585 research outputs found
Geometry of D1-D5-P bound states
Supersymmetric solutions of 6-d supergravity (with two translation
symmetries) can be written as a hyperkahler base times a 2-D fiber. The subset
of these solutions which correspond to true bound states of D1-D5-P charges
give microstates of the 3-charge extremal black hole. To understand the
characteristics shared by the bound states we decompose known bound state
geometries into base-fiber form. The axial symmetry of the solutions make the
base Gibbons-Hawking. We find the base to be actually `pseudo-hyperkahler': The
signature changes from (4,0) to (0,4) across a hypersurface. 2-charge D1-D5
geometries are characterized by a `central curve' ; the analogue for
3-charge appears to be a hypersurface that for our metrics is an orbifold of
.Comment: 20 pages, LaTeX; references adde
Dynamics of supertubes
We find the evolution of arbitrary excitations on 2-charge supertubes, by
mapping the supertube to a string carrying traveling waves. We argue that when
the coupling is increased from zero the energy of excitation leaks off to
infinity, and when the coupling is increased still further a new set of long
lived excitations emerge. We relate the excitations at small and large
couplings to excitations in two different phases in the dual CFT. We conjecture
a way to distinguish bound states from unbound states among 3-charge BPS
geometries; this would identify black hole microstates among the complete set
of BPS geometries.Comment: 50 pages, 3 figure
IoT and Sensor Networks in Industry and Society
The exponential progress of Information and Communication Technology (ICT) is one of the main elements that fueled the acceleration of the globalization pace. Internet of Things (IoT), Artificial Intelligence (AI) and big data analytics are some of the key players of the digital transformation that is affecting every aspect of human's daily life, from environmental monitoring to healthcare systems, from production processes to social interactions. In less than 20 years, people's everyday life has been revolutionized, and concepts such as Smart Home, Smart Grid and Smart City have become familiar also to non-technical users.
The integration of embedded systems, ubiquitous Internet access, and Machine-to-Machine (M2M) communications have paved the way for paradigms such as IoT and Cyber Physical Systems (CPS) to be also introduced in high-requirement environments such as those related to industrial processes, under the forms of Industrial Internet of Things (IIoT or I2oT) and Cyber-Physical Production Systems (CPPS). As a consequence, in 2011 the German High-Tech Strategy 2020 Action Plan for Germany first envisioned the concept of Industry 4.0, which is rapidly reshaping traditional industrial processes. The term refers to the promise to be the fourth industrial revolution. Indeed, the ïŹrst industrial revolution was triggered by water and steam power. Electricity and assembly lines enabled mass production in the second industrial revolution. In the third industrial revolution, the introduction of control automation and Programmable Logic Controllers (PLCs) gave a boost to factory production. As opposed to the previous revolutions, Industry 4.0 takes advantage of Internet access, M2M communications, and deep learning not only to improve production efficiency but also to enable the so-called mass customization, i.e. the mass production of personalized products by means of modularized product design and ïŹexible processes.
Less than five years later, in January 2016, the Japanese 5th Science and Technology Basic Plan took a further step by introducing the concept of Super Smart Society or Society 5.0. According to this vision, in the upcoming future, scientific and technological innovation will guide our society into the next social revolution after the hunter-gatherer, agrarian, industrial, and information eras, which respectively represented the previous social revolutions. Society 5.0 is a human-centered society that fosters the simultaneous achievement of economic, environmental and social objectives, to ensure a high quality of life to all citizens. This information-enabled revolution aims to tackle todayâs major challenges such as an ageing population, social inequalities, depopulation and constraints related to energy and the environment. Accordingly, the citizens will be experiencing impressive transformations into every aspect of their daily lives.
This book offers an insight into the key technologies that are going to shape the future of industry and society. It is subdivided into five parts: the I Part presents a horizontal view of the main enabling technologies, whereas the II-V Parts offer a vertical perspective on four different environments.
The I Part, dedicated to IoT and Sensor Network architectures, encompasses three Chapters. In Chapter 1, Peruzzi and Pozzebon analyse the literature on the subject of energy harvesting solutions for IoT monitoring systems and architectures based on Low-Power Wireless Area Networks (LPWAN). The Chapter does not limit the discussion to Long Range Wise Area Network (LoRaWAN), SigFox and Narrowband-IoT (NB-IoT) communication protocols, but it also includes other relevant solutions such as DASH7 and Long Term Evolution MAchine Type Communication (LTE-M). In Chapter 2, Hussein et al. discuss the development of an Internet of Things message protocol that supports multi-topic messaging. The Chapter further presents the implementation of a platform, which integrates the proposed communication protocol, based on Real Time Operating System. In Chapter 3, Li et al. investigate the heterogeneous task scheduling problem for data-intensive scenarios, to reduce the global task execution time, and consequently reducing data centers' energy consumption. The proposed approach aims to maximize the efficiency by comparing the cost between remote task execution and data migration.
The II Part is dedicated to Industry 4.0, and includes two Chapters. In Chapter 4, Grecuccio et al. propose a solution to integrate IoT devices by leveraging a blockchain-enabled gateway based on Ethereum, so that they do not need to rely on centralized intermediaries and third-party services.
As it is better explained in the paper, where the performance is evaluated in a food-chain traceability application, this solution is particularly beneficial in Industry 4.0 domains. Chapter 5, by De Fazio et al., addresses the issue of safety in workplaces by presenting a smart garment that integrates several low-power sensors to monitor environmental and biophysical parameters. This enables the detection of dangerous situations, so as to prevent or at least reduce the consequences of workers accidents.
The III Part is made of two Chapters based on the topic of Smart Buildings. In Chapter 6, PetroÈanu et al. review the literature about recent developments in the smart building sector, related to the use of supervised and unsupervised machine learning models of sensory data. The Chapter poses particular attention on enhanced sensing, energy efficiency, and optimal building management. In Chapter 7, Oh examines how much the education of prosumers about their energy consumption habits affects power consumption reduction and encourages energy conservation, sustainable living, and behavioral change, in residential environments. In this Chapter, energy consumption monitoring is made possible thanks to the use of smart plugs.
Smart Transport is the subject of the IV Part, including three Chapters. In Chapter 8, Roveri et al. propose an approach that leverages the small world theory to control swarms of vehicles connected through Vehicle-to-Vehicle (V2V) communication protocols. Indeed, considering a queue dominated by short-range car-following dynamics, the Chapter demonstrates that safety and security are increased by the introduction of a few selected random long-range communications. In Chapter 9, Nitti et al. present a real time system to observe and analyze public transport passengers' mobility by tracking them throughout their journey on public transport vehicles. The system is based on the detection of the active Wi-Fi interfaces, through the analysis of Wi-Fi probe requests. In Chapter 10, Miler et al. discuss the development of a tool for the analysis and comparison of efficiency indicated by the integrated IT systems in the operational activities undertaken by Road Transport Enterprises (RTEs). The authors of this Chapter further provide a holistic evaluation of efficiency of telematics systems in RTE operational management.
The book ends with the two Chapters of the V Part on Smart Environmental Monitoring. In Chapter 11, He et al. propose a Sea Surface Temperature Prediction (SSTP) model based on time-series similarity measure, multiple pattern learning and parameter optimization. In this strategy, the optimal parameters are determined by means of an improved Particle Swarm Optimization method. In Chapter 12, Tsipis et al. present a low-cost, WSN-based IoT system that seamlessly embeds a three-layered cloud/fog computing architecture, suitable for facilitating smart agricultural applications, especially those related to wildfire monitoring.
We wish to thank all the authors that contributed to this book for their efforts. We express our gratitude to all reviewers for the volunteering support and precious feedback during the review process. We hope that this book provides valuable information and spurs meaningful discussion among researchers, engineers, businesspeople, and other experts about the role of new technologies into industry and society
D1-D5-P microstates at the cap
The geometries describing D1-D5-P bound states in string theory have three
regions: flat asymptotics, an anti-de Sitter throat, and a 'cap' region at the
bottom of the throat. We identify the CFT description of a known class of
supersymmetric D1-D5-P microstate geometries which describe degrees of freedom
in the cap region. The class includes both regular solutions and solutions with
conical defects, and generalizes configurations with known CFT descriptions: a
parameter related to spectral flow in the CFT is generalized from integer to
fractional values. We provide strong evidence for this identification by
comparing the massless scalar excitation spectrum between gravity and CFT and
finding exact agreement.Comment: 37 pages, 1 figure, v2: comment added, typos corrected, references
adde
Branes wrapping Black Holes
We examine the dynamics of extended branes, carrying lower dimensional brane
charges, wrapping black holes and black hole microstates in M and Type II
string theory. We show that they have a universal dispersion relation typical
of threshold bound states with a total energy equal to the sum of the
contributions from the charges. In near-horizon geometries of black holes,
these are BPS states, and the dispersion relation follows from supersymmetry as
well as properties of the conformal algebra. However they break all
supersymmetries of the full asymptotic geometries of black holes and
microstates. We comment on a recent proposal which uses these states to explain
black hole entropy.Comment: 41 pages, 2 figures;v2: references adde
Stationary axisymmetric solutions of five dimensional gravity
We consider stationary axisymmetric solutions of general relativity that
asymptote to five dimensional Minkowski space. It is known that this system has
a hidden SL(3,R) symmetry. We identify an SO(2,1) subgroup of this symmetry
group that preserves the asymptotic boundary conditions. We show that the
action of this subgroup on a static solution generates a one-parameter family
of stationary solutions carrying angular momentum. We conjecture that by
repeated applications of this procedure one can generate all stationary
axisymmetric solutions starting from static ones. As an example, we derive the
Myers-Perry black hole starting from the Schwarzschild solution in five
dimensions.Comment: 31 pages, LaTeX; references adde
Urban mobility services based on user virtualization and social IoT
Smart cities are characterized by smart heterogeneous devices that can interact and cooperate with each other by exchanging regularly low amounts of data in the context of IoT. Lately, there has been an increasing interest in enhancing the IoT paradigm to support exchange of multimedia data. This paper focuses on the concept of Urban Mobility Services and in particular on proposing a solution to enable best QoS and load balance in a 5G network context. The paper introduces a novel algorithm for MobilIty Services uSer vIrtualizatiON (MISSION). MISSION employs cloud computing and broadcast of multimedia content in order to reduce the network load, the number of interactions, and user device energy consumption. It also relies on rating of network reputation in the 5G heterogeneous network environment and performing network selection in the quest to maximize QoS parameters. The performance of the proposed solution is compared against that of a TraffictYpe-based DifferEntiated Reputation (TYDER) algorithm. This performance was evaluated in terms of QoS parameters such as delay, latency, packet loss and prediction error. The results show how MISSION outperforms TYDER in urban mobility scenario
A microstate for the 3-charge black ring
We start with a 2-charge D1-D5 BPS geometry that has the shape of a ring;
this geometry is regular everywhere. In the dual CFT there exists a
perturbation that creates one unit of excitation for left movers, and thus adds
one unit of momentum P. This implies that there exists a corresponding
normalizable perturbation on the near-ring D1-D5 geometry. We find this
perturbation, and observe that it is smooth everywhere. We thus find an example
of `hair' for the black ring carrying three charges -- D1, D5 and one unit of
P. The near-ring geometry of the D1-D5 supertube can be dualized to a D6 brane
carrying fluxes corresponding to the `true' charges, while the quantum of P
dualizes to a D0 brane. We observe that the fluxes on the D6 brane are at the
threshold between bound and unbound states of D0-D6, and our wavefunction helps
us learn something about binding at this threshold.Comment: 31 pages, 3 figures; references adde
Turbulence Modulation by Slender Fibers
In this paper, we numerically investigate the turbulence modulation produced by long flexible fibres in channel flow. The simulations are based on an EulerâLagrangian approach, where fibres are modelled as chains of constrained, sub-Kolmogorov rods. A novel algorithm is deployed to make the resolution of dispersed systems of constraint equations, which represent the fibres, compatible with a state-of-the-art, Graphics Processing Units-accelerated flow-solver for direct numerical simulations in the two-way coupling regime on High Performance Computing architectures. Two-way coupling is accounted for using the Exact Regularized Point Particle method, which allows to calculate the disturbance generated by the fibers on the flow considering progressively refined grids, down to a quasi-viscous length-scale. The bending stiffness of the fibers is also modelled, while collisions are neglected. Results of fluid velocity statistics for friction Reynolds number of the flow (Formula presented.) and fibers with Stokes number (Formula presented.) = 0.01 (nearly tracers) and 10 (inertial) are presented, with special regard to turbulence modulation and its dependence on fiber inertia and volume fraction (equal to (Formula presented.) · (Formula presented.) and (Formula presented.) · (Formula presented.)). The non-Newtonian stresses determined by the carried phase are also displayed, determined by long and slender fibers with fixed aspect ratio (Formula presented.), which extend up to the inertial range of the turbulent flow
Sensor-based early activity recognition inside buildings to support energy and comfort management systems
Building Energy and Comfort Management (BECM) systems have the potential to considerably reduce costs related to energy consumption and improve the efficiency of resource exploitation, by implementing strategies for resource management and control and policies for Demand-Side Management (DSM). One of the main requirements for such systems is to be able to adapt their management decisions to the usersâ specific habits and preferences, even when they change over time. This feature is fundamental to prevent usersâ disaffection and the gradual abandonment of the system. In this paper, a sensor-based system for analysis of user habits and early detection and prediction of user activities is presented. To improve the resulting accuracy, the system incorporates statistics related to other relevant external conditions that have been observed to be correlated (e.g., time of the day). Performance evaluation on a real use case proves that the proposed system enables early recognition of activities after only 10 sensor events with an accuracy of 81%. Furthermore, the correlation between activities can be used to predict the next activity with an accuracy of about 60%
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