Multi‐Atomic Layers of Metallic Aluminum for Ultralong Life Lithium Storage with High Volumetric Capacity

Metallic aluminum (Al) have been explored as potential anode materials for lithium storage because of its high theoretical capacity (993 mAh g^–1) and low voltage plateaus. Al possesses high electric conductivity, low cost and environmental friendliness. Unfortunately, Al suffers from huge volume change (>100%) during the lithiation/delithiation process, which inevitably results in the pulverization of electrode and rapid capacity decay during cycling processes. To circumvent above issues, a simple but efficient strategy is demonstrated to fabricate free‐standing multi‐atomic layers of metallic Al by harnessing the good ductility of Al under pressure. The resultant multi‐atomic Al layers are ultrathin, ≈3 nm, and have a large aspect ratio. Such unique features enable multi‐atomic Al nanosheets to construct uniform and compact films with graphene. Thus, the hybrid films with different ratios are achieved, in which the notorious volume change of metallic Al can be efficiently circumvented via the good flexibility of graphene, and the density of whole electrode can be significantly enhanced. As a consequence, the optimized multi‐atomic Al layers‐graphene (AlL‐G) film exhibits a very high volumetric capacity of 1089 mAh cm^–3, high‐rate capability and ultralong cycle life up to 20 000 cycles for lithium storage.     

Taming Charge Transport in Semiconducting Polymers with Branched Alkyl Side Chains

The solid‐state packing and polymer orientation relative to the substrate are key properties to control in order to achieve high charge carrier mobilities in organic field effect transistors (OFET). Intuitively, shorter side chains are expected to yield higher charge carrier mobilities because of a denser solid state packing motif and a higher ratio of charge transport moieties. However our findings suggest that the polymer chain orientation plays a crucial role in high‐performing diketopyrrolopyrrole‐based polymers. By synthesizing a series of DPP‐based polymers with different branched alkyl side chain lengths, it is shown that the polymer orientation depends on the branched alkyl chain lengths and that the highest carrier mobilities are obtained only if the polymer adopts a mixed face‐on/edge‐on orientation, which allows the formation of 3D carrier channels in an otherwise edge‐on‐oriented polymer chain network. Time‐of‐flight measurements performed on the various polymer films support this hypothesis by showing higher out‐of‐plane carrier mobilities for the partially face‐on‐oriented polymers. Additionally, a favorable morphology is mimicked by blending a face‐on polymer into an exclusively edge‐on oriented polymer, resulting in higher charge carrier mobilities and opening up a new avenue for the fabrication of high performing OFET devices.     

Highly Efficient Quasi 2D Blue Perovskite Electroluminescence Leveraging a Dual Ligand Composition

Perovskite light-emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m⁻², and a maximum EQE of 12.2% by incorporating the double-sided ethane-1,2-diammonium bromide (EDBr₂) ligand salt along with the long-chain ligand methylphenylammonium chloride (MeCl). The EDBr₂ successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr₂) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr₂ successfully enables better energy transfer from small n phases to larger n phases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr₂ improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi-2D blue PeLEDs.     

WCDMA网络针尖效应引起掉话问题的分析处理

重庆特殊的地理环境导致因为针尖效应带来的掉话现象比较突出。介绍针尖效应,针对针尖效应引起掉话的几种情况提出3种解决方案,并对3种方案进行优劣比较。通过实际案例分析,得出在不同的情况下要用不同的方案解决掉话问题。     

斜齿轮轴齿面激光熔覆过程中温度场的数值分析

对某汽轮机滑油泵转子的斜齿轮轴齿面的激光熔覆过程进行了研究,利用有限元软件ANSYS对其温度场进行了数值分析。结果表明,在齿面激光熔覆过程中,激光能量输入产生的热量大量集中在轮齿内部,且在熔覆层与齿根结合部位等温线分布比较密集,导致在轮齿内部出现较大的温度梯度,且激光输入产生的热量可对相邻轮齿产生预热的效果;计算结果还表明,越靠近齿顶,等温线越深入基体,若将轮齿的侧面和顶部同时熔覆,极易造成齿顶的过度熔化而塌陷。根据计算结果,提出了齿侧与齿顶分步熔覆的工艺,通过实际熔覆实验,在轮齿表面获得了连续、完整的熔覆层。     

时域展宽特性对相关检测性能的影响分析

时域展宽是激光回波脉冲的重要特性,也是影响激光雷达相关检测性能的重要因素。建立了考虑时域展宽特性的激光回波脉冲数学模型,以此模型和相关检测原理为基础分析了时域展宽特性对相关检测测距误差、信噪比的影响,从激光发射脉冲的近高斯能量时间分布模型出发,推导了时域展宽系数的计算公式,并对理论分析和计算结果进行了仿真论证。仿真结果表明:回波脉冲时域展宽系数与其衰减系数成反比,与发射脉冲上升时间成正比,随着时域展宽系数的增大,激光雷达相关检测系统测距误差增大,信噪比降低。     

Ga掺杂ZnO薄膜的MOCVD生长及其特性

利用低压MOCVD技术在(0002)蓝宝石上外延获得高质量的ZnO∶Ga单晶薄膜,并研究了Ga的不同掺杂浓度对材料电学和光学特性的影响．当Ga/Zn气相摩尔比为3.2 at%时,ZnO(0002)峰半高宽仅为0.26°,载流子浓度高达2.47e19cm－3,透射率高于90%;当载流子浓度升高时,吸收边出现明显的Burstein-Moss蓝移效应．同时室温光致发光谱显示,紫外峰位随载流子浓度的增加而发生红移,峰形展宽,这和Ga高掺杂所引起的能带重整化效应有关．当Ga/Zn比达到6.3 at%时,由于高掺杂浓度下Ga的自补偿效应导致载流子浓度下降．     

目标识别技术及其在现代战争中的应用

讨论目标识别在现代战争各个领域中的应用,总结目标识别技术的发展方向,提出目标识别技术工程化实现方法。     

EV-DO信道估计选径策略探讨

EV-DO是高通公司在cdma2000基础上提出的基于提高分组数据性能的系统标准。文章从数据业务和传统的语音业务的比较说起,介绍了EV-DO系统中区别于cdma2000的技术特征(包括自适应编码、快速自动重复请求机制(ARQ)、速率控制、时隙导频工作方式等),并以此平台为例阐述了信道估计中的选径意义和策略,最后简单分析不同选径策略的性能,其中选径策略的讨论是基于带导频信道的无线系统平台而提出的,具有一定的普遍性。     

Open‐Shell Donor–Acceptor Conjugated Polymers with High Electrical Conductivity

Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm^?1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.