Three-dimensional Vector Research Articles

Abstract 14470: Right Ventricular Flow Visualization and Characterization via High Speed Volumetric Echo-PIV

Introduction: Although 4D echocardiography is used for many clinical applications, the evolving vortex flow in the right ventricle (RV) is relatively unknown and cannot be characterized with conventional echocardiography. An obstacle is that acquiring high frame rate (>100fps) data in presence of contrast is challenging and has not yet reported. Hypothesis: High frame-rate 4D echocardiographic data in presence of contrast can elucidate RV vortex flow via volumetric Echo-PIV (V-Echo-PIV). Methods: We devised a new transthoracic echocardiography (TTE) protocol using a Philips EPIQ CV9 ultrasound system with a 3D matrix probe (X5-1c) to acquire high frame-rate 4D data for processing with V-Echo-PIV. Apical RV focused view was used for full-volume acquisition by limiting the sector width and imaging depth solely to the entire RV. Visualization of the RV flow and wall dynamics was achieved by IV administration of Optison™ and Normal Saline. VolDICOMs were processed with V-Echo-PIV to obtain RV blood flow velocity field during the full cardiac cycle. Results: We improve the frame rates' scan lines to +30Hz. A 100Hz is achieved by stitching 4 cycles. We show that 4D RV flow can be quantified and characterized at high temporal resolution using V-Echo-PIV. Fig. 1A shows cine blood velocity in a healthy subject with a 51bpm heart rate. For which, V-Echo-PIV acquired 117 three-dimensional vector fields in one cardiac cycle, given the setting of 100Hz acquisition rate. The figure features flow patterns from systole to diastole, from left to right. Fig. 1B depicts the iso-surface of transient tricuspid vortex during diastolic RV filling. Conclusions: Enabled by high speed acquition in presence of contrast, V-Echo-PIV can be used as a viable alternative to 4D Flow MRI to visualize and evaluate real-time intra-cardiac blood flow, as it requires only a very short acquisition time and can be used wherever an echocardiography machine with matrix probes is available.

Three-dimensional electric-field vector resistivity imaging for deep subsurface fractures network in heterogeneous crystalline rocks

SUMMARY Crystalline rocks, exposed in different parts of the world and over about one-third of India, have complex aquifer systems, which pose a challenge to mapping groundwater dynamics. Electrical resistivity tomography in quasi-3-D and electrical logging of some borewells carried out in an experimental ‘hydrogeological park’ in southern India, which has numerous boreholes and other geophysical information for validation, were unable to map the existence of deeper bedrock fractures and their connectivity. We have attempted electric-field vector resistivity imaging (EVRI), a new tool, to resolve the possible fracture-induced deep interconnectivity in a hard rock aquifer system. In the experiment, multiple two-orthonormal-channels independent receiver nodes for potential measurements are deployed and illuminated with several current injections between ∼ 0.9–3.7 A in full 3-D fashion, which allowed for improved mapping of resistivity variation than earlier approaches. The EVRI-derived full 3-D model shows the presence of fractures for depths between 20 and 70 m with substantial resistivity variations, supported by some borewells hydraulic investigations. It has also enhanced lateral resolution for depths > 30 m and almost doubled the depth of investigation than earlier electrical models. EVRI results revealed unweathered/unfractured granitic rock with no significant signature of fractures beyond 70 m depth that corroborates with existing borehole logs and hydrogeological conceptual model. Therefore, this study demonstrates the potential of EVRI for 3-D mapping of heterogeneous crystalline rocks, which would greatly help in groundwater management.

Three-dimensional vector ECG analysis in the diagnosis of the left anterior fascicular block

The relevance of the study is due to the complexity of the differential diagnosis of left anterior fascicular block (LAFB) with myocardial infarction and left ventricular hypertrophy based on a standard ECG.Aim. Determination of the criteria for LAFB according to the data of three- dimensional vectorcardiography with an analysis of the rate of formation of the vector loop.Material and research methods. The study included 85 patients who underwent a 12-lead ECG study. 2 groups of patients were selected. The main group of 56 patients with LAFB, mean age was 63.3±16.6 (M±δ) years, 34 men and 22 women. The control group included 29 healthy individuals, the mean age was 21.4±2.5 (M± δ) years, 12 men and 17 women. All patients underwent synchronous recording of 12 standard ECG leads in the IS «Unified Cardiologist of the Republic of Tatarstan» and reconstruction of a three-d imensional vectorcardiogram using the McFee-Parungao system with an analysis of the vector loop formation rate using EasyECG Rest ATES Medica software (Russia).Results and conclusions. It is shown that for LAFB the movement of the vector loop counterclockwise is typical in the frontal plane; the presence of 2 extrema, the second is directed upwards, to the right and back. On the graph of the rate of formation of a spatial vector loop, 2 peaks are recorded with a decrease in the rate in the final part of the QRS loop by 2–2.5 times relative to the first peak, which reflects a slowdown in myocardial excitation in the output section of the left ventricle.

A collaboration-based multi-objective algorithm for distributed hybrid flowshop scheduling with resource constraints

With the development of the realistic manufacturing process, the distributed scheduling, machine velocity, and resource constraints have attracted much attention. This paper addresses the distributed hybrid flowshop scheduling problem (DHFSP) with machine velocity and resource constraints to minimize the makespan and total energy consumption simultaneously. A mathematical model of the problem is formulated. To solve the proposed problem, a collaboration-based multi-objective algorithm (CBMA) is developed. First, a machine velocity adjustment rule considering resource constraints is proposed by analyzing the characteristics of the problem. In the proposed algorithm, each solution is represented by a well-designed three-dimensional vector. Then, an objective-balanced machine selection strategy is employed to balance the quality and diversity of the initial population. Next, a Pareto knowledge-based collaborative search mechanism enhances the global search ability in each iteration. To improve the convergence of the algorithm, a distributed machine velocity adjustment rule is embedded into the local search. Finally, a set of instances based on realistic industrial processes are tested. The effective performance of the proposed algorithm is verified through computational comparisons.

Setup accuracy and margins for surface-guided radiotherapy (SGRT) of head, thorax, abdomen, and pelvic target volumes

The goal of the study was to evaluate the inter- and intrafractional patient setup accuracy of target volumes located in the head, thoracic, abdominal, and pelvic regions when using SGRT, by comparing it with that of laser alignment using patient skin marks, and to calculate the corresponding setup margins. A total of 2303 radiotherapy fractions of 183 patients were analyzed. All patients received daily kilovoltage cone-beam computed tomography scans (kV-CBCT) for online verification. From November 2019 until September 2020, patient setup was performed using laser alignment with patient skin marks, and since October 2020, using SGRT. The setup accuracy was measured by the six degrees of freedom (6DOF) corrections based on the kV-CBCT. The corresponding setup margins were calculated using the van Herk formula. Analysis of variance (ANOVA) was used to evaluate the impact of multiple factors on the setup accuracy. The inter-fractional patient setup accuracy was significantly better using SGRT compared to laser alignment with skin marks. The mean three-dimensional vector of the translational setup deviation of tumors located in the thorax, abdomen, and pelvis using SGRT was 3.6 mm (95% confidence interval (CI) 3.3 mm to 3.9 mm) and 4.5 mm using laser alignment with skin marks (95% CI 3.9 mm to 5.2 mm; p = 0.001). Calculation of setup margins for the combined inter- and intra-fractional setup error revealed similar setup margins using SGRT and kV-CBCT once a week compared to laser alignment with skin marks and kV-CBCT every other day. Furthermore, comparable setup margins were found for open-face thermoplastic masks with AlignRT compared to closed-face thermoplastic masks with laser alignment and mask marks. SGRT opens the possibility to reduce the number of CBCTs while maintaining sufficient setup accuracy. The advantage is a reduction of imaging dose and overall treatment time. Open-face thermoplastic masks may be used instead of closed-face thermoplastic masks to increase the patient's comfort.

A resilience measure for the international nickel trade network

The current rise in global trade protectionism and geopolitical conflicts have had a definite impact on the development of the nickel trade network. Therefore, this paper takes a comprehensive view of the nickel industry chain, considers four types of nickel trade in the upstream and downstream, and carves out a directionally weighted trade network. The evolution of the structural resilience of the nickel trade network over the period 2001–2021 is first measured under deliberate attack or random attack, and a three-dimensional spatially-weighted vector modelling framework based on the Data Envelopment Analysis common set of weight model is proposed to assess the resilience of the nickel trade network in terms of three dimensions: absorptive capacity, buffering capacity, and recovery capacity. The results show that structural resilience of the nickel trade network has improved over the period 2001–2021, but that the network will become paralyzed if 10%–20% of nodes are deliberately attacked. The absorptive capacity, buffering capacity, and recovery capacity of the nickel network are all low when major demand-driven nations like U.S., China, U.K, Germany, and Netherlands are attacked. Finally, recommendations are made to improve the security and stability of the nickel trade.

Three-Dimensional Space Vector Modulation for Four-Leg Current-Source Inverters

Unbalanced loads are general in uninterruptible power supply (UPS), standalone power generation applications and the failure mode of three-phase inverters. Three-phase four-leg inverters are a well-known solution to handle neutral currents caused by unbalanced loads. In four-leg inverters, three-dimensional space vector modulation (3DSVM) is widely used. However, the 3DSVM of four-leg current source inverter (CSI) has not been systematically studied so far. To fill this gap, this paper proposes a 3DSVM for CSI. The definition of the current vector, the identification of the position of reference vector and the sequence of switches are introduced. Under unbalance loads, the symmetrical load voltage can be realized, which complies with IEEE Std. 1159-2019. The output current can comply with IEEE Std. 519-2014. The proposed 3DSVM has the potential to extend the advanced modulation strategies that have been implemented/ proposed on three-leg CSI.

3D Surface Imaging in Reducing Setup Error for Prone Whole Breast Radiotherapy

For patients undergoing whole breast radiotherapy, treatment in the prone position allows for reduced dose to critical organs such as the heart and lungs. However, this treatment position comes with greater challenges in reproducibility and setup error given the unstable position. Our objective was to investigate the benefit of using 3D surface imaging to reduce daily setup errors for these patients. We performed a retrospective review of consecutive breast patients receiving prone breast radiotherapy at our institution. All patients were positioned initially using setup tattoos and twice a week, the positioning was adjusted using the aid of a motion tracking system. Then, a daily kilovoltage (kV) cone beam computed tomography (CBCT) image was acquired and positioning was adjusted to setup the breast and chest wall. Shifts in each translational direction were recorded and the three-dimensional vector displacement was calculated. For each patient the average displacements on days where a motion tracking system was used were compared to days whereas motion tracking system was not used. Patients were classified into significant benefit (more than 4 mm improvement), small benefit (0-4 mm improvement) or increased error (increased shifts on days a motion tracking system was used). Patient demographics were collected including stage, BMI, weight, heigh, age, ethnicity. Comparisons were made using t-tests. A total of 40 patients with stage T0-2N0 breast cancer were included. The median age was 64 and 60% of patients had left sided breast cancer. A total of 665 daily CBCT scans were analyzed, and the median daily vector displacement was 7.2 mm (1-21 mm). The median displacement on treatments where a motion tracking system was used (41% of treatments) was 6.1 mm versus 8.1 mm when not used (p<.0001). The use of a motion tracking system significantly reduced the occurrence of shifts more than 1 cm (12% vs. 33%, p < .0001) and 5 mm (65% vs. 83% p < .0001). For individual patients, 28% showed a significant improvement, 55% showed small improvement, 17% showed increased error. The median BMI was 27, weight was 71 kg, and neither was associated with an improvement in the use of Align RT (p > .05). However, patients in the small improvement group had a higher BMI than patients in the other two groups 29 vs. 25 (p = .01). A similar association was seen for weight (p < .05). No association was found for the benefit of a motion tracking system for height, age, stage or ethnicity. The use of 3D surface imaging for breast cancer patients receiving prone whole breast radiotherapy on average significantly reduced setup errors. For patients with higher BMI there was a consistent small reduction in setup error when compared to using setup marks alone. For patients with lower BMI, caution should be exercised as there was more variation with some patients demonstrating a large benefit and other patients having an increased setup error with the use of surface imaging. Further research is needed to investigate on the optimal use of this technology.

Discriminating States of Polarization

Equiprobable incoherent mixtures of two totally polarized states of light whose associated three-dimensional Jones vectors are mutually orthogonal are called discriminating states and constitute a peculiar type of state that plays a key role in the characteristic decomposition of a generic state into a totally polarized state, a totally unpolarized state, and a discriminating state. In general, discriminating states are three-dimensional, in the sense that the strengths of the three components of the electric field are nonzero for any Cartesian reference frame considered. In the limiting case that the electric field evolves in a fixed plane, the discriminating state is said to be regular and corresponds to a two-dimensional unpolarized state. The special features of discriminating states cover, e.g., their possible synthesis from infinite pairs of mutually orthogonal states as well as their transverse spin. The nature and properties of discriminating states are comprehensively analyzed based on their associated intrinsic Stokes parameters, which leads to meaningful interpretations in terms of the associated polarization ellipsoids and spin vectors.

Three-dimensional acoustic vector field model using Gaussian beam tracing.

A three-dimensional acoustic vector field model was developed using Gaussian beam tracing. The field at any location is computed by coherently summing all contributing beams, where the beam equation of particle velocity depends only on beam width and eikonal. A deep-sea long-range sound propagation experiment in the South China Sea was analyzed using vector hydrophone measurements of particle velocity and sound pressure. The results were compared with the model predictions, indicating that beam tracing is effective in predicting sound pressure and acoustic vector fields in deep water.

Free-space generation of three-dimensional tunable vector optical cages.

The generation of three-dimensional tunable vector optical cages through full polarization modulation requires complex polarization states. This paper takes the vector Airy optical cage as an example to generate a three-dimensional tunable high-quality optical cage based on the Pancharatnam-Berry phase principle. The proposed method in this paper possesses the capability of arbitrary modulation in various aspects, including the quantity of optical cages and their respective sizes as well as three-dimensional spatial positions. Moreover, the intensity of each optical cage can be modulated independently. This research will improve the capture efficiency of optical tweezers and promote further development in fields of efficient optical trapping, particle manipulation, high-resolution microscopic manipulation, and optical communication.

AI-Enabled Condition Monitoring Framework for Outdoor Mobile Robots Using 3D LiDAR Sensor

An automated condition monitoring (CM) framework is essential for outdoor mobile robots to trigger prompt maintenance and corrective actions based on the level of system deterioration and outdoor uneven terrain feature states. Vibration indicates system failures and terrain abnormalities in mobile robots; hence, five vibration threshold classes for CM in outdoor mobile robots were identified, considering both vibration source system deterioration and uneven terrain. This study proposes a novel CM approach for outdoor mobile robots using a 3D LiDAR, employed here instead of its usual use as a navigation sensor, by developing an algorithm to extract the vibration-indicated data based on the point cloud, assuring low computational costs without losing vibration characteristics. The algorithm computes cuboids for two prominent clusters in every point cloud frame and sets motion points at the corners and centroid of the cuboid. The three-dimensional vector displacement of these points over consecutive point cloud frames, which corresponds to the vibration-affected clusters, are compiled as vibration indication data for each threshold class. A simply structured 1D Convolutional Neural Network (1D CNN)-based vibration threshold prediction model is proposed for fast, accurate, and real-time application. Finally, a threshold class mapping framework is developed which fuses the predicted threshold classes on the 3D occupancy map of the workspace, generating a 3D CbM map in real time, fostering a Condition-based Maintenance (CbM) strategy. The offline evaluation test results show an average accuracy of vibration threshold classes of 89.6% and consistent accuracy during real-time field case studies of 89%. The test outcomes validate that the proposed 3D-LiDAR-based CM framework is suitable for outdoor mobile robots, assuring the robot’s health and operational safety.

Characterization of Fiber-Optic Vector Magnetic Field Sensors Based on the Magneto-Strictive Effect.

Fiber-optic magnetic field sensors have garnered considerable attention in the field of marine monitoring due to their compact size, robust anti-electromagnetic interference capabilities, corrosion resistance, high sensitivity, ease of multiplexing and integration, and potential for large-scale sensing networks. To enable the detection of marine magnetic field vector information, we propose an optical fiber vector magnetic field sensor that integrates three single-axis sensors in an orthogonal configuration. Theoretical analysis and experimental verification are conducted to investigate its magnetic field and temperature sensing characteristics, and a sensitivity matrix is established to address the cross-sensitivity between the magnetic field and temperature; experimental tests were conducted to assess the vector response of the three-dimensional (3D) vector sensor across the three orthogonal axes; the obtained experimental results illustrate the commendable magnetic field vector response exhibited by the sensor in the orthogonal axes, enabling precise demodulation of vector magnetic field information. This sensor presents several advantages, including cost-effectiveness, easy integration, and reliability vectorially. Consequently, it holds immense potential for critical applications in marine magnetic field network detection.

3-D SVM for Three-Phase Open-End Winding Drives With Common DC Bus

Existing modulation strategies for three-phase open-end winding drives (OWDs) with common dc bus usually conduct the modulations for α-β subspace and zero-sequence loop (ZSL) separately, which cannot reflect the relationship between α-β subspace and ZSL and fully utilize the dc bus voltage. To this end, this paper proposes a three-dimensional space vector modulation (3-D SVM) strategy for three-phase OWDs with common dc bus, which can be conducted in both a-b-c and α-β- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> coordinates, leading to full utilization of dc bus voltage and convenient overmodulation adjustment. Voltage vector distributions of OWD in the 3-D spaces with a-b-c and α-β- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> coordinates are revealed at first. Subsequently, the three adjacent voltage vectors for reference voltage vector synthesis are selected based on the relationship between leg-voltage potentials, avoiding the complex tetrahedron identification in existing 3-D SVMs for other drive topologies. In addition, overmodulation in different coordinates is also investigated. Experimental results are presented to validate the feasibility of the proposed 3-D SVM for OWDs with common dc bus.

Nested invariant tori foliating a vector field and its curl: Toward MHD equilibria and steady Euler flows in toroidal domains without continuous Euclidean isometries

This paper studies the problem of finding a three-dimensional solenoidal vector field such that both the vector field and its curl are tangential to a given family of toroidal surfaces. We show that this question can be translated into the problem of determining a periodic solution with periodic derivatives of a two-dimensional linear elliptic second-order partial differential equation on each toroidal surface and prove the existence of smooth solutions. Examples of smooth solutions foliated by toroidal surfaces that are not invariant under continuous Euclidean isometries are also constructed explicitly, and they are identified as equilibria of anisotropic magnetohydrodynamics. The problem examined here represents a weaker version of a fundamental mathematical problem that arises in the context of magnetohydrodynamics and fluid mechanics concerning the existence of regular equilibrium magnetic fields and steady Euler flows in bounded domains without continuous Euclidean isometries. The existence of such configurations represents a key theoretical issue for the design of the confining magnetic field in nuclear fusion reactors known as stellarators.

Channel Estimation for Near-Field XL-RIS-Aided mmWave Hybrid Beamforming Architectures

Extremely large-scale reconfigurable intelligent surface (XL-RIS) has been a prospective capacity-enhancing technique. Faced with XL-RIS-aided millimeter wave (mmWave) communications, we propose a low-complexity channel estimation strategy with the near-field spherical wavefront assumption. It separates the whole channel estimation procedure into two phases to decrease pilot use and computational complexity: 1) estimation of angular-domain parameters of the base station (BS) and users equipped with the hybrid beamforming architecture, and 2) estimation of cascaded angular- and polar-domain parameters of the XL-RIS. Particularly, in the first and second phases, the three-dimensional multiple measurement vector compressive sensing (3D-M-CS) framework and the 3D distributed CS (3D-D-CS) framework are proposed for enhanced parameter estimation, respectively. Then the variants of Look Ahead Orthogonal Match Pursuit (LAOMP), i.e., 3D-M-LAOMP and 3D-D-LAOMP, are developed for solving our proposed CS frameworks.

Deep reinforcement learning spacecraft guidance with state uncertainty for autonomous shape reconstruction of uncooperative target

In recent years, space research has shifted heavily its focus towards enhanced autonomy on-board spacecrafts for on-orbit servicing activities (OOS). OOS and proximity operations include a variety of activities: the focal point of this work is the autonomous guidance of a chaser spacecraft for the shape reconstruction of an artificial uncooperative object. Adaptive guidance depends on the ability of the system to build a map of the uncertain environment, figuring out its location inside of it and accordingly determining the control law. Thus, autonomous navigation is framed as an active Simultaneous Localization and Mapping (SLAM) problem and modeled as a Partially Observable Markov Decision Process (POMDP). A state-of-the-art Deep Reinforcement Learning (DRL) method, Proximal Policy Optimization (PPO), is investigated to develop an agent capable of cleverly planning the shape reconstruction of the target. Starting from previous research on the topic, this work develops further proposing a continuous action space, such that the agent is no more forced to choose between a predefined set of possible discrete actions, fixed both in magnitude and direction. In this way any combination of the three-dimensional thrust vector components is available. The chaser spacecraft is a small satellite mounting an electric propulsion engine defining the action space range, in linearized eccentric relative motion with the selected uncooperative object. Through a rendered triangular mesh, the agent capabilities of geometry reconstruction and mapping are evaluated, considering the number of quality pictures made for each face. Extensive training tests are performed with random initial conditions to verify the generalizing capability of the DRL agent. The results are then validated in a comprehensive testing campaign, whose primary focus is the introduction of noisy measurements coming from navigation, affecting pose estimation. The sensitivity of the proposed method to this condition is analyzed and the efficiency of a retraining procedure is examined. The applicability of DRL methods and neural networks to support autonomous guidance in a close proximity scenario is corroborated and the technique employed is vastly tested and verified.

An effective model for boundary vortices in thin-film micromagnetics

Ferromagnetic materials are governed by a variational principle which is nonlocal, nonconvex and multiscale. The main object is given by a unit-length three-dimensional vector field, the magnetization, that corresponds to the stable states of the micromagnetic energy. Our aim is to analyze a thin film regime that captures the asymptotic behavior of boundary vortices generated by the magnetization and their interaction energy. This study is based on the notion of “global Jacobian” detecting the topological defects that a priori could be located in the interior and at the boundary of the film. A major difficulty consists in estimating the nonlocal part of the micromagnetic energy in order to isolate the exact terms corresponding to the topological defects. We prove the concentration of the energy around boundary vortices via a [Formula: see text]-convergence expansion at the second order. The second-order term is the renormalized energy that represents the interaction between the boundary vortices and governs their optimal position. We compute the expression of the renormalized energy for which we prove the existence of minimizers having two boundary vortices of multiplicity [Formula: see text]. Compactness results are also shown for the magnetization and the corresponding global Jacobian.

Vector assessment model in R3 space for forest value

While Forests have enormous potential and value, it is necessary to establish a valuation model to help us make decisions and make sound recommendations. To this end, I have made the following contributions. I collected nine data sets from 12 forests and integrated them into three dimensions. I combined the subjective hierarchical analysis (AHP) and CRITIC objective assignment method to obtain the weights. Using the indicators and data of these three dimensions, I constructed a vector assessment model in R3 space, where the modal length of the spatial vector represents the forest value, the angle with the standard vector (1, 1, 1) represents the space of progress, and the plane established by the two vectors together represents the direction of improvement. In addition, I found a relationship between artificial logging intensity and forest value, and established extreme value points, concluding that appropriate artificial logging helps to improve forest value. Because the modal length of Siberian coniferous forests is 1.008 and the angle of 13 degrees, there is a lot of room for improvement, and I analysed this further. I used the GM (1,1) model to predict the carbon sequestration data of Siberian coniferous forests, and the results are consistent with the analysis results of the three-dimensional vector model I established.

Invariant manifold growth formula in cylindrical coordinates and its application for magnetically confined fusion

For three-dimensional vector fields, the governing formula of invariant manifolds grown from a hyperbolic cycle is given in cylindrical coordinates. The initial growth directions depend on the Jacobians of Poincaré map on that cycle, for which an evolution formula is deduced to reveal the relationship among Jacobians of different Poincaré sections. The evolution formula also applies to cycles in arbitrary finite n-dimensional autonomous continuous-time dynamical systems. Non-Möbiusian/Möbiusian saddle cycles and a dummy X-cycle are constructed analytically as demonstration. A real-world numeric example of analyzing a magnetic field timeslice on EAST is presented.