Surface Tracking Research Articles

PO-1590: Spirometer guided breathhold breast VMAT on Halcyon verified with portal images and surface tracking

PO-1590: Spirometer guided breathhold breast VMAT on Halcyon verified with portal images and surface tracking

PO-1340: Optical surface tracking for non-coplanar SRS treatments verified by film in a RandoAlderson phantom

PO-1340: Optical surface tracking for non-coplanar SRS treatments verified by film in a RandoAlderson phantom

PO-1916: Applications of the Medusa surface tracking system for respiratory control in breast cancer patients

PO-1916: Applications of the Medusa surface tracking system for respiratory control in breast cancer patients

PO-1599: Implementation of a commercial optical surface tracking system for non-coplanar SRS treatments

PO-1599: Implementation of a commercial optical surface tracking system for non-coplanar SRS treatments

Breath Hold Upper Abdominal Stereotactic Body Radiotherapy (SBRT) with Surface Guidance: Single Center Experience

Surface tracking systems which is integrated to SBRT treatments enables motion tracking with 3D camera technology. We aim to evaluate treatment related outcomes in breath hold upper abdominal SBRT with surface guidance. Patients with upper abdominal lesions treated with breath hold and SGRT were evaluated retrospectively. Half an hour coaching was given to each patient prior to simulation. The CT scans were performed with IV contrast mostly in end insprium or end exprium phases whichever more comfortable and reproducible. The planning CTs were fused with magnetic resonance images (MRI) and positron emission CTs (PET-CT). Target and critical structures were contoured. All treatments were done in Varian EDGE (Varian, Palo Alto, CA, USA). Patients were navigated both with verbal guidance and tracking screen. Cone beam CTs (CBCT) were acquired with breath hold before treatment and 6D couch corrections were done. Optical Surface Management System (OSMS; Varian, Palo Alto, CA, USA) was used both in setup and motion tracking. Automated beam hold control was used during the treatment when patients moved outside of pre-defined range. Treatment duration varied depending on patient’s breath hold performance, prescribed dose, field number and modulation. Local recurrence is defined as size increase in MRI or increase in uptake in PET-CT. Fifty lesions were treated between May 2017 and July 2019. There are 33 liver metastases, 10 pancreatic tumors, 4 primary liver tumors and 3 paraaortic lymph node metastases. Thirty-eight patients have regular follow ups. Median follow up is 9 months. The doses are 25-60 Gy in 3-5 fractions. Ten patients experienced local failure. Local control rates for liver metastases, pancreatic tumors and hepatocellular carcinoma 85%, 60% and 66% respectively. Gastric bleeding is observed in one patient who has a pancreatic tail tumor after 1 year of treatment. It is possible to reduce respiratory organ motion with breath hold in SBRT treatments. SGRT is a noninvasive, real time method without using ionized radiation and allow us to make a correct setup and intra fractional monitoring.

A object detection and tracking method for security in intelligence of unmanned surface vehicles

Unmanned surface vehicle is increasingly becoming a research hotspot, which can be used in a variety of civil and military missions. However, compared with the relative maturity of other technologies, the sensing technology of unmanned surface vehicles is relatively weak. Taking "WAM-V-USV" as the research platform, this paper is mainly focus on the detection and tracking methods of moving objects with unmanned surface vehicles. This paper introduces the environment sensing system of unmanned vehicle, water surface image preprocessing, water antenna detection based on SVM, and the method of water surface object detection and tracking based on improved YOLOV3. The simulation results show that the proposed method can effectively improve the accuracy of moving object detection and tracking. Through the practical application in the Songhua River and the US Unmanned Surface Vehicles Open, it is proved that the algorithm has a good detection and tracking effect and meets the real-time requirements. Practice has proved that the object detection and tracking method based on deep learning greatly improves the perception ability and self-security of the unmanned surface vehicles.

Finite difference solutions for nonlinear water waves using an immersed boundary method

AbstractIn this article, high‐order finite difference solutions of the exact potential‐flow problem for nonlinear water waves are developed which treat both the free surface and the uneven sea bottom boundary conditions using an immersed boundary method (IBM). The convergence, accuracy, and stability of this approach is first established for the linear problem, using various orders of scheme and different grid discretization strategies. The nonlinear wave problem on a flat bottom is then considered, and the solutions are compared with the highly accurate stream function theory solution. The convergence performance of the numerical solution for this nonlinear wave problem is established. Finally, linear wave shoaling and nonlinear wave propagation over a submerged bar are also tested. A preconditioned iterative solution strategy is also developed and shown to provide optimal scaling of the solution effort with increasing number of unknowns. Compared with existing free surface tracking methods, the IBM retains the same level of accuracy and stability when solving the linear problem. For the nonlinear problem, the IBM behaves reasonably in terms of accuracy, but generally with slightly higher computational effort. When it comes to the wave–body interaction problem, it is expected that the IBM will be advantageous compared with the σ‐transform method, since it removes the necessity of constructing an artificial continuous free‐surface inside the body.

Modeling the Slump-Type Landslide Tsunamis Part I: Developing a Three-Dimensional Bingham-Type Landslide Model

This paper incorperates Bingham and bi-viscosity rheology models with the Navier–Stokes solver to simulate the dynamics and kinematics processes of slumps for tsunami generation. The rheology models are integrated into a computational fluid dynamics code, Splash3D, to solve the incompressible Navier–Stokes equations with volume of fluid surface tracking algorithm. The change between un-yield and yield phases of the slide material is controlled by the yield stress and yield strain rate in Bingham and bi-viscosity models, respectively. The integrated model is carefully validated by the theoretical results and laboratory data with good agreements. This validated model is then used to simulate the benchmark problem of the failure of the gypsum tailings dam in East Texas in 1966. The accuracy of predicted flood distances simulated by both models is about 73% of the observation data. To improve the prediction, a fixed large viscosity is introduced to describe the un-yield behavior of tailings material. The yield strain rate is obtained by comparing the simulated inundation boundary to the field data. This modified bi-viscosity model improves not only the accuracy of the spreading distance to about 97% but also the accuracy of the spreading width. The un-yield region in the modified bi-viscosity model is sturdier than that described in the Bingham model. However, once the tailing material yields, the material returns to the Bingham property. This model can be used to simulate landslide tsunamis.

Surface guided motion management in glottic larynx stereotactic body radiation therapy

Background and purposeInvoluntary motion due to swallowing cause inaccurate dose delivery during larynx radiotherapy, a deviation that may be particularly problematic during stereotactic body radiation therapy (SBRT). The goal of this study was to develop a motion management solution for larynx SBRT using surface imaging. Material and methodsTen patients were recently treated on a phase II study of larynx SBRT on a LINAC equipped with a surface guidance system. A small region of the immobilization mask was manually cut open to allow surface tracking. Pre-treatment and intra-fractional CBCTs were acquired to verify internal anatomy. Patients were verbally instructed not to swallow during treatment. During treatment delivery, beam hold was initiated by the Motion Management Interface if surface motion exceeded a patient-specific threshold. Patient motion was recorded in log files and analyzed. We also performed phantom studies to assess the theoretical impact of gating on dose delivery. ResultsThe frequency (6.5 ± 5.2 times per fraction) and duration (3.9 ± 2.5 seconds per swallow) of swallowing varied both between patients and fractions. The magnitude of each swallow showed mean peak amplitude at 5.8 ± 3.8 mm above baseline, mostly in the longitudinal direction. Beam duty cycle was 95.0% ± 7.0% (absolute range: 76–100%), with inefficiency most prominent in the early fractions. The 95th percentile residual motion was reduced from 3.4 mm to 2.3 mm with both verbal instruction and gating. Phantom studies confirmed dose delivery accuracy represented by gamma pass rate was improved by 5% using this approach. ConclusionsLaryngeal motion management using surface imaging is feasible and efficacious. Uncontrolled movement of the larynx was not uncommon during treatment, with gating reducing potential for unplanned dose deviations. Additional research is needed to determine the clinical benefit with this system.

Phased-resolved partial discharge patterns of 10 kV stator coils under different experimental conditions

The most five common types of partial discharge (PD) activities involving 10 kV motors, namely internal discharge, slot discharge, corona discharge, surface tracking and bar-to-bar discharge, were researched in this paper. PD was induced on some 10 kV coils with modern epoxy-mica insulation system through off-line experiment under different conditions. The phased-resolved partial discharge (PRPD) patterns of different types of PDs were recorded to characterize different PDs. This research can provide a reference in off-line fault diagnosis and be useful for the PD online monitoring of high voltage motors.

Observation of wave-driven air–water turbulent momentum exchange in a large but fetch-limited shallow lake

Abstract. Wind-induced waves play a key role in air–sea momentum and heat exchange. Fetch-limited shallow lakes differ significantly from open ocean circumstances since the wave field is characterized by young and growing waves that (i) are steeper and can collapse by white-capping at lower wind speeds, and (ii) travel with lower phase velocity. Consequently, momentum (and heat) flux estimation methods arising from oceanographic observations cannot be directly applied; however, few attempts have been made to describe air–water turbulent exchange in case of large, but still fetch-limited shallow lakes. Within a Croatian-Hungarian measurement campaign, turbulent flux measurements were performed in Lake Balaton. Momentum and heat fluxes were measured with eddy-covariance technique at an offshore station, while waves were simultaneously recorded with underwater acoustic surface tracking. Momentum fluxes were also recorded at two further stations closer to the shore. In this study, we analyze the measured wind stress and surface waves to reveal surface drag in case of highly fetch-limited conditions. We compare our results with relevant model formulations that attempt to estimate momentum flux using different wave state parameterizations (i.e. wave age and wave slope modified Charnock formulations) and show that derived drag and roughness length parameterizations differ significantly from oceanographic formulas.

대면적 레이저 직접묘화 공정에서 비점수차 자동초점 기술 연구

We developed an astigmatic autofocus optics and a control unit which were implemented in a direct laser writing system for a large area patterning process. The autofocus module is comprised of a collimated laser, a quadrant photodiode, an astigmatic lens, and a few polarizing optics. This system has a 0.526 V/μm focus error signal resolution in the 50x objective lens and a surface tracking capability of under 1 mm/s XY translation stage speed. In this study, we conducted a patterning experiment using SU-8 photocurable resist on a silicon wafer to study the accuracy of the astigmatic autofocus system. We highlighted some features of this system for future improvement.

Incompressible SPH simulation of flow past horizontal cylinder between plane wall and free surface

Flow past a circular cylinder located between free-surface and wall boundaries is modelled numerically using non-uniform particle size incompressible smoothed particle hydrodynamics (SPH). Several enhancements including Rhie and Chow interpolation, colour function-based free surface tracking, and modified particle shifting are introduced to increase the accuracy and efficiency of the method. A parameter study at constant Reynolds number, Re=150, examines the influence of Froude number (Fr=0.2−0.6), submergence ratio (H∕D=0.5−1.0, where H is the distance between the apex of the cylinder and undisturbed free surface, and D is the cylinder diameter), and bottom gap ratio (G∕D=1.0−5.0, where G is the distance between the base of the cylinder and the bed) on the ambient free-surface flow pattern and hydrodynamic force on the cylinder. It is found that the vortex shedding pattern depends on all three parameters. As the Froude number increases for fixed submergence ratio and bottom gap ratio, vortex shedding is eventually suppressed. As the submergence and bottom gap ratios increase, the threshold of vortex shedding suppression shifts to higher values of Froude number. The mean drag coefficient depends on the submergence ratio and bottom gap ratio but is independent of Froude number. Meanwhile, the lift coefficient depends on submergence ratio and Froude number but is independent of bottom gap ratio. Spectral analysis of force and free-surface elevation time signals shows that the free-surface deformation and lift force are closely related during the vortex shedding regime.

Free fall water entry of a cone in three degrees of freedom

The hydrodynamic problem of a three dimensional cone entering water in three degrees of freedom is analysed based on the incompressible velocity potential theory. The effect of horizontal motion and rotational motion on the entry process is investigated. The problem is solved through the boundary element method in the time domain. Two physical coordinate systems are constructed. One is the body-fixed system for the solution of fluid velocities and free surface tracking, and the other is the space-fixed system for equations of motion. To match the extremely small wetted surface at the initial stage, the former frame is stretched based on the ratio of physical coordinates and vertical travelled distance. The auxiliary function method is used to decouple the nonlinear mutual dependence between fluid loads and the body motion. Detailed results for cone motion, impact pressure and free surface are provided, and in-depth discussion on the effect of the horizontal motion and rotational motion is given.

3D-printed headrest for frameless Gamma Knife radiosurgery: Design and validation.

PurposeFrameless Gamma Knife stereotactic radiosurgery (SRS) uses a moldable headrest with a thermoplastic mask for patient immobilization. An efficacious headrest is time consuming and difficult to fabricate due to the expertise required to mold the headrest within machine geometrical limitations. The purpose of this study was to design and validate a three‐dimensional (3D)‐printed headrest for frameless Gamma Knife SRS that can overcome these difficulties.Materials and methodsA headrest 3D model designed to fit within the frameless adapter was 3D printed. Dosimetric properties of the 3D‐printed headrest and a standard‐of‐care moldable headrest were compared by delivering a Gamma Knife treatment to an anthropomorphic head phantom fitted with an ionization chamber and radiochromic film. Ionization measurements were compared to assess headrest attenuation and a gamma index was calculated to compare the film dose distributions. A volunteer study was conducted to assess the immobilization efficacy of the 3D‐printed headrest compared to the moldable headrest. Five volunteers had their head motion tracked by a surface tracking system while immobilized in each headrest for 20 min. The recorded motion data were used to calculate the average volunteer movement and a paired t‐test was performed.ResultsThe ionization chamber readings were within 0.55% for the 3D‐printed and moldable headrests, and the calculated gamma index showed 98.6% of points within dose difference of 2% and 2 mm distance to agreement for the film measurement. These results demonstrate that the headrests were dosimetrically equivalent within the experimental uncertainties. Average motion (±standard deviation) of the volunteers while immobilized was 1.41 ± 0.43 mm and 1.36 ± 0.51 mm for the 3D‐printed and moldable headrests, respectively. The average observed volunteer motion between headrests was not statistically different, based on a P‐value of 0.466.ConclusionsWe designed and validated a 3D‐printed headrest for immobilizing patients undergoing frameless Gamma Knife SRS.

Effects of Micro-Eggshells Filler on Tracking and Erosion Resistance of Silicone Rubber Composites

This study investigates the effects of micron-sized eggshells filler on resistance to tracking and erosion of silicone rubber composite. Eggshells with particle size from 44 to 53 microns were filled into liquid room temperature vulcanizing (RTV) silicone rubber with 0, 5, 15, 25, and 30 part per hundred of rubber (phr). IEC-60587 inclined plane test (IPT) was employed to appraise the surface tracking resistance. Thermogravimetric analysis was conducted to evaluate its thermal stability. Experimental results revealed an improvement of tracking and erosion resistance due to an addition of eggshells particles. Furthermore, the thermal stability of the composites showed variation in the increasing amount of the filler. The filler indicated that higher thermal stability of eggshells influences the heat resistance of the matrix. An increase of the heat resistance resulted in the ability to slow down tracking growth and erosion in the discharge region.

A Coupled Grid-Particle Method for Fluid Animation on GPU

In digital production environments, high-quality visual effects play a key role in our mobile device such as game and film. The simulation of fluid animation with free surface is an important area in computer graphic. However, the tracking of fluid surface is a challenging problem because of its instability. In this paper, a coupled grid-particle method for fluid animation surface tracking and detail preserving is proposed. Firstly, based on the nonequilibrium extrapolation method, we design a novel method for reconstructing distribution functions (DFs) of interface grids of lattice Boltzmann method (LBM) and couple the reconstruction method with LBM and volume of fluid (VOF) to track the free surface, which can obtain the accurate surface. Secondly, in order to avoid the loss of details caused by weaknesses in the traditional LBM-VOF method, we design a coupled grid-particle method that not only makes full use of the advantages of the coupled grid-particle method but also realizes the two-way coupling between grid method and particle method. Furthermore, for achieving the real-time requirements of fluid animation, we use GPU parallel computing to accelerate the simulation and use an improved screen space fluid (SSF) rendering method for realistic rendering. The various experiments show that this work can track the fluid surface with high precision and preserve the details of the fluid surface, and it also achieves good real-time performance in large-scale fluid simulation.

The Effect of Micro-Eggshells and Aluminium Hydroxide on Tracking Resistance of Silicone Rubber Composite

Break down due to surface tracking is one of the critical insulation failures, especially in the polymeric insulation. It has made worse the reliability of the power transmission system. This present work attempts to solve the problem by observing the effect on tracking resistance of adding micro-eggshells and aluminum hydroxide into the silicone rubber. In order to fabricate the composite specimen, red eggshells (63 to 74 μm), aluminum hydroxide, and RTV silicone rubber were procured. The constant voltage test method, according to the IEC-60587 standard, was used to evaluate the tracking resistance; each specimen was applied by 4.5 kV for 1 hour, and the tracking length was declared as the inverse of tracking resistance. Besides, the rule of mixtures was employed to estimate the thermal conductivity. The results show that the tracking resistance of the composite specimens was overall higher as compare to the pure rubber. Moreover, It was found that tracking resistance and thermal conductivity decreased when the eggshells increased. It was described that the rise of thermal accumulation on the insulator surface in the hybrid composite caused by lower thermal conductivity. Therefore, it could be concluded that the mixing of micro-eggshells and aluminum hydroxide should not be used as fillers for suppressing the tracking failures.

Real-time freeform surface and path tracking for force controlled robotic tooling applications

Abstract Modern force controlled robotic manipulators in combination with additional sensor configurations allow a wide range of operational scenarios for flexible production processes. This paper considers a sensor-based geometric approach for tracking curved freeform surfaces with the focus on robotic tooling applications such as polishing and grinding. A local approximation of the surface geometry is created from sparse distance measurements between the robotic tool and the workpiece maintaining a desired distance and orientation relative to the surface. The approach only relies on current sensor data and does not require any a priori model of the geometry from CAD data or previous 3D scans of the workpiece. The considered surface tracking controller allows the additional tracking of a planned path. The presented control is extended by a force controller to achieve a desired interaction force between the manipulator and the workpiece at a specified angle. To provide a flexible automation solution for the tooling of freeform surfaces, a path planning method is presented to cover a larger area based on the teaching of the area’s boundary. The considered approaches are realized on an experimental setup with the robotic manipulator KUKA LBR iiwa 14, where the surface tracking capabilities, as well as the performance of the force controller, are evaluated. The surface tracking and force controller are implemented directly on the robot controller while the sensor data processing is performed on a PLC which is connected to the robot controller via EtherCAT. The setup uses the position-based control interface for the integration of the surface tracking and the force control which introduces some limits on the performance of the applied control schemes but preserves the safety features and the collaborative behavior of the robotic manipulator.

Seafloor geodetic network establishment and key technologies

Seafloor geodetic network construction involves the development of geodetic station shelter, network configuration design, location selection and layout, surveying strategy, observation model establishment and optimization, data processing strategy and so on. This paper tries to present main technological problems involved in the seafloor geodetic network construction, and seek the technically feasible solutions. Basic conceptions of developing seafloor geodetic station shelters for shallow sea and deep-sea are described respectively. The overall criteria of seafloor geodetic network construction for submarine navigation and those of network design for crustal motion monitoring are both proposed. In order to enhance application performances of the seafloor geodetic network, the seafloor network configuration should prefer a symmetrical network structure. The sea surface tracking line measurements for determining the seafloor geodetic station position should also adopt an approximately symmetrical configuration, and we recommend circle tracking line observations combined with cross-shaped line (or double cross-shape line) observations for the seafloor positioning mode. As to the offset correction between the Global Navigation Satellite System antenna phase center and the acoustic transducer, it is recommended to combine the calibration through external measurements and model parameter estimation. Besides, it is suggested to correct the sound speed error with a combination of observation value correction and parameterized model correction, and to mainly use the model correction to reduce the influence of acoustic ray error on the seafloor positioning. Following the proposed basic designs, experiments are performed in shallow sea area and deep-sea area respectively. Based on the developed seafloor geodetic shelter and sufficient verification in the shallow sea experiment, a long-term seafloor geodetic station in the deep-sea area of 3000 m depth was established for the first time, and the preliminary positioning result shows that the internal precision of this station is better than 5 cm.