Search Results (5,916)

Attitude information is as important as position information in describing and localizing objects. Based on this, this paper proposes a method for object attitude sensing utilizing ultra-high frequency passive RFID technology. This method adopts a double tag array strategy, which effectively enhances the spatial freedom and eliminates phase ambiguity by leveraging the phase difference information between the two tags. Additionally, we delve into the issue of the phase shift caused by coupling interference between the two tags. To effectively compensate for this coupling effect, a series of experiments were conducted to thoroughly examine the specific impact of coupling effects between tags, and based on these findings, a coupling model between tags was established. This model was then integrated into the original phase model to correct for the effects of phase shift, significantly improving the sensing accuracy. Furthermore, we considered the influence of the object rotation angle on phase changes to construct an accurate object attitude recognition and tracking model. To reduce random errors during phase measurement, we employed a polynomial regression method to fit the measured tag phase information, further enhancing the precision of the sensing model. Compared to traditional positioning modes, the dual-tag array strategy essentially increases the number of virtual antennas available for positioning, providing the system with more refined directional discrimination capabilities. The experimental results demonstrated that incorporating the effects of inter-tag coupling interference and rotation angle into the phase model significantly improved the recognition accuracy for both object localization and attitude angle determination. Specifically, the average error of object positioning was reduced to 12.3 cm, while the average error of attitude angle recognition was reduced to 8.28°, making the method suitable for various practical application scenarios requiring attitude recognition. Full article

Virtual studies involving pedestrians have gained relevance due to the advantage of not exposing them to actual risk, and simulation setups have benefitted from rapid technical advancements, becoming increasingly complex and immersive. However, it remains unclear whether complex setups affecting participants’ freedom of movement impact their decision-making. This research evaluated the effects of a more realistic approach to studying pedestrian crossing behavior by comparing a perception-action task requiring participants to walk effectively along a semi-virtual crosswalk with a similar experiment using static crossing conditions. Using a CAVE system, two real-world streets were modeled in two different virtual scenarios, varying vehicle speed patterns and distance from the crosswalk. Visual stimuli were presented to two groups of 30 participants, with auditory stimuli adapted accordingly. The impact of various factors on participants’ crossing decisions was evaluated by examining the percentage of crossings, crossing start time, and time-to-passage. Overall, the experimental approach did not significantly affect participants’ crossing decisions. Full article

Background: Aortic coarctation, a condition characterized by localized narrowing of the aorta, can be managed with either surgical or endovascular techniques. This study aims to compare these approaches concerning long-term outcomes, particularly re-coarctation rates and late arterial hypertension. Methods: We retrospectively analyzed data from patients with native, isolated aortic coarctation treated by surgical or endovascular methods between 2015 and 2024. Clinical and demographic data were collected from electronic health records. Blood pressure was measured using oscillometric devices, and transthoracic echocardiography (TTE) was performed by an experienced sonographer. The primary endpoint was to identify which treatment predicted re-coarctation during follow-up, while the secondary endpoint assessed the incidence of late arterial hypertension. Results: Sixty-nine patients were included, with a mean age of 18.14 ± 8.18 years (median 16 years; range 8 to 37 years) and a median follow-up of 3 years (range 6 months to 8 years). Of these, 67 (97.1%) underwent elective repairs. Repair techniques included endovascular treatment (24.6%), surgical end-to-end anastomosis (47.8%), and surgical patchplasty (27.5%). The endovascular group was significantly older (29.82 ± 5.9 years vs. 14.33 ± 4.25 years, p = 0.056) and had shorter procedure durations and hospital stays. One-year freedom from reintervention was significantly higher in the surgical group (98.7%) compared to the endovascular group (88.23%) (p < 0.001). Conclusions: Both techniques effectively treat aortic coarctation, but surgical repair offers better long-term outcomes, while endovascular repair provides shorter recovery times. These findings should inform the choice of treatment modality based on patient-specific factors and clinical priorities. Full article

The nutritional utility of leguminous products such as corticated marama bean (Tylosema esculentum) meal (CMBM) in quail diets is limited by high fibre levels. This study evaluated the impact of dietary CMBM pre-treated with fibrolytic multi-enzyme (FMENZ) on growth performance, and physiological and meat quality responses in Jumbo Coturnix quail. Two hundred and forty 7-day-old Jumbo quail (29.4 ± 2.72 g initial live weight) were randomly distributed to five experimental diets, with six replicate cages each (eight birds/cage). The diets were a grower diet without CMBM, and the same grower diet plus 100 g/kg CMBM pre-treated with 0, 1, 1.5, and 2% (v/w) FMENZ. Positive quadratic responses (p < 0.05) were recorded for overall feed intake and body weight gain in weeks 2 and 3. The control diet promoted the highest (p < 0.05) gain-to-feed ratio in weeks 2 and 3, and the best weight gains and glucose levels, but reduced lipase levels. Final body weights declined linearly [p = 0.037] with FMENZ levels. Breast pH increased linearly, while haemoglobin and 1 h post-mortem chroma showed positive quadratic effects (p < 0.05) with FMENZ levels. The use of the enzymes did not improve the feed value of CMBM in Jumbo quail diets. Full article

Effects of the road, such as speed bumps, can significantly affect a car’s stability. This study focuses on how a quarter-car model is affected by a basic harmonic speed hump and how Cubic Negative Velocity Control (CNVC) is used to control the amplitude of disturbances. This study differs from earlier research in considering various control and force kinds that impact the system. The external forces in this context are a component of a non-linear dynamic system. Two-degree-of-freedom (2DOF) differential coupled equations describe the system’s equation. Numerous numerical experiments have been conducted, including proportional derivative (PD), negative derivative feedback (NDF), positive position feedback (PPF), linear negative velocity control (LNVC), and CNVC; the results show that when the hump is represented as a simple harmonic hump, CNVC has the best effect and can regulate vibrations more precisely than the other approaches on this system. Subsequently, the vibration value of the system was numerically analyzed both before and after the control was implemented. Using the frequency response equation and phase plane approaches in conjunction with the Runge–Kutta fourth order method (RK-4) in the context of resonance situation analysis, the stability of the numerical solution has been evaluated. Full article

The use of inertial measurement units (IMUs) as an alternative to optical marker-based systems has the potential to make gait analysis part of the clinical standard of care. Previously, an IMU-based system leveraging Rauch–Tung–Striebel smoothing to estimate knee angles was assessed using a six-degrees-of-freedom joint simulator. In a clinical setting, however, accurately measuring abduction/adduction and external/internal rotation of the knee joint is particularly challenging, especially in the presence of soft tissue artefacts. In this study, the in vivo IMU-based joint angles of 40 asymptomatic knees were assessed during level walking, under two distinct sensor placement configurations: (1) IMUs fixed to a rigid harness, and (2) IMUs mounted on the skin using elastic hook-and-loop bands (from here on referred to as “skin-mounted IMUs”). Estimates were compared against values obtained from a harness-mounted optical marker-based system. The comparison of these three sets of kinematic signals (IMUs on harness, IMUs on skin, and optical markers on harness) was performed before and after implementation of a REference FRame Alignment MEthod (REFRAME) to account for the effects of differences in coordinate system orientations. Prior to the implementation of REFRAME, in comparison to optical estimates, skin-mounted IMU-based angles displayed mean root-mean-square errors (RMSEs) up to 6.5°, while mean RMSEs for angles based on harness-mounted IMUs peaked at 5.1°. After REFRAME implementation, peak mean RMSEs were reduced to 4.1°, and 1.5°, respectively. The negligible differences between harness-mounted IMUs and the optical system after REFRAME revealed that the IMU-based system was capable of capturing the same underlying motion pattern as the optical reference. In contrast, obvious differences between the skin-mounted IMUs and the optical reference indicated that the use of a harness led to fundamentally different joint motion being measured, even after accounting for reference frame misalignments. Fluctuations in the kinematic signals associated with harness use suggested the rigid device oscillated upon heel strike, likely due to inertial effects from its additional mass. Our study proposes that optical systems can be successfully replaced by more cost-effective IMUs with similar accuracy, but further investigation (especially in vivo and upon heel strike) against moving videofluoroscopy is recommended. Full article

This article offers a fresh exegesis of Heidegger’s philosophy of art, focusing on his conceptualization of artwork as the reproduction of the thing’s general essence. Grounding the analysis in Heidegger’s revisit of Kant’s Transcendental Aesthetic, this study explores Heidegger’s interpretation of a thing as a “composed homogeneity” that reveals inherent determinations of temporality and spatiality in the self-presence of beings as a phenomenon grasped within finite human cognition. This is inextricably linked to the ecstatic temporality of Dasein, elucidating a cyclical human–thing dynamic integral to Heidegger’s ontology. Going deeper, I draw parallels between Kant’s “supersensible” realm and Heidegger’s “earth”, revealing a teleological (ethical) design manifested in art that captures the dual essence of Nature—using Kantian terminology, its purposiveness and contrapurposiveness—intersecting with Heidegger’s notion of the counter-essence of ἀλήθεια in relation to freedom. Finally, I show how the manifold aesthetic metamorphoses of this existential scheme within the existentiell ordinariness through nonradiant φαίνεσθαι, such as equipmentality, emerge as the everyday incarnation of this design. Full article

Hydrokinetic arrays, or farms, offer a promising solution to the global energy crisis by enabling cost-effective and environmentally friendly energy generation in locations with water flows. This paper presents research focused on the design and optimization of a Gorlov-type vertical-axis hydrokinetic turbine array for power generation. The study involved (i) numerical simulations using computational fluid dynamics (CFD) software with the six degrees of freedom (6DoF) tool, (ii) optimization techniques such as response surface methodology, and (iii) experimental testing in natural environments. The objective was to develop an efficient system with low manufacturing and maintenance costs. A key finding was that the separation distance between rotors, both along and across the fluid flow, is a critical parameter in designing hydrokinetic arrays. For this study, a triangular array configuration, termed Triframe, was used, consisting of three Gorlov-type turbines with four blades each. The optimization process led to separation distances based on the diameter (D) of the turbines, with 15.9672D along the fluid flow (X) and 4.15719D across the flow (Y). Finally, an experimental scale model of the hydrokinetic array was successfully constructed and characterized, demonstrating the effectiveness of the optimization process described in this study. Full article

In contemporary society, the internet, particularly social media, has become a significant area where individuals spend considerable amounts of time engaging in various activities. Concurrently, the growing utilization of artificial intelligence (AI) has emerged as a critical component of the propaganda that is disseminated online within economic, social, and political spheres. AI encompasses a broad range of applications, including data collection for microtargeting and the dissemination of diverse forms of disinformation. Additionally, AI can be effectively employed to detect and remove content from social media platforms that contradicts democratic principles, such as disinformation or hate speech. This study reviews the existing literature on the use of AI in political propaganda, examining not only how AI has become an integral part of propaganda strategies, but also how it is utilized to counter propaganda that violates democratic values. It explores the legislation in various countries that enables (and mandates) the removal of propaganda content contrary to democratic principles from social media platforms with the assistance of AI, and it discusses perspectives that highlight the potential conflict between these practices and the principle of freedom of expression. Full article

With the development of unmanned aircraft and artificial intelligence technology, the future of air combat is moving towards unmanned and autonomous direction. In this paper, we introduce a new layered decision framework designed to address the six-degrees-of-freedom (6-DOF) aircraft within-visual-range (WVR) air-combat challenge. The decision-making process is divided into two layers, each of which is addressed separately using reinforcement learning (RL). The upper layer is the combat policy, which determines maneuvering instructions based on the current combat situation (such as altitude, speed, and attitude). The lower layer control policy then uses these commands to calculate the input signals from various parts of the aircraft (aileron, elevator, rudder, and throttle). Among them, the control policy is modeled as a Markov decision framework, and the combat policy is modeled as a partially observable Markov decision framework. We describe the two-layer training method in detail. For the control policy, we designed rewards based on expert knowledge to accurately and stably complete autonomous driving tasks. At the same time, for combat policy, we introduce a self-game-based course learning, allowing the agent to play against historical policies during training to improve performance. The experimental results show that the operational success rate of the proposed method against the game theory baseline reaches 85.7%. Efficiency was also outstanding, with an average 13.6% reduction in training time compared to the RL baseline. Full article

EELS-DARTS is a simulator designed for autonomy development and analysis of large degree of freedom snake-like robots for space exploration. A detailed description of the EELS-DARTS simulator design is presented. This includes the versatile underlying multibody dynamics representation used to model a variety of distinct snake robot configurations as well as an anisotropic friction model for describing screw–ice interaction. Additional simulation components such as graphics, importable terrain, joint controllers, and perception are discussed. Methods for setting up and running simulations are discussed, including how a snake robot’s autonomy stack closes the commands and information loop with the simulation via ROS. Multiple use cases are described to illustrate how the simulation is used to aid and inform robot design, autonomy development, and field test use throughout the project’s life cycle. A validation analysis of the screw–ice contact model is performed for the surface mobility case. Lastly, an overview of simulation use for planning operations during a recent field test to the Athabasca Glacier in Canada is discussed. Full article

Trajectory interception is a critical synchronization element in the transportation and manufacturing sectors using robotic platforms. This is usually performed by matching the position and velocity of a target object with the position and velocity of the robot interceptor. However, the synchronization task is exasperated by (i) the proper gain tuning of the controller, (ii) the dynamic response of the robotic platform, (iii) the velocity constraints in the actuators, and (iv) the trajectory profile exhibited by the moving object. This means that the interception time is not controlled, which is critical for energy optimization, resources, and production. This paper proposes a prescribed time trajectory interception algorithm for robot manipulators. The approach uses the finite-time convergence properties of sliding mode control combined with a terminal attractor based on a time base generator. The combined approach guarantees trajectory interception in a prescribed time with robust properties. Simulation studies are conducted using the first three degrees of freedom (DOFs) of a RV-M1 robot under single- and multi-object interception tasks. The results verify the effectiveness of the proposed methodology under different hyperparameter configurations. Full article

This technical study on strengthening a five-story building in Bucharest, a city known for its high seismic activity in Europe, required implementing a base-isolation system as part of the rehabilitation solution. The main challenge was assembling the elastomeric equipment system at the base of the building and the structural system, which was considered a rigid solid with six degrees of dynamic freedom. This required defining and solving differential equations of motion for earthquake action. It was determined that switching from a six-DoF system to a three-DoF system and then customizing the results for one DoF was justified. The analysis involved designing an isolation system with elastomeric anti-seismic devices and using a dynamic model with degrees of freedom to calculate the response for the first mode (fundamental) of seismic action from the spectral composition of an earthquake. The variation in amplitudes in the three zones—pre-resonance, at resonance and after resonance—is of great interest from a practical and design perspective. Also, the support solution was optimized in terms of the isolators’ location and the stiffness and damping parameters so that the degree of dynamic isolation could be achieved at the highest possible values (I ≥ 60%). Full article

This paper presents novel chattering-free robust control strategies for addressing disturbances and uncertainties in a two-degree-of-freedom (2-DOF) unmanned aerial vehicle (UAV) dynamic model, with a focus on the highly nonlinear and strongly coupled nature of the system. The novelty lies in the development of sliding mode control (SMC), integral sliding mode control (ISMC), and terminal sliding mode control (TSMC) laws specifically tailored for the twin-rotor MIMO system (TRMS). These strategies are validated through both simulation and real-time experiments. A key contribution is the introduction of a uniform robust exact differentiator (URED) to recover rotor speed and missing derivatives, combined with a nonlinear state feedback observer to improve system observability. A feedback linearization approach, using lie derivatives and diffeomorphism principles, is employed to decouple the system into horizontal and vertical subsystems. Comparative analysis of the transient performance of the proposed controllers, with respect to metrics such as settling time, overshoot, rise time, and steady-state errors, is provided. The ISMC method, in particular, effectively mitigates the chattering issue prevalent in traditional SMC, improving both system performance and actuator longevity. Experimental results on the TRMS demonstrate the superior tracking performance and robustness of the proposed control laws in the presence of nonlinearities, uncertainties, and external disturbances. This research contributes a comprehensive control design framework with proven real-time implementation, offering significant advancements over existing methodologies. Full article

Objectives: To review the evidence on the clinical value of magnetic source imaging (MSI) in patients with refractory focal epilepsy without evidence for an epileptogenic lesion on magnetic resonance imaging (“MRI-negative” or “non-lesional MRI”). Methods: We conducted a systematic literature search on PUBMED, which was extended by researchrabbit.ai using predefined criteria to identify studies that applied MSI in MRI-negative patients with epilepsy. We extracted data on patient characteristics, MSI methods, localization results, surgical outcomes, and correlation with other modalities. Results: We included 23 studies with a total of 512 non-lesional epilepsy patients who underwent MSI. Most studies used equivalent current dipole (ECD) models to estimate the sources of interictal epileptic discharges (IEDs). MEG detected IEDs in 32–100% of patients. MSI results were concordant with other modalities, such as EEG, PET, and SPECT, in 3892% of cases. If MSI concordant surgery was performed, 52–89% of patients achieved seizure freedom. MSI contributed to the decision-making process in 28–75% of cases and altered the surgical plan in 5–33% of cases. Conclusions: MSI is a valuable diagnostic tool for MRI-negative patients with epilepsy, as it can detect and localize IEDs with high accuracy and sensitivity, and provides useful information for surgical planning and predicts outcomes. MSI can also complement and refine the results of other modalities, such as EEG and PET, and optimize the use of invasive recordings. MSI should be considered as part of the presurgical evaluation, especially in patients with non-lesional refractory epilepsy. Full article