bluuebunny/crossref_metadata_2025 huggingface dataset:
Using data assimilation to train a hybrid forecast system that combines machine-learning and knowledge-based components
Authors: Wikner Alexander , Pathak Jaideep , Hunt Brian R. , Szunyogh Istvan , Girvan Michelle , Ott Edward
Published: May 2021

We consider the problem of data-assisted forecasting of chaotic dynamical systems when the available data are in the form of noisy partial measurements of the past and present state of the dynamical system. Recently, there have been several promising data-driven approaches to forecasting of chaotic dynamical systems using machine learning. Particularly promising among these are hybrid approaches that combine machine learning with a knowledge-based model, where a machine-learning technique is used to correct the imperfections in the knowledge-based model. Such imperfections may be due to incomplete understanding and/or limited resolution of the physical processes in the underlying dynamical system, e.g., the atmosphere or the ocean. Previously proposed data-driven forecasting approaches tend to require, for training, measurements of all the variables that are intended to be forecast. We describe a way to relax this assumption by combining data assimilation with machine learning. We demonstrate this technique using the Ensemble Transform Kalman Filter to assimilate synthetic data for the three-variable Lorenz 1963 system and for the Kuramoto–Sivashinsky system, simulating a model error in each case by a misspecified parameter value. We show that by using partial measurements of the state of the dynamical system, we can train a machine-learning model to improve predictions made by an imperfect knowledge-based model.
Mechanism of stabilization of porous coatings on unstable supersonic mode in hypersonic boundary layers
Authors: Long Tiehan , Dong Ying , Zhao Rui , Wen Chihyung
Published: May 2021

This study clarifies the fundamental mechanism by which porous coatings suppress the supersonic mode instability in the hypersonic boundary layer (BL) by using Doak's momentum potential theory. The independent energy budget equations for vortical, acoustic, and thermal components of instabilities are derived. Data from direct numerical simulations of Mach 6.0 flat plate flows on a solid wall and porous coatings are then analyzed. By decomposing the momentum density into vortical, acoustic, and thermal components, the source terms and fluxes are studied based on their corresponding energy corollaries. The results demonstrate the role of different components in the generation and transport of the total fluctuation enthalpy (TFE) and the way in which the fluctuation energy is transferred between components. In the case of the solid wall, the oscillating disturbance on the BL consists of acoustic and vortical components. Near the critical layer, the positive acoustic source and energy transferred from the vortical component are primary energy producers for acoustic fluxes. Then, the TFE is transported outward by the acoustic component, which leads to “sound radiation” in the supersonic mode. In the case of the porous coating, the positive vortical source near the surface of the plate is suppressed significantly. Less vortical energy is transported to the critical layer, and thus less vortical energy is transformed into acoustic energy. Acoustic energy is eventually exhausted due to energy loss in the outward transport of the TFE, and “sound radiation” disappears from the porous coating.
Infrared single-photon sensitivity in atomic layer deposited superconducting nanowires
Authors: Taylor Gregor G. , Morozov Dmitry V. , Lennon Ciaran T. , Barry Peter S. , Sheagren Calder , Hadfield Robert H.
Published: May 2021

We report on the extended infrared single-photon response of niobium nitride superconducting nanowires deposited by atomic layer deposition. The superconducting nanowire single-photon detectors are based on 4.65 nm thick NbN, patterned into 100 nm meanders, and characterized at 2.5 K. We verify single-photon sensitivity from 1310 to 2006 nm with saturated response at shorter wavelengths.
Giant enhancement of second harmonic light intensity in waveguiding core/shell ZnTe/ZnMgTe nanowires
Authors: Szymura M. , Mitioglu A. A. , Wojnar P. , Maude D. K. , Płochocka P. , Kłopotowski Ł.
Published: May 2021

We present studies of second harmonic generation in core/shell ZnTe/Zn1−xMgxTe nanowires (NWs) with a waveguiding geometry. The NWs are excited by a pulsed femtosecond laser over a broad range of excitation wavelengths from 800 to 1140 nm. This allows us to demonstrate a giant increase in the second harmonic light intensity. We attribute the observed effect to the combined action of absorption by the NW, the confinement of light due to the waveguiding geometry, and the bending of the NWs. We show that a multi-photon luminescence (MPL) is generated alongside the second harmonic light. Furthermore, we demonstrate a strong polarization anisotropy of the second harmonic and MPL signals. Unlike in bulk semiconductors and quantum wells, this anisotropy is not due to the underlying symmetries of the crystal structure, but can be attributed solely to the shape anisotropy of the NW.
Teleparallel geometries not characterized by their scalar polynomial torsion invariants
Authors: McNutt D. D. , Coley A. A. , van den Hoogen R. J.
Published: May 2021

A teleparallel geometry is an n-dimensional manifold equipped with a frame basis and an independent spin connection. For such a geometry, the curvature tensor vanishes and the torsion tensor is non-zero. A straightforward approach to characterizing teleparallel geometries is to compute scalar polynomial invariants constructed from the torsion tensor and its covariant derivatives. An open question has been whether the set of all scalar polynomial torsion invariants, IT, uniquely characterize a given teleparallel geometry. In this paper, we show that the answer is no and construct the most general class of teleparallel geometries in four dimensions, which cannot be characterized by IT. As a corollary, we determine all teleparallel geometries, have vanishing scalar polynomial torsion invariants.
Numerical investigation on the effect of diamond-shaped turbulator on thermo-hydraulic performance of tube
Authors: Hajabdollahi Hassan , Shamsi Sajjad , Dehaj MohammadShafiey , Salarmofrad Masoud , Rezaeian Mohsen
Published: May 2021

In this paper, thermo-hydraulic analysis of a diamond-shaped turbulator in a tube was investigated using the numerical simulation. Nusselt number and friction factor were evaluated by variation of Reynolds number in the range of 3500–16 500 and turbulator parameters including step ratio and rode diameter. Numerical validation was performed with experimental model and a good matching was observed. Then, closed form correlations for the Nusselt number and friction factor were presented with respect to Reynolds number. Numerical results revealed that a turbulator with a step ratio =1 and rod diameter = 3 mm provide the best Nusselt number. In addition, the results showed that the friction factor reduces by increment of both step ratio and rode diameter. Furthermore, by adjusting a turbulator with the new parameters, 40–56% improvement in the friction factor was noticed compared with the literature results. Then, by using definition of efficiency, the effect of both step ratio and rod diameter was investigated. The results revealed 4.60%–18.20% improvement in the efficiency for step ratio = 3 and rod diameter = 3 mm in comparison with the reported results in the literature. Finally, some correlations for Nusselt number and friction factor using the numerical results were presented with acceptable agreement.
Intolerance of uncertainty modulates brain-to-brain synchrony during politically polarized perception
Authors: van Baar Jeroen M. , Halpern David J. , FeldmanHall Oriel
Published: May 2021

Significance

Political partisans view the world through a biased lens, but little is known about how these biased perceptions of reality arise. We measured the brain activity of committed partisans watching real political video footage. Although all participants viewed the same videos, brain responses diverged between liberals and conservatives, reflecting differences in the subjective interpretation of the footage. This polarized perception was exacerbated by a personality trait: intolerance of uncertainty. Participants less tolerant to uncertainty in daily life had more ideologically polarized brain responses than those who tolerate uncertainty. This was observed on both sides of the ideological aisle. This suggests that aversion to uncertainty governs how the brain processes political information to form black-and-white interpretations of inflammatory political content.
Military nutrition research: Contemporary issues, state of the science and future directions
Authors: Karl J. Philip , Margolis Lee M. , Fallowfield Joanne L. , Child Robert B. , Martin Nicola M. , McClung James P.
Published: May 2021

The importance of diet and nutrition to military readiness and performance has been recognized for centuries as dietary nutrients sustain health, protect against illness, and promote resilience, performance and recovery. Contemporary military nutrition research is increasingly inter‐disciplinary with emphasis often placed on the broad topics of (1) determining operational nutrition requirements in all environments, (2) characterizing nutritional practices of military personnel relative to the required (role/environment) standards, and (3) developing strategies for improving nutrient delivery and individual choices. This review discusses contemporary issues shared internationally by military nutrition research programmes, and highlights emerging topics likely to influence future military nutrition research and policy. Contemporary issues include improving the diet quality of military personnel, optimizing operational rations, and increasing understanding of biological factors influencing nutrient requirements. Emerging areas include the burgeoning field of precision nutrition and its technological enablers.
Impact of a 246 Km ultra‐marathon running race on heart: Insights from advanced deformation analysis
Authors: Pagourelias Efstathios D. , Christou Georgios A. , Sotiriou Panagiota G. , Anifanti Maria A. , Koutlianos Nikolaos A. , Tsironi Maria P. , Christou Konstantinos A. , Vassilikos Vasileios P. , Deligiannis Asterios P. , Kouidi Evangelia J.
Published: May 2021

Although previous studies suggest that prolonged intense exercise such as marathon running transitorily alters cardiac function, there is little information regarding ultramarathon races. Aim of this study was to investigate the acute impact of ultra‐endurance exercise (UEE) on heart, applying advanced strain imaging. Echocardiographic assessment was performed the day before and at the finish line of “Spartathlon”: A 246 Km ultra‐marathon running race. 2D speckle‐tracking echocardiography was performed in all four chambers, evaluating longitudinal strain (LS) for both ventricles and atria. Peak strain values and temporal parameters adjusted for heart rate were extracted from the derived curves. Out of 60 participants initially screened, 27 athletes (19 male, age 45 ± 7 years) finished the race in 33:34:27(28:50:38‐35:07:07) hours. Absolute values of right (RV) and left ventricular (LV) LS (RVLS −22.9 ± 3.6 pre‐ to −21.2 ± 3.0% post‐, p=0.04 and LVLS −20.9 ± 2.3 pre‐ to −18.8 ± 2.0 post‐, p=0.009) slightly decreased post‐race, whereas atrial strain did not change. RV and LV LS decrease was caused mainly by strain impairment of basal regions with apical preservation. Inter‐chamber relationships assessed through RV/LV, LV/LA, RV/RA and RA/LA peak values' ratios remained unchanged from pre to post‐race. Finally, UEE caused an extension of the systolic phase of cardiac cycle with concomitant diastole reduction (p<0.001 for all strain curves). Conclusively, ventricular LS strain as well as effective diastolic period slightly decreased, whereas atrial strain and inter‐chamber relationships remained unchanged after running a 246‐km‐ultra‐marathon race. These changes may be attributed to concomitant pre‐ and afterload alterations following UEE.
Fabrication of high-aspect-ratio polydimethylsiloxane microstructures by reducing the interfacial adhesion in soft lithography
Authors: Zhou Bo , Su Bo , Ta Wurui , Yang Zenghui , Meng Junhu
Published: May 2021

The soft lithographic fabrication of high-aspect-ratio polydimethylsiloxane (PDMS) microstructures is quite challenging because of the strong interfacial adhesion between them and masters during demolding. This paper presents a simple method for fabricating high-aspect-ratio PDMS microstructures by reducing the interfacial adhesion through the cooling process. The effect of cooling process on the topography, elastic property, and adhesion property of Sylgard 184 PDMS is studied. It is found that wrinkles are formed on the surface of PDMS and that the Young’s modulus of PDMS is increased by the air cooling process. Consequently, the air-cooled PDMS has lower adhesion than the traditional oven-cooled PDMS. This result could be explained by the adhesion parameter theory: both the high amplitude of the wrinkles formed on the surface of PDMS and the high Young’s modulus of PDMS increase separation forces and reduce adhesive forces in the interface. Application of this method is demonstrated by fabricating PDMS microchannels from a silicon master which has microstructures with different aspect ratios. Compared with PDMS microchannels obtained by the oven cooling process, PDMS microchannels with a depth of 200 μm and an aspect ratio of 10 are successfully fabricated by the air cooling process.
Drying path dependence in microrheological characteristics of cellulose nanofiber dispersion revealed by single particle tracking
Authors: Koitabashi Takuma , Hanasaki Itsuo
Published: May 2021

Rheological characterization of cellulose nanofiber (CNF) dispersion is important for the process design of nanopaper fabrication. However, the existing macroscopic approach is difficult to reveal microscopic signal, or nonequilibrium nature of drying, distinct from the concentration dependence in equilibrium. We report the microscopic characterization in the drying process of CNF dispersion by the microscopy movie analysis, based on the single particle tracking (SPT) of probe particles. Since SPT does not require invasive shear flow to the system of interest, the rheological characterization in the drying process can be realised. We focused on the role of initial CNF concentration to examine the nonequilibrium effect of drying. The path of drying for a higher initial CNF concentration is not simply a time compression of the path of the lower initial concentration. It is revealed by the time-evolution curves of the generalised diffusion coefficient and the scaling exponent for probe particles. One of the origins of this path-wise dependence on the initial CNF concentration is the macroscopic spatial nonuniformity of the drying process. Thus, the effect of macroscopic condition is microscopically determined.
Flexible Ta/TiO
x
/TaO
x
/Ru memristive synaptic devices on polyimide substrates
Authors: Li Jiacheng , Hao Chenyang , Guo Shuqin , Li Yingchen , Ren Jiuzhou , Zhou Liwei , Zhao Jinshi
Published: May 2021

It is very urgent to build memristive synapses and even wearable devices to simulate the basic functions of biological synapses. The linear conductance modulation is the basis of analog memristor for neuromorphic computing. By optimizing the interface engineering wherein Ta/TiO
x
/TaO
x
/Ru was fabricated, all the memristor devices with different TiO
x
thickness showed electroforming-free property. The short-term and long-term plasticity in both potentiation and depression behaviors can be mimicked when TiO
x
was fixed at 25 nm. The presented memristive synapses simulated the stable paired-pulse facilitation and spike-timing dependent plasticity performance. The potentiation and depression in linearity and symmetry improved with the TiO
x
thickness increasing, which provides the feasibility for the application of artificial neural network. In addition, the device deposited on polyimide (PI) still exhibits the synaptic performance until the bending radii reaches 6 mm. By carefully tuning the interface engineering, this study can provide general revelation for continuous improvement of the memristive performance in neuromorphic applications.
Compactification for asymptotically autonomous dynamical systems: theory, applications and invariant manifolds
Authors: Wieczorek Sebastian , Xie Chun , Jones Chris K R T
Published: May 2021

We develop a general compactification framework to facilitate analysis of nonautonomous ODEs where nonautonomous terms decay asymptotically. The strategy is to compactify the problem: the phase space is augmented with a bounded but open dimension and then extended at one or both ends by gluing in flow-invariant subspaces that carry autonomous dynamics of the limit systems from infinity. We derive the weakest decay conditions possible for the compactified system to be continuously differentiable on the extended phase space. This enables us to use equilibria and other compact invariant sets of the limit systems from infinity to analyze the original nonautonomous problem in the spirit of dynamical systems theory. Specifically, we prove that solutions of interest are contained in unique invariant manifolds of saddles for the limit systems when embedded in the extended phase space. The uniqueness holds in the general case, that is even if the compactification gives rise to a centre direction and the manifolds become centre or centre-stable manifolds. A wide range of problems including pullback attractors, rate-induced critical transitions (R-tipping) and nonlinear wave solutions fit naturally into our framework, and their analysis can be greatly simplified by the compactification.
Possibilities of a laboratory experiment on investigation of auroral kilometric radiation in the near-Earth plasma
Authors: Viktorov Mikhail , Chernyshov Alexander , Chugunin Dmitry , Mogilevsky Mikhail
Published: May 2021

Observations are reported of electromagnetic emissions at frequencies above the electron gyrofrequency in a mirror-confined electron cyclotron resonance plasma. These emissions are interpreted as the excitation of the fast extraordinary wave at the fundamental harmonic of the electron gyrofrequency, similar to the excitation of the auroral kilometric radiation (AKR) of the Earth. The paper proposes a method for studying the temporal characteristics of physical processes occurring in the auroral electron acceleration region, which is applied to the AKR measurements onboard INTERBALL-2 spacecraft and adopted to the measurements of laboratory plasma emissions. The joint data analysis of satellite measurements and the results of laboratory experiments showed similarities in the cyclotron instability development.
Z-scheme g-C3N4/Fe2O3 for efficient photo-oxidation of benzylamine under mild conditions
Authors: Chen Yefeng , Tang Dan , Wang Zhuhan , Li Wen , Yin Mengyun , Yang Qin , Zhou Yafen , Zhang Kaiming , Kan Taotao , Zhou Limei
Published: May 2021

As an important intermediate, imine is widely used in industrial chemistry. The photocatalytic oxidation of amines to form imines is a green and economical method. But it remains a challenge for the efficient transformation under mild conditions. Herein, a Z-scheme carbon nitride (CM)-Fe2O3 heterojunction photocatalyst was synthesized by in-situ preparation of Fe2O3 nanoparticles on two-dimensional CM nanosheets. The as-prepared catalyst exhibited efficient photocatalysis activity in selective oxidation of benzylamine to N-benzylidene benzylamine. Under ambient air and room temperature, the selectivity and conversion rate both can reach 99.9%, and the corresponding turnover frequency value reaches up to 9.99 mmol g−1 h−1, superior to the most of heterogeneous photocatalysts reported in previous literatures. The excellent catalytic activity of the modified CM material may be due to the enhanced absorption of visible light and the improved photogenerated carrier separation and migration rate, and the Z-scheme mechanism also retains the strong oxidation and reduction ability of the composite material. This work will provide a promising and practical method to promote the photocatalytic conversion of solar-driven organics.
Ridge-channel AlGaN/GaN normally-off high-electron mobility transistor based on epitaxial lateral overgrowth
Authors: Ji Xiaoli , Fariza Aqdas , Zhao Jie , Wang Maojun , Wang Junxi , Yang Fuhua , Li Jinmin , Wei Tongbo
Published: May 2021

A ridge-channel AlGaN/GaN high-electron mobility transistor (HEMT) utilizing selective-area growth and epitaxial lateral overgrowth (ELO) technique is proposed in this work to achieve high-performance normally-off devices. It has a c-plane platform for the source and the drain contacts, and sidewalls of

10

1
ˉ

1

lattice plane for the gate contact. The sidewalls have characteristics of weak polarization and thin barrier, which are advantageous for realizing normally-off operation. Two ridge HEMTs with triangular and trapezoid channel are designed. Theoretical simulation demonstrates a threshold voltage of 0.03 V for the sidewall channel with reduced polarization and barrier thickness, and a threshold voltage of 1.1–1.3 V for the ridge HEMTs assuming no polarization charge in sidewall channel. The ridge-channel device also exhibits high saturation drain current. The ELO-based ridge-channel opens a new way to achieve normally-off AlGaN/GaN HEMT.
An analytical solution for McIntyre’s model of avalanche triggering probability for SPAD compact modeling and performance exploration
Authors: Chaves De Albuquerque Tulio , Issartel Dylan , Gao Shaochen , Benhammou Younes , Golanski Dominique , Clerc Raphaël , Calmon Francis
Published: May 2021

Single photon avalanche diodes (SPADs) are widely used to monitor fast and weak optical signals. The modeling of two main figures of merit of SPAD, namely the dark count rate (DCR) and the photon detection probability, requires one to calculate the avalanche triggering probability (ATP), usually obtained by numerically solving two transcendental equations (the McIntyre model) as post processing of technology computer-aided design simulations. This paper proposes an analytical alternative to this approach, exploiting an approximation of the impact ionization rates, in principle valid only under high field conditions, but extended to all fields by a simple fitting procedure. The proposed approximated/analytical ATP calculation can be efficient and relevant for SPAD compact modeling that is compatible with a spice-like simulator. As an illustration, a full analytical calculation for DCR based on both ATP and generation terms for a P+N abrupt diode junction is presented.
Shape memory polymer composite unit with embedded heater
Authors: Quadrini Fabrizio , Iorio Leandro , Bellisario Denise , Santo Loredana
Published: May 2021

A shape memory polymer composite (SMPC) unit has been manufactured with embedded heater. The structure of the SMPC unit has been designed to allow reaching high recovery loads with a reduced size of the functional device. The unit is a composite sandwich with four carbon fibre reinforced (CFR) plies, two SMP foam cores, and one SMP interlayer. In the mid-plane of the sandwich the heater is integrated, being immersed in the SMP interlayer. The adopted manufacturing procedure was able to provide the necessary consolidation in one step moulding thanks to the use, during lamination, of pre-formed SMP cores, and uncured SMP powder for the interlayer. The SMP cores were manufactured by solid state foaming of the same SM epoxy powder. SMPC laminates, without the embedded heater, were also manufactured for testing as well as traditional four-ply CFR laminates. Several tests were carried out for temperature calibration and for investigating SM properties of the SMPC laminates and unit. Dynamic mechanical analyses, hot bending tests, and microscopic observations were performed on CFR and SMPC laminates. It was found that the SMP layers reduce the glass transition temperature of the laminates as well as the transition onset temperature and, above all, the extension of the transition range thus providing the trigger effect to the SMPC transition. Double-cycle SM tests were carried on the SMPC unit at different temperatures from 160 °C to 190 °C. The unit (20 × 45 mm2) was able to exert recovery loads over 7.4 N almost independently from the temperature and without any evidence of failure after several repeated tests. High values were measured also for the shape fixity and shape recovery which were, on average, higher than 96% and 95%, respectively.
Photoionization of nS and nD Rydberg atoms of Rb and Cs from the near-infrared to the ultraviolet spectral region
Authors: Viray Michael A , Paradis Eric , Raithel Georg
Published: May 2021

We present calculations of the photoionization (PI) cross sections of rubidium and cesium Rydberg atoms for light with wavelengths ranging from the infrared to the ultraviolet, using model potentials from Marinescu et al (1994 Phys. Rev. A
49 982). The origins of pronounced PI minima are identified by investigating the free-electron wavefunctions. These include broad PI minima in the nS to ϵP PI channels of both Rb and Cs, with free-electron energy ϵ, which are identified as Cooper minima. Much narrower PI minima in the nD to ϵF channels are due to shape resonances of the free-electron states. We describe possible experimental procedures for measuring the PI minima, and we discuss their implications in fundamental atomic physics as well as in practical applications. Measurements of PI cross sections of Rydberg atoms may serve as a sensitive probe for many-electron interactions of the Rydberg electron in the atomic core region.
Generalization of the Tavis–Cummings model for multi-level anharmonic systems
Authors: Campos-Gonzalez-Angulo J A , Ribeiro R F , Yuen-Zhou J
Published: May 2021

The interaction between anharmonic quantum emitters (e.g. molecular vibrations) and confined electromagnetic fields gives rise to quantum states with optical and chemical properties that are different from those of their precursors. The exploration of these properties has been typically constrained to the first excitation manifold, the harmonic approximation, ensembles of two-level systems [Tavis–Cummings (TC) model], or the anharmonic single-molecule case. The present work studies, for the first time, a collective ensemble of identical multi-level anharmonic emitters and their dipolar interaction with a photonic cavity mode, which is an exactly solvable many-body problem. The permutational properties of the system allow identifying symmetry classified submanifolds in the energy spectrum. Notably, in this approach, the number of particles, typically in the order of several millions, becomes only a parameter from the operational standpoint, and the size of the dimension of the matrices to diagonalize is independent of it. The formalism capabilities are illustrated by showing the energy spectrum structure, up to the third excitation manifold, and the calculation of the photon contents as a permutationally invariant quantity. Emphasis is placed on (a) the collective (superradiant) scalings of light–matter couplings and the various submanifolds of dark (subradiant) states with no counterpart in the single-molecule case, as well as (b) the delocalized modes containing more than one excitation per molecule with no equivalent in the TC model. We expect these findings to be applicable in the study of non-linear spectroscopy and chemistry of polaritons.
Static bifurcation and vibrational resonance in an asymmetric fractional-order delay Duffing system
Authors: Li Ruihong , Li Jun , Huang Dongmei
Published: May 2021

Static bifurcation and vibrational resonance in a fractional-order delay Duffing system with asymmetric potential are studied. By utilizing the fast and slow variable separation approach, the static bifurcation is discussed based on the equivalent system. It is found when fractional order and time delay change, the static bifurcation of fractional-order system with asymmetric potential is different from that of system with symmetric potential. In addition, changes in asymmetric parameter can also induce saddle-node bifurcation. Furthermore, according to the approximate analytical expression of response amplitude, the effects of high frequency amplitude, fractional order and asymmetric parameter on vibrational resonance are investigated. The results show that the number of resonance peaks of asymmetric potential system is related to the selection of initial value and the change of asymmetric parameter can also induce vibrational resonance. In the meantime, the good agreement between theoretical prediction and numerical simulation confirms the validity of theoretical analysis.
Tunable bandgaps and flat bands in twisted bilayer biphenylene carbon*
Authors: Ma Ya-Bin , Ouyang Tao , Chen Yuan-Ping , Xie Yue-E
Published: May 2021

Owing to the interaction between the layers, the twisted bilayer two-dimensional (2D) materials exhibit numerous unique optical and electronic properties different from the monolayer counterpart, and have attracted tremendous interests in current physical research community. By means of first-principles and tight-binding model calculations, the electronic properties of twisted bilayer biphenylene carbon (BPC) are systematically investigated in this paper. The results indicate that the effect of twist will not only leads to a phase transition from semiconductor to metal, but also an adjustable band gap in BPC (0 meV to 120 meV depending on the twist angle). Moreover, unlike the twisted bilayer graphene (TBG), the flat bands in twisted BPC are no longer restricted by “magic angles”, i.e., abnormal flat bands could be appeared as well at several specific large angles in addition to the small angles. The charge density of these flat bands possesses different local modes, indicating that they might be derived from different stacked modes and host different properties. The exotic physical properties presented in this work foreshow twisted BPC a promising material for the application of terahertz and infrared photodetectors and the exploration of strong correlation.
Isospin effects of projectile fragmentation in a Boltzmann-Langevin approach *
Authors: Li Bing , Tang Na , Zhang Feng-Shou
Published: May 2021

The isospin effects of projectile fragmentation at intermediate energies are investigated using an isospin-dependent Boltzmann-Langevin model. The collisions of mass-symmetric reactions including 58Fe, 58Ni + 58Fe, and 58Ni at intermediate energies, in the 30 to 100 MeV/A range, are studied for different symmetry energies. Yield ratios of the isotopic, isobaric, and isotonic pairs of fragments from the intermediate-mass region using three symmetry energies are extracted as functions of the N/Z ratio of the composite systems in the entrance channel and the incident energies. It is found that the yield ratios are sensitive to symmetry energies, especially for neutron-rich systems, and the calculations using soft symmetry energy are closer to the experimental data. The isospin effect is stronger for the soft symmetry energy, owing to the competition of the repulsive Coulomb force and the symmetry energy attractive force on the proton. For the first time, the splits are presented, revealing a transition from the isospin equilibrium at lower energies to translucency at intermediate energies. The results show a degree of transparency in that intermediate mass fragments undergo a transition from dependence on the composite systems in the entrance channel to reliance on the projectile and target nuclei.
Simulations of ICRF heating of fusion oriented plasmas in plane-stratified and full toroidal geometry
Authors: Brambilla M. , Bilato R.
Published: May 2021

We compare results from the fully toroidal TORIC–SSFPQL package (Brambilla and Bilato 2006 Nucl. Fusion
46 s387) and from the plane-stratified geometry solver FELICE (Brambilla 1989 Plasma Phys. Control. Fusion
31 723) to illustrate the advantages and the limitations of the two approaches for the simulations of Ion Cyclotron Radio Frequency heating of tokamak plasmas. We point out that some of the predictions of the plane-stratified models do not straightforwardly apply to the true toroidal configuration. This is the case, in particular, for the excitation of guided modes between the plasma surface and the vessel.
Multi-task service composition model considering competitive resource constraint in cloud manufacturing
Authors: Zhongning Wang , Yankai Wang , Ronghua Chen , Hui Huang , Bin Luo
Published: May 2021

Service composition optimization is one of the core issues of cloud manufacturing research. At present, relevant researches mostly focus on single-task service composition, and there are few reports on the problem of multi-task service composition considering resource competition. However, in the real cloud manufacturing environment, multi-task service composition is common, so how to formulate a robust multi-task service composition model is a meaningful research direction. This paper first proposes a multi-task service composition optimization model considering resource competition constraints (MTSCOM-RCC) in the cloud manufacturing environment to fill the above-mentioned gap. The MTSCOM-RCC model considers the conflicts of interest and time between parallel subtasks and proposes an important service evaluation indicator. Secondly, a two-layer coding method, including task layer and subtask, is proposed based on studying the MTSCOM-RCC’s competition mechanism and characteristics. An improved hybrid genetic artificial bee colony algorithm model is proposed to solve the multi-task model. The model is combined with the global optimization method and task queue optimization method. Experimental results prove that the two-layer task optimization method model is more feasible and effective than the other two solution models.
Reservoir charaterization using J-atribute as a new attribute to reduce ambiguity in predicting reservoirs
Authors: Dwinanda I G , Haris A
Published: May 2021

The Amplitude Variation Offset (AVO) technique has often been used to predict the deposition of hydrocarbons. Knott and Zoeppritz developed the AVO method by using values of primary wave velocity (vp), secondary wave velocity (vs) and density. Then, Rutherford and William divide AVO into 4 classes based on intercept and gradient charts. This method is successfully used to predict hydrocarbons. However, in some cases there are still ambiguities and misinterpretations such as those occurring in oil and water which assess large porosity and similar characters, so that in this study required a new AVO attribute proposed by the name J-attribute to study hydrocarbons and use ambiguous in the results interpretation. The J-attribute method is a new method in Indonesia, which has not yet been tried in the Indonesian field so this research wants to prove the working principle of the J-attribute method required to provide maximum results in determining the fluid. This method is carried out in the Fauna Field, which is made in the North Sumatra Basin. The data used in this study 3 wells equipped with markers and log data such as Gamma Ray, SP, Caliper, Neutron Porosity, Density, Resistivity, DT, Photoelectric, and check shot.
Photocatalytic degradation of phenol using immobilized titania in activated carbon from Canarium ovatum Engl. nut shell
Authors: Gasga K , Rebuya N , Lasarte E
Published: May 2021

Presented study determined the photocatalytic treatment of phenol in aqueous medium using titania (TiO2) immobilized in activated carbon derived from charred Canarium ovatum Engl. nut shell through boil deposition method. Composite dosage, irradiation time, initial phenol concentration, and pH were varied to investigate how percent degradation of phenol would respond. The investigation showed that amongst all parameters, only pH has a significant effect to the photocatalytic degradation of phenol, wherein degradation increases as pH value decreases. Moreover, Design Expert® showed that 90.437% phenol degradation will be achieved using optimum values.
Analysis of suspended sediment distribution in Lamteng waters, Nasi Island, Aceh Besar District, Indonesia
Authors: Arsyami Y F , Purnawan S , Yuni S M , Setiawan I
Published: May 2021

The presence of sediment in the water column that moves without touching the bottom is known as suspended sediment. The distribution of suspended sediments in the coastal area is strongly influenced by river flows and ocean currents. Thus, this study aims to determine the distribution pattern and level of suspended sediment concentration in Lamteng waters, Nasi Island, Aceh Besar District. This research was conducted in October and December 2019. Samples were taken from 15 stations from the research location, each in October and December. Total suspended solids (TSS) samples were analysed using the Gravimetric method, in which the TSS value distribution was presented using the Natural Neighbour method. The results showed that the average TSS value in October was higher than in December. TSS in Lamteng waters shows a value that exceeds the quality standard value based on the Ministry of Environment.
The impact of the science technology society (STS) approach on critical thinking ability and student learning outcomes
Authors: Mulyanti S , Halim A , Murniati  , Ilyas S , Syukri M , Mursal
Published: May 2021

The research objective was to determine the application of the science and technology society (STS) approach in improving critical thinking ability (CTA) and student learning outcomes (LO) at High School Darul Ihsan Aceh Besar. This study used a pre-experimental method with a One Group Pre-test Post-test design. The instrument used in this study was a measurement test of critical thinking ability and learning outcomes. The results of descriptive data analysis show that the application of the Science-Technology-Society approach can improve critical thinking ability and can improve student-learning outcomes in the topic of harmonic oscillation. Besides, it also shows that the post-test score reaches the average value of 88.3 and the average N-gain reaches 75 points that is included in the high criteria of gains. The results of study shows that the science and technology approach to society can improve critical thinking ability and better learning outcomes, especially in the topic of harmonic oscillation.
Relationship between the use of the internet as a learning resource and physics learning outcomes
Authors: Halim A , Soewarno  , Yani E , Elisa  , Mahzum E , Farhan A , Irwandi I
Published: May 2021

The purpose of this study was to determine the relationship between the use of the internet as a learning resource and physics learning outcomes. This research is a quantitative study using the correlation method. The population in this study were all 105 students of class XI IPA Public High School 6 Banda Aceh, while a sample of 31 students was selected using random sampling techniques. Due to survey research, the data collection instruments used questionnaires and documentation. Data processing was performed using the Product Moment correlation test and the hypothesis was tested using the t-test. Based on the results of the calculation of data analysis, the value of the correlation coefficient r = 0.2646 (low correlation) and the tested hypothesis with a significant level α = 0.05 and degrees of freedom = 31-2 = 29 is 1.699, obtained t-count < t-table is 0, 4762 < 1, 699. Therefore, it can be concluded that there is no significant correlation between the use of the internet as a learning resource and the physics learning outcomes of class XI students of State Senior High School 6 Banda Aceh.
The lasso binary logistic regression method for selecting variables that affect the recovery of Covid-19 patients in China
Authors: Rusyana A , Notodiputro K A , Sartono B
Published: May 2021

The Lasso regression performs the least squares method with the l
1-constraint. This is a particular type of regularization which adds a penalty equal to the absolute value of the magnitude of coefficients that can result in sparse models with few coefficients in which some coefficients can become zero and be eliminated. Larger penalties result in coefficient values closer to zero, which is ideal for producing simpler models. In this study, the lasso method has been applied to select variables affecting the recovery of the Covid-19 patients. The data consisted of the number of patients treated in several hospitals or clinics in China, recovered patients, demographics, comorbidities, symptoms, and treatment. The performance of the lasso binary logistic regression was compared with the full model of logistic and the stepwise logistic regression. The results showed that the number of independent variables selected by the lasso method was larger than those selected by the stepwise method. It has also been showed that coefficient values of variables produced by the lasso method were smaller than those produced by the stepwise. The independent variables that affect the cure rate of covid-19 patients with the lasso are gender, comorbidities, diabetes, cardiovascular, cough, fatigue, diarrhea, platelet count and antibiotics.
SEIR model simulation on the spreading of Ebola virus between two regions
Authors: Rohmah A M , Rahmalia D
Published: May 2021

In this study, we formed one of epidemic models that describe the spread of Ebola virus disease between two regions in the mathematical model known as SEIR epidemic model. For constructing the mathematical model, it is necessary to understand the phenomenon of the spread of the Ebola virus such as that the number of infected populations in one region does not only depend on the number of infected individuals in one region but also by individuals traveling from one region to another. Based on this phenomenon, we constructed the SEIR mathematical model to determine the dynamics of the spreading virus. We computed the Basic Reproduction Number to determine the stability of the spreading virus. We applied the numerical simulation using the Runge-Kutta Order 4 method to illustrate the results obtained. The simulation results show that region B has a higher spread than region A, because the number virus transmission in region B is higher than that in region A based on the Basic Reproduction Numbers.
The effect of demographic variables on mathematics teachers’ TPACK: Indonesian context
Authors: Mailizar M , Hidayat M , Artika W
Published: May 2021

In Indonesia, teachers are required to integrate digital technology in the secondary school mathematics classroom. Therefore, it is necessary to examine mathematics teachers’ technological, pedagogical and content knowledge (TPACK) according to their demographic background. The purpose of this study was to examine Indonesian mathematics teachers TPACK and investigate if TPACK levels are significantly different in terms of gender, teaching experience, the level of schools and teacher level of education. We conducted a quantitative study with a crosssectional survey design. Data were collected from 210 mathematics teachers and analyzed by ANOVA. This study suggests that there were significant differences in teachers’ level of TPACK according to their gender and the level of education. However, it was found that there was no significant difference in teacher level of TPACK according to their teaching experience and the level of schools. To a large extent, this study suggested that teacher demographic background determine their TPACK.
The effectiveness of STEM mentor-mentee programme: Recreational Mathematics among secondary school students
Authors: Hassan K B , Kamaruddin H H , Khalid R Md. , Azman H H , Kasim C M M
Published: May 2021

In effort to engage secondary school students’ awareness towards Science, Technology, Engineering and Mathematics (STEM), the Recreational Mathematics programme is designed. The main objective of this programme is to promote secondary school students’ interest towards Mathematics subject. The participants were grade 5 students from Sekolah Menengah Kebangsaan Sungai Burong, Kuala Selangor, Malaysia. This programme contained 7 Mathematics activities involved basic concept of algebra. For each activity, they were guided by Universiti Selangor’s facilitators and mentors. The effectiveness of Recreational Mathematics programme was assessed through these activities. Data on a total of 91 students was collected and it was found that 75% students agreed on the success of the programme management. More than half of the students were interested with the method guided by the facilitators and mentors. They enjoyed studying this subject through mathematical games and activities. Nevertheless, there is a challenge to be encountered while conducting this programme. It was found that 96% of the students were not aware on the importance of STEM and more specifically the significance of mathematical subject. These findings show that STEM activities should be continuously run especially to the students in the rural area.
The exploration of ethnomathematics based on Rapa’i Geleng dance as mathematics learning media
Authors: Musawwir A , Suryadi D , Kusnandi
Published: May 2021

Several abstract topics in mathematics are considered unrelated to contextual problems. This condition occurs because students cannot use some abstract mathematics topics which obtained at school in their daily activities. Hence, students are less interested in mathematics learning. Therefore, a bridge connecting formal school mathematics and the local culture is needed; one of them is ethnomathematics research method design. Ethnomathematics is a qualitative method design which examines the practice and elements of mathematics in a cultural group. One of the cultures which grows, develops, and is popular in Banda Aceh City is the Rapa’i Geleng dance. Rapa’i Geleng is a traditional Acehnese dance performed by shaking the head to the left and right regularly in a specific pattern following the rhythmic strains of the Acehnese traditional musical instrument called Rapa’i. The data were collected through document review, including videos, photos, notes, and interviews with experts. The results of the exploration show that there is a mathematical concept in the Rapa’i Geleng dance, namely number pattern. The sequence topic was observed from dancers’ regular movement based on their position. Consequently, this dance is supposed to be used as a learning medium to explain abstract mathematical concepts to the students.
Development of student worksheets assisted by GeoGebra application in improving higher-order thinking ability in mathematics learning
Authors: Ahmad H , Syamsuddin  , Febryanti  , Latif A
Published: May 2021

This research was motivated by the low thinking level of SMK Mega Link Majene students in solving higher-order thinking problems and inadequate math teachers using mathematics applications in the learning process. This study aims to develop student worksheets assisted by the GeoGebra application to develop higher-order thinking skills. This research is Research and Development (RnD) using the ADDIE model (Analyze, Design, Development, Implementation, and Evaluation). The participants were 27 eleventh-grade students of SMK Mega Link Majene. The instruments were tests, student activity observation sheets, teacher implementation sheets, and questionnaires. The student worksheets should meet the characteristic of helping students develop higher-order thinking skills–analyzing, evaluating, and creating. The results showed that the student worksheets were in the valid category. The worksheets also fulfilled the practicality category: the learning implementation was well-executed, and met the effectiveness categories: (1) the students’ high-level thinking ability in mathematics on average was in the high category; (2) student activity was in the very active category; and (3) student responses to the student worksheets assisted by the GeoGebra application obtained a very positive response. The findings implied that the development of student worksheets assisted by the GeoGebra application met the valid, practical, and effective criteria.