Phonon Dynamics at Surfaces and Interfaces and Its Implications in Energy Transport in Nanostructured Materials—An opinion Paper

Nanoscale thermal transport has attracted considerable attention because of both fundamental scientific interest and important engineering applications. For semiconductors and insulators, energy transport is dominated by phonons, whose behavior at surfaces and interfaces plays a significant role in energy transport processes. In this article, we present opinions on phonon dynamics at surfaces and interfaces and the implications on nanoscale thermal transport. The effects of roughness, bonding strength, coherence, and nanoscale constrictions are discussed. The existence of two specularity parameters at an interface (separate values for transmitted and reflected phonons) and the implications of phonon reflection at free surfaces to the thermal conductance of nearby interfaces are two concepts that have not been previously discussed in the literature. We provide some outlook and potential topics for future studies.     

循环定位链传动的负变位及重合度设计计算

介绍循环定位链传动的结构及工作原理,并分析啮合过程。通过对链轮的负变位设计,使运动轨迹与理论轨迹重合,提高了啮合质量,并对啮合的重合度作了分析计算,对重合度的选择提供了依据,对提高传动的平稳性具有重要意义。     

基于真空技术的大口径炮弹搬运系统

研制了一种运用真空技术的大口径弹药搬运系统,较好地解决了大口径弹药分解拆卸过程中,拔弹、上弹环节人员劳动强度大,安全系数低等难题,实现了大口径炮弹的快速抓取、提升、移动和释放,提高作业效率近6倍,具有较高的社会效益和军事效益,以及很好的推广应用前景.     

3D打印技术解决未来空间运输问题的方案设想

3D打印技术在工业生产各领域,尤其是在航空航天领域具有广泛的用途。通过专利研究了3D打印技术及其分支技术的发展等问题,重点分析了通过3D打印技术在月球建造基地、在空间站打印结构体、电路板、传感器等部件的可行性与在太空特殊环境下需注意的问题和解决方案。预测了3D打印技术在解决未来空间运输问题的发展方向。     

欧洲高超声速技术发展路线研究

以2012年第17届AIAA国际空天飞行器与高超声速系统技术会议上法国航空航天研究院进行的题为《欧洲高超声速综述》的报告为线索,对欧洲高超声速研究现状进行分析与梳理,将研究主要分为空间进入、航空运输和基础研究等领域,并对每个领域内的典型项目进行了技术性的研究。通过分析可以看出,欧洲的高超声速项目多瞄准远期空天飞行等目标,武器装备发展意图并不明确。此外,欧洲的高超声速飞行器相关技术并不成熟,短期内可能处于技术研究阶段,不能进行试飞或投入应用。     

A New Donor–Acceptor–Donor Polyfluorene Copolymer with Balanced Electron and Hole Mobility

A new alternating polyfluorene copolymer poly[2,7‐(9,9‐dioctylfluoren)‐alt‐5,5‐(5′,8′‐di‐2‐thienyl‐(2′,3′‐bis‐(3′′‐octyloxyphenyl)‐quinoxaline))] (APFO‐15), which has electron donor–acceptor–donor units in between the fluorene units, is synthesized and characterized. This polymer has a strong absorption and emission in the visible range of the solar spectrum. Its electroluminescence and photoluminescence emissions extend from about 560 to 900 nm. Moreover, solar cells with efficiencies in excess of 3.5 % have been realized from blends of APFO‐15 and an electron acceptor molecule, a methanofullerene [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM). It has also been observed that electron and hole transport is balanced both in the pure polymer phase and in polymer/PCBM bulk heterojunction films, which makes this material quite attractive for applications in opto‐electronic devices.     

PTN技术概览及作为综合业务传送网应用价值的探讨

简要介绍了PTN技术的技术特征和最新标准化进展,分析了其作为综合业务传送网的技术优势,并结合国内实际应用案例总结了网络演进策略。     

Direct View on the Origin of High Li+ Transfer Impedance in All-Solid-State Battery

Large interfacial resistance plays a dominant role in the performance of all-solid-state lithium-ion batteries. However, the mechanism of interfacial resistance has been under debate. Here, the Li⁺ transport at the interfacial region is investigated to reveal the origin of the high Li⁺ transfer impedance in a LiCoO₂(LCO)/LiPON/Pt all-solid-state battery. Both an unexpected nanocrystalline layer and a structurally disordered transition layer are discovered to be inherent to the LCO/LiPON interface. Under electrochemical conditions, the nanocrystalline layer with insufficient electrochemical stability leads to the introduction of voids during electrochemical cycles, which is the origin of the high Li⁺ transfer impedance at solid electrolyte-electrode interfaces. In addition, at relatively low temperatures, the oxygen vacancies migration in the transition layer results in the formation of Co₃O₄ nanocrystalline layer with nanovoids, which contributes to the high Li⁺ transfer impedance. This work sheds light on the mechanism for the high interfacial resistance and promotes overcoming the interfacial issues in all-solid-state batteries.     

Enhanced performance in inverted polymer solar cells employing microwave-annealed sol-gel ZnO as electron transport layers

In this work, we propose a facile microwave-assisted approach for annealing sol-gel derived ZnO films to serve as electron transport layers (ETLs) for inverted bulk heterojunction polymer solar cells. We have demonstrated an impressive enhancement in performance for devices based on a poly (3-hexylthiophene) (P3HT): (6,6)-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) system employing the microwave-annealed ZnO (ZnO (MW)) ETLs in comparison to the cases using the conventional hotplate-annealed ZnO (ZnO (HP)) ones. The better electron transport in the device with the ZnO (MW) ETL is mainly ascribed to the preferable interfacial contact as evidenced by the morphology characteristics. Furthermore, the comprehensive analyses conducted from the light intensity dependent photocurrent and photovoltage measurements, the capacitance-voltage characteristics, and the alternating current impedance spectra suggest that the utilization of the ZnO (MW) ETLs can effectively suppress trap-assisted recombination as well as charge accumulation at the interface between P3HT: PC₆₁BM layers and ZnO layers, which is responsible for the enhanced device performance.     

对往复式压缩机故障的危害探究

往复式压缩机作为工业生产的重要设备有着无可替代的价值。是生产生活必不可少的重要器械。作为最常见的一种压缩机,其故障的危害性不容忽视。本文正是从此出发,分析讨论往复式压缩机重要部件与循环系统的故障对压缩机的影响。