Changes In Relative Position Research Articles

Development of an X-ray ionization beam position monitor for PAL-XFEL soft X-rays.

The Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL) operates hard X-ray and soft X-ray beamlines for conducting scientific experiments providing intense ultrashort X-ray pulses based on the self-amplified spontaneous emission (SASE) process. The X-ray free-electron laser is characterized by strong pulse-to-pulse fluctuations resulting from the SASE process. Therefore, online photon diagnostics are very important for rigorous measurements. The concept of photo-absorption and emission using solid materials is seldom considered in soft X-ray beamline diagnostics. Instead, gas monitoring detectors, which utilize the photo-ionization of noble gas, are employed for monitoring the beam intensity. To track the beam position at the soft X-ray beamline in addition to those intensity monitors, an X-ray ionization beam position monitor (XIBPM) has been developed and characterized at the soft X-ray beamline of PAL-XFEL. The XIBPM utilizes ionization of either the residual gas in an ultra-high-vacuum environment or injected krypton gas, along with a microchannel plate with phosphor. The XIBPM was tested separately for monitoring horizontal and vertical beam positions, confirming the feasibility of tracking relative changes in beam position both on average and down to single-shot measurements. This paper presents the basic structure and test results of the newly developed non-invasive XIBPM.

Dynamic target feature selection in pixel change space for array GM-APD lidar

For detecting dynamic targets, the relative position change between the target and array GM-APD lidar significantly affects the stability and the classification ability of the extracted features, thereby affecting the target classification and recognition. In this paper, a feature selection algorithm is proposed that maps features to the space of the calculated average number of pixel changes to enhance the classification ability of features. Divide the feature data according to different scales in this space to keep the target feature values close in each window, thereby reducing the feature instability caused by motion. At the same time, establish the loss function in each window considering the importance and relevance of features and the number of selected features. Use particle swarm optimization to adaptively select the optimal feature subset and determine the optimal window scale. The experimental results show that the proposed mean of peak ratio of the decomposition waveform feature shows significant classification ability and stability in dynamic target classification. The classification accuracy is significantly improved when dealing with different dynamic vehicle scenes using the feature subset selected by the proposed algorithm. Compared with the undivided window, the classification accuracy is improved by 9.1 %–53.1 %, and compared with the division time window, the classification accuracy is improved by 5.7 %–18.8 %. This study provides robust technical support for dynamic target classification and recognition.

Manual Acupuncture Manipulation Recognition Method via Interactive Fusion of Spatial Multiscale Motion Features

Manual acupuncture manipulation (MAM) is essential in traditional Chinese medicine treatment. MAM action recognition is important for junior acupuncturists’ training and education; however, there are obvious personalized differences in hand gestures among expert acupuncturists for the same type of MAM. In addition, during the MAM operations, the magnitude and frequency of the expert acupuncturists’ hand shape and relative needle-holding finger position changes are tiny and fast, resulting in difficulties in observing MAM action details. Thus, we propose a Spatial Multiscale Interactive Fusion MAM Recognition Network to solve the difficulties in MAM recognition. First, this paper presents an optical flow-based hand motion contour global feature extraction method for acupuncture hand shape. Second, to explore the motion rule between the needle-holding fingers during the MAM operations, we design a quantitative description method of the relative motion of the needle-holding fingers: an “interactive attention module,” which achieves feature fusion and mines the correlation between different scales of MAM action features. Finally, the proposed MAM recognition method was validated by 20 acupuncturists from the Beijing University of Traditional Chinese Medicine and 10 from the Beijing Zhongguancun Hospital who participated in the MAM video signal collection. The proposed recognition method achieves the highest average validation accuracy of 95.3% and the highest test accuracy of 96.0% for four typical MAMs, proving its feasibility and effectiveness.

Late Holocene changes in the water table at an alkaline fen in Central Latvia: Their impacts on CaCO3 deposition at the fen and relation to the hydroclimate patterns of the Eastern Baltic Region

Sediments of CaCO3-precipitating alkaline fens, comprising biotic and abiotic indicators of water table changes, are among the most reliable archives for obtaining palaeohydrological data. The study uses a semiquantitative method based on a combination of selected indicators (plant macrofossils, mollusc shells, degree of peat decomposition) to estimate the relative changes in the water table position at Lustūžkalns alkaline fen, Latvia, Eastern Baltic Region. The study also aims to determine the time frames of CaCO3 deposition at the fen using loss on ignition and carbon and oxygen stable isotope records. The chronology of the three sediment sequences studied is based on the AMS radiocarbon dating of terrestrial plant macrofossils. Although the reconstructed water table positions revealed differences between the cores, the major shift from the low water tables persisting since ca. 5000 cal yr BP to the prevailing high water stands at ca. 3000 cal yr BP was common to all the sequences. The major shift observed is consistent with a change from low to high water tables in peatlands in Latvia and at numerous fens and bogs across the Eastern Baltic Region, Fennoscandia and NW Europe. Concurrent with the increase in the water tables was the onset of CaCO3 precipitation on the Lustūžkalns fen surface, which began at ca. 3000 cal yr BP and accelerated from ca. 2500 cal yr BP. The Late Holocene CaCO3 precipitation at Lustūžkalns can be attributed to the change from warm and dry conditions during the Holocene Thermal Maximum (HTM) to cooler but humid during the Late Holocene. In contrast, in Central and Western Europe, the main period of freshwater carbonate precipitation occurred during the warm and humid HTM.

Integrated Analysis of Line-Of-Sight Stability of Off-Axis Three-Mirror Optical System

As a space camera works in orbit, the stress rebound caused by gravity inevitably results in the deformation of its optomechanical structure, and the relative position change between different optical components will affect the Line-Of-Sight pointing of the camera. In this paper, the optical sensitivity calculation of a space camera’s Line-Of-Sight pointing is realized based on the optomechanical constraint equations, and the Line-Of-Sight equations are constructed using the second type of response (DRESP2) method to realize an optomechanical integrated analysis of the camera’s Line-Of-Sight stability at the structural finite element solver level. The verification results show that the Line-Of-Sight stability error is 6.38%, meaning that this method can identify the sensitive optical elements of the optical system efficiently and quickly. Thus, the method in this paper has important significance as a reference for the analysis of the Line-Of-Sight stability of complex optical systems.

Analysis of strength characteristics of loess before and after freezing using a hollow cylinder torsional shear apparatus

This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development. In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle (α) reduces the strength of the generalized shear stress and shear strain curves. Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient (b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.

Comparative study on interactions of phillyrin and phillygenol with lysozyme: Spectroscopy, differential scanning calorimetry and molecular modeling approaches

Phillyrin (PR) and its derivative phillygenol (PG) are major active extracts of the Chinese medicine Forsythiae Fructus. Lysozyme, an important carrier protein, has a variety of physiological along with pharmaceutical functions. Herein, the interactions of PR and PG with hen egg white lysozyme (HEWL) are investigated in details by spectroscopic analyses, differential scanning calorimetry (DSC) tests, and molecular modeling approaches. Fluorescence measurement and UV–visible absorption difference spectroscopy reveal that an “untypical static quenching” takes place pointing towards the formation of ground state complex. The binding constants of HEWL-PG are greater than that of HEWL-PR. Moreover, the major driving force for the binding process is elucidated as hydrophobic interactions for both cases. Circular dichroism spectroscopy and three-dimensional fluorescence indicate that PR and PG decrease the helical structure of the HEWL and hydrophobicity surrounding Trp and Tyr residues. The thermal stability of HEWL decreases in the presence of PR and PG by DSC. Docking study infers that both PR and PG could bind to the hydrophobic cavity of HEWL and supports the higher binding of PG than PR. Molecular dynamics study illustrates that PR has higher relative position change, which may attribute to its lower binding ability. In terms of the radius of gyration (Rg), PG causes the protein structure to swell even more. The average hydrogen bonds number of HEWL-PG is less than that of HEWL-PR and more changes of the residual fluctuation are observed in HEWL-PG system. Furthermore, MM-PBSA analysis exhibits that HEWL-PG has lower binding energy. Collectively, these results support that both PR and PG could bind to HEWL, but PG possesses higher affinity which leads to stronger secondary structural changes of HEWL than PR. These findings are beneficial to comprehensively understand the binding characteristic of PR and PG with HEWL, providing experimental basis for pharmacokenitics of PR and PG.

An Orientation-Aware Attention Network for Person Re-Identification

Humans always identify persons through their characteristics, salient attributes, and these attributes’ locations on the body. Most person re-identification methods focus on global and local features corresponding to the former two discriminations, cropping person images into horizontal strips to obtain coarse locations of body parts. However, discriminative clues corresponding to location differences cannot be discovered, so persons with similar appearances are often confused because of their alike components. To address the above problem, we introduce pixel-wise relative positions for the invariance of their orientations in viewpoint changes. To cope with the scale change of relative position, we combine relative positions with self-attention modules that perform on multi-level features. Moreover, in the data augmentation stage, mirrored images are given new labels due to the conversion of the relative position along a horizontal orientation and change in visual chirality. Extensive experiments on four challenging benchmarks demonstrate that the proposed approach shows its superiority and effectiveness in discovering discriminating features.

Modification of Woven Endo-Bridge After Intracranial Aneurysm Treatment: A Methodology for Three-Dimensional Analysis of Shape and Relative Position Changes.

During follow-up of patients treated with WEB devices, shape changes have been observed. The quantitative three-dimensional measurement of the WEB shape modification (WSM) would offer useful information to be studied in association with the anatomical results and try to better understand mechanisms implicated in this modification phenomenon. We present a methodology to quantify the morphology and position of the WEB device in relation to the vascular anatomy. Three-dimensional rotational angiography (3DRA) images of seven aneurysms patients treated with WEBs were used, which also accompanied by a post-treatment 3DRA image and a follow-up 3DRA image. The device was manually segmented, obtaining the 3D models after treatment and at the follow-up. Volume, surface area, height, maximum diameter and WSM ratio of both surfaces were calculated. Position changes were evaluated measuring WEB axis and relative position between post-treatment and follow-up. Changes in WEB volume and surface area were observed with a mean modification of and , respectively. The positional variables also showed differences, mean change of device axis direction was and mean change of distance was . Inter-observer and intra-observer variability analyses did not show differences (ANOVA ). This methodology allows quantifying the morphological and position changes suffered by the WEB device after treatment, offering new information to be studied in relation to the occurrence of WEB shape modification.

Thermal Error Measurement and Compensation with Torque Limit Skip in Swiss-type Lathe Manufacturing

This paper presents a new methodology for the measurement of thermal errors of Swiss-type lathes. The basis of the proposed method is the torque limit skip function integrated in the lathe’s control which stops the motion of a linear axis if the torque on the corresponding axis servo is exceeded. The skip signal is triggered via a slow contact between a bar in the lathe’s spindle and an artefact in the lathe’s tool holder. Experimental results indicate that when a sufficiently low torque override limit is applied, the axis positioning repeatability under the repeated application of the torque limit skip is within ±1μm. The relative change in position of the axis after the skip measured over several hours is the thermal error which can be compensated. The proposed measurement technique offers significant advantages over conventional thermal error measurement with a touch-trigger probe or linear displacement sensors: if available on the machine’s control, it does not require any specialized installation, can be used during production, and delivers comparable results without high additional equipment costs.

Multi-ensemble metrology by programming local rotations with atom movements

Current optical atomic clocks do not utilize their resources optimally. In particular, an exponential gain in sensitivity could be achieved if multiple atomic ensembles were to be controlled or read out individually, even without entanglement. However, controlling optical transitions locally remains an outstanding challenge for neutral-atom-based clocks and quantum computing platforms. Here we show arbitrary, single-site addressing for an optical transition via sub-wavelength controlled moves of atoms trapped in tweezers. The scheme is highly robust as it relies only on the relative position changes of tweezers and requires no additional addressing beams. Using this technique, we implement single-shot, dual-quadrature readout of Ramsey interferometry using two atomic ensembles simultaneously, and show an enhancement of the usable interrogation time at a given phase-slip error probability. Finally, we program a sequence that performs local dynamical decoupling during Ramsey evolution to evolve three ensembles with variable phase sensitivities, a key ingredient of optimal clock interrogation. Our results demonstrate the potential of fully programmable quantum optical clocks even without entanglement and could be combined with metrologically useful entangled states in the future.

ChirpTracker: A Precise-Location-Aware System for Acoustic Tag Using Single Smartphone

The increasing interest in loss prevention devices using the Internet of Things, has been driven by the convenience, low cost, and low power consumption of these devices. However, the existing technologies cannot achieve a balance between high availability over a wide area with a single smartphone and precise location awareness. In this paper, a novel Precise-Location-Aware method that integrates acoustic technology and pedestrian dead reckoning, ChirpTracker, is proposed which most smartphones support without auxiliary equipment. This system can provide wide coverage (30m) and is suitable for many scenarios such as searching for cars in underground parking or finding items indoors. ChirpTracker can detect the distance between the smartphone and a lost tag in real time using acoustic signals, it can monitor the relative position change of the smartphone based on deep learning based pedestrian dead reckoning (PDR) and update relative positioning of the lost tag though the observation from single base-station in motion. A technology that combines the local least squares method (LSM) and particle filter (PF) improves the convergence and the robustness of ChirpTracker through an identification strategy for a mirror position. This method was validated in experiments conducted in actual environments. The results demonstrate the effectiveness and positioning accuracy of ChirpTracker.

Monitoring of structures with bearing elements in the form of long vertical rods

A building structure is considered, which in the design form consists of two vertical rectilinear interacting elements. One of them is loading, the other is carrying. The bearing element is presented in the form of a long thin rod loaded with an external axial vertical force. Due to the errors of geodetic verification and installation work, the bearing rod will be installed with some inclination and displacement relative to the coordinate axes. The external load on the bearing element is represented by the force vector, which is equivalent to the loading rod. Errors of geodetic verification and installation work will change the design direction of the force line and its design position on the supporting element. An inclined force vector will have a vertical and horizontal force component. Thus, the line of action of the loading force and the longitudinal axis of the supporting rod will be located at an angle to each other, which will cause bending momentsand transverse forces in the sections of the rod. A design "changed" in relation to the project is created. Bending moments and horizontal forces in this design will contribute to premature bending of the rod. An unevenly heated rod also acquires the ability to distort. The influence of the specified factors can be increased, and the stability of the rod significantly weakened due to uneven subsidence, horizontal displacement or tilting of the supporting structure due to dangerous exogenous geological processes. Therefore, errors in the position of elements, changes in temperature, geological processes disrupt the linear form of equilibrium of the bearing rod and its position in space. The change in shape and relative position contributes to the premature emergence of an unstable state under an increasing external load. In the changed design, the bearing rod may suddenly find itself in a critical stress-deformed state. The task of monitoring is to sense and properly record changes and dynamics of the stress-strain state. For this purpose, measuring complexes with a certain configuration are designed, which provide with the necessary specified accuracy the measurement of changes in the physical state of the elements of building structures.

Research on cone-beam CT of mandibular foramen location in children aged 7-10 years

Objective: Cone-beam CT (CBCT) images were used to investigate the relative position changes of mandibular foramen in the mandible of children and the relative position relationship with the occlusal plane, so as to provide clinical guidance for inferior alveolar nerve block (IANB) anesthesia of children. Methods: The CBCT data of 202 children aged 7-10 years in the image database of the First Affiliated Hospital of Zhengzhou University from March 2021 to February 2023 were included. Patients were divided into 4 groups according to age diffrences as 7-year-old, 8-year-old, 9-year-old and 10-year-old. There were 20 males and 22 females in the 7-year-old group, 31 males and 28 females in the 8-year-old group, 30 males and 26 females in the 9-year-old group, and 22 males and 23 females in the 10-year-old group, respectively. Forty-six adults aged 25-30 years were selected as control group, 24 males and 22 females included. The distance between the center point of mandibular foramen with the anterior edge of ascending ramus of mandible (MF-A), the posterior edge of the ascending ramus of mandible (MF-P) and the shortest distance between the center point of mandibular foramen with occlusal plane (MF-OP) were measured. The angle between the center point of the mandibular foramen with the sagittal plane of the mandibular first deciduous molar (or mandibular first premolar) and mandibular second deciduous molar (or mandibular second premolar) (∠A) was measured. The data of mandibular foramen were compared between the left and right sides and among different genders and different age groups. Results: The position of mandibular foramen in children aged 7-10 years maintained bilateral symmetry, and mandibular growth and development were relatively consistent between different genders (P>0.05). MF-A increased with age, from (15.83±1.28) mm in 7-year-old group to (17.10±1.60) mm in 10-year-old group gradually. There were significant differences in MF-A between the 10-year-old group with the 7-year-old group, the 8-year-old group [(15.98±1.53) mm] and the 9-year-old group [(16.43±1.49) mm] respectively (P<0.05). MF-P increased with age, from (9.12±1.17) mm in 7-year-old group to (11.25±1.60) mm in 10-year-old group. There were statistically significant differences in MF-P among all age groups (P<0.05). MF-OP increased with age, from below the plane (-0.24±2.31) mm in the 7-year-old group to above the plane (1.08±1.95) mm in the 10-year-old group. There were significant differences between the 10-year-old group with the 7-year-old group, the 8-year-old group [(-0.01±1.93) mm], and the 9-year-old group [(0.31±1.95) mm] (P<0.05). The ratio of MF-A to MF-P decreased as the age increased, from 1.77±0.30 in the 7-year-old group to 1.55±0.29 in the 10-year-old group. There were statistically significant differences in MF-A/MF-P among all age groups (P<0.05), except for between the 8-year-old group (1.66±0.19) and the 9-year-old group (1.65±0.28) (P>0.05). The ∠A of children in all age groups was significantly greater than the reference value (45°) (P<0.05), and there was no statistical significance among all groups (P>0.05). The differences of MF-A, MF-P, MF-OP, MF-A/MF-P and ∠A between children of all age groups and the control group were statistically significant (P<0.05). Conclusions: In children aged 7-10 years, the mandibular foramen is located behind the midpoint of the anteroposterior diameter of the mandibular ramus. With the increase of age, the mandibular foramen gradually moves from below the occlusal plane to above, and is flush with the occlusal plane at the age of 8 years. Compared with adults, the mandibular foramen in children is more backward and lower on the medial side of the mandibular ramus. When IANB is operated to children, the syringe can be moved distally from the contact area of the contralateral deciduous molars or premolars, so that the injection angle can be greater than the reference value 45° to improve the accuracy of IANB.

Analysis of Grating Lobe Effects on GEO DSC Distributed Antennas

Traditional single-antenna systems have inherent limitations in terms of antenna gain, anti-interference capability, and flexibility. To overcome these challenges, satellite-mounted distributed antenna systems disperse multiple antennas at different positions on the satellite to improve the reception quality and signal-to-noise ratio of satellite signals, enhancing the performance of the satellite communication system without additional bandwidth or transmission power. However, the dispersed locations and long distances between antennas on the satellite result in less compact spacing compared to terrestrial distributed antennas, leading to the generation of a significant number of grating lobes. The distributed satellite cluster (DSC) approach revolutionizes the traditional mode of satellite utilization, enabling close collaboration among distributed loads. In this study, we analyzed the impact of grating lobes produced by DSC distributed antennas in geostationary Earth orbit (GEO) and simulated the grating lobe patterns of two 1 m circular aperture satellite antenna arrays in GEO. The simulation results revealed that the relative position change of the satellites affected the width and number of interference fringes in a certain ground area, while change in the carrier phase led to the translation of the interference fringes. To mitigate the grating lobes, we employed a sparse array technique. The simulation results demonstrated that the sparse array effectively suppressed the grating lobes but at the expense of a decrease in the sidelobe level and beamwidth.

Wavelet transform coupled with Fischer plots for sequence stratigraphy: A case study in the Linxing area, Ordos Basin, China

Accurately dividing stratigraphic sequence using traditional data such as core and logging data is challenging due to the insufficient availability of paleontological fossils and rock data, particularly in Carboniferous-Permian strata of the Linxing area of Ordos Basin, dominated by lagoons, barrier islands, and tidal flat sedimentation. This drawback hinders the exploration and exploitation of hydrocarbon reservoirs. To address this issue, this study presents a combination of continuous wavelet transform (CWT) and Fischer plots, enabling the accurate identification of each level of sequence boundary and high-resolution sequence stratigraphic correlation. The optimal scale factors, 120, 60, and 20, are determined by applying different scale factors to gamma ray (GR) curves corresponding to long-term cycle, medium-term cycle, and short-term cycle divisions, respectively. The analysis of sequence characteristics of numerous core segments and the corresponding CWT results (i.e., wavelet coefficient curve and time-frequency energy spectrum) led to the identification of three main types of medium-term cycles (i.e., progradational, regressive, and aggradational) that were then applied to the entire well section of the study area. Moreover, the Fischer plots method was used to identify the long-term cycle based on the determination of medium-term cycles and the division of short-term cycles. This method provided intuitive identification of the relative changes in sea level position. Additionally, the characteristics of sea level changes were consistent with the results of the sea level analysis of rock and logging curves. Therefore, the combination of CWT and Fischer plots can effectively and comprehensively establish an isochronous stratigraphic framework for clastic rock hydrocarbon reservoirs, similar to this study.

Flexible printed electrically small microwave resonator for automated displacement tracking

In this paper, a planar split ring resonator-based flexible RF sensor is developed for linear and rotational position tracking of a target object. The proposed sensing scheme employs a 100 μm thin flexible printed resonator that facilitates ease of adherence to a target object than that of the conventional RF sensor. The realized printed resonator is excited by a near-field proximity coupling mechanism using a standard 50 Ω microstrip line. A detailed numerical analysis for the linear and rotational displacement of several dummy targets is carried out by recording the change in measured parameters corresponding to the relative change in position of the printed resonator attached to a dummy target under test. Afterward, the equivalent circuit and fabricated prototype of a printed flexible sensor is developed and tested for the linear and rotational displacement of several target materials under observation and an ANN model is developed to curb the uncertainty.

Largest Lyapunov exponent as a tool for detecting relative changes in the particle positions.

Dynamics of the driven Frenkel-Kontorova model with asymmetric deformable substrate potential is examined by analyzing response function, the largest Lyapunov exponent, and Poincaré sectionsfor two neighboring particles. The obtained results show that the largest Lyapunov exponent, besides being used for investigating integral quantities, can be used for detecting microchanges in chain configuration of both damped Frenkel-Kontorova model with inertial term and its strictly overdamped limit. Slight changes in relative positions of the particles are registered through jumps of the largest Lyapunov exponent in the pinning regime. The occurrence of such jumps is highly dependent on type of commensurate structure and deformation of substrate potential. The obtained results also show that the minimal force required to initiate collective motion of the chain is not dependent on the number of Lyapunov exponent jumps in the pinning regime. These jumps are also registered in the sliding regime, where they are a consequence of a more complex structure of largest Lyapunov exponent on the step.

Factor Graph Framework for Smartphone Indoor Localization: Integrating Data-Driven PDR and Wi-Fi RTT/RSS Ranging

The classic fusion localization techniques based on the Kalman filter (KF) framework have been a focus of research community in the past decades, due to the limited computing power of the mobile devices. However, with computing-efficient and sensor-rich smartphones now being a commonplace, it is convenient and meaningful to provide more accurate positioning services for smartphones in an indoor environment. In this paper, we design and develop a tightly coupled fusion platform of Wi-Fi RTT, RSS, and data-driven PDR based on factor graph optimization for locating the consumer-grade smartphones in indoor environment. As compared to the existing PDR solutions, including step model-based approaches and data-driven approaches, the proposed PDR solution with magnetic information constraint can track the relative position change of pedestrians at 20 Hz, while supporting multiple smartphone usage poses. A comprehensive comparison between factor graph optimization (FGO), KF frame and its variants is also performed. The experimental results demonstrate that the proposed fusion platform achieves an average positioning accuracy of 0.39 m. In addition, it also improves the accuracy of EFK and ARKF by 45.83% and 27.78%, respectively. The analysis shows that as the smartphone computing performance continues to improve, the FGO-based sensor fusion gradually replaces the KF frame and its variants.

Automatically Extracting Rubber Tree Stem Shape from Point Cloud Data Acquisition Using a B-Spline Fitting Program

Natural rubber is an important and strategic raw material, used in tires, gloves, and insulating products, that is mainly obtained by cutting the bark of rubber trees. However, the complex contour curve of the rubber tree trunk is hard to fit using a tapping machine. Thus, a trunk contour curve collection would be useful for the development of tapping machines. In this study, an acquisition system based on laser-ranging technology was proposed to collect the point cloud data of rubber tree trunks, and a B-spline fitting program was compiled in Matrix Laboratory (MATLAB) to extract the trunks’ contour curves. The acquisition system is composed of power, a controller, a driver, a laser range finder, and data transmission modules. An automatic extraction experiment on the contour curves of rubber tree trunks was carried out to verify the feasibility and accuracy of using the acquisition system. The results showed that the degree of rubber tree trunk characteristic recognition reached 94.67%, which means that the successful extraction of the rubber tree trunk contour curves and the B-spline fitting program are suitable for the extraction of irregular curves of rubber tree trunks. The coefficient of variation of repeated collection was 0.04%, which indicates that changes in relative positions and acquisition directions have little influence on the extraction and the accuracy of the acquisition system, which are high and stable. Therefore, it was unnecessary to adjust the position of the acquisition device before the collecting process, which helped to improve the efficiency of acquisition considerably. The acquisition system proposed in this study is meaningful to the practical production and application of agroforestry and can not only improve the precision of the rubber tapping process by combining with an automatic rubber tapping machine but can also provide technical support for the prediction of rubber wood volume and the development of ring-cutting equipment for other fruit trees.