16,592 research outputs found
Learning Robust Visual-Semantic Embedding for Generalizable Person Re-identification
Generalizable person re-identification (Re-ID) is a very hot research topic
in machine learning and computer vision, which plays a significant role in
realistic scenarios due to its various applications in public security and
video surveillance. However, previous methods mainly focus on the visual
representation learning, while neglect to explore the potential of semantic
features during training, which easily leads to poor generalization capability
when adapted to the new domain. In this paper, we propose a Multi-Modal
Equivalent Transformer called MMET for more robust visual-semantic embedding
learning on visual, textual and visual-textual tasks respectively. To further
enhance the robust feature learning in the context of transformer, a dynamic
masking mechanism called Masked Multimodal Modeling strategy (MMM) is
introduced to mask both the image patches and the text tokens, which can
jointly works on multimodal or unimodal data and significantly boost the
performance of generalizable person Re-ID. Extensive experiments on benchmark
datasets demonstrate the competitive performance of our method over previous
approaches. We hope this method could advance the research towards
visual-semantic representation learning. Our source code is also publicly
available at https://github.com/JeremyXSC/MMET
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Ensuring Access to Safe and Nutritious Food for All Through the Transformation of Food Systems
An iterative warping and clustering algorithm to estimate multiple wave-shape functions from a nonstationary oscillatory signal
Nonsinusoidal oscillatory signals are everywhere. In practice, the
nonsinusoidal oscillatory pattern, modeled as a 1-periodic wave-shape function
(WSF), might vary from cycle to cycle. When there are finite different WSFs,
, so that the WSF jumps from one to another suddenly, the
different WSFs and jumps encode useful information. We present an iterative
warping and clustering algorithm to estimate from a
nonstationary oscillatory signal with time-varying amplitude and frequency, and
hence the change points of the WSFs. The algorithm is a novel combination of
time-frequency analysis, singular value decomposition entropy and vector
spectral clustering. We demonstrate the efficiency of the proposed algorithm
with simulated and real signals, including the voice signal, arterial blood
pressure, electrocardiogram and accelerometer signal. Moreover, we provide a
mathematical justification of the algorithm under the assumption that the
amplitude and frequency of the signal are slowly time-varying and there are
finite change points that model sudden changes from one wave-shape function to
another one.Comment: 39 pages, 11 figure
Offline and Online Models for Learning Pairwise Relations in Data
Pairwise relations between data points are essential for numerous machine learning algorithms. Many representation learning methods consider pairwise relations to identify the latent features and patterns in the data. This thesis, investigates learning of pairwise relations from two different perspectives: offline learning and online learning.The first part of the thesis focuses on offline learning by starting with an investigation of the performance modeling of a synchronization method in concurrent programming using a Markov chain whose state transition matrix models pairwise relations between involved cores in a computer process.Then the thesis focuses on a particular pairwise distance measure, the minimax distance, and explores memory-efficient approaches to computing this distance by proposing a hierarchical representation of the data with a linear memory requirement with respect to the number of data points, from which the exact pairwise minimax distances can be derived in a memory-efficient manner. Then, a memory-efficient sampling method is proposed that follows the aforementioned hierarchical representation of the data and samples the data points in a way that the minimax distances between all data points are maximally preserved. Finally, the thesis proposes a practical non-parametric clustering of vehicle motion trajectories to annotate traffic scenarios based on transitive relations between trajectories in an embedded space.The second part of the thesis takes an online learning perspective, and starts by presenting an online learning method for identifying bottlenecks in a road network by extracting the minimax path, where bottlenecks are considered as road segments with the highest cost, e.g., in the sense of travel time. Inspired by real-world road networks, the thesis assumes a stochastic traffic environment in which the road-specific probability distribution of travel time is unknown. Therefore, it needs to learn the parameters of the probability distribution through observations by modeling the bottleneck identification task as a combinatorial semi-bandit problem. The proposed approach takes into account the prior knowledge and follows a Bayesian approach to update the parameters. Moreover, it develops a combinatorial variant of Thompson Sampling and derives an upper bound for the corresponding Bayesian regret. Furthermore, the thesis proposes an approximate algorithm to address the respective computational intractability issue.Finally, the thesis considers contextual information of road network segments by extending the proposed model to a contextual combinatorial semi-bandit framework and investigates and develops various algorithms for this contextual combinatorial setting
A Design Science Research Approach to Smart and Collaborative Urban Supply Networks
Urban supply networks are facing increasing demands and challenges and thus constitute a relevant field for research and practical development. Supply chain management holds enormous potential and relevance for society and everyday life as the flow of goods and information are important economic functions. Being a heterogeneous field, the literature base of supply chain management research is difficult to manage and navigate. Disruptive digital technologies and the implementation of cross-network information analysis and sharing drive the need for new organisational and technological approaches. Practical issues are manifold and include mega trends such as digital transformation, urbanisation, and environmental awareness.
A promising approach to solving these problems is the realisation of smart and collaborative supply networks. The growth of artificial intelligence applications in recent years has led to a wide range of applications in a variety of domains. However, the potential of artificial intelligence utilisation in supply chain management has not yet been fully exploited. Similarly, value creation increasingly takes place in networked value creation cycles that have become continuously more collaborative, complex, and dynamic as interactions in business processes involving information technologies have become more intense.
Following a design science research approach this cumulative thesis comprises the development and discussion of four artefacts for the analysis and advancement of smart and collaborative urban supply networks. This thesis aims to highlight the potential of artificial intelligence-based supply networks, to advance data-driven inter-organisational collaboration, and to improve last mile supply network sustainability. Based on thorough machine learning and systematic literature reviews, reference and system dynamics modelling, simulation, and qualitative empirical research, the artefacts provide a valuable contribution to research and practice
Thermodynamic Assessment and Optimisation of Supercritical and Transcritical Power Cycles Operating on CO2 Mixtures by Means of Artificial Neural Networks
Feb 21, 2022 to Feb 24, 2022, San Antonio, TX, United StatesClosed supercritical and transcritical power cycles operating on Carbon Dioxide have proven to be a promising technology for power generation and, as such, they are being researched by numerous international projects today. Despite the advantageous features of these cycles enabling very high efficiencies in intermediate temperature applications, the major shortcoming of the technology is a strong dependence on ambient temperature; in order to perform compression near the CO2 critical point (31ºC), low ambient temperatures are needed. This is particularly challenging in Concentrated Solar Power applications, typically found in hot, semi-arid locations.
To overcome this limitation, the SCARABEUS project explores the idea of blending raw carbon dioxide with small amounts of certain dopants in order to shift the critical temperature of the resulting working fluid to higher values, hence enabling gaseous compression near the critical point or even liquid compression regardless of a high ambient temperature. Different dopants have been studied within the project so far (i.e. C6F6, TiCl4 and SO2) but the final selection will have to account for trade-offs between thermodynamic performance, economic metrics and system reliability.
Bearing all this in mind, the present paper deals with the development of a non-physics-based model using Artificial Neural Networks (ANN), developed using Matlab’s Deep Learning Toolbox, to enable SCARABEUS system optimisation without running the detailed – and extremely time consuming – thermal models, developed with Thermoflex and Matlab software.
In the first part of the paper, the candidate dopants and cycle layouts are presented and discussed, and a thorough description of the ANN training methodology is provided, along with all the main assumptions and hypothesis made.
In the second part of the manuscript, results confirms that the ANN is a reliable tool capable of successfully reproducing the detailed Thermoflex model, estimating the cycle thermal efficiency with a Root Mean Square Error lower than 0.2 percentage points. Furthermore, the great advantage of using the Artificial Neural Network proposed is demonstrated by the huge reduction in the computational time needed, up to 99% lower than the one consumed by the detailed model. Finally, the high flexibility and versatility of the ANN is shown, applying this tool in different scenarios and estimating different cycle thermal efficiency for a great variety of boundary conditions.Unión Europea H2020-81498
Accelerated Sparse Recovery via Gradient Descent with Nonlinear Conjugate Gradient Momentum
This paper applies an idea of adaptive momentum for the nonlinear conjugate
gradient to accelerate optimization problems in sparse recovery. Specifically,
we consider two types of minimization problems: a (single) differentiable
function and the sum of a non-smooth function and a differentiable function. In
the first case, we adopt a fixed step size to avoid the traditional line search
and establish the convergence analysis of the proposed algorithm for a
quadratic problem. This acceleration is further incorporated with an operator
splitting technique to deal with the non-smooth function in the second case. We
use the convex and the nonconvex functionals as two
case studies to demonstrate the efficiency of the proposed approaches over
traditional methods
Universal Private Estimators
We present \textit{universal} estimators for the statistical mean, variance,
and scale (in particular, the interquartile range) under pure differential
privacy. These estimators are universal in the sense that they work on an
arbitrary, unknown continuous distribution over ,
while yielding strong utility guarantees except for ill-behaved .
For certain distribution families like Gaussians or heavy-tailed distributions,
we show that our universal estimators match or improve existing estimators,
which are often specifically designed for the given family and under \textit{a
priori} boundedness assumptions on the mean and variance of . This
is the first time these boundedness assumptions are removed under pure
differential privacy. The main technical tools in our development are
instance-optimal empirical estimators for the mean and quantiles over the
unbounded integer domain, which can be of independent interest
A Hierarchical Game-Theoretic Decision-Making for Cooperative Multi-Agent Systems Under the Presence of Adversarial Agents
Underlying relationships among Multi-Agent Systems (MAS) in hazardous
scenarios can be represented as Game-theoretic models. This paper proposes a
new hierarchical network-based model called Game-theoretic Utility Tree (GUT),
which decomposes high-level strategies into executable low-level actions for
cooperative MAS decisions. It combines with a new payoff measure based on agent
needs for real-time strategy games. We present an Explore game domain, where we
measure the performance of MAS achieving tasks from the perspective of
balancing the success probability and system costs. We evaluate the GUT
approach against state-of-the-art methods that greedily rely on rewards of the
composite actions. Conclusive results on extensive numerical simulations
indicate that GUT can organize more complex relationships among MAS
cooperation, helping the group achieve challenging tasks with lower costs and
higher winning rates. Furthermore, we demonstrated the applicability of the GUT
using the simulator-hardware testbed - Robotarium. The performances verified
the effectiveness of the GUT in the real robot application and validated that
the GUT could effectively organize MAS cooperation strategies, helping the
group with fewer advantages achieve higher performance.Comment: This paper is accepted by the ACM Symposium on Applied Computing
(SAC) 2023 Technical Track on Intelligent Robotics and Multi-Agent Systems
(IRMAS
Machine-learning detection of the Berezinskii-Kosterlitz-Thouless transition and the second-order phase transition in the XXZ models
We propose two machine-learning methods based on neural networks, which we
respectively call the phase-classification method and the
temperature-identification method, for detecting different types of phase
transitions in the XXZ models without prior knowledge of their critical
temperatures. The XXZ models have exchange couplings which are anisotropic in
the spin space where the strength is represented by a parameter .
The models exhibit the second-order phase transition when , whereas
the Berezinskii-Kosterlitz-Thouless (BKT) phase transition when . In
the phase-classification method, the neural network is trained using spin or
vortex configurations of well-known classical spin models other than the XXZ
models, e.g., the Ising models and the XY models, to classify those of the XXZ
models to corresponding phases. We demonstrate that the trained neural network
successfully detects the phase transitions for both and ,
and the evaluated critical temperatures coincide well with those evaluated by
conventional numerical calculations. In the temperature-identification method,
on the other hand, the neural network is trained so as to identify temperatures
at which the input spin or vortex configurations are generated by the Monte
Carlo thermalization. The critical temperatures are evaluated by analyzing the
optimized weight matrix, which coincide with the result of numerical
calculation for the second-order phase transition in the Ising-like XXZ model
with but cannot be determined uniquely for the BKT transition in
the XY-like XXZ model with .Comment: 17 pages, 12 figure
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