Irregular Field Research Articles

Noiseless regularisation by noise

We analyse the effect of a generic continuous additive perturbation to the well-posedness of ordinary differential equations. Genericity here is understood in the sense of prevalence. This allows us to discuss these problems in a setting where we do not have to commit ourselves to any restrictive assumption on the statistical properties of the perturbation. The main result is that a generic continuous perturbation renders the Cauchy problem well-posed for arbitrarily irregular vector fields. Therefore we establish regularisation by noise “without probability”.

Thermal interactions in large irregular fields of geothermal boreholes: the method of equivalent boreholes

A new method is presented to evaluate thermal interactions between vertical geothermal boreholes. The finite line source (FLS) solution is extended to consider thermal interactions between groups of boreholes. Groups of boreholes that share similar temperatures and heat extraction rates are identified using hierarchical agglomerative clustering, and each group is represented in the model as a single equivalent borehole. Each equivalent borehole is split into segments, and temporal and spatial superposition of the FLS solution are employed to calculate the total temperature change along the length of the equivalent boreholes. The new method is shown to provide an accurate calculation of the g-function, with a mean absolute percentage error below 0.612% on the g-functions of regular borefields of up to 144 boreholes using only 3 to 5 equivalent boreholes. Calculation times are significantly reduced: the g-function of a borefield of 1024 randomly positioned boreholes is calculated in 3.65 s.

Study on periodic orbit for the asteroid based on the dipole segment model

Asteroids are exist widely in the solar system, the study of orbital dynamics in the gravitational field of asteroids is helpful to reveal the origin and evolution of the solar system, and has potential scientific significance and engineering value. Due to the complex and irregular gravitational field characteristics of asteroids, there are abundant dynamic phenomena and mechanisms nearby, which also brings challenges to understanding the orbital dynamics and designing the periodic orbits for asteroids. In this paper, the dynamical model for the elongated asteroids is established. The model consists of a line segment and two point masses. The periodic orbits of the model are solved using the numerical technique of Poincare surface of section. The stability of the orbits is also calculated and analyzed. It is found that the shape and stability of periodic orbits are related to the islands on the Poincare map.

Performance and application of an evaluation method for flow conditioner based on CFD

As evaluation of the performance of flow conditioner mostly depends on the specific pipeline system, which cannot be timely feedback to improve the structure design, an evaluation method for flow conditioner based on computational fluid dynamics (CFD) is promoted. First, the evaluation coordinates for flow conditioner is established and the coordinate values of each sampling point are solved. Then, the judgment basis of whether the velocity distribution of pipe cross-section is fully developed is derived, and then come to the evaluation index of flow conditioner rectifier performance. Finally, with CFD simulation technology, the verified experiments of grid format flow conditioner are performed. The results showed that, the proposed evaluation method is qualified to evaluate the grid format flow conditioner’s performance quickly and effectively. Besides, it is helpful to analyze the function of flow conditioner’s performance on Reynolds numbers. What’s more, when 5.84 × 106≤Re≤5.84×108, the required minimum length of straight pipe for irregular downstream field of the grid format conditioner achieving fully developed is only 0.5-0.6 times by those without conditioner. It is of great significance to accelerate the flow conditioner designed and to promote fluid energy monitoring.

Can landscape level semi-natural habitat compensate for pollinator biodiversity loss due to farmland consolidation?

Traditional farming landscapes in China consist of small irregular fields with an intimately interspersed semi-natural habitat network of field margins, but are increasingly converted into consolidated ones that consist of standardized fields with reduced areas of field margins and other semi-natural habitat. It is unclear how such farmland consolidation influences pollinator communities, and if there is a negative effect, whether this effect is mitigated by semi-natural habitat present in the wider landscape. We compared the diversity and abundance of wild pollinators in oilseed rape fields that were embedded in landscapes that consisted either of traditional or consolidated farmland. The landscapes spanned a range of semi-natural habitat area from 10% to 73% at a scale of one km radius in Jiangxi Province, China. Pollinators were sampled using pan traps during two years (2015 and 2019). Results showed that pollinator diversity was positively associated with the proportion of semi-natural habitat in both traditional and consolidated farming landscapes, but was higher in traditional farming landscapes. In both years, there was no difference in pollinator abundance between landscapes with traditional and consolidated fields. The results indicate that the network of field margins in traditional farmland supports a diverse pollinator community, and that land consolidation has equivalent effects on pollinator diversity as substantial decreases in semi-natural habitat in the wider landscape. The role of semi-natural habitat in supporting farmland biodiversity and its associated services needs therefore to be considered in plans for farmland consolidation.

(Invited) Hydrogen-Substituted Graphdiyne Ion Tunnel Directing Concentration Redistribution for Commercial-Grade Dendrite-Free Zinc Anodes

Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging battery lifespans, minimum effort has been devoted to dendrite elimination in commercial-grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm-2). Additionally, new dilemmas regarding change of proton-storage behavior and interface pulverization have emerged in turn. Herein, hydrogen-substituted graphdiyne (HsGDY) with sub-ångström level ion tunnels and robust chemical stability was designed as an artificial interface layer to address these issues. This strategy prolonged the symmetric cell lifespan to >2400 h (100 days), which is 37-times larger than the one without protection (63 h). The simulation of dual-fields uncovered that HsGDY could redistribute the Zn2+ concentration field by spatially forcing Zn2+ to deviate from the irregular electric field. During practical use, the as-assembled full batteries delivered a long lifespan 50 000 cycles and remained stable even at a commercial-grade cathode loading mass of up to 22.95 mg cm-2. This HsGDY-protection methodology represents a great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.

Phase-resolved ocean wave forecast with ensemble-based data assimilation

Abstract

Evolvement of interpretation capacities of seismic measurements in mining of water-soluble minerals

The current development level of geophysical methods for mining monitoring of water-soluble mineral deposits provides opportunities to control the growing variety of potentially hazardous geological and mining conditions, to identify the critical states of rock mass and to monitor the emergency facilities. Seismic surveys for solving the specified problems have proven to be a highly informative method for studying the structural features and properties of productive and waterprotective overburden strata, which has a high information richness of the recorded data. The main set of parameters for the interpretation stage of seismic exploration has been formed based on the experience in shallow seismic surveys within a potash deposit; it incl udes the target reflection times, effective and interval velocities, amplitudes, frequencies and a number of derivatives from these parameters. Improvement and adaptation of world interpretation practices in relation to the indicated seismic studies conditions provides means for increasing reliability of anomalies identification and expanding the set of typical wave ‘images’ for various kinds of inhomogeneities in a wide range of wave field realizations and its attributes. The analysis of irregular wave field component in the results of scattered waves processing, spectral decomposition and RGB-mixing is considered as an additional techniques of qualitative interpretation. An approach is proposed to determining possible fracturing in rock mass based on the variability of interval velocities. In combination with the AVO-analysis, this approach makes it possible to assess the trend of rock disintegration within the emergency facilities. The interpretation results of the areal (quasi-3D) and spatial (3D) detailed surveys of a shallow potash deposit are presented.

On the statistical properties of inertia and drag forces in nonlinear multi-directional irregular water waves

Abstract

Statistical properties of wave kinematics in long-crested irregular waves propagating over non-uniform bathymetry

Experimental and numerical evidence have shown that nonuniform bathymetry may alter significantly the statistical properties of surface elevation in irregular wave fields. The probability of “rogue” waves is increased near the edge of the upslope as long-crested irregular waves propagate into shallower water. The present paper studies the statistics of wave kinematics in long-crested irregular waves propagating over a shoal with a Monte Carlo approach. High order spectral method is employed as wave propagation model, and variational Boussinesq model is employed to calculate wave kinematics. The statistics of horizontal fluid velocity can be different from statistics in surface elevation as the waves propagate over uneven bathymetry. We notice strongly non-Gaussian statistics when the depth changes abruptly in sufficiently shallow water. We find an increase in kurtosis in the horizontal velocity around the downslope area. Furthermore, the effects of the bottom slope with different incoming waves are discussed in terms of kurtosis and skewness. Finally, we investigate the evolution of kurtosis and skewness of the horizontal velocity over a sloping bottom in a deeper regime. The vertical variation of these statistical quantities is also presented.

Automated segmentation for whole human eye OCT image using RM multistage Mask R-CNN

Accurate segmentation of structures in whole human eye optical coherence tomography (OCT) images can improve the accuracy of disease diagnosis and ophthalmic biological parameter measurement. However, due to the complex features of the cornea, lens, and retina in the whole human eye OCT image and external interference, it is difficult to precisely extract the object features, which restricts the segmentation accuracy of whole human eye OCT images. A relation module (RM) multistage Mask Region-based Convolutional Neural Network (R-CNN) method for whole human eye OCT image segmentation is established. Based on Mask R-CNN, modulated deformable convolution is employed to produce an irregular receptive field and improve the adaptability of the network to the whole human eye OCT image’s object deformation. In the feature map extraction, the RM is combined to learn the position relation feature map of the human eye structures, which is utilized to enhance feature maps. A multistage mask is constructed in the segmentation branch, and the error is corrected through iterations of the mask to improve the segmentation accuracy of the whole human eye OCT image. Combined with the above structures, the RM multistage Mask R-CNN method is constructed for whole human eye OCT image segmentation. The model is trained by whole human eye OCT images and is applied to realize highly accurate whole human eye OCT image segmentation. Comparison experiments with K-means, U-net, and Feature Pyramid Networks (FPN)-deformable-mask R-CNN are performed to verify the segmentation accuracy and robustness of the proposed method to complex deformation and external interference.

A Novel Data Management Methodology and Case Study for Monitoring and Performance Analysis of Large-Scale Ground Source Heat Pump (GSHP) and Borehole Thermal Energy Storage (BTES) System

Aalto New Campus Complex (ANCC) is a recently inaugurated educational facility at Aalto University, located in Otaniemi (Espoo), Finland. Within over 40,000 m2, it comprises two faculties, a shopping center, recreational areas, and a metro station. ANCC is also a large-scale application of Ground Source Heat Pump (GSHP)–Borehole Thermal Energy Storage (BTES) in Finland, comprising an irregular BTES field of 74 boreholes with an overall length of roughly 23 km and 4 million m3 of energy storage. Therefore, accurate monitoring of the GSHP–BTES energy system is crucial for sustainable and efficient long-term operation. Due to the fundamental issues affecting the accuracy of all thermal energy meters, a novel methodology adjusting for consistency of the measured data (in order to accomplish daily energy balance on both sides of the GSHP) is developed. The proposed methodology is used also in conjunction with reconstruction of missing relevant data before April/May 2020 by applying linear regression techniques. The developed data management is considered essential due to its capability to handle measured data with high uncertainty (thermal meters) by using highly accurate data regarding the GSHP power demand. Additionally, operational data and relevant GSHP performance indicators for the 18-month period starting from July 2019 is presented and analyzed.

Numerical Evaluation of Screening Current-Induced Magnetic Field in No-Insulation REBCO Coil Systems

We have been developing a no-insulation (NI) REBCO coil which is expected to be applied to medical accelerators and magnetic resonance imaging as a technology that can achieve both high thermal stability and high current density. Due to the flat shape and much greater, than the thickness, width of a REBCO-coated conductor, the screening currents are remarkably induced by changing the magnetic flux that penetrates the tape vertically. For insulated (INS) coils, this screening current causes an irregular magnetic field (screening current-induced magnetic field (SCIF)). Also, in the NI coil, an excitation delay occurs because of the current flowing in the radial direction with coil excitation. Therefore, as the cause of irregular magnetic field, it is necessary to simultaneously consider the influence of both the excitation delay and SCIF. In this study, we numerically investigate the magnetic field in the NI coil. The SCIF and an excitation delay reduce magnetic accuracy in the NI coil. Thus, we propose an energization waveform that can improve the magnetic field accuracy even if there is an excitation delay. Besides, we verified its effectiveness.

Numerical Evaluation of Screening Current-Induced Magnetic Field Considering Variable Output Energy in REBCO Coil System of Skeleton Cyclotron for Cancer Therapy

We have been developing a new-generation accelerator named “Skeleton Cyclotron”, which is an ultra-compact and high-intensity accelerator for the stable production of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">211</sup> At used for targeted alpha-particle therapy. Coil system for Skeleton Cyclotron consists of circular and noncircular high-temperature superconducting magnets and it can cause the output energy to vary without being bounded by the non-linearity of the iron core. This will enable not only the production of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">211</sup> At, but also the production of radioisotopes for positron emission tomography and neutron irradiation for boron neutron capture therapy with a single accelerator. A high-precision magnetic field distribution and a high temporal stability are required for stable beam acceleration, but the screening current, which is induced in the REBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> (REBCO, RE: Rare Earth) coated conductor, generates an irregular magnetic field and deteriorates the quality of the magnetic field spatially and temporally. In this study, we numerically evaluated the temporal stability and reproducibility of the screening current-induced field considering the variable energy operation for the Ultra-Baby Skeleton Cyclotron, which is a small demonstration model of Skeleton Cyclotron.

Transfers around Phobos via bifurcated retrograde orbits: Applications to Martian Moons eXploration mission

Quasi-satellite or distant retrograde orbits are stable orbits in the restricted three-body problem will be used in remote planetary satellite missions like JAXA’s Martian Moons eXploration (MMX). Due to Phobos’ irregular gravity field, the proximity operations of the MMX mission require sophisticated techniques for transfers and maintenance between different quasi-satellite orbits. This paper focuses on the design of transfer trajectories between Quasi-Satellite Orbits (QSO) around Phobos. We utilize horizontal bifurcated Multi-Revolution Periodic QSOs (MP-QSOs) that are found in the vicinity of an ellipsoidal Phobos under the assumptions of the circular Hill Problem. Transfer strategy via MP-QSOs is explored through transfer maps that illustrate transfer design space between different altitudes QSOs. It is found that transfers via MP-QSOs provide insights on minimum ΔV transfers and the parameters determining the transfer cost. The proposed transfer method is explicitly applied to MMX baseline QSOs. This research has identified that transfers between high(100 × 200 km)-to-mid(50 × 100 km), mid-to-low(30 × 50 km), and lower altitude(<30 km) QSOs via MP-QSOs can be achieved with as low as 11.63 m/s, 3.99 m/s, 1.74 m/s, and 0.97 m/s, respectively.

Source apportionment in PM2.5 in central Japan using positive matrix factorization focusing on small-scale local biomass burning

Here, we discuss the influences of small-scale biomass burning (BB) originating from local/regional emissions, such as agricultural waste burning, which are difficult to detect via remote sensing. To evaluate the BB contribution, we used a positive matrix factorization (PMF) model with chemical component data including levoglucosan, a useful BB indicator, at multiple urban, suburban, and background sites in central Japan during two weeks in October and November of 2014 and January and February of 2015. High levoglucosan concentrations were observed not only at the suburban sites but also at the urban sites. At the background site located downwind of Northeast China, the levoglucosan concentrations were elevated when air masses were transported from Northeast China, where fire spots were detected. Meanwhile, at the other sites, small-scale local or regional BB emissions prevailed, and fire spots were rarely detected. At these sites, the levoglucosan levels were high although the relevant air masses did not originate in Northeast China. The source apportionment results demonstrated that in fall, BB was a significant source of particulate matter with diameters of less than 2.5 μm (PM2.5), organic carbon, and elemental carbon at all sites. Notably, the BB contributions to PM2.5 were higher at an urban site located near farmland than at other urban sites in fall and winter. Our results indicate that specific BB emission sources, such as local, small, and irregular open field burning, impact the air quality not only at suburban areas but also at urban areas in central Japan.

Correlation Between Average Segment Width and Gamma Passing Rate as a Function of MLC Position Error in Volumetric Modulated Arc Therapy.

Objective:This study analyzed the correlation between the average segment width (ASW) and gamma passing rate according to the multi-leaf collimator (MLC) position error.Method:To evaluate the changes in the gamma passing rate according to the MLC position error, 21 volumetric modulated arc therapy (VMAT) plans were generated using pelvic lymph node metastatic prostate cancer patient's data which is sensitive to MLC position errors as they involve several long, narrow, irregular fields. The ASW for each VMAT plan was calculated using our own code developed using Visual Basic for Applications (VBA). The gamma passing rate of the VMAT plan according to the MLC position error was evaluated using ArcCHECK (Sun Nuclear, Melbourne, FL, USA) while inducing symmetric MLC position errors in 0.25 mm intervals from −1 mm to +1 mm in the infinity medical linear accelerator (Elekta AB, Stockholm, Sweden). Finally, we examined the correlation between the change in the passing rate () due to the MLC position error and the ASW in VMAT through linear regression analysis using the least squares method.Results:The ASW and were found to have a linear correlation according to the MLC position error, and the coefficient of determination was 0.88. For a 1 mm position error of MLC in VMAT, the gamma passing rate improved by approximately 11.9% as the ASW increased by 10 mm.Conclusion:These results are expected to be employed as guidelines to minimize the dose uncertainty due to MLC position error in VMAT.

Stress-oriented 3D printing path optimization based on image processing algorithms for reinforced load-bearing parts

Fibre reinforced filament fabrication is a potential additive manufacturing method for certain load-bearing parts in aerospace and automotive products. In current practice, printing paths are planned from part geometry without considering loading conditions. This paper presents a new method for optimizing printing paths to align with the principal stress field of parts in use. Because of the powerful processing capabilities, for the first time grayscale image was adopted to represent the irregular vector field, which can be robustly processed into sub-regions for generating regular printing paths. Preliminary bending test achieved promising increase in tensile strength compared with conventional methods.

Reflection on inactive and energetic survey of sandwich synthesized glazed layers

Right now, study the material and geometric vulnerability consequences for the static, free vibration and dynamic conduct of sandwich shaft structures. A higher-request sandwich board hypothesis is considered for the examination. The flexible properties of the sandwich pillar are considered as 1-D non -Gaussian irregular field which causes neighborhood variety in mass and firmness frameworks of the shaft. The discretization of the non-Gaussian irregular fields is performed utilizing the development ideal direct estimation. To play out the numerical investigation, Monte-Carlo reproduction alongside the computationally proficient time-space ghastly component technique is proposed. Numerical outcomes are acquired for various limit conditions just as for various materials in the sandwich face sheet and center. Results got right now the impacts of material and geometric vulnerability in the reaction conduct of a sandwich shaft. The individual impact of center thickness and Poisson's proportion of the center on the static, free vibration and dynamic reaction is measured. It is seen that the vulnerabilities in material and geometric properties alongside stacking and limit conditions impact the static, free vibration and dynamic reaction.

Higher-order Spectral Method for Regular and Irregular Wave Simulations

In this study, a nonlinear wave simulation code is developed using a higher-order spectral (HOS) method. The HOS method is very efficient because it can determine the solution of the boundary value problem using fast Fourier transform (FFT) without matrix operation. Based on the HOS order, the vertical velocity of the free surface boundary was estimated and applied to the nonlinear free surface boundary condition. Time integration was carried out using the fourth order Runge–Kutta method, which is known to be stable for nonlinear free-surface problems. Numerical stability against the aliasing effect was guaranteed by using the zero-padding method. In addition to simulating the initial wave field distribution, a nonlinear adjusted region for wave generation and a damping region for wave absorption were introduced for wave generation simulation. To validate the developed simulation code, the adjusted simulation was carried out and its results were compared to the eighth order Stokes theory. Long-time simulations were carried out on the irregular wave field distribution, and nonlinear wave propagation characteristics were observed from the results of the simulations. Nonlinear adjusted and damping regions were introduced to implement a numerical wave tank that successfully generated nonlinear regular waves. According to the variation in the mean wave steepness, irregular wave simulations were carried out in the numerical wave tank. The simulation results indicated an increase in the nonlinear interaction between the wave components, which was numerically verified as the mean wave steepness. The results of this study demonstrate that the HOS method is an accurate and efficient method for predicting the nonlinear interaction between waves, which increases with wave steepness.