Creep Properties of Composite Solders Reinforced with Nano- and Microsized Particles

In the present work the creep properties of Sn37Pb- and Sn0.7Cu-based composite solders reinforced with metallic nano- and microsized Cu and Ag particles have been studied. First, a series of volume percentages of reinforcements were selected to optimize the content of reinforcing particles. Then, the composite solder with optimum volume fraction of reinforcement particles, corresponding to the maximum creep rupture lifetime, was selected to investigate the effect of applied stress and temperature on the creep rupture lifetime of the composite solder joints. In the creep rupture lifetime test, small single-lap tensile-shear joints were adopted. The results indicate that composite solders reinforced with microsized particles exhibit better creep strengthening than composite solders reinforced with nanosized particles, although the mechanical tensile shear strength of composite solder joints reinforced with nanosized particles may be higher than those reinforced with microsized particles. Moreover, the creep strengthening action of the reinforcement particles is more obvious under conditions of lower applied stress or lower test temperature. Strengthening by metallic Cu or Ag reinforcement particles decreases with increasing temperature or applied stress. The Sn0.7Cu-based composite solder reinforced with microsized Ag particles is a low-cost lead-free solder that is easy to process and may have good market potential.     

A novel on-chip high to low voltage power conversion circuit

A novel power supply transform technique for high voltage IC based on the TSMC 0.6μm BCD process is achieved. An adjustable bandgap voltage reference is presented which is different from the traditional power supply transform technique. It can be used as an internal power supply for high voltage IC by using the push-pull output stage to enhance its load capability. High-order temperature compensated circuit is designed to ensure the precision of the reference. Only 0.01 mm2 area is occupied using this novel power supply technique. Compared with traditional technique, 50% of the area is saved, 40% quiescent power loss is decreased, and the temperature coefficient of the reference is only 4.48 ppm/℃. Compared with the traditional LDO (low dropout) regulator, this power conversion architecture does not need external output capacitance and decreases the chip-pin and external components, so the PCB area and design cost are also decreased. The testing results show that this circuit works well.     

Hierarchically Structured Self‐Healing Sensors with Tunable Positive/Negative Piezoresistivity

It is a challenge to manufacture flexible sensors that possess easily distinguishable biomotion signals, strong response reliability, and excellent self‐healing capability. Herein, a self‐healing sensor with tunable positive/negative piezoresistivity is designed by the construction of hierarchical structure connected through supramolecular metal–ligand coordination bonds. The developed sensors can be integrated with the human body to detect multiple tiny signals, such as pronunciation, coughing, and deep breathing. Interestingly, the nanostructured elastomer sensor with and without a flexible yarn electrode shows negative and positive current signals, respectively, making it easy to be identify. Furthermore, it exhibits very fast (2 min), autonomous, and repeatable self‐healing ability with high‐healing efficiency (88.6% after the third healing process). The healed samples still possess flexibility, high sensitivity, and accurate detection capability, even after bending over 10 000 cycles. The excellent biomimetic self‐healing performance combined with the tunable piezoresistivity make it promising for next‐generation wearable electronics.     

Direct 3D Printing of Ultralight Graphene Oxide Aerogel Microlattices

Graphene aerogel microlattices (GAMs) hold great prospects for many multifunctional applications due to their low density, high porosity, designed lattice structures, good elasticity, and tunable electrical conductivity. Previous 3D printing approaches to fabricate GAMs require either high content of additives or complex processes, limiting their wide applications. Here, a facile ion‐induced gelation method is demonstrated to directly print GAMs from graphene oxide (GO) based ink. With trace addition of Ca²⁺ ions as gelators, aqueous GO sol converts to printable gel ink. Self‐standing 3D structures with programmable microlattices are directly printed just in air at room temperature. The rich hierarchical pores and high electrical conductivity of GAMs bring admirable capacitive performance for supercapacitors. The gravimetric capacitance (C_s) of GAMs is 213 F g^?1 at 0.5 A g^?1 and 183 F g^?1 at 100 A g^?1, and retains over 90% after 50 000 cycles. The facile, direct 3D printing of neat graphene oxide can promote wide applications of GAMs from energy storage to tissue engineering scaffolds.     

视音频延时器用大容量FIFO的设计

介绍视音频延时器用大容量FIFO的设计,大容量FIFO的设计采用了SDRAM代替双口RAM,并采用FPGA设计双口SDRAM控制器.该FIFO也可用作高速数据采集系统的数据缓冲.     

嵌入式命令词语音识别系统

当今语音识别技术的一个重要应用就是嵌入式平台上的命令词识别系统,本文提出了一种新的组合解码和置信度的一遍解码方法,同时在算法高精度、运算低复杂度两方面做出了很大的努力,最终在PDA(Compaq iPAQ 3630)平台上实现了一个基于HMM的定点命令词语音识别系统。系统具有较强的鲁棒性和集外词拒识能力,而且系统也具有完整性、高精度、低运算复杂度,整体设计框架灵活,可以非常容易的移植到各种嵌入式平台。     

厚壁管道周向压电Lamb波缺陷图像增强研究

为解决厚壁管道周向压电Lamb波缺陷检测中非平稳信号引起的低信噪比和分辨率问题,利用相位相干成像算法(PCI)从Lamb波信号中提取相位信息构建相位相干因子,通过动态加权处理放大相位分布对超声图像像素幅值的贡献。一方面,该方法保留相位分布一致的缺陷回波幅值,增强缺陷信噪比。另一方面,该方法能通过增强孔径波束指向性,提高后处理图像的虚拟聚焦效果及横向分辨力。通过对外径269 mm、壁厚32 mm的带有20 mm横向裂纹缺陷的厚壁管道进行了探伤检测,对得到的信号进行图像重建。结果表明,PCI的信噪比为25.2 dB,较原始B扫描图像提高了15.6 dB,半波高水平宽度由47.3 mm缩小到22.4 mm,提升了横向分辨率,提高了对缺陷的识别度。     

Sufficient Utilization of Mn2+/Mn3+/Mn4+ Redox in NASICON Phosphate Cathodes towards High-Energy Na-Ions Batteries

Na superionic conductor of Na₃MnTi(PO₄)₃ only containing high earth-abundance elements is regarded as one of the most promising cathodes for the applicable Na-ion batteries due to its desirable cycling stability and high safety. However, the voltage hysteresis caused by Mn²⁺ ions resided in Na⁺ vacancies has led to significant capacity loss associated with Mn reaction centers between 2.5–4.2 V. Herein, the sodium excess strategy based on charge compensation is applied to suppress the undesirable voltage hysteresis, thereby achieving sufficient utilization of the Mn²⁺/Mn³⁺ and Mn³⁺/Mn⁴⁺ redox couples. These findings indicate that the sodium excess Na_3.5MnTi_0.5Ti_0.5(PO₄)₃ cathode with Ti⁴⁺ reduction has a lowest Mn²⁺ occupation on the Na⁺ vacancies in its initial composition, which can improve the kinetics properties, finally contributing to a suppressed voltage hysteresis. Based on these findings, it is further applied the sodium excess route on a Mn-richer phosphate cathode, which enables the suppressed voltage hysteresis and more reversible capacity. Consequently, this developed Na_3.6Mn_1.15Ti_0.85(PO₄)₃ cathode achieved a high energy density over 380 Wh kg⁻¹ (based on active substance mass of cathode) in full-cell configurations, which is not only superior to most of the phosphate cathodes, but also delivers more application potential than the typical oxides cathodes for Na-ion batteries.     

In Situ Conversion Reaction Triggered Alloy@Antiperovskite Hybrid Layers for Lithiophilic and Robust Lithium/Garnet Interfaces

Garnet-type electrolytes demonstrate promising prospects in the field of solid-state lithium batteries owing to their superior ionic conductivity and high (electro)chemical stability toward Li metal, whereas the critical issue of Li dendrite growth and even infiltration throughout garnets limits their practical applications. Herein, a hybrid interlayer consisting of Li₃Bi alloy embedded in antiperovskite-type Li₃OCl matrix is in situ constructed at Li/Li_6.75La₃Zr_1.75Ta_0.25O₁₂ interface by taking the conversion reaction of BiOCl with Li metal. The lithiophilic nature of such interlayer enables an intimate contact of garnet against Li metal, guaranteeing a dramatically reduced interfacial resistance of 27 Ω cm². In addition, the inside electron-conducting Li₃Bi nanoparticles homogenize the interfacial potential distribution, while the outside ion-conducting Li₃OCl matrix with a bandgap of 5.06 eV blocks electron tunneling from Li bulk. Profiting from such synergistic effect, the resultant Li symmetric cell displays a high critical current density of 1.1 mA cm⁻², along with an ultralong cycling life of 1000 h at 0.5 mA cm⁻². Furthermore, the corresponding solid LiNi_0.6Co_0.2Mn_0.2O₂/Li cell delivers a high cycling stability for 150 times accompanied by a capacity retention of 82%. This study puts forward a potential solution for construction of functional layers at Li/garnet interfaces by making use of in situ conversion reaction.     

Reconstruction of the Indium Tin Oxide Surface Enhances the Adsorption of High-Density Self-Assembled Monolayer for Perovskite/Silicon Tandem Solar Cells

Self-assembled monolayers (SAMs) are widely used as carrier transport interlayers for enabling high-efficiency perovskite solar cells (PSCs). However, achieving uniform and pinhole-free monolayers on metal oxide (e.g., indium tin oxide, ITO) surfaces is still challenging due to the sensitivity of SAM adsorption to the complex oxide's surface chemistry. Here, the hydrofluoric acid and the subsequent UV–ozone treatment are employed to reconstruct the ITO surface by selectively removing the undesired terminal hydroxyl and hydrolysis product. This can significantly increase the ITO surface activity and area, thus facilitating the adsorption of high-density SAMs. The resultant fluorinated surface can also prevent the direct contact of ITO with the perovskite active layer and passivate the perovskite bottom interface. Benefiting from the synergistically improved perovskite film formation, charge extraction, energy level alignment, and interfacial chemical stability, the corresponding PSC achieves a greatly enhanced power conversion efficiency of 21.3%, along with an enhanced long-term stability as compared to the control counterpart. Furthermore, a semitransparent PSC with a certified efficiency of 19.0% (with a record fill factor of 84.1%) and a four-terminal perovskite/silicon tandem with an efficiency of 28.4% are also demonstrated.