bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic model for an ensemble of interacting irradiation-induced defects in a macroscopic sample
Authors: Baraglia Federico , Ma Pui-Wai 
Published: December 2020

Abstract
We develop a dynamic model for the evolution of an ensemble of hundreds of interacting irradiation-induced mobile nanoscale defects in a micrometre size sample. The model uses a Langevin defect dynamics approach coupled to a finite element model, treated using the superposition method. The elastic field of each defect is described by its elastic dipole tensor, and the long-range interaction between defects is treated using the elastic Green’s function formalism. The approach circumvents the need to evaluate the elastic energy by means of volume integration, and provides a simple expression for the energy of elastic image interaction between the migrating defects and surfaces of the sample. We discuss the underlying theory, and also the parallelization and coarse-graining numerical algorithms that help speed up simulations. The model addresses the issue of imbalanced forces and moments arising as an artefact of the modified boundary problem associated with the traction free boundary condition. To illustrate applications of the method, we explore the dynamic evolution of an ensemble of interacting dislocation loops of various size and with different Burgers vectors, which proves the feasibility of performing large-scale simulations using the proposed model.
Dislocation precipitate bypass through elastically mismatched precipitates
Authors: Szajewski Benjamin A , Crone Joshua C , Knap Jaroslaw 
Published: December 2020

Abstract
The Orowan bypass mechanism for elastically homogeneous precipitates has been thoroughly studied. In engineering materials, alternate phased precipitates exhibit elastic moduli differing from the host matrix. To further our understanding of realistic dislocation precipitate interactions, we employ a three dimensional coupled discrete dislocation dynamics and finite element computational scheme to compute the Orowan bypass stress (τ
Orowan) required for a dislocation to bypass a row of elastically stiff precipitates. Specifically, we examine the influence of elastic mismatch between precipitates and the host matrix on τ
Orowan. Unique to our computational study, our simulations span a range of precipitate diameters (D), inner precipitate spacings (L), and an order of magnitude in precipitate-matrix elastic mismatch ratio. We partition observed increases in τ
Orowan into dislocation image stress interactions and additional stress concentrations due to the interaction of the applied stress with the elastically stiff precipitates. Finally, we incorporate the dependence of τ
Orowan on precipitate-matrix elastic mismatch into our derived model for τ
Orowan by introducing an effective D which depends explicitly on the elastic mismatch. Both our simulations and analyses suggest that strengthening due to relative increases in precipitate stiffness is modest compared to strengthening with precipitate width.
Unpacking structural domain of mathematics to aid inquiry in physics: a pilot study
Authors: Sokolowski Andrzej 
Published: December 2020

Abstract
Analysing graphs, formulating covariational relationships, and hypothesizing systems’ behaviour have emerged as frequent objectives of contemporary research in physics education. As such, these studies aim to help students achieve these objectives. While a consensus has been reached on the cognitive benefits of emphasizing the structural domain of mathematical apparatus in physics instruction, the question remains open on how to accomplish this task in school practice. This study contributes to this discussion. It attempts to determine how high-school physics students perceive formulas as a means to understand covariational relationships of natural phenomena. It also explores the hypothesis that including more structural domains of mathematics makes physics content more attractive for students. A sample of 25 advanced high-school physics students was taught kinematics, dynamics, and energy sections considering functional representations of some laws and principles traditionally covered in those sections. At the concluding phase, these students were invited to contrast formulas and their covariational embodiments as a means of providing conceptual understanding. The analysis revealed that students considered formulas as algebraic tools to attain a specific value to a particular application or carry out algebraic algorithms to solve a physics problem. They found formulas converted to covariational relationships a better fit for the learning of general phenomenon behaviour and extracting new information, especially from a graphical representation of these relationships. These findings generated the conclusion that the structural domain of mathematics can aid physics understanding by alternatively presenting formulas as mathematical entities that are transferrable to functions. It was further concluded that such parallelism would benefit not only the depth of inquiry in physics but also a general students’ STEM disposition.
Magnetic modeling of actively shielded rotating MRI magnets in the presence of environmental steel
Authors: Whelan Brendan , Leghissa Martino , Amrein Philipp , Zaitsev Maxim , Heinrich Bernhard , Fahrig Rebecca , Rohdjess Heiko 
Published: December 2020

Abstract
Rotating MRI systems could enable novel integrated medical devices such as MRI-Linacs, MRI-xray-angiography systems, and MRI-proton therapy systems. This work aimed to investigate the feasibility of rotating actively shielded superconducting MRI magnets in the presence of environmental steel—in particular, construction steel in the floor of the installation site. Two magnets were investigated: a 1.0 T split bore magnet, and a 1.5 T closed bore magnet. Each magnet was scaled to emulate field strengths of 0.5, 1.0, and 1.5 T. Finite Element Modeling was used to simulate these magnets in the presence of a 3 × 4 m steel plate located 1250 mm or 1400 mm below the isocenter. There are two possible rotation directions: around the longitudinal (z) axis or around the transverse (x) axis. Each model was solved for rotation angles between 0 and 360° in 30° intervals around each of these axes. For each simulation, a 300 mm DSV was extracted and decomposed into spherical harmonics. For the closed-bore magnet, total induced perturbation for the zero degree rotation angle was 223, 432, and 562 μT peak-to-peak (pk–pk) for the 0.5, 1.0, and 1.5 T models respectively (steel at 1250 mm). For the split-bore magnet, the same numbers were 1477, 16747, and 1766 μT. The substantially higher perturbation for the split-bore magnet can be traced to its larger fringe field. For rotation around the z-axis, total perturbation does not change as a function of angle but is exchanged between different harmonics. For rotation around the x-axis, total perturbation is different at each rotation angle. For the closed bore magnet, maximum perturbations occurred for a 90° rotation around the transverse axis. For the split-bore magnet, the opposite was observed, with the same 90° rotation yielding total perturbation lower than the conventional position. In all cases, at least 95% of the total perturbation was composed of 1st and 2nd order harmonics. The presence of environmental steel poses a major challenge to the realization of an actively shielded rotating superconducting MRI system, requiring some novel form of shimming. Possible shimming strategies are discussed at length.
Dynamics of ion beam emission in a low pressure plasma focus device
Authors: Lim Lian-Kuang , Yap Seong-Ling , Nee Chen-Hon , Yap Seong-Shan 
Published: December 2020

Abstract
The plasma that accelerates and compresses in the formation of the pinch in dense plasma focus devices has been found to be an abundant source of multiple radiations like ion beams and x-rays. In this work, the ion beam and x-ray emissions from a 2.7 kJ (13.5 kV, 30 µF) plasma focus device operated at pressure below 1 mbar were investigated. The time profile of the ion beam emission was analysed from the simultaneously measured ion beam, soft and hard x-ray signals using biased ion collectors, BPX 65 silicon PIN diode and a scintillator-photomultiplier tube assembly. Time resolved analysis of the emissions revealed that the emission of the ion beam corresponded to several different pinching instances. Two components of the ion beam were identified. An ion beam of lower energy but higher intensity was emitted followed by an ion beam of higher energy but lower intensity in the first plasma pinch. The ion beam emitted from the first plasma pinch also has higher energy than subsequent plasma pinches. The emission was found to be associated with the amplitude of voltage spike. The results from ion beam and electron beams suggest that they were emitted by the same localized electric field induced in the pinched plasma. The strongest plasma focus discharge indicated by sharp voltage spike of high amplitude and highest ion beam energy were both observed at 0.2 mbar. The average energy of the ion beam obtained is (53 ± 13) keV. At this optimum condition, the ions beam with the highest energy also led to the highest hard x-ray emission.
Particle scattering and resonances involving avoided crossing
Authors: Yang Yu Kun , Cheng Yongjun , Wu Yong , Qu Yi Zhi , Wang Jian Guo , Zhang Song Bin 
Published: December 2020

Abstract
In molecules, the nonadiabatic couplings between two adiabatic potentials build the avoided crossing (AC) region. The rovibronic resonances in the AC region of two-coupled potentials are very special, since they are not in the bound state region of the adiabatic potentials, and they usually do not play important roles on the scatterings and are less discussed. Exemplified in particle scattering, resonances in the AC region are comprehensively investigated. The effects of resonances in the AC region on the scattering cross sections strongly depend on the nonadiabatic couplings of the system, it can be very significant as sharp peaks, or inconspicuous buried in the background. More importantly, it shows a simple quantity proposed by Zhu and Nakamura (1992 J. Chem. Phys.
97 8497) to classify the coupling strength of nonadiabatic interactions, can be well applied to quantitatively estimate the importance of resonances in the AC region. Example applications of the quantity for real molecules (MgH, CO and OH) can well explain the evolutions of cross sections in the AC region published in the literatures. This work provides a simple and practical way to determine the candidate molecules when studying the resonances in the AC region.
X
0(2900) and its heavy quark spin partners in molecular picture *
Authors: Hu Mei-Wei , Lao Xue-Yi , Ling Pan , Wang Qian 
Published: December 2020

Abstract
The

, recently observed by the LHCb Collaboration in the

invariant mass of the

process, is the first exotic candidate with four different flavors, beginning a new era for the hadron community. Under the assumption that the

is a

hadronic molecule, we extracted the whole heavy-quark symmetry multiplet formed by the

doublet and the

meson. For the bound state case, there would be two additional

hadronic molecules associated with the

and

channels, as well as one additional

molecule. In the light quark limit, they are

and

below the

and

thresholds, respectively, which are unambiguously fixed by the mass position of the

. For the virtual state case, there would be one additional

hadronic molecule, strongly coupled to the

channel, and one additional

molecule. Searching for these heavy quark spin partners will help shed light on the nature of the

.
Chiral crossover characterized by Mott transition at finite temperature *
Authors: Mao Shijun 
Published: December 2020

Abstract
We discuss the proper definition for the chiral crossover at finite temperature, based on Goldstone's theorem. Different from the commonly used maximum change in chiral condensate, we propose defining the crossover temperature using the Mott transition of pseudo-Goldstone bosons, which, by definition, guarantees Goldstone's theorem. We analytically and numerically demonstrate this property in the frame of a Pauli-Villars regularized NJL model. In an external magnetic field, we find that the Mott transition temperature shows an inverse magnetic catalysis effect.
Compressional Alfvén eigenmodes excited by runaway electrons
Authors: Liu Chang , Brennan Dylan P. , Lvovskiy Andrey , Paz-Soldan Carlos , Fredrickson Eric D. , Bhattacharjee Amitava 
Published: December 2020

Abstract
Compressional Alfvén eigenmodes (CAEs) driven by energetic ions have been observed in magnetic fusion experiments. In this paper, we show that the modes can also be driven by runaway electrons formed in post-disruption plasma, which may explain kinetic instabilities observed in DIII-D disruption experiments with massive gas injection. The spatial structure is calculated, as are the frequencies which are in agreement with experimental observations. Using a runaway electron distribution function obtained from a kinetic simulation, the mode growth rates are calculated and found to exceed the collisional damping rate when the runaway electron density exceeds a threshold value. The excitation of CAEs poses a new possible approach to mitigate seed runaway electrons during the current quench and surpassing the avalanche.
Application of complex networks and indirect influences to non-forced migration
Authors: Catumba-Ruiz J , Redondo J M , Olivar G 
Published: December 2020

AbstractThe migration phenomena of human populations is a well-known issue in social, economic, and sociophysics studies. A common effect of non-forced migration is the fact that important cities gain population over the first years and become overpopulated. Therefore, neighboring cities receive all migration and end up geographically merging with the important ones. Several studies have addressed the social and economic reasons behind this effect, but a mathematical model has been lacking. Here, we construct a migration complex network with population and migration dynamics and carry out an indirect influences analysis of those dynamics. Using this, we can measure the effect of migration on population growth across cities. The results show that the analysis of the indirect influences reveals interesting facts about the mentioned migration effect and address the measurement of this. Given this, urban planners and city administrations can make use of these findings to improve their migratory research.
Trajectory-tracking control of a planar parallel robot using generalized predictive control with constraints
Authors: Rodelo M , Villa J L , Yime E 
Published: December 2020

Abstract
This paper presents the generalized predictive control with constraints, implemented to a planar parallel robot in order to calculate and track the desired trajectory of the end-effector of this robot. The manipulator is driven by three brushless direct current motors, and each one has an encoder to measure the velocity and rotation angles of the motors. Three constraints were considered to interact with the control law: control signal, terminal response and the over impulse constraints. The performance of the control law is evaluated in the simulation environment using Matlab/Simulink with the physic model developed through simscape multibody. The angular position and velocity errors for each of the three motors were calculated. Likewise, the output torques for each one were estimated. The results proved that the control law proposed with the constraints imposed for each motors has a good efficiency with a stable response time of the robot in performing the trajectory tracking, contributing to the scientific community a strategy of predictive optimization of control actions with multiple constraints applied on parallel robots.
Physical applications: fractional Brownian movement applied to the particle dispersion
Authors: Herrera Y , Prada D A , Ortega J , Sierra A , Acevedo A 
Published: December 2020

Abstract
Fractional Brownian motion allows you to see the correlation between past data increments in a shift with respect to future increments. Through this important physical property of fractional Brownian motion, it was possible to perform an analysis of the impact of suspended particles, also known as particulate matter, on the environment, which is a worldwide concern. The particulate matter produced in a coal mine is large and can be disastrous for neighboring communities, resulting in a decrease in their health and quality of life in general. In this work we analyze a time series of the values of total suspended particles registered by the “La Jagua” monitoring station located 5 km from the coal mine complex in the municipality of “La Jagua” de Ibrírico in Colombia, we do this by using the fractional Brownian motion calculated from Hurst’s coefficient to determine if there is persistence of the presence of this particulate material in the future. Initially a normality test is carried out, then the rescaled range and Hurst coefficient are computed with which it is possible to determine the increasing persistence and volatility of the series.
Development of a system based on aerial images for the morphological patterns classification using support vector machine
Authors: Montero D , Arenas W , Salinas S , Rueda C 
Published: December 2020

Abstract
Oil palm cultivation is one of the major agricultural activities in Colombia. Production performance is related to the good practices in the plantation, mainly regarding the management of phytosanitary conditions. Bud rot disease is the one with the greatest impact in Colombia. The most commonly used technique for its detection is from routine visual inspection on each palm, being costly and inefficient. For this reason, the aim of this study is the development of a classification algorithm based on binary support vector machines for the detection of Bud Rot. The model was obtained from 798 aerial images acquired by unmanned aerial vehicles. Each image was tagged by an expert palm grower based on the presence or absence of the disease. These images were described by 531 morphological features extracted using the concatenation of uniform binary local pattern vectors. Bootstrapping was used to balance the classes, obtaining 507 observations per class. To evaluate the performance metrics of the classifier, an 8-fold Monte Carlo cross-validation was implemented by randomly splitting the data set into training (80%), validation (10%), and test (10%) sets with balanced classes. Finally, the model achieved a performance greater than 96.0%. This indicates that the model developed could be a great technique to automate bud rot detection with high reliability, increasing the efficiency in the recognition. All these thanks to the fusion of Machine Learning techniques with the phenomena of optical physics.
Analysis of the atmospheric macro-physical using spatial methods
Authors: Andrades-Grassi J E , Cuesta-Herrera L , Torres-Mantilla H A , López-Hernández J Y 
Published: December 2020

Abstract
The central western area of Venezuela has an unequal distribution of precipitation. Due to its agricultural importance, is necessary to plan water accounting and this requires a evaluation of spatial and temporal variability of precipitation and an estimate of local geophysical effect from the relief. In this research we use an iterative computationally lattice approach to perform a confirmatory analysis of the variability and the spatial correlation structure in monthly precipitation stations. Spatial correlograms and pooled empirical semivariogram were applied to evaluate the most appropriate spatial weighting matrix to estimate the Moran’s I. The altitude effect over monthly rainfall was estimated through spatial regression algorithm which determine the predominant spatial process in each slice. A homogeneous spatial stochastic process with positive spatial autocorrelation is evidenced. There is a trend towards a higher frequency of spatial error and spatial auto-regressive processes between the months of June and August whilst there are not dominant process between October and December. This response is caused by the dynamics of the intertropical convergence zone, which generates a seasonal effect on precipitation. These estimations allows decision-making in modeling and will lead to an improvement for analysis and forecasting in areas strongly affected by climate change and water stress.
Geometry and measurement: specialized knowledge of future teachers within a pedagogical laboratory
Authors: Acevedo-Rincon J P 
Published: December 2020

Abstract
Based on the need to train teachers for the teaching of school mathematics, it is proposed to carry out a pedagogical laboratory, which allows monitoring successful practices of teachers within the university in order to promote teaching and research processes within the courses. This document aims to analyze the teaching and learning practices of prospective teachers in a didactic course of geometric and metric thinking. In this way, under a qualitative research perspective, the development of the laboratory is analyzed as a process developed in five stages: identification of the population, study of documents, identification of the mathematical object, planning, implementation and reflection and systematization of the experience. This article contributes mainly to the representation of phenomena and proposal of models of physics and natural sciences. One of the main conclusions proposes training for the teaching of school mathematics with real experiences given by natural contexts where pedagogical practices are carried out. From these practices, the reflections made by the students reveal the contributions of adequate planning of the classes for the success in the development of this, in addition to the security that these practices generate when taking classes from non-own courses.
Scientific competencies around the study of physics in secondary school students. A review of knowledge
Authors: Hernández-Suárez C A , Prada-Núñez R , Avendaño-Castro W R 
Published: December 2020

Abstract
This research seeks to analyze the degree of promotion and development of scientific competences based on the document Basic Standards of Competences in Natural Sciences proposed by the Ministerio de Educación Nacional, Colombia, specifically the competences associated with Physics. To this end, a twenty-item questionnaire is designed with a dichotomous response scale. The reliability analysis showed that the proposed scale had a good internal consistency regarding the measurement of scientific competences. The research adopts a quantitative descriptive approach based on the processing of data provided by 87 students from a private educational institution with emphasis on natural sciences in the city of San José de Cúcuta and enrolled between the ninth and eleventh grades. The results identify as a weakness in the teaching process, that teachers do not promote the use and articulation of diverse registers of semiotic representation of a set of data, a situation that limits the process of reasoning and resolution of problematic situations in everyday scenarios where the concepts of physics are present. Likewise, it was observed as a strength that teachers promote attitudinal skills in their students based on mutual respect, cooperative work and good communication. This type of research expands the knowledge that is available on the process of developing scientific competencies in the courses prior to entering higher education, so it is suggested to replicate this research process in students from different social contexts in order to improve the robustness of the questionnaire and provide valuable information to educational institutions on the design of improvement plans.