硬质合金刀具月牙洼磨损定量化实验研究

定量研究了细晶粒硬质合金刀具切削钛合金TC4过程中,不同切削参数对月牙洼磨损演变速率和磨损体积的影响。采用等高线图描绘不同切削参数下月牙洼的磨损形貌,求解月牙洼每一个磨损深度下等高线所围区域的面积,并阐述等高线所围区域面积随其磨损深度变化的关系。引入月牙洼磨损演变速率,用于表征月牙洼沿其磨损深度方向磨损的快慢程度,分析了切削参数对月牙洼磨损演变速率的影响规律。求解出不同切削参数下月牙洼的磨损体积,分析了切削速度、进给率和工件材料去除率对月牙洼磨损体积的影响规律。研究结果表明,切削速度是影响月牙洼磨损体积的主导因素。     

低速旋转制导炮弹的滚转过渡过程分析

根据低速旋转末制导炮弹的特点,建立了低速旋转末制导炮弹滚转运动模型,分析了滚转角速度ω与滚转驱动力矩Md之间的传递函数.最后对末制导炮弹出炮口后进入稳速滚转的过渡过程进行了仿真分析.     

对2024铝合金疲劳裂纹扩展寿命进行预测

通过二维弹塑性有限元计算得到Ⅰ型静态裂纹在常幅疲劳载荷下裂纹尖端塑性应变能,进而获得裂纹尖端塑性应变能和应力强度因子幅值的非线性关系;根据能量平衡概念,建立了裂纹扩展速率与裂纹尖端塑性应变能的关系。由此得到一种基于裂纹尖端塑性应变能的疲劳裂纹扩展寿命预测模型,利用该模型预测了中心裂纹平板的疲劳裂纹扩展寿命,预测结果与试验值吻合得很好。     

电流阀值对断续骚扰检测结果的影响

对于某些由开关操作数得出喀呖声率的被测设备,目前大部分检测实验室的断续骚扰分析仪可能会漏计算一些开关操作。解释了标准中"开关操作"的定义,通过实际案例阐述了使用分析仪进行断续骚扰项目检测时,预置电流阀值的选择对检测结果的影响。     

高速率WDM系统光信噪比（OSNR）计算方法及软件实现

通过对光信噪比（OSNR）的理论分析,提出了OSNR的计算方法,并在此基础上开发出计算工具以快速仿真出WDM系统OSNR值,从而能够更加严谨地验证系统建设方案的合理性。     

短螺距手性液晶热敏旋光特性的研究

利用Berreman 4×4矩阵建立理论模型对短螺距手性液晶的旋光率进行求解,使用MATLAB计算得到了手性液晶旋光角随入射角、螺距、盒厚等外界因素变化规律的仿真结果,且通过实验验证了此方法的准确性。对手性液晶旋光效应作为热敏材料的使用进行了实验探究,使用旋光仪测量螺距为250~310nm的手性液晶旋光角,得到手性液晶的热敏旋光特性。结果显示,螺距不同时,液晶的旋光角随温度具有不同程度的变化,但每种螺距下,手性液晶旋光率随温度的变化明显且规律。验证了旋光率热敏效应的稳定性,结果证明将手性液晶作为一种潜在的热敏材料应用的可行性,为手性液晶在温度传感器中的应用提供了实验依据。     

微机电陀螺仪技术及其在智能汽车上的应用

通过分析微机电陀螺仪的原理、性能、特点、应用现状和存在问题,认为微振动陀螺、流体陀螺、固体微陀螺、静电悬浮转子式微陀螺最有可能在短期内用于智能汽车系统.考虑到成本、尺寸、精度上的综合优势,提出微振动陀螺、固体陀螺、流体陀螺、静电悬浮陀螺有在智能汽车上推广使用的可能性,而原子陀螺则具有很好的研究前景.     

Improvement of TEOS-chemical mechanical polishing performance by control of slurry temperature

Effects of slurry temperature on the chemical mechanical polishing (CMP) performance of tetra-ethyl ortho-silicate (TEOS) film with silica and ceria slurries were investigated. The change of slurry properties as a function of different slurry temperatures was also studied to obtain higher removal rates and smoother surface morphology. The changes observed with increasing temperature are as follows: the pH showed a slight tendency to decrease, the conductivity of the slurry showed a tendency to increase, the particle size in the slurry decreased, and the zeta potential of the slurry decreased with temperature. The removal rates linearly increased and maintained at the temperature of about 40 °C. The hydroxyl (OH⁻) groups increased in the slurry as the slurry temperature increased and then they diffused into the TEOS film. The surface of the TEOS film became hydro-carbonated by the diffused hydroxyl groups. The hydro-carbonated surface of TEOS film could be removed more easily. Better surface morphology of TEOS films could be obtained at 40 °C of silica slurry and at 90 °C of ceria slurry. It is found that the CMP performance of TEOS film could be significantly improved or controlled by change of slurry temperature with the same slurry.     

一种有效的对直接序列扩频信号干扰技术

直接序列扩频（DSSS）信号具有较强的抗干扰能力,被广泛应用于各种军民用领域.简要分析了DSSS信号的技术特点和工作原理,针对现有对DSSS信号干扰技术的不足,提出了一种改进的延迟转发干扰技术体制,其可以达到对DSSS信号的高效相关干扰,最后通过计算机仿真分析,验证了该干扰技术对DSSS信号的有效性.     

Rate adaptive resource allocation in orthogonal frequency division multiple access system using multi‐objective immune algorithm

Rate adaptive downlink resource allocation in orthogonal frequency division multiple access system is a constraint optimization problem, which is to maximize the minimum data rate of the user subject to constraint that total power cannot exceed a given value. How to handle the constraint is a key issue for constrained optimization problem. Different with the available schemes on constraint handling, the proposed algorithm converts the constraint into an objective. Then, the resource allocation is combined into a multi‐objective optimization problem. An improved multi‐objective optimization algorithm based on artificial immune system is proposed to solve it. The simulation results show that, compared with previous schemes, the proposed algorithm performs remarkable improvement in sum capacity. Copyright © 2013 John Wiley & Sons, Ltd.