Position Measurements Research Articles

Self-powered ultraviolet position-sensitive detectors based on PrNiO3/Nb-doped SrTiO3 p–n junctions

Position-sensitive detectors based on the lateral photovoltaic effect have been widely used in optical engineering for the measurement of position, distance, and angles. However, self-powered ultraviolet position-sensitive detectors with high sensitivity and fast response are still lacking due to the difficulty associated with the fabrication of p-type wide bandgap semiconductors, which hinders their further design and enhancement. Here, the influence of band structures and interfacial transport properties on the performance of self-powered ultraviolet position-sensitive detectors based on PrNiO3/Nb:SrTiO3p–n junctions is systematically investigated. Large position sensitivity and fast relaxation time of the lateral photovoltaic effect were observed up to 400 K in the perovskite-based ultraviolet position-sensitive detectors. Hall effect measurements revealed that the transport of photoexcited carriers occurs mainly through the interface of the PrNiO3/Nb:SrTiO3 junctions, resulting in a fast response and a stable photovoltaic effect. This study presents insights and avenues for designing self-powered perovskite oxide ultraviolet position-sensitive detectors with enhanced photoelectric performance.

New Orbital Parameters of 850 Wide Visual Binary Stars and Their Statistical Properties

Abstract Based on positional observations and measurements of radial velocities, the orbits of 850 wide visual binary stars have been determined. The parameters of the log-normal distributions for the histograms of orbital periods, stellar masses, and semimajor axes in astronomical units have been obtained. The eccentricity histogram for binary stars with orbital periods less than 400 yr follows a normal distribution centered at e = 0.545 +/− 0.029. For stars with longer periods, this distribution obeys the law f = 2e, with accuracy to errors. The mass-to-luminosity relation for stars with well-determined masses is given by: log L ⊙ = 4.33 log M ⊙ − 0.11 , where L ⊙ and M ⊙ are the luminosity and mass of the star in units of the solar luminosity and mass, respectively.

A linear variable differential transducer for position measurement with an external armature

This paper presents a novel structure for linear position sensors with external armature. The coils are designed to have a nonoverlapping structure to increase the coils’ design optimization flexibility. The 3D finite element method is utilized for design optimization to extend the linearity range of the position sensor. The excitation and pickup coils are segmented to facilitate and improve the winding process. The number of turns in each pickup coil is optimized using the 3D finite element method to minimize the nonlinearity error and enhance the linearity range of the position sensor. The simulation results are compared with experiments to validate the optimization process of the position sensor.

VECTOR: Velocity-Enhanced GRU Neural Network for Real-Time 3D UAV Trajectory Prediction

This paper addresses the challenge of predicting 3D trajectories for Unmanned Aerial Vehicles (UAVs) in real-time, a critical task for applications like aerial surveillance and defense. Current prediction models primarily leverage only position data, which may not provide the most accurate forecasts for UAV movements and usually fail outside the position domain used in the training phase. Our research identifies a gap in utilizing velocity estimates and first-order dynamics to better capture the dynamics and enhance prediction accuracy and generalizability in any position domain. To bridge this gap, we introduce a trajectory prediction scheme using sequence-based neural networks with Gated Recurrent Units (GRUs) to forecast future velocity and positions based on historical velocity estimates instead of position measurements. This approach is designed to improve the predictive capabilities over traditional methods that rely solely on recurrent neural networks (RNNs) or transformers, which can struggle with scalability in this context. Our methodology employs both synthetic and real-world 3D UAV trajectory data, incorporating diverse patterns of agility, curvature, and speed. Synthetic data are generated using the Gazebo robotics simulator and PX4 Autopilot, while real-world data are sourced from the UZH-FPV and Mid-Air drone racing datasets. We train the GRU-based models on drone 3D position and velocity samples to capture the dynamics of UAV movements effectively. Quantitatively, the proposed GRU-based prediction algorithm demonstrates superior performance, achieving a mean square error (MSE) ranging from 2×10−8 to 2×10−7. This performance outstrips existing state-of-the-art RNN models. Overall, our findings confirm the effectiveness of incorporating velocity data in improving the accuracy of UAV trajectory predictions across both synthetic and real-world scenarios, in and out of position data distributions. Finally, we open-source our 5000 trajectories dataset and a ROS2 package to facilitate the integration with existing ROS-based UAV systems.

Comparative Analysis of Physiological Vergence Angle Calculations from Objective Measurements of Gaze Position.

Eccentric photorefractometry is widely used to measure eye refraction, accommodation, gaze position, and pupil size. While the individual calibration of refraction and accommodation data has been extensively studied, gaze measurements have received less attention. PowerRef 3 does not incorporate individual calibration for gaze measurements, resulting in a divergent offset between the measured and expected gaze positions. To address this, we proposed two methods to calculate the physiological vergence angle based on the visual vergence data obtained from PowerRef 3. Twenty-three participants aged 25 ± 4 years viewed Maltese cross stimuli at distances of 25, 30, 50, 70, and 600 cm. The expected vergence angles were calculated considering the individual interpupillary distance at far. Our results demonstrate that the PowerRef 3 gaze data deviated from the expected vergence angles by 9.64 ± 2.73° at 25 cm and 9.25 ± 3.52° at 6 m. The kappa angle calibration method reduced the discrepancy to 3.93 ± 1.19° at 25 cm and 3.70 ± 0.36° at 600 cm, whereas the linear regression method further improved the accuracy to 3.30 ± 0.86° at 25 cm and 0.26 ± 0.01° at 600 cm. Both methods improved the gaze results, with the linear regression calibration method showing greater overall accuracy.

Astrometric Calibration of MagAO-X with Updated Solutions for HD 165054 Field Stars

Abstract MagAO-X is a recently commissioned extreme adaptive optics instrument for the Magellan Clay 6.5 m telescope at Las Campanas Observatory in Chile. MagAO-X had first light in 2019 and subsequent commissioning observations in 2022 and 2023. An essential step for the commissioning of any new instrument is the calibration of the conversion of detector coordinates to angular sky coordinates, which we accomplish with observations of HD 165054. The background stars adjacent to HD 165054 in Baade’s Window are in a fortuitous configuration for the astrometric calibration of natural-guide-star high-contrast imaging instruments. We extend past work to connect these stars’ positions to absolute astrometry for HD 165054 itself using Gaia Data Release 3 data, and bootstrap the creation of an astrometric solution for our new high-contrast imaging instrument. Through Markov Chain Monte Carlo analysis of the historical data and position measurements from MagAO-X, we obtain updated astrometric parameters for the seven background stars and an astrometric calibration of the MagAO-X science cameras.

Detailed Transfer Line Beam Characteristics at an Operational Proton Therapy Center

The McLaren Proton Therapy Center functions as a multi-room, clinically active cancer treatment center. Beam position, size, and current measurements along the transfer lines have been utilized together with simulations to validate computer models for the Center’s transfer lines and associated beam parameters. Beam profile monitor (BPM) data collected along the beamlines provided detailed beam measurements. A computer tool, utilizing nonlinear constrained optimization programs that are integrated with a beam envelope code, was used to find detailed beam phase space parameters (centroids, sigma matrices) that reproduced the measured data. Quadrupole scan and steerer scan experiments have been used to validate the calibration and alignment of these devices, as well as to independently confirm beam parameters at selected locations. Beam current measurements along the beamlines were used to infer transmission efficiencies and then compared to multi-particle simulations in order to identify beam loss locations. The work resulted in an improved understanding of the beams and beam transfer lines to support further beamline optimization and design activities. The experimental and simulation methodologies, tools, and results and their interpretations should be applicable to many types of operating accelerator facilities.

A Low-Cost Three-Degree-of-Freedom Position Measurement Method of the Y-Type Maglev Planar Motor Based on Hall Sensor

A Low-Cost Three-Degree-of-Freedom Position Measurement Method of the Y-Type Maglev Planar Motor Based on Hall Sensor

Trajectory PHD and CPHD Filters for the Pulse Doppler Radar

Different from the standard probability hypothesis density (PHD) and cardinality probability hypothesis density (CPHD) filters, the trajectory PHD (TPHD) and trajectory CPHD (TCPHD) filters employ the sets of trajectories rather than the sets of the targets as the variables for multi-target filtering. The TPHD and TCPHD filters exploit the inherent potential of the standard PHD and CPHD filters to generate the target trajectory estimates from first principles. In this paper, we develop the TPHD and TCPHD filters for pulse Doppler radars (PD-TPHD and PD-TCPHD filters) to improve the multi-target tracking performance in the scenario with clutter. The Doppler radar can obtain the Doppler measurements of targets in addition to the position measurements of targets, and both measurements are integrated into the recursive filtering of PD-TPHD and PD-TCPHD. PD-TPHD and PD-TCPHD can propagate the best augmented Poisson and independent identically distributed multi-trajectory density approximation, respectively, through the Kullback–Leibler divergence minimization operation. Considering the low computational complexity of sequential filtering, Doppler measurements are sequentially applied to the Gaussian mixture implementation. Moreover, we perform the -scan implementations of PD-TPHD and PD-TCPHD. Simulation results demonstrate the effectiveness and robustness of the proposed algorithms in the scenario with clutter.

Evaluation of hyoid bone position, shape, area, volume, and tongue volume.

Our study aims to determine the position and types of the hyoid bone and to evaluate the morphometry of the hyoid bone and tongue according to sex. Our study included cervical Computed Tomography (CT) images of 200 individuals (100 females, 100 males) between the ages of 18 and 84. Using the 3D Slicer software package, hyoid bone position, shape, area, volume and tongue volume measurements were made on these images. In our study, the position of the hyoid bone was found to be proportionally at the C3 vertebral level in both sexes. The most common hyoid bone was type B, while the least common was type V. Type B rate was statistically higher in females, and type H rate was higher in males (p < 0.05). Participants with type H had statistically higher bone volumes and areas than those with type B (p < 0.05). Differences between bone volumes and areas of other bone types were not statistically significant (p > 0.05). Average hyoid bone volume (females 1575.9mm3; males 2609.6mm3), hyoid bone area (females 1519.8mm2; males 2406.4mm2), tongue volume (females 66,659.5mm3; males 83,085.5mm3) were measured in females and males. A statistically weak negative correlation was found between the participants' ages and hyoid bone areas (rho = -0.162; p = 0.022). A statistically moderate positive correlation was found between tongue volume and hyoid bone volume/area (respectively p < 0.001; rho1 = 0.658, rho2 = 0.546). Hyoid bone volume, hyoid bone area and tongue volume were higher in males than females. As tongue volume increased, hyoid bone volume and hyoid bone area increased. The connection between tongue volume and hyoid bone volume will contribute to dentomaxillary development and surgical procedures, and bone morphology will also be important in different disciplines.

Dynamics and related hazards of the Belvedere Glacier in the Italian Alps: a review

The Belvedere glacier is an intensively studied glacier in the Italian Alps on the east face of the Monte Rosa, which is currently undergoing a fast deglaciation connected to various slope failures and Glacial Lake Outburst Floods. Measurements of the terminus position have been carried out since the 1920s. Since 2000, more attention has been paid to this area due to the occurrence of large mass movements and a surge-type event. In this review, research articles and various reports dealing mainly with glacier dynamics, rock and ice avalanches, Glacial Lake Outburst Floods, and other hazardous processes were considered. Aerial photogrammetry, Unmanned Aerial Vehicles, satellite stereo-processing and several terrestrial approaches (laser scanning, geophysics, measurements of near-surface heat flow, ablation stakes and camera-lapse) provided a base for quantifying the ongoing processes. Despite efforts based on the comparison of Digital Elevation Models, this review shows that the evolution of the Belvedere glacier in terms of ice volume is still partially unknown due to the low temporal frequency of aerial surveys, technical limitations of the Unmanned Aerial Vehicles used, and the fact that most studies focus only on the lower part of the glacier. The hazardous supraglacial Effimero lake that appeared during the surge-type event has been well documented, and interventions to mitigate potential risks were put in place, but the trigger of the event and the evolution of the lake basin have not yet been clarified. Mass wasting and outburst floods are mainly documented in the grey literature. The degradation of permafrost was suggested to be the driver of rock and ice avalanches, including one of the largest ice avalanches in the Alps, which occurred in 2005. In summary, the Belvedere Glacier and the surrounding rock walls have experienced repeated slope failures, an incident of surge and several outburst floods. Despite regular monitoring, a clear picture of its behavior due to the changing climate is still unknown. This review is intended to pave the way for further integrative studies.

Spontaneous cerebrospinal fluid rhinorrhea as a primary presentation of idiopathic intracranial hypertension, management strategies, and clinical outcome.

Causes of cerebrospinal fluid (CSF) rhinorrhea could be divided into primary (spontaneous) and secondary (head trauma and iatrogenic). Idiopathic intracranial hypertension (IIH) has emerged as a cause for spontaneous CSF rhinorrhea but is still underestimated, may be overlooked and needs special consideration in management. The objective of this study is to demonstrate spontaneous CSF rhinorrhea as the primary presentation of IIH and explore the algorithm of management. All patients with spontaneous (primary) CSF rhinorrhea were included with complete clinical and radiological assessment. We performed lumbar puncture and CSF pressure measurements in the lateral decubitus position for all included patients to detect those with intracranial hypertension. A pressure of 20 cmH2O in cases of CSF rhinorrhea is considered a cutoff for diagnosing raised intracranial pressure. When intracranial hypertension was diagnosed, patients were subjected immediately to lumboperitoneal shunt. If CSF leakage stopped after shunt insertion, we would not perform skull base repair, and the patient was sent for follow-up. However, if CSF leakage did not stop after shunt insertion despite normalization of intracranial tension or recurrence of CSF rhinorrhea despite shunt patency or there was intracranial pneumocephalus, skull base repair would be performed. During the period of the study, 293 cases of CSF rhinorrhea were seen. Only 42 (14.3%) patients were diagnosed with spontaneous CSF rhinorrhea, and the remaining were posttraumatic. Thirty-seven patients (88.1%) of 42 patients revealed high CSF pressure readings. All 37 patients received lumboperitoneal shunt followed by CSF rhinorrhea stoppage. Later, during follow-up, 7 patients developed recurrence of leakage; 3 of them revealed shunt obstruction, and rhinorrhea improved after shunt revision. The other 4 patients revealed patent shunt and needed skull base repair. Spontaneous CSF rhinorrhea is considered secondary to IIH until proven otherwise. Initial placement of lumboperitoneal shunt may provide an effective alternative to skull base repair for the treatment of patients with IIH presenting with CSF rhinorrhea.

DYNAMIC POSITION MEASUREMENT OF THE CNC MACHINE USING LASER INTERFEROMETRY

Currently, emphasis is placed on the ever-higher accuracy and speed of measuring the geometric accuracy of CNC machine tools. Achieving the highest possible accuracy is often time-consuming, which results in higher financial costs. The purpose of this study was to verify the suitability of the dynamic measurement of the position CNC machine based on laser interferometry using angular optics concerning static measurement. In the case of both measurements, a commercially available laser interferometer XL-80 was used. First, a static measurement was performed on the horizontal X axis, then a set of dynamic measurements was performed, and the last static measurement was evaluated as a control. The test therefore assesses the accuracy of dynamic position measurement in accordance with ISO 230-2 parameters. The advantage of dynamic measurement is the provision of a more realistic and detailed view of CNC machine tool errors thanks to the high resolution of the measurement itself. At the same time, this research opens another unexplored area of mutual synchronization of data obtained from the CNC machine and data from the reference method.

Formalization for Subsequent Computer Processing of Kara Sea Coastline Data

This study aimed to develop a methodological framework for predicting shoreline dynamics using machine learning techniques, focusing on analyzing generalized data without distinguishing areas with higher or lower retreat rates. Three sites along the southwestern Kara Sea coast were selected for this investigation. The study analyzed key coastal features, including lithology, permafrost, and geomorphology, using a combination of field studies and remote sensing data. Essential datasets were compiled and formatted for computer-based analysis. These datasets included information on permafrost and the geomorphological characteristics of the coastal zone, climatic factors influencing the shoreline, and measurements of bluff top positions and retreat rates over defined time periods. The positions of the bluff tops were determined through a combination of imagery with varying resolutions and field measurements. A novel aspect of the study involved employing geostatistical methods to analyze erosion rates, providing new insights into the shoreline dynamics. The data analysis allowed us to identify coastal areas experiencing the most significant changes. By continually refining neural network models with these datasets, we can improve our understanding of the complex interactions between natural factors and shoreline evolution, ultimately aiding in developing effective coastal management strategies.

Quantum information of a relativistic particle with position-dependent mass under the Aharonov–Casher effect

In this work, the influence of the Aharonov–Casher (AC) effect is investigated for a relativistic particle with position-dependent mass through Shannon quantum information. Shannon’s formalism is appropriate because its results suggest explanations for the measurement uncertainties of a quantum system. To calculate Shannon’s entropy, it is necessary to obtain the description of quantum eigenstates. Using the eigenstates obtained, we analyzed the system quantum information in position and momentum space. Considering the results of Shannon’s entropy, it is possible to understand the influence of the AC effect and the position-dependent mass on the quantum information. It was possible to notice that the informational content decreases in the position space when we increase the value of the parameter that controls the mass profile. This result is strong, as it indicates a decrease in uncertainties related to particle position measurements. The opposite happens when we increase the quantum phase ΦAC.

The presence of a Segond fracture in ACL-injured patients is associated with increased internal tibial rotation on preoperative MRIs

BackgroundSegond fracture is considered a component of the anterolateral complex (ALC) injury, yet the underlying cause and clinical outcomes of this bony avulsion remain subjects of debate. Additionally, MRI measurements of altered tibiofemoral position in anterior cruciate ligament (ACL)-injured patients with a Segond fracture have not been reported. The purpose of this study is to measure the rotational tibiofemoral position on MRI in ACL-injured patients with a Segond fracture.MethodsA total of 44 patients with a primary ACL injury and a concomitant Segond fracture were included in the Segond fracture group, with the time from injury to MRI within 3 months. Avulsion was confirmed via preoperative computed tomography (CT) scans. The control group comprised 44 matched patients with primary ACL injury and an MRI-determined ALC injury but without a Segond fracture, also with the time from injury to MRI within 3 months. The MRI-determined ALC injury included injuries to the anterolateral ligament, Kaplan fibers, and anterolateral joint capsule, as identified based on previous studies. Sex, age, and BMI were matched between the two groups using propensity score matching (PSM). Arthroscopic findings, concomitant collateral ligament injuries, and preoperative MRI measurements were compared between the two groups.ResultsThe Segond fracture group demonstrated a higher frequency of concomitant patellar and femoral trochlear injuries (p = 0.0110) and lateral collateral ligament injuries (p = 0.0121) compared to the control group. Additionally, significantly increased internal rotational tibial subluxation (IRTS) (p = 0.0095) and axial internal tibial rotation (ITRa) (p = 0.0306) were observed in the Segond fracture group. A strong positive correlation was found between IRTS and ITRa (rp = 0.8201), indicating that these two tibial rotation measurement methods were correlated. No significant differences were observed in the measurements of anteroposterior tibiofemoral position and posterior tibial slope (PTS) between the two groups.ConclusionThe presence of a Segond fracture was associated with significantly increased internal tibial rotation measured on MRIs, suggesting that this bony avulsion may represent a more severe form of ALC injury in ACL-injured patients and should be managed with caution.

Partial Alignment of Astrometric Position Excursions of International Celestial Reference Frame Quasars with Radio Jet Structures

Abstract Published analyses of very long baseline interferometry data for the sources included in the third International Celestial Reference Frame catalog have revealed object-specific, excess astrometric variability and quasi-coherent trajectories as functions of time. A fraction of these sources show markedly elongated distributions of positions on the sky measured with diurnal observations. Here we apply a novel statistical and data-processing method to the diurnal position measurements stretching over 40 yr to quantify the degree of elongation and its position angle, for each source with more than 200 data points. We find that 49% of the examined sources have distribution elongations in excess of 1.3. Robust uncertainties of the directions of maximal astrometric dispersion are computed by the bootstrapping method, and the results are compared with a larger catalog of radio jet directions by A. V. Plavin et al. (2022). Nearly one-half of the sources with smaller position angle uncertainties are found to have astrometric position excursions from their mean positions aligned with the radio jet structures within ±30°.

Precise Z-Block positioning and dimension measurement using improved Canny edge detection and sub-pixel contour fitting

Precise Z-Block positioning and dimension measurement using improved Canny edge detection and sub-pixel contour fitting

Bunch-by-bunch position measurement with sub-micron resolution at nanoseconds separation using wideband cavity beam position monitors.

We developed a wideband RF cavity beam position monitor (CBPM) with a 217MHz bandwidth centered at the 4.875GHz dipole mode frequency as part of the preliminary research for a high-repetition-rate hard x-ray free electron laser project at the Chinese Academy of Engineering Physics. This paper presents new results demonstrating bunch-by-bunch position measurements on electron bunches spaced by 2.3ns (4 bunches per train). Over a measurement range of ∼100μm, this wideband CBPM achieved a spatial resolution of 0.8μm at a bunch charge of 80 pC. Position and tilt variations between bunches on the order of 10μm and 10 μrad, respectively, were clearly resolved. This high spatial and temporal resolution provides a valuable tool for experimental studies on long-range wakefield effects in multi-bunch operational light sources.

Measurements of Minor Loop Position and Shape Depending on Inductor Excitation Process

Measurements of Minor Loop Position and Shape Depending on Inductor Excitation Process