Flexible Resource Optimization for GEO Multibeam Satellite Communication System

in IEEE Transactions on Wireless Communications (2021)

Conventional GEO satellite communication systems rely on a multibeam foot-print with a uniform resource allocation to provide connectivity to users. However, applying uniform resource allocation is ... [more ▼]

Conventional GEO satellite communication systems rely on a multibeam foot-print with a uniform resource allocation to provide connectivity to users. However, applying uniform resource allocation is inefficient in presence of non-uniform demand distribution. To overcome this limitation, the next generation of broadband GEO satellite systems will enable flexibility in terms of power and bandwidth assignment, enabling on-demand resource allocation. In this paper, we propose a novel satellite resource assignment design whose goal is to satisfy the beam traffic demand by making use of the minimum transmit power and utilized bandwidth. The motivation behind the proposed design is to maximize the satellite spectrum utilization by pushing the spectrum reuse to affordable limits in terms of tolerable interference. The proposed problem formulation results in a non-convex optimization structure, for which we propose an efficient tractable solution. We validate the proposed method with extensive numerical results, which demonstrate the efficiency of the proposed approach with respect to benchmark schemes. [less ▲]

Fluctuations and Limitations of a Multi-Sector Economic Model with Delays

in The proceedings of the 2010 American Control Conference (ACC) (2010)

A general multi-sector model of the economy is investigated. A sector's input to production, labor, evolves according to a jump Markov process. Labor jumps between sectors to balance supply and demand ... [more ▼]

A general multi-sector model of the economy is investigated. A sector's input to production, labor, evolves according to a jump Markov process. Labor jumps between sectors to balance supply and demand, where each sector differs by its productivity. The jump model captures the intrinsic noise of the micro agents on the macro level, which is represented by the random timing of labor jumps. Quantifying this noise is a central theme of this paper. An operator theoretic approach is utilized to capture the fluctuations of a linearized jump system exactly. As an illustrative example two sector and three sector economies are studied. In each case the optimal aggressiveness, gain, of a sector is determined for minimal variance. Delays are then introduced into the model. It is shown that the presence of a delay creates a limit on the minimum variance achievable and that high gain is destabilizing. For both the two and three sector models the nonlinear jump systems are simulated. It is shown that the operator theoretic approach is an appropriate method for quantifying the second moments. [less ▲]

FM Discriminator for AIS Satellite Detection

in Personal Satellite Services (2010)

The Automatic Identification System (AIS) is a tracking system used on ships for several decades to improve traffic monitoring and safety at sea in a short range. The modulation technique used is Gaussian ... [more ▼]

The Automatic Identification System (AIS) is a tracking system used on ships for several decades to improve traffic monitoring and safety at sea in a short range. The modulation technique used is Gaussian Minimum Shift Keying (GMSK). Recently, the idea of receiving AIS signals from space arose. This presents mainly two challenges. The first one is that received signals present a large Doppler range due to the satellite speed. The second one is the simultaneous reception of signals from ships because of the broad satellite coverage. In this paper, a novel non-coherent GMSK demodulator is proposed to handle the large Doppler shift problem based on several FM discriminators in parallel. A frame collision detection algorithm is presented but the collision problem is not addressed. In addition, computer simulated and real signals are used to study the receiver performance on an AWGN channel. [less ▲]

Fostering sustainable user behaviour: exploring meaning and its creation in products and services

in Valentine, Louise; Borja de Mozota, Brigitte; Nelson, Julien (Eds.) et al The Value of Design Research, Proceedings of the 11th International Conference of the European Academy of Design (2015)

This paper is integrated in our research project on fostering sustainable user behaviour by designing meaning. It explores different types of meaning in products and services, and their creation. For that ... [more ▼]

This paper is integrated in our research project on fostering sustainable user behaviour by designing meaning. It explores different types of meaning in products and services, and their creation. For that, the results of a literature study are integrated into an initial taxonomy of meaning and an initial framework for creating meaning. From the taxonomy we derive four roles that products and services can play in meaning making. Additionally we discuss how five possible interventions in users meaning making for behavioural change can be pursued by design on the basis of the framework. We illustrate the role of designers in creating meaning with examples, touch on its potential for behavioural change of users and outline further research needs. [less ▲]

Fracture mechanism simulation of inhomogeneous anisotropic rocks by extended finite element method

in Theoretical and Applied Fracture Mechanics (2019), 104

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores ... [more ▼]

The vast majority of rock masses is anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile, given the frequently asymmetric distribution of pores, grain sizes or different mineralogical compounds in different locations, they are often classified as inhomogeneous materials. In such materials, stress intensity factors (SIFs) at the crack tip, which control the initiation of failure, strongly depend on mechanical properties of the material near that area. On the other hand, crack propagation trajectories highly depend on the orthotropic properties of the rock mass. In this study, the SIFs are calculated by means of anisotropic crack tip enrichments and an interaction integral are developed for inhomogeneous materials with the help of the extended finite element method (XFEM). We also use the T-stress within the crack tip fields to develop a new criterion to estimate the crack initiation angles and propagation in rock masses. To verify and validate the proposed approach, the results are compared with experimental test results and those reported in the literature. It is found that the ratio of elastic moduli, shear stiffnesses, and material orientation angles have a significant impact on the SIFs. However, the rate of change in material properties is found to have a moderate effect on these factors and a more pronounced effect on the failure force. The results highlight the potential of the proposed formulation in the estimation of SIFs and crack propagation paths in inhomogeneous anisotropic materials. [less ▲]

The Framework of Security-Enhancing Friction: How UX Can Help Users Behave More Securely

in New Security Paradigms Workshop (2020, October 26)

A growing body of research in the usable privacy and security community addresses the question of how to best influence user behavior to reduce risk-taking.We propose to address this challenge by ... [more ▼]

A growing body of research in the usable privacy and security community addresses the question of how to best influence user behavior to reduce risk-taking.We propose to address this challenge by integrating the concept of user experience (UX) into empirical usable privacy and security studies that attempt to change risktaking behavior. UX enables us to study the complex interplay between user-related, system-related and contextual factors and provides insights into the experiential aspects underlying behavior change, including negative experiences. We first compare and contrast existing security-enhancing interventions (e.g., nudges, warnings, fear appeals) through the lens of friction. We then build on these insights to argue that it can be desirable to design for moments of negative UX in security-critical situations. For this purpose, we introduce the novel concept of security-enhancing friction, friction that effectively reduces the occurrence of risk-taking behavior and ensures that the overall UX (after use) is not compromised. We illustrate how security-enhancing friction provides an actionable way to systematically integrate the concept of UX into empirical usable privacy and security studies for meeting both the objectives of secure behavior and of overall acceptable experience. [less ▲]

Free boundary problems: numerical methods and data-driven simulations

Presentation (2018, March 05)

Friendly Batch Routing (FBR)

Software (2012)

The Friendly Batch Routing (FBR) application uses the Google Maps API to easily and simply gather route data for many origin-destination pairs. FBR is designed with usability in mind so that errors do not ... [more ▼]

The Friendly Batch Routing (FBR) application uses the Google Maps API to easily and simply gather route data for many origin-destination pairs. FBR is designed with usability in mind so that errors do not interrupt processing and skipped records can easily be resubmitted for processing. Additionally the FBR output can easily be imported into GIS packages. [less ▲]

From image to analysis: an extended finite element method to simulate the mechanical response of soft-tissue

Presentation (2014, April 10)

In this seminar we consider the problem of constructing a numerical method particularly well suited to modelling domains described by segmented image data of the human body. Instead of constructing a ... [more ▼]

In this seminar we consider the problem of constructing a numerical method particularly well suited to modelling domains described by segmented image data of the human body. Instead of constructing a conforming mesh of the problem domain, we use implicitly defined domains described using the level-set method. We then include information about the implicitly defined domains by enriching the usual finite element basis functions defined on a cartesian quadtree or octree mesh with hanging nodes. This approach introduces significant complexities compared with classical finite element methods. We will discuss difficulties with the treatment of hanging nodes, numerical integration and imposing Dirichlet boundary conditions. We will discuss the possible future of extensions of this work, including cutting of soft tissue, multiscale problems with complex microstructure, and model order reduction problems. [less ▲]

Fully-Actuated Aerial Manipulator for Infrastructure Contact Inspection: Design, Modeling, Localization, and Control

in Sensors (2020)

This paper presents the design, modeling and control of a fully actuated aerial robot for infrastructure contact inspection as well as its localization system. Health assessment of transport ... [more ▼]

This paper presents the design, modeling and control of a fully actuated aerial robot for infrastructure contact inspection as well as its localization system. Health assessment of transport infrastructure involves measurements with sensors in contact with the bridge and tunnel surfaces and the installation of monitoring sensing devices at specific points. The design of the aerial robot presented in the paper includes a 3DoF lightweight arm with a sensorized passive joint which can measure the contact force to regulate the force applied with the sensor on the structure. The aerial platform has been designed with tilted propellers to be fully actuated, achieving independent attitude and position control. It also mounts a “docking gear” to establish full contact with the infrastructure during the inspection, minimizing the measurement errors derived from the motion of the aerial platform and allowing full contact with the surface regardless of its condition (smooth, rough, ...). The localization system of the aerial robot uses multi-sensor fusion of the measurements of a topographic laser sensor on the ground and a tracking camera and inertial sensors on-board the aerial robot, to be able to fly under the bridge deck or close to the bridge pillars where GNSS satellite signals are not available. The paper also presents the modeling and control of the aerial robot. Validation experiments of the localization system and the control system, and with the aerial robot inspecting a real bridge are also included. [less ▲]