Real-time Semantic Segmentation of Crop and Weed for Precision Agriculture Robots Leveraging Background Knowledge in CNNs

Precision farming robots, which target to reduce the amount of herbicides that need to be brought out in the fields, must have the ability to identify crops and weeds in real time to trigger weeding actions. In this paper, we address the problem of CNN-based semantic segmentation of crop fields separating sugar beet plants, weeds, and background solely based on RGB data. We propose a CNN that exploits existing vegetation indexes and provides a classification in real time. Furthermore, it can be effectively re-trained to so far unseen fields with a comparably small amount of training data. We implemented and thoroughly evaluated our system on a real agricultural robot operating in different fields in Germany and Switzerland. The results show that our system generalizes well, can operate at around 20Hz, and is suitable for online operation in the fields.Comment: Accepted for publication at IEEE International Conference on Robotics and Automation 2018 (ICRA 2018

Toward robust algebraic multigrid methods for nonsymmetric problems

When analyzing symmetric problems and the methods for solving them, multigrid and algebraic multigrid in particular, one of the primary tools at the analyst's disposal is the energy norm associated with the problem. The lack of this tool is one of the many reasons analysis of nonsymmetric problems and methods for solving them is substantially more difficult than in the symmetric case. We show that there is an analog to the energy norm for a nonsymmetric matrix A, associated with a new absolute value we term the "form" absolute value. This new absolute value can be described as a symmetric positive definite solution to the matrix equation A*|A|-1A = |A|; it exists and is unique in particular whenever A has positive symmetric part. We then develop a novel convergence theory for a general two-level multigrid iteration for any such A, making use of the form absolute value. In particular, we derive a convergence bound in terms of a smoothing property and separate approximation properties for the interpolation and restriction (a novel feature). Finally, we present new algebraic multigrid heuristics designed specifically targeting this new theory, which we evaluate with numerical tests

Alveolar Epithelial Type II Cell Metabolism in Health, Hypoxia and Disease

Alveolar epithelial type II (ATII) cells constitute 50% of cells composing the alveolar epithelium and are essential to proper lung function. They are the primary producers of pulmonary surfactant, serve as progenitors capable of rapid self-renewal and differentiation, and play roles in immunity and fluid homeostasis, all of which require considerable energy investment. Given their many ATP-demanding functions, ATII cells are expected to be highly metabolically active; however, little is known about the fundamental metabolism of this critical cell type. ATII cells are normally exposed to uniquely high oxygen concentrations. However, numerous lung diseases including idiopathic pulmonary fibrosis (IPF) lead to pulmonary hypoxia. The role of hypoxia has been extensively investigated in pathologies like cancer and heart disease but has received far less attention in pulmonary disease. Recent findings of lactic acid build-up in IPF lung suggest a role for altered cell metabolism, potentially related to hypoxia. We investigate the hypothesis that hypoxia alters ATII metabolism, and that similar metabolic change occurs in IPF lung. ATII metabolism was characterized under ambient versus 1.5% O2. Additionally, to understand possible contributions of ATII to lactic acid build-up in disease, the ability of healthy cells to both produce and consume lactate was assessed. Extracellular flux analysis was performed to measure glycolytic and mitochondrial metabolism in a model cell line and ATII isolated from mouse and human lungs, and flux experiments were correlated with metabolite measurements and gene and protein expression. This work demonstrates that ATII cells are highly metabolic and dependent on mitochondrial metabolism. Hypoxia suppresses ATII mitochondrial metabolism without concurrent change in glycolysis, despite enhanced enzyme expression. Similarly, ATII from IPF patient lung showed low mitochondrial function compared to control, while glycolytic output occurred at near-control rates or higher, generating a highly glycolytic phenotype. In both hypoxia-treated and IPF-derived ATII, reserve mitochondrial capacity was maintained. Additionally, we demonstrate that ATII consume lactate and that this ability is limited by hypoxia. Based on our findings, we propose a hypothetical model by which metabolic cooperation between ATII and other cell types is altered in IPF to favor enhanced lactic acid generation and reduced consumption