基于空间7R机构的联轴器运动学及动力学仿真

应用机械系统动力学仿真分析软件ADAMS,建立了基于空间7R机构的联轴器的仿真模型,并进行了运动学和动力学仿真分析;结合有限元仿真分析软件ANSYS,进一步对该联轴器在转动过程中的应力变化进行了分析。为基于空间7R机构的联轴器的设计提供了理论依据,通过CAE仿真软件对基于空间7R机构的联轴器进行运动和动力性能分析,为该联轴器的实际应用以及进一步的分析打下了良好的基础。     

The influence of object size on judgments of lateral separation

The size of a previously experienced object has a significant effect on depth judgments in visually sparse environments. The present research explored whether familiar object size also significantly influences judgments of lateral separation. Experiment 1 required participants to detect changes in lateral separation using a one-shot change detection paradigm with a closer/same/farther forced-choice response. Participants accurately detected changes in lateral separation, although concurrent changes in object size significantly reduced the accuracy of their judgments such that increases (or decreases) in object size caused a relative underestimation (or overestimation) of separation. Experiment 2 replicated these results using a distance reproduction methodology. These results indicate that familiar object size exhibits a significant effect on judgments of lateral separation.     

基于500 Hz OH-PLIF技术的超声速燃烧室火焰结构

针对超声速燃烧室火焰驻留时间短和高湍流度的特点,利用500 Hz高频OH-PLIF(planar laser induced fluorescence)技术,研究了氢燃料超声速燃烧室火焰结构,结合壁面压力,获得了点火、稳焰以及熄火过程的规律。结果表明：隔离段入口来流马赫数为2的情况下,氢气当量比0.1和0.3,在火花塞点火下,2 ms均能点燃并获得PLIF火焰图像,其中当量比为0.1凹槽内存在爆燃现象,火焰达到稳定燃烧状态较慢(约65 ms)。稳焰过程中,当量比为0.3燃烧相对不充分,燃烧区域更靠近下壁面,燃烧位置和火核位置变化较大。当量比为0.1和0.3,熄火时间均在6 ms内,其中当量比为0.1熄火时火焰是从凹腔中部传播到凹腔前缘位置熄灭并伴随有一个短暂火焰增强的过程,并且在传播至凹腔前缘时已接近熄灭,当量比为0.3在熄灭前则是慢慢变弱,最终在凹腔前缘至喷氢位置间熄灭。     

4×4单元面阵自适应天线系统的设计与实现

面阵系统所采用阵元数多,数据量大,对信号处理机的实时处理能力要求非常高。系统采用基于参考信号的LMS算法,收敛速度较快、运算量低．且易于硬件实现。系统平台采用目前流行的DSP＆FPGA架构,具有高速运算和处理能力,解决了面阵系统对实时处理机的苛刻要求。测试结果表明,系统能自适应地控制天线阵列方向图在用户信号方向产生高增益波束,在干扰信号方向产生较深零陷,并实现零误码率通信。     

一种新的单通道阵列DOA估计快速算法

针对现有单通道阵列DOA估计算法复杂度较高、实时性较差的问题,提出一种适用于单通道阵列的快速DOA估计算法.该算法将常规多通道阵列的空间FFT算法引入单通道阵列信号处理中,将通道切换时间带入FFT运算中,构建了新的变换核函数,利用该核函数可直接对单通道阵列的采样信号进行空间FFT变换,基于此提出了适用于单通道阵列的SA...     

A study of people's sketching habits in GIS

Sketching is traditionally associated withdoodling simple strokes on a piece of paper.Only few professionals outside of design andthe fine arts have recognized the expressivepower of this intuitive modality. However,sketching seems particularly well suited tocapture objects and situations in a spatialenvironment, such as geographic space. To learnmore about the techniques and strategies peopleuse when sketching, a survey of sketching wasconducted. The study showed that paper andpencil sketches contain mostly simple andabstract objects that are composed of only fewstrokes. The spatial configuration of a sceneis primarily expressed through the topologicalordering of objects relative to each other.Metric relationships are used to refine spatialconfigurations. These and other findingssuggest that sketching is an appropriatemodality to interact with a computer where onewants to describe and capture objectconfigurations in a spatial environment, suchas a geographic information system (GIS).     

基于模式空间变换的圆阵无源测向算法研究

建立了均匀圆阵测向系统模型，在其基础上利用模式空间变换方法将均匀圆阵转化为虚拟均匀线阵，使得ESPRIT算法得以应用，从而实现二维无源测向。为验证算法的可行性及可靠性，搭建了七元均匀圆阵实测系统。实验结果表明，该算法所用时间较短，且测向结果较为稳定，可应用于均匀圆阵无源测向系统。     

Spatial Influence of Environmental Axes in a Baseball Field

Abstract

We investigated the influence of environmental axes in a baseball field. In Experiment 1, participants walked either a path in the prototypical orientation (home plate to second base) or one which was rotated 225°. Recall for object locations was best when participants imagined themselves aligned with axes salient from the experienced orientation. In Experiment 2, when learning was through a route text, there was less of an influence of environmental axes. In Experiment 3, when participants walked both paths, memories were good for the atypical orientation, suggesting that task-specific spatial cues can be more influential than a prior conceptual north.     

Individual Differences in Representational Precision Predict Spatial Working Memory Span

Perhaps the signature feature of working memory is that it is limited. In the same subjects, we used two different retrieval tasks to independently measure two different limits of spatial memory. Precision was measured by asking participants to localize a missing target item among a field of other targets and distracters. Capacity was measured with a similar task where participants identified, rather than localized, a set of remembered targets from within a larger set of identical items. Across participants, the precision of localization was positively correlated with the number of successfully retrieved items. These data suggest that an individual's representational capacity may ultimately be constrained by their ability to form precise representations of space.     

Learning Spatial Localization: From Rat Studies to Computational Models of the Hippocampus

In his landmark article, Richard Morris (1981) introduced a set of rat experiments intended “to demonstrate that rats can rapidly learn to locate an object that they can never see, hear, or smell provided it remains in a fixed spatial location relative to distal room cues” (p. 239). These experimental studies have greatly impacted our understanding of rat spatial cognition. In this article, we address a spatial cognition model primarily based on hippocampus place cell computation where we extend the prior Barrera–Weitzenfeld model (2008) intended to allow navigation in mazes containing corridors. The current work extends beyond the limitations of corridors to enable navigation in open arenas where a rat may move in any direction at any time. The extended work reproduces Morris's rat experiments through virtual rats that search for a hidden platform using visual cues in a circular open maze analogous to the Morris water maze experiments. We show results with virtual rats comparing them to Morris's original studies with rats.