Gratings mask bars and bars mask gratings: visual frequency response to aperiodic stimuli

Gratings and bars produce unexpected mutual visual masking. A grating masks a bar much less than a bar masks a bar; and a bar masks a grating uniformly over the grating field. These effects suggest that neural populations selective for size and orientation may be involved in frequency analysis rather than in simple feature detection.     

Size adaptation: a new aftereffect

If, after prolonged observation of a striped pattern, one views a grating of the same orientation with somewhat narrower bars, then the bars seem even thinner than in fact they are. Broader bars seem broader still. This finding implies a system of size-detecting channels in humnan vision. The phenomenon may underlie many of the classical figural aftereffects.     

Human visual acuity measured with colored test objects

Visual acuity was measured with a grating test object in which alternating bars were matched in brightness but differed in wavelength. If the wavelength difference between adjacent bars was great enough, acuity scores were obtained which were as high as those obtained with test objects in which there was a large brightness difference between adjacent bars.     

压棒工序对烟末质量的影响

为提高烟末利用率,有效降低再造烟叶的生产成本,对比分析压棒工序对烟末的热水可溶物含量及提取率、常规化学成分及感官评吸质量的影响。结果表明:压棒过程可造成烟末少部分热水可溶物损失,对其常规化学成分影响较小,且再造烟叶样品的感官质量差异不大;烟末压棒后其浓缩液粘度急剧增高。烟末压棒后进行再造烟叶投料生产可行,但需要降低烟末压棒时切断作用产生的细小颗粒,或提高烟末棒浓缩液的纯净度,降低浓缩液粘度。     

Lateral hypothalamus: food current intensity in maintaining self-stimulation of hunger

Rats displaying stimulus-bound eating will press bars for currents slightly above eating threshold only when food is near the bar. At higher currents self-stimulation is maintained without food. Such currents may spread to activate consummatory feedback appropriate to the drive elicited; or, for more intensely stimulated drive mechanisms, wider ranges of sensory feedback may be reinforcing.     

挑流式底栏栅取水的初步研究

底栏栅取水工程设计及运用存在的主要问题是廊道从河流层取水，引进沙量较多，易造成底栏栅堵塞及渠道淤积，磨损水轮机等。本文根据山溪性河流的特点，提出利用挑流式底栏栅取水，其功用为：（１）利用挑流排泄漂浮物，减少水中漂浮物堵塞栅隙；（２）由于取水廓道顶上底栏栅坡度小于零，相应增加了廊道进水流量系数，可减小栅条间距；（３）利用推移质卵石对底栏的碰撞，可减少和排除堵塞底栏栅的漂浮物和卡石，从而达到引水防漂防     

HRB400钢筋在模拟混凝土孔隙液中的电化学腐蚀行为

采用循环动电位极化技术研究了HRB400钢筋在不同碳化程度和不同Cl-含量的模拟混凝土孔隙液中的电化学腐蚀行为,分析了腐蚀参数的变化规律,并与HPB235钢筋的腐蚀性能作了对比。结果表明,钝化膜破坏前,HRB400钢筋与HPB235钢筋的腐蚀特性相似;钝化膜破坏时HRB400钢筋对碳化和Cl-的腐蚀敏感性大于HPB235钢筋,前者的临界pH值大于后者、临界Cl-含量小于后者;2种钢筋的接触处暴露于较严重腐蚀环境下,HRB400钢筋作为阳极被加速腐蚀,HPB235钢筋作为阴极受到保护。为了确保工程结构的耐久性,在较严重腐蚀环境下建议对HRB400钢筋和HRB235钢筋的接触处进行绝缘处理。     

Sugarbeet Yield Monitoring for Site-Specific Farming Part I–Laboratory Tests and Preliminary Field Tests

A site-specific sugarbeet yield monitoring system was developed and tested. Two weight-sensing systems were developed, tested, and evaluated on a laboratory test conveyor. One system used 152mm (6in.) idler wheels attached to load cells. The instrumented idlers replaced an existing chain supporting idler on each side of the harvester outlet conveyor. The second system replaced two existing idlers on each side of the harvester outlet conveyor with slide bars covered with UHMW plastic. A product flow rate was obtained from the combined load cell outputs and conveyor speed. Laboratory tests to predict accumulated weight showed a 2.5% error for the slide bar system and a 3.5% error for the idler wheel system. As a result, field testing was performed exclusively with the slide bar weight-sensing system. Calibration was obtained by comparing accumulated truckload weight as indicated by the weight-sensing system to measured gross sugarbeet weight on individual trucks. Typical weight errors ranged from 2% to 3% with an average error of 2.3%. Site-specific yield information was derived from the sugarbeet flow, harvester speed and width, and DGPS receiver. Sugarbeet yield maps were developed as a visual management aid.     

Neural symbolic activity: A psychophysical measure

When a subject views a grating which is partially blocked from view by a cube, adaptation (decrease in contrast of the grating) occurs not only to the visible portions of the grating, but also to those portions blocked from view. This may indicate the existence of a neural mechanism which conveys the information "in back of."     

Color adaptation of spatial frequency detectors in the human visual system

Observers exposed alternately to a vertical grating of one spatial frequency in red light and a vertical grating of different spatial frequency in green light subsequently report frequency-specific color aftereffects when shown gratings in white light. Aftereffects occur, however, only when inspection gratings differ in spatial frequency by one octave or more and the frequency of at least one grating is above 3 cycles per degree. This spatial selectivity of the aftereffect is considered in terms of a neural adaptation model incorporating evidence on the tuning of spatial frequency detectors in the human visual system.     

一种监测笼型感应电动机转子断条故障的新方法

电机断电后，如果有导条断裂，转子磁通在定子绕组中的感应电压将直接受到影响。根据这一特点，提出了一种诊断笼型感应电动机转子断条的新方法，即通过分析定子绕组中感应电压高次谐波的变化来确定转子断条故障。与其他方法相比，该方法能消除三相电压不平衡以及电机磁饱和等现象对故障监测所造成的影响。仿真与试验结果证明了该方法的有效性。     

基于计算机视觉的棒材在线计数系统研究

以计算机视觉技术为基础,利用色彩与阈值相结合的分割算法将端面目标从复杂的背景中分割出来,运用形态学处理方法实现端面边缘的快速检测,通过边界追踪算法提取连通区域的边界长度来实现棒材的计数．该系统较好地解决了粘连和堆叠棒材的准确计数问题,实时性好,可靠性高．     

Emerging chirality in artificial spin ice

Artificial spin ice, made up of planar nanostructured arrays of simple ferromagnetic bars, is a playground for rich physics associated with the spin alignment of the bars and spin texture associated with the magnetic frustration at the bar vertices. The phase diagram is exotic, showing magnetic monopole-like defects and liquid and solid phases of spins arranged in loop states with predicted chiral order. We show that magnetotransport measurements in connected honeycomb structures yield the onset of an anomalous Hall signal at 50 kelvin. The temperature scale can be attributed to the long-range dipolar ice phase. The topological Hall signal arises because chiral loops form at the sample edges, indicating a generic route to exotic states via nanoarray edge structure.     

Shifts in perception of size after adaptation to gratings

After viewing a suitable grating of vertical stripes for 5 minutes, subjects overestimated the width of a rectangle by 6 percent. The shifts in perception of size occurred whether individual stripes in the grating were narrower than, equal to, or wider than the rectangle. Rectangle width was underestimated only if the grating stripes were extremely wide, with a spatial frequency lower than most of the effective amplitude spectrum of the rectangle. These findings (and complementary ones with horizontal gratings) suggest that the visual system codes size on the basis of spatial frequency components, rather than directly in terms of width.     

水工建筑物板式基础结构的微机计算方法

本文提出了利用微机技术计算水利工程建筑中板式基础的方法。数学模型按弹性地基梁计算中的链杆法建立。程序以 BASIC 语言设计。链杆法是求解弹性地基梁的传统方法之一,但其计算十分繁杂,而且计算精度因所取链杆数目的多少相差甚大。本文应用微机使计算大为简化,并能根据工程需要达到计算精度。此法可在工程实际中广为采用。     

机动水稻插秧机送秧机构的计算机辅助设计

滚动直插式水稻插秧机在栽插拔取苗时通常采用对准式送秧机构,这种机构结构简单,但送秧轨迹不够理想.现先设想送秧叉的运动轨迹为一连杆曲线,根据曲柄连杆机构各杆件的几何关系列出轨迹的方程,然后采用有约束条件的直接搜索法中的随机方向搜索法求得轨迹的实现机构,最终改善插秧机的送秧能力。     

油菜秸秆灰分混凝土与钢筋粘结性能的研究

用油菜秸秆灰分等量替代5%、10%、15%的水泥,分别制作强度为C20、C30、C40的秸秆灰分混凝土试件,测试混凝土的粘结强度,考察月牙纹钢筋与油菜秸秆灰分混凝土的粘结性能。结果表明,油菜秸秆灰分掺量为5%时,3个强度下的油菜秸秆灰分混凝土与月牙纹钢筋的粘结强度分别为19.06、19.90、20.08 MPa,与普通混凝土相当,油菜秸秆灰分掺量10%和15%的混凝土与月牙纹钢筋粘结性能较普通混凝土减弱。改变5%掺量油菜秸秆灰分混凝土植入钢筋的类型与月牙纹钢筋直径,月牙纹钢筋与油菜秸秆灰分混凝土的粘结强度是光圆钢筋的2.55倍;月牙纹钢筋直径从12 mm增至16、20 mm,粘结强度分别下降了6%与25%,油菜秸秆灰分混凝土粘结性能随着月牙纹钢筋直径增加而减弱。     

外槽轮排种器性能检测及分析

采用机器视觉方法,检测了外槽轮排种器的排种过程,以期对该排种器性能进行较精确地评价。小麦试验结果表明,排种量呈某种性质的离散分布,其条形图一般非对称,峰值偏左。排种器转速和槽轮工作长度愈大,则排种均匀性愈好,条形图趋于对称。两个参数对排种能力及排种均匀性均存在极为显著的影响,显著性检验尾概率的最大值分别达0 0007和0 0016,效应模型的决定系数最小值为0 9185。排种量的均值达17 0343粒/s～165 9395粒/s,标准差达13 6025粒/s～27 4819粒/s,变异系数达15 6797%～79 8534%。排种量的极差变化较小。槽轮工作长度值18mm可能处于排种量跃升的临界状态附近。