Feed-Forward Segmentation of Figure-Ground and Assignment of Border-Ownership

Figure-ground is the segmentation of visual information into objects and their surrounding backgrounds. Two main processes herein are boundary assignment and surface segregation, which rely on the integration of global scene information. Recurrent processing either by intrinsic horizontal connections that connect surrounding neurons or by feedback projections from higher visual areas provide such information, and are considered to be the neural substrate for figure-ground segmentation. On the contrary, a role of feedforward projections in figure-ground segmentation is unknown. To have a better understanding of a role of feedforward connections in figure-ground organization, we constructed a feedforward spiking model using a biologically plausible neuron model. By means of surround inhibition our simple 3-layered model performs figure-ground segmentation and one-sided border-ownership coding. We propose that the visual system uses feed forward suppression for figure-ground segmentation and border-ownership assignment

Porous, Functionally Gradient Pyroelectric Materials.

Properties of a new type of pyroelectric ceramic structure containing a layer of known porosity laminated between two dense layers, to form a functionally gradient material (FGM), are reported. The combination of theoretical models for pyroelectric, dielectric, and thermal properties gave a model for the pyroelectric voltage figure of merit (FV) in good agreement with experiment, which had shown a 20% improvement for an introduced central layer porosity of 27%. Preliminary pyroelectric responsivity measurements on FGM infrared detectors indicated an even better improvement. It is postulated that this is due to the porous layer acting as a thermal barrier in the structure

Automatic Evaluation of Multi-Parameter Fluorescence Micrographs with a Neural Network Architecture

A neural network architecture for the automatic evaluation of uorescence microscopy images of tissue samples is presented. One image is segmented into regions of uorescent lymphocyte cell bodies and background. The system uses two kinds of neural nets to (i) detect the uorescent cells and (ii) compute a one-pixel wide contour line for each detected cell. Even though the cells contours show considerable variation and the have nonhomogenous uorescence signals across the cell body the system detects a minimum of 95% of the cells with less than 10% false positives, using human expert evaluation of the images as a reference. Keywords: shape recognition, contour grouping, uorescence microscopy, functional proteomics 1 Introduction In this work we present a system for the rapid and exact evaluation of multi-parameter uorescence images. The platform of our study is the evaluation of images of uorescent lymphocytes in a tissue sample to prove the presence of n cell surface proteins at ..

Dielectric measurements on high-Q ceramics in the microwave region

The postresonator method proposed by Hakki and Coleman for the measurement of dielectric properties of solids in the microwave region is reexamined. Based on the experiments performed around 10 GHz, the limitations of the method in loss determination for materials with tan delta < 5 x 10(-4) are outlined. Alternative techniques for studying high-Q materials are described. Loss measurements performed on well-prepared ceramics have been used to draw comparisons among these techniques. Some of the experimental findings are new and are reported for the first time

Statistical electric field and switching time distributions in PZT 1Nb2Sr ceramics: Crystal- and microstructure effects

Dispersive polarization response of ferroelectric PZT ceramics is analyzed assuming theinhomogeneous field mechanism of polarization switching. In terms of this model, the localpolarization switching proceeds according to the Kolmogorov-Avrami-Ishibashi scenario with theswitching time determined by the local electric field. As a result, the total polarization reversal isdominated by the statistical distribution of the local field magnitudes. Microscopic parameters of thismodel (the high-field switching time and the activation field) as well as the statistical field andconsequent switching time distributions due to disorder at a mesoscopic scale can be directlydetermined from a set of experiments measuring the time dependence of the total polarizationswitching, when applying electric fields of different magnitudes. PZT 1Nb2Sr ceramics with Zr/Tiratios 51.5/48.5, 52.25/47.75, and 60/40 with four different grain sizes each were analyzed followingthis approach. Pronounced differences of field and switching time distributions were founddepending on the Zr/Ti ratios. Varying grain size also affects polarization reversal parameters, but inanother way. The field distributions remain almost constant with grain size whereas switching timesand activation field tend to decrease with increasing grain size. The quantitative changes of the latterparameters with grain size are very different depending on composition. The origin of the effects onthe field and switching time distributions are related to differences in structural and microstructuralcharacteristics of the materials and are discussed with respect to the hysteresis loops observed underbipolar electrical cycling