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16 pages, 380 KB  
Systematic Review
The Value of Interventions Aimed at Improving the Patient Experience: Systematic Review of Economic Impacts and Provider Well-Being Outcomes
by Tiago S. Jesus, Dongwook Lee, Brocha Z. Stern, Manrui Zhang, Jan Struhar, Allen W. Heinemann, Anne Deutsch and Neil Jordan
Healthcare 2025, 13(13), 1622; https://doi.org/10.3390/healthcare13131622 - 7 Jul 2025
Viewed by 826
Abstract
Background: Although improving the patient experience with care is being framed as part of value-based care, the economic and provider well-being impact of interventions for improving the patient experience has not been established. We aimed to synthesize the contemporary (2015–2024) empirical literature on [...] Read more.
Background: Although improving the patient experience with care is being framed as part of value-based care, the economic and provider well-being impact of interventions for improving the patient experience has not been established. We aimed to synthesize the contemporary (2015–2024) empirical literature on the economic (e.g., costs, revenue) and other value-based impacts (e.g., provider well-being) of patient-experience improvement interventions. Methods: Systematic review using six databases of scientific literature (PubMed, EconLit, CINAHL, PsycINFO, DOAJ, and Scopus) supplemented by journal-specific and snowball searches following a registered study protocol (PROSPERO: CRD42022358337). Two independent reviewers performed eligibility decisions and quality appraisals of the study methods and economic assessments, when applicable; the latter was conducted using the Joanna Briggs Institute’s checklist for economic evaluations. Results: Out of 1317 unique references, nine were included. Four studies assessed the effectiveness of patient experience improvement interventions (e.g., provider communication training, discharge or transitional support) coupled with economic evaluations; these found statistically significant positive outcomes for both patient experience and economic dimensions—including reduced costs, improved revenue, or additional costs offset by increased revenue. Three additional studies on provider communication training also found statistically significant positive impacts on provider well-being (i.e., reduced burnout) and patient experience improvements. Conclusion: These findings shed light on the overall synergistic value of and business case for investments into developing patient experience improvement programs or activities. However, there is room for strengthening this body of knowledge in scope, volume, and method quality, including the need to study the impact on patient experience, provider well-being, health outcomes, and costs (i.e., the quadruple aim) in tandem. Full article
(This article belongs to the Special Issue Patient Experience and the Quality of Health Care)
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26 pages, 11590 KB  
Article
Towards Geodetic Datum Modernization: A Comparative Study of GNSS Solutions in KGD2002 Using GAMIT/GLOBK and Bernese
by Seung-Jun Lee and Hong-Sik Yun
Appl. Sci. 2025, 15(12), 6460; https://doi.org/10.3390/app15126460 - 8 Jun 2025
Viewed by 683
Abstract
This study evaluates coordinate consistency in the static Korean Geodetic Datum 2002 (KGD2002) by comparing GNSS station positions derived independently from GAMIT/GLOBK and Bernese software. Using a nationwide network of approximately 3000 unified geodetic control points (UGCPs), we analyze horizontal coordinate differences (ΔN, [...] Read more.
This study evaluates coordinate consistency in the static Korean Geodetic Datum 2002 (KGD2002) by comparing GNSS station positions derived independently from GAMIT/GLOBK and Bernese software. Using a nationwide network of approximately 3000 unified geodetic control points (UGCPs), we analyze horizontal coordinate differences (ΔN, ΔE) to identify regional patterns and potential systematic biases. The results indicate that both solutions are closely aligned with the official KGD2002 coordinates, generally within a few millimeters to sub-centimeter levels. However, small regional discrepancies are evident; for example, some provinces exhibit consistent mean northward or southward offsets on the order of 0.1–0.3 cm, and greater dispersions—up to 2 cm—are observed in peripheral regions such as Jeollanam. Notably, the Bernese solution demonstrates slightly tighter agreement, with lower standard deviations compared to GAMIT/GLOBK. The application of two distinct processing strategies within a unified static reference frame is a novel aspect of this study, revealing subtle differences attributable to network geometry, environmental factors, and software modeling approaches. The findings also underscore the limitations of KGD2002’s static nature, particularly its fixed epoch and lack of motion modeling. In response to these issues, this study discusses the rationale for transitioning to a dynamic geodetic reference frame, such as ITRF2020, to improve compatibility with international systems and account for ongoing crustal motions. Overall, the results provide a foundation for the future modernization of Korea’s spatial reference infrastructure and highlight the importance of adopting time-dependent datums in geodetic applications. Full article
(This article belongs to the Section Earth Sciences)
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13 pages, 679 KB  
Article
Waiting Time and Focus of Physical Therapy for Children with Cerebral Palsy in Saudi Arabia: Parents’ Report
by Abdulrhman Mashabi, Maysoun N. Saleh, Ahmad A. Alharbi, Abdulaziz A. Albalwi, Hani F. Albalawi and Qais Al-Bakri
Children 2025, 12(5), 544; https://doi.org/10.3390/children12050544 - 24 Apr 2025
Viewed by 776
Abstract
Background: Physical therapy is crucial in the rehabilitation of children with cerebral palsy (CP), aiming to enhance motor function, postural control, and functional independence. Objective: The study explored the current physical therapy interventions for children with CP in Saudi Arabia, including waiting time, [...] Read more.
Background: Physical therapy is crucial in the rehabilitation of children with cerebral palsy (CP), aiming to enhance motor function, postural control, and functional independence. Objective: The study explored the current physical therapy interventions for children with CP in Saudi Arabia, including waiting time, the most used interventions, the focus of therapy, and parents’ desired goals. Methods: A cross-sectional study was conducted involving 215 children with CP (aged 6 months to 18.2 years). Face-to-face surveys were conducted to collect data on CP classification (based on the Gross Motor Function Classification System), age at first referral, types of interventions used, intervention goals, and parents’ desired goals for their children. Results: Children with severe CP (non-ambulators) received physical therapy services significantly earlier than those with milder involvement (ambulators). The most commonly used interventions were therapeutic exercises and home exercises, followed by standing frames. Hydrotherapy was the least utilized intervention. The focus of therapy was mainly on joints and muscles, as well as mobility and transfers. Conclusions: The study underscores the need to identify and refer children with CP for physical therapy. The findings suggest further investigation into barriers to utilizing certain interventions like hydrotherapy and emphasize the need for more inclusive goal-setting processes in the rehabilitation of children with CP based on both physical therapy and parent perspectives. Full article
(This article belongs to the Section Pediatric Neurology & Neurodevelopmental Disorders)
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22 pages, 6390 KB  
Article
A Posture Training System Based on Therblig Analysis and YOLO Model—Taking Erhu Bowing as an Example
by Bonnie Lu, Chao-Li Meng and Chyi-Ren Dow
Sensors 2025, 25(3), 674; https://doi.org/10.3390/s25030674 - 23 Jan 2025
Viewed by 1271
Abstract
Computer-assisted learning can help erhu learners to analyze their playing performance and identify areas for improvement. Therefore, in this study, a computerized system based on a You Only Look Once (YOLO)-OD model was developed for erhu bowing training. First, Therblig analysis was performed [...] Read more.
Computer-assisted learning can help erhu learners to analyze their playing performance and identify areas for improvement. Therefore, in this study, a computerized system based on a You Only Look Once (YOLO)-OD model was developed for erhu bowing training. First, Therblig analysis was performed to segment the erhu bowing process into multiple steps, which were then analyzed thoroughly to identify critical objects for detection. Second, a YOLO-OD model was developed to detect and track the critical objects identified in video frames. Third, scoring methodologies were developed for bow level and bow straightness. The YOLO-OD model and the aforementioned scoring methodologies were incorporated into a computerized training system for erhu bowing, which enables erhu learners to practice independently. It provides scores for bow level and bow straightness, allowing learners to evaluate their technique, as well as feedback and instant alerts regarding incorrect motions and postures, which enable learners to adjust their actions and postures in real time. In addition, teachers or coaches can refer to the videos and other data collected using the proposed system in order to identify problematic erhu bowing techniques and provide students with relevant suggestions and feedback. Full article
(This article belongs to the Section Sensing and Imaging)
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13 pages, 2064 KB  
Article
A Robust Method for Validating Orientation Sensors Using a Robot Arm as a High-Precision Reference
by József Kuti, Tamás Piricz and Péter Galambos
Sensors 2024, 24(24), 8179; https://doi.org/10.3390/s24248179 - 21 Dec 2024
Cited by 2 | Viewed by 1677
Abstract
This paper presents a robust and efficient method for validating the accuracy of orientation sensors commonly used in practical applications, leveraging measurements from a commercial robotic manipulator as a high-precision reference. The key concept lies in determining the rotational transformations between the robot’s [...] Read more.
This paper presents a robust and efficient method for validating the accuracy of orientation sensors commonly used in practical applications, leveraging measurements from a commercial robotic manipulator as a high-precision reference. The key concept lies in determining the rotational transformations between the robot’s base frame and the sensor’s reference, as well as between the TCP (Tool Center Point) frame and the sensor frame, without requiring precise alignment. Key advantages of the proposed method include its independence from the exact measurement of rotations between the reference instrumentation and the sensor, systematic testing capabilities, and the ability to produce repeatable excitation patterns under controlled conditions. This approach enables automated, high-precision, and comparative evaluation of various orientation sensing devices in a reproducible manner. Moreover, it facilitates efficient calibration and analysis of sensor errors, such as drift, noise, and response delays under various motion conditions. The method’s effectiveness is demonstrated through experimental validation of an Inertial Navigation System module and the SLAM-IMU fusion capabilities of the HTC VIVE VR headset, highlighting its versatility and reliability in addressing the challenges associated with orientation sensor validation. Full article
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13 pages, 2635 KB  
Article
Decoupled Cross-Modal Transformer for Referring Video Object Segmentation
by Ao Wu, Rong Wang, Quange Tan and Zhenfeng Song
Sensors 2024, 24(16), 5375; https://doi.org/10.3390/s24165375 - 20 Aug 2024
Cited by 1 | Viewed by 1472
Abstract
Referring video object segmentation (R-VOS) is a fundamental vision-language task which aims to segment the target referred by language expression in all video frames. Existing query-based R-VOS methods have conducted in-depth exploration of the interaction and alignment between visual and linguistic features but [...] Read more.
Referring video object segmentation (R-VOS) is a fundamental vision-language task which aims to segment the target referred by language expression in all video frames. Existing query-based R-VOS methods have conducted in-depth exploration of the interaction and alignment between visual and linguistic features but fail to transfer the information of the two modalities to the query vector with balanced intensities. Furthermore, most of the traditional approaches suffer from severe information loss in the process of multi-scale feature fusion, resulting in inaccurate segmentation. In this paper, we propose DCT, an end-to-end decoupled cross-modal transformer for referring video object segmentation, to better utilize multi-modal and multi-scale information. Specifically, we first design a Language-Guided Visual Enhancement Module (LGVE) to transmit discriminative linguistic information to visual features of all levels, performing an initial filtering of irrelevant background regions. Then, we propose a decoupled transformer decoder, using a set of object queries to gather entity-related information from both visual and linguistic features independently, mitigating the attention bias caused by feature size differences. Finally, the Cross-layer Feature Pyramid Network (CFPN) is introduced to preserve more visual details by establishing direct cross-layer communication. Extensive experiments have been carried out on A2D-Sentences, JHMDB-Sentences and Ref-Youtube-VOS. The results show that DCT achieves competitive segmentation accuracy compared with the state-of-the-art methods. Full article
(This article belongs to the Special Issue AI-Driven Sensing for Image Processing and Recognition)
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15 pages, 270 KB  
Article
Topological Crystals: Independence of Spectral Properties with Respect to Reference Systems
by Koichi Kato and Serge Richard
Symmetry 2024, 16(8), 1073; https://doi.org/10.3390/sym16081073 - 19 Aug 2024
Viewed by 900
Abstract
It is a common postulate that spectral properties of operators describing physical systems are independent of the underlying reference frames. For the Laplace operator on topological crystals, we prove such a statement from a deeper analysis of the behavior of spectral properties with [...] Read more.
It is a common postulate that spectral properties of operators describing physical systems are independent of the underlying reference frames. For the Laplace operator on topological crystals, we prove such a statement from a deeper analysis of the behavior of spectral properties with respect to arbitrary choices. In particular, we investigate the impact of the choice of a unit cell, and of the choice of a family of generators for the transformation group. Full article
(This article belongs to the Section Mathematics)
14 pages, 6358 KB  
Article
Practical Performance Analysis of MDI-QKD with Orbital Angular Momentum on UAV Relay Platform
by Dan Wu, Jiahao Li, Lan Yang, Zhifeng Deng, Jie Tang, Yuexiang Cao, Ying Liu, Haoran Hu, Ya Wang, Huicun Yu, Jiahua Wei, Huazhi Lun, Xingyu Wang and Lei Shi
Entropy 2024, 26(8), 635; https://doi.org/10.3390/e26080635 - 27 Jul 2024
Cited by 2 | Viewed by 1975
Abstract
The integration of terrestrial- and satellite-based quantum key distribution (QKD) experiments has markedly advanced global-scale quantum networks, showcasing the growing maturity of quantum technologies. Notably, the use of unmanned aerial vehicles (UAVs) as relay nodes has emerged as a promising method to overcome [...] Read more.
The integration of terrestrial- and satellite-based quantum key distribution (QKD) experiments has markedly advanced global-scale quantum networks, showcasing the growing maturity of quantum technologies. Notably, the use of unmanned aerial vehicles (UAVs) as relay nodes has emerged as a promising method to overcome the inherent limitations of fiber-based and low-Earth orbit (LEO) satellite connections. This paper introduces a protocol for measurement-device-independent QKD (MDI-QKD) using photon orbital angular momentum (OAM) encoding, with UAVs as relay platforms. Leveraging UAV mobility, the protocol establishes a secure and efficient link, mitigating threats from untrusted UAVs. Photon OAM encoding addresses reference frame alignment issues exacerbated by UAV jitter. A comprehensive analysis of atmospheric turbulence, state-dependent diffraction (SDD), weather visibility, and pointing errors on free-space OAM-state transmission systems was conducted. This analysis elucidates the relationship between the key generation rate and propagation distance for the proposed protocol. Results indicate that considering SDD significantly decreases the key rate, halving previous data results. Furthermore, the study identifies a maximum channel loss capacity of 26 dB for the UAV relay platform. This result is pivotal in setting realistic parameters for the deployment of UAV-based quantum communications and lays the foundation for practical implementation strategies in the field. Full article
(This article belongs to the Special Issue Progress in Quantum Key Distribution)
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26 pages, 11687 KB  
Article
Investigation of a Modified Wells Turbine for Wave Energy Extraction
by Mohammad Nasim Uddin, Frimpong Opoku and Michael Atkinson
Energies 2024, 17(15), 3638; https://doi.org/10.3390/en17153638 - 24 Jul 2024
Cited by 2 | Viewed by 1690
Abstract
The Oscillating Water Column (OWC) is the most promising self-rectifying device for power generation from ocean waves; over the past decade, its importance has been rekindled. The bidirectional airflow inside the OWC drives the Wells turbine connected to a generator to harness energy. [...] Read more.
The Oscillating Water Column (OWC) is the most promising self-rectifying device for power generation from ocean waves; over the past decade, its importance has been rekindled. The bidirectional airflow inside the OWC drives the Wells turbine connected to a generator to harness energy. This study evaluated the aerodynamic performance of two hybrid airfoil (NACA0015 and NACA0025) blade designs with variable chord distribution along the span of a Wells turbine. The present work examines the aerodynamic impact of the variable chord turbine and compares it with one with a constant chord. Ideally, Wells rotor blades with variable chords perform better since they have an even axial velocity distribution on their leading edge. The variable chord rotor blade configurations differ from hub to tip with taper ratios (Chord at Tip/Chord at Hub) of 1.58 and 0.63. The computation is performed in ANSYS™ CFX 2023 R2 by solving three-dimensional, steady-state, incompressible Reynolds Averaged Navier–Stokes (RANS) equations coupled with a k-ω Shear Stress Transport (SST) turbulence model in a non-inertial reference frame rotating with the turbine. The accuracy of the numerical results was achieved by performing a grid independence study. A refined mesh showed good agreement with the available experimental and numerical data in terms of efficiency, torque, and pressure drop at different flow coefficients. A variable chord Wells turbine with a taper ratio of 1.58 had a peak efficiency of 59.6%, as opposed to the one with a taper ratio of 0.63, which had a peak efficiency of 58.2%; the constant chord Wells turbine only had a peak efficiency of 58.5%. Furthermore, the variable chord rotor with the higher taper ratio had a larger operating range than others. There are significant improvements in the aerodynamic performance of the modified Wells turbine, compared to the conventional Wells turbine, which makes it suitable for wave energy harvesting. The flow field investigation around the turbine blades was conducted and analyzed. Full article
(This article belongs to the Section A3: Wind, Wave and Tidal Energy)
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23 pages, 8941 KB  
Article
DS-Trans: A 3D Object Detection Method Based on a Deformable Spatiotemporal Transformer for Autonomous Vehicles
by Yuan Zhu, Ruidong Xu, Chongben Tao, Hao An, Huaide Wang, Zhipeng Sun and Ke Lu
Remote Sens. 2024, 16(9), 1621; https://doi.org/10.3390/rs16091621 - 30 Apr 2024
Cited by 2 | Viewed by 2270
Abstract
Facing the significant challenge of 3D object detection in complex weather conditions and road environments, existing algorithms based on single-frame point cloud data struggle to achieve desirable results. These methods typically focus on spatial relationships within a single frame, overlooking the semantic correlations [...] Read more.
Facing the significant challenge of 3D object detection in complex weather conditions and road environments, existing algorithms based on single-frame point cloud data struggle to achieve desirable results. These methods typically focus on spatial relationships within a single frame, overlooking the semantic correlations and spatiotemporal continuity between consecutive frames. This leads to discontinuities and abrupt changes in the detection outcomes. To address this issue, this paper proposes a multi-frame 3D object detection algorithm based on a deformable spatiotemporal Transformer. Specifically, a deformable cross-scale Transformer module is devised, incorporating a multi-scale offset mechanism that non-uniformly samples features at different scales, enhancing the spatial information aggregation capability of the output features. Simultaneously, to address the issue of feature misalignment during multi-frame feature fusion, a deformable cross-frame Transformer module is proposed. This module incorporates independently learnable offset parameters for different frame features, enabling the model to adaptively correlate dynamic features across multiple frames and improve the temporal information utilization of the model. A proposal-aware sampling algorithm is introduced to significantly increase the foreground point recall, further optimizing the efficiency of feature extraction. The obtained multi-scale and multi-frame voxel features are subjected to an adaptive fusion weight extraction module, referred to as the proposed mixed voxel set extraction module. This module allows the model to adaptively obtain mixed features containing both spatial and temporal information. The effectiveness of the proposed algorithm is validated on the KITTI, nuScenes, and self-collected urban datasets. The proposed algorithm achieves an average precision improvement of 2.1% over the latest multi-frame-based algorithms. Full article
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28 pages, 577 KB  
Article
Small-Scale Cosmology Independent of the Standard Model
by Georgy I. Burde
Universe 2024, 10(4), 180; https://doi.org/10.3390/universe10040180 - 13 Apr 2024
Viewed by 1516
Abstract
‘Small-scale cosmology’ is a theory designed to incorporate the linear redshift versus distance relation, which is inferred from observations, into the theoretical framework independent of the global Robertson–Walker–Friedman (RWF)-type models. The motivation behind this is that the RWF cosmological models, based on the [...] Read more.
‘Small-scale cosmology’ is a theory designed to incorporate the linear redshift versus distance relation, which is inferred from observations, into the theoretical framework independent of the global Robertson–Walker–Friedman (RWF)-type models. The motivation behind this is that the RWF cosmological models, based on the assumptions of homogeneity and a constant matter density, as well as the concept of expanding space inherent to them are not applicable on the scales of observations from which the linear Hubble law is inferred. Therefore, explaining the Hubble law as the small redshift limit of the RWF model or as an effect of expanding space is inconsistent. Thus, the Hubble linear relation between the redshift of an extragalactic object and its distance should be considered an independent law of nature valid in the range of the distances where the RWF cosmology is not valid. In general, the theory, based on that concept, can be developed in different ways. In the present paper, ‘small-scale cosmology’ is formulated as a theory operating in the (redshift–object coordinates) space, which allows developing a conceptual and computational basis of the theory along the lines of that of special relativity. In such a theory, the condition of invariance of the Hubble law with respect to a change in the observer acceleration plays a central role. In pursuing this approach, the effectiveness of group theoretical methods is exploited. Applying the Lie group method yields transformations of the variables (the redshift and space coordinates of a cosmological object) between the reference frames of the accelerated observers. In this paper, the transformations are applied to studying the effects of the solar system observer acceleration on the observed shape, distribution and rotation curves of galaxy clusters. Full article
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16 pages, 3790 KB  
Technical Note
Assessment of the Improvement in Observation Precision of GNSS, SLR, VLBI, and DORIS Inputs from ITRF2014 to ITRF2020 Using TRF Stacking Methods
by Jin Zhang, Chengli Huang, Lizhen Lian and Simeng Zhang
Remote Sens. 2024, 16(7), 1240; https://doi.org/10.3390/rs16071240 - 31 Mar 2024
Cited by 2 | Viewed by 2397
Abstract
International terrestrial reference frame (ITRF) input data, generated by Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) combination centers (CCs), are considered to be relatively high-quality and accurate [...] Read more.
International terrestrial reference frame (ITRF) input data, generated by Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radiopositioning integrated by satellite (DORIS) combination centers (CCs), are considered to be relatively high-quality and accurate solutions. Every few years, these input data are submitted to the three ITRS combination centers, namely Institut Géographique National (IGN), Deutsches Geodätisches Forschungsinstitut at the Technische Universität München (DGFI-TUM), and Jet Propulsion Laboratory (JPL), to establish a multi-technique combined terrestrial reference frame (TRF). Generally, these solutions have undergone three rounds of outlier removal: the first at the technique analysis centers during solution generations and the second during the technique-specific combination by the CCs; ITRS CCs then perform a third round of outlier removal and preprocessing during the multi-technique combination of TRFs. However, since the primary objective of CCs is to release the final TRF product, they do not emphasize the publication of analytical preprocessing results, such as the outlier rejection rate. In this paper, our specific focus is on assessing the precision improvement of ITRF input data from 2014 to 2020, which includes evaluating the accuracy of coordinates, the datum accuracy, and the precision of the polar motions, for all four techniques. To achieve the above-mentioned objectives, we independently propose a TRF stacking approach to establish single technical reference frameworks, using software developed by us that is different from the ITRF generation. As a result, roughly 0.5% or less of the SLR observations are identified as outliers, while the ratio of DORIS, GNSS, and VLBI observations are below 1%, around 2%, and ranging from 1% to 1.2%, respectively. It is shown that the consistency between the SLR scale and ITRF has improved, increasing from around −5 mm in ITRF2014 datasets to approximately −1 mm in ITRF2020 datasets. The scale velocity derived from fitting the VLBI scale parameter series with all epochs in ITRF2020 datasets differs by approximately 0.21 mm/year from the velocity obtained by fitting the data up to 2013.75 because of the scale drift of VLBI around 2013. The decreasing standard deviations of the polar motion parameter (XPO, YPO) offsets between Stacking TRFs and 14C04 (20C04) indicate an improvement in the precision of polar motion observations for all four techniques. From the perspective of the weighted root mean square (WRMS) in station coordinates, since the inception of the technique, the station coordinate WRMS of DORIS decreased from 30 mm to 5 mm for X and Y components, and 25 mm to 5 mm for the Z component; SLR WRMS decreased from 20 mm to better than 10 mm (X, Y and Z); GNSS WRMS decreased from 4 mm to 1.5 mm (X and Y) and 5 mm to 2 mm (Z); while VLBI showed no significant change. Full article
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17 pages, 2176 KB  
Article
Attitude Correlated Frames Based Calibration Method for Star Sensors
by Liheng Ma, Shenglong Xiao, Wenjun Tang, Xiao Luo and Su Zhang
Sensors 2024, 24(1), 67; https://doi.org/10.3390/s24010067 - 22 Dec 2023
Cited by 3 | Viewed by 1335
Abstract
Star sensors undergo laboratory calibration before they leave the factory. In addition, recalibration is necessary after they experience vibration, deformation, etc. Using the analysis of attitude-dependent and attitude-independent interstar angular invariance calibration methods (IAICMs) as a reference, an attitude-correlated frame-based calibration method (ACFCM) [...] Read more.
Star sensors undergo laboratory calibration before they leave the factory. In addition, recalibration is necessary after they experience vibration, deformation, etc. Using the analysis of attitude-dependent and attitude-independent interstar angular invariance calibration methods (IAICMs) as a reference, an attitude-correlated frame-based calibration method (ACFCM) is proposed in this work, which combines the advantages of both methods. Using outdoor star observations, the ACFCM correlates star image frames obtained at different times via a strapdown gyro unit. As a result, the number of efficient star images for calibration increases rapidly and the distribution of star images becomes much more uniform, thus improving the calibration accuracy of the star sensor. A simulation and experimental tests were designed and carried out. Both the simulation and experimental results verify the feasibility of the proposed ACFCM method. Furthermore, by comparing our method with the IAICMs, the repeatability and reliability of the principal point obtained from the calibration with the ACFCM method proposed in this work were significantly improved. Full article
(This article belongs to the Section Optical Sensors)
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22 pages, 1506 KB  
Article
SmrtSwarm: A Novel Swarming Model for Real-World Environments
by Nikita Bhamu, Harshit Verma, Akanksha Dixit, Barbara Bollard and Smruti R. Sarangi
Drones 2023, 7(9), 573; https://doi.org/10.3390/drones7090573 - 8 Sep 2023
Cited by 6 | Viewed by 4314
Abstract
Drone swarms have gained a lot of popularity in recent times because, as a group, drones can perform highly intelligent tasks. Drone swarms are strongly inspired by the flocking behavior of birds, insects, and schools of fish, where all the members work in [...] Read more.
Drone swarms have gained a lot of popularity in recent times because, as a group, drones can perform highly intelligent tasks. Drone swarms are strongly inspired by the flocking behavior of birds, insects, and schools of fish, where all the members work in a coordinated manner to achieve a common goal. Since each drone is an independent entity, automating the control of a swarm is difficult. Previous works propose various swarming models with either centralized or distributed control. With distributed control, each drone makes its own decisions based on a small set of rules to accomplish swarm behavior, whereas in centralized control, one drone acts as the leader, who knows the final destination and the path to follow; it specifies the trajectories and velocities for the rest of the drones. Almost all the work in the area of swarming models follows Reynolds’ model, which has three basic rules. For GPS-aided settings, state-of-the-art proposals are not mature enough to handle complex environments with obstacles where primarily local decisions are taken. We propose a new set of rules and a game-theoretic method to set the values of the hyperparameters to design robust swarming algorithms for such scenarios. Similarly, the area of realistic swarming in GPS-denied environments is very sparse, and no work simultaneously handles obstacles and ensures that the drones stay in a confined zone and move along with the swarm. Our proposed solution SmrtSwarm solves all of these problems. It is the first comprehensive model that enables swarming in all kinds of decentralized environments regardless of GPS signal availability and obstacles. We achieve this by using a stereo camera and a novel algorithm that quickly identifies drones in depth maps and infers their velocities and identities with reference to itself. We implement our algorithms on the Unity gaming engine and study them using exhaustive simulations. We simulate 15-node swarms and observe cohesive swarming behavior without seeing any collisions or drones drifting apart. We also implement our algorithms on a Beaglebone Black board and show that even in a GPS-denied setting, we can sustain a frame rate of 75 FPS, much more than what is required in practical settings. Full article
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14 pages, 3178 KB  
Article
Aeroacoustic and Aerodynamic Adjoint-Based Shape Optimization of an Axisymmetric Aero-Engine Intake
by Morteza Monfaredi, Varvara Asouti, Xenofon Trompoukis, Konstantinos Tsiakas and Kyriakos Giannakoglou
Aerospace 2023, 10(9), 743; https://doi.org/10.3390/aerospace10090743 - 22 Aug 2023
Cited by 1 | Viewed by 2748
Abstract
A continuous adjoint-based aeroacoustic optimization, based on a hybrid model including the Ffowcs Williams–Hawkings (FW–H) acoustic analogy, to account for the multidisciplinary design of aero-engine intakes with an axisymmetric geometry, is presented. To optimize such an intake, the generatrix of its lips is [...] Read more.
A continuous adjoint-based aeroacoustic optimization, based on a hybrid model including the Ffowcs Williams–Hawkings (FW–H) acoustic analogy, to account for the multidisciplinary design of aero-engine intakes with an axisymmetric geometry, is presented. To optimize such an intake, the generatrix of its lips is parameterized using B-Splines, and the energy contained in the sound pressure spectrum, at the blade passing frequency at receivers located axisymmetrically around the axis of the engine, is minimized. The engine is not included in the optimization and manifests its presence through an independently computed time-series of static pressure over the annular boundary of the simulation domain that corresponds to the inlet to the fan. Taking advantage of the case axisymmetry, the steady 3D RANS equations are solved in the rotating frame of reference and post-processed to compute the flow quantities’ time-series required by the FW–H analogy. The numerical solution of the unsteady flow equations and the otherwise excessive overall cost of the optimization are, thus, avoided. The objective function gradient is computed using the continuous adjoint method, coupled with the analytical differentiation of the FW–H analogy. The adjoint equations are also solved in the rotating frame via steady solver. Full article
(This article belongs to the Special Issue Adjoint Method for Aerodynamic Design and Other Applications in CFD)
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