16,226 research outputs found
The Metaverse: Survey, Trends, Novel Pipeline Ecosystem & Future Directions
The Metaverse offers a second world beyond reality, where boundaries are
non-existent, and possibilities are endless through engagement and immersive
experiences using the virtual reality (VR) technology. Many disciplines can
benefit from the advancement of the Metaverse when accurately developed,
including the fields of technology, gaming, education, art, and culture.
Nevertheless, developing the Metaverse environment to its full potential is an
ambiguous task that needs proper guidance and directions. Existing surveys on
the Metaverse focus only on a specific aspect and discipline of the Metaverse
and lack a holistic view of the entire process. To this end, a more holistic,
multi-disciplinary, in-depth, and academic and industry-oriented review is
required to provide a thorough study of the Metaverse development pipeline. To
address these issues, we present in this survey a novel multi-layered pipeline
ecosystem composed of (1) the Metaverse computing, networking, communications
and hardware infrastructure, (2) environment digitization, and (3) user
interactions. For every layer, we discuss the components that detail the steps
of its development. Also, for each of these components, we examine the impact
of a set of enabling technologies and empowering domains (e.g., Artificial
Intelligence, Security & Privacy, Blockchain, Business, Ethics, and Social) on
its advancement. In addition, we explain the importance of these technologies
to support decentralization, interoperability, user experiences, interactions,
and monetization. Our presented study highlights the existing challenges for
each component, followed by research directions and potential solutions. To the
best of our knowledge, this survey is the most comprehensive and allows users,
scholars, and entrepreneurs to get an in-depth understanding of the Metaverse
ecosystem to find their opportunities and potentials for contribution
A Spatio-temporal Decomposition Method for the Coordinated Economic Dispatch of Integrated Transmission and Distribution Grids
With numerous distributed energy resources (DERs) integrated into the
distribution networks (DNs), the coordinated economic dispatch (C-ED) is
essential for the integrated transmission and distribution grids. For large
scale power grids, the centralized C-ED meets high computational burden and
information privacy issues. To tackle these issues, this paper proposes a
spatio-temporal decomposition algorithm to solve the C-ED in a distributed and
parallel manner. In the temporal dimension, the multi-period economic dispatch
(ED) of transmission grid (TG) is decomposed to several subproblems by
introducing auxiliary variables and overlapping time intervals to deal with the
temporal coupling constraints. Besides, an accelerated alternative direction
method of multipliers (A-ADMM) based temporal decomposition algorithm with the
warm-start strategy, is developed to solve the ED subproblems of TG in
parallel. In the spatial dimension, a multi-parametric programming projection
based spatial decomposition algorithm is developed to coordinate the ED
problems of TG and DNs in a distributed manner. To further improve the
convergence performance of the spatial decomposition algorithm, the aggregate
equivalence approach is used for determining the feasible range of boundary
variables of TG and DNs. Moreover, we prove that the proposed spatio-temporal
decomposition method can obtain the optimal solution for bilevel convex
optimization problems with continuously differentiable objectives and
constraints. Numerical tests are conducted on three systems with different
scales, demonstrating the high computational efficiency and scalability of the
proposed spatio-temporal decomposition method
Economia colaborativa
A importância de se proceder à análise dos principais desafios jurÃdicos que a economia colaborativa coloca – pelas implicações que as mudanças de paradigma dos modelos de negócios e dos sujeitos envolvidos suscitam − é indiscutÃvel, correspondendo à necessidade de se fomentar a segurança jurÃdica destas práticas, potenciadoras de crescimento económico e bem-estar social.
O Centro de Investigação em Justiça e Governação (JusGov) constituiu uma equipa multidisciplinar que, além de juristas, integra investigadores de outras áreas, como a economia e a gestão, dos vários grupos do JusGov – embora com especial participação dos investigadores que integram o grupo E-TEC (Estado, Empresa e Tecnologia) – e de outras prestigiadas instituições nacionais e internacionais, para desenvolver um projeto neste domÃnio, com o objetivo de identificar os problemas jurÃdicos que a economia colaborativa suscita e avaliar se já existem soluções para aqueles, refletindo igualmente sobre a conveniência de serem introduzidas alterações ou se será mesmo necessário criar nova regulamentação.
O resultado desta investigação é apresentado nesta obra, com o que se pretende fomentar a continuação do debate sobre este tema.Esta obra é financiada por fundos nacionais através da FCT — Fundação para a Ciência e a Tecnologia, I.P., no âmbito do Financiamento UID/05749/202
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
CFLIT: Coexisting Federated Learning and Information Transfer
Future wireless networks are expected to support diverse mobile services,
including artificial intelligence (AI) services and ubiquitous data
transmissions. Federated learning (FL), as a revolutionary learning approach,
enables collaborative AI model training across distributed mobile edge devices.
By exploiting the superposition property of multiple-access channels,
over-the-air computation allows concurrent model uploading from massive devices
over the same radio resources, and thus significantly reduces the communication
cost of FL. In this paper, we study the coexistence of over-the-air FL and
traditional information transfer (IT) in a mobile edge network. We propose a
coexisting federated learning and information transfer (CFLIT) communication
framework, where the FL and IT devices share the wireless spectrum in an OFDM
system. Under this framework, we aim to maximize the IT data rate and guarantee
a given FL convergence performance by optimizing the long-term radio resource
allocation. A key challenge that limits the spectrum efficiency of the
coexisting system lies in the large overhead incurred by frequent communication
between the server and edge devices for FL model aggregation. To address the
challenge, we rigorously analyze the impact of the computation-to-communication
ratio on the convergence of over-the-air FL in wireless fading channels. The
analysis reveals the existence of an optimal computation-to-communication ratio
that minimizes the amount of radio resources needed for over-the-air FL to
converge to a given error tolerance. Based on the analysis, we propose a
low-complexity online algorithm to jointly optimize the radio resource
allocation for both the FL devices and IT devices. Extensive numerical
simulations verify the superior performance of the proposed design for the
coexistence of FL and IT devices in wireless cellular systems.Comment: The paper has been accepted for publication by IEEE Transactions on
Wireless Communications (March 2023
An Orchestration Framework for Open System Models of Reconfigurable Intelligent Surfaces
To obviate the control of reflective intelligent surfaces (RISs) and the
related control overhead, recent works envisioned autonomous and
self-configuring RISs that do not need explicit use of control channels.
Instead, these devices, named hybrid RISs (HRISs), are equipped with receiving
radio-frequency (RF) chains and can perform sensing operations to act
independently and in parallel to the other network entities. A natural problem
then emerges: as the HRIS operates concurrently with the communication
protocols, how should its operation modes be scheduled in time such that it
helps the network while minimizing any undesirable effects? In this paper, we
propose an orchestration framework that answers this question revealing an
engineering trade-off, called the self-configuring trade-off, that
characterizes the applicability of self-configuring HRISs under the
consideration of massive multiple-input multiple-output (mMIMO) networks. We
evaluate our proposed framework considering two different HRIS hardware
architectures, the power- and signal-based HRISs that differ in their hardware
complexity. The numerical results show that the self-configuring HRIS can offer
significant performance gains when adopting our framework.Comment: 31 pages, 7 figures, submitted to an IEEE journa
AoI-Delay Tradeoff in Mobile Edge Caching: A Mixed-Order Drift-Plus-Penalty Algorithm
We consider a scheduling problem in a Mobile Edge Caching (MEC) network,
where a base station (BS) uploads messages from multiple source nodes (SNs) and
transmits them to mobile users (MUs) via downlinks, aiming to jointly optimize
the average service Age of Information (AoI) and service delay over MUs. This
problem is formulated as a difficult sequential decision making problem with
discrete-valued and linearly-constrained design variables. To solve this
problem, we first approximate its achievable region by characterizing its
superset and subset. The superset is derived based on the rate stability
theorem, while the subset is obtained using a novel stochastic policy. We also
validate that this subset is substantially identical to the achievable region
when the number of schedule resources is large. Additionally, we propose a
sufficient condition to check the existence of the solution to the problem.
Then, we propose the mixed-order drift-plus-penalty algorithm that uses a
dynamic programming (DP) method to optimize the summation over a linear and
quadratic Lyapunov drift and a penalty term, to handle the product term over
different queue backlogs in the objective function. Finally, by associating the
proposed algorithm with the stochastic policy, we demonstrate that it achieves
an versus tradeoff for the average AoI and average delay
Performance Analysis and Comparison of Non-ideal Wireless PBFT and RAFT Consensus Networks in 6G Communications
Due to advantages in security and privacy, blockchain is considered a key
enabling technology to support 6G communications. Practical Byzantine Fault
Tolerance (PBFT) and RAFT are seen as the most applicable consensus mechanisms
(CMs) in blockchain-enabled wireless networks. However, previous studies on
PBFT and RAFT rarely consider the channel performance of the physical layer,
such as path loss and channel fading, resulting in research results that are
far from real networks. Additionally, 6G communications will widely deploy
high-frequency signals such as terahertz (THz) and millimeter wave (mmWave),
while performances of PBFT and RAFT are still unknown when these signals are
transmitted in wireless PBFT or RAFT networks. Therefore, it is urgent to study
the performance of non-ideal wireless PBFT and RAFT networks with THz and
mmWave signals, to better make PBFT and RAFT play a role in the 6G era. In this
paper, we study and compare the performance of THz and mmWave signals in
non-ideal wireless PBFT and RAFT networks, considering Rayleigh Fading (RF) and
close-in Free Space (FS) reference distance path loss. Performance is evaluated
by five metrics: consensus success rate, latency, throughput, reliability gain,
and energy consumption. Meanwhile, we find and derive that there is a maximum
distance between two nodes that can make CMs inevitably successful, and it is
named the active distance of CMs. The research results not only analyze the
performance of non-ideal wireless PBFT and RAFT networks, but also provide
important references for the future transmission of THz and mmWave signals in
PBFT and RAFT networks.Comment: arXiv admin note: substantial text overlap with arXiv:2303.1575
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Co-design As Healing: Exploring The Experiences Of Participants Facing Mental Health Problems
This thesis is an exploration of the healing role of co-design in mental health. Although co-design projects conducted within mental health settings are rising, existing literature tends to focus on the object of design and its outcomes while the experiences of participants per se remain largely unexplored. The guiding research question of this study is not how we design things that improve mental health, but how co-designing, as an act, might do so.
The thesis presents two projects that were organized in collaboration with the mental health charity Islington Mind and the Psychosis Therapy Project (PTP) in London.
The project at Islington Mind used a structured design process inviting participants to design for wellbeing. A case study analysis provides insights on how participants were impacted, summarizing key challenges and opportunities.
The design at PTP worked towards creating a collective brief in an emergent fashion, finally culminating in a board game. The experiences of participants were explored through Interpretative Phenomenological Analysis (IPA), using semi-structured interview data. The analysis served to identify key themes characterising the experience of co-design such as contributing, connecting, thinking and intentioning. In addition, a mixed-methods analysis of questionnaires and interview data exploring participants' wellbeing, showed that all participants who engaged fairly consistently in the project improved after the project ended, although some participants' scores returned to baseline six months later.
Reflecting on both projects, an approach to facilitation within mental health is outlined, detailing how the dimensions of weaving and layered participation, nurturing mattering and facilitating attitudes interlace. This contribution raises awareness of tacit dimensions in the practice of facilitation, articulating the nuances of how to encourage and sustain meaningful and ethical engagement and offering insights into a range of tools. It highlights the importance of remaining reflexive in relation to attitudes and emotions and discusses practical methodological and ethical challenges and ways to resolve them which can be of benefit to researchers embarking on a similar journey.
The thesis also offers detailed insights on how methodologies from different fields were integrated into a whole, arguing for transparency and reflexivity about epistemological assumptions, and how underlying paradigms shift in an interdisciplinary context.
Based on the overall findings, the thesis makes a case for considering design as healing (or a designerly way of healing), highlighting implications at a systems, social and individual level. It makes an original contribution to our understanding of design, highlighting its healing character, and proposes a new way to support mental health. The participants in this study not only had increased their own wellbeing through co-designing, but were also empowered and contributed towards healing the world. Hence, the thesis argues for a unique, holistic perspective of design and mental health, recognizing the interconnectedness of the individual, social and systemic dimensions of the healing processes that are ignited
Coloniality and the Courtroom: Understanding Pre-trial Judicial Decision Making in Brazil
This thesis focuses on judicial decision making during custody hearings in Rio de Janeiro, Brazil. The impetus for the study is that while national and international protocols mandate the use of pre-trial detention only as a last resort, judges continue to detain people pre-trial in large numbers. Custody hearings were introduced in 2015, but the initiative has not produced the reduction in pre-trial detention that was hoped. This study aims to understand what informs judicial decision making at this stage. The research is approached through a decolonial lens to foreground legacies of colonialism, overlooked in mainstream criminological scholarship. This is an interview-based study, where key court actors (judges, prosecutors, and public defenders) and subject matter specialists were asked about influences on judicial decision making. Interview data is complemented by non-participatory observation of custody hearings. The research responds directly to Aliverti et al.'s (2021) call to ‘decolonize the criminal question’ by exposing and explaining how colonialism informs criminal justice practices. Answering the call in relation to judicial decision making, findings provide evidence that colonial-era assumptions, dynamics, and hierarchies were evident in the practice of custody hearings and continue to inform judges’ decisions, thus demonstrating the coloniality of justice. This study is significant for the new empirical data presented and theoretical innovation is also offered via the introduction of the ‘anticitizen’. The concept builds on Souza’s (2007) ‘subcitizen’ to account for the active pursuit of dangerous Others by judges casting themselves as crime fighters in a modern moral crusade. The findings point to the limited utility of human rights discourse – the normative approach to influencing judicial decision making around pre-trial detention – as a plurality of conceptualisations compete for dominance. This study has important implications for all actors aiming to reduce pre-trial detention in Brazil because unless underpinning colonial logics are addressed, every innovation risks becoming the next lei para inglês ver (law [just] for the English to see)
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