高精度双路相敏放大器的设计

介绍一种将检测的输入正弦信号与基准正弦信号按一定关系进行相位比较,进而产生一直流电压信号。该信号送往控制系统进行相位校正,对其原理、结构设计及制作工艺过程进行了详细的叙述,实验结果表明它可工作在比较恶劣环境中。     

基于粘滑驱动跨尺度精密定位技术的研究现状

目前跨尺度纳米定位技术在纳米操作、大规模集成电路制造和生物技术等众多领域都有着广泛的应用前景.该文对目前应用较多的宏微混合式驱动、压电超声马达驱动、尺蠖式驱动和粘滑式驱动这4种跨尺度定位技术驱动原理进行了介绍,并对其分辨率、速度、推力、尺寸、驱动器数量和结构6个方面进行了比较和分析,得出粘滑驱动以其驱动范围大,分辨率高,结构简单,体积小和集成度高等突出优点,适用于微纳操作领域.对目前国内外粘滑驱动在驱动原理、关键技术和样机实验方面的研究进行了分析,总结出目前粘滑驱动研究中的研究基础和不足,并提出了有待解决的问题和关键技术.     

绕制精密螺旋线的系统技术

在螺旋线型慢波电路行波管中,精密螺旋线是重要的组成部分,由于精密螺旋线的绕制要求高（包括螺距精度、螺旋线形状）,行业研究机构、制造与使用单位、检测部门等在不断地进行系统研究和工艺试验。对绕制精密螺旋线系统的主要结构、控制方法进行了叙述,经实际应用证明了这种方法的可行性。     

五点交比不变性在质心提取中的应用

针对大尺寸3-D视觉测量系统中参数校准精度及特征点质心提取准确性均较低的问题,提出了一种基于五点交比不变性约束的质心提取算法.在高斯曲面多次拟合算法及规则特征点阵的基础上,引入同一空间直线上五点交比值不变性,以此作为约束条件提取特征点的质心;并利用Levenberg-Marquardt(L-M)迭代算法对质心坐标进行优...     

Quantifying the effect of heat stress on daily milk yield and monitoring dynamic changes using an adaptive dynamic model

Automation and use of robots are increasingly being used within dairy farming and result in large amounts of real time data. This information provides a base for the new management concept of precision livestock farming. From 2003 to 2006, time series of herd mean daily milk yield were collected on 6 experimental research farms in the Netherlands. These time series were analyzed with an adaptive dynamic model following a Bayesian method to quantify the effect of heat stress. The effect of heat stress was quantified in terms of critical temperature above which heat stress occurred, duration of heat stress periods, and resulting loss in milk yield. In addition, dynamic changes in level and trend were monitored, including the estimation of a weekly pattern. Monitoring comprised detection of potential outliers and other deteriorations. The adaptive dynamic model fitted the data well; the root mean squared error of the forecasts ranged from 0.55 to 0.99 kg of milk/d. The percentages of potential outliers and signals for deteriorations ranged from 5.5 to 9.7%. The Bayesian procedure for time series analysis and monitoring provided a useful tool for process control. Online estimates (based on past and present only) and retrospective estimates (determined afterward from all data) of level and trend in daily milk yield showed an almost yearly cycle that was in agreement with the calving pattern: most cows calved in winter and early spring versus summer and autumn. Estimated weekly patterns in terms of weekday effects could be related to specific management actions, such as change of pasture during grazing. For the effect of heat stress, the mean estimated critical temperature above which heat stress was expected was 17.8 ± 0.56°C. The estimated duration of the heat stress periods was 5.5 ± 1.03 d, and the estimated loss was 31.4 ± 12.2 kg of milk/cow per year. Farm-specific estimates are helpful to identify management factors like grazing, housing and feeding, that affect the impact of heat stress. The effect of heat stress can be decreased by modifying these factors.     

CK61250E卧式车床尾座套筒锥孔的修复

以加工实例锥孔,阐述了利用数控车床磨削修复大型车床尾座套筒的工艺方法。重点介绍了定位基准选择,工件装夹扭矩传递以及砂轮修整等方面的内容。     

太阳光不平行度对太阳能聚集性能影响的数值研究

对大型对日定向的碟式太阳能反射聚集器,通过数值模拟研究了太阳光不平行度与定向跟踪精度对聚光性能的影响。通过建立锥形光束的概率模型,采用蒙特卡洛法直接模拟了太阳光经碟式反射聚集器后在焦平面上产生的能流分布。比较了不同定向跟踪精度下,不同口径比的反射聚集器对太阳光与平行光的聚集性能差别。     

利用插值法提高PD雷达测距测速精度

脉冲多普勒(PD)雷达是在动目标显示雷达基础上发展起来的一种新型雷达体制,这种雷达具有同时测距和测速能力。该体制雷达的常规测量方法是利用回波强度最大采样点来确定目标信息,但测量误差较大,已不能满足对测量精度要求较高的现代火控雷达等的需求。为此提出了一种对目标回波主瓣面积作梯形近似并插值估计出回波强度真实最大值点位置的方法———插值法,该方法从回波波形的特点入手,原理简单易懂,可在计算量增加不大的情况下大大提高测量精度,仿真结果验证了其有效性。     

统计指标离散化方法及应用

连续数据离散化能够提高数据挖掘算法的分类能力．文中提出一种基于统计指标的连续属性离散化方法,凭借相关系数衡量类与属性间的关联度,获取最优区间列表．引入变精度粗糙集模型,有效地控制数据由离散化导致的信息丢失．该方法在声纳传感器数据识别以及其它领域上进行了应用．实验结果表明,该方法在J48决策树上有很好的分类能力．     

大口径多维调整反射镜架的设计及精度分析

设计了一种能够满足大光斑激光传输的大口径的激光反射镜架,给出满足多维调整使用要求的设计方案,分析了调整架的理论精度、实际精度,分析了误差产生的原因,并根据使用要求对调整架进行了精度设计,进行符合实际的精度分配,使设计满足使用和加工的要求。