110 research outputs found
Sample4Geo: Hard Negative Sampling For Cross-View Geo-Localisation
Cross-View Geo-Localisation is still a challenging task where additional
modules, specific pre-processing or zooming strategies are necessary to
determine accurate positions of images. Since different views have different
geometries, pre-processing like polar transformation helps to merge them.
However, this results in distorted images which then have to be rectified.
Adding hard negatives to the training batch could improve the overall
performance but with the default loss functions in geo-localisation it is
difficult to include them. In this article, we present a simplified but
effective architecture based on contrastive learning with symmetric InfoNCE
loss that outperforms current state-of-the-art results. Our framework consists
of a narrow training pipeline that eliminates the need of using aggregation
modules, avoids further pre-processing steps and even increases the
generalisation capability of the model to unknown regions. We introduce two
types of sampling strategies for hard negatives. The first explicitly exploits
geographically neighboring locations to provide a good starting point. The
second leverages the visual similarity between the image embeddings in order to
mine hard negative samples. Our work shows excellent performance on common
cross-view datasets like CVUSA, CVACT, University-1652 and VIGOR. A comparison
between cross-area and same-area settings demonstrate the good generalisation
capability of our model
Orientation-Guided Contrastive Learning for UAV-View Geo-Localisation
Retrieving relevant multimedia content is one of the main problems in a world
that is increasingly data-driven. With the proliferation of drones, high
quality aerial footage is now available to a wide audience for the first time.
Integrating this footage into applications can enable GPS-less geo-localisation
or location correction.
In this paper, we present an orientation-guided training framework for
UAV-view geo-localisation. Through hierarchical localisation orientations of
the UAV images are estimated in relation to the satellite imagery. We propose a
lightweight prediction module for these pseudo labels which predicts the
orientation between the different views based on the contrastive learned
embeddings. We experimentally demonstrate that this prediction supports the
training and outperforms previous approaches. The extracted pseudo-labels also
enable aligned rotation of the satellite image as augmentation to further
strengthen the generalisation. During inference, we no longer need this
orientation module, which means that no additional computations are required.
We achieve state-of-the-art results on both the University-1652 and
University-160k datasets
Dimensional analysis of droplet size and ligament length during high-speed rotary bell atomization
Modern spray-coating processes are based on high-volume, low-pressure, airless atomization or high-speed rotary bell atomization, often assisted by electrostatic charging to increase the transfer efficiency. The process from the liquid film flow beneath the bell, through ligament formation and consecutive disintegration to droplet deposition, has been constantly explored during the evolution of automotive spray coating. This work proposes a set of dimensionless groups that fully describe the process from film flow to ligament disintegration, including shear and elongational flow effects during atomization of particle laden, shear thinning, viscoelastic fluids
Analysis of Paint Flow Pulsations during High-Speed Rotary Bell Atomization
High-speed rotary bell atomization is the preeminent coating technique in the automotive industry. It is widely accepted that a narrow droplet size distribution and constant spray are necessary in order to guarantee uniform film thickness and high-quality appearance. This may be deteriorated by paint flow pulsations. So far, however, no studies exist regarding such fluctuations quantitatively for this type of atomizers. We fill this gap using image analysis of high-speed recordings close to the bell edge. We could show that the fundamental pulsation frequency increases linearly with rotational speed. A ratio of pulsation frequency and true rotational speed of about 3 was found, indicating that pulsations were initiated mainly by the three struts of the distributor disc. The coefficient of variation, i.e., the amplitude of fluctuation increased with decreasing liquid volume rate and rotational speed. Beyond that, we could show that the formation of droplets larger than 100 μm, which are assumed to cause paint defects, is promoted by the degree of fluctuation. These findings may stimulate development of bell cups showing less paint flow pulsations
NeRFtrinsic Four: An End-To-End Trainable NeRF Jointly Optimizing Diverse Intrinsic and Extrinsic Camera Parameters
Novel view synthesis using neural radiance fields (NeRF) is the
state-of-the-art technique for generating high-quality images from novel
viewpoints. Existing methods require a priori knowledge about extrinsic and
intrinsic camera parameters. This limits their applicability to synthetic
scenes, or real-world scenarios with the necessity of a preprocessing step.
Current research on the joint optimization of camera parameters and NeRF
focuses on refining noisy extrinsic camera parameters and often relies on the
preprocessing of intrinsic camera parameters. Further approaches are limited to
cover only one single camera intrinsic. To address these limitations, we
propose a novel end-to-end trainable approach called NeRFtrinsic Four. We
utilize Gaussian Fourier features to estimate extrinsic camera parameters and
dynamically predict varying intrinsic camera parameters through the supervision
of the projection error. Our approach outperforms existing joint optimization
methods on LLFF and BLEFF. In addition to these existing datasets, we introduce
a new dataset called iFF with varying intrinsic camera parameters. NeRFtrinsic
Four is a step forward in joint optimization NeRF-based view synthesis and
enables more realistic and flexible rendering in real-world scenarios with
varying camera parameters
Secure and Efficient Masking of AES - A Mission Impossible?
This document discusses masking approaches with a special focus on the AES S-box. Firstly, we discuss previously presented masking schemes with respect to their security and implementation. We conclude that algorithmic countermeasures to secure the AES algorithm
against side-channel attacks have not been resistant against all
first-order side-channel attacks.
Secondly, we introduce a new masking countermeasure which is not only secure against first-order side-channel attacks, but which also leads to relatively small implementations compared to other masking schemes when implemented in dedicated hardware
Impact of Antimalarial Treatment and Chemoprevention on the Drug Sensitivity of Malaria Parasites Isolated from Ugandan Children
Changing treatment practices may be selecting for changes in the drug sensitivity of malaria parasites. We characterized ex vivo drug sensitivity and parasite polymorphisms associated with sensitivity in 459 Plasmodium falciparum samples obtained from subjects enrolled in two clinical trials in Tororo, Uganda, from 2010 to 2013. Sensitivities to chloroquine and monodesethylamodiaquine varied widely; sensitivities to quinine, dihydroartemisinin, lumefantrine, and piperaquine were generally good. Associations between ex vivo drug sensitivity and parasite polymorphisms included decreased chloroquine and monodesethylamodiaquine sensitivity and increased lumefantrine and piperaquine sensitivity with pfcrt 76T, as well as increased lumefantrine sensitivity with pfmdr1 86Y, Y184, and 1246Y. Over time, ex vivo sensitivity decreased for lumefantrine and piperaquine and increased for chloroquine, the prevalences of pfcrt K76 and pfmdr1 N86 and D1246 increased, and the prevalences of pfdhfr and pfdhps polymorphisms associated with antifolate resistance were unchanged. In recurrent infections, recent prior treatment with artemether-lumefantrine was associated with decreased ex vivo lumefantrine sensitivity and increased prevalence of pfcrt K76 and pfmdr1 N86, 184F, and D1246. In children assigned chemoprevention with monthly dihydroartemisinin-piperaquine with documented circulating piperaquine, breakthrough infections had increased the prevalence of pfmdr1 86Y and 1246Y compared to untreated controls. The noted impacts of therapy and chemoprevention on parasite polymorphisms remained significant in multivariate analysis correcting for calendar time. Overall, changes in parasite sensitivity were consistent with altered selective pressures due to changing treatment practices in Uganda. These changes may threaten the antimalarial treatment and preventive efficacies of artemether-lumefantrine and dihydroartemisinin-piperaquine, respectively
Ateriovenous subclavia-shunt for head and neck reconstruction
Reconstruction of the facial hard- and soft tissues is of special concern for the rehabilitation of patients especially after ablative tumor surgery has been performed. Impaired soft and hard tissue conditions as a sequelae of extensive surgical resection and/or radiotherapy may impede common reconstruction methodes. Even free flaps may not be used without interposition of a vein graft as recipient vessels are not available as a consequence of radical neck dissection
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