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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

GVT-BDNet : Convolutional Neural Network with Global Voxel Transformer Operators for Building Damage Assessment / GVT-BDNet : Convolutional Neural Network med Global Voxel Transformer Operators för Building Damage Assessment

Remondini, Leonardo January 2021 (has links)
Natural disasters strike anywhere, disrupting local communication and transportation infrastructure, making the process of assessing specific local damage difficult, dangerous, and slow. The goal of Building Damage Assessment (BDA) is to quickly and accurately estimate the location, cause, and severity of the damage to maximize the efficiency of rescuers and saved lives. In current machine learning BDA solutions, attention operators are the most recent innovations adopted by researchers to increase generalizability and overall performances of Convolutional Neural Networks for the BDA task. However, the latter, nowadays exploit attention operators tailored to the specific task and specific neural network architecture, leading them to be hard to apply to other scenarios. In our research, we want to contribute to the BDA literature while also addressing this limitation. We propose Global Voxel Transformer Operators (GVTOs): flexible attention-operators originally proposed for Augmented Microscopy that can replace up-sampling, down-sampling, and size-preserving convolutions within either a U-Net or a general CNN architecture without any limitation. Dissimilar to local operators, like convolutions, GVTOs can aggregate global information and have input-specific weights during inference time, improving generalizability performance, as already proved by recent literature. We applied GVTOs on a state-of-the-art BDA model and named it GVT-BDNet. We trained and evaluated our proposal neural network on the xBD dataset; the largest and most complete dataset for BDA. We compared GVT-BDNet performance with the baseline architecture (BDNet) and observed that the former improves damaged buildings segmentation by a factor of 0.11. Moreover, GVT-BDNet achieves state-of-the-art performance on a 10% split of the xBD training dataset and on the xBD test dataset with an overall F1- score of 0.80 and 0.79, respectively. To evaluate the architecture consistency, we have also tested BDNet’s and GVT-BDNet’s generalizability performance on another segmentation task: Tree & Shadow segmentation. Results showed that both models achieved overall good performances, scoring an F1-score of 0.79 and 0.785, respectively. / Naturkatastrofer sker överallt, stör lokal kommunikations- och transportinfrastruktur, vilket gör bedömningsprocessen av specifika lokala skador svår, farlig och långsam. Målet med Building Damage Assessment (BDA) är att snabbt och precist uppskatta platsen, orsaken och allvarligheten av skadorna för att maximera effektiviteten av räddare och räddade liv. Nuvarande BDA-lösningar använder Convolutional Neural Network (CNN) och ad-hoc Attention Operators för att förbättra generaliseringsprestanda. Nyligen föreslagna attention operators är dock specifikt skräddarsydda för uppgiften och kan sakna flexibilitet för andra scenarier eller neural nätverksarkitektur. I vår forskning bidrar vi till BDA -litteraturen genom att föreslå Global Voxel Transformer Operators (GVTO): flexibla attention operators som kan appliceras på en CNN -arkitektur utan att vara bundna till en viss uppgift. Nyare litteratur visar dessutom att de kan öka utvinningen av global information och därmed generaliseringsprestanda. Vi tillämpade GVTO på en toppmodern CNN-modell för BDA. GVTO: er förbättrade skadessegmenteringsprestandan med en faktor av 0,11. Dessutom förbättrade de den senaste tekniken för xBD-testdatauppsättningen och nådde toppmodern prestanda på en 10% delning av xBD-träningsdatauppsättningen. Vi har också utvärderat generaliserbarheten av det föreslagna neurala nätverket på en annan segmenteringsuppgift (Tree Shadow segmentering), vilket uppnådde över lag bra prestationer.

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