5,646 results on '"David Martin"'
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2. Approximating Symplectic Realizations: A General Framework for the Construction of Poisson Integrators
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Cabrera, Alejandro, de Diego, David Martín, and Vaquero, Miguel
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Mathematics - Numerical Analysis ,Mathematics - Differential Geometry ,65P10, 53D05 - Abstract
While the construction of symplectic integrators for Hamiltonian dynamics is well understood, an analogous general theory for Poisson integrators is still lacking. The main challenge lies in overcoming the singular and non-linear geometric behavior of Poisson structures, such as the presence of symplectic leaves with varying dimensions. In this paper, we propose a general approach for the construction of geometric integrators on any Poisson manifold based on independent geometric and dynamic sources of approximation. The novel geometric approximation is obtained by adapting structural results about symplectic realizations of general Poisson manifolds. We also provide an error analysis for the resulting methods and illustrative applications.
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- 2024
3. Low-Attaining Secondary School Mathematics Students' Perspectives on Recommended Teaching Strategies
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Jeremy Hodgen, Colin Foster, Margaret Brown, and David Martin
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Recent research syntheses have identified several potentially high-leverage teaching strategies for improving low-attaining secondary school students' learning of mathematics. These strategies include the structured use of representations and manipulatives and an emphasis on derived facts and estimation. This paper reports on 70 semi-structured interviews conducted with low-attaining students in Years 9-10 (ages 13-15) in England. The interviews addressed the students' perceptions of learning mathematics and the teaching strategies that they experienced and believed were most helpful. Many students reported rarely using number lines, not spontaneously estimating answers and being unfamiliar with derived facts. During the interviews, with minimal direction, students often showed that they were well able to make use of these strategies; however, they did not report making spontaneous use of them independently. We conclude that many of the most well-evidenced and recommended strategies to support low-attaining students in mathematics appear to be unfamiliar and unvalued, and we discuss how this might be addressed.
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- 2024
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4. Constructing Dynamic Feedback Linearizable Discretizations
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Jindal, Ashutosh, Nicolau, Florentina, Diego, David Martin, and Banavar, Ravi
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Electrical Engineering and Systems Science - Systems and Control - Abstract
Dynamic feedback linearization-based methods allow us to design control algorithms for a fairly large class of nonlinear systems in continuous time. However, this feature does not extend to their sampled counterparts, i.e., for a given dynamically feedback linearizable continuous time system, its numerical discretization may fail to be so. In this article, we present a way to construct discretization schemes (accurate up to first order) that result in schemes that are feedback linearizable. This result is an extension of our previous work, where we had considered only static feedback linearizable systems. The result presented here applies to a fairly general class of nonlinear systems, in particular, our analysis applies to both endogenous and exogenous types of feedback. While the results in this article are presented on a control affine form of nonlinear systems, they can be readily modified to general nonlinear systems.
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- 2024
5. Momentum-based gradient descent methods for Lie groups
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Campos, Cédric M., de Diego, David Martín, and Torrente, José
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Mathematics - Optimization and Control ,Computer Science - Machine Learning ,Mathematics - Differential Geometry ,Mathematics - Numerical Analysis ,65K10 (Primary) 70G45, 22E99 (Secondary) - Abstract
Polyak's Heavy Ball (PHB; Polyak, 1964), a.k.a. Classical Momentum, and Nesterov's Accelerated Gradient (NAG; Nesterov, 1983) are well know examples of momentum-descent methods for optimization. While the latter outperforms the former, solely generalizations of PHB-like methods to nonlinear spaces have been described in the literature. We propose here a generalization of NAG-like methods for Lie group optimization based on the variational one-to-one correspondence between classical and accelerated momentum methods (Campos et al., 2023). Numerical experiments are shown., Comment: 24 pages, 2 algorithms, 5 figures
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- 2024
6. Designing Poisson Integrators Through Machine Learning
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Vaquero, Miguel, de Diego, David Martín, and Cortés, Jorge
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Mathematical Physics ,Computer Science - Machine Learning ,Mathematics - Differential Geometry ,Mathematics - Dynamical Systems ,Mathematics - Numerical Analysis ,37J06, 70H15, 70H20, 70G45, 65L05, 68T07 ,G.1.8 ,J.2 - Abstract
This paper presents a general method to construct Poisson integrators, i.e., integrators that preserve the underlying Poisson geometry. We assume the Poisson manifold is integrable, meaning there is a known local symplectic groupoid for which the Poisson manifold serves as the set of units. Our constructions build upon the correspondence between Poisson diffeomorphisms and Lagrangian bisections, which allows us to reformulate the design of Poisson integrators as solutions to a certain PDE (Hamilton-Jacobi). The main novelty of this work is to understand the Hamilton-Jacobi PDE as an optimization problem, whose solution can be easily approximated using machine learning related techniques. This research direction aligns with the current trend in the PDE and machine learning communities, as initiated by Physics- Informed Neural Networks, advocating for designs that combine both physical modeling (the Hamilton-Jacobi PDE) and data., Comment: 5 pages, 5 figures
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- 2024
7. Feedback Linearizable Discretizations of Second Order Mechanical Systems using Retraction Maps
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B., Shreyas N., Diego, David Martin, and Banavar, Ravi
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Electrical Engineering and Systems Science - Systems and Control - Abstract
Mechanical systems are most often described by a set of continuous-time, nonlinear, second-order differential equations (SODEs) of a particular structure governed by the covariant derivative. The digital implementation of controllers for such systems requires a discrete model of the system and hence requires numerical discretization schemes. Feedback linearizability of such sampled systems, however, depends on the discretization scheme employed. In this article, we utilize retraction maps and their lifts to construct feedback linearizable discretizations for SODEs which can be applied to many mechanical systems.
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- 2024
8. From retraction maps to symplectic-momentum numerical integrators
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Barbero-Liñán, María, Marrero, Juan Carlos, and de Diego, David Martín
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Mathematics - Numerical Analysis ,Mathematics - Symplectic Geometry - Abstract
Retraction maps have been generalized to discretization maps in (Barbero Li\~n\'an and and Mart\'{\i}n de Diego, 2022). Discretization maps are used to systematically derive numerical integrators that preserve the symplectic structure, as well as the discrete momemtum map under the assumption of symmetric preservation for the discretization map. The procedure described here gives a geometrical construction that can be easily adapted to discretize dynamics on more general structures and open the door to reduction processes., Comment: 4 pages
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- 2024
9. Metriplectic Euler-Poincar\'e equations: smooth and discrete dynamics
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Bloch, Anthony, Puiggalí, Marta Farré, and de Diego, David Martín
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Mathematical Physics ,Mathematics - Dynamical Systems ,70G45, 37J37 - Abstract
In this paper we will study some interesting properties of modifications of the Euler-Poincar\'e equations when we add a special type of dissipative force, so that the equations of motion can be described using the metriplectic formalism. The metriplectic representation of the dynamics allows us to describe the conservation of energy, as well as to guarantee entropy production. Moreover, we describe the use of discrete gradient systems to numerically simulate the evolution of the continuous metriplectic equations preserving their main properties: preservation of energy and correct entropy production rate., Comment: 14 pages, 5 figures
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- 2024
10. Symmetry Preservation in Hamiltonian Systems: Simulation and Learning
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Vaquero, Miguel, Cortés, Jorge, and de Diego, David Martín
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Mathematical Physics ,Computer Science - Machine Learning ,Mathematics - Numerical Analysis ,Mathematics - Optimization and Control ,Mathematics - Symplectic Geometry ,37J06, 70H15, 70H30, 37C79, 65L05 ,I.6.1 ,I.2.6 - Abstract
This work presents a general geometric framework for simulating and learning the dynamics of Hamiltonian systems that are invariant under a Lie group of transformations. This means that a group of symmetries is known to act on the system respecting its dynamics and, as a consequence, Noether's Theorem, conserved quantities are observed. We propose to simulate and learn the mappings of interest through the construction of $G$-invariant Lagrangian submanifolds, which are pivotal objects in symplectic geometry. A notable property of our constructions is that the simulated/learned dynamics also preserves the same conserved quantities as the original system, resulting in a more faithful surrogate of the original dynamics than non-symmetry aware methods, and in a more accurate predictor of non-observed trajectories. Furthermore, our setting is able to simulate/learn not only Hamiltonian flows, but any Lie group-equivariant symplectic transformation. Our designs leverage pivotal techniques and concepts in symplectic geometry and geometric mechanics: reduction theory, Noether's Theorem, Lagrangian submanifolds, momentum mappings, and coisotropic reduction among others. We also present methods to learn Poisson transformations while preserving the underlying geometry and how to endow non-geometric integrators with geometric properties. Thus, this work presents a novel attempt to harness the power of symplectic and Poisson geometry towards simulating and learning problems., Comment: 32 pages, 19 figures
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- 2023
11. Chapter 18. Making Marriages Mixed: Religious Pluralization, Ritual, and the Formation of Intra-Christian Marriage Barriers in Late Sixteenth- and Early Seventeenth-Century Germany
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Luebke, David Martin, primary
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- 2024
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12. Dynamic priority-based bandwidth allocation scheme for machine type communications
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David Martin Amitu, Roseline N Akol, and Jonathan Serugunda
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Bandwidth allocation ,Coexistence ,Dynamic priority ,Machine type communications ,Network adaptability ,Latency constraints ,Telecommunication ,TK5101-6720 ,Electronics ,TK7800-8360 - Abstract
Abstract The burgeoning realm of Machine Type Communications (MTC) has ushered in a paradigm shift in wireless communication, necessitating innovative strategies to efficiently manage diverse application requirements. This paper presents a pioneering Dynamic Priority-based Bandwidth Allocation (DPBA) scheme tailored specifically for MTC scenarios, encompassing both MTC and Human Type Communications (HTC) coexistence. DPBA employs an adaptive framework addressing dynamic MTC traffic, optimizing resource use while meeting latency constraints and sporadic data patterns. By dynamically prioritizing MTC applications based on requirements, the scheme allocates bandwidth for reliable data delivery. DPBA extends to MTC and HTC coexistence, managing diverse quality demands. This underlines its versatility and capacity to serve distinct needs in a shared spectrum. To substantiate its performance, the DPBA scheme is rigorously evaluated against a spectrum of related allocation methods like Proportional Fairness (PF), Static Priority Scheduling (SPS), and the Machine Learning-based Scheme (MLS), DPBA excels in simulations, minimizing packet loss, latency, enhancing throughput and ensuring fairness, surpassing benchmarks. This research underscores the critical importance of tailored bandwidth allocation strategies in advancing MTC and HTC coexistent environments. With its adaptability, efficiency, and remarkable performance, the DPBA scheme emerges as a cornerstone in the trajectory of wireless communication networks, catering to the distinct requirements of both MTC and HTC applications.
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- 2024
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13. Reduction by symmetries of contact mechanical systems on Lie groups
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Simoes, Alexandre Anahory, Colombo, Leonardo, de León, Manuel, Marrero, Juan Carlos, de Diego, David Martín, and Padrón, Edith
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Mathematical Physics ,Mathematics - Differential Geometry - Abstract
We study the dynamics of contact mechanical systems on Lie groups that are invariant under a Lie group action. Analogously to standard mechanical systems on Lie groups, existing symmetries allow for reducing the number of equations. Thus, we obtain Euler-Poincar\'e-Herglotz equations on the extended reduced phase space $\mathfrak{g}\times \R$ associated with the extended phase space $TG\times \R$, where the configuration manifold $G$ is a Lie group and $\mathfrak{g}$ its Lie algebra. Furthermore, we obtain the Hamiltonian counterpart of these equations by studying the underlying Jacobi structure. Finally, we extend the reduction process to the case of symmetry-breaking systems which are invariant under a Lie subgroup of symmetries., Comment: 38 pages
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- 2023
14. A new perspective on symplectic integration of constrained mechanical systems via discretization maps
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Liñán, María Barbero, de Diego, David Martín, and de Almagro, Rodrigo T. Sato Martín
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Mathematics - Numerical Analysis ,Mathematical Physics - Abstract
A new procedure to construct symplectic methods for constrained mechanical systems is developed in this paper. The definition of a map coming from the notion of retraction maps allows to adapt the continuous problem to the discretization rule rather than viceversa. As a result, the constraint submanifold is exactly preserved by the discrete flow and the extension of the methods to the case of non-linear configuration spaces is straightforward.
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- 2023
15. Constructing Feedback Linearizable Discretizations for Continuous-Time Systems using Retraction Maps
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Jindal, Ashutosh, Banavar, Ravi, and Diego, David Martin
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Electrical Engineering and Systems Science - Systems and Control - Abstract
Control laws for continuous-time dynamical systems are most often implemented via digital controllers using a sample-and-hold technique. Numerical discretization of the continuous system is an integral part of subsequent analysis. Feedback linearizability of such sampled systems is dependent upon the choice of discretization map or technique. In this article, for feedback linearizable continuous-time systems, we utilize the idea of retraction maps to construct discretizations that are feedback linearizable as well. We also propose a method to functionally compose discretizations to obtain higher-order integrators that are feedback linearizable., Comment: 7 pages, 9 figures
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- 2023
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16. Dynamic priority-based bandwidth allocation scheme for machine type communications
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Amitu, David Martin, Akol, Roseline N, and Serugunda, Jonathan
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- 2024
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17. How Germany is phasing out lignite: insights from the Coal Commission and local communities
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Radtke, Jörg and David, Martin
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- 2024
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18. How environments can promote active aging: results from a case study of two municipalities in Quebec, Canada
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McNeil-Gauthier, Anne-Lou, Milot, David-Martin, and Levasseur, Mélanie
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- 2024
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19. Higher-order retraction maps and construction of numerical methods for optimal control of mechanical systems
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Simoes, Alexandre Anahory, Liñán, Maria Barbero, Colombo, Leonardo, and de Diego, David Martín
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Mathematics - Optimization and Control ,Mathematics - Numerical Analysis - Abstract
Retractions maps are used to define a discretization of the tangent bundle of the configuration manifold as two copies of the configuration manifold where the dynamics take place. Such discretization maps can be conveniently lifted to a higher-order tangent bundle to construct geometric integrators for the higher-order Euler-Lagrange equations. Given a cost function, an optimal control problem for fully actuated mechanical systems can be understood as a higher-order variational problem. In this paper we introduce the notion of a higher-order discretization map associated with a retraction map to construct geometric integrators for the optimal control of mechanical systems. In particular, we study applications to path planning for obstacle avoidance of a planar rigid body., Comment: 8 pages
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- 2023
20. Discrete gradient methods for irreversible port-Hamiltonian systems
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Simoes, Alexandre Anahory, de Diego, David Martín, and Maschke, Bernhard
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Mathematics - Numerical Analysis ,Mathematical Physics ,Mathematics - Dynamical Systems - Abstract
In this paper we introduce discrete gradient methods to discretize irreversible port-Hamiltonian systems showing that the main qualitative properties of the continuous system are preserved using this kind discretizations methods., Comment: 8 pages, conference paper
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- 2023
21. Valorization of Biomass and Industrial Wastes as Alternative Fuels for Sustainable Cement Production
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Ofelia Rivera Sasso, Caleb Carreño Gallardo, David Martin Soto Castillo, Omar Farid Ojeda Farias, Martin Bojorquez Carrillo, Carolina Prieto Gomez, and Jose Martin Herrera Ramirez
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waste valorization ,alternative fuels ,carbon emissions ,clinker production ,Environmental technology. Sanitary engineering ,TD1-1066 ,Environmental engineering ,TA170-171 - Abstract
The cement industry contributes around 7% of global anthropogenic carbon dioxide emissions, mainly from the combustion of fuels and limestone decomposition during clinker production. Using alternative fuels derived from wastes is a key strategy to reduce these emissions. However, alternative fuels vary in composition and heating value, so selecting appropriate ones is crucial to maintain clinker quality and manufacturing processes while minimizing environmental impact. This study evaluated various biomass and industrial wastes as potential alternative fuels, characterizing them based on proximate analysis, elemental and oxide composition, lower heating value, and bulk density. Sawdust, pecan nutshell, industrial hose waste, and plastic waste emerged as viable options as they met the suggested thresholds for heating value, chloride, moisture, and ash content. Industrial hose waste and plastic waste were most favorable with the highest heating values while meeting all the criteria. Conversely, wind blade waste, tire-derived fuel, and automotive shredder residue did not meet all the recommended criteria. Therefore, blending them with alternative and fossil fuels is necessary to preserve clinker quality and facilitate combustion. The findings of this research will serve as the basis for developing a computational model to optimize the blending of alternative fuels with fossil fuels for cement production.
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- 2024
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22. Assessing the perioperative gain of weight (Δweight) as a determinant of morbidity after kidney transplantation: a retrospective exploratory study
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Beatriz Barberá Carbonell, Tobias Zingg, Maurice Matter, Gaëtan-Romain Joliat, David Martin, Manuel Pascual, Nicolas Demartines, Dela Golshayan, Luis Cano, and Ismail Labgaa
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Complications ,Prediction ,Biomarkers ,Transplant ,Outcomes ,Medicine ,Science - Abstract
Abstract Kidney transplantation (KT) is associated with a substantial risk of postoperative complications (POC) for which performant predictors are lacking. Data showed that a perioperative gain of weight (ΔWeight) was associated with higher risk of POC, but it remains unexplored in KT. This retrospective study aimed to investigate the association between ΔWeight and POC after KT. ΔWeight was calculated on postoperative day (POD) 2. POC were graded according to the Dindo-Clavien classification. Primary endpoint was overall POC. A total of 242 patients were included and 174 (71.9%) complications were reported. Patients showed a rapid gain of weight after KT. Mean ΔWeight was 7.83 kg (± 3.20) compared to 5.3 kg (± 3.56) in patients with and without complication, respectively (p = 0.0005). ΔWeight showed an accuracy of 0.74 for overall POC. A cut-off of 8.5 kg was determined. ΔWeight ≥ 8.5 kg was identified as an independent predictor of overall POC on multivariable analysis (OR 2.04; 95% CI 1.08–3.84; p = 0.025). ΔWeight ≥ 8.5 kg appeared as an independent predictor of POC after KT. These results stress the need to monitor weight in KT and to further investigate this surrogate with future studies assessing its clinical relevance.
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- 2024
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23. Recommended data elements for health registries: a survey from a German funding initiative
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Sonja Harkener, Ekkehart Jenetzky, Rüdiger Rupp, Jennifer Dell, Christoph Engel, Maximilian Ferry von Bargen, Robert Finger, Maximilian Glienke, Carsten Heinz, Patrick Jersch, David Martin, Rita Schmutzler, Martin Schönthaler, Barbara Suwelack, Jeannine Wegner, and Jürgen Stausberg
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Data element ,Health care ,Health services research ,Metadata ,Registry ,Computer applications to medicine. Medical informatics ,R858-859.7 - Abstract
Abstract Background The selection of data elements is a decisive task within the development of a health registry. Having the right metadata is crucial for answering the particular research questions. Furthermore, the set of data elements determines the registries’ readiness of interoperability and data reusability to a major extent. Six health registries shared and published their metadata within a German funding initiative. As one step in the direction of a common set of data elements, a selection of those metadata was evaluated with regard to their appropriateness for a broader usage. Methods Each registry was asked to contribute a 10%-selection of their data elements to an evaluation sample. The survey was set up with the online survey tool „LimeSurvey Cloud”. The registries and an accompanying project participated in the survey with one vote for each project. The data elements were offered in content groups along with the question of whether the data element is appropriate for health registries on a broader scale. The question could be answered using a Likert scale with five options. Furthermore, “no answer” was allowed. The level of agreement was assessed using weighted Cohen’s kappa and Kendall’s coefficient of concordance. Results The evaluation sample consisted of 269 data elements. With a grade of “perhaps recommendable” or higher in the mean, 169 data elements were selected. These data elements belong preferably to groups’ demography, education/occupation, medication, and nutrition. Half of the registries lost significance compared with their percentage of data elements in the evaluation sample, one remained stable. The level of concordance was adequate. Conclusions The survey revealed a set of 169 data elements recommended for health registries. When developing a registry, this set could be valuable help in selecting the metadata appropriate to answer the registry’s research questions. However, due to the high specificity of research questions, data elements beyond this set will be needed to cover the whole range of interests of a register. A broader discussion and subsequent surveys are needed to establish a common set of data elements on an international scale.
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- 2024
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24. The Left and the Populist Slur
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Jones, David Martin
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- 2024
25. Neurologic pelvic pain: Diagnosis and treatment, with attention to hip–spine–pelvis exam
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Oyenike Ilaka, Shreya Patel, Nucelio Lemos, Charles Argoff, Hal David Martin, and Elise De
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Chronic pelvic pain ,Neuropathic pain ,Diagnosis ,Treatment ,Expert opinion ,Diseases of the genitourinary system. Urology ,RC870-923 - Abstract
This article summarizes the 2023 International Continence Society (ICS) Workshop 5 focused on neurologically mediated chronic pelvic pain (CPP) (Workshop 5). A team of experts share practical advice and tools for assessment, diagnosis and management relevant to pudendal neuropathy or other nerve entrapment, central nervous system diagnoses such as herniated disc, radiculopathy, Tarlov cyst, tethered cord, hip confounders, and systemic neuropathy such as small fiber neuropathy, neuroinflammatory disease (e.g. Lyme, Multiple Sclerosis) and central sensitization.
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- 2024
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26. Towards Improving Real-Time Head-Worn Display Caption Mediated Conversations with Speaker Feedback for Hearing Conversation Partners.
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Jenna Jiayi Kang, Emily Layton, David Martin, and Thad Starner
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- 2024
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27. Robot-Guided End Effector for an Automated Finishing of Concrete Free-Form Surfaces
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David, Martin, Dröder, Klaus, Lowke, Dirk, editor, Freund, Niklas, editor, Böhler, David, editor, and Herding, Friedrich, editor
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- 2024
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28. Digital Fabrication with Local Earthen Materials: The Relevance of Process Robustness
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Gosslar, Joschua, Dorresteijn, Evelien, David, Martin, Leusmann, Thorsten, Dröder, Klaus, Lowke, Dirk, Kloft, Harald, Lowke, Dirk, editor, Freund, Niklas, editor, Böhler, David, editor, and Herding, Friedrich, editor
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- 2024
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29. Surface Processing of Shotcrete 3D Printed Concrete Elements Using a Rotating Trowel Disc – Influence of Timing on Resulting Surface Quality
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Dörrie, Robin, David, Martin, Freund, Niklas, Lowke, Dirk, Dröder, Klaus, Kloft, Harald, Lowke, Dirk, editor, Freund, Niklas, editor, Böhler, David, editor, and Herding, Friedrich, editor
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- 2024
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30. Vibrated Short Rebar Insertion - The Effect of Integration Time on the Resulting Bond Quality
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Freund, Niklas, David, Martin, Dröder, Klaus, Lowke, Dirk, Lowke, Dirk, editor, Freund, Niklas, editor, Böhler, David, editor, and Herding, Friedrich, editor
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- 2024
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31. Post-accident Recovery Treatment Using a Physio Room and Aided by an Assistive System
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David, Bertrand, Reynaud-David, Martin, Chalon, René, Jouffroy, Julien, Goos, Gerhard, Series Editor, Hartmanis, Juris, Founding Editor, van Leeuwen, Jan, Series Editor, Hutchison, David, Editorial Board Member, Kanade, Takeo, Editorial Board Member, Kittler, Josef, Editorial Board Member, Kleinberg, Jon M., Editorial Board Member, Kobsa, Alfred, Series Editor, Mattern, Friedemann, Editorial Board Member, Mitchell, John C., Editorial Board Member, Naor, Moni, Editorial Board Member, Nierstrasz, Oscar, Series Editor, Pandu Rangan, C., Editorial Board Member, Sudan, Madhu, Series Editor, Terzopoulos, Demetri, Editorial Board Member, Tygar, Doug, Editorial Board Member, Weikum, Gerhard, Series Editor, Vardi, Moshe Y, Series Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Woeginger, Gerhard, Editorial Board Member, and Krömker, Heidi, editor
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- 2024
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32. Cobordism, Singularities and the Ricci Flow Conjecture
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Velázquez, David Martín, De Biasio, Davide, and Lust, Dieter
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High Energy Physics - Theory - Abstract
In the following work, an attempt to conciliate the Ricci flow conjecture and the Cobordism conjecture, stated as refinements of the Swampland distance conjecture and of the No global symmetries conjecture respectively, is presented. This is done by starting from a suitable manifold with trivial cobordism class, applying surgery techniques to Ricci flow singularities and trivialising the cobordism class of one of the resulting connected components via the introduction of appropriate defects. The specific example of $\Omega^{SO}_4$ is studied in detail. A connection between the process of blowing up a point of a manifold and that of taking the connected sum of such with $\mathbb{CP}^n$ is explored. Hence, the problem of studying the Ricci flow of a $K3$ whose cobordism class is trivialised by the addition of $16$ copies of $\mathbb{CP}^2$ is tackled by applying both the techniques developed in the previous sections and the classification of singularities in terms of ADE groups., Comment: 52 pages, 2 figures
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- 2022
33. Understanding the factors associated with mental health practitioners' engagement in effective suicide prevention activities within an Improving Access to Psychological Therapies (IAPT) service
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Sandford, David Martin
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Background This thesis comprises of a systematic review and three empirical studies. It developed from efforts to encourage a culture within a primary care mental health service which maintained a focus on suicide prevention, despite the relative rarity of suicide deaths in any individual clinical setting. The service aimed to improve the knowledge and confidence of practitioners in this vital area and recognised the importance of supporting practitioners in the event of them losing a patient to suicide. Methods Three areas for study were selected which may be associated with practitioners' engagement in suicide prevention efforts. A systematic review of the impact on mental health practitioners of losing a patient to suicide was followed by a qualitative study exploring the impact of such deaths on practitioners within an Improving Access to Psychological Therapies service. A survey of all staff in an NHS Mental Health Trust was conducted using the Attitudes to Suicide Prevention Scale (ASPS) and these data were used to perform a replication of the validation of the scale. A new scale was developed to measure practitioners' confidence in assessing, formulating and managing the risk of suicide. This was administered to mental health practitioners to assess the psychometric properties of the scale. Results The systematic review included qualitative and quantitative studies (n=54) and found that the most common personal reactions included guilt, shock, sadness, anger and fear of blame. Impact on professional practice included self-doubt and being more cautious and defensive in the management of suicide risk. As quantitative study methodologies were heterogeneous, it was difficult to make direct comparisons across studies. However, across 13 studies (total n = 717 practitioners) that utilised the Impact of Event Scale, between 12% and 53% of practitioners recorded clinically significant trauma scores. The need for training focused on the impact of suicides and the value placed upon informal support were often cited in these studies. The experience of losing a patient through suicide can have a significant impact on mental health professionals, both in terms of their personal reactions and subsequent changes to professional practice. The negative impact, however, may be moderated by cultural and organisational factors and by the nature of support available. In Study one, survey data from all Trust staff were used to explore the psychometric properties of the Attitudes to Suicide Prevention Scale. Two items from the scale displayed poor item-scale correlation, therefore they were excluded from the factor analysis and a further item was also excluded as it used different anchor points. However, analyses of the remaining 11 items were not satisfactory, with no adequate factor structure emerging. Nonetheless, there were statistically significant differences in attitudes between specific staff groups (i.e., those with/with suicide awareness or prevention training, gender and by level of patient contact), but not between groups defined by age range. Generally, however, the scale indicated that there were positive attitudes across all Trust staff. Study two, the development of a scale to measure practitioners' confidence in assessing, formulating and managing risk of suicide, the analysis indicated a singlefactor structure, good test-retest reliability and statistically significant increases in confidence between pre- and post-training and between pre-training and six-month follow-up. Cohen's effect size values suggest a moderate to large effect. In Study three, a qualitative study with IAPT practitioners (n=7), analysis of the transcripts identified a number of themes related to the impact on staff. Specifically, the analyses yielded four superordinate themes which were represented in the majority of cases: 1) feeling shocked and upset about the death of a patient; 2) attempting to understand the causes of the suicide; 3) learning from the tragic event; and 4) reflections on what helped in coping with the tragic event. IAPT practitioners reported initial emotional responses of shock, upset, guilt and fear of blame following the death through suicide of a patient. This is consistent with the findings of the systematic review and previous research with mental health practitioners more broadly. Conclusion The studies included in this thesis, improved our understanding of the impact on practitioners of the loss of a patient by suicide. This supported changes within our service to help better prepare and support practitioners for such an eventuality. All practitioners are made aware of the potential for the loss of a patient by suicide, of the likely impact of this and of the support available to them. In order to keep a focus on the prevention of suicide and to improve practitioners' confidence in this, training has been developed in risk assessment, formulation and management and further training into the psychological moderators of suicidal behaviour and into safety planning has been delivered. Understanding staff attitudes could help identify potential barriers to effective engagement of practitioners in suicide prevention. The selection of the Attitudes to Suicide Prevention Scale for research purposes should be treated with caution and given the findings of Study one there is a sufficient rationale to develop a new measure. Effective engagement is also likely to be affected by practitioners' confidence in their ability to assess, formulate and manage suicide risk. A newly developed scale (Study two) displays promise as a measure for this purpose. The findings from Study three support the following recommendations from the systematic review. Services and training providers should ensure that practitioners are prepared for the eventuality of a patient suicide and are adequately supported if they experience such a tragic event. The provision of regular suicide prevention training can help create a culture that supports engagement in this vital activity. Training should also; address any negative attitudes to suicide prevention, increase practitioners' confidence in the assessment, formulation and management of suicide risk, prepare staff for the potential experience of losing a patient through suicide and inform them of what to expect in such an event including the available support.
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- 2023
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34. Muscle stiffness indicating mission crew health in space
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Britt Schoenrock, Paul E. Muckelt, Maria Hastermann, Kirsten Albracht, Robert MacGregor, David Martin, Hans-Christian Gunga, Michele Salanova, Maria J. Stokes, Martin B. Warner, and Dieter Blottner
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Medicine ,Science - Abstract
Abstract Muscle function is compromised by gravitational unloading in space affecting overall musculoskeletal health. Astronauts perform daily exercise programmes to mitigate these effects but knowing which muscles to target would optimise effectiveness. Accurate inflight assessment to inform exercise programmes is critical due to lack of technologies suitable for spaceflight. Changes in mechanical properties indicate muscle health status and can be measured rapidly and non-invasively using novel technology. A hand-held MyotonPRO device enabled monitoring of muscle health for the first time in spaceflight (> 180 days). Greater/maintained stiffness indicated countermeasures were effective. Tissue stiffness was preserved in the majority of muscles (neck, shoulder, back, thigh) but Tibialis Anterior (foot lever muscle) stiffness decreased inflight vs. preflight (p
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- 2024
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35. Dividing the kingdom: Britain's game of thrones
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Jones, David Martin
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- 2022
36. A parallel iterative method for variational integration
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Ferraro, Sebastián J., de Diego, David Martín, and de Almagro, Rodrigo Takuro Sato Martín
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Mathematics - Optimization and Control ,Mathematics - Numerical Analysis ,70-08, 70-10, 70G45, 70Hxx, 70Q05, 93-XX, 93C10, 49-XX, 49Mxx, 49M20, 65L10, 65L20 - Abstract
Discrete variational methods show excellent performance in numerical simulations of different mechanical systems. In this paper, we introduce an iterative procedure for the solution of discrete variational equations for boundary value problems. More concretely, we explore a parallelization strategy that leverages the capabilities of multicore CPUs and GPUs (graphics cards). We study this parallel method for higher-order Lagrangian systems, which appear in fully-actuated problems and beyond. The most important part of the paper is devoted to a precise study of different convergence conditions for these methods. We illustrate their excellent behavior in some interesting examples, namely Zermelo's navigation problem, a fuel-optimal navigation problem, interpolation problems or in a fuel optimization problem for a controlled 4-body problem in astrodynamics showing the potential of our method.
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- 2022
37. A scoping review of the research evidence of the developmental assets model in Europe
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Antonio David Martin-Barrado and Diego Gomez-Baya
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positive youth development ,development assets ,scoping review ,Europe ,wellbeing ,Psychology ,BF1-990 - Abstract
IntroductionPositive Youth Development (PYD) is a strength-based perspective that focuses on the resources to promote a successful transition to adulthood, derived from the Relational Developmental Systems theory. In this line, the Developmental Assets (DA) model focuses on describing the personal resources (Internal Assets) and contextual resources (External Assets) that help to reach PYD. Most research from this approach has been carried out in United States and, to a lesser extent, in the European continent. The aim of this scoping review was to examine the evidence collected for the DA model in Europe.MethodsWeb of Science database was used to search for articles published between 2013 and February 2024. Initially, there were 55 possible articles to be included, but after applying the exclusion criteria, this number was reduced to 11.ResultsThe findings suggested that the evidence for DA in Europe was in line with North American research, so that a higher presence of DA was related to higher well-being, better psychological adjustment, and lower risk behaviors. Internal Assets were the most influential assets, with the Positive Identity category being especially remarkable. Commitment to Learning and Social Competencies were also highlighted in the studies included in the review. Concerning External Assets, Positive Boundaries-expectations and Empowerment were emphasized as protective factors in youth development. These assets were found to present a protective effect against risk behaviors and were positively associated with PYD and socioemotional skills.DiscussionThus, these findings support the applicability of the DA framework in promoting PYD in European context, and some intervention strategies are discussed considering cultural diversity.
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- 2024
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38. The Tory origins of the industrial revolution
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Jones, David Martin
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- 2024
39. Chronobiology of Viscum album L.: a time series of daily metabolomic fingerprints spanning 27 years
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Greta Guglielmetti, Stephan Baumgartner, Claudia Scherr, David Martin, and Alexander L. Tournier
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chronobiology ,mistletoe ,metabolomic fingerprinting ,pattern formation ,image analysis ,medicinal plants ,Physiology ,QP1-981 - Abstract
Introduction: European mistletoe (Viscum album L.) has been gaining increasing interest in the field of oncology as a clinically relevant adjunctive treatment in many forms of cancer. In the field of phytopharmacology, harvesting time is pivotal. In the last century, a form of metabolomic fingerprinting based on pattern formation was proposed as a way to determine optimal harvesting times to ensure high quality of mistletoe as raw material for pharmaceutical use. In order to further evaluate the information obtained with this metabolomic fingerprinting method, we analysed a large time series of previously undigitised daily mistletoe chromatograms dating back to the 1950s.Methods: These chromatograms were scanned and evaluated using computerized image analysis, resulting in 12 descriptors for each individual chromatogram. We performed a statistical analysis of the data obtained, investigating statistical distributions, cross-correlations and time self-correlations.Results: The analysed dataset spanning about 27 years, contains 19,037 evaluable chromatograms in daily resolution. Based on the distribution and cross-correlation analyses, the 12 descriptors could be clustered into six independent groups describing different aspects of the chromatograms. One descriptor was found to mirror the annual rhythm being well correlated with temperature and a phase shift of 10 days. The time self-correlation analysis showed that most other descriptors had a characteristic self-correlation of ∼50 days, which points to further infradian rhythms (i.e., more than 24 h).Discussion: To our knowledge, this dataset is the largest of its type. The combination of this form of metabolomic fingerprinting with the proposed computer analysis seems to be a promising tool to characterise biological variations of mistletoe. Additional research is underway to further analyse the different rhythms present in this dataset.
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- 2024
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40. Eye-movement desensitisation and reprocessing therapy (EMDR) to prevent transition to psychosis in people with an at-risk mental state (ARMS): mixed method feasibility study
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Daniela Strelchuk, Nicola Wiles, Katrina Turner, Catherine Derrick, David Martin, Jonathan Davies, and Stan Zammit
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EMDR ,ARMS ,psychosis ,prevention ,feasibility study ,Psychiatry ,RC435-571 - Abstract
Background Trauma plays an important role in the development of psychosis, but no studies have investigated whether a trauma-focused therapy could prevent psychosis. Aims This study aimed to establish whether it would be feasible to conduct a multicentre randomised controlled trial (RCT) to prevent psychosis in people with an at-risk mental state (ARMS), using eye-movement desensitisation and reprocessing therapy (EMDR). Method This started as a mixed-method randomised study comparing EMDR to treatment as usual but, as a result of low participant recruitment, was changed to a single-arm feasibility study. The proposed primary outcome for an RCT was transition to psychosis at 12-month follow-up. Data on secondary outcomes were also collected. Qualitative interviews were conducted with patients and therapists. Results Fourteen participants were recruited from the Early Intervention teams. Most people who expressed an interest in taking part attended an assessment to determine eligibility. All those eligible consented to take part. A total of 64% (7 of 11) of participants who were offered EMDR were followed up at 12 months. Of the 11 participants offered EMDR, one (11%, 95% CI: 0.2%, 48%) transitioned to psychosis. Nine patients and three therapists were interviewed. Participants who completed therapy (n = 4; mean 10.5 sessions) found EMDR helpful, but those who discontinued (n = 6; mean 5.2 sessions) said it had not benefitted them overall. Therapists said EMDR could be effective, although not for all patients. Conclusions Future studies recruiting people with an ARMS to an RCT may need to extend recruitment beyond Early Intervention teams. Although some individuals found EMDR helpful, reasons for discontinuing need to be addressed in future studies.
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- 2024
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41. Presymplectic integrators for optimal control problems via retraction maps
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Liñán, María Barbero and de Diego, David Martín
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Mathematics - Optimization and Control ,Mathematics - Numerical Analysis ,Mathematics - Symplectic Geometry - Abstract
Retractions maps are used to define a discretization of the tangent bundle of the configuration manifold as two copies of the configuration manifold where the dynamics take place. Such discretization maps can be conveniently lifted to the cotangent bundle so that symplectic integrators are constructed for Hamilton's equations. Optimal control problems are provided with a Hamiltonian framework by Pontryagin's Maximum Principle. That is why we use discretization maps and the integrability algorithm to obtain presymplectic integrators for optimal control problems.
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- 2022
42. Variational integrators for non-autonomous systems with applications to stabilization of multi-agent formations
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Colombo, Leonardo, Fernández, Manuela Gamonal, and de Diego, David Martín
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Electrical Engineering and Systems Science - Systems and Control ,Mathematics - Numerical Analysis ,Mathematics - Optimization and Control - Abstract
Numerical methods that preserve geometric invariants of the system, such as energy, momentum or the symplectic form, are called geometric integrators. Variational integrators are an important class of geometric integrators. The general idea for those variational integrators is to discretize Hamilton's principle rather than the equations of motion in a way that preserves some of the invariants of the original system. In this paper we construct variational integrators with fixed time step for time-dependent Lagrangian systems modelling an important class of autonomous dissipative systems. These integrators are derived via a family of discrete Lagrangian functions each one for a fixed time-step. This allows to recover at each step on the set of discrete sequences the preservation properties of variational integrators for autonomous Lagrangian systems, such as symplecticity or backward error analysis for these systems. We also present a discrete Noether theorem for this class of systems. Applications of the results are shown for the problem of formation stabilization of multi-agent systems., Comment: arXiv admin note: text overlap with arXiv:2010.00425
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- 2022
43. The role of start-ups as knowledge brokers: a supply chain ecosystem perspective
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Magliocca, Pierpaolo, Herold, David Martin M., Canestrino, Rossella, Temperini, Valerio, and Albino, Vito
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- 2023
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44. Terrorism and the western mind
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Jones, David Martin
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- 2021
45. Multichannel detection of evoked responses using critical values corrected by a parametric bootstrap: Frequency-domain cholesky correction
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Zanotelli, Tiago, Ribeiro, Mateus, Vaz, Patrícia Nogueira, Felix, Leonardo Bonato, Mendes, Eduardo Mazoni Andrade Marçal, Miranda de Sá, Antonio Mauricio Ferreira Leite, and Simpson, David Martin
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- 2024
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46. POTDAI: A Tool to Evaluate the Perceived Operational Trust Degree in Artificial Intelligence Systems
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David Martin-Moncunill, Eduardo Garcia Laredo, and Juan Carlos Nieves
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Artificial intelligence ,cooperative systems ,human-computer interaction ,human factors ,trustworthy AI ,technology acceptance model ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
There is evidence that a user’s subjective confidence in an Artificial Intelligence (AI)-based system is crucial in its use, even more decisive than the objective effectiveness and efficiency of the system. Therefore, different methods have been proposed for analyzing confidence in AI. In our research, we set out to evaluate how the degree of perceived trust in an AI system could affect a user’s final decision to follow AI recommendations. To this end, we established trustworthy criteria that such an evaluation should meet by following a co-creation approach with a multidisciplinary group of 10 experts. After a systematic review of 3,204 articles, we found that none of the tools met the inclusion criteria. Thus, we introduce the so-called “Perceived Operational Trust Degree in AI” (POTDAI) tool that is based on the findings from the expert group and the literature analysis, with a methodology that adds rigor to that employed previously to create similar evaluation tools. We propose a short questionnaire for quick and easy application, inspired by the original version of the Technology Acceptance Model (TAM) with six Likert-type items. In this way, we also respond to the need pointed out by authors such as Vorm and Combs to extend the TAM to address questions related to user perception in systems with an AI component. Thus, POTDAI can be used alone or in combination with TAM to obtain additional information on its usefulness and ease of use.
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- 2024
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47. Exploiting Zero Forcing and Block Diagonalization Precoding for Multi-User MIMO ISAC: Bridging Communications and Sensing
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Carlos Ravelo, David Martin-Sacristan, and Jose F. Monserrat
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ISAC ,MU-MIMO ,precoding ,user selection ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
This paper explores the potential of applying Zero Forcing (ZF) and Block Diagonalization (BD), two linear precoding techniques commonly utilized in communications, to a Multi-User Multiple Input Multiple Output (MU-MIMO) Integrated Sensing and Communications (ISAC) setup. The parallels between communications and sensing are highlighted to show the feasibility of extending ZF and BD to ISAC. To enable the implementation of these techniques, the concept of sensing channel is exploited, enabling the treatment of the sensing receiver as an additional user. Furthermore, two user selection strategies extend existing communication-only algorithms to accommodate sensing requirements. The efficacy of the proposed techniques is substantiated through comprehensive simulations. With the proposed solution, a high beampattern gain is maintained for the sensing while keeping good communication performance, only limited by the power allocation between the two functionalities.
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- 2024
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48. Sustainable Mobility in B5G/6G: V2X Technology Trends and Use Cases
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Sandra Roger, Carmen Botella-Mascarell, David Martin-Sacristan, David Garcia-Roger, Jose F. Monserrat, and Tommy Svensson
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6G ,beyond 5G ,ITS ,mobile communications ,SDGs ,Sustainability ,Transportation engineering ,TA1001-1280 ,Transportation and communications ,HE1-9990 - Abstract
The concept of sustainability has been recently extended to cover economic and social factors besides the traditional environmental ones. This paper reflects on the potential of mobile communication standards towards achieving sustainable mobility, with focus on vehicular communications and use cases in smart cities scenarios. In this context, intelligent transportation systems, including connected and autonomous vehicles, will be key for developing affordable and sustainable infrastructures and services. We start by identifying three current technology trends, namely, towards climate neutral; cloudification and edge computing; and Big Data and artificial intelligence, and then we examine their capability to enable sustainable Vehicle-to-Everything (V2X) communication systems in beyond 5G and 6G networks. In the second part of the paper, a set of selected use case categories involving connected and autonomous vehicles is presented, showcasing the potential impact of the selected technology trends. Finally, a review of the estimates of the quantitative savings that could be achieved in environmental-related parameters such as energy/fuel consumption and greenhouse gas emissions is provided.
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- 2024
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49. A Scoping Review of the Evidence of the 5Cs Model of Positive Youth Development in Europe
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Antonio David Martin-Barrado and Diego Gomez-Baya
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5Cs ,positive youth development ,scoping review ,Europe ,Urban groups. The city. Urban sociology ,HT101-395 - Abstract
In the last 20 years, evidence has been found that supports the “5Cs” of the Positive Youth Development (PYD) model developed by Lerner and his colleagues in the United States. This model considers adolescents as active elements who may acquire the resources and strengths to develop positive relationships with others. However, few studies have focused on its generalization to other contexts. Therefore, the aim of the present scoping review is to examine the evidence of the 5Cs model (Confidence, Competence, Caring, Connection and Character) in Europe. A search was carried out in the international Web of Science database for articles published in Europe between 2013 and June 2023, obtaining 123 articles. Subsequently, after applying the inclusion criteria, 23 articles were included. The findings agreed that men have higher levels of Competence and Confidence, while women scored higher in Connection, Caring and Character. Furthermore, many studies stated that higher scores in Connection, Competence, Character and Confidence are related to better mental health, higher academic performance and greater social and environmental contribution. Consequently, it is crucial to increase the number of interventions based on this model to result in future adults who are healthy, happy and engaged with society. Finally, future lines of research are discussed, as well as the importance of researchers carrying out more intervention programs.
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- 2024
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50. Correlating food and nutritional patterns with cancers in the pediatric oncology population at two specialized hospitals in Tanzania
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Dafrosa Joseph Monko, Haikael David Martin, and Emmanuel Abraham Mpolya
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Pediatric oncology population ,Clinical nutrition ,Nutritional guidelines ,Malnutrition ,LMIC ,Africa ,Nutrition. Foods and food supply ,TX341-641 ,Food processing and manufacture ,TP368-456 ,Medicine (General) ,R5-920 - Abstract
Abstract Background This study of nutritional patterns in relation to cancers among pediatric oncology population in Tanzania was motivated by the lack of up-to-date information about the nutritional practices, the controversy around the importance of nutritional support and the lack of consistent nutritional criteria among pediatric oncology populations. Methods A survey study in two cancer referral hospitals of children diagnosed with any cancers, aged between 1 and 17 years inclusive and being eligible for enteral feeding included 131 children. Their demographic, nutritional, feeding and cancer profiles were analyzed descriptively through mapping and other approaches as well as inferentially using multinomial regression models to understand different aspects of nutrition for children suffering from cancers. Results The majority (15% or higher) of pediatric oncology population originated from the lake zone. Between 7 and 12% of pediatric oncology population originated from the Western zone. The top-three cancers with their percentages in the brackets were: Wilms Tumor (32%), Acute Lymphoblastic Leukemia (26%) and Retinoblastoma (13%). About 69% of the pediatric oncology population ate foods that are rich in energy but poor in protein such as rice (21.5%), porridge (19.3%), banana (11.7%) and potatoes (10.2%). On the other hand, only 17.5% ate foods that are generally protein-rich such as meat (8.0%), fish (5.3%) and chicken (4.2%); and 12.7% ate milk (4.2%), beans (3.4%), vegetables (2.7%), eggs (1.9%) and fruits (1.5%). Cancers impacted food intake in about 60% of all children with cancers and affected appetite in 18.3% of them. Cancers caused vomiting in 16% and diarrhea in 6.1% of children. The majority of children with cancers (61.8%) took at least one meal while 34.4% took just snacks (p
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- 2024
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