Passive Tracking Research Articles

Radical right populism and the media: evidence from the supply side and demand side of political information in Germany

Abstract Hostile stances towards journalists and perceptions of media bias have become cornerstones of populist radical right identity formation. Despite a lively scholarly and public debate about the relation between populism and the media, a comprehensive account of the supply side of political information—radical right populist parties’ (RRPPs) communication—and the demand side—citizens’ information selection—is still missing. Focusing on the RRPP Alternative for Germany (AfD), this paper first establishes that its Twitter communication features more negative media-related cues and links to hyperpartisan news websites compared with the other major German parties. Self-reported media use from two high-quality surveys as well as a passive web tracking allow us to comprehensively characterize the information selection of AfD supporters. In line with the party’s media-related cues, people identifying with the AfD used alternative online sources more frequently amid less exposure to public broadcasting than supporters of other parties. Beyond Germany, media-related party cues and selective exposure by citizens might play an even more critical role in more polarized societies. More generally, the identified individual-level heterogeneity in media exposure is a scope condition that research on the aggregated societal effects of media coverage, e.g. on immigration, needs to consider.

ML-Track: Passive Human Tracking Using WiFi Multi-link Round-trip CSI and Particle Filter

ML-Track: Passive Human Tracking Using WiFi Multi-link Round-trip CSI and Particle Filter

Review of Research Progress on Passive Direction-of-Arrival Tracking Technology for Underwater Targets

Utilization of ocean resources and defense of national security heavily rely on underwater target tracking technology, which consequently holds significant strategic importance. The passive tracking technology for underwater target bearings, known for its extensive detection range, capability for long-term observation, and robust real-time capabilities, has emerged as a new focal point of research. This paper reviews the essential concepts, research developments, applications, and limitations of key technologies for passive underwater target bearing tracking, concentrating on three main areas: underwater target bearing estimation technology, target tracking technology, and comprehensive underwater target bearing tracking technology. Specifically, it discusses highly robust methods for tracking single or multiple underwater targets. Ultimately, this paper highlights the primary challenges currently facing research in this field and provides a perspective on future developments.

ON THE ISSUE OF RADON EXPOSURE IN THE EXISTING RADIATION SITUATION AT WORKPLACES.

assessment of probable exposure levels from radon and NORM in workplaces within the context of justi fying radiation protection plans in an existing exposure situation. Materials regarding the assessment of naturally occurring radioactive material (NORM) con tent in tailing from mining and processing industries in Ukraine and assessments of contamination levels of industri al sites of oil and gas enterprises were used for estimating the probable range of effective doses (ED) of workers fromNORM at industrial enterprises. These materials were obtained as a result of research conducted by specialists from theRadiation Protection Laboratory of the State Institution «O.M. Marzіeiev Institute for Public Health of the NationalAcademy of Medical Sciences of Ukraine» (RP SI «IPH NAMSU»). The results of studies conducted by the StateInstitution «Ukrainian Scientific Research Institute of Industrial Medicine» (SI «UKRMEDPROM») were used for calcu lating the EDs of iron ore miners. Calculations of probable EDs of industrial enterprise workers were carried out usingmethodologies and recommendations from publications of the IAEA related to occupational exposure. Assessments ofexposure levels for office workers were based on measurements of indoor radon concentrations of first-floor premisesin multi-story buildings of industrial urban development from the laboratory's own databases. Radon measurements inindoor air were conducted using passive track etch radon detectors with an exposure time of at least 30 days.Calculations of EDs for office workers were carried out using dose coefficients and mathematical models from the ICRP. When workers are exposed to radon as a result of the technological process, radiation exposure is limitedby dose criteria. Using non-uranium miners as an example, it was shown that effective doses (ED) due to gammaradiation varied within a narrow range, ranging from 0.2 to 0.4 mSv/year, and were on average an order of magnitudelower than the radon component of the total ED for the two groups of mines, which amounted to 2.0-14.0 mSv/yearfor the Northern group and 0.3-0.8 mSv/year for the Southern group. For three underground worker specialties, radi ation EDs could potentially exceed the reference level of 6 mSv/year and fall under regulatory control. Potentialradiation EDs for workers at one of the Ukrainian oil fields were generally not significant (<0.1-1 mSv/year), exceptfor areas where used pipe storage and sludge settlers were located (70.0 mSv/year; 28.0 mSv/year at a distance of10 meters), near which dose limits for Category A personnel (6 mSv/year), falling under regulatory control, wereexceeded. Radon exposure in workplaces also includes the presence of workers in regular office premises on the firstfloors of multi-story buildings, where the main source of radon entry into the air is the underlying soil. For the mostresearched regions of Ukraine (~1200 measurements of radon activity concentrations in first-floor premises), it wasfound that the reference level of 300 Bq/m3 is exceeded in 0.2-0.5% of cases in certain regions, indicating thatpotentially the reference level may be exceeded in tens of thousands of premises. A differentiated approach is justified for assessing the hazards of workplaces, allowing for optimizingradiation protection for workers at a reasonable cost and saving significant resources for enterprises. Effective doses(ED) of radiation for workers at enterprises where radon is an integral part of the technological process vary widelyand can differ by an order of magnitude even within the same enterprise. Reference levels of 300 Bq/m3 may beexceeded in tens of thousands of office premises, and only through direct measurements of radon activity concen trations in building air can such premises be identified.

MagDesk: Interactive Tabletop Workspace Based on Passive Magnetic Tracking

MagDesk: Interactive Tabletop Workspace Based on Passive Magnetic Tracking

Passive vision based three-dimensional seam tracking using a stereo vision system with a single HDR camera

Seam tracking is a crucial feature that an automatic welding system must have. The laser tracking algorithm offers high accuracy but faces challenges in identifying seams with extremely narrow gaps, as the deformation of the laser stripe becomes difficult to detect in such cases. In contrast, the passive vision-based algorithm can effectively capture narrow gap information from the welding scene, making it more suitable for recognizing narrow seams. However, most of proposed passive vision-based seam tracking is based on “teaching and playback” mode and can only realize planar tracking. In medium and thick steel plate welding, the workpieces are so large that the “teaching and playback” based control algorithm is unsuitable. Therefore, in this paper, a stereo vision system with a single camera and the corresponding calibration algorithm are developed to achieve three dimensional seam tracking. Compared to stereo system with dual camera, the proposed system is cheaper and easier to synchronize acquisition. Moreover, to get out of the “teaching and playback” control strategy, a vector control algorithm without cumulative error is proposed. Results of nine experiments show that the average error of the proposed seam tracking system is less than 1.0662mm and the maximum error is 1.8030mm.

Target detection, ISAR imaging and tracking capabilities of a passive radar net utilising barrage jamming signals

AbstractJammers aim to interfere with active radars during military operations. Still, they can strengthen our capabilities on the battlefield if there are proper methods to use them. This paper demonstrates the possibility of utilising a ground‐based barrage jammer (to jam radars or communications) as an illumination source for passive radar detection, tracking and inverse synthetic aperture radar (ISAR) imaging. It shows the feasibility of using a jammer for cooperative (friendly jammer) and non‐cooperative (hostile jammer) operations. The results come from the European Defence Agency project no B 1516 IAP2 GP entitled jammer‐based passive radar. This article will present some of the outcomes of field trials conducted in June 2022 in Poland within the international electronic warfare exercises. Designed jammer demonstrators, with a maximum bandwidth of 115 MHz, were used as illuminators of opportunity and made it possible to test the operation of passive radars with five signal types (within two bands—L‐band and S‐band) for military targets (i.e. fighters, transport planes, helicopters). In the first part of the article, detection, ISAR imaging and tracking issues will be addressed. The second part of the article will focus on the results obtained during the project's joint field trials.

Holographic solar concentrator with wide band using multi-wavelength transmission grating

A multi-wavelength holographic grating using photopolymer is presented for a holographic solar concentrator system. Currently, volume holographic optical elements (HOEs) have been proposed for application in solar concentrators due to their advantages, such as lightweight, selective wavelength, and passive tracking. However, their efficiency depends on the central wavelength, which is determined by both the recording material and the recording angle. In this work, a transmission holographic grating with multiple wavelengths is proposed to enhance the performance of holographic solar concentrator systems. The diffraction efficiency and spectral range are significant factors in determining the concentrated efficiency of solar energy. The optimal efficiency of transmission grating is derived based on the optical characteristics of the photopolymer and the wavelength selectivity is then analyzed to compare the concentrated efficiency. The experimental results indicate that the dichromatic transmission grating with an average diffraction efficiency of 70 % and a wavelength band of 278 nm has a concentrated efficiency of 48.7 %. Compared to monochromatic and trichromatic holographic grating, dichromatic grating can concentrate more energy with a wider spectral band.

Prediction of mental health risk in adolescents via a smartphone app: a feasibility pilot study

Abstract Background The prevalence of mental health problems in adolescents is a global public health concern. Machine learning (ML) can analyse multidimensional data collected by phone sensors (passive tracking) and symptom self-reporting (active tracking) to model and predict mental health states. However, research in adolescents is lacking. This study investigated the feasibility of using ML to predict mental health in a non-clinical population of adolescents from active and passive data collected through the Mindcraft mobile app. Methods We recruited 103 secondary students (aged 14-18) who first completed the Strengths and Difficulties Questionnaire (SDQ) and then used the Mindcraft app for two weeks. The app integrates sensor data (location, steps, noise, light, battery, app usage) and self-reports. We extracted 85 sensor-based features and 19 from questionnaires to develop a gradient-boosted ensemble ML model. This model identifies students with abnormal SDQ scores and was evaluated using leave-one-out cross-validation. Results All students completed the active questionnaires; 67 also provided passive sensor data. 31 had abnormal SDQ scores. Using passive data, the ML model reached a balanced accuracy of 0.64 and an AUC score of 0.57. Incorporating both data types improved accuracy to 0.67 and AUC to 0.70. Feature importance scores showed step count and questionnaire on racing thoughts and hopefulness as most significant. Conclusions Our findings affirm the potential of integrating passive and active data collection to monitor mental health in real-world settings. Our ML model demonstrated moderate accuracy in predicting adolescents’ mental health risk measured with a behavioural screening questionnaire. This study will guide the development of a ML-driven, personalised mobile intervention for early symptom detection and mental health self-management, which might constitute an innovative and scalable tool for mental health prevention and intervention in adolescents. Key messages • This study shows the feasibility of using active and passive data to predict mental health risk in adolescents. • This study informs the development of a personalised machine learning-driven mobile intervention.

Passive Stylus Tracking: A Systematic Literature Review

Passive stylus systems offer a simple and cost-effective solution for digital input, compatible with a wide range of surfaces and devices. This study reviews the domain of passive stylus tracking on passive surfaces, a topic previously underexplored in existing literature. We answer four key research questions: what type of systems exist in this domain, what methods do they use for tracking styli, how accurate are they, and what are their limitations? A systematic literature review resulted in 24 papers describing passive stylus systems. Their methods primarily fall into four categories: monocular cameras with image processing, multiple camera systems with image processing, machine learning systems using high-speed cameras or motion capture hardware, and radio frequency signal-based systems with signal processing. We found the system with the highest accuracy used a single monocular camera. In many systems, markers such as retroreflective spheres, tape, or fiducial markers were used to enhance the feature matching. We have also found stagnation and in some cases, regression in the precision and reliability of these systems over time. The limitations in these systems include the lack of varied stylus form factor support, the restriction to specific camera positions and angles, and the requirement of expensive hardware. Given these findings, we discuss the important characteristics and features of passive stylus systems and propose ways forward in this field.

Experimental and statistical methods for microrheological characterization of heterogeneity in human respiratory mucus mimics of health and disease progression

Human respiratory mucus (HRM) is extremely soft, compelling passive microrheology for linear viscoelastic characterization. We focus this study on the use of passive microrheology to characterize HRM heterogeneity, a phenomenon in normal HRM that becomes extreme during cystic fibrosis (CF) disease. Specifically, a fraction of the mucin polymers comprising HRM phase-separate into insoluble structures, called flakes, dispersed in mucin-depleted solution. We first reconstitute HRM samples to the MUC5B:MUC5AC mucin ratios consistent with normal and CF clinical samples, which we show recapitulate progressive flake formation and heterogeneity. We then employ passive particle tracking with 200 nm and 1 μm diameter beads in each reconstituted sample. To robustly analyze the tracking data, we introduce statistical denoising methods for low signal-to-noise tracking data within flakes, tested and verified using model-generated synthetic data. These statistical methods provide a fractional Brownian motion classifier of all successfully denoised, tracked beads in flakes and the dilute solution. From the ensemble of classifier data, per bead diameter and mucus sample, we then employ clustering methods to learn and infer multiple levels of heterogeneity: (i) tracked bead data within vs. outside flakes and (ii) within-flake data buried within or distinguishable from the experimental noise floor. Simulated data consistent with experimental data (within and outside flakes) are used to explore form(s) of the generalized Stokes–Einstein relation (GSER) that recover the dynamic moduli of homogeneous and heterogeneous truth sets of purely flakelike, dilute solution, and mixture samples. The appropriate form of GSER is applied to experimental data to show (i) flakes are heterogeneous with gel and sol domains; (ii) dilute solutions are heterogeneous with only sol domains; and (iii) flake and dilute solution properties vary with probe diameter.

Multi-sensor distributed fusion based on cross-location for passive tracking

Multi-sensor distributed fusion based on cross-location for passive tracking

Fast, automated, real-time 3D passive balloon catheter tracking during MRI-guided cardiac catheterization using orthogonal projection imaging and real-time image-based catheter detection.

MRI-guidance of cardiac catheterization is currently performed using one or multiple 2D imaging planes, which may be suboptimal for catheter navigation, especially in patients with complex anatomies. The purpose of the work was to develop a robust real-time 3D catheter tracking method and 3D visualization strategy for improved MRI-guidance of cardiac catheterization procedures. A fast 3D tracking technique was developed using continuous acquisition of two orthogonal 2D-projection images. Each projection corresponds to a gradient echo stack of slices with only the central k-space lines being collected for each slice. To enhance catheter contrast, a saturation pulse is added ahead of the projection pair. An offline image processing algorithm was developed to identify the 2D coordinates of the balloon in each projection image and to estimate its corresponding 3D coordinates. Post-processing includes background signal suppression using an atlas of background 2D-projection images. 3D visualization of the catheter and anatomy is proposed using three live sagittal, coronal, and axial (MPR) views and 3D rendering. The technique was tested in a subset of a catheterization step in three patients undergoing MRI-guided cardiac catheterization using a passive balloon catheter. The extraction of the catheter balloon 3D coordinates was successful in all patients and for the majority of time-points (accuracy >96%). This tracking method enabled a novel 3D visualization strategy for passive balloon catheter, providing enhanced anatomical context during catheter navigation. The proposed tracking strategy shows promise for robust tracking of passive balloon catheter and may enable enhanced visualization during MRI-guided cardiac catheterization.

Long-term comparison and performance study of consumer grade electronic radon integrating monitors

This study reports the performance of 7 types of consumer grade passive Electronic Radon Integrating Monitors, ERIM (AlphaE, AER Plus, Canary, Corentium Pro, Radon Scout Home, Ramon and Wave) and passive etched track radon detectors. All monitors and passive radon detectors were exposed side by side for 2 periods of 3 months under controlled conditions in the UKHSA radon chamber and in a stainless steel container to an average radon concentration of 4781 Bq m−3 and 166 Bq m−3, respectively. The performance of each individual monitor was compared with Atmos 12DPX and AlphaGUARD P30 reference instruments. The performance of the monitors was evaluated by estimating the biased, precision and measurement errors of each type. It was found that UKHSA passive radon detectors showed excellent performance (measurement error < 10%) at both higher and lower exposures. The AlphaE, Canary and Ramon showed excellent performance, with measurement error <10%, when they were exposed to radon concentrations between 4000 Bq m−3 and 6000 Bq m−3 in the UKHSA radon chamber. However, when the monitors were exposed to radon levels below the UK radon Action Level of 200 Bq m−3, the only ERIM which had a measurement error <10% was the Radon Scout Home. All other monitors showed a significant decrease in their performance with measurement errors ranging between 20% and 50%. The calibration factor, which is the ratio between the measured value (background is subtracted) and the reference value, was also studied. It was found that the calibration factors of individual monitors changed significantly. Calibration measurements in 2019 and in 2023 found that the percentage change varied between −46% and +63%. This shows the importance of initial and regular calibration, and maintenance of the monitors.

WiVelo: Fine-grained Wi-Fi Walking Velocity Estimation

Passive human tracking using Wi-Fi has been researched broadly in the past decade. Besides straightforward anchor point localization, velocity is another vital sign adopted by the existing approaches to infer user trajectory. However, state-of-the-art Wi-Fi velocity estimation relies on Doppler-Frequency-Shift (DFS), which suffers from the inevitable signal noise incurring unbounded velocity errors, further degrading the tracking accuracy. In this article, we present WiVelo, which explores new spatial-temporal signal correlation features observed from different antennas to achieve accurate velocity estimation. First, we use subcarrier shift distribution (SSD) extracted from channel state information (CSI) to define two correlation features for direction and speed estimation, separately. Then, we design a mesh model calculated by the antennas’ locations to enable a fine-grained velocity estimation with bounded direction error. Finally, with the continuously estimated velocity, we develop an end-to-end trajectory recovery algorithm to mitigate velocity outliers with the property of walking velocity continuity. We implement WiVelo on commodity Wi-Fi hardware and extensively evaluate its tracking accuracy in various environments. The experimental results show our median and 90-percentile tracking errors are 0.47 m and 1.06 m, which are half and a quarter of state-of-the-art. The datasets and source codes are published through Github ( https://github.com/research-source/code ).

Original Insights Into Rock Slope Damage Processes Until Collapse From Passive Seismic Monitoring

AbstractWe performed a passive seismic monitoring of the La Praz ∼14,000 m3 unstable slope (French Alps) spanning over 10 years. During the last 6 months prior to collapse, we detected a clear 24% decrease in the slope's fundamental resonance frequency, f0, caused by a reduction in overall rock mass stiffness. The combined study of f0 and slope deformation suggested the alternating importance of sudden brittle failure processes versus more ductile phases with possible sliding. Seismic monitoring revealed slope damage that remained ambiguous or undetected with ground surface deformation monitoring, and highlighted critical periods with intense damage. Only some of these critical damage periods could be related to clear external forcing factors such as intense rainfall episodes. These new insights into rock slope's structural condition at depth represent an asset for future monitoring systems. Surface deformation and passive seismic stiffness tracking combined could reveal active slopes with ongoing damage processes.

Passive underwater tracking with unknown measurement noise statistics using variational Bayesian approximation

This paper considers a bearings-only tracking problem with unknown measurement noise statistics. It is assumed that the measurement noise follows a Gaussian probability density function where the mean and the covariance of the noise are unknown. Here, an adaptive nonlinear filtering technique is proposed, where the joint distribution of the measurement noise mean and its covariance are considered to follow a normal inverse Wishart (NIW) distribution. Using the variational Bayesian (VB) approximation, joint distribution of the target state, the measurement noise mean and covariance is factorized as the product of their individual probability density function (pdf). Minimizing the Kullback-Leibler divergence (KLD) between the factorized and true joint pdfs, probability distributions of the noise mean, covariance and the target states are evaluated. The estimation of states with the proposed VB based method is compared with the maximum a posteriori (MAP) and the maximum likelihood estimation (MLE) based adaptive filtering. Deterministic sigma points are used to realize the filtering algorithms. The proposed adaptive filter with VB approximation is found to be more accurate compared to their corresponding MAP-MLE based counterparts.

Early Pandemic Behaviors and the Role of Vaccines in Reversing Pandemic Mobility Trends: Evidence from a U.S. Panel

The COVID-19 pandemic disrupted travel behavior and resulted in the emergence of new mobility trends. In this paper, we study the degree to which vaccines played a role in reversing pandemic-induced travel behaviors and contributed to a “return to normal.” Using five waves of original U.S.-based survey data combined with passive smartphone tracking data collected in 2020 and 2021, we show that in the early phases of the pandemic, the behavioral response of people in the United States was heterogeneous: individuals with low levels of concern about being infected with COVID-19 engaged in riskier behaviors than those with higher levels of concern, such as traveling more, eschewing masks, attending large gatherings, and using public transportation. Vaccine availability in early 2021 played a significant role in reducing those concerns, which in turn was reflected in significantly increased mobility and travel frequency. We also found a strong positive association between getting vaccinated and the frequency of using public transportation. Telecommuting and working from home remained high after vaccine availability, but we found that the fraction of full-time employees that worked from home every day significantly dropped. This reduction in fully remote work was no different among vaccinated and unvaccinated people, which suggests that the decision to return to in-person work was not only driven by employees’ safety concerns and preferences, but was also a function of employers’ expectations and their decision to reopen their offices. We discuss the implications of our findings on understanding travel behavior during pandemic impact- and recovery periods.

A novel process to infer the reliability of ecological information derived from passive acoustic telemetry track reconstruction

Abstract Passive acoustic telemetry can be used within cooperative networks to track migratory species over great distances at a relatively low cost. However, the non‐uniform distribution of fixed receivers within networks often results in sporadic detection data. Here, we propose a novel combination of methods to measure the reliability of hot spot analysis results derived from track reconstructions of passive telemetry data. We use an iterative process to simulate tracks of animals, derive detection data from these tracks, and reconstruct tracks from these derived data using a movement model. We then compare quadrat count residuals from the simulated and reconstructed tracks for different grid resolutions. The methodological framework is outlined in detail and tested on the acoustic telemetry cooperative arrays off the US East Coast. Our methods are applied to a subset of blacktip shark, Carcharhinus limbatus, acoustic telemetry detection data collected off the US East Coast. We then apply the resultant quadrat count to a hot spot analysis to determine the distribution of animals derived from these track reconstruction methods. We integrate the results of our methods process with the hot spot analysis results to determine the reliability of this distribution information. The track reconstruction methods performed well in coastal regions, from Palm Beach County, FL to Long Island, NY, minimized the clustering effect of high densities of receivers, and closed the gaps in some regions that were lacking receiver coverage. This performance was primarily affected by the presence/absence of receivers, and to a lesser extent by receiver density and water depth, depending on the grid resolution. Our method combination demonstrates a means by which passive telemetry data can be regularized to determine the spatial distribution of animals across regions with non‐uniform sampling coverage. These methods also allow the user to determine the reliability of animal distribution products in a telemetry array and the factors that contribute to high accuracy and precision. Our iterative process enables managers to infer the reliability of ecological results in decision‐making processes and could be leveraged for use as a gap analysis to develop a national strategy for telemetry assets.

Adaptive neural fault-tolerant prescribed performance control of a rehabilitation exoskeleton for lower limb passive training

This article studies the passive tracking problem of a wearable exoskeleton for lower limb rehabilitation therapy in the face of unmodeled dynamics, interactive friction, disturbance, prescribed performance constraints, and actuator faults. Adaptive neural networks and a smooth performance function are incorporated to establish a novel fault-tolerant tracking scheme, which can not only compensate for the nonlinear uncertainties and disturbance, but also handle the actuator fault with guaranteed tracking performance. A state feedback controller is presented by using the full state information and an output feedback controller is developed when the angular velocity is unavailable. The differential explosion issue of the backstepping technique is resolved by constructing a first-order filter and the unmeasurable velocity is estimated by a nonlinear observer. Semiglobal uniform boundedness stabilities of the exoskeleton system are proved via the Lyapunov direct method. The tracking performances of the designed control approaches are tested by comparative simulations.