Radial Error Research Articles

Evaluating the accuracy of automated cephalometric analysis based on artificial intelligence

BackgroundThe purpose of this study was to evaluate the accuracy of automatic cephalometric landmark localization and measurements using cephalometric analysis via artificial intelligence (AI) compared with computer-assisted manual analysis.MethodsReconstructed lateral cephalograms (RLCs) from cone-beam computed tomography (CBCT) in 85 patients were selected. Computer-assisted manual analysis (Dolphin Imaging 11.9) and AI automatic analysis (Planmeca Romexis 6.2) were used to locate 19 landmarks and obtain 23 measurements. Mean radial error (MRE) and successful detection rate (SDR) values were calculated to assess the accuracy of automatic landmark digitization. Paired t tests and Bland‒Altman plots were used to compare the differences and consistencies in cephalometric measurements between manual and automatic analysis programs.ResultsThe MRE for 19 cephalometric landmarks was 2.07 ± 1.35 mm with the automatic program. The average SDR within 1 mm, 2 mm, 2.5 mm, 3 and 4 mm were 18.82%, 58.58%, 71.70%, 82.04% and 91.39%, respectively. Soft tissue landmarks (1.54 ± 0.85 mm) had the most consistency, while dental landmarks (2.37 ± 1.55 mm) had the most variation. In total, 15 out of 23 measurements were within the clinically acceptable level of accuracy, 2 mm or 2°. The rates of consistency within the 95% limits of agreement were all above 90% for all measurement parameters.ConclusionAutomatic analysis software collects cephalometric measurements almost effectively enough to be acceptable in clinical work. Nevertheless, automatic cephalometry is not capable of completely replacing manual tracing. Additional manual supervision and adjustment for automatic programs can increase accuracy and efficiency.

Magnetic Resonance-Guided Stereotaxy for Infusions to the Pig Brain.

The overall goal of this procedure is to perform stereotaxy in the pig brain with real-time magnetic resonance (MR) visualization guidance to provide precise infusions. The subject was positioned prone in the MR bore for optimal access to the top of the skull with the torso raised, the neck flexed, and the head inclined downward. Two anchor pins anchored on the bilateral zygoma held the head steady using the head holder. A magnetic resonance imaging (MRI) flex-coil was placed rostrally across the head holder so that the skull was accessible for the intervention procedure. A planning grid placed on the scalp was used to determine the appropriate entry point of the cannula. The stereotactic frame was secured and aligned iteratively through software projection until the projected radial error was less than 0.5 mm. A hand drill was used to create a burr hole for insertion of the cannula. A gadolinium-enhanced co-infusion was used to visualize the infusion of a cell suspension. Repeated T1-weighted MRI scans were registered in real time during the agent delivery process to visualize the volume of gadolinium distribution. MRI-guided stereotaxy allows for precise and controlled infusion into the pig brain, with concurrent monitoring of cannula insertion accuracy and determination of the agent volume of distribution.

Prediction of the degeneration of radial error motion of a motorized spindle considering the load

Prediction of the degeneration of radial error motion of a motorized spindle considering the load

Adaptive group-wise modeling of thermally induced errors of a turning center

Traditional multivariate regression analysis-based thermal error models use only one polynomial of several temperature variables to predict thermal errors, which will produce lower local prediction accuracy for a longer machining process with sudden changes of machining parameters, and hence the group-wise modeling method is proposed in this paper. Resorting to hard break points and soft break points, the grouping work is completed in two steps: hard grouping and soft grouping. The positions of hard break points are optimized using the genetic algorithm toolbox in Matlab software to realize adaptive grouping. The mechanism for updating the thermal error model coefficients vectors for different soft groups is developed. The modeling test is carried out on a turning center for which the positions of thermal key points are optimized. The prediction results for radial and axial thermal errors show that four hard break points can basically meet the requirements at the di value of 80%, so the group-wise modeling method is helpful to advance the prediction accuracy of thermal errors.

Response of Meteor Plasma Trails Observed by Meteor Radar to Geomagnetic Activity

AbstractFrom meteor radar observations typically measuring neutral winds and temperatures in the upper atmosphere, we showed that under‐dense meteor plasma trails respond to geomagnetic activity. Depending on the geomagnetic activity conditions, the parameters of the under‐dense trail echoes show substantial anomalies, and their responses are immediate. As geomagnetic activity increases, the decay time decreases up to about 10% at Kp = 8, while both the returned signal power and radial velocity error increase. In addition, the types of diffuse evolution vary with geomagnetic activity, resulting in strong geomagnetic activity that immediately affects the trail. The evolution of the trail is affected not only by the ambient mesospheric neutral atmospheric properties but also by electromagnetic effects, such as strong electric fields inside meteor trails. Furthermore, our findings suggest that the geomagnetic effect should be considered when estimating atmospheric parameters from MR during a geomagnetically active period.

An evaluation method of GPS satellite clock in-orbit with periodic terms deducted

The performance of the atomic clock in orbit is of terrific significance for the Global Navigation Satellite System (GNSS). With the rapid development of satellite navigation and atomic clock technology, the periodic error of satellite clocks caused by the environment is more prominent. This paper focuses on the analysis and quantification of the systematic periodic error in the clock offset and proposes a more accurate evaluation method for GPS satellite clocks. The fact that the J2 relativistic effect and orbit radial error are the main sources of the systematic periodic term has been revealed. Then, the Fast Fourier Transform (FFT) is employed using the sliding window to investigate the periodic influence caused by satellite orbit and the J2 relativistic effect on clock offset through six GPS satellites with different orbital planes, these satellites also cover all four types of GPS satellite blocks. The results show that there is an obvious relationship between the sun elevation and orbit radial error, clock offset fitting precision, frequency stability and amplitude. The different geometric configurations of the satellite and the varying environment make this relationship different. Based on the clock offset provided by European Space Agency (ESA), the period of clock offset is extracted and quantized, with the period of 24 h, 12 h, 8 h, 6 h, 4 h, and 3 h. According to the daily extraction results of the time-varying periodic terms, the two most noticeable terms correction on satellite clock offset has been proven to be effective in eliminating periodic errors. Compared to those without periodic correction, the fitting precision and frequency stability can improve by 48.5% and 42.6%, respectively. In addition, all GPS satellite clocks in orbit are evaluated by this periodic correction method, and the results are more approach to the actual performance of the satellite clock. Furthermore, this method can also be adapted to evaluate satellite clocks of other GNSS systems. Therefore, when we evaluate the high-precision atomic clock flying on board GNSS satellites and compare them with the manufacturers’ specifications, the periodic error cannot be neglected.

In Situ Measurement of Spindle Radial Error for Ultra-Precision Machining Based on Three-Point Method

The radial error is an important parameter to evaluate the performance of ultra-precision spindles. The three-point method has not yet been well applied in nanometer-scale measurement due to its disadvantages of harmonic suppression and the complicated error separation process. In order to verify that the three-point method can realize the nanometer-scale measurement of the radial error in the machining environment, an in situ measurement and evaluation system is established. Experiments are performed using the system, and a comparative experiment is conducted to verify the accuracy of the system. The average value and standard deviation of the measurement results are 23.096 nm and 0.556 nm, respectively. The in situ measurement result was in good agreement with the Donaldson reversal method using a commercially available spindle analyzer.

Frameless Robot-Assisted Asleep Centromedian Thalamic Nucleus Deep Brain Stimulation Surgery in Patients with Drug-Resistant Epilepsy: Technical Description and Short-Term Clinical Results.

This purpose of this work is to give a detailed description of a surgical technique for frameless robot-assisted asleep deep brain stimulation (DBS) of the centromedian thalamic nucleus (CMT) in drug-resistant epilepsy (DRE). Ten consecutively enrolled patients who underwent CMT-DBS were included in the study. The FreeSurfer "Thalamic Kernel Segmentation" module and experience target coordinates were used for locating the CMT, and quantitative susceptibility mapping (QSM) images were used to check the target. The patient's head was secured with a head clip, and electrode implantation was performed with the assistance of the neurosurgical robot Sinovation®. After opening the dura, the burr hole was continuously flushed with physiological saline to stop air from entering the skull. All procedures were performed under general anesthesia without intraoperative microelectrode recording (MER). The mean age of the patients at surgery and onset of seizures was 22years (range 11-41years) and 11years (range 1-21years), respectively. The median duration of seizures before CMT-DBS surgery was 10years (2-26years). CMT was successfully segmented, and its position was verified by experience target coordinates and QSM images in all ten patients. The mean surgical time for bilateral CMT-DBS in this cohort was 165 ± 18min. The mean pneumocephalus volume was 2 cm3. The median absolute errors in the x-, y-, and z-axes were 0.7mm, 0.5mm, and 0.9mm, respectively. The median Euclidean distance (ED) and radial error (RE) was 1.3 ± 0.5mm and 1.0 ± 0.3mm, respectively. No significant difference was found between right- and left-sided electrodes regarding the RE nor the ED. After a mean 12-month follow-up, the average reduction in seizures was 61%, and six patients experienced a ≥ 50% reduction in seizures, including one patient who had no seizures after the operation. All patients tolerated the anesthesia operation, and no permanent or serious complications were reported. Frameless robot-assisted asleep surgery is a precise and safe approach for placing CMT electrodes in patients with DRE, shortening the surgery time. The segmentation of the thalamic nuclei enables the precise location of the CMT, and the flow of physiological saline to seal the burr holes is a good way to reduce the influx of air. CMT-DBS is an effective method to reduce seizures.

Research on Magnetic-Induced Error of Small-Sized Fiber Optic Gyro Fiber Coil in Space Environment

Spacecraft is severely limited in weight and volume, resulting in a small bending radius of the fiber coil used by IFOG (Interference Fiber Optic Gyroscope). The fiber coil has such a size that the influence of bending on fiber birefringence cannot be ignored. In this paper, we research magnetic-induced errors of small-sized IFOG working in low orbit space. Firstly, we use the Jones matrix to analyze the effects of radial magnetic field and axial magnetic field on IFOG. Secondly, we establish a three-dimensional model for the radial magnetic-induced errors and magnetic-induced errors of minor radius fiber coil. Using the finite element method, we analyze the magnetic-induced error between different levels of the fiber coil. Combined with the birefringence distribution of the minor radius fiber coil, an accurate three-dimensional magnetic-induced error model is established. Thirdly, in the experiment, we design the magnetic-induced error test platform that includes the Fluke standard current source, transconductance amplifier, and Helmholtz coil. The experimental results show that, compared with the traditional calculation method, the three-dimensional magnetic-induced error model reduces the RMSE (Root Mean Square Error) of the radial magnetic field by 56.9% and the RMSE of the axial magnetic field by 35.7%, respectively.

Recovery of kicking kinematics and performance following repeated high-intensity running bouts in the heat: Can a rapid local cooling intervention help young soccer players?

ABSTRACT The effects of a cooling strategy following repeated high-intensity running (RHIR) on soccer kicking performance in a hot environment (>30ºC) were investigated in youth soccer players. Fifteen academy under-17 players participated. In Experiment 1, players completed an all-out RHIR protocol (10×30 m, with 30s intervals). In Experiment 2 (cross-over design), participants performed this running protocol under two conditions: (1) following RHIR 5 minutes of cooling where ice packs were applied to the quadriceps/hamstrings, (2) a control condition involving passive resting. Perceptual measures [ratings of perceived exertion (RPE), pain and recovery], thigh temperature and kick-derived video three-dimensional kinematics (lower limb) and performance (ball speed and two-dimensional placement indices) were collected at baseline, post-exercise and intervention. In Experiment 1, RHIR led to small-to-large impairments (p < 0.03;d = −0.42–-1.83) across perceptual, kinematic and performance measures. In experiment 2, RPE (p < 0.01; Kendall’s W = 0.30) and mean radial error (p = 0.057; η2 = 0.234) increased only post-control. Significant small declines in ball speed were also observed post-control (p < 0.05; d = 0.35). Post-intervention foot centre-of-mass velocity was moderately faster in the cooling compared to control condition (p = 0.04; d = 0.60). In youth soccer players, a short cooling period was beneficial in counteracting declines in kicking performance, in particular ball placement, following intense running activity in the heat.

Prestress Modal Analysis under Assembling Error of Diaphragm Disc Coupling

The high-speed and high-torque diaphragm disc coupling used in coal machine-driven systems is the critical power transmission component, especially in high-speed and heavy-duty shafting. The dynamic rotor characteristics are significant. In the case of external excitation in the installation or working process of diaphragm coupling, it is inevitable to have axial deviation, angular misalignment, and radial misalignment error. Therefore, analyzing the prestress mode under the assembly error of diaphragm disc coupling is crucial. The finite element model of diaphragm plate coupling was established using ABAQUS software. The accessible way under critical speed, the mode under axial dislocation, and radial dislocation were analyzed. The results show that the assembly error of the diaphragm disc coupling will affect the first and second-order natural frequencies in a specific range but will not cause resonance.

지각적 관찰학습을 통한 야구 피칭 동작의 운동학적 분석 : 운동 타이밍과 수행 정확성 중심으로

The purpose of this study is to compare the changes in performance according to the speed of playback of the video on overarm-pitching learning. 25 novice subjects were assigned into five groups (control, 33%, 66%, 100%, 133% speed conditions relative to the actual playback speed). After observing each video for 10 minutes, all subjects performed a task of throwing a baseball to the target as fast as possible. For comparison of learning effect, movement time and radial error were measured. The 66% video playback speed group showed that the tempo was reduced during the wind-up phase. However, the 133% video playback speed group showed that the tempo was increased in stride phase. With the change in motor timing, the 66% and 133% groups exhibited reduced spatial accuracy. In conclusion, the motor tempo has been effected depending on the level of video playback speed. However, internal rhythm was hard to change by observational learning in the early stages. And, large difference in playback speed with the actual video had no significant changes in motor timing. Consequently, the tempo of the movement and the different levels of perceptive speed must be considered in learning the timing.

A novel method for measuring radial and axial errors in a cylindrical coordinate system using a combined double ball bar

Multiaxis machine tools are widely used in manufacturing. The measurement of motion error is important to improve the machining accuracy of machine tools. A double ball bar (DBB), as a high-precision single-dimensional position reading device, is widely used to measure the motion error of the circular path of machine tools. However, the motion errors contain the cylindrical radial and axial errors with respect to the circular path plane. Therefore, the measurement results of the DBB are incomplete because they do not contain axial errors. To measure the motion error of the circular path accurately, completely and concisely, a novel measurement method based on the combined DBB (C-DBB) is proposed in this paper, which can directly measure the radius and axial motion error of the circular path in one measurement. First, the measuring principle of the C-DBB method is introduced, and the measurement model of the radius and axial motion error of the circular path is established. Then, a measuring device using the C-DBB method was designed based on the lever principle, and the error parameters of the designed device were analyzed. According to the error analysis results, the measurement results of the C-DBB method were compensated and corrected. Finally, the C-DBB method is used to measure the circular path on the vertical CNC milling machine, and the results are compared with the measurement results using the DBB method. It is shown that the proposed C-DBB method can obtain high-precision multidimensional motion error in a single measurement, and the designed measuring device based on the C-DBB method has high repeatability and good circular path measuring ability. The proposed method provides an effective method for machine tool multidimensional motion error measurement and compensation.

Research on development of aspheric diffractive optical element for mid-infrared imaging

The aspheric diffractive lens reduces chromatic aberration in precision infrared optical systems. With the advancement in micro-optics, conventional lenses are replaced by aspheric, diffractive and hybrid surfaces to fulfil the requirements of miniaturized design of optical devices. This paper covers the detailed aspects of hybrid aspheric diffractive optics from design to manufacturing by precision machining. The germanium aspheric diffractive lens is designed using Zemax OpticsStudio® for Medium Wave Infrared (MWIR) range to achieve an aberration-free and diffraction-limited surface. The designed surface is fabricated by the diamond turning process. The developed surface is characterized by profile and diffractive structure quality. The results demonstrate the fabricated lens with a diffractive structure step height error of 0.001 µm and radial position error of 1 µm. A high-quality aspheric diffractive lens is fabricated with 99.57 % diffraction efficiency.

Separation of rotary table radial error motions in gear pitch measurements using harmonic regeneration

During precision or on-machine gear pitch measurements, radial error motions of the rotary table (RT) are non-negligible factors that affect the measurement accuracy and repeatability. In this paper, an error separation method using harmonic regeneration (the ES–HR method) is presented to reduce the influence of the RT radial error motions. First, the gear pitch deviations are measured over several laps. Then, the measurement results are decomposed into different period components by a discrete Fourier transform and the integral period components are extracted to regenerate the pitch deviations. Using this method, the influence of the non-integral period RT radial error motions and most of the random errors can be eliminated. Finally, the influence of the integral period RT radial error motions, acquired synchronously or in advance, are subtracted from the regenerated pitch deviations and the actual gear pitch deviations without the influence of RT radial error motions are obtained. Experimental results showed that this proposed method can effectively eliminate the influence of the RT radial error motions and has better accuracy and less uncertainty than the pitch deviations evaluation algorithm that uses a multi-lap average. Additionally, this method does not require changes in the position of the gear relative to the RT as do existing error separation methods, and it can be easily used for measurements at production sites or on machines.

A novelty mandrel supported thin-wall tube bending cross-section quality analysis: a diameter-adjustable multi-point contact mandrel

The mandrel plays a vital role in metal tube bending limit improvement and high-quality achievement. For the bending forming process of metal tubes with different diameters, the corresponding mandrel needs to be customized, which has the disadvantages of a long design cycle, high manufacturing cost, and low reuse rate. Therefore, a novelty concept of diameter adjustable mandrel (DAM) based on the multi-point contact was proposed to adapt different diameter tube bending processes. Since the point-contact characteristics of the DAM can lead to irregular cross-section deformation, the cross-sectional full profile radial error (FP-RE) model was proposed. As a more comprehensive evaluation model, the FP-RE model is used to measure the deformation degree of the whole bending cross-section. A diameter-adjustable DAM was adopted in the AISI 304L tubes (the inner diameter = 40–56 mm) bending experiments. The maximum absolute error of FP-RE was 0.11% compared with the ones obtained from FEA in Abaqus/explicit. In addition, the effects of the DAM characteristic parameters, viz., the support blocks amount, the effective magnification, and the effective support diameter, on the tube forming quality were discussed. The results indicated that (a) an even number of support blocks could prevent the collapse of the outer convex tube wall and improve the quality of the inner concave tube wall. (b) When the DAM was used in the larger inner diameter tube bending, the larger non-contact area would cause an increase in the roundness section distortion. (c) A larger DAM diameter would lead to a more minor cross-section deformation degree for the tubes with the same diameter, while the wall thinning was just the opposite. Finally, the result also proved that the DAM (the minimum effective diameter is 40 mm with six support blocks) could be used for tubes with an inner diameter of about 40–56 mm, and the forming quality was acceptable.

B-Spline-Based Curve Fitting to Cam Pitch Curve Using Reinforcement Learning

Directly applying the B-spline interpolation function to process plate cams in a computer numerical control (CNC) system may produce verbose tool-path codes and unsmooth trajectories. This paper is devoted to addressing the problem of B-spline fitting for cam pitch curves. Considering that the B-spline curve needs to meet the motion law of the follower to approximate the pitch curve, we use the radial error to quantify the effects of the fitting B-spline curve and the pitch curve. The problem thus boils down to solving a difficult global optimization problem to find the numbers and positions of the control points or data points of the B-spline curve such that the cumulative radial error between the fitting curve and the original curve is minimized, and this problem is attempted in this paper with a double deep Q-network (DDQN) reinforcement learning (RL) algorithm with data points traceability. Specifically, the RL environment, actions set and current states set are designed to facilitate the search of the data points, along with the design of the reward function and the initialization of the neural network. The experimental results show that when the angle division value of the actions set is fixed, the proposed algorithm can maximize the number of data points of the B-spline curve, and accurately place these data points to the right positions, with the minimum average of radial errors. Our work establishes the theoretical foundation for studying spline fitting using the RL method.

Accurate Deep Brain Stimulation Lead Placement Concurrent With Research Electrocorticography.

Using electrocorticography for research (R-ECoG) during deep brain stimulation (DBS) surgery has advanced our understanding of human cortical-basal ganglia neurophysiology and mechanisms of therapeutic circuit modulation. The safety of R-ECoG has been established, but potential effects of temporary ECoG strip placement on targeting accuracy have not been reported. To determine whether temporary subdural electrode strip placement during DBS implantation surgery affects lead implantation accuracy. Twenty-four consecutive patients enrolled in a prospective database who underwent awake DBS surgery were identified. Ten of 24 subjects participated in R-ECoG. Lead locations were determined after fusing postoperative computed tomography scans into the surgical planning software. The effect of brain shift was quantified using Lead-DBS and analyzed in a mixed-effects model controlling for time interval to postoperative computed tomography. Targeting accuracy was reported as radial and Euclidean distance errors and compared with Mann-Whitney tests. Neither radial error nor Euclidean distance error differed significantly between R-ECoG participants and nonparticipants. Pneumocephalus volume did not differ between the 2 groups, but brain shift was slightly greater with R-ECoG. Pneumocephalus volume correlated with brain shift, but neither of these measures significantly correlated with Euclidean distance error. There were no complications in either group. In addition to an excellent general safety profile as has been reported previously, these results suggest that performing R-ECoG during DBS implantation surgery does not affect the accuracy of lead placement.

Automatic analysis of lateral cephalograms based on high-resolution net

Cephalometric analysis is essential in orthodontic treatment, and it is progressing toward automatic cephalometric analysis. This study aimed to establish a cephalometric landmark detection model on the basis of a high-resolution net and improve the accuracy with high resolution. A total of 2000 lateral cephalograms were collected to construct a dataset, and the number of target landmarks was 51. A high-resolution network model was applied to the landmark detection task. Four models were trained by adjusting different input resolutions to choose the most suitable resolution. A test set consisting of 300 lateral cephalograms was used for evaluation. The model was evaluated from the error size and distribution of each landmark. After 200 epochs of training, a landmark detection model was established. Under different resolutions of the input image, the mean model radial error decreased initially and then increased. At 680 × 920 pixels resolution, the minimum error and the highest detection success rate were obtained. The mean radial error was 1.08 ± 0.87 mm. The detection success rates of 2.0 mm, 2.5 mm, 3.0 mm, and 4.0 mm were 89.00%, 94.00%, 96.33%, and 98.67%, respectively. The mean radial errors of 22 landmarks were<1 mm, and the errors of other landmarks were<2 mm except for the pterion. The error distribution of landmarks followed a certain pattern. An automatic landmark detection model based on a high-resolution net was established to recognize 51 landmarks. The model showed high detection accuracy, which provides a basis for further measurement application.

Indirect neural-based finite-time integral sliding mode control for trajectory tracking guidance of Mars entry vehicle

This article presents an indirect neural-based finite-time integral sliding mode control algorithm for the reference trajectory tracking guidance of Mars entry vehicle under uncertainties. The proposed controller is developed as a combination of finite-time integral sliding mode controller and indirect neural identification. The finite-time integral sliding mode controller is designed by constructing a new type of finite-time integral sliding mode surface to prevent the singularity problem. Moreover, the neural network (NN) is combined with the finite-time integral sliding mode controller to identify the lumped uncertainty and attenuate the chattering phenomenon. Particularly, the concept of indirect neural identification is adopted and only a single adaptive parameter is required to be learned online. In this way, the proposed controller is not only strongly robust against aerodynamic and density uncertainties, but also computationally simple for onboard implementations. Stability argument indicates that the proposed controller can ensure the radial distance tracking error and its time differentiation regulate to the small residual sets around zero in finite time. Lastly, the effectiveness and excellent guidance performance of the proposed control algorithm are demonstrated through simulation studies on a Mars Science Laboratory-type (MSL-type) entry vehicle.