Accurate Rotation Research Articles

[formula omitted]Beach: Self-attention-based spatiotemporal network for skillful prediction of shoreline changes multiple days ahead

We developed a self-attention-based spatiotemporal network called alphaBeach that uses spatiotemporal representation learning for skillful prediction of shoreline changes multiple days ahead. The proposed model predicts the spatiotemporal position of the shoreline up to seven consecutive days in the future based on hydrodynamic forcing of ocean waves and tide data for the past 30 consecutive days. It is further divided into alphaBeach-w/oIC and alphaBeach-w/IC depending on whether or not the beach state of the antecedent historical shoreline information is used as the initial condition. alphaBeach-w/oIC, which does not incorporate this information, learns the sequential relationship between hydrodynamic forcing and shoreline to estimate overall trends of shoreline changes including seasonal oscillation from the point in time after model training, given only the ocean waves and tides. alphaBeach-w/IC does incorporate antecedent historical shoreline information to greatly enhance its predictive accuracy of shoreline progradation, retreat, and beach rotation for short-term time scales and for extreme storm events. The proposed model was applied to Tairua Beach, New Zealand, and it demonstrated superior predictive accuracy compared to previous methods and matched current understanding of accretion-dominated and oscillation-dominated shoreline changes.

An efficient single-shot global localization method for indoor mobile robots usingphase correlation

Purpose The purposes of this paper are to solve the low-efficiency problem caused by large search space in global localization and develop an efficient global localization method requiring only one 2D-LiDAR scan to match against the prior map for indoor mobile robots. Design/methodology/approach This paper solves the global localization problem using phase correlation as the underlying registration method. To obtain accurate rotation parameter, this paper exhaustively pre-rotates the prior map by a certain angle stride in advance. Then the input scan is matched against the pre-rotated maps one by one using phase correlation to determine translation parameters, and this paper constructs an orientation histogram by the correlation coefficients. The map rotation angle and corresponding translation parameters of the maximal peak value in the orientation histogram constitute the global pose. This paper applies a divide-and-conquer method to reduce the time consumption of single phase correlation and determines promising angle ranges where the maximal peak value may appear based on the periodicity of 90º in the orientation histogram with the signal-to-noise ratio (SNR) to reduce execution times of phase correlation. Findings Both simulated and real experimental results reveal that the proposed method achieves a high enough success rate and efficient (processing time in a second) global localization. Originality/value The proposed method constructs an orientation histogram to improve the global localization success rate and applies a divide-and-conquer method with SNR to improve efficiency, which will benefit the indoor mobile robots equipped with 2D-LiDAR.

A radiation therapy platform to enable upright cone beam computed tomography and future upright treatment on existing photon therapy machines

AbstractBackgroundThe conventional lying down position for radiation therapy can be challenging for patients due to pain, swallowing or breathing issues. To provide an alternative upright treatment position for these patients, we have developed a portable rotating radiation therapy platform which integrates with conventional photon treatment machines. The device enables cone‐beam computed tomography (CBCT) imaging of patients in an upright position, and the future delivery of therapeutic radiation.PurposeTo design, manufacture, and test a device for upright radiation therapy. A collaborative partnership between physicists, engineers, radiation therapists, radiation oncologists, implementation researchers and consumers was established, to create a device that meets both the clinical and technical requirements of upright radiation therapy. The device is central to a clinical trial (ACTRN12623000498695) which will evaluate upright image quality in the context of future image guided radiation therapy for patients with lung cancer or head and neck cancer.MethodsThe weight and physical constraints of the device were assessed with respect to the American civilian population. The final design was evaluated with a series of tests to characterize the angular accuracy of the platform rotation and the reproducibility of the platform setup position in a radiation treatment room. To acquire an upright CBCT, the platform movement system was synchronized to the kilo‐voltage fluoroscopic imaging on an existing treatment machine. The accuracy of the synchronization was evaluated by assessing the positional reproducibility of upright CBCT imaging of a chest phantom.ResultsThe platform has a weight limit of up to 125 kg which is suitable for approximately 90% of males and 95% of females. The platform has physical constraints that accommodate approximately 95.6% of males and 99.6% of females: a maximum seated height of 97.5 cm, a maximum hip breadth of 63.0 cm, and maximum elbow to knuckle length of 46.5 cm. The angular accuracy of the motion system is within ±0.15° over a full rotation, which is within the guidelines for machine movement accuracy in radiation therapy (1 mm/1°). The platform is a portable device and can be reproducibly positioned in a radiation therapy treatment room with a translational range within ±0.04 mm and a rotational range within ±0.025°. The CBCT imaging can reproducibly detect the position of a chest phantom with a translational uncertainty of ±0.07 mm and a rotational uncertainly of ±0.22°, when imaging is acquired following a strict procedure.ConclusionThe upright radiation therapy platform is suitable for the evaluation of CBCT imaging in the context of image guided radiation therapy. The platform will allow the investigation of open questions in upright radiation therapy in the areas of patient experience, positional stability, anatomical changes, and treatment delivery. Improvements to the materials in the radiation beam line, synchronization with the existing treatment machine, and increasing the device weight limit are suggested prior to delivery of future upright treatments.

Age-stratified assessment of orthodontic tooth movement outcomes with clear aligners

ObjectiveThis study compared the achieved tooth movement to that predicted in the preliminary simulated digital treatment plan between adults and teenagers.Materials and methodsRecords of 60 patients (30 adults; mean age: 36.6 ± 11.36 years, and 30 teenagers; mean age: 16.23 ± 2.25 years) were randomly selected. Initial and predicted models were obtained from the initial simulated treatment plan. The first model of the refinement scan was labeled as achieved. SlicerCMF software (version 3.1; https://www.slicer.org) was used to superimpose the achieved and predicted digital models over the initial ones with regional superimposition on relatively stable first molars. 600 teeth were measured in each group for horizontal, vertical, angular movements, and transverse dimensions. Accuracy was defined as the achieved amount of movement minus predicted and was calculated for each individual and compared between teens and adults.ResultsThe mandibular inter-canine width accuracy was statistically significant between groups (p = 0.050). Significant under-correction in horizontal movements was noted for mandibular first premolars in teenagers compared to adults (p = 0.037). There was considerable over-correction in horizontal movements for mandibular central and lateral incisors between groups (p < 0.05). No significant difference was observed between groups in the vertical plane. Rotations were underachieved for maxillary first premolars, more in adults than teenagers (p = 0.017).ConclusionThe accuracy of achieved versus predicted tooth movement between adults and teenagers was significant for the inter-canine width. Mandibular central and lateral incisors showed significantly greater over-correction in adults in the horizontal plane. The accuracy of rotations and vertical movements was comparable.

Scaling relations between mass components and rotational velocity in disk galaxies

Abstract In this study, we re-evaluate the baryonic Tully–Fisher relation (BTFR) by analyzing the correlations between maximum rotational velocity and various mass components, including stellar mass, atomic hydrogen (H i) mass, baryonic mass, and dark matter mass in a sample of 141 disk galaxies from the SPARC (Spitzer Photometry and Accurate Rotation Curves) database, augmented by recent data on stellar and dark matter masses. We apply multiple statistical methods, including Monte Carlo orthogonal distance regression (MCODR), Monte Carlo least-squares (MCLS), and traditional least-squares (LS), to assess the impact of different fitting techniques on the derived scaling relations between the mass components (stellar, H i, and dark matter) and maximum rotational velocities of these galaxies. We find that the selection of statistical methods significantly influences the derived slopes and intercepts the relation between maximum rotational velocity and mass components. The MCODR method that accounts for errors in both variables consistently produces steeper slopes, suggesting a stronger correlation between stellar mass and rotational dynamics compared to other methods. In contrast, the MCLS method tends to yield flatter slopes, highlighting the sensitivity of this approach to outliers. Despite the variations in slope and intercept across different methods, the fundamental relation between baryonic mass and rotational velocity remains robust. We have also compared dark matter mass derived from different halo models [NFW (Navarro–Frenk–White) versus combined NFW + Dekel–Zhao profiles] and noted that the slope from the NFW profile is slightly steeper than that from the combined profile, highlighting the sensitivity of scaling relations to the selection of halo model. Overall, this study reinforces the robustness of the BTFR across different mass components in disk galaxies while emphasizing the critical role of statistical methods and dark matter profiles in analyzing galactic dynamics.

High-resolution motion compensation for brain PET imaging using real-time electromagnetic motion tracking.

Substantial improvements in spatial resolution in brain positron emission tomography (PET) scanners have greatly reduced partial volume effect, making head movement the main source of image blur. To achieve high-resolution PET neuroimaging, precise real-time estimation of both head position and orientation is essential for accurate motion compensation. A high-resolution electromagnetic motion tracking (EMMT) system with an event-by-event motion correction is developed for PET-CTscanners. EMMT is comprised of a source, an array of sensors, and a readout electronic unit (REU). The source acts as a transmitter and emits an EM dipole field. It is placed in close proximity to the sensor array and detects changes in EM flux density due to sensor movement. The REU digitizes signals from each sensor and captures precise rotational and translational movements in real time. Tracked motion in the EMMT coordinate system is synchronized with the PET list-mode data and transformed into the scanner coordinate system by locating paired positions in both systems. The optimal rigid motion is estimated using singular value decomposition. The rigid motion and depth-of-interaction (DOI) parallax effect are corrected by event-by-event rebinning of mispositioned lines-of-response (LORs). We integrated the EMMT with our recently developed ultra-high resolution Prism-PET prototype brain scanner and a commercial Siemens Biograph mCT PET-CT scanner. We assessed the imaging performance of the Prism-PET/EMMT system using multi-frame motion of point sources and phantoms. The mCT/EMMT system was validated using a set of point sources attached to both a mannequin head and a human volunteer, for simulating multiframe and continuous motions, respectively. Additionally, a human subject for [18F]MK6240 PET imaging wasincluded. The tracking accuracy of the Prism-PET/EMMT system was quantified as a root-mean-square (RMS) error of 0.49 for 100 axial rotations, and an RMS error of 0.15 mm for 100 mm translations.The percent difference (%diff) in average full width at half maximum (FWHM) of point source between motion-corrected and static images, within a motion range of and 10 mm from the center of the scanner's field-of-view (FOV), was 3.9%. The measured recovery coefficients of the 2.5-mm diameter sphere in the activity-filled partial volume correction phantom were 23.9%, 70.8%, and 74.0% for the phantom with multi-frame motion, with motion and motion compensation, and without motion, respectively. In the mCT/EMMT system, the %diff in average FWHM of point sources between motion-corrected and static images, within a motion range of and 10 mm from the center of the FOV, was 14%. Applying motion correction to the [18F]MK6240 PET imaging reduced the motion-induced spill-in artifact in the lateral ventricle region, lowering its standardized uptake value ratio (SUVR) from 0.70 to 0.34. The proposed EMMT system is a cost-effective, high frame-rate, and none-line-of-sight alternative to infrared camera-based tracking systems and is capable of achieving high rotational and translational tracking accuracies for mitigating motion-induced blur in high-resolution brain dedicated PETscanners.

Evaluating Surgical Accuracy in Bimaxillary Surgery: A Systematic Review and Meta-Analysis of Mandible-First versus Maxilla-First Approaches.

Mandible-first surgery (MdFS) has gained attention as an alternative to the traditional maxilla-first surgery (MxFS) in bimaxillary procedures. Given the distinct sequence of operations between these approaches, evaluating the clinical advantages of MdFS compared to MxFS is crucial for optimizing surgical decision-making. This systematic review and meta-analysis examine intraoperative achievability and postoperative stability between these two surgical approaches. A thorough literature search was performed using PubMed, Embase, Web of Science, and MEDLINE, covering articles published from 2013 to 2023. Studies included were retrospective, prospective, and randomized trials that compared the accuracy and/or stability of MdFS with MxFS. The primary endpoint for the meta-analysis was the standardized mean difference in surgical accuracy for translational movements, with a secondary focus on rotational accuracy. A total of 11 studies encompassing 712 patients met the inclusion criteria. The analysis suggested that MdFS might reduce accuracy in the sagittal dimension (CI, 0.05 to 0.74) but offered greater achievability in the vertical direction (CI, - 0.47 to - 0.07). Additionally, MdFS was associated with a relatively posterior (CI, - 1.18 to - 0.60) and inferior (CI, - 0.64 to - 0.07) positioning of the maxillomandibular complex. Despite certain limitations, our findings indicate that MdFS can achieve clinical outcomes similar to MxFS in terms of both accuracy and stability. However, further researches with larger sample sizes and more rigorous study designs are necessary to validate these conclusions. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of contents or the online Instructions to Authors www.springer.com/00266 .

Design and Testing of Electric Drive System for Maize Precision Seeder

To improve the expandability, seeding accuracy, and operating speed range of the electric drive system (EDS) of precision seeders, this study constructed an EDS based on a controller area network (CAN) bus and designed a motor controller based on a field-orientated control (FOC) algorithm. Full-factorial bench and field tests based on seed spacing (0.1, 0.2, and 0.3 m) and operating speed (3, 6, 9, 12, and 15 km/h) were carried out to evaluate the performance of the EDS. The results of bench tests showed that seeding quality varied inversely with operating speed and positively with seed spacing. The average quality of feed index (QFI) at 0.1, 0.2, and 0.3 m seed spacing in bench tests was 88.38%, 96.67%, and 97.36%, with the average coefficient of variation (CV) being 20.13%, 16.27%, and 13.20%. Analysis of variance confirmed that both operating speed and seed spacing had a significant effect on QFI and CV (p &lt; 0.001). The analysis of motor rotational speed accuracy showed that the relative error of motor rotational speed above 410 rpm did not exceed 2.24%, and the relative error had less influence on the seeding quality. The average QFI was 85.93%, 95.91%, and 96.24%, with the average CV being 21.12%, 15.50%, and 16.49% at 0.1, 0.2, and 0.3 m seed spacing in field tests. The methods and results of this study can provide a reference for the design and optimization of the EDS in a maize precision seeder and provide an effective solution for the improvement of maize yields.

A LiDAR-depth camera information fusion method for human robot collaboration environment

With the evolution of human–robot collaboration in advanced manufacturing, multisensor integration has increasingly become a critical component for ensuring safety during human–robot interactions. Given the disparities in range scales, densities, and arrangement patterns among multisensor data, such as that from depth cameras and LiDAR, accurately fusing information from multiple sources has emerged as a pressing need to safeguard human–robot safety. This paper focuses on LiDAR and depth cameras, addressing the challenges posed by the differences in data collection range, point density, and distribution patterns which complicate information fusion. We propose a heterogeneous sensor information fusion method for human–robot collaborative environments. To solve the problem of substantial differences in point cloud range scales, a moving sphere space coarse localization algorithm is introduced, narrowing down the scale of interest based on similar features. Furthermore, to address the challenge of significant density differences and low overlap rates between point clouds, we present an improved FPFH coarse registration algorithm based on overlap ratio and an enhanced ICP fine registration algorithm based on the generation of corresponding points. The method proposed herein is applied to the fusion of information from a 64-line LiDAR and a depth camera within a human–robot collaboration scene. Experimental results demonstrate an absolute translational accuracy of 4.29 cm and an absolute rotational accuracy of 0.006 rad, meeting the requirements for heterogeneous sensor information fusion in the context of human–robot collaboration.

Acquired angle error correction based on variation of an angle detection signal intensity in rotary encoders

Abstract Rotary encoders are used in various machines to measure the angular position of a rotating axis. Therefore, rotary encoders are required not only to be highly accurate, but also usable in various environments. When using a rotary encoder on a machine, angle errors occur due to eccentricity between the encoder and the machine, the deformation of the scale, and the shaft runout of a rotation axis. Various methods have been adopted to reduce such angle errors. However, these methods have problems such as the large size and high cost of the rotary encoder, the necessity of additional devices for measuring, and increasing installation labor, so the environment in which they can be implemented is limited. In this study, we have proposed a method to correct the angle errors based on variation of an angle detection signal intensity in the sensor head. This method can correct the errors on machine without using multiple sensor heads or separate devices. The angle error estimated by this method is compared with that measured by the external equipment of a reference encoder. While the maximum angle error was 28.36” without correction, the residual error with correction can be reduced to 1.75” or less. From this result, the proposed method can improve the measurement accuracy of the rotary encoder already installed on the machine. Therefore, this method is an effective means for achieving both high rotational accuracy on machines and ease of correcting an error in rotary encoders to the machines.

Optimum error design and 5-axis CNC machining of preloaded roller-gear-cam in roller-drive system

Roller-gear-cam (RG-cam) drive systems in machine tool rotary tables provide enhanced rotation accuracy and superior transmission efficiency due to their preloaded design. However, achieving a controllable preload engagement between the roller and RG-cam requires the use of 5-axis CNC machining using a non-formed tool, which inevitably introduces machining errors. Accordingly, this study proposes a comprehensive method for the design, analysis, and manufacture of a precision RG-cam system on a conventional 5-axis CNC machine tool. Notably, the proposed method enables the machining errors to be controlled and minimized. The feasibility of the proposed approach is demonstrated by machining a prototype roller-drive system on a 5-axis CNC machine. The accuracy of the machined RG-cam is evaluated in accordance with the ISO 230-2 standard. It is shown that the forward and reverse rotational errors of the RG-cam over a single revolution are less than 10 s.

The Solar Aspect System of the Hard X-ray Imager Onboard ASO-S

The ASO-S/HXI is a bi-grids modulating instrument for solar hard X-ray imaging, whose collimator contains 91 pairs of tungsten grids. Since the solar disk is invisible in hard X-rays, a Solar Aspect System (SAS) is required to provide the pointing of hard X-ray imager (HXI) for locating X-ray sources on the solar disk. In addition, the knowledge of the alignment and relative twist of the corresponding front–rear grid pairs is important for image reconstruction as well as locating flares. Therefore, the SAS system was designed to monitor the alignment status of HXI grids and to provide the pointing direction of the HXI collimator with two subsystems DM and SA during the whole life cycle of HXI. DM measures the centroids of the front frosted glasses and the solar disk. SA images the Sun and provides precise relative locations of the solar disk center. Both work in the visible light of 565–585 nm. With all the data together, we can solve with an inversion algorithm the alignment status of the front and rear grids, the relative twist, and the pointing direction. We tested and validated the SAS design with both the simulation model and ground coordinate measuring machine. Here we present the detailed system design, the testing results, the inversion algorithm, and the in-orbit status of the SAS. Currently, the SAS has realized the rotational measurement accuracy of about 4 arcsec, and a translational measurement accuracy of about 15 μm, and the SAS pointing data has been used in both imaging calibration for flare locations and imaging corrections for the platform drifting effect. The high-cadence precise measurement (better than 0.3 arcsec) of the pointing will allow the study of source locations at different energies and therefore help us to understand electron acceleration and transportation in flares.

Research on positioning accuracy of the swivel head of milling and turning complex machining center

Abstract This article focuses on the swivel head of a milling-turning complex machining center and establishes a geometric error model between the rotary axes based on the multi-body system theory and the homogeneous coordinate transformation method. The double ball bar (DBB) is used to identify the geometric errors of the machine tool swivel head position-independent by measuring circular trajectories. The impact of PIGEs on the measurement trajectory is simulated. The swivel head is rotated at four angles (B0°, B45°, B90°, B-15°), and the laser tracker is used to analyze and study the linear axis straightness, perpendicularity, and the center coordinates and plane errors of the swivel head movement along the XZ plane. A swivel head rotation accuracy test fixture is designed to correct the positioning accuracy of a swivel head with a 45° inclination of the rotation axis. The research results show that the fluctuation of the center plane degree of freedom of the swivel head moving along the XZ plane is small, and the maximum value is 0.0086mm. Under the 45° angle posture of the swivel head, both the center coordinate error value and the plane error value are the largest. The simulation results of the swivel head position error are fairly consistent with the center coordinate error of the swivel head plane movement. A backward tilt displacement of 0.01mm~0.015mm of the machine column during assembly can reduce the influence of the weight of the swivel head on the perpendicularity and straightness of the vertical reciprocating motion, and adding auxiliary support near the base of the swivel head zero position can reduce machine straightness error.

Accuracy of clear aligners in the orthodontic rotational movement using different attachment configurations.

To evaluate the accuracy of dental rotational movements using clear aligners with different attachment configurations. This retrospective study analysed 212 teeth from 89 patients undergoing Invisalign treatment. Digital models were analysed after the virtual treatment plan (ST1) and after the first treatment phase (ET1) to evaluate the effective clinical rotational movement. The rotational movements of incisors, canines, and bicuspids were measured using data from the Clincheck Movements Table. ST1 and ET1 were compared to determine the actual rotational movement achieved (ST1-ET1). The presence or absence of attachments (rectangular or optimized) on teeth was analysed. The accuracy of rotational movements among attachment types was compared using the Kruskal-Wallis test. Multiple linear regressions were conducted with accuracy as the dependent variable and tooth type, gender, and age as predictors. Optimized attachments had the highest median accuracy (70%), followed by rectangular (65%), and without attachment (63%), with no significant differences (p = .5). There were no significant differences across age groups, genders, or tooth types. Baseline accuracy was 68.62% (95% CI: 56.03-81.20, p < .001). Age was a significant predictor (estimate = -0.30, 95% CI: -0.58 - -0.03, p = .032), indicating decreased accuracy with increasing age. The model's R2 was 0.046, with an adjusted R2 of 0.003, indicating minimal variance explained. The addition of attachment configurations to clear aligners improves rotational accuracy, but not significantly. Further advancements in these configurations are needed to enhance the performance of the aligners.

Quantum Effects on Cosmic Scales as an Alternative to Dark Matter and Dark Energy

The spin-torsion theory is a gauge theory approach to gravity that expands upon Einstein’s general relativity (GR) by incorporating the spin of microparticles. In this study, we further develop the spin-torsion theory to examine spherically symmetric and static gravitational systems that involve free-falling macroscopic particles. We posit that the quantum spin of macroscopic matter becomes noteworthy at cosmic scales. We further assume that the Dirac spinor and Dirac equation adequately capture all essential physical characteristics of the particles and their associated processes. A crucial aspect of our approach involves substituting the constant mass in the Dirac equation with a scale function, allowing us to establish a connection between quantum effects and the scale of gravitational systems. This mechanism ensures that the quantum effect of macroscopic matter is scale-dependent and diminishes locally, a phenomenon not observed in microparticles. For any given matter density distribution, our theory predicts an additional quantum term, the quantum potential energy (QPE), within the mass expression. The QPE induces time dilation and distance contraction, and thus mimics a gravitational well. When applied to cosmology, our theory yields a static cosmological model. The QPE serves as a counterpart to the cosmological constant introduced by Einstein to balance gravity in his static cosmological model. The QPE also offers a plausible explanation for the origin of Hubble redshift (traditionally attributed to the universe’s expansion). The predicted luminosity distance–redshift relation aligns remarkably well with SNe Ia data from the cosmological sample of SNe Ia. In the context of galaxies, the QPE functions as the equivalent of dark matter. The predicted circular velocities align well with rotation curve data from the SPARC (Spitzer Photometry and Accurate Rotation Curves database) sample. Importantly, our conclusions in this paper are reached through a conventional approach, with the sole assumption of the quantum effects of macroscopic matter at large scales, without the need for additional modifications or assumptions.

Modeling and Rotation Control Strategy for Space Planar Flexible Robotic Arm Based on Fuzzy Adjustment and Disturbance Observer

In precise space operation tasks, the impact of disturbing torques on the space flexible robotic arm (SFRA) cannot be ignored. Besides, the slender structure of the SFRA is very likely to generate vibration of the robotic arm. These are all potential hidden dangers in space safety. To quantify the potential risk, an accurate dynamics model of the SFRA considering the disturbing torque is built by Lagrange principle and the assumed modal method (AMM). Moreover, the effects of the disturbing torque, modal order and nonlinear terms on the deformation accuracy of the SFRA are compared. It is observed that the simplified dynamics model with neglecting the nonlinear terms (NNTs) has a high model accuracy and be easily solved. Therefore, the NNTs simplified model is chosen for deriving the transfer function of the SFRA. The parameters of the PI controller are adjusted in real time based on fuzzy rules to reduce the tracking error in the SFRA. In addition, the disturbance observer is designed to observe and compensate of the disturbance torque in the SFRA. The control method of adjusting controller parameters with fuzzy rules based on the disturbance observer greatly improves the rotational control accuracy of the SFRA. Finally, the validity of aforementioned control strategy is confirmed by simulation analysis and experimental results.

Recent Patent on Diamond Grinding Wheel Dressing

Diamond grinding wheels, particularly the advanced single-layer brazed variants, are indispensable for efficiently machining hard materials such as ceramics. Effective dressing is crucial, as it optimizes the wheel's isotropy and rotational accuracy, thereby ensuring precise machining. The selection of dressing tools and the conditions under which they operate significantly influence wheel quality, impacting key factors including topography, sharpness, wear rate, grinding forces, temperatures, and the surface integrity of the machined part. Consequently, the development of costeffective, high-performance dressing devices is of paramount importance. Furthermore, to provide a comprehensive review of representative patents in diamond grinding wheel dressing and to analyze the unique features, advantages, and disadvantages of various diamond grinding wheel dressing methods. Differentiating by method, diamond grinding wheel dressing devices fall into mechanical, memorable, and compound categories. Each patent addresses traditional device drawbacks with unique innovations, highlighting technical gaps and development needs in respective fields. Contemporary research in diamond dressing technology predominantly revolves around optimizing mechanical dressing methodologies. This focus is complemented by pioneering advancements in the architectural design and performance augmentation of dressing apparatuses, aiming to elevate efficiency and precision in various industrial applications. Specialized dressing techniques have resulted in many superior devices that are now widely utilized. Modern dressing devices are characterized by their high accuracy, efficiency, and performance. The mechanical dressing method enjoys the broadest applicability, proving highly effective for dressing diamond grinding wheels. Specialized dressing methods, on the other hand, offer superior dressing effects and the distinct advantage of contactless operation, thereby extending the service life of diamond grinding wheels. The composite dressing approach, merging the best attributes of mechanical and specialized methods, presents significant potential. Though currently underrepresented in terms of available devices, this field is expected to see considerable development and expansion in the future.

Image reconstruction method based on wavelet fusion in electrical capacitance tomography with rotatable electrode sensor

In this paper, an image reconstruction method based on wavelet fusion in electrical capacitance tomography with a rotatable electrode sensor is proposed. This method can weaken the effect of the relative position distribution between the electrodes and the phantom object, thus improving the quality of the reconstructed image. To investigate the reliability of the proposed image reconstruction method, a new mechanical design of a rotatable 12-electrode sensor is introduced. The rotation of the 12-electrode sensor is accomplished by stepping motor and gear sets, which can easily change the measurement position of the electrodes. Five independent datasets of 66 capacitance measurements can be obtained by rotating the electrode sensor 4 times with an angle of 6°from the initial position. Then solving the inverse problem for each of the datasets, 5 reconstructed images are obtained. Finally, the wavelet fusion algorithm is used to fuse the reconstructed images. To verify the validity of the method, this paper evaluates the error case of rotational accuracy, the error case of measurement data and the case of real experiment, respectively. The experimental results indicate that the method can reduce the artifacts in the reconstructed images and improve the quality of the reconstructed images. Meanwhile, this processing method can enhance the shape and edge contour of the measured phantom.

Guided versus non-guided chin repositioning: a retrospective study on accuracy

Genioplasty is a widely used surgical approach to address chin deformities by performing an osteotomy on the inferior border of the mandible to allow for comprehensive repositioning of the chin. This study aimed to compare the accuracy of freehand chin repositioning with a guided technique that employed specialised surgical guides. For this retrospective study, data from 30 adult patients who underwent orthognathic surgery to correct dentofacial deformities were analysed. All patients underwent virtual planning before surgery, with half of them treated using freehand chin repositioning and the other half using the guided technique. The surgical outcomes were measured and compared with the virtual plan to assess the positional and rotational accuracy of the techniques. In terms of translational assessment, noteworthy values that exceeded clinically acceptable limits were observed only in sagittal movement in the freehand group (0.97 mm, interquartile range (IQR) 0.73–2.29 mm). Regarding rotational accuracy, both groups exhibited an IQR that surpassed acceptable limits for pitch (3.26°, IQR 2.06–5.20 for the guided group and 2.57°, IQR 1.63–4.24° for the freehand group). The Mann-Whitney test indicated no statistical differences between the groups in any translational or rotational assessment. In conclusion, although there was no statistical difference, the guided technique proved effective in achieving clinically acceptable accuracy in all positions and almost all rotations, displaying superior results in sagittal positioning compared with the freehand technique. To fully harness the advantages of guides and to guarantee accuracy in all rotations, we recommend further research involving guides made of more rigid materials, and customised implants.

Effect of balls’ quantities, preload and raceway diameters on rotation accuracy and vibration of rigid rotor-bearing system based on nonlinear dynamic model

The rotation accuracy and vibration of the bearing-rotor system are important evaluation indicators for the working accuracy of machine tools. In this work, an innovative nonlinear dynamic model of the ball bearing-rotor system is first developed by considering the slip, spin and gyroscopic effects of ball and the whirl motion of cage. Secondly, this developed model is validated through experimental methods. On this basis, the coordination of balls' quantities and preload is studied to obtain the desired rotation accuracy and vibration of rotor. The effect of raceway diameters on the rotation accuracy and vibration of rotor is investigated. The influence mechanism of the odd and even number of balls in the left and right bearings on the rotation accuracy and vibration is revealed. The analyzed results illustrate that the reasonable contact load of the ball by adjusting the preload of the bearing-rotor system or the balls’ quantity can prompt good rotation accuracy and low vibration of rotor, here, the maximum contact loads of 65 N should be adopted in the left and right bearings to select the preload. Additionally, odd or even balls assembled in the left and right bearings synchronously are conducive to obtaining a favorable trajectory and rotating accuracy of rotor.