Dual band microstrip patch antenna array loaded with split ring resonators and via holes

Reduction in antenna size by using multi-band radiators play a vital role in the miniaturization of present world wireless handheld devices, as dual band behaviour of the antennas result in the integration of more than one communication standard in a single system and thus, saving the installation space required for separate antennas. In this context, this communication presents a shorted-pin dual band metamaterial inspired microstrip patch antenna array. Under the unloaded conditions, the traditional patch antenna array resonates at 5.8 GHz with gain of 9.8 dBi and bandwidth of 540 MHz. However, when each patch of this traditional antenna array is loaded with split ring resonator (SRR) and a metallic via hole is introduced in the patch, the same antenna array produces an additional resonant frequency in IEEE 802.11b/g/n 2.45 GHz Wi-Fi band with bandwidth and gain of 290 MHz and 5.6 dBi, respectively, while the initial resonant frequency (i.e. 5.8 GHz) gets shifted to IEEE 802.11ac 5 GHz Wi-Fi band, providing the gain and bandwidth of 11.4 dBi and 510 MHz, respectively. The proposed antenna array has been fabricated, and the measured results are presented to validate the proposed array. Moreover, the equivalent circuit of the proposed antenna array has been designed and analyzed to validate the simulated, measured and theoretical results. Attainment of dual band characteristics by incorporating the metamaterial with single band traditional patch antenna array makes this structure novel, as this has been achieved without any extra hardware cost, size and loss of structural planarity. Also, both the frequency bands of this proposed metamaterial inspired antenna array possess considerable gain and bandwidth.     

带预复位机构的推管和摆块推件的叶轮压铸模

叶轮有8个叶片,叶片为薄且面积大的曲面,叶轮的轮毂对模具型芯包紧力较大,若推出机构不合理,容易引起工件变形甚至断裂,故采用8个摆块与1个推管的组合推件机构。分析了铸件的工艺性,论述了模具结构和工作过程。     

Fracture Characteristics of Torsion-Bending Fatigue and Impact Fatigue Failure of Two Steel Pins in a Crawler Excavator

The arms of crawler excavators used in diverse quarries work under extremely harsh conditions. A common failure during their operation is the fracture of the steel pin joints that permit free movement of the two adjacent booms closer to the machine housing, as well as the motion of the backhoe bucket against its nearest boom. This work presents examples of two steel pin joint failures. The pins had a diameter of 90 mm, and the failures resulted in high stand-by time for repairs. The first failure was caused by the combination of bending and torsion fatigue, and the second fracture occurred because of impact fatigue. Optical metallography and scanning electron microscopy/electron dispersive x-ray analysis (SEM/EDS) analysis provided a better understanding of the failure mechanism of the two steel pins, since these particular components exhibited excellent fatigue characteristics in both mating fracture surfaces.     

自动插件机元件管脚视觉检测算法的研究

针对自动插件机的应用需求,提出一种元件管脚视觉检测算法,可对管脚完整度及成型跨距进行检测。首先,对图像进行二值化处理,用连通区域面积特征及最小包围圆对管脚粗定位;其次,通过形态学处理构建ROI,运用Canny检测算子对目标边缘进行像素级定位,之后再根据曲线拟合原理对目标边缘进行亚像素级定位;最后,用权重函数将目标边缘进行圆拟合,获得管脚的精确位置信息。实验结果表明算法具有较高的稳定性,且算法耗时少,能满足自动机插件机的实际应用要求。     

Influence of z-pin length on the delamination fracture toughness and fatigue resistance of pinned composites

The effect of z-pin length on the mode I and mode II delamination toughness and fatigue resistance of z-pinned carbon-epoxy composites is investigated. Experimental testing and mechanical modelling reveals that both the mode I fracture toughness and fatigue resistance increase with the z-pin length due to increased bridging traction loads generated by elastic stretching and pull-out of the pins. The opposite trend occurs for mode II toughness, which decreases with increasing z-pin length due to lower traction loads arising from restrictions on the shear-induced rotation and pull-out of the pins. The mode II fatigue resistance is increased by z-pinning, although it is not dependent on the z-pin length. Increasing the z-pin length beyond a critical size also changes the mode I and mode II delamination fracture and fatigue processes from single to multiple cracking. The effect of z-pin length on the delamination toughening and fatigue strengthening mechanisms is determined.     

存储对IC器件引出端焊接性能的影响

主要研究了存储周期对锡铅/纯锡两种镀层的塑封IC器件引脚焊接性能的影响。分别针对两种不同镀层的元器件引脚设计储存老化试验,通过可焊性及数据分析等手段,获得存储对镀层老化程度的影响及可焊性的变化情况,从而为制定合理的元器件储存期限提供试验依据。     

Robustness enhancement through chip-package co-design for high-speed electronics

The low interaction between chip and package design has an increasingly limiting effect on the system performance. In this paper, the chip-package co-design flow is presented. We address robustness enhancement under the package and interconnection constraints as well as process, voltage, and temperature (PVT) variations by using impedance control, optimal pins assignment and transmitter equalization. From the simulation results we find that without on-chip digital compensation circuit, the variation of the driver's output impedance is 37% under different PVT conditions. However, it is only 5% when digital compensation circuit is used. Through optimal pins assignment the effective inductance of the pins is reduced. When power and ground pins are used as shielding pins, crosstalk is also decreased by 10 dB. Transmitter equalization effectively decreases inter-symbol interference caused by interconnection attenuation and dispersion. In our design example we find that without equalization the eye-diagram is almost closed at the receiver end. On the other hand with one-tap pre-emphasis equalization the eye-diagram is open and has a height of 90 mV and a width of 140 ps. It is also found that there is a clear optimal window for high data rate in this design. Without a chip-package co-design such an optimal window will not be found.     

外倒锥齿的锥度量棒设计原理与MATLAB程序开发

针对倒锥齿的特点进行分析，运用量球测量法中跨球距M值的计算原理及公式，求得相应的锥度量棒的计算式，并在此基础上基于MATLAB开发了锥度量棒设计的计算程序，并给出了应用实例。     

数字电路设计中部分常见问题解析

借助一个双向计时器的设计电路,以举例的形式对数字电路设计中3个方面的常见问题进行了较为详尽地分析,并提出了一些见解,即针对控制设计方面在分析了其实质要求的基础上提出解决问题的关键是选取合适的输入控制信号和正确列出真值表或状态表,针对时序方面通过比较同步和异步的特点并指出可采用同步的"分频"和异步的"级联"完成设计,而针对引脚方面则解析了一般芯片中几个特殊引脚并准确阐述了其所蕴含的不容易被理解的概念。     

CPT,CDT用销钉冲压模具及工艺改进

对ＣＰＴ，ＣＤＴ用销钉进口模具结构及冲压成型工艺进行改进后，模具工艺性良好，取得可观的技术经济效益。