Synthesis and Characterization of 2D Molybdenum Carbide (MXene)

Large scale synthesis and delamination of 2D Mo₂CT _x (where T is a surface termination group) has been achieved by selectively etching gallium from the recently discovered nanolaminated, ternary transition metal carbide Mo₂Ga₂C. Different synthesis and delamination routes result in different flake morphologies. The resistivity of free‐standing Mo₂CT _x films increases by an order of magnitude as the temperature is reduced from 300 to 10 K, suggesting semiconductor‐like behavior of this MXene, in contrast to Ti₃C₂T _x which exhibits metallic behavior. At 10 K, the magnetoresistance is positive. Additionally, changes in electronic transport are observed upon annealing of the films. When 2 μm thick films are tested as electrodes in supercapacitors, capacitances as high as 700 F cm^?3 in a 1 m sulfuric acid electrolyte and high capacity retention for at least 10,000 cycles at 10 A g^?1 are obtained. Free‐standing Mo₂CT _x films, with ≈8 wt% carbon nanotubes, perform well when tested as an electrode material for Li‐ions, especially at high rates. At 20 and 131 C cycling rates, stable reversible capacities of 250 and 76 mAh g^?1, respectively, are achieved for over 1000 cycles.     

Non‐Lithographic Fabrication of All‐2D α‐MoTe2 Dual Gate Transistors

As one of the emerging new transition‐metal dichalcogenides materials, molybdenum ditelluride (α‐MoTe₂) is attracting much attention due to its optical and electrical properties. This study fabricates all‐2D MoTe₂‐based field effect transistors (FETs) on glass, using thin hexagonal boron nitride and thin graphene in consideration of good dielectric/channel interface and source/drain contacts, respectively. Distinguished from previous works, in this study, all 2D FETs with α‐MoTe₂ nanoflakes are dual‐gated for driving higher current. Moreover, for the present 2D dual gate FET fabrications on glass, all thermal annealing and lithography processes are intentionally exempted for fully non‐lithographic method using only van der Waal's forces. The dual‐gate MoTe₂ FET displays quite a high hole and electron mobility over ≈20 cm² V^?1 s^?1 along with ON/OFF ratio of ≈10⁵ in maximum as an ambipolar FET and also demonstrates high drain current of a few tens‐to‐hundred μA at a low operation voltage. It appears promising enough to drive organic light emitting diode pixels and NOR logic functions on glass.     

基于动态逆与QFT 的鲁棒飞行控制器

针对保证无人战斗机控制器的解耦性能和鲁棒性能问题,设计一个某无人战斗机的姿态控制器。将动态逆(DI)和定量反馈理论(QFT)相结合,用动态逆实现无人战斗机控制的动态解耦,用定量反馈理论保证控制器的鲁棒性能,并以实例进行仿真结果分析。仿真结果表明:在气动数据变化±30%的范围内,DI与QFT控制器可以实现对飞机姿态的精确控制,能很好地解决飞机的姿态控制问题,有较好的工程应用价值。     

一种激光引信光学系统的虚拟样机建模技术

光学系统是激光引信的重要组成部分,同样,光学系统的建模也是激光引信虚拟样机技术的核心部分。由于文章所研究的光学系统采用脉冲体制激光器和不规则面形探测器,并且所要探测的目标特性较为复杂,传统的光学仿真软件不能满足虚拟样机的要求。所以,文章采用统计建模与Matlab软件编程相结合的方法进行光学系统虚拟样机建模。     

MOS器件的X射线辐照效应

研究了在10keVX射线辐照情况下，MOS器件的阈值电压随总剂量和剂量率的改变而变化的趋势。实验结果表明，辐照后，与用Co^60作为辐射源辐照所做实验结果明显不同的是，NMOS器件的阈值电压漂移幅度远大于PMOS器件的漂移幅度。文中对这种现象进行了讨论。     

Strong Electronic Interaction between Amorphous MnO2 Nanosheets and Ultrafine Pd Nanoparticles toward Enhanced Oxygen Reduction and Ethylene Glycol Oxidation Reactions

Strengthening the interface interaction between metal and support is an efficient strategy to improve the intrinsic activity and reduce the amount of noble metal. Amorphization of support is an effective approach for enhancing the metal-support interaction due to the numerous surface defects in amorphous structure. In this work, a Pd/a-MnO₂ electrocatalyst containing ultrafine and well-dispersive Pd nanoparticles and amorphous MnO₂ nanosheets is successfully synthesized via a simple and rapid wet chemical method. Differing from the crystal counterpart (Pd/c-MnO₂), the flexible structure of amorphous support can be more favorable to electron transfer and further enhance the metal-support interaction. The synergism between Pd and amorphous MnO₂ results in the downshift of the d-band center, which is beneficial for the desorption of critical intermediates both in oxygen reduction reaction (ORR) and in ethylene glycol oxidation (EGOR). Due to the lower *^.OH desorption energy of Pd/a-MnO₂ surface, the rapid dissociation of *OH from Pd facilitates the formation of H₂O in ORR, thus demonstrating superior ORR performance comparable to Pt/C. For EGOR, the presence of amorphous MnO₂ promotes the formation of adsorbed OH species, which accelerates the desorption of intermediate CO from Pd sites, and thus exhibits excellent EGOR activity and stability.     

Facile Synthesis of Medium-Entropy Metal Sulfides as High-Efficiency Electrocatalysts toward Oxygen Evolution Reaction

Developing highly efficient and durable electrocatalysts toward oxygen evolution reaction (OER) is an urgent demand to produce clean hydrogen energy. In this study, a series of medium-entropy metal sulfides (MEMS) of (NiFeCoX)₃S₄ (where X = Mn, Cr, Zn) are synthesized by a facile one-pot solvothermal strategy using molecular precursors. Benefiting from the multiple-metal synergistic effect and the low crystallinity, these MEMS show significantly enhanced electrocatalytic OER activity compared with the binary-metal (NiFe)₃S₄ and ternary-metal (NiFeCo)₃S₄ counterparts. Especially, (NiFeCoMn)₃S₄ delivers a low overpotential of 289 mV at 10 mA cm⁻², a decent Tafel slope of 75.6 mV dec⁻¹ and robust catalytic stability in alkaline medium, outperforming the costly IrO₂ benchmark electrocatalyst and the majority of the reported metal sulfide-based electrocatalysts until now. These MEMS with facile synthesis and excellent electrocatalytic performance bring a great opportunity to design desirable electrocatalysts for practical application.     

突发8PSK信号载波同步算法研究

在时分多址(TDMA)通信网络中,由于COSTAS环会出现"悬隔效应"导致其不太适应突发方式载波恢复的解调要求。因此,提出了一种开环结构的全数字无前导字的突发8PSK解调方案。与常规算法相比,该算法可以在较低信噪比、较大载波频偏下工作,适合用于突发通信。在已有的理论基础上对算法进行了讨论,并给出了计算机的仿真结果。     

河南烟区烤烟叶片含钾量低的原因初探

温室盆栽和大田试验结果揭示．烟叶评吸质量与烟叶含钾量呈正相关。尽管河南植烟土壤含钾量高于南方红壤，但其所产烟叶含钾量却远低于红壤。造成这种现象的主要原因包括土壤水分不足钾素迁移速度低，补充速度赶不上吸收速度的需要；土壤固相对钾的固定，河南烟区上镶中过量的钙对钾吸收的拮抗等。盆栽试验表明烤烟缺钾临界值为烤烟收获后土壤速效钾含量小于150mg／kg。通过调节土壤水分状况，选用吸钾能力高的烤烟品种和调节烤烟的生理活性可以有效地提高烟叶含钾量。     

甘蔗糖液中C1~-和SO_4~(2-)的紫外线检测──离子色谱法测定

提出了采用紫外检测——高效离子色谱法测定甘蔗糖液样品中的Cl-和5O42-的分析方法。色谱分离系统由yydac302IC离子色谱柱和3mmol／L邻苯二甲酸溶液（PH＝5．0，用四硼酸钠调节）组成。利用流动相具有的紫外光吸收特性，周紫外光度检测器对分离后的Cl-和SO42-进行间接检测。