A low-power,fast-settling reference circuit for high-speed high-resolution ADC

A low-power, fast-settling reference buffer used for high-speed high-resolution ADC is proposed. A replica buffer forms a closed loop to stabilise the operating point and a cascaded gm-boosting technique provides sufficient low output impedance, all of which ensure a high performance for the proposed buffer. The measured results show that the proportion of power consumption by the proposed buffer over ADC is only 2.7%, while settling to 12-bit accuracy within 0.13 ns.     

Adhesion strength of leadframe/EMC interfaces

Cu-based leadframe sheets were oxidized in alkaline solutions to produce brown and/or black oxide on the surfaces, and molded with epoxy molding compound (EMC). The adhesion strength of leadframe/EMC interface was measured using sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens. Results showed that the adhesion strength of leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates. The presence of smooth-faceted Cu₂O on the surface of the leadframe gave close to zero fracture toughness (G_C) and suitable pull strength (PS). A direct correlation between G_C and PS showed that PS can be a measure of G_C only in a limited range.     

Effect of thermal cycles on the mechanical strength of quad flat pack leads/Sn-3.5Ag-X (X=Bi and Cu) solder joints

Quad Flat Pack (QFP) Leads/Sn-3.5Ag-X (X=Bi and Cu) joint was thermally cycled between 243 K and 403 K or 273 K and 373 K, and both metallographic examination and mechanical pull test were performed to evaluate thermal fatigue damage of the joint. The addition of bismuth drastically degrades the thermal fatigue resistance of Sn-3.5Ag solder. On the other hand, the pull strength of Sn-3.5Ag-Cu solder joints slightly decreased with increasing number of thermal cycles, though it still remains higher in comparison to that for conventional Sn-37Pb or bismuth containing solder joint. The behavior observed here reflects the isothermal fatigue properties of bulk solder, because thermal fatigue crack initiates at the surface of solder fillet and propagates within the fillet in an early stage of fatigue damage. Furthermore, the lead phases lying at the interface between lead-frame and bismuth containing solder joint may promote the crack propagation at the interface, resulting in the extremely low thermal fatigue resistance of the joint.     

Gel Polymer Electrolyte toward Large-Scale Application of Aqueous Zinc Batteries

Aqueous zinc batteries are promising candidates for energy storage and conversion devices in the “post-lithium” era due to their high energy density, high safety, and low cost. The electrolyte plays an important role in zinc batteries by conducting and separating the positive and negative electrodes. However, the issues of zinc dendrites growth, corrosion, by-product formation, hydrogen evolution and leakage, and evaporation of the aqueous electrolytes affect the commercialization of the batteries. Moreover, the widely used aqueous electrolytes result in large battery sizes, which are not conducive to the emerging smart devices. The intrinsic properties of gel polymer electrolytes (GPEs) can solve the above problems. In order to promote the wider application of GPEs-based zinc batteries, in this review, the working principle and the current problems of zinc batteries are first introduced, andthe merits of GPEs compared to aqueous electrolytes are then summarized. Subsequently, a series of challenges and corresponding strategies faced by GPE is discussed, and an outlook for its future development is finally proposed.     

基于射线跟踪的小区信号强度估计

基于经验模型的无线信号强度估计方法无法针对具体物理场景,估计结果精度低,无法满足移动通信网络规划和优化的需要。射线跟踪技术能依据场景信息跟踪电波传播路径,但现有的反向跟踪方法在进行室外成片区域信号强度估计时复杂度高,无法实用。为提高估计结果的精度,降低估计方法的复杂度,提出了一种正向跟踪信号强度估计方法,将基站天线处发射的电磁波模拟成离散的射线,在考虑建筑物形状、分布信息的基础上采用基于网格的搜索算法跟踪射线路径,在接收点处对反射、绕射射线接收合并,最终得到基站覆盖区域的信号强度分布。仿真结果表明该方法的场强估计结果和实测数据吻合程度远大于经验模型估计方法,并且80%左右的估计结果和实测数据的误差在12 dBm以内,可应用于移动通信网络规划和优化。     

Dynamic multicast link selections for buffer‐aided relaying networks

The management of small cell is considered a key point in next‐generation cellular networks for providing higher data rates, and the relay nodes are expected to be useful to improve the coverage area. Moreover, multicast services have gained importance to disseminate common data to subscribers. The use of buffer‐aided relay for multicast communications is analysed in the paper, and different policies to perform the optimal link selections are compared. These policies are based on the knowledge of the instantaneous link quality indicators as well as the status of the relay buffer and dynamically select the better link according to a suitable probabilistic criterion by improving the aggregate multicast flows. The parameters of these multicast policies are optimized via a Markov chain theoretical framework. The performance for all the proposed methods is analytically derived and validated through computer simulations conducted in different multicast scenarios. The advantages of the proposed schemes are pointed out in terms of multicast throughput, buffer occupancy for different buffer and multicast group size. Copyright © 2016 John Wiley & Sons, Ltd.     

The Effect of He Implantation on the Tensile Properties and Microstructure of Cu/Fe Nano‐Bicrystals

In situ uniaxial tensile experiments on as‐fabricated and helium‐implanted 100 nm‐diameter Cu/Fe bicrystals unearth the effect of individual face‐centred‐cubic/body‐centred‐cubic (fcc‐bcc) interfaces on improving radiation‐damage tolerance and helium absorption. Arrays of nanotensile specimens, each containing a single Cu grain in the bottom half and a single Fe grain on top, were fabricated by templated electron‐beam lithography and electrodeposition. Helium is implanted at 200 keV to a dose of 10¹⁴ ion/cm² nominally into the interface region. High‐resolution, site‐specific transmission electron microscopy (TEM) and through‐focus analysis reveal that the interfaces are nonplanar and contain ≈5 nm‐spaced He bubbles with diameters of 1–2 nm. Nanomechanical experimental results show that the irradiated samples exhibit yield and ultimate tensile strengths more than 60% higher than the as‐fabricated ones, while they retain comparable ductility. Tensile failure always occurs gradually, along the interfaces, with no noticeable shape localization. The absence of brittle failure in He‐irradiated metals might be explained, in part, by the inability of the small He bubbles to serve as sufficient stress concentrators for cracking. In addition, the non‐orthogonal orientation of the interfaces with respect to the loading axes results in the development of both normal‐ and shear‐stress components. Tensile loading along the pillar axes may cause those interfacial regions subjected to normal stresses to detach, while the inclined regions, subjected to shear, to carry plastic deformation until final fracture.     

聚乙二醇阴极修饰层改善聚合物太阳能电池光电性能的研究

通过将聚乙二醇(PEG)掺入活性层制备聚合物太阳 能电池,利用PEG的迁移特性获得阴极修饰层,研 究PEG阴极修饰层对聚合物太阳能电池光电性能的影响。X射线光电子能谱(XPS)分 析表明,掺入活性层中的 PEG迁移到活性层与Al电极之间,形成了阴极缓冲层。吸收光谱、电流密度-电压 特性曲线和外量子 效率谱的分析表明,PEG阴极缓冲层的形成改善了活性层与阴极的界面接触特性, 降低了活性层与电 极之间的能级势垒,有利于载流子传输,因此显著地改善了聚合物太阳能电池的光电性能, 使得器件的开 路电压Voc、短路电流密度Jsc和填充因子(FF)都有明显提高。当P3HT:PCBM 活性层中掺入体积比为0.5%的PEG时,聚合物太阳能电池的能量转换 效率(P CE)最高,达到了3.07%,比未掺杂PEG的参考器件提 高了38.5%。     

激光热力强化电化学沉积试验研究

为了进一步揭示激光的热力效应对电化学沉积的强化作用,构建了激光电化学复合沉积试验系统,进行了理论分析和实验验证。采用激光循环往复的扫描方式照射沉积区域制备沉积层试样,对沉积过程中的力效应和热效应进行测试,最后采用扫描电子显微镜对沉积层的表面形貌和截面形貌进行观察对比。结果表明,激光的热力效应能加快金属离子的还原反应,促进晶核形成和晶粒细化,在激光能量为0.2mJ（20kHz）时,能获得良好的沉积速率（0.198mg/min）;在激光能量为0.4mJ（20kHz）时,沉积层的拉伸强度性能较好,达到256.38 MPa。此研究结果对电解加工技术的发展是有一定帮助的。     

某7000吨浮船坞横向强度分析

文章以某7 000吨浮船坞为研究对象, 对其工作状态、龙骨墩出水状态、沉浮状态等三种工况进行了横向强度分析, 并针对其浮箱内部结构提出了改进措施, 具有一定的应用价值。