计算机内部时间长期稳定性分析

介绍了计算机内部时间的原理;设计了利用GPS提供的高精度UTC时间求取计算机内部时间钟差钟速的实验方案;进行了连续90天的实验,积累了175个时段的实验数据;分别利用多项式模型、傅里叶级数模型以及正弦和函数模型,对这些实验数据进行了钟差长期变化的拟合分析。分析表明:计算机内部时间的长期变化规律主要呈线性变化趋势,同时又含有周期性的影响;拟合精度最高的是七阶正弦和函数模型,其拟合残差中误差为0.289秒。     

基于冷量阈值的整流罩空调控制策略研究

针对某航天发射场整流罩空调机组经常出现前级蒸发器结霜和送风温湿度波动问题,进行问题机理分析,结合新风与表冷后目标露点的焓值差提出了一种基于冷量阈值的压缩机PID控制方法;该方法首先根据新风和目标露点的焓值差计算出处理空气所需的实际冷量,然后将该冷量作为基于露点PID控制压缩机输出的上限值;冷量阈值的使用一方面使PID控制一直保持欠调节状态,避免了压缩机投入比的上下跳变而导致送风温湿度波动的问题;另一方面有效解决了压缩机投入冷量过多而导致的蒸发器结霜问题;实践证明,优化后的空调机组运行稳定可靠,温湿度控制精度得到有效提升,分别达到了±0.5 ℃和±3%,满足航天器产品保障需求。     

The <Emphasis Type="Italic">B</Emphasis><Superscript><Emphasis Type="Italic">dual</Emphasis></Superscript>-Tree: indexing moving objects by space filling curves in the dual space

Existing spatiotemporal indexes suffer from either large update cost or poor query performance, except for the B ^x -tree (the state-of-the-art), which consists of multiple B ⁺-trees indexing the 1D values transformed from the (multi-dimensional) moving objects based on a space filling curve (Hilbert, in particular). This curve, however, does not consider object velocities, and as a result, query processing with a B ^x -tree retrieves a large number of false hits, which seriously compromises its efficiency. It is natural to wonder “can we obtain better performance by capturing also the velocity information, using a Hilbert curve of a higher dimensionality?”. This paper provides a positive answer by developing the B ^dual -tree, a novel spatiotemporal access method leveraging pure relational methodology. We show, with theoretical evidence, that the B ^dual -tree indeed outperforms the B ^x -tree in most circum- stances. Furthermore, our technique can effectively answer progressive spatiotemporal queries, which are poorly supported by B ^x -trees.     

Primal or dual: which promises faster spatiotemporal search?

The existing predictive spatiotemporal indexes can be classified into two categories, depending on whether they are based on the primal or dual methodology. Although we have gained considerable empirical knowledge about various access methods, currently there is only limited understanding on the theoretical characteristics of the two methodologies. In fact, the experimental results in different papers even contradict each other, regarding the relative superiority of the primal and dual techniques. This paper presents a careful study on the query performance of general primal and dual indexes, and reveals important insight into the behavior of each technique. In particular, we mathematically establish the conditions that determine the superiority of each methodology, and provide rigorous justification for well-known observations that have not been properly explained in the literature. Our analytical findings also resolve the contradiction in the experiments of previous work.     

降雨入渗对非饱和土边坡稳定性的影响

研究降雨入渗对边坡稳定性的影响规律。采用有限元法进行非饱和土边坡的二维非稳态渗流计算,考虑基质吸作用利用极限平衡法进行非饱和土边坡稳定安全系数计算,进而通过算例计算,分析了降雨过程中及降雨之后,边坡内孔隙水压分布、潜在滑裂面位置以及边坡稳定安全系数的变化情况。着重分析了降雨强度和降雨持续时间的影响,并特别注意分析降雨结束后的边坡稳定性。算例表明某些情况下边坡安全系数最小值出现在降雨之后的数小时或数天,而非降雨的过程中或降雨刚刚结束之时。     

Novel method for haze degraded image scene rendition

To remove haze rapidly and effectively, equivalence between Retinex model and Monochrome Atmospheric Scattering model is explored, and then a novel solution for the Monochrome Atmospheric Scattering model is proposed based on the variational Retinex. Firstly, a variational model for the atmosphere transmission map is constructed, so the transmission map estimation problem can be formulated as a Quadratic Programming optimization problem. Secondly, we calculate the transmission map and resolve the Monochrome Atmospheric Scattering model in each channel to get the Reflectance image; Finally, the Color Constancy is adopted to restore the color of the dehazed image. Experimental results show that the proposed method could remove haze rapidly and effectively, and has some advantages over other algorithms.     

Determining the number of new employees with learning, forgetting and variable wage with a Newsvendor model in pull systems

This paper develops a new quantitative model to find the optimal number of new employees with a Newsvendor model in a pull production system. This model allows learning, forgetting and variable wage. This paper also provides numerical results on sensitivity analysis, and compares the numerical results in three different situations: the situation with both learning and forgetting effect, that with learning effect but without forgetting effect and the situation with neither learning nor forgetting effect. The conclusions drawn from the comparison may offer theoretical insight for human resource managers to make appropriate employment decisions.     

基于WorldFIP现场总线的开关量I/O模件的研发

为了将WorldFIP现场总线技术与传统的开关量控制方法结合起来,介绍了基于WorldFIP的开关量I/O模件,讨论了开关量I/O模件的工作原理及软、硬件的开发设计。模件基于ARM9核心的平台,为实现软PLC虚拟机提供了充分的硬件支持。输入电路有过电压保护的功能,大大减小了现场的安装调试过程中造成的模件损坏。软PLC系统的分为中间码编辑环境和运行环境两部分。编辑环境使用已有的FIPCON软件,运行环境在模件实现,软PLC虚拟机是其主要部分,它采用解释的方式实现中间码的执行。中间码连接了编辑环境和运行环境,在借鉴其它方法的基础上采用了一种相对简单的文法。在开发过程中,对软件和硬件进行了调试和相关测试,最终以解释执行方式实现了开关量的控制。     

微机电系统扭转微镜面驱动器的研制

提出了一种新颖的采用键合减薄工艺制作的微机电系统扭转微镜面驱动器,该种微镜面驱动器工艺制作简便可行.通过对研制的微镜面驱动器进行测试,该驱动器在18V驱动电压时可以达到0.3°的扭转角度,微镜面的频率响应时间小于1ms.同时该驱动器具有较大的微反射镜面,面积达到600μm×700μm,试验结果表明微镜面驱动器将可以应用于光通信领域.     

不同原子频标的物理工作原理对比

本文主要介绍了氢钟、铷钟、铯钟等几种主要原子频标的物理工作原理、性能、工作与应用领域与研究进展;并将介绍了基于CPT(coherentpopulationtrapping)现象研制的芯片级原子钟;最后简述了原子钟的主要应用需求与发展趋势。