Precious‐Metal‐Free Electrocatalysts for Activation of Hydrogen Evolution with Nonmetallic Electron Donor: Chemical Composition Controllable Phosphorous Doped Vanadium Carbide MXene

The insufficient strategies to improve electronic transport, the poor intrinsic chemical activities, and limited active site densities are all factors inhibiting MXenes from their electrocatalytic applications in terms of hydrogen production. Herein, these limitations are overcome by tunable interfacial chemical doping with a nonmetallic electron donor, i.e., phosphorization through simple heat‐treatment with triphenyl phosphine (TPP) as a phosphorous source in 2D vanadium carbide MXene. Through this process, substitution, and/or doping of phosphorous occurs at the basal plane with controllable chemical compositions (3.83–4.84 at%). Density functional theory (DFT) calculations demonstrate that the P? C bonding shows the lowest surface formation energy (ΔG_Surf) of 0.027 eV Å^?2 and Gibbs free energy (ΔG_H) of –0.02 eV, whereas others such as P‐oxide and P? V (phosphide) show highly positive ΔG_H. The P3–V₂CT_x treated at 500 °C shows the highest concentration of P? C bonds, and exhibits the lowest onset overpotential of –28 mV, Tafel slope of 74 mV dec^?1, and the smallest overpotential of ‐163 mV at 10 mA cm^?2 in 0.5 m H₂SO₄. The first strategy for electrocatalytically accelerating hydrogen evolution activity of V₂CT_x MXene by simple interfacial doping will open the possibility of manipulating the catalytic performance of various MXenes.     

基于μCLinux的NAT设备的设计与开发

NAT(网络地址翻译)技术有效地解决了IP地址紧缺的问题,为实现IPv4到IPv6的平滑过渡发挥了巨大的作用.在一个体积小、重量轻、价格低廉的嵌入式平台上实现NAT设备具有很好的实际意义.文中介绍了NAT技术的原理和实现过程,在自行设计的ARM7嵌入式硬件平台上基于μCLinux操作系统实现了NAT的功能,并通过实现其他相关功能,构建了完整的NAT设备,完成了小型网络接入Internet的方案.     

光纤Michelson干涉仪干涉条纹对比度的研究

通过实验测定了光纤Michelson干涉仪输出的干涉信号,并由此计算了干涉条纹对比度.从条纹对比度的拟合曲线出发,分析了可能影响光纤干涉仪干涉信号对比度的主要因素,为实验中条纹对比度的进一步提高提供有益的参考.     

Probabilistic characteristics of the envelope derivative for the sum of signal and narrow-band noise

Probability density and the formula for moments of the envelope derivative of the sum of harmonic signal and Gaussian narrow-band noise have been obtained. A new random function equal to the product of the envelope and phase derivative was introduced and the same probabilistic characteristics were determined for this function. Geometrical interpretation of the sum of signal and noise implies that the introduced function represents angular speed of rotation of the resultant vector.     

Trapping second-order nonlinearity in erbium-doped germanosilicate ring in thermally poled optical fibre

An optical fibre with an erbium (Er)-doped germanosilicate ring structure around the anode hole has been fabricated for stabilising the thermal poling induced second-order nonlinearity (SON). The SON spatial distribution was visualised with second-harmonic microscopy. It was found that the SON layer was trapped in the Er-doped ring under normal poling conditions. Only at higher poling voltages and for much longer poling time could some SON be formed at the core-cladding interface, while most of the SON layer was still firmly confined within the Er-doped ring.     

提高感应电能传输效率的研究

非接触式感应电能传输系统（ICPT）是一种新型的电能传输技术,通过感应电磁耦合向负载提供电能。ICPT的关键部件是松耦合变压器（也叫可分离变压器）它的耦合系数较低,制约着传输效率。本文对非接触感应电能传输系统进行了系统的介绍,并且分析了磁芯材料、工作频率、气隙大小等关键参数对传输效率的影响,着重讨论了可分离变压器的初次级绕组的补偿问题,并且给出了补偿电路的设计方案。     

纳伏级微弱信号放大电路的设计

针对工程测量领域的实际需求,设计了纳伏级微弱信号的放大电路,在信号输入端,通过仿真软件仿真设计,最终选用AD公司的超低噪声差分信号放大芯片AD620,放大倍数为10倍,降低了等效输入噪声。设计了相应的信号调理电路,采用多级放大电路组态方式,运用超低噪声四运放（OP470A）来组建多级带通滤波器,经过多级滤波、多级放大,逐步提高信噪比。通过实验,采用不同频段的噪声,验证SNR的改善情况。利用Multisim仿真软件对系统噪声进行了分析,分析结果显示,在低频段有效地抑制对电路造成影响的各种噪声,信噪比得到了较大的提升。     

平顶光束激光冲击2024铝合金诱导残余应力场的模拟与实验

对平顶光束激光冲击2024铝合金诱导的残余应力情况进行了有限元模拟与实验研究。改进了平顶光束诱导冲击波的压力分布模型,并将该模型用于残余应力场的有限元模拟。在实验室环境下获得了适合用于激光冲击的高质量平顶光束,并使用该光束进行激光冲击2024铝合金的实验,实验结果和模拟结果基本一致。研究发现平顶光束冲击2024铝合金有如下特点:存在一个阈值,当激光冲击波压力小于该阈值时,影响区内残余应力场近似均匀分布;当冲击波压力大于该阈值时会引起"残余应力洞",但该"残余应力洞"内部近似均匀分布。在深度方向上,塑性影响深度和最大残余应力深度随激光冲击波压力的增加而增加。     

强跟踪自适应滤波器实现机动目标的精确跟踪

机动目标状态估计中的一个主要问题是:目标运动的突变性导致状态噪声无法进行统计预测.传统的EKF将噪声看成是高斯白噪声有着本质上的不足,因而无法实现稳定的跟踪.引入Sage-Husa滤波算法对有色噪声进行在线的估计,一定程度上弥补了目标运动模型不够合理的缺憾.在此基础上,从系统容错设计基本原理出发,用归一化残差功率法实时地检测可能出现的数值发散现象,一旦检测到发散,印通过一种改进的强跟踪自适应滤波器进行抑制,有效地提升了滤波的健硕性,实现了稳定跟踪.最后,针对高机动目标的运动特性,仿真验证采用变维滤波模型,用EKF对目标的简单机动进行跟踪,只有目标运动突变时才采用本文提出的算法,以提升计算的实时性.仿真结果表明此算法对高机动目标的跟踪是有效的.     

Design of Liveness-Enforcing Supervisors for Flexible Manufacturing Systems Using Petri Nets

This correspondence develops a methodology to synthesize supervisors for a special class of Petri nets that can well model many flexible manufacturing systems. In our previous work, siphons in a Petri net are divided into elementary and dependent ones on the condition that all emptiable minimal siphons are computed. In this research, a mixed integer programming (MlP)-based deadlock detection technique is used to find some, in general not all, minimal siphons in a plant model without complete siphon enumeration. For each siphon found, depending on its noncontrollability, a monitor is added such that it is invariant-controlled. Our siphon control method guarantees that no emptiable control-induced siphon is generated due to the addition of the monitors. The siphon control process proceeds iteratively until there is no unmarked siphon in the supervisor of a plant model. Compared with the existing approaches, the novel deadlock prevention policy can usually lead to a structurally simple liveness-enforcing supervisor by adding only a small number of monitors and arcs. More importantly, complete siphon enumeration is avoided. A practical flexible manufacturing system (FMS) example is utilized to illustrate the proposed methods.