Irregular Field Research Articles

Matching Vector Filtering Methods For Sea Ice Motion Detection Using SAR Imagery Feature Tracking

Applying feature tracking techniques to SAR imagery generates high resolution sea ice motion fields. However, the bad matching vectors still exist after the NNDR (Nearest Neighbor Distance Ratio) test and contaminate the derived motion fields, which need to be identified and filtered out. In this research, we propose two algorithms to eliminate such wrong matching vectors. The first employs the matching results derived by the maximum cross-correlation (MCC) method as the reference motion fields to evaluate such wrong matches. The second method employs the local spatial consistency presumption of sea ice motion fields. A Voronoi diagram is applied to slice the overlapping area of two SAR images into many fractions, and each fraction extends its size 50% outward to calculate the regional mean sea ice flow vector and standard deviation. Any vector within the fraction that exceeds 3 times the regional standard deviation will be recognized as an outlier and filtered out. Two methods are tested to two cases with strong rotation or irregular sea ice motion fields derived from Sentinel-1 imagery. The overall accuracy of our two methods is 93.9% and 98.7%, and they sacrifice 6.12% /1.22% of the correct vectors to filter out 100.0% / 94.12% of the wrong vectors for the MCC referenced filter and Voronoi fragmented filter, respectively.

Dosimetric study of Rapid Arc therapy during Craniospinal Irradiation in Adult patients

Context: Adult medulloblastomas are very rare and constitute only 1% of the central nervous system tumors in adults. CSI treatment is challenging in adults due to the long, irregular target volume, critical structures, and field matchings due to multiple fields. Aims: This retrospective dosimetric study of adult patients who underwent Craniospinal irradiation was done to get insight into the challenges in the treatment and advantages of using RapidArc technique. Materials and Methods: The computed dosimetric rapid arc planning data of 3 adult cases who underwent Craniospinal irradiation between November 2018 and June 2021 were studied. Results: In our study mean conformity index (range) was 0.95 (0.91–1) and Mean homogeneity index (range) was 0.11 (0.06–0.15). Mean dose to the lenses, lungs, heart, and kidneys was 6.4 Gy, 9.4 Gy, 5 Gy, and 7 Gy, respectively. Conclusions: Volumetric modulated arc therapy technique for Craniospinal irradiation gives conformal dose distribution within the target, better normal tissue sparing, and more homogeneous dose distribution in the field junctions without the need to move the junction.

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

Row anchor selection classification method for early-stage crop row-following

The field navigation tasks of agricultural robots are the basis for implementing field management projects in the early stages of seedlings guided by precision agriculture policies. High accuracy and execution speed of navigation tasks are needed for the escalating field machine implementations in a significantly unstructured and irregular field environment, contributing to the difficulty and urgency of achieving a field navigation solution with high navigation accuracy while maintaining proper execution speed. In our study, the row anchor selection classification method (RASCM) is presented to track early-stage crop rows, and the early corn seedling dataset (E-dataset) and LRC-dataset are developed for the measurement of the experimental results. RASCM is divided into three parts, including a row anchor selection method (RasM), a lightweight deep convolutional neural network (DCNN) network GhostNet, and a combined loss function (C-loss). It is suggested that RASCM has achieved good results in terms of calculation speed and accuracy by comparing the end-to-end regression operation based on the steering wheel angle (E2Er) and crop row pixel segmentation (SeG) approaches with RASCM on the LRC-dataset, which can be effectively applied in actual projects. Finally, a class activation map (CAM) is used to visualize the internal working mechanism of GhostNet, and the demonstrated effectiveness of GhostNet is not limited to the RasM labeling area. In contrast, broad global features are learned, and the previous noise is highly mitigated. Strong generalization performance for different environments is displayed by using RACSM, contributing to the effectiveness of early-stage crop row-following. The main contribution of our paper is the proposal of RASCM, which is a novel method in the field of early-stage crop row-following and can be used as a basic reference for subsequent work in this research field.

Mean and variance of the Eulerian and Lagrangian horizontal velocities induced by nonlinear multi-directional irregular water waves

In this paper, we study the mean and variance of the Eulerian and Lagrangian fluid velocities as a function of depth below the surface of directionally spread irregular wave fields given by JONSWAP spectra in deep water. We focus on the behaviour of these quantities in the bulk of the water, and using second-order potential flow theory we derive new simple asymptotic approximations for their decay in the limit of large depth below the surface. Specifically, we show that when the depth is greater than about 1.5 peak wavelengths, the variance of the Eulerian velocity decays in proportion to exp ⁡ ( − ( 135 4 ) 1 / 3 ( − k p z ) 2 / 3 ) , and the mean Lagrangian velocity decays in proportion to 1 ( − k p z ) 1 / 6 exp ⁡ ( − ( 135 4 ) 1 / 3 ( − k p z ) 2 / 3 ) . Here, k p is the peak wave number and z is the vertical coordinate measured positively upwards from the still water level. We test the accuracy of the second-order formulation against new fully nonlinear simulations of both short crested and long crested irregular wave fields and find a good match, even when the simulations are known to be affected substantially by third-order effects. To our knowledge, this marks the first fully nonlinear investigation of the Eulerian and Lagrangian velocities below the surface in irregular wave fields.

Unifying organization and operation of irregular spatio-temporal field data with a tensor-based approach

Unifying organization and operation of irregular spatio-temporal field data with a tensor-based approach

Primitive element driven unified organization and operation of irregular spatiotemporal field data a tensor approach

Primitive element driven unified organization and operation of irregular spatiotemporal field data a tensor approach

Unifying organization and operation of irregular spatio-temporal field data with a tensor-based approach

Unifying organization and operation of irregular spatio-temporal field data with a tensor-based approach

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

A tensor-based approach to unify organization and operation of data for irregular spatio-temporal fields

APOPHIS – effects of the 2029 Earth’s encounter on the surface and nearby dynamics

ABSTRACT The 99942 Apophis close encounter with Earth in 2029 may provide information about asteroid’s physical characteristics and measurements of Earth’s effects on the asteroid surface. In this work, we analysed the surface and the nearby dynamics of Apophis. The possible effects of its 2029 encounter on the surface and environment vicinity are also analysed. We consider a 340 m polyhedron with a uniform density (1.29, 2.2, and 3.5 g cm−3). The slope angles are computed, as well their variation that arises during the close approach. Such variation reaches 4° when low densities are used in our simulations and reaches 2° when the density is high. The zero-velocity curves, the equilibrium points, and their topological classification are obtained. We found four external equilibrium points and two of them are linearly stable. We also perform numerical simulations of bodies orbiting the asteroid, taking into account the irregular gravitational field of Apophis and two extra scenarios of perturbations: the solar radiation pressure and the Earth’s perturbation during the close approach. The radiation pressure plays an important role in the vicinity of the asteroid, only cm-sized particles survived for the time of integration. For densities of 2.2 and 3.5 g cm−3, a region of 5 cm radius particles survived for 30 yr of the simulation, and for 1.29 g cm−3, only particles with 15 cm of radius survived. The ejections and collisions are about 30–50 times larger when the close encounter effect is added but around 56–59 per cent of particles still survive the encounter.

In-place rotation of particles and time-average vibrational vortex on a Chladni plate

It is traditionally believed that particles will settle at the nodes or antinodes of a vibrating plate, forming stable standard or inverse Chladni patterns. The Chladni effect has been utilized to manipulate or pattern objects such as solid particles and even biological cells. The motion of particles near the nodal point is usually considered stochastic, and the stable and orderly movement of particles is impossible. Here, we experimentally show that the aggregation of particles can keep in-place rotating with different chirality at the nodal point of a vibrating plate, by utilizing specific dual-frequency oscillating signals to a single vibrator. To understand the motion of particles, irregular whirlpool force fields are calculated by considering the function of time dependent terms of the vibration response. Our findings reveal the time averaged vibrational vortex which can trap and rotate objects or particle clusters. It offers a new controllable degree of freedom for the movement of objects on a Chladni plate.

Reconstruction of irregular missing seismic data using conditional generative adversarial networks

During acquisition, due to economic and natural reasons, irregular missing seismic data are always observed. To improve accuracy in subsequent processing, the missing data should be interpolated. A conditional generative adversarial network (cGAN) consisting of two networks, a generator and a discriminator, is a deep-learning model that can be used to interpolate the missing data. However, because cGAN is typically data set oriented, the trained network is unable to interpolate a data set from an area different from that of the training data set. We design a cGAN based on Pix2Pix GAN to interpolate irregular missing seismic data. A synthetic data set synthesized from two models is used to train the network. Furthermore, we add a Gaussian-noise layer in the discriminator to fix a vanishing gradient, allowing us to train a more powerful generator. Two synthetic data sets synthesized by two new geologic models and two field data sets are used to test the trained cGAN. The test results and the calculated recovered signal-to-noise ratios indicate that although the cGAN is trained using synthetic data, the network can reconstruct irregular missing field seismic data with high accuracy using the Gaussian-noise layer. We test the performances of cGANs trained with different patch sizes in the discriminator to determine the best structure, and we train the networks using different training data sets for different missing rates, demonstrating the best training data set. Compared with conventional methods, the cGAN-based interpolation method does not need different parameter selections for different data sets to obtain the best interpolation data. Furthermore, it is also an efficient technique as the cost is because of the training, and after training, the processing time is negligible.

Neural Basis of Numeric Incongruity Processing and Mental Arithmetic in Human Brain

This paper presents a general overview of the practical applicability of non-linear potential flow solvers for water wave propagation. Those numerical models are unable to describe explicitly the wave breaking phenomena, including free surface reconnexion, energy dissipation, etc. This reduces their range of application in real sea waves, which are in the most general context irregular and directional wave fields. This study covers the influence of discretization, water depth, directional spreading and spectral peakedness on the limitations in the use of such non-linear potential models. The approach at use relies on a highly non-linear model based on the High-Order Spectral method.

On two approaches to the third-order solution of surface gravity waves

A third-order approximate solution for surface gravity waves in the finite water depth is studied in the context of potential flow theory. This solution corresponds to the steady-state part of a multidirectional irregular wave field and provides explicit expressions for the surface elevation, free-surface velocity potential, and velocity potential. The amplitude dispersion relation is also provided. Two approaches are used to derive the third-order analytical solution, resulting in two types of approximate solutions: the perturbation solution and the Hamiltonian solution. The perturbation solution is obtained by a classical perturbation technique in which the time variable is expanded in multiscale to eliminate secular terms. The Hamiltonian solution is derived from the canonical transformation in the Hamiltonian theory of water waves. By comparing the two types of solutions, it is found that they are completely equivalent for the first- and second-order solutions and the nonlinear dispersion, but for the third-order part only the sum–sum terms are the same. Due to the canonical transformation that could completely separate the dynamic and bound harmonics, the Hamiltonian solutions break through the difficulty that the perturbation theory breaks down due to singularities in the transfer functions when the quartet resonance criterion is satisfied. Furthermore, it is also found that some time-averaged quantities based on the Hamiltonian solution, such as mean potential energy and mean kinetic energy, are equal to those in the initial state in which the sea surface is assumed to be a Gaussian random process. This is because there are associated conserved quantities in the Hamiltonian form. All of these show that the Hamiltonian solution is more reasonable and accurate to describe the third-order steady-state wave field. Finally, based on the Hamiltonian solution, some statistics are given such as the volume flux, skewness, excess kurtosis, and non-uniqueness of the induced mean flow and mean surface.

A Physical Model of Wave Attenuation in Pancake Ice

A physical model is discussed that mimics the interaction between ocean waves and a multitude of loose pancake ice floes, which form the outer edge of the Arctic and Antarctic marginal ice zones during winter sea ice formation. The pancakes were modeled by using ice cubes with different concentrations, while waves were generated mechanically. The ice cubes had a dimension of a few centimeters, which was two orders of magnitude smaller than the dominant wavelength. Experiments consisted of tracking the propagation of regular and irregular wave fields along the flume as they crossed the ice cover to measure the rate of ice-induced wave attenuation. Results indicate that wave attenuation increases with ice concentration with only 30% of energy allowed to pass through high-density covers. Wave energy is attenuated across the entire spectral domain and is strongest at high frequencies. This results in a downshift of the spectral peak.

THE CROPPING PATTERN CHARACTERIZATION, SOCIOECONOMIC ANALYSIS AND PROBLEMS OF MAIZE (Zea Mays) SEED PRODUCTION IN DEUKHURI, DANG NEPAL

Maize ranks second position after rice both in area and production in Nepal. In recent year, the area under Maize cultivation has steadily increase but the productivity has been low which is unable to meet the demand and is mostly affected by insect/pests and diseases. The purpose of this study was to assess the socioeconomic condition of maize producers. A field survey was carried out in which 30 households of Lamahi Municipality of Dang district during June 2019.The Lamahi municipality was strictly involved in seed production and the RajpurGaupaika was found better in seed production than Gaduwa and Rapti Gaupalika.Purposive sampling technique was used to collect data using pre-tested interview schedule. Pairwise ranking method was used to rank problems based on index value. The average area used for seed production was 0.3hac with productivity of 0.53mt.The major(66.7%) source of foundation seed was obtained from NARC, Khajura,Nepalgunj.About 86.67% and 80% farmer were access to extension service and had received training on Maize seed production.The majority of people followed Maize-Rice –wheat cropping pattern ranks first on the basis of index value(0.87).Insect/pests and diseases ranked at first as a major problem in maize seed production with (0.69) index value followed by lack of technical assistance,irregular field inspection,scarcity of input and loan unavailability .Similarly Maize stem borer and Bacterial stalk rot ranked at first as a major pests and diseases with (0.83) and (0.68) index value respectively.Similarly low volume of production ranked as a first major problem of marketing.Proper training,extension services and government support on inputs should be focus to enhance better socioeconomic condition and production of Maize.

The feasibility of an approximate irregular field dose distribution simulation program applied to a respiratory motion compensation system.

This study optimized our previously proposed simulation program for the approximate irregular field dose distribution (SPAD) and applied it to a respiratory motion compensation system (RMCS) and respiratory motion simulation system (RMSS). The main purpose was to rapidly analyze the two-dimensional dose distribution and evaluate the compensation effect of the RMCS during radiotherapy. This study modified the SPAD to improve the rapid analysis of the dose distribution. In the experimental setup, four different respiratory signal patterns were input to the RMSS for actuation, and an ultrasound image tracking algorithm was used to capture the real-time respiratory displacement, which was input to the RMCS for actuation. A linear accelerator simultaneously irradiated the EBT3 film. The gamma passing rate was used to verify the dose similarity between the EBT3 film and the SPAD, and conformity index (CI) and compensation rate (CR) were used to quantify the compensation effect. The Gamma passing rates were 70.48-81.39% (2%/2mm) and 88.23-96.23% (5%/3mm) for various collimator opening patterns. However, the passing rates of the SPAD and EBT3 film ranged from 61.85% to 99.85% at each treatment time point. Under the four different respiratory signal patterns, CR ranged between 21% and 75%. After compensation, the CI for 85%, 90%, and 95% isodose constraints were 0.78, 0.57, and 0.12, respectively. This study has demonstrated that the dose change during each stage of the treatment process can be analyzed rapidly using the improved SPAD. After compensation, applying the RMCS can reduce the treatment errors caused by respiratory movements.

Left ventricular four-dimensional blood flow energetics and vorticity in chronic myocardial infarction patients with/without left ventricular thrombus

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The British Heart Foundation [FS/10/62/28409] and Dutch ZonMw [104003001]. Background Left ventricular thrombus (LVT) formation is a frequent and serious complication of myocardial infarction (MI). How global LV flow characteristics are related to this phenomenon is yet uncertain. In this study, we investigated LV flow differences using 4D flow cardiovascular magnetic resonance (CMR) between chronic MI patients with LVT [MI-LVT(+)] and without LVT [MI-LVT(-)], and healthy controls. Methods In this prospective cohort study, the 4D flow CMR data were acquired in 19 chronic MI patients (MI-LVT(+), n= 9 and MI-LVT(-), n= 10) and 9 age-matched controls. All included subjects were in sinus rhythm. The following LV flow parameters were obtained: LV flow components (direct, retained, delayed, residual), mean and peak KE values (indexed to instantaneous LV volume), mean and peak vorticity values, and diastolic vortex ring properties (position, orientation, shape). Results The MI patients demonstrated a significantly larger amount of delayed and residual flow, and a smaller amount of direct flow compared to controls (p = 0.02, p = 0.03, and p < 0.001, respectively). The MI-LVT(+) patients demonstrated numerically increased residual flow and reduced retained and direct flow in comparison to MI-LVT(-) patients. Systolic mean and peak LV blood flow KE values were significantly lower in MI patients compared to controls (p = 0.04, p = 0.03, respectively). Overall, the mean and peak LV vorticity values were significantly lower in MI patients compared to controls. The mean vorticity at the basal level was significantly higher in MI-LVT(+) than in MI-LVT(-) patients (p < 0.01). The vortex ring core during E-wave in MI-LVT(-) group was located closer to the mitral annulus and in a less tilted orientation to the LV compared to MI-LVT(+) group (p = 0.05, p < 0.01, respectively). Conclusion Chronic MI patients with LVT express a different distribution of LV flow components, irregular vorticity vector fields, and altered diastolic vortex ring geometric properties as assessed by 4D flow CMR. Larger prospective studies are warranted to further evaluate these initial observations.