Effects of temperature and current density on the surface hardness and tribological properties of Ti-6Al-4V alloy by molten salt carburization

Surface hardening of Ti-6Al-4V alloy was achieved by carburization in a molten salt bath containing BaCO₃ as the carbon-yielding agent with electrolysis within the temperature range 790–930°C. The hardness of the total carburizing layer (TCD) is influenced by the bath temperature, the applied current density and the carburizing period. The major hardening effect is considered to be the formation of a solid solution of carbon in -Ti. The oxide film wrapping at the outermost surface of cathodically charged specimens, identified to be mainly BaTiO₃, was formed irrespective of the bath temperature during the quenching process and has no effect on the surface hardening. The optimal carburizing parameters obtained in this study for surface hardening are carburizing at 930±10°C (bath temperature) and 0.3 A/Cm² (applied current density) for 90 min (carburizing period), while those for tribological properties improvement are carburizing at 860±5°C and 0.3 A/Cm² for 90 min.     

脉冲电流对Al-4.5Cu合金定向凝固组织的影响

研究了脉冲电流对Al-4．5Cu合金定向凝固过程及组织的影响。结果表明，随着脉冲电流峰值和频率的增大，Al—4．5Cu合金柱状晶被熔断，形态由细条状变为不连续，失去其定向凝固的取向性；且柱状晶间距随电流峰值和频率的增大而减小。由脉冲电流的引入而产生的脉冲磁压力及焦耳热效应在固液界面处造成的强烈扰动是定向凝固组织失去取向性的主要原因。     

Difference in electron- and gamma-irradiation effects on output characteristic of color CMOS digital image sensors

Changes of the average brightness and non-uniformity of dark output images, and quality of pictures captured under natural lighting for the color CMOS digital image sensors irradiated at different electron doses have been studied in comparison to those from the γ-irradiated sensors. For the electron-irradiated sensors, the non-uniformity increases obviously and a small bright region on the dark image appears at the dose of 0.4 kGy. The average brightness increases at 0.4 kGy, increases sharply at 0.5 kGy. The picture is very blurry only at 0.6 kGy, showing the sensor undergoes severe performance degradation. Electron radiation damage is much more severe than γ radiation damage for the CMOS image sensors. A possible explanation is presented in this paper,     

基于当前最优解的分段搜索策略的人工蜂群算法

为了克服人工蜂群算法在求解函数优化问题中所存在的局部搜索能力差、收敛精度低的缺点,提出了一种基于当前最优解的分段搜索策略的人工蜂群算法。该算法中跟随蜂利用由全局当前最优解和个体当前最优解引导的局部搜索策略逐维进行变异,并采用基于“分段思想”的局部搜索策略对蜜源进行贪婪更新,以提高蜜源的更新效率,从而提高了人工蜂群算法的局部搜索能力。6个标准测试函数的仿真实验结果表明,与基本人工蜂群算法相比,改进后的人工蜂群算法在寻优精度和收敛速度上均有明显提高。     

带温度补偿的双余度舵机伺服控制算法研究

针对双余度舵机不同控制通道间速度环输出指令存在偏差、电流冲击和输出转矩波动等问题,本文提出了一种带温度补偿的双余度舵机伺服控制算法。首先,采用积分均衡的方法抑制传感器和双通道控制器解算误差引起的速度环输出指令的差异,然后采用电流截止负反馈的方法减小负载扰动和电机过渡过程带来的电流冲击,最后通过对电机进行温度补偿来减小环境温度和本体升温对输出转矩的影响。仿真结果表明,该算法能够有效抑制速度环输出指令误差和减小电流冲击,使电机在不同的工作温度下保持良好的性能。     

光伏微逆变器电流传感器和功率管开路故障诊断

当电流传感器出现性能蜕化、故障或失效时,光伏微逆变器系统的输出会受到严重影响,甚至微逆变器系统其他部件有可能被直接损坏而导致整个系统永久失效;微逆变器系统中反激式变换器功率管的开路故障会引起2个交错支路电流不平衡,导致输出电流波形畸变率变大.为此,提出一种基于状态观测器的光伏微逆变器电流传感器和功率管开路故障诊断方法.建立两路反激式变换器的数学模型;构建状态观测器以实现对两路反激式变换器原边电流的在线估计,并生成残差;将残差与阈值进行比较,实现对微逆变器系统中电流传感器与功率管的实时故障诊断.仿真结果验证该方法可行且有效.     

刍议如何在高校计算机教学中培养学生的创新能力

创新是国家兴旺发达的不竭动力,是一个民族进步的灵魂。一个民族没有过硬的创新能力,是不可能长久地立于民族之林的。计算机课程作为高校的基础课程,内容更新速度快,实践性和操作性都很强。计算机教师不仅要引导学生掌握计算机基础知识,还要培养学生的创新能力。本文就如何在高校计算机教学中培养学生的创新能力展开探讨,具有一定的现实意义和指导意义。     

一种三级CMOS运算放大器

运算放大器（OPERATIONAL AMPLIFIER）是模拟电路中最重要和最通用的单元电路之一。基于0.5 umCMOS混合工艺设计了一种三级CMOS运算放大器,它具有放大倍率高,静态功耗低,适合大规模集成等特点。     

Challenges of 22 nm and beyond CMOS technology

It is predicted that CMOS technology will probably enter into 22 nm node around 2012. Scaling of CMOS logic technology from 32 to 22 nm node meets more critical issues and needs some significant changes of the technology, as well as integration of the advanced processes. This paper will review the key processing technologies which can be potentially integrated into 22 nm and beyond technology nodes, including double patterning technology with high NA water immersion lithography and EUV lithography, new devi...     

CMOS图像传感器中的串扰与常用解决方案

CMOS图像传感器中,串扰的大小会影响到图像传感器最终输出图像的质量,串扰越大,最终的图像质量越差,并随着目前像素单元尺寸的逐渐减小,光串扰和电荷串扰都会越来越严重。针对CMOS图像传感器中存在的这2种形式的串扰,结合具体的应用环境,出现了各种各样的解决方案。这些方案多从器件结构改进和材料等方面着手,采取有效措施,将CMOS图像传感器在具体场合应用时的串扰降低到了一个合理的水平。