337 research outputs found
Learning Action Translator for Meta Reinforcement Learning on Sparse-Reward Tasks
Meta reinforcement learning (meta-RL) aims to learn a policy solving a set of
training tasks simultaneously and quickly adapting to new tasks. It requires
massive amounts of data drawn from training tasks to infer the common structure
shared among tasks. Without heavy reward engineering, the sparse rewards in
long-horizon tasks exacerbate the problem of sample efficiency in meta-RL.
Another challenge in meta-RL is the discrepancy of difficulty level among
tasks, which might cause one easy task dominating learning of the shared policy
and thus preclude policy adaptation to new tasks. This work introduces a novel
objective function to learn an action translator among training tasks. We
theoretically verify that the value of the transferred policy with the action
translator can be close to the value of the source policy and our objective
function (approximately) upper bounds the value difference. We propose to
combine the action translator with context-based meta-RL algorithms for better
data collection and more efficient exploration during meta-training. Our
approach empirically improves the sample efficiency and performance of meta-RL
algorithms on sparse-reward tasks.Comment: Published in AAAI 202
Federated Learning Attacks and Defenses: A Survey
In terms of artificial intelligence, there are several security and privacy
deficiencies in the traditional centralized training methods of machine
learning models by a server. To address this limitation, federated learning
(FL) has been proposed and is known for breaking down ``data silos" and
protecting the privacy of users. However, FL has not yet gained popularity in
the industry, mainly due to its security, privacy, and high cost of
communication. For the purpose of advancing the research in this field,
building a robust FL system, and realizing the wide application of FL, this
paper sorts out the possible attacks and corresponding defenses of the current
FL system systematically. Firstly, this paper briefly introduces the basic
workflow of FL and related knowledge of attacks and defenses. It reviews a
great deal of research about privacy theft and malicious attacks that have been
studied in recent years. Most importantly, in view of the current three
classification criteria, namely the three stages of machine learning, the three
different roles in federated learning, and the CIA (Confidentiality, Integrity,
and Availability) guidelines on privacy protection, we divide attack approaches
into two categories according to the training stage and the prediction stage in
machine learning. Furthermore, we also identify the CIA property violated for
each attack method and potential attack role. Various defense mechanisms are
then analyzed separately from the level of privacy and security. Finally, we
summarize the possible challenges in the application of FL from the aspect of
attacks and defenses and discuss the future development direction of FL
systems. In this way, the designed FL system has the ability to resist
different attacks and is more secure and stable.Comment: IEEE BigData. 10 pages, 2 figures, 2 table
HPLFlowNet: Hierarchical Permutohedral Lattice FlowNet for Scene Flow Estimation on Large-scale Point Clouds
We present a novel deep neural network architecture for end-to-end scene flow
estimation that directly operates on large-scale 3D point clouds. Inspired by
Bilateral Convolutional Layers (BCL), we propose novel DownBCL, UpBCL, and
CorrBCL operations that restore structural information from unstructured point
clouds, and fuse information from two consecutive point clouds. Operating on
discrete and sparse permutohedral lattice points, our architectural design is
parsimonious in computational cost. Our model can efficiently process a pair of
point cloud frames at once with a maximum of 86K points per frame. Our approach
achieves state-of-the-art performance on the FlyingThings3D and KITTI Scene
Flow 2015 datasets. Moreover, trained on synthetic data, our approach shows
great generalization ability on real-world data and on different point
densities without fine-tuning
Topological Transformation and Free-Space Transport of Photonic Hopfions
Structured light fields embody strong spatial variations of polarisation,
phase and amplitude. Understanding, characterization and exploitation of such
fields can be achieved through their topological properties. Three-dimensional
(3D) topological solitons, such as hopfions, are 3D localized continuous field
configurations with nontrivial particle-like structures, that exhibit a host of
important topologically protected properties. Here, we propose and demonstrate
photonic counterparts of hopfions with exact characteristics of Hopf fibration,
Hopf index, and Hopf mapping from real-space vector beams to homotopic
hyperspheres representing polarisation states. We experimentally generate
photonic hopfions with on-demand high-order Hopf indices and independently
controlled topological textures, including N\'eel-, Bloch-, and anti-skyrmionic
types. We also demonstrate a robust free-space transport of photonic hopfions,
thus, showing potential of hopfions for developing optical topological
informatics and communications
A Coarse-to-fine Framework for Automated Kidney and Kidney Tumor Segmentation from Volumetric CT Images
Automatic semantic segmentation of kidney and kidney tumor is a promising tool for the treatment of kidney cancer. Due to the wide variety in kidney and kidney tumor morphology, it is still a great challenge to complete accurate segmentation of kidney and kidney tumor. We propose a new framework based on our previous work accepted by MICCAI2019, which is a coarse-to-fine segmentation framework to realize accurate and fast segmentation of kidney and kidney tumor
The inner nuclear membrane protein NEMP1 supports nuclear envelope openings and enucleation of erythroblasts
Nuclear envelope membrane proteins (NEMPs) are a conserved family of nuclear envelope (NE) proteins that reside within the inner nuclear membrane (INM). Even though Nemp1 knockout (KO) mice are overtly normal, they display a pronounced splenomegaly. This phenotype and recent reports describing a requirement for NE openings during erythroblasts terminal maturation led us to examine a potential role for Nemp1 in erythropoiesis. Here, we report that Nemp1 KO mice show peripheral blood defects, anemia in neonates, ineffective erythropoiesis, splenomegaly, and stress erythropoiesis. The erythroid lineage of Nemp1 KO mice is overrepresented until the pronounced apoptosis of polychromatophilic erythroblasts. We show that NEMP1 localizes to the NE of erythroblasts and their progenitors. Mechanistically, we discovered that NEMP1 accumulates into aggregates that localize near or at the edge of NE openings and Nemp1 deficiency leads to a marked decrease of both NE openings and ensuing enucleation. Together, our results for the first time demonstrate that NEMP1 is essential for NE openings and erythropoietic maturation in vivo and provide the first mouse model of defective erythropoiesis directly linked to the loss of an INM protein
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