scholarly journals Transsaccadic memory of multiple spatially variant and invariant object features

2018 ◽  
Vol 18 (1) ◽  
pp. 6 ◽  
Author(s):  
Jerrold Jeyachandra ◽  
Yoongoo Nam ◽  
YoungWook Kim ◽  
Gunnar Blohm ◽  
Aarlenne Z. Khan
Keyword(s):  
Spatially Variant ◽  
Transsaccadic Memory ◽  
Object Features

scholarly journals Medial occipital cortex participates in a cortical network for transsaccadic feature discrimination: an fMRI paradigm

2021 ◽  
Author(s):  
B. R. Baltaretu ◽  
W. Dale Stevens ◽  
E. Freud ◽  
J. D. Crawford
Keyword(s):  
Spatial Frequency ◽  
Shape Change ◽  
Occipital Cortex ◽  
Cortical Network ◽  
Object Processing ◽  
Repetition Suppression ◽  
Early Visual Cortex ◽  
Transsaccadic Perception ◽  
Transsaccadic Memory ◽  
Object Features

AbstractTo date, the cortical correlates for human transsaccadic vision have been probed for single object features such as orientation (associated with parietal repetition suppression) and spatial frequency (associated with occipital repetition enhancement). Here, we used functional magnetic resonance imaging to distinguish cortical modulations associated with transsaccadic perception of multiple object features. Participants (n=21) viewed a 2D object and then, after sustained fixation or a saccade, judged whether the shape or orientation of the re-presented object had changed. Since feature change was randomized, participants had to remember both features across saccades to perform the task. A whole-brain voxelwise contrast (Saccade > Fixation; n=17) uncovered areas that might be specialized for transsaccadic memory, updating and/or perception, including medial occipital, dorsomedial posterior parietal, and dorsal frontal cortex. Searching within these regions, we then employed a feature contrast (Orientation vs. Shape change). This contrast revealed feature-specific modulations (consistent with shape change enhancement) in left medial occipital cortex. The peak site (left cuneus) showed contralateral functional connectivity with early visual cortex (lingual gyrus), object-processing areas (occipitotemporal cortex) and saccade / motor areas in parietal cortex. These observations show that medial occipital cortex participates in a cortical network involved in transsaccadic feature perception. Together with the previous literature, this suggests separate mechanisms for transsaccadic perception of intrinsic object features (spatial frequency, shape) versus object location and orientation.

Evaluation of the expediency of using thermal i magery data for decryption exogenous processes and vegetation

2018 ◽  
Vol 933 (3) ◽  
pp. 52-62
Author(s):  
V.S. Tikunov ◽  
I.A. Rylskiy ◽  
S.B. Lukatzkiy
Keyword(s):  
Spatial Data ◽  
Laser Scanning ◽  
Data Extraction ◽  
Spectral Band ◽  
Information Provision ◽  
Lidar Data ◽  
Thermal Imagery ◽  
Scanning Lidar ◽  
Field Works ◽  
Object Features

Innovative methods of aerial surveys changed approaches to information provision of projecting dramatically in last years. Nowadays there are several methods pretending to be the most efficient for collecting geospatial data intended for projecting – airborne laser scanning (LIDAR) data, RGB aerial imagery (forming 3D pointclouds) and orthoimages. Thermal imagery is one of the additional methods that can be used for projecting. LIDAR data is precise, it allows us to measure relief even under the vegetation, or to collect laser re-flections from wires, metal constructions and poles. Precision and completeness of the DEM, produced from LIDAR data, allows to define relief microforms. Airborne imagery (visual spectrum) is very widespread and can be easily depicted. Thermal images are more strange and less widespread, they use different way of image forming, and spectral features of ob-jects can vary in specific ways. Either way, the additional spectral band can be useful for achieving additional spatial data and different object features, it can minimize field works. Here different aspects of thermal imagery are described in comparison with RGB (visual) images, LIDAR data and GIS layers. The attempt to estimate the feasibility of thermal imag-es for new data extraction is made.

scholarly journals Customized depolarization spatial patterns with dynamic retardance functions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
David Marco ◽  
Guadalupe López-Morales ◽  
María del Mar Sánchez-López ◽  
Ángel Lizana ◽  
Ignacio Moreno ◽  
...  
Keyword(s):  
Spatial Patterns ◽  
Detection System ◽  
Temporal Integration ◽  
Matrix Decomposition ◽  
Decomposition Methods ◽  
Time Dependent ◽  
Light Modulator ◽  
Dynamical Time ◽  
Depolarization Effect ◽  
Spatially Variant

AbstractIn this work we demonstrate customized depolarization spatial patterns by imaging a dynamical time-dependent pixelated retarder. A proof-of-concept of the proposed method is presented, where a liquid–crystal spatial light modulator is used as a spatial retarder that emulates a controlled spatially variant depolarizing sample by addressing a time-dependent phase pattern. We apply an imaging Mueller polarimetric system based on a polarization camera to verify the effective depolarization effect. Experimental validation is provided by temporal integration on the detection system. The effective depolarizance results are fully described within a simple graphical approach which agrees with standard Mueller matrix decomposition methods. The potential of the method is discussed by means of three practical cases, which include non-reported depolarization spatial patterns, including exotic structures as a spirally shaped depolarization pattern.

scholarly journals Generation of terahertz vector beams using dielectric metasurfaces via spin-decoupled phase control

Nanophotonics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 3393-3402 ◽  
Author(s):  
Yuehong Xu ◽  
Huifang Zhang ◽  
Quan Li ◽  
Xueqian Zhang ◽  
Quan Xu ◽  
...  
Keyword(s):  
High Performance ◽  
Special Kind ◽  
Phase Control ◽  
High Resolution Imaging ◽  
Plasmon Excitation ◽  
Bessel Beams ◽  
Dynamic Phase ◽  
Vector Beams ◽  
Resolution Imaging ◽  
Spatially Variant

AbstractCylindrical vector beams (CVBs), being a special kind of beams with spatially variant states of polarizations, are promising in photonics applications, including high-resolution imaging, plasmon excitation, optical trapping, and laser machining. Recently, generating CVBs using metasurfaces has drawn enormous interest owing to their highly designable, multifunctional, and integratable features. However, related studies remain unexplored in the terahertz regime. Here, a generic method for efficiently generating terahertz CVBs carrying orbital angular momentums (OAMs) is proposed and experimentally demonstrated using transmission-type spatial-variant dielectric metasurfaces, which is realized by designing the interference between the two circularly polarized transmission components. This method is based on spin-decoupled phase control allowed by simultaneously manipulating the dynamic phase and geometric phase of each structure, endowing more degree of freedom in designing the vector beams. Two types of metasurfaces which respectively generate polarization-dependent terahertz vector vortex beams (VVBs) and vector Bessel beams (VBBs) are experimentally characterized. The proposed method opens a new window to generate versatile vector beams, providing new capabilities in developing novel, compact, and high-performance devices applicable to broad electromagnetic spectral regimes.

scholarly journals Developing Objective Operational Definitions for Monitoring Drought

2009 ◽  
Vol 48 (6) ◽  
pp. 1217-1229 ◽  
Author(s):  
Steven M. Quiring
Keyword(s):  
Water Conservation ◽  
Standardized Precipitation Index ◽  
Meteorological Drought ◽  
Severity Index ◽  
Decision Makers ◽  
Drought Severity ◽  
Specific Method ◽  
The Standardized Precipitation Index ◽  
Spatially Variant ◽  
Objective Methodology

Abstract Drought is a complex phenomenon that is difficult to accurately describe because its definition is both spatially variant and context dependent. Decision makers in local, state, and federal agencies commonly use operational drought definitions that are based on specific drought index thresholds to trigger water conservation measures and determine levels of drought assistance. Unfortunately, many state drought plans utilize operational drought definitions that are derived subjectively and therefore may not be appropriate for triggering drought responses. This paper presents an objective methodology for establishing operational drought definitions. The advantages of this methodology are demonstrated by calculating meteorological drought thresholds for the Palmer drought severity index, the standardized precipitation index, and percent of normal precipitation using both station and climate division data from Texas. Results indicate that using subjectively derived operational drought definitions may lead to over- or underestimating true drought severity. Therefore, it is more appropriate to use an objective location-specific method for defining operational drought thresholds.

A SAR sidelobe suppression algorithm based on modified spatially variant apodization

2010 ◽  
Vol 53 (9) ◽  
pp. 2542-2551 ◽  
Author(s):  
Chong Ni ◽  
YanFei Wang ◽  
XiangHui Xu ◽  
ChangYi Zhou ◽  
PengFei Cui
Keyword(s):  
Sidelobe Suppression ◽  
Spatially Variant
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