Effect of pH Value on Electroless Deposition of Copper Graphite Powders

Protection of Metals and Physical Chemistry of Surfaces - The effect of pH value on the electroless deposition of copper coated graphite powders (Cu@GPs) was investigated in this paper. The...     

双金属板渐进成形底部鼓包和侧壁鼓凸研究

为了从工艺上提高双金属板成形精度,通过实验结合有限元分析的方法探究了不同工艺参数对成形精度的影响,研究表明:成形角度和成形深度分别是影响底部精度和侧壁精度的最关键因素,当成形角度由30°增大至60°时,底部鼓包高度降低29%,侧壁鼓凸量增加18.5%;当工具头直径由10 mm增大至20 mm时,底部鼓包高度下降13%,侧壁鼓凸量下降16%;当下压量由0.5 mm减小至0.2 mm时,底部鼓包高度下降24%,侧壁鼓凸量增加18.3%;最后优选了合理的工艺参数,使得底面鼓包高度下降49%,侧壁鼓凸量下降41%。     

复合蛋盒型夹层结构动态压缩的力学性能研究

蛋盒型结构是一种新型的周期性单胞轻质结构,该结构具有低密度、高比强度和吸能能力强等特性。本文通过有限元法建立了平面蛋盒型夹芯板与曲面蛋盒型夹心板的落锤冲击模型,对比分析了其抗冲击特性,并且对不同条件下的蛋盒型结构的动态压缩力学性能进行对比分析。结果表明：受到冲击时的夹芯板会经历三个阶段,其中压缩阶段为主要的吸能阶段,通过将冲击动能转变为夹芯板的塑性耗散能来达到缓冲吸能的目的,同时这些特性依赖于成型高度以及上下面板厚度等结构参数,单胞结构成型高度为6mm、单胞周期为20mm、上下面板板厚为0.5mm、曲率半径为400mm时,复合蛋盒型夹芯板具有更好地力学性能。     

Heterogeneous Structure Design to Strengthen Carbon-Containing CoCrFeNi High Entropy Alloy

A carbon-containing CoCrFeNi high entropy alloy (HEA) with heterogeneous structures was obtained through thermome-chanical treatments,which induced concurrent recrystallization and carbide precipitation in the alloy.A combination of high yield strength (556 MPa) and large uniform elongation (45％) was achieved in the investigated alloy.The enhancement of the strength is attributed to the combined effects of grain refinement,precipitation strengthening and microstructural het-erogeneity.Our work demonstrated that the heterogeneity design could be realized by thermomechanical processes,which provided a practical strategy for producing HEAs with high performance.     

Ti对Nb-20Si-5Al超高温合金性能的影响

采用放电等离子烧结法(SPS)制备了Nb-20Si-5Al-xTi(x=0,18,20,22,摩尔分数)超高温合金,研究了Ti加入量对Nb-20Si-5Al合金的室温断裂韧度和高温抗氧化性的影响。结果表明,随着Ti加入量的增加,超高温合金的相组成由Nbss、Nb₅Si₃和Al3Nb相转变成为Nbss、(Nb,Ti)5Si3和Ti相。Ti能明显改善Nb-20Si-5Al超高温合金的断裂韧度和高温抗氧化性能,随着Ti加入量的增加均先提高然后降低,在Ti加入量为20%时,合金断裂韧度最大,为7.41 MPa·m^1/2,相比未加Ti时提高了约56.9%,其高温氧化速率最低,为0.72×10^-4g²/(cm⁴·h)。添加Ti元素后,其氧化产物中出现Ti₂Nb₁₀O₂₉、TiNb₂O₇、TiO₂等,可以提高其氧化膜的致密性,从而提高高温抗氧化性能。     

临界淬火工艺处理高强结构钢Q690GJ的韧化机理

研究了QT(淬火+回火)和QLT(淬火+临界淬火+回火)热处理对高强结构钢Q690GJ微观组织及低温韧性的影响。通过金相、扫描电镜等方法,对低温冲击试样、无塑性转变试样进行了微观分析。结果表明:QLT工艺处理的Q690GJ钢低温韧性明显优于QT工艺。微观组织分析表明:QLT工艺处理试验钢组织为板条马氏体+残留奥氏体,临界淬火工艺形成了更多数量的、且较为稳定的残留奥氏体软相,提高了起裂前的塑性变形能力;同时形成更多取向混乱的马氏体板条束,有效阻碍了裂纹的扩展,从而提高低温韧性、降低无塑性转变温度。     

A temperature sensor based on the splicing of a core offset multi-mode fiber with two single mode fibers

In this paper, a temperature sensor based on the splicing of a core offset multi-mode fiber with two single mode fibers is proposed and demonstrated experimentally. The temperature sensing principle is analyzed and related experiment is performed. By controlling the core offset and splicing length of the specialty multi-mode fiber (SMMF), two sensors with different temperature sensing properties are obtained, and experimental results show that the temperature sensitivity can be up to 48.76 pm/°C in the range of 25—95 °C. Moreover, it has many advantages, including small size, high sensitivity, and simple structure. So it can be used in potential temperature sensing applications, such as industrial production, biomedical science, power electronics, and so on.     

高速动车组弓网离线放电电磁干扰对L波段雷达的影响分析

随着我国高速铁路的迅速发展,高速铁路电磁干扰对沿线电子设备的影响愈来愈引起人们的关注.目前国内相关高校及科研院所对于该电磁干扰的来源和机理已做了较为深入的研究,得出了一些很有价值的理论成果,但其对雷达的影响程度,尚没有明确的结论.研究通过前期的大量测试数据对列车弓网离线引起的电磁干扰、电磁干扰强度与车速的关系进行统计分析及数学建模,现场测试数据定量分析了此噪声对L波段雷达的影响.通过计算得到了在平原地区条件下(干扰源与受扰雷达之间的电磁波传播路径上无遮挡物,仅存在地面反射),干扰强度与雷达和铁道间距、列车速度之间的关系,得出了雷达的有效防护距离.     

A 3.16–7 GHz transformer-based dual-band CMOS VCO

A dual-band, wide tuning range voltage-controlled oscillator that uses transformer-based fourth-order(LC) resonator with a compact common-centric layout is presented. Compared with the traditional wide band(VCO), it can double frequency tuning range without degrading phase noise performance. The relationship between the coupling coefficient of the transformer, selection of frequency bands, and the quality factor at each band is investigated. The transformer used in the resonator is a circular asymmetric concentric topology. Compared with conventional octagon spirals, the proposed circular asymmetric concentric transformer results in a higher qualityfactor, and hence a lower oscillator phase noise. The VCO is designed and fabricated in a 0.18- m CMOS technology and has 75% wide tuning range of 3.16–7.01 GHz. Depending on the oscillation frequency, the VCO current consumption is adjusted from 4.9 to 6.3 m A. The measured phase noises at 1 MHz offset from carrier frequencies of 3.1, 4.5, 5.1, and 6.6 GHz are –122.5, –113.3, –110.1, and –116.8 d Bc/Hz, respectively. The chip area, including the pads, is 1.20.62 mm2 and the supply voltage is 1.8 V.     

SF_6分解产物测试在330kV断路器故障排除中的应用

本文对一起典型的断路器SF6分解产物异常进行了研究分析。通过对断路器内部的测试分析,发现了设备重大安全隐患,确保了设备的运行安全,是一起SF6气体标志性分解产物发现设备内部故障的典型案例。对充SF6气体设备的运行、维护及试验检测具有借鉴意义。