Detection of tomatoes using spectral-spatial methods in remotely sensed RGB images captured by UAV

The spectral-spatial classification of high spatial resolution RGB images obtained from unmanned aerial vehicles (UAVs) for detection of tomatoes in the image is presented. Bayesian information criterion (BIC) was used to determine the optimal number of clusters for the image. Spectral clustering was carried out using K-means, expectation maximisation (EM) and self-organising map (SOM) algorithms to categorise the pixels into two groups i.e. tomatoes and non-tomatoes. Due to resemblance in spectral intensities, some of the non-tomato pixels were grouped into the tomato group and in order to remove them, spatial segmentation was performed on the image. Spatial segmentation was carried out using morphological operations and by setting thresholds for geometrical properties. The number of pixels grouped in the tomato cluster is different for each clustering method. EM doesn't pick up the land patches as tomato pixels. As a result, the size of the tomatoes picked up is different than K-means and SOM. Since threshold values chosen for carrying out spatial segmentation are shape and size dependent, different threshold values are applied to different methods of clustering. A synthetic image of 12 x 12 pixels with different labels is created to illustrate the effect of each method used for spatial segmentation on the clustered image. Two representative UAV images captured at different heights from the ground were used to demonstrate the performance of the proposed method. Results and comparison of performance parameters of different spectral-spatial classification methods were presented. It is observed that EM performed better than K-means and SOM. (C) 2015 IAgrE. Published by Elsevier Ltd. All rights reserved

InAs-Al Hybrid Devices Passing the Topological Gap Protocol

We present measurements and simulations of semiconductor-superconductor heterostructure devices that are consistent with the observation of topological superconductivity and Majorana zero modes. The devices are fabricated from high-mobility two-dimensional electron gases in which quasi-one-dimensional wires are defined by electrostatic gates. These devices enable measurements of local and non-local transport properties and have been optimized via extensive simulations for robustness against non-uniformity and disorder. Our main result is that several devices, fabricated according to the design's engineering specifications, have passed the topological gap protocol defined in Pikulin {\it et al.}\ [arXiv:2103.12217]. This protocol is a stringent test composed of a sequence of three-terminal local and non-local transport measurements performed while varying the magnetic field, semiconductor electron density, and junction transparencies. Passing the protocol indicates a high probability of detection of a topological phase hosting Majorana zero modes. Our experimental results are consistent with a quantum phase transition into a topological superconducting phase that extends over several hundred millitesla in magnetic field and several millivolts in gate voltage, corresponding to approximately one hundred micro-electron-volts in Zeeman energy and chemical potential in the semiconducting wire. These regions feature a closing and re-opening of the bulk gap, with simultaneous zero-bias conductance peaks at {\it both} ends of the devices that withstand changes in the junction transparencies. The measured maximum topological gaps in our devices are 20-$30\,\mu$eV. This demonstration is a prerequisite for experiments involving fusion and braiding of Majorana zero modes.Comment: Fixed typos. Fig. 3 is now readable by Adobe Reade