Background
The fixture thread depth reportedly influences the primary stability of dental implant, but its effect on the positional accuracy in immediate implant placement has not been reported ...previously.
Materials and Methods
Fifty‐six single‐rooted, anterior and premolar teeth were extracted from six human cadavers, followed by installing either regular‐threaded implants (RT group, N = 30) or deep‐threaded implants (DT group, N = 26) completely relying on the surgical guide. Optical impressions taken after osteotomy and fixture installation were superimposed with the preoperative virtual planning data to measure the vertical, angular, platform and apex deviations that occurred during osteotomy and installation.
Results
While the osteotomy deviations were similar between the two groups, the angular and apex deviation of the DT group (2.67 ± 2.56°; 1.04 ± 0.49 mm, respectively) were significantly larger than those of the RT group (1.61 ± 1.04°; 0.67 ± 0.41 mm, respectively) during installation (p < .05). When the installation deviations were analysed in the anterior and premolar areas separately, the angular, platform and apex deviations of the DT group (3.05 ± 3.26°; 0.75 ± 0.32 mm; 1.08 ± 0.56 mm, respectively) were significantly larger than those of the RT group (1.56 ± 0.73°, 0.59 ± 0.28 mm; 0.62 ± 0.38 mm, respectively) in the anterior site (p < .05), whereas there was no significant intergroup difference in the premolar site.
Conclusion
In immediate‐implant surgery, using an implant with a deeper thread might increase the deviations during installation, especially in the anterior area.
It is essential to improve the absolute position accuracy of industrial robot milling systems. In this paper, a method based on an incremental extreme learning machine model (IELM) is proposed to ...improve the positioning accuracy of the robot. An extreme learning machine optimized by the improved sparrow search algorithm (ISSA) to predict the positioning errors of an industrial robot. The predicted errors are used to achieve compensation for the target points in the robot's workspace. The IELM model has good fitting and predictive power and can be fine-tuned by adding fewer samples. Combined with an offline feed-forward compensation method, the solution was validated on the milling industrial robot KUKA KR160. The method has been validated on a KUKA KR160 industrial robot, and experimental results show that after compensation; the absolute positioning error of the milling robot is improved by 86%, from 1.074 to 0.154 mm. After fine-tuning the industrial robot’s error prediction model using a small number of measurement points once the robot had moved to a new machining position, experimental results showed that the average absolute positioning error of the robot’s end-effector was reduced by 70.76%, from 1.71 before compensation to 0.5 mm after compensation.
In this study, the effect of the height difference, geometry, and number of GCPs on the positional accuracy of point cloud was investigated in UAV photogrammetry. It has been determined that the ...topographic change of the study area, the geometric structure of GCPs, and the distance between GCPs are the most important factors in GCP network design. It was observed that the GCP network design is more important than the number of GCPs in the UAV Photogrammetry method to increase the positional accuracy.
Robot geometrical calibration aims at reducing the global positioning accuracy of a robotic arm by correcting the theoretical values of the kinematic parameters. A novel method for the geometrical ...calibration of robotic arms used in industrial applications is proposed. The proposed approach mainly focuses on the final positional accuracy of the robotic tool center point (TCP) when executing an industrial task rather than on the accurate estimation of the kinematic parameters themselves, as done so far by many calibration methods widely discussed in literature. A real industrial use-case is presented, and the steps of the proposed calibration procedure for the robotic arm are described. Experimental methodology and results for the identification of geometrical parameters are also discussed. A practical validation of the final positional accuracy of the robotic arm (after kinematic calibration) was performed, and experimental results validated the proposed procedure, proving its feasibility and effectiveness in the considered industrial scenario.
The circular Rogowski coil with a rectangular section is the most common and basic measuring unit of current. However, in some situations, a noncircular Rogowski coil is more suitable because of the ...limited space to be embedded in and the demand for decreasing the size of the Rogowski coil. Circular Rogowski coil is usually wound uniformly to guarantee the positional accuracy and anti-interference ability considering the very good symmetry. However, for noncircular Rogowski coil, the turns arrangement is usually designed based on experience due to the lack of theoretic direction. This article first proposed a method of turns arrangement of the noncircular Rogowski coil with a rectangular section, which the positional accuracy and anti-interference ability can be achieved at the same time. By establishing the equivalent relation between mutual inductance and electric potential, the turns density of the noncircular Rogowski coil can be acquired by solving the charge density on its equivalent electrodes. The turns density is proven to be unique. For a given turn number, the turns arrangement of the noncircular Rogowski coil can be obtained by discretizing the turns density. As an example of the method, a square Rogowski coil, which can be used in chip current measurement in Press Pack insulated gate bipolar transistors (IGBTs), is particularly designed and contrasted with the traditional square Rogowski coil with turns equidistantly arranged to verify the great positional accuracy and anti-interference ability. The results of the calculation and experiment show that this method is very effective.
Google Earth now hosts high-resolution imagery that spans twenty percent of the Earth's landmass and more than a third of the human population. This contemporary highresolution archive represents a ...significant, rapidly expanding, cost-free and largely unexploited resource for scientific inquiry. To increase the scientific utility of this archive, we address horizontal positional accuracy (georegistration) by comparing Google Earth with Landsat GeoCover scenes over a global sample of 436 control points located in 109 cities worldwide. Landsat GeoCover is an orthorectified product with known absolute positional accuracy of less than 50 meters root-mean-squared error (RMSE). Relative to Landsat GeoCover, the 436 Google Earth control points have a positional accuracy of 39.7 meters RMSE (error magnitudes range from 0.4 to 171.6 meters). The control points derived from satellite imagery have an accuracy of 22.8 meters RMSE, which is significantly more accurate than the 48 control-points based on aerial photography (41.3 meters RMSE; t-test p-value < 0.01). The accuracy of control points in more-developed countries is 24.1 meters RMSE, which is significantly more accurate than the control points in developing countries (44.4 meters RMSE; t-test p-value < 0.01). These findings indicate that Google Earth highresolution imagery has a horizontal positional accuracy that is sufficient for assessing moderate-resolution remote sensing products across most of the world's peri-urban areas.
OpenStreetMap (OSM) is among the most prominent Volunteered Geographic Information (VGI) initiatives, aiming to create a freely accessible world map. Despite its success, the data quality of OSM ...remains variable. This study begins by identifying the quality metrics proposed by earlier research to assess the quality of OSM building footprints. It then evaluates the quality of OSM building data from 2018 and 2023 for five cities within Québec, Canada. The analysis reveals a significant quality improvement over time. In 2018, the completeness of OSM building footprints in the examined cities averaged around 5%, while by 2023, it had increased to approximately 35%. However, this improvement was not evenly distributed. For example, Shawinigan saw its completeness surge from 2% to 99%. The study also finds that OSM contributors were more likely to digitize larger buildings before smaller ones. Positional accuracy saw enhancement, with the average error shrinking from 3.7 m in 2018 to 2.3 m in 2023. The average distance measure suggests a modest increase in shape accuracy over the same period. Overall, while the quality of OSM building footprints has indeed improved, this study shows that the extent of the improvement varied significantly across different cities. Shawinigan experienced a substantial increase in data quality compared to its counterparts.
Precision object handling and manipulation require the accurate positioning of industrial robots. A common practice for performing end effector positioning is to read joint angles and use industrial ...robot forward kinematics (FKs). However, industrial robot FKs rely on the robot Denavit-Hartenberg (DH) parameter values, which include uncertainties. Sources of uncertainty associated with industrial robot FKs include mechanical wear, manufacturing and assembly tolerances, and robot calibration errors. It is therefore necessary to increase the accuracy of DH parameter values to reduce the impact of uncertainties on industrial robot FKs. In this paper, we use differential evolution, particle swarm optimization, an artificial bee colony, and a gravitational search algorithm to calibrate industrial robot DH parameters. A laser tracker system, Leica AT960-MR, is utilized to register accurate positional measurements. The nominal accuracy of this non-contact metrology equipment is less than 3 μm/m. Metaheuristic optimization approaches such as differential evolution, particle swarm optimization, an artificial bee colony and a gravitational search algorithm are used as optimization methods to perform the calibration using laser tracker position data. It is observed that, using the proposed approach with an artificial bee colony optimization algorithm, the accuracy of industrial robot FKs in terms of mean absolute errors of static and near-static motion over all three dimensions for the test data decreases from its measured value of 75.4 μm to 60.1 μm (a 20.3% improvement).
Debido a la popularidad de Google Earth, los usuarios suelen utilizar los datos geográficos de esta plataforma con fines científicos y para la planificación espacial. Sin embargo. Google afirma que ...estos datos son solo aproximaciones y, por lo tanto, su precisión posicionai no está documentada oficialmente. Ante la mejora en la obtención de estos datos surge la necesidad de evaluar la calidad del producto cartográfico. Este trabajo tiene como objetivo evaluar la calidad planimétrica de los datos puntuales obtenidos de Google Earth, con base en la estadística descriptiva, el análisis de tendencias y el Estándar Brasileño de Precisión Cartográfica (PEC-PCD). Para ello, se utilizaron como referencia dos ortofotos georreferenciadas con una resolución espacial de 5 cm, una de una zona urbana y otra de una zona rural del estado de Pernambuco en Brasil. En los resultados se encontró un error posicionai de 1,26 m en la zona urbana y de 4,65 m en la zona rural. Según el análisis PEC-PCD, los datos planimétricos generados por Google Earth cumplen con las especificaciones técnicas a escalas menores a 1:5000 en áreas densamente urbanizadas y 1:10000 en áreas no urbanizadas. Se observó que en lugares con mayor disponibilidad de imágenes satelitales de alta resolución se presenta una precisión significativa. Por lo tanto, Google Earth representa una fuente atractiva de datos posicionales que se pueden utilizar para análisis espaciales y estudios preliminares.
Tectonic plate motion affects coordinates resulting from GPS measurements and the referencing of aerial and satellite imagery. It therefore impacts the long-term use of global coordinate systems. ...Over time, the tectonic plates move relative to each other and coordinates become outdated. Most geographic datasets including OpenStreetMap are no exception, as these are affected in terms of a growing location–coordinate mismatch. Current research is aware of this issue but solution strategies have not been fully explored yet. In this manuscript, we discuss how regular systematic updates of coordinate values can be used to address this issue. We explore the recommended frequency to perform such updates for guaranteeing a minimal loss of accuracy after long periods of time. It is further determined how rounding errors impair such systematic updates and in which ways singular and irregular manual updates impede systematic solution strategies. The solution strategies proposed lead to minimal overall errors and thus guarantee to retain high positional accuracy of coordinate pairs within global datasets, even after years of existence.
•Urban datasets such as OpenStreetMap are affected by tectonic plate motion long-term.•The systematic strategy proposed to correct for tectonic effects minimizes overall error.•Singular updates of the data at irregular intervals are taken into account.•The overall positional error is symmetric with respect to the fraction of the data that is subject to irregular updates.
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