17 research outputs found
Adaptive Radiation Survey Using an Autonomous Robot Executing LiDAR Scans in the Large Hadron Collider
No full textAt CERN, radiation surveys of equipment and beam lines are important for safety and analysis throughout the accelerator complex. Radiation measurements are highly dependent on the distance between the sensor and the radiation source. If this distance can be accurately established, the measurements can be used to better understand the radiation levels of the components and can be used for calibration purposes. When surveys are undertaken by the Train Inspection Monorail (TIM) robot, the sensor is at a constant distance from the rail, which means that it is at a known distance and height from the centre of the beam line. However, the distance of the sensor to the closest surface of the beam line varies according to what kind of equipment is installed on the beam line at this point. Ideally, a robotic survey would be completed with online adaption of the sensor position according to the equipment present in the LHC. This new approach establishes a scan of the surface with a 2D LiDAR while moving along the tunnel axis in order to obtain a 3D scan of the environment. This 3D scan will be used to generate online trajectories that will allow the robot to accurately follow the beam line and thus measure the radiation levels.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Human-Robot Interactio
Experimental Closed-Loop Excitation of Nonlinear Normal Modes on an Elastic Industrial Robot
No full textAdding elastic elements to the mechanical structure should enable robots to perform efficient oscillatory tasks. Still, even characterizing natural oscillations in nonlinear systems is a challenge in itself, which nonlinear modal theory promises to solve. Therein eigenmanifolds generalize eigenspaces to mechanical systems with non-Euclidean metrics and thus characterize families of oscillations that are autonomous evolutions of the robot. Eigenmanifolds likewise provide a framework for deriving feedback controllers to excite and sustain these oscillations. Nevertheless, these results have been so far essentially theoretical. They have been applied on relatively low dimensional systems and almost exclusively in simulation. We aim to bridge the theory to the real-world gap with the present work and show that we can excite nonlinear modes in complex systems. To this end, we propose control strategies that can simultaneously stabilize numerically evaluated eigenmanifolds and sustain oscillations in the presence of dissipation. We then focus on the KUKA iiwa with simulated parallel springs as an example of the highly nonlinear and articulated system. We calculate all the nonlinear modes of the system, and we use the proposed strategies to excite the associated natural oscillations
The ‘Second Journey’ (Al-Rihla al-thaniya) of Muhammad al-Muwaylihi’s Hadith ͑Isa Ibn Hisham Revisited
No full textIn this chapter, the author discusses the second part of Muhammad al-Muwaylihi's Hadith ʻIsa Ibn Hisham, the ‘second journey’ (Al-Rihla al-thaniya). The author published his Oxford DPhil thesis of 1968, a translation and commentary on Hadith ʻIsa Ibn Hisham, in book form upon the suggestion of Mustafa Badawi. It appeared in 1992 as A Period of Time (Fatra min al-zaman). Later in the 1990s another Egyptian scholar, Gaber Asfour, requested the author to prepare for publication the complete works of Muhammad al-Muwaylihis and his father Ibrahim. These also appeared in Cairo in 2002 and 2007 respectively. The author first provides a background on al-Muwaylihi's ‘first journey’ in Hadith ʻIsa Ibn Hisham before turning to Al-Rihla al-thaniya, al-Muwaylihi's account of his visit to Paris.</p
Thermodynamic topology of black holes within Tsallis statistics
No full textIn this paper, we investigate the thermodynamic topology of black holes within the framework of Tsallis statistics. By integrating Tsallis non-extensive statistics with topological thermodynamics, we analyze the local and global stability of various black hole solutions, including Schwarzschild, Reissner–Nordström, and higher-dimensional black holes. The introduction of Tsallis entropy, parameterized by the non-extensive parameter, δ, results in distinct thermodynamic behaviors depending on its value. Employing Duan's ϕ-mapping theory, we classify the thermodynamic topology of four-dimensional Schwarzschild black holes and non-charged higher-dimensional uncharged black holes into three distinct classes based on their topological number W: stable (W=+1), unstable (W=−1), and critical (W=0). Additionally, the thermodynamic topology of Reissner–Nordström and charged higher-dimensional charged black holes is categorized into two classes, where W=+1 indicates a stable class and W=0 represents a less stable class. Our study further demonstrates that the number of dimensions does not affect the topological thermodynamics within the context of non-extensive statistics. This approach provides novel insights into the interplay between Tsallis statistics and black hole thermodynamics, underscoring the pivotal role of topology in understanding black hole physics
Barrow Entropy and AdS Black Holes in RPS Thermodynamics
No full textIn this paper, we examine the restricted phase space (RPS) thermodynamics for
charged AdS black holes by considering the impact of quantum gravity on the
event horizon area. The primary aim of this work is to elucidate the influence
of quantum gravitational effects on thermodynamic behaviors, critical
phenomena, phase transitions, and the stability of black holes. We observe that
charged AdS black holes exhibit thermodynamic behavior similar to that of Van
der Waals fluids when influenced by quantum gravity. Furthermore, we introduce
a novel black hole thermodynamic phenomenon, which we term ``resistance of
phase transitions". Our study uncovers a violation of the homogeneity property
of the Smarr relation in RPS thermodynamics due to the effects of quantum
gravity.Comment: 11 pages, 4 figure
Constraints on the reheating phase after Higgs inflation in the hybrid metric-Palatini approach
No full textIn this paper, we study the post-inflationary era called reheating stage. For
this purpose, we consider a model in which the inflaton is non-minimally
coupled to the curvature within the hybrid metric-Palatini approach.
Furthermore, to investigate the consistency of our results with the
observational data, we relate reheating parameters to those of inflation model.
By taking into consideration the Higgs potential ; we
derive the necessary quantities needed to obtain the reheating duration and the
reheating temperature. Moreover, we plot reheating e-folds and temperature as a
function of the spectral index, respectively. We consider three cases depending
on the coupling constant . In addition, we use some specific values of the
effective equation of state , which is presumed to remain relatively
constant within the range of . We find
that for our results are in agreement with the recent Planck
data as the reheating instant is corresponding to the central value of the
spectral index and to a maximum temperature required by the scale of
baryogenesis models.Comment: 10 pages, 7 figure
Primordial black holes in Gauss-Bonnet gravity
No full textIn this paper, we investigate the production of primordial black holes (PBHs) during the preheating era. Indeed, the amplification of field fluctuations can lead to the amplification of curvature perturbations. The overproduction of primordial black holes can occur if curvature perturbations on small scales are sufficiently large. In this study, we explore the Gauss-Bonnet inflation model with Power-law potential, V(ϕ)=V0ϕn, and monomial Gauss-Bonnet coupling function, ξ(ϕ)=ξ0ϕn. Additionally, we examine a two-field preheating model with a quadratic inflaton potential. After that, we calculate and present the mass variance and the fraction of the total energy density collapsing into PBHs taking into account some specific values of the parameter, α, relating the dimensionless constants of the power-law potential and the monomial coupling function, for n=2. Our findings indicate that the PBHs production is influenced by the model parameter with an increasing probability of PBHs production as α increases. Furthermore, the duration of preheating, mΔt, affects the range of k/kend within which PBHs production is consistent with observations. Finally, we study the abundance of PBHs produced. In the case where mΔt=10 and n=2, we find that PBHs can constitute a fraction of the present dark matter in the Universe for the three considered values of α, namely α=−1.5×10−6,−2×10−6 and −2.5×10−6
Higgs inflation model with non-minimal coupling in hybrid Palatini approach
No full textThe inflation model with non-minimal coupling scalar field in the context of
the hybrid metric Palatini is studied in this paper. We derive the Einstein's
field equations, the equations of motion of the scalar field. Furthermore,the
background and the perturbative parameters are obtained by means of Friedmann
equation in the slow roll regime. The analysis of cosmological perturbations
allowed us to obtain the main inflationary parameters such as the scalar
spectral index and the tensor to scalar ratio . In this perspective,
as an application of our analysis, we consider the Higgs field with quartic
potential which plays the inflaton role, and we show that the predictions of
Higgs hybrid inflation are in good agreement with recent observational data
\cite{Akrami:2018odb}.Comment: 9 pages, 4 figure
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Short-Term Forecasting of Electric Loads Using Nonlinear Autoregressive Artificial Neural Networks with Exogenous Multivariable Inputs
No full textShort-term load forecasting is crucial for the operations planning of an electrical grid. Forecasting the next 24 h of electrical load in a grid allows operators to plan and optimize their resources. The purpose of this study is to develop a more accurate short-term load forecasting method utilizing non-linear autoregressive artificial neural networks (ANN) with exogenous multi-variable input (NARX). The proposed implementation of the network is new: the neural network is trained in open-loop using actual load and weather data, and then, the network is placed in closed-loop to generate a forecast using the predicted load as the feedback input. Unlike the existing short-term load forecasting methods using ANNs, the proposed method uses its own output as the input in order to improve the accuracy, thus effectively implementing a feedback loop for the load, making it less dependent on external data. Using the proposed framework, mean absolute percent errors in the forecast in the order of 1\% have been achieved, which is a 30\% improvement on the average error using feedforward ANNs, ARMAX and state space methods, which can result in large savings by avoiding commissioning of unnecessary power plants. In addition, in order to improve the robustness of the forecast to variations in the number of neurons and other network parameters, the author proposes a method using an exponential decay of the error weights for training the neural network. The modification consists in giving higher error weight to more recent values and lower weight to older values of the training set. By doing this, mover recent values have a higher influence on the calculation of the synaptic weights and therefore the forecast produced by the NARX network is more accurate. This method, combined with the use of Bayesian regularization for training, results in improved forecast accuracy of up to 25\% and robustness to variation in parameter selection. The New England electrical load data are used to train and validate the forecast prediction.</p
