bluuebunny/crossref_metadata_2025 huggingface dataset:
Terahertz interface physics: from terahertz wave propagation to terahertz wave generation
Authors: Du Wanyi , Huang Yuanyuan , Zhou Yixuan , Xu Xinlong
Published: December 2021

Terahertz (THz) interface physics as a new interdiscipline between the THz technique and condensed matter physics has undergone rapid development in recent years. In particular, the development of advanced materials, such as graphene, transitional metal dichalcogenides, topological insulators, ferromagnetic metals, and metamaterials, has revolutionized the interface field and further promoted the development of THz functional devices based on interface physics. Moreover, playing at the interface of these advanced materials could unveil a wealth of fascinating physical effects such as charge transfer, proximity effect, inverse spin-Hall effect, and Rashba effect with THz technology by engineering the charge, spin, orbit, valley, and lattice degrees of freedom. In this review, we start with a discussion of the basic theory of THz interface physics, including interface formation with advanced materials, THz wave reflection and transmission at the interface, and band alignment and charge dynamics at the interface. Then we move to recent progress in advanced materials from THz wave propagation to THz wave generation at the interface. In THz wave propagation, we focus on THz wave impedance-matching, Goos–Hänchen and Imbert–Fedorov shifts in THz region, interfacial modulation and interfacial sensing based on THz waves. In THz wave generation, we summarize ongoing coherent THz wave generation from van der Waals interfaces, multiferroic interfaces, and magnetic interfaces. The fascinating THz interface physics of advanced materials is promising and promotes novel THz functional devices for manipulating propagation and generation of THz waves at interfaces.
Dynamically tunable plasmon-induced transparency effect based on graphene metasurfaces
Authors: Chen Shuxian , Li Junyi , Guo Zicong , Chen Li , Wen Kunhua , Xu Pengbai , Yang Jun , Qin Yuwen
Published: December 2021

Plasmon-induced transparency (PIT) is theoretically explored for a graphene metamaterial using finite-difference time-domain numerical simulations and coupled-mode-theory theoretical analysis. In this work, the proposed structure consists of one rectangular cavity and three strips to generate the PIT phenomenon. The PIT window can be regulated dynamically by adjusting the Fermi level of the graphene. Importantly, the modulation depth of the amplitude can reach 90.4%. The refractive index sensitivity of the PIT window is also investigated, and the simulation results show that a sensitivity of 1.335 THz RIU−1 is achieved. Additionally, when the polarization angle of the incident light is changed gradually from 0° to 90°, the performance of the structure is greatly affected. Finally, the proposed structure is particularly enlightening for the design of dynamically tuned terahertz devices.
Quantitative investigation of polarization-dependent photocurrent in ferroelectric thin films
Authors: Rani Komalika , Matzen Sylvia , Gable Stéphane , Maroutian Thomas , Agnus Guillaume , Lecoeur Philippe
Published: December 2021

Ferroelectric thin films are investigated for their potential in photovoltaic (PV) applications, owing to their high open-circuit voltage and switchable photovoltaic effect. The direction of the ferroelectric polarization can control the sign of the photocurrent through the ferroelectric layer, theoretically allowing for 100% switchability of the photocurrent with the polarization, which is particularly interesting for photo-ferroelectric memories. However, the quantitative relationship between photocurrent and polarization remains little studied. In this work, a careful investigation of the polarization-dependent photocurrent of epitaxial Pb(Zr, Ti)O3 thin films has been carried out, and has provided a quantitative determination of the unswitchable part of ferroelectric polarization. These results represent a systematic approach to study and optimize the switchability of photocurrent, and more broadly to get important insights on the ferroelectric behavior in all types of ferroelectric layers in which pinned polarization is difficult to investigate.
Low magnetic-field induced high temperature dynamic magnetoelectric coupling performances in Z-type Sr3Co2Fe24O41
Authors: Li Jun , Zhao Dongpeng , Bai Han , Yuan Zhi , Zhou Zhongxiang
Published: December 2021

Magnetic-field induced dynamic magnetoelectric coupling effects and polarization performance of Z-type Sr3Co2Fe24O41 (SCFO) ceramic has been investigated. Results found that SCFO’s transverse tapered magnetic structure can induce electric polarization, and its electric polarization direction will not change under external magnetic effects. First-order dynamic magnetoelectric coupling coefficient (α) and second-order dynamic magnetoelectric coupling coefficient (β) of SCFO exhibited strong response main in magnetic structural phase transition region. The magnetoelectric structural phase transition position appeared in low magnetic field, and the magnetic moment vector and its corresponding electric polarization vector of SCFO exhibited the most unstable state near its equilibrium position, which is beneficial for inducing strong dynamic magnetoelectric coupling response. When the applied magnetic fields to SCFO increased, the magnetic moment stability near the equilibrium position increased, and the dynamic magnetoelectric coupling response decreased. Results showed that the dynamic magnetoelectric coupling response of SCFO can bear T
1 = 370 K high temperature. The dynamic magnetoelectric coupling response induced by low magnetic fields in SCFO contributes to its actual application in next generation magnetoelectric information storage devices.
Uncertainty quantification for aerodynamic pressure probes, using adaptive quasi-Monte Carlo
Authors: Chasoglou A C , Tsirikoglou P , Kalfas A I , Abhari R S
Published: December 2021

In the present study, an adaptive randomized Quasi Monte Carlo methodology is presented, combining Stein’s two-stage adaptive scheme and Low Discrepancy Sobol sequences. The method is used for the propagation and calculation of uncertainties related to aerodynamic pneumatic probes and high frequency fast response aerodynamic probes (FRAP) in the subsonic flow regime,

0.15
⩽
M
⩽
0.7

. The use of the proposed methodology allows the fast and accurate, in a probabilistic sense, calculation of uncertainties, ensuring that the total number of Monte Carlo (MC) trials is kept low based on the desired numerical accuracy. Thus, the method is well-suited for aerodynamic pressure probes, where multiple points need to be evaluated in their calibration space. Complete and detailed measurement models are presented for both a pneumatic probe and FRAP. The models are segregated in sub-problems that allow the evaluation and inspection of intermediate steps of MC in a transparent manner, also enabling the calculation of the relative contributions of the elemental uncertainties on the measured quantities. The adaptive scheme is implemented with a block-to-block evaluation, which accelerates the calculation of statistical parameters. Various, commonly-used sampling techniques for MC simulation and different adaptive MC schemes are compared, using both theoretical toy distributions and actual examples from aerodynamic probes’ measurement models. The robustness of Stein’s two-stage scheme is demonstrated even in cases when significant deviation from normality is observed in the underlying distribution of the output of the MC. With regards to FRAP, two issues related to piezo-resistive sensors are addressed, namely temperature dependent pressure hysteresis and temporal sensor drift, and their uncertainties are accounted for in the measurement model. These effects are the most dominant factors, affecting all flow quantities’ uncertainties, with significance that varies mainly with M and operating temperature. This work highlights the need to construct accurate and detailed measurement models for aerodynamic probes, that otherwise will result in significant underestimation (routinely in excess of 50

%

) of the final uncertainties.
A boundary division guiding synchrosqueezed wave packet transform method for rolling bearing fault diagnosis
Authors: Pang Bin , Zhang Heng , Sun Zhenduo , Yan Xiaoli , Li Chunhua , Tang Guiji
Published: December 2021

Synchrosqueezed wave packet transform (SSWPT) can effectively reconstruct the band-limited components of the signal by inputting the specific reconstructed boundaries, and it provides an alternative bearing fault diagnosis method. However, the selection of reconstructed boundaries can significantly affect the fault feature extraction performance of SSWPT. Accordingly, this paper presents a boundary division guiding SSWPT (BD-SSWPT) method. In this method, an adaptive boundary division method is developed to effectively determine the reconstructed boundaries of SSWPT. Firstly, the marginal spectrum of SSWPT, more robust to noise than the Fourier spectrum, is defined for the scale-space division to obtain the initial boundaries. Secondly, the inverse transform of SSWPT is conducted based on the initial boundaries to obtain the initial reconstructed components. Thirdly, a boundary redefinition scheme, composed of clustering and combination, is conducted to redefine the boundaries. Finally, the potential components are extracted by the inverse transform of SSWPT based on the redefined boundaries. The validity of BD-SSWPT is verified by simulated and experimental analysis, and the superiority of BD-SSWPT is highlighted through comparison with singular spectrum decomposition (SSD) and an adaptive parameter optimized variational mode decomposition (AVMD). The results demonstrate that BD-SSWPT identifies more significant fault features and has higher computational efficiency than SSD and AVMD.
Dislocation evolution during additive manufacturing of tungsten
Authors: Cui Yinan , Li Kailun , Wang Chan , Liu Wei
Published: December 2021

Additive manufacturing (AM) frequently encounters part quality issues such as geometrical inaccuracy, cracking, warping, etc. This is associated with its unique thermal and mechanical cycling during AM, as well as the material properties. Although many efforts have been spent on this problem, the underlying dislocation evolution mechanism during AM is still largely unknown, despite its essential role in the deformation and cracking behavior during AM and the properties of as-fabricated parts. In this work, a coupling method of three-dimensional dislocation dynamics and finite element method is established to disclose the mechanisms and features of dislocations during AM. Tungsten (W) is chosen as the investigated material due to its wide application. The internal thermal activated nature of dislocation mobility in W is taken into account. The correlations between the combined thermal and mechanical cycles and dislocation evolutions are disclosed. The effect of adding alloying element Ta in W is discussed from the perspectives of tuning dislocation mobility and introducing nanoparticles, which helps to understand why higher dislocation density and fewer microcracks are observed when adding Ta. The current work sheds new light on the long-standing debating of dislocation origin and evolutions in the AM field.
Nanoscale self-assembly: concepts, applications and challenges
Authors: Amadi Eberechukwu Victoria , Venkataraman Anusha , Papadopoulos Chris
Published: December 2021

Self-assembly offers unique possibilities for fabricating nanostructures, with different morphologies and properties, typically from vapour or liquid phase precursors. Molecular units, nanoparticles, biological molecules and other discrete elements can spontaneously organise or form via interactions at the nanoscale. Currently, nanoscale self-assembly finds applications in a wide variety of areas including carbon nanomaterials and semiconductor nanowires, semiconductor heterojunctions and superlattices, the deposition of quantum dots, drug delivery, such as mRNA-based vaccines, and modern integrated circuits and nanoelectronics, to name a few. Recent advancements in drug delivery, silicon nanoelectronics, lasers and nanotechnology in general, owing to nanoscale self-assembly, coupled with its versatility, simplicity and scalability, have highlighted its importance and potential for fabricating more complex nanostructures with advanced functionalities in the future. This review aims to provide readers with concise information about the basic concepts of nanoscale self-assembly, its applications to date, and future outlook. First, an overview of various self-assembly techniques such as vapour deposition, colloidal growth, molecular self-assembly and directed self-assembly/hybrid approaches are discussed. Applications in diverse fields involving specific examples of nanoscale self-assembly then highlight the state of the art and finally, the future outlook for nanoscale self-assembly and potential for more complex nanomaterial assemblies in the future as technological functionality increases.
Quantum computing for classical problems: variational quantum eigensolver for activated processes
Authors: Pravatto Pierpaolo , Castaldo Davide , Gallina Federico , Fresch Barbara , Corni Stefano , Moro Giorgio J
Published: December 2021

The theory of stochastic processes impacts both physical and social sciences. At the molecular scale, stochastic dynamics is ubiquitous because of thermal fluctuations. The Fokker–Plank–Smoluchowski equation models the time evolution of the probability density of selected degrees of freedom in the diffusive regime and it is, therefore, a workhorse of physical chemistry. In this paper we report on the development and implementation of a variational quantum eigensolver to solve the Fokker–Planck–Smoluchowski eigenvalue problem. We show that such an algorithm, typically adopted to address quantum chemistry problems, can be effectively applied to classical systems, paving the way to new applications of quantum computers. We compute the conformational transition rate in a linear chain of rotors with nearest-neighbour interactions. We provide a method to encode the probability distribution for a given conformation of the chain on a quantum computer and assess its scalability in terms of operations. A performance analysis on noisy quantum emulators and quantum devices (IBMQ Santiago) is provided for a small chain which shows results in good agreement with the classical benchmark without any further addition of error mitigation techniques.
Identify spin property of relativistic electrons in fully relativistic laser fields
Authors: Li X B , Gan L F , Wang J , Jiao J L , Jin S , Zhuo H B , Zhou C T , Zhu S P , He X T , Qiao B
Published: December 2021

A semiclassical method is developed to study the spin evolution of a relativistic electron in an fully relativistic laser pulse. Different from the previous classical method which is based on the direct generalization of nonrelativistic spin precession equation, we perform first-principle calculations on the mean values of various spin operators with respect to a relativistic electron wave packet. It is demonstrated, via theoretical derivation and numerical simulation, that although the Foldy–Wouthuysen operator merits the single-particle interpretation, its mean value obviously deviates from the result of the classical method, which sheds light on not only the understanding of relativistic spin itself but also broad related applications. To achieve a direct observation of such effect, a feasible experimental setup utilizing the asymmetric field of a single-cycle laser is proposed. In such geometry, the deviation is evidenced in the total change of spin which can be easily measured after the interaction.
Multiple Fano resonances based on clockwork spring-shaped resonator for refractive index sensing
Authors: Ding Jinghui , Qi Yunping , Yuan Yujiao , Chen Haowen , Liu Weiming , Jia Yingjun , Wang Xiangxian
Published: December 2021

A surface plasmon polarized structure consisting of two metal-insulator-metal (MIM) waveguide coupled with clockwork spring-shaped resonators are constructed in this paper, and its geometric parameters are controlled within a few hundred nanometers. The finite element method (FEM) and multimode interference coupled mode theory (MICMT) are used to simulate and theoretically calculate the optical response of the designed structure. By modifying the structural parameters of the system, the influence on the asymmetry of the Fano resonance line is studied. The changes of the transmission spectra at different refractive indexes are also investigated. Based on this asymmetric resonant line, the sensitivity and FOM* (figure of merit) value of the cavity with different parameters are measured. The sensitivity and FOM* under the best parameters are 1200 nm RIU−1 and 191.6, respectively. The surface plasmon structure proposed and the results in this paper are promising for applications in the field of high-performance sensing and micro-nano optical devices.
Anti-function solution of uniaxial anisotropic Stoner–Wohlfarth model
Authors: Zheng Kun , Miao Yu , Li Tong , Yang Shuang-Long , Xi Li , Yang Yang , Zhao Dun , Xue De-Sheng
Published: December 2021

The anti-trigonometric function is used to strictly solve the uniaxial anisotropic Stoner–Wohlfarth (SW) model, which can obtain the relation of the angle α(θ) between the magnetization (the anisotropy field) and the applied magnetic field. Using this analytic solution, the hysteresis loops of uniaxial anisotropic SW particles magnetized in typical directions could be numerically calculated. Then, the hysteresis loops are obtained in randomly distributed SW particle ensembles while ignoring the dipole interaction among them with the analytic solution. Finally, the correctness of the analytic solution is verified by the exact solutions of remanence, switching field, and coercivity from the SW model. The analytic solution provides an important reference for understanding the magnetizing and magnetization reversal processes of magnetic materials.
Relativistic motion on Gaussian quantum steering for two-mode localized Gaussian states
Authors: Gong Xiao-Long , Cao Shuo , Fang Yue , Liu Tong-Hua
Published: December 2021

Realistic quantum systems always exhibit gravitational and relativistic features. In this paper, we investigate the properties of Gaussian steering and its asymmetry by the localized two-mode Gaussian quantum states, instead of the traditional single-mode approximation method in the relativistic setting. We find that the one-side Gaussian quantum steering will monotonically decrease with increasing observers of acceleration. Meanwhile, our results also reveal the interesting behavior of the Gaussian steering asymmetry, which increases for a specific range of accelerated parameter and then gradually approaches to a finite value. Such finding is well consistent and explained by the well-known Unruh effect, which could significantly destroy the one-side Gaussian quantum steering. Finally, our results could also be applied to the dynamical studies of Gaussian steering between the Earth and satellites, since the effects of acceleration are equal to the effects of gravity according to the equivalence principle.
Vortex chains induced by anisotropic spin–orbit coupling and magnetic field in spin-2 Bose-Einstein condensates
Authors: Zhu Hao , Yin Shou-Gen , Liu Wu-Ming
Published: December 2021

We investigate the anisotropic spin–orbit coupled spin-2 Bose–Einstein condensates with Ioffe–Pritchard magnetic field. With nonzero magnetic field, anisotropic spin–orbit coupling will introduce several vortices and further generate a vortex chain. Inside the vortex chain, the vortices connect to each other, forming a line along the axis. The physical nature of the vortex chain can be explained by the particle current and the momentum distribution. The vortex number inside the vortex chain can be influenced via varying the magnetic field. Through adjusting the anisotropy of the spin–orbit coupling, the direction of the vortex chain is changed, and the vortex lattice can be triggered. Moreover, accompanied by the variation of the atomic interactions, the density and the momentum distribution of the vortex chain are affected. The realization and the detection of the vortex chain are compatible with current experimental techniques.
Spin and spin–orbit coupling effects in nickel-based superalloys: A first-principles study on Ni3Al doped with Ta/W/Re
Authors: Liu Liping , Cao Jin , Guo Wei , Wang Chongyu
Published: December 2021

Heavy elements (X = Ta/W/Re) play an important role in the performance of superalloys, which enhance the strength, anti-oxidation, creep resistance, and anti-corrosiveness of alloy materials in a high-temperature environment. In the present research, the heavy element doping effects in FCC-Ni(γ) and Ni3Al(γ′) systems are investigated in terms of their thermodynamic and mechanical properties, as well as electronic structures. The lattice constant, bulk modulus, elastic constant, and dopant formation energy in non-spin, spin polarized, and spin–orbit coupling (SOC) calculations are compared. The results show that the SOC effects are important in accurate electronic structure calculations for alloys with heavy elements. We find that including spin for both γ and γ′ phases is necessary and sufficient for most cases, but the dopant formation energy is sensitive to different spin effects, for instance, in the absence of SOC, even spin-polarized calculations give 1% to 9% variance in the dopant formation energy in our model. Electronic structures calculations indicate that spin polarization causes a split in the metal d states, and SOC introduces a variance in the spin-up and spin-down states of the d states of heavy metals and reduces the magnetic moment of the system.
Cluster decay half-lives using asymmetry dependent densities
Authors: Dehghani V. , Alavi S. A. , Razavi R. , Soylu A. , Koyuncu F.
Published: December 2021

By adopting different neutron and proton density distributions, cluster decay half-lives were investigated using double-folding potentials with constant and nuclear asymmetry dependent sets of nuclear density parameters. Two adopted asymmetry dependent sets of parameters were fitted based on microscopic calculations, and they were calculated based on the neutron skin/halo-type nuclei assumption and by employing experimental rms charge radii. A bulk agreement between theory and experiment was obtained for all sets of parameters using a calculated cluster preformation probability. Few differences were observed between the skin and halo-type assumptions. However, the notable role of the asymmetry parameter was observed in the relatively large differences between the skin and skin-type with zero thickness.
Optimizing a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear
Authors: Liang Liyan , Bin Guangyu , Chen Xiaogang , Wang Yijun , Gao Shangkai , Gao Xiaorong
Published: December 2021

Objective. Steady-state visual evoked potential (SSVEP) based brain–computer interface (BCI) has the characteristics of fast communication speed, high stability, and wide applicability, thus it has been widely studied. With the rapid development in paradigm, algorithm, and system design, SSVEP-BCI is gradually applied in clinical and real-life scenarios. In order to improve the ease of use of the SSVEP-BCI system, many studies have been focusing on developing it on the hairless area, but due to the lack of redesigning the stimulation paradigm to better adapt to the new area, the electroencephalography response in the hairless area is worse than occipital region. Approach. This study first proposed a phase difference estimation method based on stimulating the left and right visual field separately, then developed and optimized a left and right visual field biphasic stimulation paradigm for SSVEP-based BCIs with hairless region behind the ear. Main results. In the 12-target online experiment, after a short model estimation training, all 16 subjects used their best stimulus condition. The paradigm designed in this study can increase the proportion of applicable subjects for the behind-ear SSVEP-BCI system from 58.3% to 75% and increase the accuracy from 74.6 ± 20.0% (the existing best SSVEP stimulus with hairless region behind the ear) to 84.2

±

14.7%, and the information transfer rate from 14.2

±

6.4 bits min−1 to 17.8

±

5.7 bits min−1. Significance. These results demonstrated that the proposed paradigm can effectively improve the BCI performance using the signal from the hairless region behind the ear, compared with the standard SSVEP stimulation paradigm.
Ion heating and energy balance during magnetic reconnection events in the RFX-mod experiment
Authors: Gobbin M. , Agostini M. , Auriemma F. , Carraro L. , Cavazzana R. , Fassina A. , Franz P. , Marrelli L. , Momo B. , Piovan R. , Predebon I. , Puiatti M.E. , Spizzo G. , Terranova D. , Zuin M. , RFX-mod Team
Published: December 2021

Reconnection events in high current reversed field pinch plasmas are often associated to the partial or total loss of the helical magnetic topology. The electron temperature collapse during these phenomena is investigated in RFX-mod thanks to high time resolution soft-x-ray diagnostics; these data are used, together with magnetic energy reconstructions, for energy balance analysis. The paper shows that the energy released during reconnection events, similarly to astrophysical plasmas, might be involved in ion heating, the latter being estimated by the energy distribution function of neutral atoms, a rather interesting feature in a reactorial perspective. These issues will be further investigated in RFX-mod2 , an upgrade of the present device starting its operations from 2022, where the modified boundary conditions are expected to increase the helical states duration and reduce the frequency of reconnection events.
Simulating energetic particle losses in JET plasmas with a reverse integration biasing scheme
Authors: Bonofiglo P.J. , Podestà M. , White R.B. , Kiptily V. , Goloborodko V. , Gorelenkov N.N. , Vallar M. , Cecil F.E. , Giroud C. , Brezinsek S. , JET Contributors
Published: December 2021

An integrated energetic particle transport model has been constructed in JET plasmas constrained by experimental fast ion loss measurements. The model incorporates a synthetic fast ion loss detector identical to JET’s thin-foil Faraday cup fast ion loss detector array. The loss model combines analyses from the TRANSP and ORBIT-kick codes with enhanced features for producing the synthetic diagnostic. Extensions to the ORBIT code framework allow a full-orbit representation within the vacuum region that can map particles directly to an installed detector geometry. Since synthetic fast ion loss detectors are plagued by weak loss statistics, a novel reverse integration biasing scheme has been implemented to boost computational efficiency. The model is validated against experimental loss measurements induced by long-lived kink modes and is found to be in good agreement. This confirms the development of a fully integrated transport/loss model which can be quantitatively verified against experiment allowing for future validation and predictive studies. The model is particularly useful for more complicated plasma scenarios that involve multiple fast ion species such as JET’s 2021 DT-campaign.
Low-frequency zonal flow eigen-structures in tokamak plasmas
Authors: Ilgisonis V.I. , Lakhin V.P. , Marusov N.A. , Smolyakov A.I. , Sorokina E.A.
Published: December 2021

The nonlocal eigenmode analysis of low-frequency zonal flows (ZFs) in toroidally rotating tokamak plasmas is performed in the framework of the reduced one-fluid ideal magnetohydrodynamic model. It is shown that for typical profiles of plasma parameters toroidal plasma rotation results in the global ZF formation on the periphery of plasma column. For some types of equilibria these ZFs are aperiodically unstable that leads to the excitation of the differential plasma rotation at the tokamak plasma edge.
Zonal flow generation and toroidal Alfvén eigenmode excitation due to tearing mode induced energetic particle redistribution
Authors: Zhang H.W. , Ma Z.W. , Zhu J. , Zhang W. , Qiu Z.Y.
Published: December 2021

Generation of the n = 0 zonal flow and excitation of the n = 1 toroidal Alfvén eigenmode (TAE) due to the redistribution of energetic particles (EPs) by the m/n = 2/1 tearing mode (TM) are systematically studied with the hybrid drift-kinetic magnetohydrodynamic (MHD) simulations (m and n represent the poloidal and toroidal mode number, respectively). In the presence of the m/n = 2/1 TM, the amplitude of the n = 1 TAE shows a slower decay after its first saturation due to the wave–particle nonlinearity and the nonlinear generation of the n = 0 & higher-n (n ⩾ 2) sidebands. Meanwhile, a strong n = 0 zonal flow component is nonlinearly generated when both TAE and TM grow to large amplitudes. The redistribution of EPs by the m/n = 2/1 magnetic island results in a continuous drive on the background plasma, and finally produces the zonal flow through the MHD nonlinearity. In addition, the large m/n = 2/1 magnetic island is found to be responsible for the formation of the strong spatial gradient of the EP distribution through the resonance between EPs and TM, which can lead to burst of unstable TAE and destabilization of originally stable TAE.
Monitoring the brightness temperature of the Moon throughout the lunar cycle from radio observations in the Ku band
Authors: Galeano David , Edwin A. Quintero
Published: December 2021

Within the spectrum of radio waves, the Ku band (12 - 18 GHz
) stands out for the wide range of instruments available and for its relative ease of acquisition, given that satellite television operates in this band. This situation offers a great opportunity for the development of radio astronomy in countries with unfavorable climatic conditions for optical astronomy, since this band is only affected by dense masses of water vapor. In this article we present a methodology for the calibration of the receiver system of compact Ku-band radio telescopes, and its application in the determination of the brightness temperature of the Moon. Our methodology involves modeling the influence of the atmosphere of the Earth on the response of the radioreceptor, which minimizes the error in the calculation of the brightness temperature of the observed object. We applied the proposed methodology in the monitoring of the Lunar cycle using the Ku-band radio telescope of the Observatorio Astronomico of Universidad Tecnológica de Pereira, Colombia (OAUTP). After observing during May, June, and July of 2021, we obtained an average temperature of 213.15 K, with maximum and minimum values of 275.55 K and 150.75 K, respectively. In addition, we evidenced a delay of 5.75 days between the phase in which the maximum temperature is presented and the phase of the full Moon, which is consistent with the frequency of observation. The results show that our methodology is useful to optimize the calibration of compact Ku-band radio telescopes, and expand the potential of this type of instrument for the scientific study of radio sources other than the Sun, in this case the Moon.
Dipole Polarizability of C28and its Counterparts Nb4B18and Ta4B18. Insights from a Density Functional Theory (DFT) Endeavour
Authors: Xenides Demetrios , Karamanis Panaghiotis
Published: December 2021

We report on a preliminary investigation of the non linear optical (NLO) properties and in particular dipole polarizability. The target species are two perfect tetrahedral nanoclusters Nb4B18and Ta4B18, along with their nanofullerene counterpart that is C28. Our study based on density functionals (DFs) that have gained popularity among the scientific community. In addition we performed Hartree-Fock calculations known for not including dynamic electron correlation. The DF obtained values are characterized by some dispersion, with maximal differences to be around 5 %, in all three cases. Given that the DFT introduces a fuzzy percentage of electron correlation sets the observed convergence of HF values to DFT ones is at least surprising. Furthermore, it should be said that though the values can be characterized as accurate their reliability should not be taken for granted. Last, we note the smooth convergence of LC-BLYP, LC-BP86, LC-BPW91 to LC-whPBE.
Effectiveness of using The GeoEnzo Application on Metacognitive Abilities in Mathematics Learning
Authors: Syamsuddin  , Latif Abdul , Ahmad Herlina , Febryanti
Published: December 2021

This research is an experimental study that aims to determine the effectiveness of using the GeoEnzo application. The subjects in this study were students of class XII SMK Mega Link Majene. The research instrument was used to reveal students’ metacognitive abilities in understanding and solving problems on three-dimensional material. The instruments used were tests, observation sheets, and student response questionnaires. The data analysis used was descriptive and inferential statistical analysis. The results of the analysis showed that the average value of students’ metacognitive abilities in understanding the material was 82.75 in the high category, while the metacognitive ability in solving questions was 85.25 in the high category. Student activities are in the very active category and student responses to learning give a very positive response. The t-test shows the sig value. (2-tailed) = 0.000 < α = 0.05, thus the application of GeoEnzo application media is effective for students’ metacognitive abilities in mathematics learning.
Efficiency of Ni Content in Laterite Nickel Deposits through The Least Square Method Approach on Semivariogram
Authors: Usman F , Tinungki G M , Herdiani E T
Published: December 2021

Ordinary kriging is one of the geostatistical techniques used for spatial prediction on a spatially distributed random plane. Ordinary kriging is a linear unbiased estimator which is part of a semivariogram system of equations that minimizes errors of variance in estimating mineral resources. The semivariogram model shows optimal results in the estimation using the least square method, the effective minimization method smoothes the data points against the curve on a semivariogram graph, the least square makes the size error efficient in the semivariogram model and has been proven to be effective in reducing errors in the semivariogram model in the case of laterite nickel deposits. at PT. Vale Indonesia Tbk. Thus, conclusively the prediction of unsampled Ni content results is very accurate. This is indicated by the lowest root mean square error (RMSE) in limonite in the exponential model, saprolite in the spherical model, and bedrock in the gaussian model. The greatest value of Ni content in this study was in the saprolite layer.
Time Series Clustering for Robust Mean-Variance Portfolio Selection: Comparison of Several Dissimilarity Measures
Authors: Gubu La , Rosadi Dedi , Abdurakhman
Published: December 2021

This paper shows how to create a robust portfolio selection with time series clustering by using some dissimilarity measure. Based on such dissimilarity measures, stocks are initially sorted into multiple clusters using the Partitioning Around Medoids (PAM) time series clustering approach. Following clustering, a portfolio is constructed by selecting one stock from each cluster. Stocks having the greatest Sharpe ratio are selected from each cluster. The optimum portfolio is then constructed using the robust Fast Minimum Covariance Determinant (FMCD) and robust S MV portfolio model. When there are a big number of stocks accessible for the portfolio formation process, we can use this approach to quickly generate the optimum portfolio. This approach is also resistant to the presence of any outliers in the data. The Sharpe ratio was used to evaluate the performance of the portfolios that were created. The daily closing price of stocks listed on the Indonesia Stock Exchange, which are included in the LQ-45 indexed from August 2017 to July 2018, was utilized as a case study. Empirical study revealed that portfolios constructed using PAM time series clustering with autocorrelation dissimilarity and a robust FMCD MV portfolio model outperformed portfolios created using other approaches.
Rainfall Data Modeling with Artificial Neural Networks Approach
Authors: Astutik S , Pramoedyo H , Rahmi N S , Irsandy D , Damayanti R H P Y
Published: December 2021

Rainfall is one of the important information that widely used in various fields. Rainfall data involving location information is referred to as spatial rainfall data. Some of the model approaches to spatial rainfall data are the Vector Autoregressive (VAR) model, state-space, Markov chain stochastic model, and Geographically Weighted Regression (GWR). However, these models have not been able to produce predictions of the occurrence of no rain (zero value) or extreme values. Currently, theoretical modelling is mostly approached by artificial neural network (ANN) techniques. The purpose of this study is to model spatial rainfall data in East Java, Indonesia in 2020 with the ANN approach which is supported by several variables such as location and elevation information. The ANN used backpropagation and Rporp by combining the learning rate and layer which is then obtained the RMSE value. The results show that the best model has the smallest RMSE of 1.22 when the learning rate is 0.15 on 11 layers using Rprop algorithm.
Vector Autoregressive-Based Maximum MCUSUM Control Chart for Monitoring the Quality of White Crystal Sugar
Authors: Khusna H , Mashuri M , Wibawati
Published: December 2021

The white crystal sugar which is widely consumed sugar has two critical to qualities, namely the index of solution colour and the level of sulphur dioxide. These quality characteristics have small mean and variability shifts, as well as autocorrelation pattern. This research aims to propose residual-based Maximum Multivariate Cumulative Sum (Max-MCUSUM) control chart, one of the single control charts to monitor small shifts of mean and variability simultaneously, for monitoring the quality of white crystal sugar. The vector autoregressive (VAR) model is utilized to model the daily solution colour index and the daily sulphur dioxide level, then the residuals are monitored using Max-MCUSUM chart. The VAR-based Max-MCUSUM chart employs bootstrap, one of the nonparametric resampling methods, to estimate the control limit. The results of white crystal sugar quality control show that the processes in the last week of August 2020 need to be improved. Monitoring the white crystal sugar data using conventional control chart leads to many false alarm signals. Furthermore, the proposed control chart is more sensitive than the residual-based MEWMA and residual-based Hotelling’s T
2 charts in case of monitoring the quality of white crystal sugar.
Technology Integration to teaching mathematics in Higher Education during Coronavirus Pandemic using SAMR Model
Authors: Wijaya Tommy Tanu , Rizki L M , Yunita W , Salamah Umi , Pereira J , Zhang Cheng , Li Xinxin , Purnama A
Published: December 2021

Technology integration is one of the abilities teachers need to support teaching and learning activities and direct students to deep learning. Choosing a learning media based on technology is more difficult in statistics lesson. This study aimed to analysis the ability of teachers in integrating technology during the coronavirus pandemic using the SAMR model. This research used a qualitative method, this research data was in the form of information on what technology was used and how the teacher integrated technology during the coronavirus pandemic. Data was collected by means of observation and interviewing 2 Guangxi Normal University students who took this course. The results showed that the ability of teachers to integrate technology in statistics lesson during coronavirus pandemic was at every SAMR level. This study proves that the coronavirus pandemic has a positive impact on teachers’ ability to integrate technology.
The Impact of Creative Problem-Solving Learning Model Based Android Towards Learning Outcomes of Elementary School Students
Authors: Jusmawati  , Satriawati  , Irman R , Rahman Abdul , Arsyad Nurdin
Published: December 2021

This study aims to know the impact of the Creative Problem Solving learning model based on android on the learning outcomes of elementary school students. The numbers population was all students of SD Tunas Bangsa. The technique of determining the sample used simple random sampling. This research used pre-experimental with One Group Pretest-Posttest Design. Data collection techniques used learning outcomes tests to measure the student’s learning outcomes both before and after being given treatment, documentation, and observations about student learning activities and teacher observations regarding the implementation of the model during the learning process. Descriptive statistical analysis data described the students’ mathematics learning outcomes. Inferential statistical analysis to test the hypothesis using the dependent t-test or Paired-Sample T-Test with SPSS 21.0 version. The results of the research showed that there was an impact of the Creative Problem Solving learning model based on android towards learning outcomes. This is evidenced by the results of the pretest in the less category experienced an increase in posttest learning outcomes in the good category. It can be concluded that there is an the impact of Creative Problem Solving learning model based on android towards learning outcomes of elementary school students.
Studying the surfactant dynamics at non-isothermal liquid surface with thermography
Authors: Mizev A I , Shmyrov A V
Published: December 2021

The dynamics of liquid multiphase systems largely depends on the conditions on the interface. The behavior of a system with adsorbed surfactant layers at the interface boundaries may differ qualitatively from the behavior of a system with pure surface. The experimental study of such systems is difficult, since the presence of adsorbed layer can most often be judged only by indirect signs. Therefore, most of the research is carried out by numerical modeling. Unfortunately, the currently existing numerical studies of liquid multiphase systems with adsorbed surfactant layer are far from perfect due to numerous simplifications and approximations assumed in theoretical models. In this paper, we propose a new approach for visualization and studying the boundary between a clean surface and an adsorbed surfactant layer. It is based on the comparison of track images of the fluid motion in the volume and the registration of the temperature distribution at the interface boundary. This approach made it possible to unambiguously associate the characteristic regions on the temperature profile with the position of the so-called stagnation point. The proposed method for visualizing the stagnation point can be useful in a number of problems of interface hydrodynamics based on the thermocapillary effect.
Image-based processing simulation of shock wave propagation through the area of ionization instability
Authors: Kravchenko O V , Azarova O A , Lapushkina T A
Published: December 2021

A partially automatic method of digital processing images (photographs, shadow and Schlieren pictures) for the analysis of experimental data is proposed. The method is utilized to investigate the effect of the region of ionization instability created by a glow gas discharge on the front of an initially flat shock wave. The proposed method is based on a composition of simple image processing operations and makes it possible to perform simulations taking into account the real geometry of the ionization strata and the shape of the front of a shock wave based on the obtained experimental images. First, as a result of digital processing the geometry of experimental objects is extracted from the images. This information is then embedded in the Navier-Stokes code for conducting simulations. New results for the real geometry of ionization strata of different scales are presented which confirmed the previous ones obtained for the density homogeneously stratified source model.
Polychromatic Hilbert diagnostics of phase and temperature disturbances, induced by candle flame in air
Authors: Arbuzov V A , Arbuzov E V , Dubnishchev Yu N , Zolotukhina O S , Lukashov V V
Published: December 2021

The work is motivated by the scientific and practical significance of the problem of non-disturbing diagnostics of phase and temperature fields induced in a gas medium by a flame of a torch (candle). The spatial conditions in which the fields are studied satisfy the model of axial symmetry of the torch associated with the vertical orientation of the candle. A method adequate to the problem to be solved has been developed, based on polychromatic Hilbert visualization of phase optical density fields, measurement of the temperature profile in selected sections of the medium under study, registration and selection of RAW images recorded by the photomatrix in RGB channels. The visualized Hilbert structures contain information on the phase optical density perturbations induced by the temperature field. The reliability of the results is confirmed by comparing the experimentally obtained hilbertograms and those reconstructed from phase structures using the Abel transform.
Investigation of partially transparent and high-density two-phase liquids using laser interference method
Authors: Kuchmenko A V , Lapitsky K M , Lapitskaya I A , Badamshina E B
Published: December 2021

The purpose of the present work was to investigate partially transparent and high-density two-phase liquids using the laser interference method to establish the limits of applicability of this method. The results of the work include the interference fringe patterns of drops when using various kinds of liquids, the calculated drop sizes. The calculation of inaccuracies was also carried out to further establishing the limits of applicability of this method.
Processing and visualization of the results of parametric numerical calculations
Authors: Bondarev A E , Kuvshinnikov A E
Published: December 2021

In modern problems of mathematical modeling in computational gas dynamics, it is increasingly necessary to implement parametric studies. In these cases, the key factors of the problem under consideration vary with the chosen step within the given ranges. Calculations of this kind can be effectively carried out by constructing a generalized computational experiment. A generalized computational experiment is a computational technology that combines the solution of mathematical modeling problems, parallel technologies, and visual analytics technologies. The results of a generalized computational experiment are multidimensional arrays, where the dimension of the arrays corresponds to the number of key factors. Processing and visual presentation of such arrays requires solving a number of separate tasks. The processing and visual presentation of the results are carried out for target functionals represented as a function of many variables. The report presents an examples of solving specific processing and visualization problems based on the implemented generalized computational experiment for 3D cone in supersonic flow.