Perceiving distance accurately by a directional process of integrating ground information

By itself, the absolute distance of an object cannot be accurately judged beyond 2-3 m (refs 1-3). Yet, when it is viewed with reference to a flat terrain, humans accurately judge the absolute distance of the object up to 20 m, an ability that is important for various actions. Here we provide evidence that this is accomplished by integrating local patches of ground information into a global surface reference frame. We first show that restricting an observer's visual field of view to the local ground area around the target leads to distance underestimation, indicating that a relatively wide expanse of the ground surface is required for accurate distance judgement. Second, as proof of surface integration, we show that even with the restricted view, the observer can accurately judge absolute distance by scanning local patches of the ground surface, bit by bit, from near to far, but not in the reverse direction. This finding also reveals that the surface integration process uses the near-ground-surface information as a foundation for surface representation, and extrapolation to the far ground surface around the target for accurate absolute distance computation.     

基于EP2C35的MCU8051内核的小型系统设计

本文介绍了以FPGA芯片EP2C35为平台,构建基于MCU8051内核的SOPC小型系统的结构原理、设计层次、内核各组成模块及参数设置等构建过程,及其性能特点与运行验证,并且阐述了该系统相比于标准8051微控制器的优越性,易于拓展为不同应用场合的嵌入式系统和片上系统。     

超重力场辅助燃烧合成技术制备Fe3Al合金及其抗氧化性能研究

本课题利用超重力场辅助的两步燃烧合成技术成功制备了Fe3Al合金.首先利用Al/Fe2O3之间的铝热反应释放的高热量使得产物(Fe和Al2O3)转变成高温混合熔体,Fe熔体在1000 g超重力场的作用下迅速从高温混合熔体中分离,并和底部的纳米铝粉发生二次燃烧合成,生成致密的Fe3Al金属间化合物.Fe3Al样品中仅存在...     

自发光材料在隧道安全救援中的应用试验研究

隧道侧壁涂刷反射率较高的材料有利于改善隧道内部照明环境,对隧道安全救援也有积极作用。本文利用自发光材料蓄能释光的功能,分析自发光材料的施工工艺,对7种光源条件下自发光材料的余辉亮度进行模型隧道试验测试,得到自然光照射下初始余辉亮度最大,光源停止照射10 min 后,自发光材料的余辉亮度衰减至初始亮度的10％。同时依托云南保腾高速公路鹿山隧道,现场开展了 LED 灯源条件下的余辉亮度实验,探讨了余辉持续时间与安全救援的关系,发现断电30 min 后墙面的视觉诱导作用仍较明显,能对突发事件中隧道内人员的紧急避险和安全救援起到积极作用,为今后进一步合理利用和开发自发光材料在隧道应急救援中的作用提供参考。     

Mineralogical and geochemical features of sulfide chimneys from the 49°39′E hydrothermal field on the Southwest Indian Ridge and their geological inferences

During January–May in 2007,the Chinese research cruise DY115-19 discovered an active hydrothermal field at 49°39′E/37°47′S on the ultraslow spreading Southwest Indian Ridge (SWIR).This was also the first active hydrothermal field found along an ultraslow-spreading ridge.We analyzed mineralogical,textural and geochemical compositions of the sulfide chimneys obtained from the 49°39′E field.Chimney samples show a concentric mineral zone around the fluid channel.The mineral assemblages of the interiors consist ...     

发酵黄腐酸对突变及对造血功能的影响

以小鼠骨髓嗜多染红细胞微核率（ＰＣＥ ＭＮＲ）和骨髓有核细胞数为指标对发酵黄腐酸（ＢＦＡ）和矿源黄腐酸（ＭＦＡ）进行了致突变作用和对造血系统影响的检测,结果结果表明,ＢＦＡ和ＭＦＡ本身无诱变性,可作为食品添加剂,饲料添加剂及药品使用。而且在给小鼠致变环磷酰胺时,ＢＦＡ可抑制突变率,保护分裂细胞,提高造血机能,并有一定的正向量效关系,在较大量使用时无毒副作用,ＭＦＡ也可抑制突变,保护分裂细胞,但在较     

MM4模式和陕西春季降水模拟试验

介绍了有限区域的中尺度数值模拟ＭＭ４的结构,物理过程等,用ＭＭ４模式对陕西省春季透雨和暴雨过程进行模拟试验,证明了ＭＭ４模式在陕西春季大降水预报中的可用性。     

基于Spring和Memcached的iBATIS二级缓存的研究与应用

高性能是J2EE应用程序追求的目标,在特定硬件基础上,数据访问的性能在很大程度上决定了整个应用系统的性能,而缓存往往是提升数据访问性能的最关键因素.在对iBATIS的缓存支持情况进行了介绍和研究的基础上,并结合Spring框架和iBATIS,使用Memcached对iBATIS二级缓存进行了新的实现,使应用的性能得到了很大的提升.     

关于丢番图方程x3-1=py2

设s为正整数且2｜s,素数p=27s2+1,利用初等方法证明了丢番图方程x3-1=py2仅有平凡整数解(x,y)=(1,0).     

攀西地区小麦育种目标的制定

本文根据近年来国内外对小麦育种动态的研究情况。结合攀西地区实际,通过对该地区小麦生产地的抽样调查与分析,制定出了适合该区区域特点的小麦育种目标。