self-template-assisted strategy is proposed for the rational design and preparation of a series of M Sb (M = Ni, Co, or Fe) nanocomposites with M N C coordination, which are firmly anchored on Swiss-cheese-like nitrogen-doped porous carbon as anodes for LIBs. The large interface pore network structure, the introduction of heteroatoms, and the formation of strong metal N C bonds effectively enhance their electronic conductivity and structural integrity, and provide abundant interfacial lithium storage. The experimental results have proved the high rate performance and excellent cycling stability of antimony-based composite materials. Electrochemical kinetics studies have demonstrated that the increase in capacity during cycling is mainly controlled by the diffusion mechanism rather than the pseudocapacitance contribution. This facile strategy can provide a new pathway for low-cost and high-yield synthesis of Sb-based composites with high performance, and is expected to be applied in other energy-related fields such as sodium-/potassium-ion batteries or electrocatalysis.     

Molecular packing correlated fluorescence in TIPS-pentacene films

The molecular packing and optical properties of exposed and buried layers (i.e. the layers at the top surface and near the substrate, respectively) were systematically studied in 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) films coated by spin-coated (SC) and droplet-pinned-crystallization (DPC) methods. Buried layers in both films exhibit intense photoluminescence (PL) resembling the behaviors of the molecules in dilute solution ascribing to weak π-π stacking, while the exposed layers show extremely weak PL due to strong crystallinity. Polarized excitation PL spectra demonstrate that molecular orientation of the buried layers is quasi-ordered in the film coated by DPC method and completely disordered in the film coated by SC method. Besides, the strong crystallinity of the exposed TIPS-pentacene is verified by grazing incident wide-angle X-ray scattering measurement. The distinct differences in optical and structural properties between the exposed and buried layers indicate that TIPS-pentacene films are inhomogeneous in vertical direction due to interfacial effect, which affects the performance of photodiode fabricated with both films. The understanding of the molecular packing correlated fluorescence in TIPS-pentacene films is vital for optimizing the film structure to achieve high performance organic electronic devices.     

密钥控制的多S盒Rijndael算法

根据AESS盒的设计思想构造出了一批密码性能良好的S盒,并从方差的角度对它们的雪崩概率进行了分析。在此基础上,对Rijndael算法中的字节代换步骤SubBytes进行改进,从而提出了一种基于密钥控制的多S盒的Rijndael算法。实验结果表明,改进后的算法对差分攻击的抵抗能力有所提高,雪崩效应更趋合理。     

多径信道下辅助矢量接收机性能分析

研究了在直接序列码分多址(DS-CDMA)系统中,多径环境下一种基于RAKE结构的辅助矢量接收机。该接收机在收集多径信号的同时抑制系统中的多址干扰,从收集的多径信号中估计出信道响应矢量,并利用估计出的信道响应矢量对多径信号进行合并,最后进行判决。仿真结果表明,辅助矢量接收机能够有效地去除DS-CDMA系统中的多址干扰,同时具备良好的抗多径衰落性能,误码性能明显优于RAKE接收机。     

ADM4210热插拔控制器的原理及应用

ADM4210器件构成的热插拔保护电路,为电路提供欠压、过压、过流和短路保护,能够在不响应工作底板正常运行情况下．实现板卡的热插拔。介绍了ADM4210的主要特性、工作原理及应用电路设计。     

Hyperelastic,Robust, Fire-Safe Multifunctional MXene Aerogels with Unprecedented Electromagnetic Interference Shielding Efficiency

MXene aerogels have shown great potential for many important functional applications, in particular electromagnetic interference (EMI) shielding. However, it has been a grand challenge to create mechanically hyperelastic, air-stable, and durable MXene aerogels for enabling effective EMI protection at low concentrations due to the difficulties in achieving tailorable porous structures, excellent mechanical elasticity, and desired antioxidation capabilities of MXene in air. Here, a facile strategy for fabricating MXene composite aerogels by co-assembling MXene and cellulose nanofibers during freeze-drying followed by surface encapsulation with fire-retardant thermoplastic polyurethane (TPU) is reported. Because of the maximum utilization of pore structures of MXene, and conductive loss enhanced by multiple internal reflections, as-prepared aerogel with 3.14 wt% of MXene exhibits an exceptionally high EMI shielding effectiveness of 93.5 dB, and an ultra-high MXene utilization efficiency of 2977.71 dB g g⁻¹, tripling the values in previous works. Owing to the presence of multiple hydrogen bonding and the TPU elastomer, the aerogel exhibits a hyperelastic feature with additional strength, excellent stability, superior durability, and high fire safety. This study provides a facile strategy for creating multifunctional aerogels with great potential for applications in EMI protection, wearable devices, thermal management, pressure sensing, and intelligent fire monitoring.     

大型泵站前池水流流态的模拟

泵站前池水流常有如表面漩涡、大尺度回漩等不良流态的存在，为准确模拟其流态，可采用以弗汝德模型为基础，加大水流流速来进行模拟．模型比λ＝1：8的泵站前池模型的试验结果表明，将弗汝德模型水流流速提高约0．5倍，相当于流速比尺λ＝λ0.3能得到较为满意的前池流态模拟。