Stereopsis Masking in Humans is Not Orientationally Tuned

Perception ◽  
1978 ◽  
Vol 7 (4) ◽  
pp. 431-436 ◽  
Author(s):  
John E W Mayhew ◽  
John P Frisby
Keyword(s):  
Random Texture ◽  
Global Stereopsis ◽  
Orientational Tuning

A stereopsis signal carried by an oriented random texture and masked by a similar noise texture is not unmasked when the orientation of the noise is rotated. This result is discussed in connection with the orientational tuning of local and global stereopsis processes.

scholarly journals Polycrystal Simulation of Texture-Induced Grain Coarsening during Severe Plastic Deformation

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5834
Author(s):  
Chi Zhang ◽  
Laszlo S. Toth
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Face Centered Cubic ◽  
Shear Texture ◽  
Grain Coarsening ◽  
Random Texture ◽  
Polycrystal Plasticity ◽  
Grain Fragmentation

During severe plastic deformation (SPD), there is usually extended grain fragmentation, associated with the formation of a crystallographic texture. The effect of texture evolution is, however, coarsening in grain size, as neighbor grains might coalesce into one grain by approaching the same ideal orientation. This work investigates the texture-induced grain coarsening effect in face-centered cubic polycrystals during simple shear, in 3D topology. The 3D polycrystal aggregate was constructed using a cellular automaton model with periodic boundary conditions. The grains constituting the polycrystal were assigned to orientations, which were updated using the Taylor polycrystal plasticity approach. At the end of plastic straining, a grain detection procedure (similar to the one in electron backscatter diffraction, but in 3D) was applied to detect if the orientation difference between neighboring grains decreased below a small critical value (5°). Three types of initial textures were considered in the simulations: shear texture, random texture, and cube-type texture. The most affected case was the further shearing of an initially already shear texture: nearly 40% of the initial volume was concerned by the coalescence effect at a shear strain of 4. The coarsening was less in the initial random texture (~30%) and the smallest in the cube-type texture (~20%). The number of neighboring grains coalescing into one grain went up to 12. It is concluded that the texture-induced coarsening effect in SPD processing cannot be ignored and should be taken into account in the grain fragmentation process.

Effect of Roll Gap Geometry on the Evolution of Strain States and Textures during Asymmetrical Rolling in AA 1050

2006 ◽  
Vol 116-117 ◽  
pp. 417-420 ◽  
Author(s):  
Moo Young Huh ◽  
Hyung Gu Kang ◽  
C.K. Kang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
The Finite Element Method ◽  
Asymmetrical Rolling ◽  
Rolling Pass ◽  
Random Texture ◽  
Roll Gap ◽  
Element Method

Asymmetrical rolling was performed by rolling AA 1050 sheets with different velocities of upper and lower rolls. In order to study the effect of roll gap geometry on the evolution of strain states and textures during asymmetrical rolling, the reduction per rolling pass was varied. After asymmetrical rolling, the outer thickness layers depicted shear textures and the center thickness layers displayed a random texture. With decreasing reduction per an asymmetrical rolling pass, the thickness layers depicting shear textures increases. The strain states associated with asymmetrical rolling were investigated by simulations with the finite element method (FEM).

scholarly journals P-Texture Effect on the Fatigue Crack Propagation Resistance in an Al-Cu-Mg Alloy Bearing a Small Amount of Silver

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2481 ◽  
Author(s):  
Yangcheng Hu ◽  
Zhiyi Liu ◽  
Qi Zhao ◽  
Song Bai ◽  
Fei Liu
Keyword(s):  
Electron Microscopy ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Closure ◽  
High Intensity ◽  
Damage Tolerance ◽  
Mg Alloy ◽  
Random Texture ◽  
Texture Effect

P-texture effect on the fatigue crack propagation (FCP) resistance in an Al-Cu-Mg alloy containing a small amount of Ag, is investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back scattering diffraction (EBSD). Results shows that the high intensity P-texture sheet has lower σ0.2/σb, lower FCP rate and higher damage tolerance than random texture sheet. Fracture analysis indicates that the striations spacing of high intensity P-texture sheet is much smaller than that of random texture sheet and it has a rougher fatigue fracture surface, which causes a significant roughness induced crack closure (RICC) effect. The calculation results manifest that high intensity P-texture sheet possesses a higher crack closure level reaching 0.73 as compared to random texture sheet (only 0.25). The statistical analysis results reveal the P-grains have large twist angle of 105–170° and tilt angle of 5–60° with neighboring grains, which is similar to Goss-grains. This is the fundamental reason that P-texture sheet has the same FCP resistance and induces fatigue crack deflection as Goss-texture sheet. Additionally, the most {111} slipping planes of P-grains are distributed in the range of 30–50° deviating from transverse direction of the sheet. This results in more {111} slipping planes to participate in cyclic plastic deformation, which is beneficial to reduce fatigue damage accumulation and improve the damage tolerance of Al-Cu-Mg-Ag alloy.

Global Stereopsis

1988 ◽  
pp. 427-430
Author(s):  
B. Julesz
Keyword(s):  
Global Stereopsis

High Phi and Ghost Phi

2017 ◽  
Author(s):  
Mark Wexler
Keyword(s):  
Slow Rotation ◽  
Illusory Motion ◽  
Motion Adaptation ◽  
Random Texture ◽  
Motion Energy ◽  
Moving Stimulus ◽  
Transient Events ◽  
Fast Motion ◽  
Direction Opposite

When a moving stimulus is followed by certain transient events, an illusion of very fast motion is perceived, in which a random texture undergoes a slow rotation, but every second most observers perceive a very fast jump in the direction opposite to the preceding or “inducing” rotation. These jumps are illusory: during the perceived jump, every frame is a new, random texture, uncorrelated with the previous textures; the last of these random textures is set to turning once again, and the sequence repeats. Thus there is there is no specific correspondence between the textures before, during, and after the jumps and no motion energy corresponding to the jumps. These illusory jumps are called “high phi.” If the transient is immediately “undone,” a different kind of illusory motion is perceived, called “ghost phi.” This example shows a study of the effects of motion adaptation.

Binocular visual processing in the owl’s telencephalon

1979 ◽  
Vol 204 (1157) ◽  
pp. 435-454 ◽  
Keyword(s):  
Visual Processing ◽  
Striate Cortex ◽  
Functional Organization ◽  
Receptive Fields ◽  
Field Size ◽  
Evolutionary Origins ◽  
Structural Differences ◽  
Output Neurons ◽  
Global Stereopsis ◽  
Orientation Movement

Single neurons recorded from the owl’s visual Wulst are surprisingly similar to those found in mammalian striate cortex. The receptive fields of Wulst neurons are elaborated, in an apparently hierarchical fashion,from those of their monocular, concentrically organized inputs to produce binocular interneurons with increasingly sophisticated requirements for stimulus orientation, movement and binocular disparity. Output neurons located in the superficial laminae of the Wulst are the most sophisticated of all, with absolute requirements for a combination of stimuli, which include binocular presentation at a particular horizontal binocular dis­parity, and with no response unless all of the stimulus conditions are satisfied simultaneously. Such neurons have the properties required for ‘global stereopsis,’ including a receptive field size many times larger than their optimal stimulus, which is more closely matched to the receptive fields of the simpler, disparity-selective interneurons. These marked similarities in functional organization between the avian and mammalian systems exist in spite of a number of structural differences which reflect their separate evolutionary origins. Discussion therefore includes the possibility that there may exist for nervous systems only a very small number of possible solutions, perhaps a unique one, to the problem of stereopsis.

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